Foreword
By Ricky McLain from Woodworks
Is there a building size, height, number of stories, or occupancy in which mass timber works the best? In this video, Ricky takes a look at optimizing mass timber for a variety of projects, but rather than looking at this from a size and scale perspective, the focus is on structural material replacements for other systems in which mass timber works well – particularly post and beam framing.
In this regard, mass timber’s sweet spot can vary between something like an office building and a multi-family building.
Mass Timber Definition:
Mass Timber, also called Engineered wood, composite wood, man-made wood, or manufactured board, includes a range of derivative wood products which are manufactured by binding or fixing the strands, particles, fibres, or veneers or boards of wood, together with adhesives, or other methods of fixation[1] to form composite material.
Ref: Wikipedia Page for Mass Timber
What is Mass Timber’s SWEET SPOT?
Video Transcript:
Well, hey folks! Welcome back to another Two-Minute Tuesday. I’m Ricky McLean. In this video, we’re going to take a look at the sweet spot for mass timber.
What is the sweet spot? I get this question a lot, people wanting to know what is the type of building or scale of building or size of building in which mass timber makes the most sense. And I’d like to back up and start by saying that I wouldn’t look at it quite that way. These are just my personal views, but I wouldn’t look at it so much as what is the perfect size or scale or even occupancy of building.
Really, where I start to look at this conversation is what would that building have been if it weren’t mass timber. You need to think about really what does mass timber compete with or potentially replace the best in terms of other building materials. So, what would the project have been? What would your project have been if it weren’t mass timber construction?
Of course, thinking about mass timber working very well in a post-beam and plate style of construction, I think that starts to lend itself into certain typologies where other post-beam and plate systems would work, such as a steel or concrete building.
Now, when we think about this concept of what would the building have been if it weren’t mass timber, let’s take a look at two examples, both three-story buildings. But let’s say one of these three-story buildings is an office building, and the other three-story building is a multi-family building.
I think you can start to really imagine and see that there’s a very distinct difference in the structural layouts of these buildings. The office building, on one hand, wants to be very large spans, open floor plate, tall ceilings, whereas the multi-family building wants to be much more broken up, compartmentalized, a number of interior walls, sometimes those can be bearing walls, and has a number of compartments within that structure, shorter spans for the floors and roofs generally.
So, I think if we start to look at it through that lens of what are these different structural systems, then we can start to see that perhaps mass timber competes very well in even something like a three-story office building, whereas if we’re looking at a multi-family building, then we can start to see that if it’s three stories, it’s likely already going to be light-frame wood construction. And from a cost perspective, mass timber generally isn’t going to compete well with light-frame wood construction. It was really never intended to be a competitor to light-frame wood construction.
Now, having said that, we are seeing some projects use a hybrid approach in multi-family in that three to five-story range where they’re using light-frame wood walls with mass timber floor panels, expose those floor panels on the underside. That is the exposed ceiling finish, while getting the benefits of light-frame bearing walls in terms of using them as sheer walls, as well as routing plumbing lines, electrical services, those types of things.
Whereas if you start to look at taller multi-family buildings, now we’re talking about in excess of five stories, there are really two things going on there. Number one, from the code perspective, we have to now start looking at the new Type 4A, 4B, or 4C construction types introduced in the 2021 International Building Code. As we get to that taller height, of course, what that tells us is that we can no longer use light-frame wood walls or any type of light-frame wood construction in these taller mass timber construction types. And therefore, what we’re generally looking at is switching that system to a post-and-beam style of system.
So now that we’re in multi-family going taller again, where does mass timber generally work the best? It’s in that post-plate and beam style of construction. And therefore, for multi-family, that might mean that using mass timber in that 6 to 10, 12, even up to 18 stories might be its sweet spot.
So, I think what that shows is that for something like an office layout or even something like retail commercial mercantile, which has generally a more open floor plate, sometimes larger spans, mass timber can really find its sweet spot on a very wide range of building scales. Even a two-story, three-story office building, mass timber can be very competitive. And then going up into taller structures, 10, 12, 14 stories of mass timber construction, mass timber can be very cost-competitive with other building materials, again comparing to what that building would have been if it weren’t mass timber.
And then on the other end of the spectrum, if we’re doing something like a pre-engineered steel building, industrial single-story structure, from a cost perspective, mass timber isn’t going to compete in that realm. So, if an owner is completely fine with the aesthetics and the layout and the use of a building like an industrial pre-engineered steel building, mass timber is probably not going to find its sweet spot in that regard. You can certainly use mass timber in industrial buildings, but understand that there is a very different aesthetic to those two types of structures.
Mass timber has also started to find a resurgence and a potential sweet spot in something like industrial uses where it is replacing tilt-up construction, using mass timber walls and even potentially mass timber roof systems combined with either glue-laminated beams for the frames or even structural steel beams.
Two more things that I think it’s important to point out in this regard is that don’t assume that the entire building has to be mass timber. Don’t be afraid to use mass timber in just parts of a building, isolated areas of a building. This can be a great way to introduce you if this is your first mass timber project or somebody else from the design or development team if it’s their first mass timber project, to get some familiarity with the use of mass timber and find your sweet spot going forward depending on the projects that you generally do.
Also, it’s very important to point out that these sweet spots don’t put you in a box, meaning if you have a project that maybe is outside of the norms of what mass timber is typically used in but you’re very motivated to use mass timber, by all means, definitely use it. This is strictly through the lens of conversations that I often hear and have regarding where is mass timber most cost-competitive and how does it compete well with other building materials.
I’m interested to hear from all of you as well. Where are you finding your sweet spot for mass timber? What types of projects are you doing and finding success with using mass timber? What is your sweet spot?
Well, as always, I thank you so much for watching today’s video. I look forward to talking to you all next week.
For More information please visit: https://www.woodworks.org
Related mass timber posts:
How to start a mass timber building design
External Youtube post: Mass Timber Innovation
