Trevor Acorn - The Future of Construction w/ Structural Mastery from a Structural Engineer

Austin Tunnell

All right, well, welcome to the Building Culture podcast. I'm Austin Tanel and I'm super excited today because I've got on Trevor Acorn, who is a structural engineer. And from my understanding of principle, Walter P. Moore, which is, you know, like a global engineering firm. Um, and I first ran across you, I think on Twitter when I was in Spain, like four or five months ago or something you commented and I looked up.

Trevor Acorn

Right.

Austin Tunnell

And you just had a very fascinating take on things. I've never talked to a structural engineer who is talking like you. So before we get into that, if you could just do a little intro, talk about, you know, your background, what you're doing now, stuff like that.

Trevor Acorn

Yeah, no problem. Well, yeah, like you said, I'm a structural engineer. I work for Walter P. Moore. Walter P. Moore, it's really, it's a global engineering firm and we primarily do structural engineering. And we do a lot of pretty large and well-known projects all over the United States and even the rest of the world. But we also do enclosure engineering. We do diagnostics on old buildings. And so my particular role is structural engineering. I'm a... senior project manager here at Walter P. Moore. But I've got friends just down the hall that specialize in restoration of old masonry or glass facade restoration. We have guys that specialize in civil engineering. I mean, we have a lot of groups all in one firm. And honestly, it's pretty great to have so many experts under one roof that I can tap into and ask questions. Yeah, so that's me. I've been practicing for 18 years, in buildings. There's a lot of structural engineers that do bridges and other specialty, but I'm an engineer of record for many, many projects. Primarily work in the big material, steel, concrete, masonry. And yeah, I do projects all over the US. I've been in Kansas City for about 10 years here and it's great. I love what I do.

Austin Tunnell

Where are you from? Where were you before that?

Trevor Acorn

Well, so my folks lived outside of Rolla. So I grew up kind of in rural, Missouri Went to school in Rolla. There's an engineering school there. That's fairly well-known It's been a couple years in st. Louis, but then came over to Kansas City It's a lot of a lot of a lot of engineering here in Kansas City It's a good place to be if you're a you're an engineer

Austin Tunnell

Got it.

Austin Tunnell

Cool. We'll get into like defining some of the things we're talking about later. Like what is structural masonry and all that. But I'm actually just curious like how, because most structural engineers that I interact with, right, and they could walk all over me in terms of engineering, right? Like I don't know how to engineer things and calculate numbers and all that. But I've been consistently surprised at people's non-understanding or at least misunderstanding or whatever you want to call it about masonry, structural masonry. And just like knowing anything at all, like most people don't know anything about structural masonry. How did you, you know, familiar, you know, how did you get familiar with that, with structural masonry? Like have you worked on it? Is it because there was people doing restorations? Do you have an interest in it? You know, where does that come from?

Trevor Acorn

Yeah, I came at it from the latter too. So 12 years ago, I bought an old house and it had structural masonry walls, right? And I had to have one wall rebuilt completely because the mortar had been repointed with like a type S mortar. Over time that had cracked, water had infiltrated the wall, it had washed out the lime mortar that was behind the face mortar. All that mortar then kind of ran back behind the wall.

Austin Tunnell

Uh huh.

Trevor Acorn

and filled up the cavity. It's kind of an interesting thing here about Kansas City. We have all these short-waist homes and there were some of the earliest cavity wall construction. So it was like six-inch stone, but they do have like a two-inch air gap back there, but it was all lime mortar. They used these large nails to tie the stonework to the wall. It's really unique. It wasn't done for very long. But anyway, like that whole...

Austin Tunnell

And what kind of wall was it you said? Cause it's six inches of stone, but what is the quote unquote wall?

Trevor Acorn

right, six to eight inches. Yeah, it's almost a precursor to modern cavity wall construction. It was done in the 20s, actually earlier than that, my house is 1905, but they would do a rubble stone foundation, right? And then they would set a wood floor on top of it. And then that last kind of wife of stone, they would take up a whole story. And so that would be tied back to the stud wall cavity.

Austin Tunnell

Hmm

Austin Tunnell

And you're saying when you're it is a stud wall. It's like two by four You know old to ogre two by four. Is it siding like one by twelve slanted or something like that for your like sheathing? Okay

Trevor Acorn

So it's structural masonry below.

Trevor Acorn

Yeah, right, right. Yeah, it was one by sheeting. So it's structural masonry, the kind you're familiar with, the kind you're working with, below grade, right? It's a rubble stone foundation. But then once you get above that, it turns into a cavity wall system. And it was a very early version of a cavity wall system. But yeah, working on this old house and then understanding why the wall was failing, it led me down this rabbit hole of...

Austin Tunnell

Got it.

Austin Tunnell

Got it, okay.

Trevor Acorn

understanding the different types of mortar, different types of construction, our particular type of construction here in Kansas City, and also just historic masonry restoration generally. We have experts, like I said, at Walter P. Moore that do that work, and so I've had a lot of conversations with them as well. So, over the past 12 years, I've just gotten really familiar with it, primarily through this side, the side of restoration, not new construction.

Austin Tunnell

Mm-hmm.

Trevor Acorn

You're like one of the only people doing that but on the on the restoration side, it's common It's common to have to understand it

Austin Tunnell

Right.

Austin Tunnell

No, I found that restoration people are actually the most, um, generally helpful people to talk to because they know things from experience that they have seen it's not because they heard something or it's an old wives tale or blah, blah. It's no, no. If you put type S mortar, tuck point type S mortar on top of lime, it will destroy your building. You know, like they can say things with confidence from real experience of things they've seen that have lasted a hundred something years, although I will say there's a little, it's interesting, actually, I want to take your temperature on this. So.

Trevor Acorn

Yeah, right.

Austin Tunnell

There've been a few restoration people that have pushed back on my claims that, um, well, I, I say this term a lot, like one that all the oldest buildings in the world are some form of structural masonry. And I say all, maybe I should say the vast majority of right. Cause whether it's the pyramids or the Pantheon or entire cities all over Europe or South America, or even in the middle East or something, it's, it's structural masonry. And, and some people have kind of. suggested that I was getting confused and saying I was making a logical mistake of calling it survivorship bias. But for me, I'm actually saying I think they're using that backwards because the restoration people that are saying this, they'll say, no, every masonry building we work on, you've got to retuck point the whole thing. It's hundreds of thousands of dollars, blah, blah. And I'm like, yeah, because it's still there 150 years later when it hasn't been maintained versus... stick frame left unmaintained would not be there in that time. Cause that's how I describe it as masonry. It's not like one is inherently like better. Everything's got pros and cons, but masonry has fewer vulnerabilities. Take out seismic and then, you know, it's not termite, mold, fire rot, you know, it's just less things vulnerabilities than Mason or than wood framed construction. Would you kind of agree with that? Would you argue? Would you add on to what I'm saying here?

Trevor Acorn

Sure, I mean, boy, any building that's poorly built and not detailed well is not going to last, right? And even a structural masonry wall, if your roof is improperly designed and it doesn't shed water properly, if that masonry is constantly exposed to moisture and freeze thaw, I think it's going to have a limited life. It's going to last a lot longer than wood. I agree with you there. But every building needs to have good... detailing to last. And I think that's an important point. One thing I've seen a lot, just looking at all these old buildings. So I live in a historic neighborhood of Kansas City. I'm surrounded by masonry buildings. And a lot of that masonry done with lime mortar over a hundred years ago is due for repointing. It only needs to be repointed once every 30, 40, 50 years. It lasts a really, really long time. But it's important to do that right. incorrectly, then those buildings fail prematurely. I think there's also something to be said to you about modern mortars. I'm not a huge fan of high cement mortars, but a well-designed, well-engineered masonry building today, like the ones you guys are doing, even with exposure to water, again, the last even longer than some of the historic ones that are being built. So I think doing it right makes a big difference.

Austin Tunnell

Mm-hmm.

Austin Tunnell

No, I like what you say there that it needs to be detailed right. Because I've seen old brick buildings that are in terrible shape, you know, as you're saying. And the thing that I would say is it kind of like you're saying is that it can just go a much longer period without being maintained and still be able to be brought back to life with serious maintenance and stuff and fixing it up. But what I'm thinking about, like part of our argument is if you're trying to build for centuries.

Trevor Acorn

Mm-hmm.

Austin Tunnell

Obviously you want to detail it all well, regardless of what you're building. But you also don't want to assume that there's going to be like perfect maintenance all the time over a 400 or 500 year lifespan, you know, economies. And when you talk, talk about that kind of time span, you're talking about like six cities, you know, becoming very wealthy and then kind of falling into poverty for a hundred years and then back, you know, like it's a long and so.

Trevor Acorn

Exactly right, yeah.

Austin Tunnell

I think that's part of the strength of masonry is its ability to withstand years of neglect when built correctly. And it's not indefinite, you know, it will disintegrate at some point, you know, the mortar and all that.

Trevor Acorn

Yeah, I think, you know, I certainly talk a lot with people about designing a building well from a structural perspective, from a durability perspective. But I think something that you're onto, and I think the rest of the AEC industry, which was onto more, is designing buildings that we love, right? Because if we build a beautiful building, it's going to want to be maintained by the people that own and live in that building, right? People don't want to see beautiful buildings go into disrepair.

Austin Tunnell

Yeah.

Trevor Acorn

And I think that that's also an important factor. I think the design is really important, aesthetically, the details are important. I mean, all this stuff is really important, right? My goal in life is for all of us to build better buildings, buildings that last, buildings that we can give to our kids.

Austin Tunnell

No, that's I love it. Yeah. And I actually want to come back to talking more about that because that's really unique. Well, I think it's a neat perspective and it's really unique. And like engineers, like I've just never talked and like on your bio, you're like talking about Christopher Alexander and stuff. Like how did you get, how did you, you know, Donald Shoop and stuff? Like, how are you, um, you

Trevor Acorn

Yeah, sure, yeah. Yeah, I could talk about that a bit. I mean, so my engineering, my education was in architectural engineering and you know there's a lot in that program of course, but I did two semesters of a history of architecture class. I had a really great professor, Jeff, there and during that class I got introduced to Christopher Alexander. And just architectural theory in general. And I really fell in love with it. It just really hit on a lot of levels for me. And so I went down a pretty deep rabbit hole in the whole new urbanism and these, the Christopher Alexander kind of way of thinking and looking at the world. That... That led me into a lot of other things, including thinking about like urban economics, right? And Henry George and Don Shoup and these other things that impact our built environment, right? To me, it's not just our buildings. It's the whole soup, right? It's how everything comes together that really matters.

Austin Tunnell

Yeah.

Austin Tunnell

Right. Gosh, we need like that is if there was one thing I could change about the industry. I mean, I'm kind of saying this offhand. So maybe if I thought hard enough, I think of something else, but like, if there was one thing that I could change about the industry, just with a snap of my fingers, it would be to just have everyone be more well-rounded and understand what other people are doing. So engineers understand architecture and architecture and engineers and GCs and trades and, and utility engineers and municipalities, like they actually.

Trevor Acorn

Right.

Trevor Acorn

Yeah

Trevor Acorn

100%.

Austin Tunnell

have an understanding and appreciation. Doesn't mean they're experts, right? Like, yeah.

Trevor Acorn

Yeah, totally. One of the best things I did was working for my dad in construction during college. He was a builder. He had a concrete company and I would help him pour concrete. I did flat work and elevated work. Yeah, it really made me appreciate what gets done in the field and I keep thinking back on that. You know, another thing too after...

Austin Tunnell

Oh.

Austin Tunnell

That's cool.

Trevor Acorn

After I graduated, I went to work in St. Louis for this development called the New Town at St. Charles, which is a new urban development, one of the larger ones in the United States. It was designed by Duane Plater Zeebeck, so Andre Stoani was a part of that. I got to work with Tim Bussey, the town architect, and it was really cool. I mean, I lived there, I was part of that whole group. But also, as we're designing and building all these buildings, I'm kind of the in-house structural engineer for them. The guys that are actually building all the buildings on site are coming just walking in the door, because our office was right there on site. They'd walk in the door, and they'd share their comments. And they'd look at me, and they'd be like, Trevor, I need you to design this differently for this reason, right? I wanted to put this together like this, but the way you designed it doesn't allow me to do that. And so I got constant feedback from these guys in the field. that allowed me to be a better designer. And yeah, it's something I've always, when I design a new building and I go out on site visits, I'm always asking the contractor, hey, what could I have done different? Like, what was a pain point for you? What slowed you down? Those kind of questions, right? It really matters that the people building the building aren't frustrated as they build it, right? And that they can deliver at a really high level.

Austin Tunnell

Wow, that is so cool.

Austin Tunnell

Yeah. And yeah, very cool. I could keep talking about this for 20 minutes. Fine. I'm going to kind of move on because I want to get through some of the more get into some of the technical stuff. And part of it, I actually want to talk about the industry more for my own understanding. Um, and like, if you were described to describe to a sixth grader, right? So as if I'm an idiot, uh, well, sixth graders aren't idiots, but you know what I mean, I described to me, like, I don't know what I'm talking about. What does it mean to engineer something?

Trevor Acorn

I think that's important.

Austin Tunnell

Like, what are you doing? Does that question make sense? Okay.

Trevor Acorn

Yeah, sure. Yeah. Well, I think a lot of people know what it means to design something, right? And maybe we should start there because engineering is really the next step. It comes behind the designer and it helps the designer accomplish his design, right? So I work primarily for architects. I'm a consultant to an architect. They come up with a beautiful design for a building and somehow they need to get that thing built in the real world. Right. And so they come to me and I design the structure. So I'm designing the columns, the beams, maybe the stud framing, the foundations, all the things that are required to make that building actually stand up and work. Right. In the real world for wind, for seismic, for gravity lifts. So that's the particular kind of engineering that I'm doing. I'm supporting an architect who's doing designing design work, and I'm doing the engineering behind it.

Austin Tunnell

And then, you know, and to go a layer deeper, cause then when you say I'm designing the beams, I'm designing the structure once again, like, what do you mean by I'm designing? Cause like, I, you know, I know what it means, like you're running calculations of load and all that and PSI and compression and, and sheer and all that, but there's, you know, and not, and this is where I start to really not know what I'm talking about. It's there's even different ways that you can choose as a structural engineer to analyze something, right? There's not just one way to engineer a beam. Aren't there?

Trevor Acorn

Yeah.

Austin Tunnell

you know, multiple ways to analyze something. Am I right about that? And like, if they've got names or is it just like one approach to everything.

Trevor Acorn

Sure. Yeah, it kind of is material specific. And we also, you know, we have building codes, like we have the International Building Code, International Residential Code, that provides guidance and rules and limits on to, you know, what, where you go with your design. So there's a lot of guidance out there and there are different ways to do it, for sure. There's different approaches to doing the math, to doing the analysis, and to picking the beams. They're all pretty similar, right? So in my world, a more technical term, like we have ASD, which is an allowable stress design method. Yeah, and so we'll use that. That's very common in masonry, for example. It's really common in wood construction. But in concrete and steel, especially concrete, we have LRFD, which is, let's see, load resistance factor design. So it's more of a statistical approach.

Austin Tunnell

That's okay, yeah.

Trevor Acorn

that takes the loading but then applies it in a little different way than the allowable stress design. Two different approaches. They actually, I mean, honestly, they result in very similar kind of answers. But that's just, I would say that's just on the strength side of things. As a structural engineer, I'm also thinking about the stiffness of things. That's like deflection, right? And how they perform. So like deflection but also vibration is a concern. I'm also concerned about size.

Austin Tunnell

Got it.

Trevor Acorn

seismic forces, wind forces, and of course how all these parts and pieces of a building come together. So there are nuances to all that and different structural engineers have different levels of experience in those areas. For example, not every structural engineer spends a lot of time doing vibration design and there's a lot of nuance to vibration design or to high seismic design, and it takes experience to do that well. So like, you know, one thing that I'm doing with my architects is I'm trying to bring the best practices of design, of structural design and engineering to the table. And that may not just be through me, right, but through my team or through my coworkers in California or New York or wherever they are, we bring the top designers to the table on some of these buildings that we work on. I hope that helps.

Austin Tunnell

Got it. Okay. Yeah, no, it is. And that's what I was looking for. It's like the AST allow, uh, what is it? Allowable stress test, allowable stress design. Okay. Um, and then load resistant something. Yeah. Got it. Okay. And you know, in terms of, and you might not know all this. If you were to ask me the history of my profession, I couldn't tell you certain things, but, um, you know, when we say, when I say, or when, you know, we say modern engineering.

Trevor Acorn

allowable stress design. Yeah.

Trevor Acorn

Yeah, load resistance factor design.

Austin Tunnell

What does it actually mean to you? Like, is there a date where it's like, now we are crossed into modern engineering? Here is pre-modern, here is post-modern engineering, or just modern engineering, I should say.

Trevor Acorn

Yeah, I'm not an expert in the history there, but I do know that a lot of these methods of analysis and engineering started to Come about in the early 1900s, you know the 20th century late 1900s early 1900s and We just started using you know applying using physics science to the built environment So before that a lot of things were built on an empirical method, right, based on experience. A lot of the masonry buildings all around the world, they were built on essentially rules of thumb, right, of best practices kind of learned over time. And modern engineering just applies the foundations of physics, structural analysis, you know, statistics to buildings so that we can kind of tune that and think about it a little more logically, right.

Austin Tunnell

Right.

Austin Tunnell

Got it, yeah.

Trevor Acorn

We can calculate the forces that go through a beam, and we can figure out exactly how many bolts it's going to take to hold that beam up.

Austin Tunnell

No, kind of a random offhand question. Do modern engineers believe in the idea of thrust that an arch or something lets off thrust? Cause someone told me they don't.

Trevor Acorn

That's an interesting question. I don't know if I feel like I should ask about whoever told you that. But yeah, of course. It's you know, thrust, we don't run into it as much, right? Because we're not building arches anymore so much. It's much more rare. But anytime you really do have an arch, then you obviously you have thrust.

Austin Tunnell

Ha ha! Okay.

Austin Tunnell

Right.

Trevor Acorn

The most common place that we run into thrust is actually in an attic roof of a house. If you think about any attic roof, you got two rafters that they're coming together. At the base of those rafters is thrust. Without something to resist that thrust at the bottom of the rafters, those rafters will spread. Normally, we resist that with the ceiling joist. Or if you have a prefabricated truss, that's what a truss is. It's got a bottom cord that resists that thrust from the Raptors. So yeah, I mean thrust is very real

Austin Tunnell

Got it. And can you calculate specifically like what is the thrust coming off of an arch? You know, say, Hey, it's 20 foot wide arch. You got X amount of weight above it. Can you, and how do you do that in modern engineering? Cause I've not met many people you're the, and we'll get into graphic static. There's so many things I want to ask you, gosh. Okay. So I'm just trying to not throw too much at you at once. Um, can you calculate without graphics as let's not into graphic statics yet, but just in kind of like modern engineering.

Trevor Acorn

Sure. Yeah.

Trevor Acorn

Um.

Austin Tunnell

Do most structural engineers, could they look at an arch and be like, yeah, you need about five feet of buttress on this side of the arch to make sure the forces.

Trevor Acorn

No, I don't think anybody could do that, honestly, anymore. It's so uncommon. Yeah, like I said, thrust is a very real thing. Yeah, but that is, oh my goodness. OK, we have specialty engineers that do very large structures, like tensile fabric structures and large compression arch kind of structures,

Austin Tunnell

Okay.

Austin Tunnell

So they know it exists, they just don't know how to.

Trevor Acorn

they have specialty software that is used to calculate that. And to find, you know, a big part of these kind of structures is not just calculating it, but then finding the right form. We call it form finding, right? Because you have to draw out your arch in the correct shape for it to be in pure compression. And if you do that incorrectly, then you can get bending moments inside your arch that cause it. So it's really important to get the shape of an arch correct. So yeah, we call that form finding. We use graphic statics, Rhino and Grasshopper, a lot of tools to do that.

Austin Tunnell

Y'all use graphic status because like most, so that is that pretty, is that you that knows graphic status or like, Hey, most of the people you work with know it too.

Trevor Acorn

Very few people I work with know it. Yeah, it's incredibly uncommon. Yeah.

Austin Tunnell

Okay, I was going to say, because I haven't talked to anyone, you were the first person that were like, oh yeah, graphics tech. So I was like, wow, I got to talk to you. And I see the, I see the book behind you. I've, oh, you, I don't know if you can see mine. I've actually got it sitting right there. Cause when I was in Spain and I was like, I could tell everything they were so much of what they were talking about was over my head because I'm not an engineer, you know? And I was like, hold on, what is the baby version of this? So I can like teach myself some stuff. And they're like, oh, that form enforces, that'll teach you everything. I like got.

Trevor Acorn

Yeah, yeah, it's.

Trevor Acorn

Oh.

Trevor Acorn

Mm-hmm.

Austin Tunnell

book and it's just huge and complex. I was like, Whoa, okay, I'm not going to figure this out overnight. But

Trevor Acorn

Oh, that's the book. Yeah, that's an incredible book. Yeah. Right. Definitely one of my favorite books. Yeah, no, so, you know, okay, graphic statics would be used to find the shape of a truss, or, well, it could be used for trusses, but for an arch, it would be used to find the shape of an arch. Or if you have an arch shape and you have some uniform applied loads to it, you could use it to calculate if that arch is acceptable or not. Right, yeah, to calculate the buttress force, or the thrust force for the buttress.

Austin Tunnell

Or to calculate how much butt you're seeing you need, you know, based on. Yeah.

Trevor Acorn

that can fall out of a graphic statics approach. Unfortunately though, like when you get into different load combinations and, you know, wind pressures that maybe hit the arch in different ways, or if you have like a point load on part of the arch, it gets really complicated really quickly. And so that's where we use computer methods to define those forces and to check an arch under all the different load combinations and conditions that might apply in the real world.

Austin Tunnell

Got it. Is, is struck, is, is graphic statics. Is that like, um, is it on the lines of say, a type of analysis that modern engineering can do like ASD, you know, or, or LRFD, or is it kind of completely separate and is it like official? You know what I mean? Like, or is it just, Hey, this is a good way to think about things. Or is it, Hey, if you can prove it in graphic statics, you can pass code and do it.

Trevor Acorn

Yes.

Trevor Acorn

Okay, yeah. I don't know of anyone using GraphicStatics as part of a calculation package that they then send to the building official for permit. You know, it gets at the right answer. But again, you have to prove to a building official that whatever structure you're designing is going to work for all the different conditions. And when we talk about building a commercial building with all the different loads. we might have a thousand different load combinations that get applied to any given beam or element in the structure. And it would be incredibly difficult to use graphic statics to do that. We would use graphic statics upfront to find the shape, and to do the big picture analysis. And then we would use a more robust computer software to fine tune that and to do the final calculations that would be submitted to the building official.

Austin Tunnell

Interesting.

Trevor Acorn

In the end, it's not really ASD or LRFD. What it is a way to, for any given load, define what the resultant forces are. It's a trick, right?

Austin Tunnell

Hmm. Got it. Is it accurate? And this is kind of like when I was hearing it from, I'm from non-engineers. I was hearing it from engineers and I'm a non-engineer and the way I've kind of been describing it since I kind of heard about it is graphic statics is a way to. Um, design a very efficient, uh, designed something very efficiently by considering the shape and the geometry and the flow of forces through a building or material and kind of like tailoring it to that. So you're, you're kind of getting rid of excess waste and excess materials and things like that, or allows you to do stuff like that. Is that kind of, that is right. Like I'm not wrong when I say that. Hey.

Trevor Acorn

Yeah, that's absolutely right. Yeah, no, that's absolutely right. So I mentioned earlier, we use it for form finding, right? Yeah, it's really a tool for that upfront, finding the shape that's gonna give us that expressive structure that we want, and that we're pretty confident that later when we do a more robust analysis, it's gonna still work, right?

Austin Tunnell

That's what I thought it was cool, because when you said it, I was like, okay, maybe I'm not wrong when I say that.

Austin Tunnell

Is that the Eiffel Tower? You might not know this, but I think the Eiffel Tower and stuff was based on graphic statics and do you know? Okay.

Trevor Acorn

Yeah, I think it was actually. I don't know much of the history there, but a lot of older buildings were, bridges especially were very commonly done that way.

Austin Tunnell

Man, there's this gosh, I got to it.

Austin Tunnell

I was about to say bridges. There was a new bridge, uh, gosh, somewhere in Europe. I mean, this, I mean, I wish I remembered the name of it. It really bothers me that I forgot it because I want to look it up, but it, it's just this just thin, thin bridge. It just has this little taper at the end across this huge gorgeous built in the past 10 years and they did it off graphic statics and it's just, or at least this is what I was told, um, and it's incredible. Uh,

Trevor Acorn

Sure, yeah, it's awesome.

Austin Tunnell

And of course, then you've got all the guastavino stuff from a hundred years ago that I'm getting really intrigued with, um, of, of learning how to do that. And this gets into the shape of the arch and things like that, because I actually want to follow up with that because I, you know, assuming you've got enough buttressing, okay. Assuming you've got a solid foundation with minimal movement and enough buttressings, your thrust, you know, isn't, you know, going outside the wall or something like that. You've resolved that in my mind, you could basically build an arch in any shape and it's not going to fail.

Trevor Acorn

Yeah, you've resolved your thrust into the right.

Trevor Acorn

Well, as your arch, okay, so you have the spring line, you have the crown, the rise of the arch, then you kind of have the top and bottom lines, right, which are the interdos and extrados, I think is what they call those. So we try to keep the flow of forces in the center third of the interdos and extrados, yeah. So as you adjust the shape of the arch,

Austin Tunnell

Mm-hmm. Yep.

Austin Tunnell

Okay, that's what you're talking about.

Trevor Acorn

you have to do that in a way where that flow of forces stays within the center third of the arch. So that's why a flat arch, I mean when you go completely flat, those forces no longer resolve.

Austin Tunnell

Got it. Okay.

Austin Tunnell

ride a Jack arch or something or so what's interesting about that is, um, and I don't know this, I'm asking to, like, I'm both telling you what I think and asking you if this is correct, but that matters a lot when you're building, say in the, an old cathedral, you know, you've got these vaulted ceilings and then the roof is actually wood, you know, generally speaking, like the ceiling is a thin, you know, vault or something. And then the roof is typically some kind of wood. Um, and, uh, Oh my goodness, where was I going with that? Uh,

Trevor Acorn

Right, yeah.

Austin Tunnell

Oh, yeah, yeah. I mean, you've got basically a kind of a freestanding arch where you just have the vussoirs of the arch and nothing else and then you could get a point load. And what you're saying there about the forces flowing within the center third of that arch makes sense to me. But when you put the arch within a wall, like it's within a brick wall, and there's masonry above it and all around it, then that doesn't like, then it really doesn't matter. In

Trevor Acorn

Oh, sure. Yeah.

Austin Tunnell

My mind the way I actually think about it in terms of how it works in real life that arch is not going to fail You can do a really shallow segmental arch. You can do a pointed arch. You can do a half round arch

Trevor Acorn

Yeah, I see what you're saying. It's interesting, if you just took a solid brick wall and you just punch a hole in it, forget about the arch, just hit it, yeah, put a hole through it, but eventually that little bit of brick above the hole will start to arch around it. And that is the flow of forces that I'm talking about, because below that, you're getting tension in the brick or the masonry, and that's what's causing it to fall out of the arch. So that's that flow of forces.

Austin Tunnell

It'll stand up.

Austin Tunnell

Right.

Austin Tunnell

Right.

Austin Tunnell

Yep.

Austin Tunnell

Okay. And this validates kind of what I was thinking. Well, so some nuances that I learned in Spain, by the way, when I was there with Spain, I mean, these are guys that are, you know, in their sixties and stuff that have been basically studying old masonry buildings their whole lives. And they get called in to the old cathedral because there's a crack and hey, is it going to stand up? Do we need to do anything? Do we need to put tension ties? Do we leave it? Do we need to tear it down? You know, so they've been studying these things for their lives. But. I had always in my head before this trip referred to certain arches as stronger than other arches. And let's see, what did I say? You know, because you can say certain arches have less thrust. You know, a Roman arch, which is, you know, a half round arch is going to have less thrust than a shallow segmental arch, you know. And then that kind of makes sense intuitively. You look at it and you're like, okay, I can kind of like just understand, even if you don't fully understand the why, like it kind of makes sense.

Trevor Acorn

Yeah, right.

Austin Tunnell

But what they were talking, you know, and I knew about catenary arches before I went, you know, but if you hang a chain upside down, you know, that's gonna be, and you can actually move it in and out, you know, if you imagine moving your hands in and out and the shape of the arch changes, well, that's a catenary. You flip that upside down and, you know, it's perfectly in tension because you're hanging it as a chain. You flip it upside down, perfectly in compression, and you can also thin that out and have different shapes. And this was what was fascinating to me is because I'd always thought about half round arches being

Trevor Acorn

Yeah, it goes in perfect compression. That's right.

Austin Tunnell

quote unquote, stronger than segmental. Something about it makes sense when you look at it a little bit where you can kind of make that argument because it's like a half round arch or something, something about it. You could see the way I used to understand masonry that it's quote unquote stronger. But the way I've learned to say it now is it's actually not stronger. Well, actually a half round arch is less efficient than a segmental arch because the further you depart from a true catenary, the more meat you have. to have within the arch to keep the flow of forces within the center third. So a half round arch is very unlike a chain versus a, well, not unlike, but you'll actually have the chain kind of fall out very easily. It's hard to keep it in the center third versus a segmental arch. You can actually, there's actually more ways you can hang that chain within the segmental or a Gothic arch, which is actually the closest to a catenary, is actually the most efficient arch, meaning you can make it the thinnest arch, which doesn't really matter in a wall system, right? If you're in an entire brick wall,

Trevor Acorn

Yeah, I think that's a correct way to think about it.

Austin Tunnell

Whether it's two Rolex or Vauxsoirs or 10, it really doesn't matter. Um, but if you were doing it free standing, you know, point loads and things like that, and you want the flow of forces to stay within the arts. That's where I know it's just interesting to think about, oh, there's more about the flow of forces and efficiencies. It's not that one arch is so really stronger than the other. And ultimately, if you can keep the masonry from moving one, you've got enough butt, you're saying all that. And you can keep the masonry from moving. any arch can stand there because you actually have to have movement in a building for an arch to crack or for something to happen. Or at least that's how I'm thinking about it now.

Trevor Acorn

sure. I think you're on the right track. Absolutely. You know, when I was talking about form finding and the arch shapes, and often what we're looking at is, you know, how can we adjust the shape of the structure and keep everything in compression, right? And so if you think about like a Gothic arch, right, it's not a circle or a parabola or a cantonary curve. It's got like a little point at the top.

Austin Tunnell

Okay.

Trevor Acorn

So that's an example of an arch that actually has some different curvature along the arch You can imagine an arch where maybe you want it to kind of dip down and then go horizontal Right, you don't see arches like that very often. I can't think of anything like but if you were You would find that flow of forces gets out of the center third if that if that dip in the arch is too great And that would create an arch that they would have they would go into tension and would have some issues with it

Austin Tunnell

Right.

Austin Tunnell

Yeah, it's interesting. It's so interesting for me that the, the under it's starting to understand. It's so weird. Masonry is interesting because, um, if you just imagine a brick wall, you're looking at just a plain brick wall. And then you have, I don't know, just call it a, a five foot wide opening in it. And an arch over call it a segmental arch. You, and then there's 20 feet of masonry above it. You, you, like in your head, you kind of imagine all that weight and forces coming down, it hits the arch and then it diverts sideways.

Trevor Acorn

So, yeah.

Austin Tunnell

But it's not like the f- Exactly, yeah, yeah. So, so, so actually you, you kind of explain that cause I'm gonna, I'm curious if I'm, yeah, go ahead with that, what you mean by that.

Trevor Acorn

It's spreading before that, yeah. Yeah, yeah, yeah.

Trevor Acorn

Well, now, it's a common kind of misunderstanding. I mean, I understand where it comes from. Even a lot of structural engineers think about it that way. In our minds, we kind of chase the forces down and we follow the forces through the building. But as like an aside example, I often work with concrete walls, right? And they're supported by, often by footings, but sometimes there's no footing at all underneath the concrete wall. Sometimes we'll span a wall from a deep foundation, a pier to a pier. And in that case, it's very clear. The forces aren't coming straight down the wall and directly into the dirt. The wall is acting like a beam, right? And it's distributing that load out to the piers. Similarly, in a masonry wall, well before that load hits the arch in a big solid wall, it's spread out. And that interlocking of all the brick and just the stiffness of the wall causes that load to spread. So you're right. I mean, yeah.

Austin Tunnell

Hmm.

Austin Tunnell

Yep.

Austin Tunnell

Yeah. What's interesting about that is what that means is your arch isn't really carrying nearly as much weight. You know, say you've got a hundred foot feet, you've got a 10 foot wide arch and a hundred feet of masonry above. That arch is not carrying a hundred feet of weight above it. You know, like you're saying kind of is that triangle, or at least my understanding is if it's a 10 foot of wide arch, you make a, what do you call an equilateral triangle and that's really ultimately about the weight that arch is carrying because the other weight is already starting to move to the sides of it before it ever gets there in catenary fashion.

Trevor Acorn

Yeah, that's exactly right. If you're going to design a steel lentil, which is, you know, we could talk about that. But if you're going to design a steel lentil above a window, we really only have to look at that triangle of brick that's above it, that equal lateral, you know, 45 degree from the ends of the angle. And that weight of that is all that hits that lentil. So lentils are often very overdesigned for the load that they actually see. Yeah.

Austin Tunnell

Right. I believe that I did it once myself, just I was so nervous about, uh, well, and of course engineers, but I mean, like, I didn't know, I didn't fully understand, and so I even did a relief arch above it because I was like, so scared about using metal and, oh, you know, just, uh, it's kind of funny, but.

Trevor Acorn

Yeah

Trevor Acorn

Well, maybe we could talk about brick veneer for a minute, but brick veneer throws a wrench in all this. Because with brick veneer, you've got to have control joints. And often the control joints are at the windows. And so now it's like, well, you don't have any way to resist the thrust. So is it going to arch over the lintel? Probably not. And so now you've got to over-design all your lintels for this wall of brick that has nowhere else to go. Right.

Austin Tunnell

Yeah.

Austin Tunnell

Right?

Austin Tunnell

Right. See, that's really interesting. Uh, that's another kind of nuance there about what not per se veneer, but something I learned or realized is say you do put in a solid stone and I think most engineers would, you know, want to throw up if I told them this, but like putting in a solid unreinforced lintel stone, lintel, you know, terrifying, right? Uh, I'm just kidding. Um, but.

Trevor Acorn

Sure.

Austin Tunnell

It actually, I mean, I think, you know, it, that functions as a beam when you put it in, as in weight comes in, there's no thrust off that because the weight's coming, you know, straight down because you've got a beam, you know, just like you would with metal coming straight down, like you're saying. But this was interesting. And this was what I was talking to one of these, some of these experts about is, yeah, but what happens if that lintel cracks just a little bit? Well, the building's not going to fall down.

Trevor Acorn

Yeah, right.

Austin Tunnell

Unless like there's substantial movement in the walls falling away. You know, there's really no way for masonry to fail if you can keep the walls from moving in some ways. Well, structurally water and stuff can, can damage something, but the moment the lintel cracks, it's no longer acting as a beam, it's actually acting as an arch. Like there's it's arching within that stone that might be two pieces together. And there's one side kind of slipped down and a little crack in between it.

Trevor Acorn

Yeah, right.

Austin Tunnell

You know, it's no longer acting as a meme. It's actually acting as an arch, you know, and then it's just, you know, you can't have any, it doesn't, it's not going to slide. So it actually holds itself up. Um, but what's interesting about that is I used to think, Oh, I can put a lintel closer to a wall and need less, less buttressing than a segmental arch or something, which is true, but if that stone were to crack and suddenly that thing starts arching and you can't control that, it was just a, it kind of like a, oh, like, Oh, that's interesting. Like I hadn't thought about that. Um,

Trevor Acorn

Yeah, I think what's happening...

Trevor Acorn

Oh, I see.

Trevor Acorn

Yeah, I gotcha. Yeah, I think you're right. I mean, when the lintel cracks, right? The brick above it tries to move down with it. And as soon as that happens, it starts to arch again. Now, if the question is like the lintel itself, if it has no steel inside of it and it cracks, there's nothing resisting the tension on the bottom side of that lintel. So it would fail.

Austin Tunnell

Yeah.

Trevor Acorn

but for the masonry above not coming down with it. Right.

Austin Tunnell

Exactly. Because that's what I mean. If, if the, if you keep your walls from moving that lintel, even if it cracks and starts to fall, it can't actually fall because the masonry over here is holding it in place and then it can't slide past each other, can't move out. The outside can't move up. And so that's what I see. Cracked lintels all the time. It's funny because we misunderstand masonry so much in the United States. We look at cracks and it's like, oh my gosh, the masonry is failing. We actually put this in our contracts, but it's like masonry cracks, all masonry cracks over time because.

Trevor Acorn

Oh, right.

Trevor Acorn

Right. That's awesome.

Austin Tunnell

Any tension introduced into it. The only way for masonry to relieve tension is to crack. And then it goes back into equilibrium. Well, hopefully. So I say 99.9% of cracks are non-structural. Would you agree with that or disagree? I mean, I'm saying arbitrarily saying 99% like maybe of well-built buildings.

Trevor Acorn

Yeah, there's a lot of masonry is kind of like concrete in this respect. Concrete always cracks and masonry will crack. If you're using the right mortars and things, sometimes those cracks can kind of heal themselves a bit. But when there's building movement, we'll see diagonal cracks and that's a structural concern. That's usually a sign of settlement, big diagonal cracks.

Austin Tunnell

Right.

Austin Tunnell

Right.

Trevor Acorn

But often like a vertical crack is usually just a sign of shrinkage.

Austin Tunnell

Yeah. I actually had one of my first big arches crack. Um, and it scared the crap out of me. Um, and I had, uh, Wallace engineering. Do you know Wallace engineering and this? Yeah. Okay. So, and, and at the time, I mean, it's a while ago, Tom Wallace, like the, the guy that started it, like, he was just curious because I was like, that's pretty cool. And I had him come assess it and he was like, Oh,

Trevor Acorn

Oh, sure. Yeah, they have a Kansas City office.

Austin Tunnell

You're totally fine. Don't do anything. I was like, Oh, awesome. And then, but it was funny because I, that's where I started really understanding masonry better because I kept just, I just lay a bed at night. Like, why did it crack? You know, like you're just sitting there thinking about the, this wall and how it works and things. And, and all it was is just like one side of the arch settled a little bit. Um, and this is interesting because it's allowed by engineering. And, but what we did is we had, imagine a rectangle of a house. So just a simple rectangle of a house.

Trevor Acorn

Great.

Austin Tunnell

And then cut that rectangle in half with what I would call kind of like a, you see it in a lot of our houses, if you're on Instagram or something, just like we call it a buttressing wall on the inside where it's just a big arch on the inside. Basically just cuts the rectangle in half and then also cuts the floor plane in half a little bit and you get this big brick arch inside, very pretty. And a lot of these arches, we do this in a lot of our houses, they're 10 to 12 feet wide. Well, even engineered, right? Like the foundation, well, we didn't carry the footing underneath that 12 foot of arch because why are you going to waste all that concrete? So it's just like we did footing, footing for where the spring, you know, where the arch started, you know, where it went to, and then there was nothing in between. Well, then what happens is one side can differentially settle compared to the other side. And so now we never do that. We always, and like this funny, because once again, you can have an engineer and they might not do that, but now we just carry that, even if it's a 20 foot wide arch, we'll carry that footing all the way across and connect it with, with rebar to make sure in grand that you could still get differential settling, but it makes it way, way harder. and we have not had any cracks in.

Trevor Acorn

Yeah. The way I think about that as a structural engineer, I try to size my footings for equal stress, right? So I try to chase all the loads down the building. And then when those loads hit the ground, I adjust the size of the footing so that I'm applying the same amount of stress to the subsoil everywhere I go. So in your case, like the arch, right? One way to deal with that is exactly like you said, you could just run the footing all the way through, reinforce it, and that distributes that load over that larger area. The other way to do it would be like at the ends of the arch, you could have spread footings that are wider, larger, and then sized so that the soil stress is the same as the rest of the wall. So in plan, you would see maybe your typical footing is, I don't know, two and a half foot wide, but then at the arch, maybe have like a five by five foot footing, something like that.

Austin Tunnell

Got it, okay.

Austin Tunnell

Got it. Okay. That's very interesting. Well, I wanted to say one more thing on the, uh, cause it was, it helped me understand it, uh, for anyone that might be listening, you know, once again, kind of going back to that arch, this idea of the arch carrying all the weight or not carrying all the weight. And you might be thinking like, how is it not carrying all the weight? Well, or, or this idea of like, yeah, the weight comes down, hits the arch and then, and then it, you know, goes sideways around, you know, to the sides. But if you just imagine a, I don't know, call it a 10 foot high garden wall, just to call it a double width brick wall, two brick thick wall, 10 feet tall, and you've just got all the brick laid just normally how you would see on a building. Okay, yeah, you can make the sense. All that force is going straight to the ground. Everything's going vertically right down to the ground. And then now change the brick and turn it up on end in what we would call a soldier course. Do the same thing. The forces flow through it the exact same way. Turn them on a diagonal, the forces flow through it exactly the same way. build a bunch of arches into the brick wall, but it's all a solid brick wall, there's no actual openings, those forces still just flow straight down. Because it's not like going, oh, I hit this brick that's turned a different direction, now I'm gonna go sideways, right? Like it's still, in that sense, it's a monolithic wall to the forces. Or at least once again, I'm kind of saying this because this is how I'm understanding it now, and curious if you would agree with that.

Trevor Acorn

Yeah, so well, often with masonry, we're trying to have a mortar and a masonry unit that has similar strength. The mortar usually a little less than the masonry unit. And when they bond together, those two elements now have similar strength and similar stiffness. So the thing with structural engineering and with load path is that the load will always follow the path of highest stiffness. So if you put something. very stiff in a wall, it attracts load, right? And so, you know, a clay masonry unit has the same stiffness no matter which way you push and pull on it. So it doesn't really matter in a wall application how you orient that brick as far as how the forces flow through the wall. You're right about that. You know, kind of what does end up mattering is, you know, when you have, the bricks will tie into each other. And so like, if you punch a hole in a wall, they'll interlock and that interlocking of the bricks can create kind of an arching action. And so that's a little different than what you're getting at anyway, but I agree with your fundamental insight there that yeah, forces flow regardless.

Austin Tunnell

Right.

Austin Tunnell

Yep. Okay. That was mind that was, you know, cause I already, when I figured that out, like I under, I already, just cause I've been doing this while, like I understand masonry differently than most people, you know, I have very hands on understanding. Uh, but that one was still like a, Oh my gosh. Like it was, uh, it was a complete, it kind of, kind of blew my mind in the moment of how I was missing something so big, but really kind of exciting too, to understand understanding masonry differently. Um, well, because when you actually really understand something, you know, you can start manipulating and playing and inventing and things more so. Um, huh. Would most engineers understand? I mean, I'm sure if you told them, but like, would they know that if you just, what we just talked about?

Trevor Acorn

I think they might. I mean, we often think of masonry pretty monolithically as far as the stress when we're analyzing the stresses in the masonry wall. So that's not that uncommon. We have these things we call allowable stresses, right? So we'll calculate for a given masonry unit and a given mortar what the allowable stress is in that wall. And it doesn't really matter the orientation of the masonry units. We're always checking the same stress everywhere in that wall.

Austin Tunnell

Uh, are you familiar with Hyman? Um, Hyman, the he's, uh, what is it? Jack Weiss Hyman. He's still alive today. He's very old. Yes. Engineer and, um, graphic statics. And he's written like the stone skeleton. He's kind of like the structural masonry master. Um, but he's very technical. So like, it's really hard to understand just as a lay person. Like I have, I have trouble understanding, but he, H E Y M A N. I've got a couple of his.

Trevor Acorn

Is he an engineer or is he, what does he do?

Trevor Acorn

How do you spell his name? I'm going to do a quick Google.

Austin Tunnell

books. Um, yeah, cause he actually, this really interesting, this was, it was repeated in Spain over and over again is Hyman Hyman. Like you've got to understand him. If you want to understand masonry and he has three rules about masonry when you're designing, he says one, assume that it has infinite compression. Obviously it doesn't like it can technically fail, but just in terms of practicality, you're never going to fail in compression with masonry because you can build it so hot, you know, without failing and you're talking about skyscrapers fine, you know, maybe at some point you have to worry about it, but for the most part, infinite compression to no tension. So he's just, even though technically masonry has the ability to have some tension, he just says like, assume there's zero tension and then three assume no sliding when you're designing, you know, sliding between things. And obviously that can happen. And by the way, sliding could be hugely detrimental, but when you're trying to figure out if a building like how to design a building, those are his kind of like three tenants of. uh, structural masonry. Um, and, and he's someone I still want to learn more and read more. Uh, but he talks about all this kind of stuff that we're talking about too. Um, and flying buttresses and things.

Trevor Acorn

I love that you brought it up. Yeah, I've seen this book before and I don't own it and I'm not familiar with his work. So I'm gonna check it out. That's really cool.

Austin Tunnell

Cool. I, yeah, I'll be curious if you ever do get into that, I would love to talk to you about it because that's one where I'm just, I think you would understand so much more than me reading it. You know, we, we've mentioned a couple of times and I think this is a pretty practical one, I'm curious your take on mortar, I'm guessing we're fairly come from a similar place on it, just from what I heard you say, but, but what is your kind of take on Mortars and what are the in your opinion? What are the best mortars?

Trevor Acorn

Yeah, I mean, there's a lot of confusion on this topic, and it's probably good to try to bring some clarity to the issue. So, in the United States, we have, how most people, most engineers think about it is, the word Mason, right? So M-S-O-N, different types of mortars. And M is like the strongest of the strong mortars. it's high cement content. And then as you go S, it's structural. It's also high strength. And it's lower strength. O is even lower. There's also a K, which is very low. I think it's masonry work. Yeah. Yeah, let's see. M-A-S-O-N-W-O-R-K. Yeah, right. Yeah, so K.

Austin Tunnell

I hadn't even heard of the K, that's interesting, I thought O was the softest.

Austin Tunnell

Like, it's every other letter. Yeah, I always forget too. I just remember MSNO.

Trevor Acorn

Yeah, K is on the lowest end. But every one of those is cement-based mortar. I mean, that's just what we do in America. That's Portland cement, right? So they have different amounts, right? So type N is one part cement, one part lime, type S lime, hydrated lime, which I'm gonna talk about in a second, and then sand. And type S, or that's type N, type S has half as much lime. And type O,

Austin Tunnell

Right. Cement being Portland.

Trevor Acorn

has that much less again of lime, like quarter.

Austin Tunnell

Yeah, we, we actually make that I'm curious. We make that it's, it's kind of like our best of not the best, like the best cost-effective thing to do for anyone out there to like, rather than buying a type S or a type N that's premixed from the store, we'll mix a type O on site that is one, one part Portland, two parts type S lime. And technically they say it's nine parts sand in the book, but I'm skeptical of that and think it's more like eight, but, um,

Trevor Acorn

Oh great.

Trevor Acorn

Yeah, eight to nine, yeah. Yeah, technically I think you can adjust that and still be type O, yeah.

Austin Tunnell

Right. And that's something like 350 PSI, which I understand sounds really low to people because like concrete's 3,500, you know, but, but in the context of the building and the way it's distributed, you're, you know, when you're building a few story buildings, you're not worried about 350 PSI actually pencils out from my understanding.

Trevor Acorn

Yeah, I like to just, if I know the masonry unit that I'm working with, I want to make sure that whatever mortar I use is less than that masonry unit. You don't want to have a higher strength mortar than masonry unit. It can lead to a lot of different issues. But that's just, okay, that's just cement-based mortars. In historic preservation...

Austin Tunnell

Right.

Trevor Acorn

we have lime-based mortars that are in all these old buildings, and you don't want to be mixing cement-based mortars and lime-based mortars unless if you're super careful about having a mortar that is very similar stiffness to the other mortar in there. Otherwise, the load that's coming down the wall, I already said load will chase the path of high stiffness, right? So now if you put, if you mix a high-strength, high-stiff mortar and with an existing old lime mortar, that load is going to shift over and try to force its way through that little bit of tuck pointing that you did.

Austin Tunnell

Fascinating. I've never, that's new for me. Okay.

Trevor Acorn

Yeah, so we want those to match. The other thing that happens is a high cement mortar, like a type S mortar, will hold water behind it. And so we can actually trap water. And then you can get freeze thaw damage in that masonry, right, from water. It's also the more Portland cement you use, the more likely that mortar is to crack. And the less able it is to heal itself, too. The lime in that mortar will help kind of fuse back together the microcracks that happen in that. And so that cracking also allows a path for water into the joint, right, which can then saturate and leach out the lime mortar that's behind it. So there's a lot of things to think about when you're using different mortars. But you know, in Europe, they're still using lime-based mortars without any cement, and those are different. You know, when you go to Home Depot and you buy lime, type S lime, that is a...

Austin Tunnell

Right.

Austin Tunnell

Yeah.

Trevor Acorn

hydrated lime. If you mix that lime with sand, it's never going to set up. It looks like mortar, it never sets up. That's very different than hydraulic lime. There's non-hydraulic, there's natural hydraulic lime, lime putty, it's also called. All these have a natural pozzolin or like fly ash slag, brick dust in them that will allow them to set up. and act as a mortar. So those kind of mortars are great for soft masonry and they're very common in Europe. But they're pretty hard to attain here. I don't know if you've had luck trying to source them.

Austin Tunnell

Hmm. It's about 50 bucks a, but you can get it pretty easily, but it's $50 a bag. And just to compare that, you can go to the store and buy a type N for 12 bucks a bag. So it's. Boy.

Trevor Acorn

Yeah, exactly. Right. So I often recommend that people use type N or type O and let's take a look at the masonry units that you're using and try to think through that. But the one issue with wine mortars from Europe or even a type O mortar is really just kind of freeze thaw and durability over time in an exterior environment. The mortar fails, which is exactly what you want, but it's just going to fail a little sooner.

Austin Tunnell

Okay.

Austin Tunnell

Right.

Trevor Acorn

then maybe a type N might in an exterior wall application. So type N can still be good from a longer-term durability of the wall. Or I should say, not really durability, but you're going to have to repoint the wall more often if you're using a software.

Austin Tunnell

Right. That's what's interesting.

Austin Tunnell

Right. But yeah, it's hard, but it's like, you got to repoint it more often, but it might, if it is maintained may actually last longer in the long run, which is interesting, but I mean, I totally like the type S or type N, you know, on repointing on an old historic building. My gosh. I mean, I see that all over Oakland city. He was walking by and you see this brick spalling, you know, I mean, it happens very quickly. I didn't know about the following the path of the stiffness, which is really fascinating. I hadn't realized that makes sense to me, but yeah, the water one and the freeze thaw.

Trevor Acorn

If that's right. Yeah.

Trevor Acorn

Yeah, especially yeah.

Austin Tunnell

But on that note, it's interesting because old brick, these bricks that are 100 years old or more, a lot of those are 2000 PSI, maybe 3000 PSI versus modern brick. The brick we're using are over 6000 PSI. Even just straight up Portland concrete that you'd be pulling a driveway with that's 3500 PSI, their brick is still way harder than...

Trevor Acorn

of, yeah.

Austin Tunnell

the Portland. So what's your opinion of that? And this is where I really don't know. And I'm not sure anyone really knows everyone's got opinions, but like, uh, because we, we haven't really tested it, but some people will say, well, it's stronger. So it's better more dirt, you know, because it's modern brick, it doesn't matter as much. And now the Portland is actually better because we've got harder brick and that way. Yeah. You don't have to tuck point as much like with the lime mortar, et cetera, et cetera. What do you think about? Yeah. What's kind of your take on that harder brick? Does that make Portland okay better? You know, is lime still preferable?

Trevor Acorn

Sure, yeah. I think the harder brick, I think they're on the market more now because in a cavity wall situation, those bricks are exposed to much higher degrees of freeze-thaw and a porous brick in that application, imagine a brick full of water and then freezes, right? It's going to bust apart more easily. and a highly porous brick is going to allow more water into it. So the higher strength bricks also tend to be less porous. And also they're less susceptible to freeze thaw damage. So I think that's why in the market you're seeing higher strength bricks are more common. It does mean also that they're more agreeable to cement mortars as a result, because they have a higher strength. So I think that's okay. I think you can use type N and type S in the cavity wall and be fine. And in a mass wall like what you're doing, you wanna have that vapor, the water, to be able to come in and come out of that wall. And you want it to be able to dry in both ways. And so more porous bricks and more porous mortars work well in a big mass wall as a result. Austin Tunnell (01:00:07.062) Yep. Trevor Acorn (01:00:17.236) So I think that seems more appropriate there. But yeah, I think a lot of the higher strength brick, like I said, and mortars are really a function of how we're using them today, which is cavity wall construction primarily. Austin Tunnell (01:00:17.41) Yep. Austin Tunnell (01:00:27.518) Right. And it seems like it would still be good in structural masonry, just that once again, the more water you keep out without sealing something off so that when water gets in, it doesn't, you know, it keeps liquid water out, but it allows water vapor, water gas in and out. You know, it seems like harder brick, even for structural masonry would be a very good idea and that's where I kind of go, I just wonder like, okay, if you've got a harder brick that lets in less water. Trevor Acorn (01:00:36.894) Yeah. Trevor Acorn (01:00:42.304) Yeah, that's right. Austin Tunnell (01:00:53.61) Might it be better to have a harder mortar that lets in less water too? But I don't know, and I'll tell you kind of like just how we think about it and what we do. If we do use a pre-blended mortar and budget's kind of the main thing here is we'll use a type N, from the store type N. So it's the softest you can buy from the store because you can't even find type O. So that's kind of our, that's our lowest tier, but we feel good about it still with modern brick. We would not do that with a reclaimed brick to be clear. Trevor Acorn (01:00:57.101) Thanks for watching! Right. Austin Tunnell (01:01:22.806) The second version we'll do that's a little bit more expensive, but still doable is we'll buy type one, two Portland type S lime and the sand. So it's the type O mortar where it's one part Portland, two parts type of this lime, then you know, eight or nine parts sand. And I think that's pretty solid because at least it's got twice as much lime as Portland, you know, um, and then the third kind, which was a more recent discovery in the past two years, because these NHLs, the natural hydraulic lines out of Europe. Trevor Acorn (01:01:36.161) down. Trevor Acorn (01:01:48.267) Right. Austin Tunnell (01:01:48.306) are 50, 60 bucks a bag and then heck, I don't even know those bags are as big. So, I mean, it's just outrageously expensive unless you're going to be just tuck pointing a few things right on the historic building that's worth it. But, Greymont out of their plant and I think Ohio has a PHL, a pozzolanic hydraulic lime that's they've got a 3.5 and a 5.0 and they're using medicaolin for their pozzolan. So it's no Portland, no cement and it's just real lime and medicaolin, which is supposed to be a very good pozzolan. It gives the hydraulic set. Trevor Acorn (01:02:12.694) Right. Austin Tunnell (01:02:18.238) And so that's what we've used on a couple of our buildings. And when we're using reclaimed brick, we'll either do that or the, the type O blend, if we're using a reclaimed brick, but that PHL is really interesting. Do you have an experience with, um, cause the problem is, is I like it. I like the idea of it. I've talked to a few people that really think it's, um, awesome, but like so few people know about masonry in this country that it's, you know, Trevor Acorn (01:02:40.312) Mm-hmm. All right. Yeah, I get it. So the question is about pozzolin-based lime mortars. I don't know much about them. I know we've been doing this in concrete for a long time, where we've been trading off cement for flash, slag, metakaolin, silica fumes, another one. And yeah, it's in concrete. Yeah. It's not concrete. Austin Tunnell (01:02:51.807) Okay. Austin Tunnell (01:03:04.342) Oh, so y'all use medicail in concrete stuff. Got it, okay. Trevor Acorn (01:03:09.596) I think, yeah, it's similar to like brick dust is also a pozzolin, right? Yeah, and it's a clay-based product. It's complicated. I don't know a lot of the nuances of it, but I kind of think about it as similar to like what a brick dust pozzolin is. Austin Tunnell (01:03:10.414) It's a clay product, right? Or some kind of medication? Austin Tunnell (01:03:16.462) Okay. Right, I remember the Romans, I think, did that for their lime. Austin Tunnell (01:03:33.278) Okay. Got it. And I don't know. You might not know if this is true or not, but my current understanding is, uh, what gives lime a hydraulic set is the amount of impurities in it. And I'm going to miss the, whatever the molecules like, cause whatever it is, calcium carbon, whatever I forget the, what is that? Okay. Yeah. And what I've heard, okay. Yeah. I don't know that this is true. So if you ever hear anything, keep an ear out, but like, what I've heard is that in Europe, they have, well, their lime is less pure. Trevor Acorn (01:03:47.712) You probably know more about that than I do. Yeah. I don't know about, yeah. Yeah. I know that it's a thing, but I'm not familiar with it. Austin Tunnell (01:04:02.73) So like they have a bunch of NHL and the U S our lime is actually a lot more pure or at least what we're mining. So we actually have to add. Posilons to it, to give it a hydraulic set, which is just interesting. And you know, that's kind of anecdotal. I heard that from like one or two people years ago, but it made sense to me. Trevor Acorn (01:04:05.472) Gotcha, yeah. Trevor Acorn (01:04:14.841) Oh, gotcha. It is curious to me why... Trevor Acorn (01:04:20.584) Okay, gotcha. Yeah, I'm not familiar with that, but it has been curious to me why it's so hard for us to get the same limewater that they're using in Europe. Like, what's the deal? What's the deal, US? Yeah. Austin Tunnell (01:04:30.258) Yeah. Well, and so this is, this is actually one other interesting thing. And I mean, we're, we're at an hour. So I'll kind of want to wrap in the next 10 minutes and we're just going to have to do another one. Cause I I've gotten through like a quarter of my stuff, but, um, Oh shoot, where was I going? Where was it going? Oh, oh, you were asking about, so why don't we have lime and, and this is Trevor Acorn (01:04:46.732) Uh... Austin Tunnell (01:04:54.654) I've talked to old masons in the US. They'll come on one of our job sites and maybe their 50s or 60s probably, and they'll be kind of blown away what we're doing. And they'll say, man, I remember, and maybe they're a little older, 60s, 70s or something. And they'll say, man, I remember we used to do this. We'd show up on a job site, there's a foundation there and a footing, and we'd start laying brick. And I always ask people, what happened? would change. And a lot of people, like more than just a few, have indicated they think steel lobbying and concrete lobbying played a huge role, if not the main role. And I've actually heard from other people, and these are trustworthy people, but I'm kind of being cautious because I don't know these as facts, you know, but that even the Portland industry bought up most of our lime and stuff like that, and they're just not mining it. And so there's all sorts of little conspiracy things around. steel in Portland, which is kind of funny, but I'm also open to it because so much of it is weird. Like you're just going, what happened? Like one day we're doing all these things. And then the next day, boom, done. Like Guastavino did over a thousand buildings across 32 states in the United States a hundred years ago. Most of those are still standing today that aren't torn down. They're shockingly amazing. The St. John's dome that he did a hundred years ago in New York, it's 130 foot diameter. He's using five inches of thin clay tile and zero steel are reinforcing. The Duomo in Florence is 146 foot diameter. It took him 15 years to build. He does some 15 weeks without centering or formwork and it's still standing. And they chose him to do that because it was the cheapest option to do it. And now like you would be looked at like you're an insane person. If you were to even just ask to do something like that. Trevor Acorn (01:06:30.304) Yeah, it's incredible. Trevor Acorn (01:06:42.36) Thanks for watching! Austin Tunnell (01:06:50.73) Sorry, that was kind of a... Trevor Acorn (01:06:51.392) I'm not sure. No, I love it. I'm not sure what to say. I, you know, I'll say this for a very, very long time. Concrete in America was incredibly cheap, right? It's incredibly cheap. It's still fairly cheap. But when, um, with that building material that is so powerful in so many ways for construction, I mean, it's pretty honestly concrete and steel together. It's, it's crazy what- we've done with that material. And it's been so cheap for so long that I think economics was a big part of it. Maybe there was a conspiracy too. I will say, I also do a lot of work with mass timber. We should talk about timber sometime. I think that would be cool. But the cement industry, the concrete industry, they put all kinds of marketing about how mass timber buildings were unsafe. And they were incredibly scared about it and did everything in their power to try to limit. Austin Tunnell (01:07:30.786) Boo yah. Austin Tunnell (01:07:45.623) Right. Trevor Acorn (01:07:48.508) designers from designing around it. Austin Tunnell (01:07:50.498) Right. And see, that's what I wonder about steel too, because it's like steel is an absolutely incredible material. We have done a make the modern world is, I mean, just mind bogging, just amazing. Right. We can launch rockets into space. I look at skyscrapers and I'm just like, Mike, like, how are we able to do stuff like this? And then I pass a 12 foot garden wall in Oklahoma city that's built by the government and fairly new and it's falling apart because they put a bunch of steel in it. And it's like a freaking Trevor Acorn (01:08:17.98) Oh yeah. It's right. Austin Tunnell (01:08:19.49) garden wall and then I'll post about it and say, guys, I'm not an engineer. I don't put steel in the buildings because by the way, when steel rusts, it expands four times its original size. It blows out the masonry, failing infrastructure in America. It's not failing concrete, it's failing rebar. And then a little have engineers message back angrily arguing with me about how it was the right thing to put that steel in that wall. I'm going, I don't even know how to, it just doesn't make sense to me. Trevor Acorn (01:08:32.194) 100%. Yeah. Trevor Acorn (01:08:42.036) Yeah, you're right about that and they're all wrong. So as soon as you put, yeah, man, okay. As soon as you put steel and concrete or masonry, you're limiting the life of that structure if it's exposed to moisture. Now, like in an interior environment, you got a concrete building, concrete columns, inside a roof, under a roof and behind walls. Yeah, that's gonna last forever as long as it's, you know, stays dry. But yeah. Austin Tunnell (01:08:45.858) That actually really helps me to hear because I'm always worried I'm wrong. Trevor Acorn (01:09:10.856) in an exterior application, eventually over time that cement, that concrete is going to carbonate, the pH level in that concrete is going to change, it's going to drop, and then that steel will start to rust and expand. I think it's more than four times, maybe it's four times, but yeah, it'll, yeah. Yeah, so you'll see rust tracking and you know, yeah, it'll blow apart your concrete and your masonry. Austin Tunnell (01:09:27.818) I've heard seven too, but I've heard four to seven. Trevor Acorn (01:09:37.16) So yeah, I think as structural engineers especially, we should be really careful when we specify steel, any steel in an exposed environment like that. You know, we're limiting the life of that structure by doing that for sure. Austin Tunnell (01:09:50.038) got it. And I have a question there because this is what I wonder, because I definitely know about it in exterior walls, right? Although I found this out recently, I don't know if it's... Well, they were saying that... Hold on. These were engineers. These were actually when it was in Spain, but they were saying that steel... If you actually just leave it in water, it will last a lot longer than if you're putting it in water, drying it out, putting it in water, drying it out. So that's true. Okay. Trevor Acorn (01:10:17.645) Yeah, the chemical reaction requires water and air, oxygen. And so take one of those away and you're not gonna get the rest. Austin Tunnell (01:10:21.374) Okay. Austin Tunnell (01:10:26.218) What is the technical term for like some steel resting? It's carbonizing. What, what is it doing? What's the, okay. Good. We'll just leave it at that. Um, but here's my other question because you mentioned this was actually something I really wanted to ask you is yeah, when you do use steel correctly, right in the right application, it is an amazing material, um, and say you've got concrete, uh, columns in a building or something. Trevor Acorn (01:10:31.888) I just call it resting. I forget the technical term. Yeah, yeah, great. Trevor Acorn (01:10:45.216) Right. Austin Tunnell (01:10:53.358) I always kind of was thinking like besides humidity and stuff like that, like, man, it seems like those could last a pretty dang long time. But these people I've met recently said, yes, it will last a lot longer than an exterior wall. But ultimately, they said the exact same thing you just said about the concrete, its pH level changing and what is it carbonizing because it's absorbing carbon? Okay, so it's carbonizing and then that steel is still going to rest because of that carbonization around. Is that true? Trevor Acorn (01:11:09.368) Carbonates, yeah. Yeah, right, carbonizes, yeah. Trevor Acorn (01:11:20.4) Yeah, yeah, that's true. So slowly over time, there's a, I forget what chemical you put, but you can cut a piece of concrete open and you can apply this chemical to it and it'll turn the concrete pink. And over time, the pink represents the depth of the carbonation of that concrete. And so that goes deeper and deeper and deeper over time. Austin Tunnell (01:11:45.399) Mmm. Trevor Acorn (01:11:49.24) Part of what we do in concrete design is we set the rebar back from the face of concrete by a dimension. In exterior concrete, it's an inch and a half, two inches, even three inches. We do that because of that, because of that carbonation, also because of cracks and water infiltration that can bring water in touch with that rebar. Inside of a building, we're set back an inch and a half, two inches on our columns. And it's going to take an incredibly long time for that carbonation layer to reach that steel, because it's harder for it to go deeper and deeper, right? It happens kind of quicker at the surface, and then it slows down as it goes deeper into it. Right. Yeah. Austin Tunnell (01:12:24.93) Got it. Cause it actually has to absorb the car. Right. Which is why a hydraulic set and mortar is so important. So you can keep building your wall quickly. Cause if it's carbonation, it can't cure in the middle of the wall. Because if it's a thick wall, okay. That's kind of the same. Am I using, am I comparing that correctly? Is this okay? Trevor Acorn (01:12:36.096) Right Trevor Acorn (01:12:39.612) Yeah, right. Yeah. Yeah, that's right. Hydraulic is water set. With mortars, there's also non-hydraulic mortars that set through exposure to the air, which is interesting, I think, through carbonation. But yeah. Austin Tunnell (01:12:53.398) Right. Carbonation. Right. Like the type S line. Trevor Acorn (01:13:00.032) Yeah, well, right. Type S line mixed with the POS, type S line like from Home Depot mixed with the POS line. Yeah, that'll set. Austin Tunnell (01:13:07.578) Oh, you still have to mix it with the puzzle. Like even I thought lime with sand was actually you can cure it. It'll just be type it would be through carbonation because we've just kind of like painted it on stuff before. And it does dry out and harden up, but it's not like hard, you know. Trevor Acorn (01:13:21.468) Yeah, the type S is that you buy from Home Depot is special. It's a hydrated lime. It goes through this process where it won't ever set up by itself with water. It'll, it'll dry out and it might crust, but it won't actually set up in any sort of structural way that yeah. Austin Tunnell (01:13:26.434) Write special. Austin Tunnell (01:13:36.982) Oh, I see. Okay. I'm glad you that helped. It's been a while since I was thinking about that. Okay. And that's a couple more things because we're talking about steel. Well, three more things. Um, so a skyscraper, for example, that's steel structure, all that. Um, can those last like, I mean, 500, a thousand years. Trevor Acorn (01:13:44.406) Yeah. Trevor Acorn (01:13:50.581) Sure. Trevor Acorn (01:13:57.816) steel and concrete, yeah. Trevor Acorn (01:14:06.148) I mean, there's a lot in that question because any structure has to be maintained. And some structures can last longer with less maintenance than others. We've already talked about that. A big steel structure like I've also already said that it needs to be a building that's loved, right? Or else it's not going to be maintained. I think that's important. But it's going to be. Austin Tunnell (01:14:09.334) Ha ha. Austin Tunnell (01:14:29.895) Right. Yeah. Trevor Acorn (01:14:35.992) the facade, right? So it's gonna be the glass, you've got ceiling joints, all of that has to be replaced over time. It's gonna be the detailing of the roof at the parapet to the walls. It's gonna be all, you know, that whole envelope has to be cared for over the life of that structure if it's gonna have any chance of lasting a thousand years. But there's nothing inherently, there's nothing about the structure itself that I think would prohibit it from lasting an incredibly long time. Austin Tunnell (01:15:03.1) Okay. Trevor Acorn (01:15:05.416) Yeah, a thousand years, maybe. Yeah, it's real. Right. Austin Tunnell (01:15:05.483) Right. Right. That's a hard, that's a hard timeline. I mean, you have no idea what's yeah. No. Cool. Um, just add it to, we'll, we'll pick it up on the next time we talk, but. Excuse me. Are you familiar with GFRP rebar at all? Glass fiber reinforced polymer. Yep. Have you all used that? Trevor Acorn (01:15:23.196) Yeah, glass fiber reinforced. Yeah. We actually talked about it in our office here recently. It's an interesting material. You can't field bend it. So if you need hooks and things, it may not be the best choice. But for flat work, it could make a lot of sense. It doesn't have good fire resistance. I believe, I think it softens under a fire event. So in a building where you might need your concrete to have a one hour or two hour writing, I think there might be some issues with it there. But yeah, imagine for a slab on grade or a grade beam, or I can imagine an exterior environment where it might be exposed to the elements, it could make a lot of sense. Yeah. Austin Tunnell (01:15:54.079) Mm-hmm. Austin Tunnell (01:16:16.75) Cool. That's, and we'll talk about it more next time, but that's what we've been using for, I don't know, got six, five, six years now, uh, is GFRP rebar in our buildings. And it's interesting because when I, I feel like when we first started using it, it was like really under the radar. And then in just six years now, like there's a couple of local stores that are stocking it. Now it's, it's not the size we need. Um, but it's like seven sixteenths or something. So, you know, number fours and we generally use number sixes. Trevor Acorn (01:16:25.18) Oh, you've been using it? Oh, that's great, okay. Trevor Acorn (01:16:37.819) Oh wow. Austin Tunnell (01:16:45.198) Um, for our walls, like vertical reinforcements and bond beams. Um, but I will say totally right on the bending. Uh, but thankfully in our application, we like need straight ones. And then we just need corners. So we just order the corners like 30 inch bent corners. And it's actually really nice because then you don't have to bend it and working with a, what I love about it is it weighs 75% less so that you can take a number six, you know, at three quarters inch stick that's 20 feet long and I could carry a bundle on my shoulder. Trevor Acorn (01:16:58.304) Oh yeah. Trevor Acorn (01:17:06.803) Oh sure. Austin Tunnell (01:17:12.726) versus one piece of steel, I would carry it and it would be like, oh, and then trying to like maneuver it and get it around and you know, it's interesting. Trevor Acorn (01:17:17.32) Hey, yeah, that's really cool. So are you using it in like a foundation, like a concrete foundation or using it in your masonry walls? Austin Tunnell (01:17:27.062) We've done both and what we're trying to move to is only GFRP and foundation and walls, but we've just been doing it in walls mainly and then foundation when budget allows, although at this point it's about the same price of steel. So early is last time I checked. Trevor Acorn (01:17:40.544) Yeah, interesting. I have more questions now. I unfortunately have to go. I got to take kids on a soccer carpool here momentarily. Maybe we'll have to do it again. Sure. Austin Tunnell (01:17:47.873) Okay. Cool. Okay. Well, let me just show you this one thing because this, I want to get you nerded out so that you, we can get back on here and talk. Let me share my screen. I know anyone listening is not going to be able to see this, but I'll describe it. And, um, okay, let's see how I can do this. No. Okay. Here we are. Austin Tunnell (01:18:11.851) Okay. Well, while that is loading, Trevor, I'm showing you, there's this guy, Peter Block, Peter Block Research Group out of Zurich, and they're playing with graphic statics along with John Oxendorf and MIT. And this is a floor system that they are installing in high rise. And I think it's already in there. So it's multiple stories. This is a concrete floor system. That's five pieces. They're, they're cast pieces. Trevor Acorn (01:18:23.956) I saw this, yeah. Austin Tunnell (01:18:38.138) And they're just lowering them into place. And then that little, that middle piece gets put in last. The thin parts between the ribs is an inch thick. And on top of that, they're using lightweight concrete and there's zero steel or anything in here. The only steel would be exterior tie bars around it in some applications, or if you're building an envelope already has that, but basically that is entirely in compression and it reduces the amount of steel and concrete that they need for their floor systems by something like 80% or something like that. which I had never realized that floor systems and high rises and big commercial buildings were such a huge part of the cost materials, labor, and carbon even of a project. And so it was just these massive reductions. I just thought this was the coolest freaking thing I had seen in a long time. Um, have you, are you familiar with this? Trevor Acorn (01:19:12.817) Oh yeah, for sure carbon. Trevor Acorn (01:19:20.764) I love it. I am only familiar as of this week. I saw something about this and looked into it. I mean, it is really incredible. Like you said, like thrust, like back to that early conversation, this only works because of the thrust at the perimeter. So you have to design a whole, you know, your whole building. These all have to be very carefully laid out in a way where all that thrust can be resolved, right, through tie rods or through other structure. So but yeah. Austin Tunnell (01:19:45.118) Yeah, yep. Right. Trevor Acorn (01:19:50.356) I mean, it's super cool. Austin Tunnell (01:19:52.102) Right. Like I just, I keep going, the applications, I mean, they're doing other stuff. You know, this is, you know, this is in Texas, I think, and this just, you've seen that and it's just amazing because they're designing this with graphic statics. Now they're using grasshopper and other things. And I think some of them do more. I don't know enough to speak to that. You would know way more, but it's really impressive, you know, what you can do when you get the geometry and the proportions, right? The Trevor Acorn (01:19:57.48) Yeah, I've seen this, yeah. Yeah. Trevor Acorn (01:20:05.922) Mm-hmm. Austin Tunnell (01:20:17.646) Efficiency and durable strength of a structure that you can make like it's just it's shocking to me And it's just it's such a cool thing that I feel like is missing Completely missing in modern engineering like I don't know if that's true or not like do you think stuff like this has a you know? a real-world application today in the 21st century Trevor Acorn (01:20:40.215) Yeah, it's hard, right? Because there's so much. Trevor Acorn (01:20:46.124) There's so much momentum, inertia going in the direction that we've been going for the past 100 years. So it's really hard to change things. But as we get an individual project, one individual project after another individual project, where these things start to make sense again, especially this floor system that you had on the screen, I could see that having pretty wide ranging use in even a high rise building, right? It could reduce the weight. and can reduce the cost and even the speed of construction because those are all prefabricated. It's similar to kind of what I'm seeing with mass timber too. It's like as the bugs get worked out and we're figuring out how to use it better, like I think we're gonna see more and more buildings use that, those structures. But it takes, unfortunately, it just takes a lot of time for people to wrap their heads around it. You know, you got to test it. You got to prove that it's gonna work. Someone's got to actually go out and build it and Austin Tunnell (01:21:21.175) Yep. Austin Tunnell (01:21:37.42) Right. Right. Trevor Acorn (01:21:45.244) everybody's watching and You know Yeah, exactly. Yeah, but Austin Tunnell (01:21:46.662) Yeah. Yeah, let's get fail and you fail very loudly. It was doesn't help. That's kind of the exciting part of it all for us. It's like, how do you, you know, being the age that I, you know, pretty, I'm 35. And, you know, when you grow up in the world as it is, you kind of feel like the world's all figured out, you know, you can travel, go to Africa and take a picture on your Instagram and it's posted for the world, you know, you can fly, go into space, you know, just insane. And we were on the verge of AI, right. And. It just feels like there's nothing left to like truly pioneer. But like the older I get, the more I don't believe that the more I'm like, oh my gosh, there's so much more to do so much more to learn so much more to pioneer so much more invention and innovation that needs to be had. Like we had like the skyrocketing amount and I feel like there's almost a bit of a plateau and it's like, what is the next kind of push going to be? But anyway, I know you've got to go get your kids. Um, I could do this for four more hours, so really appreciate it. And I look forward to hopping on here again sometime if you're up for it. Trevor Acorn (01:22:34.089) Natural, yeah. Yeah. Trevor Acorn (01:22:44.18) Yeah, Austin had a blast. Happy to chat about other topics, structural engineering or otherwise. We have a lot of similar interests I see here too. So I think that's really. Austin Tunnell (01:22:52.194) Good job. Cool. Well, thanks. Thanks Trevor. And, uh, yeah, we'll talk to you again soon. Bye. Trevor Acorn (01:22:59.628) Great, thanks. Talk to you later.