EP #134: Concrete vs. Mass Timber – Sorting Fact from Hype

Seth Tandett (00:00)
And welcome to another episode of the concrete logic podcast. And today I have Garrett Braun of blue nest principle. Correct? Is that your, that your, your title that you use? He's a struck structural engineer and he was nice enough to come on the podcast today. We're going to talk about mass timber, which you know, in the intro to the podcast, if you guys listen to it,

Garrett Braun (00:10)
That's correct, that's the title I use. I've been given, yeah.

Yes.

Seth Tandett (00:29)
the guy that does the cool voice and everything. He actually says, we're going to bring on people of competing materials. look at that. We're doing that today. Holy cow.

Garrett Braun (00:39)
I also use lots of concrete, so I'm just specifying these things. But yeah, we can talk about what the pros and cons of mass timber and concrete and stuff when we're using one over the other.

Seth Tandett (00:44)
Right.

Yeah, no.

Yeah, that's perfect. So yeah, so Garrett, do you want to share a little bit more about yourself before we get started?

Garrett Braun (00:57)
Sure, So structural engineer, went to school at Georgia Tech, lived up in Boston, lived in Richmond, moved to Richmond about eight years ago. So we work on primarily buildings and then buildings of all types. I'd say half our work is existing buildings, half is new structures. And then we're using all the major materials, including mass timber and concrete. Yeah, so we've got a small little firm we started almost five years ago at this point. We got five folks working with us, yeah, based in Richmond.

Seth Tandett (01:22)
Yep. And you do work in just Virginia or you do work all over or where are you doing work?

Garrett Braun (01:29)
The vast majority of our work is in Virginia. We've got a random project in Kansas. We've done some stuff in Georgia, North Carolina, Maryland, Ohio. So we've done stuff in other scattering states, but I would say the vast majority is in Virginia.

Seth Tandett (01:42)
All right, well good deal. Yeah, so we want you want to get us started on mass timber. Maybe let's tell, maybe tell us what mass timber is. Yeah, and how it's made and where it comes from and all that good stuff.

Garrett Braun (01:52)
Yeah, yeah. So.

Yeah, so mass timber, there are a bunch of products within mass timber. Mass timber is just a certain size of wood. And that gives it some fire durability, basically, once you get to a certain mass of wood. And so that's kind of the distinguishing factor to move into mass timber. So there are products called CLT, which is like a layup of woods, LVLs, PSLs, all those different engineered lumber.

products are all, if they're of a certain size, can be considered mass timber. And you can have like heavy timber, which is just a big tree. That could be mass timber as well. You just can't find those big trees as much as you used to be able to.

Seth Tandett (02:39)
So can you, what are, you said some abbreviations there, CLT, yeah, what do those stand for?

Garrett Braun (02:42)
Yes, I did say a lot.

Yeah, so there's just different ways of kind of gluing and laying up that wood, basically. So there's an LVL, which is a common piece of lumber you'll see in residential buildings, you'll see in bigger buildings. It's laminated veneer lumber. And so it's all these laminations of wood that are all glued together. Then there's a similar product called a PSL. It's a Paralam strand lumber.

So it's all these little particles of wood all glued together. So like an LVL looks like plywood with like all its layers. PSLs look like OSB, where it's all the little particles of wood glued together. So OSB is an oriented strand board. So it's a piece of sheeting you often see on the side of houses or on floors in wood buildings. And it kind of just looks like all these little pieces of wood glued together randomly.

Seth Tandett (03:23)
Right.

Okay. ⁓

Garrett Braun (03:34)
So the

one thing to add there is like a CLT. So mass timber, one of the major products of mass timber is CLT. So it's a cross laminated timber. And so they're basically, they have two by lumber that they're spanning one way and then they're doing a layer that's the opposite way. And they're basically just doing this crisscross to create these panels of wood that's CLT. And so that is the product that is dominating mass timber right now.

Seth Tandett (03:58)
So they're making walls and stuff out of that product.

Garrett Braun (04:02)
Yes,

they'll do like floor plates out of it or they'll do walls out of it. Both of those things, yes.

Seth Tandett (04:08)
Okay, so prefabbing those and bringing them to a job site.

Garrett Braun (04:13)
That's right. they're largely abiding by shipping restraints. So you can get a 50-foot long, 11-foot wide panel, just like you could with precast concrete, at least if you're shipping on the highway.

Seth Tandett (04:25)
Gotcha. Huh. All right. Well, that's a good general. And where does, I guess, majority of the product, is it made in the US? Is it from Canada? Where's it coming from?

Garrett Braun (04:38)
Yeah, so I think Europe started the trend. I think there's a lot of manufacturing that happened in Europe. That's where it really started to grow out of. Canada picked it up next. In the US, it's starting to be picked up now. So we've got a project here in Richmond, a three-story office building. I think they're going get their product from an Alabama plant. There's a chance they get it from a Montana plant.

I think they're building a plant or they've built a plant, but it's still in its early stages in South Carolina. So it's coming, it's starting to come primarily from the US. I think projects done five years ago plus were coming from Canada, maybe even Europe, if it was close to the coast.

Seth Tandett (05:13)
Cool. Alright. Where you want to go next?

Garrett Braun (05:17)
I mean, can talk about when we are often, we have owners bring us in, and these owners are like, hey, I want to build this building. I want to build an office building. I want some other use. And I want you to give us some guidance on what system to use, what's the best structural system, that kind of stuff. So we can talk about where maybe mass timber and concrete are competing. think anything under any kind of low-rise structure,

typically not using concrete. It doesn't make sense. can get a better, more cost-effective product with a lot of different other materials. Same thing with CLT. Like if I want a cost-effective two or three story building, probably just going to use regular two-by lumber. I think where it starts getting interesting is when you go from like five stories up to like 12 stories in that kind of mid-rise range. I think right now you see a lot of concrete and steel buildings. I think mass timber will start to...

take over some of that market and can compete and play well in that market. Beyond that 12 stories, you can still use mass timber, but you lose a lot of the benefits. You've got to cover it up for fire protection reasons. You've got to do some things to it that takes away some of its positive aspects. And I think concrete and steel will continue to dominate beyond that level.

Seth Tandett (06:32)
Okay, well let's talk about some of those positives that you're seeing in the low rise.

Garrett Braun (06:35)
Mm-hmm.

Yep, yep. So that mid-rise range, for mass timber, the advantages are that speed of construction. So like you said, that plank, if I can get a 52-foot long, 11-foot wide plank, they can lay down floors really quickly. And they can put up walls really quickly with that system. So I'm always amazed at how fast regular lumber goes up. They can put up mass timber even quicker.

So there's a real speed there that's advantageous. They also brag about having like a smaller labor pool. They say they have teams of like five to 10 people that can put up, you know, a medium sized building that's as big as their group is that's doing it. So it doesn't need a big labor force. So I think big advantage of speed of construction, it's a lighter structure than concrete. So when you're getting into that mid-rise range, maybe you can...

add a few more stories of mass timber and not need a deep foundation system. So maybe you can use it to drive down costs because of that weight. There's obviously, there's an aesthetics appeal. It's kind of a, they've done a good job of branding it. It's kind of cool right now. So there's that aspect. And then they've also done, they've done a lot of work around branding it as a sustainable product. So I think those are the things where mass timber.

is standing out.

Seth Tandett (07:56)
So do you normally have, you said a client comes to you and says they want to build a building. ⁓ Do they, the ones that are mass timbered, is that normally where they actually start with? Say, I want this to be mass timber or do you get to that point and suggest it?

Garrett Braun (08:01)
Mm-hmm.

Yeah, I don't think, I mean, I think it's a newer product. A lot of building owners don't even know about it. So no, I mean, like we, we had a client come to us who was talking to an architect. They've done some mass timber. think that architect mentioned it to them. And so we put together some studies of like, here's one system, a steel system, more traditional steel system, and then here's a mass timber system. And kind of laid out those two options. And I think they were really drawn to the aesthetic side of things. ⁓

Seth Tandett (08:43)
Yeah.

Garrett Braun (08:44)
And so that's what brought them on board for that project. And we actually ended up with a hybrid system. We have a steel column and beam system with a CLT plank on top of it, with a mass timber plank on top of it.

Seth Tandett (08:58)
Why'd you do that?

Garrett Braun (09:00)
So it spans. their zoning requires them not to exceed a certain elevation. And they feel like they're selling a premium product with the CLT. And so they wanted pretty high floor-to-floor heights. And so we were trying to maximize that. If you use a glulam beam, you're going to get a much deeper beam than you would with a steel beam. So we kept the floor system as mass timber, but we have a shallower steel beam to maximize their ceiling height.

Seth Tandett (09:27)
But they want the wood aesthetic. that why you went that direction? Yeah.

Garrett Braun (09:31)
That's right.

Yes, they want that wood aesthetic. Yeah.

Seth Tandett (09:34)
Well,

you could have done it in concrete and did a wood liner in there and made it look like wood.

Garrett Braun (09:40)
It's true. I mean, there's a way to fake it for sure. I mean, think the advantage of CLT, the thing I like, you know, as an engineer, I'm always trying to like, it's been in structural engineers DNA from the beginning of our profession to use less materials. So as a CLT product, I don't, I can just, I love to see the structure exposed as well. And so you can use it for the finished material. You can use it as a structural material. You can do all those things. So.

once you start adding these finished materials, I'm like, why? That's the beauty of it. You don't need to add all those different layers to get something you want.

Seth Tandett (10:11)
Yeah, no, I get that. I the same way about concrete.

Garrett Braun (10:13)
Yeah.

I wish they'd expose concrete more, right? Yeah. I mean, you can do the same thing, right? For whatever reason, I feel like it was cool to expose your concrete for a while. It's gone. It's less common, feel like nowadays, but you still see it. It still can be done.

Seth Tandett (10:22)
huh.

Yeah.

Okay, and so, did we talk, so you talk about floor to floor height? Is there limitations on the, I guess you were talking about the steel, but is there limitations of floor to floor height with the mass timber that you've seen?

Garrett Braun (10:37)
Mm-hmm.

I don't,

yeah, I haven't seen any like floor to floor height limitations. I mean, I've seen, I'll say mass timber from a lateral system standpoint, like using those walls to resist wind loads, earthquake loads. It's not, they're doing some testing. I think they have some promising results, but those aren't in the code yet. And there aren't, we aren't able to use those yet. So I don't think it's a great product for resisting those lateral loads. So we are often seeing.

it as a hybrid system with another product with steel brace frames with a concrete core, something like that for that lateral system. Yeah.

Seth Tandett (11:16)
And then as far as the prefab, what would you say the floor? The floor, what? Yeah, the floor system.

Garrett Braun (11:21)
system is. Yeah,

it's a CLT, so it's a cross laminated timber. And so you can get that in all kinds of spans. So you can just increase the thickness and add more laminations of wood. you can get like, so if you want to get to like a typical concrete span, so like 25 feet or so, you end up with a pretty thick sandwich of wood, you end up with like a 12 inch plus thick sandwich of wood. But you can get there. That's about as far as you

Seth Tandett (11:26)
Right.

Garrett Braun (11:48)
probably going to push it. I think there's more efficient would be to do shorter spans and use a thinner panel of wood.

Seth Tandett (11:55)
Yeah. So I guess is there like a standard or, you know, a piece that they use for the floor? I think you said 11 by 52. Is that right? The extent of it? Is that just typical and they build those things ahead of time and you can just kind of, you know, order them or is there a prefabrication time for each one of these projects? They're prefabbing specifically for that project.

Garrett Braun (12:06)
That's right. Yeah. Yeah.

Yeah, they're prefabbing for that project. So I think it's like precast concrete in that way where they're, you know, you're giving them your design documents. They are then putting together fabrication drawings and they're drawing out dimensioning each piece and part and how all those parts are going to come together. Then they're fabricating each part and then shipping it all out to the site.

Seth Tandett (12:24)
Okay.

in your experience how long has it been that you need to have a design to them so they can prefab for delivery?

Garrett Braun (12:48)
I mean, we've been, so on the project we're working on, we have an office building, we sent out permit drawings a few weeks ago. We've been talking to the CLT provider the whole time, basically. So they know this is coming down the pipeline for quite some time. So I don't know, we'll see how fast they can turn it around, but it, you know, they could probably queue it up however we wanted because we've been talking to them from the beginning. And I think that's...

Seth Tandett (13:13)
Gotcha.

Garrett Braun (13:14)
pretty common with this material, because it's a newer material. There are a lot of things people don't know. And so those manufacturers are kind of acting like the knowledge center for that stuff. And so yeah, the other thing is there isn't a standardized product. So the factory in Montana is designing a slightly different panel than the factory in Alabama. They're using different wood species. They're using different strengths. They're doing different layups. And so

The challenge I think for the industry right now is you don't have a standard product yet. And so you really do need to kind of go talk to your manufacturers so you can understand what their limitations are and what they can do and what strengths they have. So you have to start that conversation early, basically.

Seth Tandett (13:53)
Gotcha.

And then as far as coordinating with MEP and sleeves and things of that nature, are they able to adapt in the field or is this info they have to have ahead of time? Do they make those openings ahead of time?

Garrett Braun (13:59)
Mm-hmm.

They typically make the openings ahead of time. are, know, wood is, you put a saw to it and cut through it. It's pretty easy. But I think the industry is trying to have everything prefabricated. So once it gets out of the site, they can just move. So I think they're trying to push that all early on. So there's an ability to be somewhat adaptable, but they're trying to steer away from that as much as possible. I think that MEP is really sensitive to, right? So these mass timbers,

Seth Tandett (14:29)
Right.

Garrett Braun (14:34)
one of the big reasons for doing it is to expose it all. That means all your MEP is also exposed. And so I think there is, it's just, makes it so that MEP you have to be highly coordinated on from the get go. You can't just be like, hey, you've got 18 inches or two feet of ceiling space, go do your MEP however you want, you know? So I think all of those things are kind of forcing you to lock those things earlier and to be more careful and more exact about how your

doing those things.

Seth Tandett (15:01)
Gotcha. And then the floor itself, you, is there a concrete topping on those or? Yeah.

Garrett Braun (15:11)
Yeah,

so that's where it kind of, this is an area I think CLT could improve a lot. Basically, it's bad in acoustics. So it does not, it transfers sound, it doesn't dampen sound well. And so they're mitigating that by putting either a couple of inches of concrete on top of it or a gypsum topping on top of it or something. And it's taking away some of those benefits. So yeah, you are doing that.

Seth Tandett (15:36)
Yeah. So, yeah, you're exposed at the ceiling, but not at the floor, right?

Garrett Braun (15:40)
That's right.

Exactly. I mean, you can do the reverse too, but at one side of it, you need something to dampen that sound basically.

Seth Tandett (15:49)
just for sound, not for any other reason, fire protection or anything like that.

Garrett Braun (15:54)
No, yeah, not for that. mean, the mass timber, so the fire protection, fires move up, right? So you're most worried about fire protection on the ceiling side. But the idea behind mass timber is it's thick enough that the bottom of it will char. And that charring basically acts as like an insulating material, almost like fireproofing on steel. And that prevents you from having a structural failure, basically. So the whole idea behind mass timber is it's thick enough that it can withstand a fire.

Seth Tandett (16:20)
Is there like a rating for that or?

Garrett Braun (16:23)
Yeah, so we would design towards that CLT for normal loads. Then we would design it for a fire situation, so for reduced loads, but with a reduced thickness of that panel. So yeah, there are. And then you can get different one-hour ratings, two-hour ratings, and your thickness changes based on those rating needs. So sometimes you're having to buy a thicker panel, not for any structural reason, not for any vibration reason, but just to have enough fire protection, basically.

Seth Tandett (16:52)
Okay. Do you know anything about... So you said you have found some projects where it's more cost effective. Do you know anything about insurance? Is the insurance for a building like that? Is it more, is it less than a steel or concrete building?

Garrett Braun (17:05)
Mm-hmm.

Yeah,

I'll say on the cost effective question, I think it's a it's a tough thing to answer. I think for CLT planks, you're often not using finished materials. So you're saving money there. Maybe you're paying more for that CLT than you would a concrete system, but you're saving on the finished materials. You're saving on the speed of construction, that kind of stuff. So I think right now, I think CLT can compete with concrete. I don't think it's beating it, but I think it's because of some of those factors.

As they start, as there's more manufacturing plants, as there's a better labor availability for that kind of stuff, I think it'll be, you might see it be more cost effective. I don't know that it is right now. I don't think it is. What was your second question? There was a second part to that. yes. I think the industry, the CLT industry is trying to educate insurers basically. So my sense is if you just went to your insurer and said, I'm going to build this wood building, will you insure me? They're like, you're going to pay a premium for that.

Seth Tandett (17:50)
Mm-hmm.

Insurance, do you know? Yeah.

Garrett Braun (18:09)
I think the CLT industry has done all this testing to prove, this works, this isn't concerning, blah, blah. So I'm guessing you're paying a little bit of a premium, but not a significant one if you can do a good job of educating your insurer.

Seth Tandett (18:22)
Yeah. Maybe a little bit cheaper than building out of the, you know, your standard lumber that we see so much in Richmond. Yeah.

Garrett Braun (18:35)
Yeah, I mean, like that low-rise stuff, can't beat it. It's cost-effective,

but it's not meant for fire, right? If you put that in a fire, it's going to disintegrate very quickly. So, yeah.

Seth Tandett (18:44)
Yeah.

OK. So we talked about, did we talk, we didn't really talk about, I guess we kind of did, the structural grids and spans. Floor to floor height we talked about. Vibration and acoustics we talked about. Fire design, insurance, schedule.

Garrett Braun (18:56)
Mm-hmm.

a little bit, schedule thing.

Seth Tandett (19:03)
What about,

is there any durability or maintenance considerations when you build with mass timber?

Garrett Braun (19:10)
That's it.

I'll say during construction is a significant one. So during construction, you've got this finished product that is exposed to the elements while you're throwing it up. it is, they are, I think they're still figuring it out. Every contractor is kind of doing it in a different way, but they're having to take procedures to kind of put a protective coating on that mass timber, you know, try to get it so it's not getting banged up because at end of the day, that's what you're going to see. So I think it's a big deal on that end. I think from a long-term durability standpoint, I mean,

wood. I mean, you can go find, you know, 100 year plus old buildings in older cities in the US and Europe that are made out of wood. So the key though is you just got to keep them dry. If that stuff gets exposed to prolonged moisture, yeah, it's susceptible to it like any other wood product.

Seth Tandett (20:01)
So what are you seeing how they're protecting it? you saying they're like putting a coating or something on them?

Garrett Braun (20:06)
Yeah,

think they're putting some kind of coating, painting some kind of coating basically on it that's acting like a temporary barrier to help protect it. mean, they're also just putting, you can put a physical vapor barrier on top of it while you're in construction. I think there's a handful of ways they're trying to navigate that and protect that through construction. But I think that is an area that people's first time they're struggling how to do that.

perfected the method of doing that. Yeah, I mean, there's a lot of different people experimenting out there on that front.

Seth Tandett (20:38)
I did not know that. All right, then the big, I guess, bigger topic, I guess the push that I've seen to the mass timber is the whole carbon footprint debate, but it doesn't sound like you haven't brought it up yet. usually I hear that is why someone is going to a mass timber system versus a steel or concrete. ⁓

Garrett Braun (20:51)
Mm-hmm.

Mm-hmm. Mm-hmm.

Seth Tandett (21:03)
What is, what do you know about that? mean, is, is that being pushed on your job? Is that discussed? And I guess what is, what's your view on that?

Garrett Braun (21:12)
That's it.

Yeah,

you know, I definitely yeah, I think the industry is pushing hard to sell it as a sustainable product. I think there are, I think it's like the cost equation where it's a little bit complicated, you know, so you're, you're using a renewable product in wood, that's, it's renewable if you're foresting in a way that you're growing back the trees, cutting them down, growing them back, right. But you're also right now shipping them from pretty far away.

Whereas concrete, you're getting it from down the road. You have to. So I think that sustainability question, the other thing that as a structural engineer, it's like in my blood to use as few materials as possible in order to meet a safety need, basically. And so mass timber, there's this idea that the more you use, the more carbon sink you have, the more carbon that's in that wood. And you've reduced how much carbon is in the atmosphere by using more of the product, which is

kind of peculiar to me. So I think there's some things that are a little funky. don't think it's, I do think they're selling it. I think it can be a sustainable product. There are real pros to that, but it's not quite as obvious as they might make it seem sometimes. Or clear cut.

Seth Tandett (22:22)
Yeah.

Yeah. But it, it, it, in your, in your example, it doesn't sound like that was what. Yeah.

Garrett Braun (22:29)
That's right. So the building we're

working on, think it was purely an aesthetic. It was like two things, right? It was, we like the look of this and we think we can sell a premium product so we can get people to pay more for rent in our building because we have the CLT product. So it was not, it was not driven by a sustainability approach.

Seth Tandett (22:33)
Yeah. Right.

Yeah, that's honesty is refreshing. It's a cool looking product. We want it.

Garrett Braun (22:54)
Yeah, I mean,

again, I mean, it's a valid reason and that's yeah.

Seth Tandett (22:57)
Yeah.

Huh. Is there anything you think we didn't hit on that we need to hit on today?

Garrett Braun (23:06)
That is most of it. I the one thing I'll say, you know, one place where I'm using concrete that CLT is not going to get me there is just like in unique forms, right? The beauty of concrete is that I can build some kind of shell element. I can build these interesting forms and shapes. I can get a really thin floor plate. Those are places where I'm turning to concrete to solve my structural needs and the desires and wishes of owners we're working with.

Whereas CLT, you don't have that same kind of flexibility. I think that's an area where concrete distinguishes itself.

Seth Tandett (23:40)
yeah, well concrete can do whatever mass timber can do. And I'm a bit biased, but... Well, yeah, I mean, if you're looking at limit, you know, minimizing the, like you said, it's in your blood, the amount of materials that you're using. I concrete does your structure, it can be exposed. ⁓

Garrett Braun (23:47)
It didn't show in that comment.

Mm-hmm.

Seth Tandett (24:05)
It always.

At times I've been on part of projects that I'm often confused on why we're bringing in other trades when concrete could Just be the end all for that structure so when you start When you start introducing other trades your your your you're bringing more folks into the project which exposes you to Not just

Garrett Braun (24:15)
Mm-hmm.

Seth Tandett (24:26)
possibly additional costs, but also safety factors. You're bringing different equipment on, because steel needs different equipment than concrete needs sometimes, and different personnel. And then the coordination to do that work when you bring in other trades, it just makes things way more complex than they need to be.

Garrett Braun (24:35)
Mm-hmm.

Yeah, I mean, we're...

Yeah, no, I mean, I

Seth Tandett (24:54)
But I appreciate it when someone tells me, we're looking for a certain aesthetic. This is what the look we want. Hey, I get it. Everybody's got their taste. And some of these projects that we're a part of, someone's spending a lot of money to build these things. So if they've got a preference, you've got to run with it.

Garrett Braun (24:58)
Mm-hmm.

Mm-hmm. Yeah.

Mm-hmm.

Yeah. Yeah.

Mm-hmm, mm-hmm. Yeah, for sure. No, when it comes to adding in different materials, I I hear you. Like, we are definitely... The thing that pains me the most is when we're, introducing, like, one steel beam into a project or one, you know, cast-in-place concrete element that's not foundations, like, some kind of frame or some kind of random thing. Those things are... It's hard to have those one-offs. It's a lot of expense for something that's not that expensive if there's more of it.

Seth Tandett (25:41)
Yeah. Yeah, for each his own. But I do appreciate you coming on and educating me on mass timber. did not realize they had to protect it when they were erecting during construction. That was one thing I did learn today. ⁓ So I appreciate that.

Garrett Braun (25:45)
That's right. ⁓

Mm-hmm. Mm-hmm.

Nice. Yeah, happy to do it.

Thanks for having me. It was good chat with you.

Seth Tandett (26:04)
Yeah, if folks want to reach out to you, and want to build a mass timber building with you, or even concrete, might even want to do some concrete, ⁓ What's the best way to get a hold of you?

Garrett Braun (26:11)
Yeah, hit me up. Yeah, we do plenty of concrete. Hit us up.

I mean, you can email me. So you can to our website, blueneststructural.com. We've got all our contact information on there. Yeah, just reach out, give us a call, email.

Seth Tandett (26:29)
Cool. And then as always, if you guys check out the show notes, there's, I'll put Garrett's contact information in there and then make sure you check out the links to donate. can donate to the show, you know, help out the podcast. You can also check out the Concrete Logic Academy. There's classes and things on that. you enjoy listening to podcast, if you're still listening, you listened all the way through.

And you need continuing education or PDHs. You become an Academy member. You can log on there. We follow all the standard guidelines to do yourself reporting for that. So yeah, it's that easy. All right, Garrett, appreciate you coming on the show today. All right, and folks, until next time, let's keep it concrete.

Garrett Braun (27:10)
Cool. Same, good to be with you.