Think Out Loud

As interest grows in the use of mass timber, questions remain about its potential and limits

By Sheraz Sadiq (OPB)
Sept. 20, 2022 6:10 p.m.

Broadcast: Wednesday, Sept. 21

Earlier this month, the U.S. Department of Commerce awarded a $41 million grant to the Oregon Mass Timber Coalition to spur the development of mass timber for use on affordable housing projects in the state. The federal dollars will also fund research into the acoustic and fire-resilience properties of mass timber at the University of Oregon and Oregon State University, which, along with the Port of Portland and several state agencies, are part of the coalition.


Mass timber refers to wood products that are stacked on top of each other and pressed together to form panels or beams for use on large industrial and commercial buildings. The Portland International Airport’s renovated main terminal features a nine-acre-long roof made of cross-laminated mass timber beams and panels. Mass timber is gaining in popularity in the construction industry because it is seen as being a more sustainable material than steel or concrete and can be engineered to be just as strong. But questions remain about the cost of mass timber, its long term sustainability and applications in different environments. Joining us now is George Berghorn, an assistant professor of construction management at Michigan State University, and the research director for Mass Timber@MSU.

Note: The following transcript was created by a computer and edited by a volunteer.

Dave Miller: This is Think Out Loud on OPB, I’m Dave Miller. The Oregon Mass Timber Coalition recently won a $41 million federal grant. It is just the latest boost for an industry that says it can use engineered wood products to replace steel and concrete in many buildings. The coalition includes the Port of Portland, the University of Oregon, Oregon State University and several state agencies. They are bullish on the future of mass timber, but there are still a lot of questions about its cost, its long term sustainability and its applications in different environments. George Berghorn is an Assistant Professor of Construction Management and the Resource Director for Mass Timber at Michigan State University.

He joins us now for a bit of a reality check. Welcome to Think Out Loud.

George Berghorn: Thanks, Dave.

Miller: Mass timber is one of those phrases that encompasses, it seems to me, so many different things, that I’m not totally sure how helpful it is. Can you give us a sense for what is included in the umbrella of mass timber?

Berghorn: Yeah, it’s a great question. There’s a number of different products that fall under that umbrella and the easiest way to think about them, I think, is that these are products that are made up of lamination of wood that are then held together by a resin by a glue, and in cross-section these products that are manufactured tend to be very large. So you might be looking at columns and beams for a building, so very large cross sections larger than 6-8 inches in each direction. You might be looking at floor decks. So again, those floor decks are going to have some significant thickness, 4″ or larger. And then other associated products, kind of in that same grouping of ideas, again, beams, columns, decks, wall panels, things of that nature.

Miller: So plywood, it’s not thick enough to be mass timber?

Berghorn: That’s a great point. Plywood by itself is not mass timber, although there is a relatively new product that’s been developed in the Pacific Northwest called ‘mass plywood panel,’ MPP, which is basically just a much thicker plywood product. So again, it’s very thin veneers of wood bonded together with resin, but the thicknesses now are multiple inches instead of going to the store and you’re buying a three quarter inch thick plywood panel.

Miller: What would that be used for?

Berghorn: That can be used for wall applications. In fact, the laboratory, the mass timber laboratory at Oregon State University uses MPP for a significant amount of the wall structure.

Miller: So, as opposed to having studs and plywood on top the entire wall would be this manufactured wood product?

Berghorn: Correct. My understanding is that most people that are looking at MPP for wall applications are looking at factories, warehouses, you know, large, large open bay, wide-span type of applications.

Miller: So, as you just noted, that seems like a relatively new invention, but how long have humans been making some version of what you’re describing, putting pieces of wood together to make big structural elements?

Berghorn: This all comes from what we used to do with solid sawn wood. So I mean you can go and find structures that still exist that are 1,000 years old that used large cross-sectional solid sawn timber. But the advent of using resin and smaller pieces of wood to make materials is a more recent invention, 1920s, 1930s, for some of these products. There’s products that are a little bit older that instead of using glue to hold the layers together, use nails that’s called nail-laminated timber [NLT]. And you see a lot of old mill construction in the southeastern United States and up in New England that used NLT as floor decks. And they just took lumber and held the lumber together by nailing through the face to make relatively large panels.

Miller: So I mean you’ve given us a little bit of a sense for this but what are the things that mass timber can replace?

Berghorn: I want to talk about that word ‘replace.’ You know I think mass timber becomes a complement to the other conventional building materials that we have available in our toolbox to build with. So typically we see large structural elements that are made of either steel or concrete. And so mass timber has the ability, either to work with those systems in a hybrid form – We have a building on campus at Michigan State University that’s a hybrid of steel and timber – or as you suggested, in some cases, some steel or concrete elements can be replaced by mass timber elements.

Miller: What would the reason be for both of those versions?

Either the full replacement or the hybrid?

Berghorn: Yes. Let me start with the hybrid. The hybrid approach basically leans on the strengths of both materials and in the case of our building at MSU, we had some critical column lines in the building that when we looked at what the cross-sectional area of those columns would have to be, if they were rendered in wood, they would have been too large to accommodate what we wanted to do with the building…

Miller: Because you need more wood to hold up something than you would in steel, steel is just……

Berghorn: Correct.

Miller: …stronger for size…?

Berghorn: Yeah. So wood typically, this is a little variable by species, but would typically is stronger on a strength to weight basis than steel, but to get that weight, because wood is not as dense as steel, you’re looking at a much larger member in many cases. So yeah, we just would have ended up to have too large of a column in our building. And so that was a perfect application for steel. Let’s get a smaller cross section. We’re not taking up as much of the floor and then we can put wood where we…where it made more sense, where it fit the program for the building. And then in the cases of where you would replace a conventional material for a mass timber material, there’re a lot of reasons why building owners and developers are making that call. Some of it is to support ESG Goals – environment, social and government goals for corporations or for business entities. Some of it is people like the look and the feel of wood. We see this in our building. Students come into that building, we have exposed wood columns and the students call it out, they actually like to go over there and touch the exposed wood and sort of interact with it and there are studies that suggest that people have less stress and students perform better when they’re in environments that have more natural materials exposed. There’s a lot of reasons and I think the overarching idea is that as designers and constructors, we want to use the right material in the right application and mass timber just gives us another tool in our toolkit.

Miller: Does that make it more like that? The last part, that people want to see and feel and be around wood and in the same, I mean, and you rarely hear someone say that about concrete or steel beams – not that they can’t be made in pleasing ways,...

Berghorn: Sure…

Miller: …but you rarely hear someone say, I really want to go and touch that steel beam, does that change the way these are incorporated in designs? Are they more visible on purpose?

Berghorn: I would say so, yeah, I mean when I think of some of the more well known mass timber buildings that have been built in the US, we are exposing more of that structure than you might be doing if you were rendering that same building with other materials.


Miller: If you’re just tuning in, we’re talking right now about the promise, but also the limitations of mass timber. We’re talking with George Berghorn, who is the Research Director for Mass Timber at Michigan State University. When I have heard people talk about mass timber in the past, it can sometimes sound like a magic cure-all, sort of like the way people talk about hemp or in the last couple of years maybe they did that, ‘this will sequester carbon, bring back timber jobs and manufacturing jobs, solve homelessness because this is, this will be the cure for affordable housing or at least a component of it.’ We can dig into all these issues one by one, but how do you separate the hype from the reality?

Berghorn: It’s a great question and before I was in academia I worked in the construction industry, I was a superintendent, I was a project manager. So I tend to take those sort of ‘magic bullet’ ideas with a little bit of a grain of salt I guess, from my own professional background, I’m a little more skeptical. So how do you separate hype from reality? I’m actually in Madison, Wisconsin, right now, at a 2.5 day conference that’s being put on by the Forest Service that’s called, ‘They’re Trying Real Mass Timber Research Workshop,’ and what we’re doing at this workshop is we’re actually trying to dig into what are the most critical questions about how this material performs, how buildings that are built using it perform, and we’re trying to answer those questions from both an academic and industry-centered perspective. So, it’s so far been a day and a half of great dialogue, great questions, great ideas that are bubbling up to the surface. And that’s some of what we’re trying to do is engage with credible folks within the research community that can answer some of those critical questions. And then, the cool thing with this group is, we’re not just a bunch of academics that then talk to each other. Our work is then meant to be public facing. So the goal is that any work that we do through this kind of loose confederation of actors that come to these events, that we would be able to publish and share that information with the public so that it’s accessible and available to a much wider audience.

Miller: What do you see as the most important questions that are being asked right now at that conference?

Berghorn: Yeah, great. So there’s a number of questions. Actually, one of the sessions that’s going on right now, I’m getting team chats from one of my colleagues, they’re talking about,...

Miller: You’re supposed to turn those off before this radio interview…

Miller / Berghorn: Laughing

Miller: Unless it’s vital.

Berghorn: It’s interesting because some of the questions that are coming up have to do with, ‘can we use salvaged lumber, reclaimed lumber from demolition and deconstruction projects in the manufacture of this material?’ And the reason I’m getting these pings on teams is because I have a couple of students who did some pilot scale work on that topic about a year ago.

Miller: Is there an answer to that? That seems like that’s a great question. I mean because we still haven’t even gotten to the plantations necessary…

Berghorn: Sure.

Miller: …to sustain this on a big level. So from what you’ve learned so far, is it possible to take wood from an old stick built house, throw it in a dump truck and then take it to a factory and reuse it?

Berghorn : The work we did and then there was some work that was done at Oregon State around the same time, both of our groups found that it seems like this is possible. We had very positive results. We were also very careful in how we evaluated the lumber that we brought in, we didn’t just, you know, sort of randomly put any piece of lumber that we found into making these products. But yeah, it showed great potential you know, but of course we’re operating at a pilot scale. So now the questions become, well how do you scale that up? What would, what would a manufacturing process have to look like to now bring this material in? What would a procurement process have to look like to bring this material in? But I think the most fundamental question was, ‘Does the engineering work?’ If the engineering works, then we can figure out the supply chain and the economics and those pieces.

Miller: But there are other big questions about scaling. So let’s turn to the newly cut wood.

Berghorn: Sure.

Miller: If this were going to be a much more common and also, you know, economically feasible tool as you said, to be used in all kinds of applications, what is the scale of logging that would have to be done in order to sustain it?

Berghorn: That’s a good question. I don’t know that anyone has a direct answer right now, to say if you increase US construction activity by 5%, this is where you’re, where you’re going to be. There have been some studies done, kind of larger, larger scales, both spatial and temporal scales and some of those studies have suggested that until we get to a much, much, much larger percentage of buildings being built with mass timber – And when I say much larger, I mean like the majority of the buildings that we build shift over to mass timber. Most of the studies that I’ve seen suggest that we have the ability to support that with the forest resources that we currently have in the US. The Ascent Tower is fairly famous, at least within my circles, fairly famous building in Milwaukee – Just opened up, it’s currently the tallest mass timber building in the world and it’s right here in the Midwest in the US.

Miller: How tall is it?

Berghorn: It’s 19 stories of timber over six stories of concrete, so it’s 254 feet, I believe is where their final number came out. It was estimated, they did some, they did some scientific work to look at the amount of timber that went into that building. The answer came back that it takes about… it’s on the matter of minutes for how long it takes for North American forests to regenerate that amount of timber for that building. So, you know, from what we’re seeing anyway, the data that we’re seeing suggests that until we get to just a significant amount of our construction changing to mass timber, we might be okay. And I’ll say like, just personally, I don’t think that I see a day that 80% or 70% of our construction shifts to mass timber, I think mass timber will always be a viable alternative, but I don’t think that it becomes a 1-1 replacement for every construction project in the country.

Miller: What’s the climate change argument for using mass timber in certain applications as opposed to steel or concrete?

Berghorn: Right now the embodied carbon to manufacture mass timber, so all of the emissions that you might think of that go into the manufacturing process, the embodied carbon burden of mass timber is somewhat lower than the embodied carbon in concrete or steel. And I should say, conventional concrete and steel. Additionally, that wood, all of that, that wood that’s being harvested and being turned into mass timber products is storing carbon inside of it, that’s been sequestered from the atmosphere. So atmospheric carbon dioxide, we all remember like, you know, photosynthesis from our elementary school days, all that atmospheric carbon is used to put carbon onto the body of the tree and that carbon is locked away, stored away in that wood. And if we’re building significant buildings, that we expect to have significant lifespans like our building at MSU is expected to have a 100-year lifespan, you’re now storing that carbon within the building. The question becomes, though, and this is where some of the question and the concern and maybe a little controversy has come into play, is ‘Well, what happens to that building at the end of life?’ What happens to those large wooden members, if they just get taken out and land filled, we’re just releasing that carbon, we’re just releasing it, you know, 50 to 100 years later.

Miller: What about cost, right now? You mentioned that you worked as a construction superintendent and a project manager. On average, right now, how does the cost for a mass timber product that’s analogous to other conventional products? How do they compare?

Berghorn: The comparisons are a little bit all over the board, as you might imagine, because buildings are all so different, right? It’s really hard to find two buildings that are exactly the same. So it sometimes is a little bit of an apples and oranges comparison. But what we know is that the material itself tends to be more expensive than concrete or steel. So if you’re looking purely from a material cost, things are going to be higher. There is some potential for savings during the construction process. These buildings do have the potential to be erected a little bit quicker. And of course, if you’re building your building quicker, that means you’re saving some money. You don’t have your trailer out on, out on site out on rent for as long, don’t have your Superintendent out on site as long. So quicker can mean a little bit of cost savings. But the other interesting thing, as I mentioned before as compared to steel, wood has a higher strength to weight ratio, so, because wood is lighter, you can actually downsize the foundations sometimes on these buildings. So if I go back to the Ascent Tower in Milwaukee, they were able to downsize their foundation and just doing that, saved them about a month of construction time and…

Miller: Because there’s less concrete that has to be poured into the ground first?

Berghorn: Right, so in their case they were on a pile foundation, I think they, I think they used driven piles, so you’ve probably heard a pile driver banging away before. So they were able to use, my recollection is, 100 fewer piles, which not only saved a month, but also saved the people that live and work around the site a month of a pile driver banging all day long.

Miller: How much standardization is there in mass timber right now? I mean, can you or could somebody who’s building a medium sized building somewhere, say I want 17 of these regular sized pieces of this flooring and of these mass timber columns and I want them next month, are there regular sizes?

Berghorn: Not really. The majority of projects, the majority of manufacturers are doing custom layups, custom fabrications. that was actually one of the sessions I was in at the conference yesterday was talking about – ‘Do we need standardization and is that something that would benefit end-users as well as the manufacturing community?’ There is one manufacturer in the US who is right now looking at trying to shift to a little bit more of a commodity product. So they want to basically offer, kind of a standard sized product and they think that they can disrupt the market by doing that and… and having shorter lead times to get to the material, having a more well understood catalog of what’s available. But as an industry, we’re not there yet.

Miller: And finally, what about risks of various kinds? Something about climate change-induced risks like fires or flooding or seismic risks like earthquakes?

Berghorn: So these structures do tend to perform pretty well, with …with seismic forces. There’s actually a very, very large seismic test that’s going to be going on at the beginning of next year out in San Diego. I think it’s a 10 story building that they’re going to shake for about two months, to study performance of taller buildings. But the studies that have been done so far on seven story buildings, some other variations of height, have been pretty positive because wood does have some ductility, some elasticity to it that particularly concrete doesn’t perform, you know that as well in terms of its ductility. Fire, there’s fire questions to still be resolved. There are fire questions to understand. I’m not a fire expert. But fire testing has been done on these structures. You can meet two hour fire separation, which is a requirement for a lot of different building types under code in the US. You can meet two hour fire separation with mass timber. You know, you think about like a campfire, you know you’re sitting around the campfire and then somebody throws in a big log and that big log never really burns, it just… it just chars and then it kind of sits there and smolders for a long time. That’s what we’re seeing. You know the large cross section kind of prevents burn-through. Flooding was your last question, long term exposure to water, mold growth. Those kind of questions also came up yesterday. Those are areas that we still need to learn a little bit more about. We want to understand under a greater variety of circumstances.

Miller: George Berghorn, I will let you get back to this meeting. Thanks very much for joining us.

Berghorn: Thanks so much, Dave, appreciate it.

Miller: George Berghorn is Research Director of Mass Timber and an Assistant Professor of Construction Management at Michigan State University.

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