This is Forest to Frame, where we explore how restoring forests creates beautiful spaces. A podcast dedicated to conversations with industry leaders, shaping the future of the forest industry. And now, here's your host, Russ Vaagen

Hey everybody, Russ here, Forest to Frame podcast. Today, I wanna talk about something a little more technical. It's about lumber and moisture content when it comes to mass timber. A lot of people think that you can use low quality lumber, put it into CLT and it's gonna make a great product. The fact is that we need to have high quality lumber. And not only that, we need a specific moisture content range. So you may have heard lumber being called KDHT. Well, that means kiln dried and heat treated. And essentially, if you're buying a two by six or a two by four from your local lumber store, it's going to have that stamp on it. What that means is the lumber is kiln dried to 19% moisture or less. and it's heat treated, which means that the core temperature got up to, I believe it's 150 degrees for an hour, 30 minutes or an hour. I can't remember the exact, but that's the heat treated portion. And you'll see some lumber that doesn't have the KD on it, just has the heat treated. That's to remove any living organisms. So, any of the fungus, any mold, any potential bugs or anything that might be in that wood that could then be transferred to something else or rot it in the future. So that's just like standard lumber jargon for kiln-dried lumber, heat-treated lumber. In the mass timber world, And prior to CLT, we had just glue lambs. And in glue lambs, there was always this grade called lamb stock, and it was different than your standard visual grades. And there really was not much if anything to do with machine stress rated lumber, which is the E rating that gives you the specific low low end strength of each piece. And so you have the you have these grades that are a little different than standard, but there's also a moisture conference or moisture. content percentage that's lower, it's a 15% or lower moisture percentage. So, you know, that's doesn't sound like much 19% for standard lumber 15%. But the reason is that the lumber is like a rigid sponge. And it's constantly acclimating. So if you ever put hardwood in your house, A lot of people have you notice that if you did it yourself or you had a contractor do it, it was solid wood you set it in the House for about three days or whatever the acclimation period is for your area and what that does it allows that lumber. to dissipate any moisture or pick up any moisture that's going to have in that house, which is going to end up keeping it from expanding or contracting with any of the moisture that's changed from what's in the lumber to its final installation point. So that also affects other lumber and it affects mass timber. And so when you put a glulam together, if it's got a high moisture content, it's going to acclimate, remove moisture, which is going to cause that piece to shrink. And it doesn't seem like a lot, but when you have lots of layers, You know, a millimeter here millimeter there, but you do that over the layers all of a sudden you're going to have a lot of change so by drawing it down to 15% or less, it has good adhesion let's put together and it doesn't move very much, which is also important. For cross-laminated timber as part of the APA and other grading agencies PRG 320 guidelines for CLT, the CLT guidelines say 12% plus or minus three. And as you could probably imagine, because it's different and because we're in a commodity lumber world, it de facto goes to 15% or less, just like lamb stock. We have found that we're actually trying to get to that 12 on a consistent basis. We have our own kilns here, so we can do that if we need to, but the mills that we work with, and specifically Vaughan Brothers, who we work with mostly, have done a really good job of getting it down to that 12% moisture content and being consistent. which means that when we make our product, it doesn't move very much. It doesn't expand and contract much at all, but it still does. The beauty of cross-laminated timber is that you are putting the layers in long ways, and then you put another layer in this way, so it's not shrinking the same direction. We don't see the lumber shrink in length. as much as we do the depth. So it has to do with the way the cell structure of the wood works, and I'm not a specific wood scientist, but I've been around it enough to see it. And so when you have that, you have two counteracting forces that essentially hold it together. You may get some cracking if you have a moisture differential that needs to, you know, it needs to release moisture and it isn't able to hold its shape. But that's okay. Cracking is not a bad thing in the product. But in glulam, because they're all going the same direction and they're all essentially equalizing moisture the same way, they'll shrink. And so it's really important to get that moisture content as close to the end installation point as possible. But that's also a little bit tricky too. And I think it's a place that we are learning more about as an industry, both in the building industry, construction and design, and in the manufacturing of these mass timber products, because Sometimes when you install something in a building, especially in, let's say, Western Washington or Oregon, where you do get a lot of rain, especially in the springtime, you might be installing in a very wet, moist environment. So you may get some absorption of moisture while you're doing the install, and then you put the building together, and then the building gets dried in, and it's much drier, and maybe doesn't have great humidity controls. So now you go from a moist environment where the woods kind of swelling a bit to a finished drying environment where it's contracting a bit and you can develop some challenges there in the glue lamp but it's. you know, it's something where it's really important that we manufacture the lumber correctly, specifically getting that drying content down. And that stability just makes a project, you know, much better. And then, you know, using the lumber, and the mass timber in a way that we understand. So if we know we've got a glulam in a certain area and it has the potential to move, we need to just kind of think about that. Because mass timber is beautiful, but it's beautiful because it's natural. And it's natural, it gives it a little bit more you know, flexibility, which creates a tremendous amount of benefits, but it also creates its own little challenges. And I think that most people just think that you can use any lumber for CLT, as long as it's the right species, and it's, you know, two and better. And they say you can use a number three in the center. And if you don't know lumber grades, it's just a two and better is I would say a kind of standard grade, a mostly straight, modest size knots, very little wane. That's kind of what you're looking for at the home store, similar to your stud grade. But a number three is going to have wane, bigger knots, potentially a little rod in there. And yeah, you can squeeze that into the center of a CLT. The problem that we see is that I'm not on number three or created equal. It's not just because it's got some lane. It's not just because it's got some knots that are larger or that have fallen out. It's a whole host of things. So certain number of threes, yeah, you could use it for CLT with very little problem, very structurally sound. And then others are gonna be really poor in quality. So it just creates a differentiation. So we choose to use as much 2M better or a specific CLT grade that we worked out with the mill as possible, just so we can have really good consistency. And there is a cost difference there. But when you think about all the manufacturing, that cost differential doesn't seem to pay dividends in our opinion, because you can create something that is pretty low quality or doesn't meet the client's expectations. When you're doing a bespoke custom piece, each specific piece of CLT and glulam goes in a specific spot. If you create something that doesn't meet the expectations or is going to have some sort of structural problem with it, because let's say it had rod or something in the wrong place, and you're entering that into the process, maybe somebody is new and they put the wrong piece of lumber in the wrong spot. all of a sudden, you have to go make that specific piece, you don't just pull a piece of CLT out of the stack, cut it and send it down the road. And you know, these projects may be across the country. So for us, the risk of putting that, you know, less expensive, lower quality lumber in there, just to get a, you know, a it's not even a percentage point of cost out of it, just doesn't seem like a very good value proposition to us. So long and short of it is we try to focus on getting the moisture content right, in particular for the products that we need to for stability. And if you start with the right moisture content and in our world, we really don't use anything that's over 15%. And in actuality, we're down in the 12, 13%, with a high percentage of what we're doing. And, you know, having the kilns here, we can identify if, you know, there was a mistake made in the process, and we get lumber here that's higher moisture content, we can pull it off and dry it. And it just makes for better quality product, so these are some of the things that we think about as we go along and make the the mass timber products out there and it's just I think nuances that make the difference between. Good looking mass timber products and. just incredible high quality, uh, mass timber buildings. And that's what we're focused on doing. And, um, that's what we've, the relationships we've created with our clients are all about. So, um, yeah, hope you learned something here about lumber drying, the differences between standard lumber, mass timber, lumber, lamb stock, CLT stock. They're a little different. Um, and we've got a long way to go as an industry to, uh, you know, further develop these things, we can be more efficient in the use of our lumber. Now, I mentioned MSR, we could use machine stress rating to make better products, in my opinion, and in many cases, I think we could actually more specifically tailor the structural integrity of the lumber to the product. And then we may be able to do longer spans with less depth, which means we use less wood, which means we can pass savings along to the marketplace and to our clients. So yeah, I hope that provided some value for today. And we look forward to seeing you on a future Forrest of Frame podcast. Thank you.

Russ Vaagen

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