Timber's popularity growing within commercial construction
Projects that used to consume thousands of tons of steel and concrete are being built with arguably the world’s longest and most renewable industrial resource – wood.
The North American timber construction industry has transformed significantly over the past decade. At the turn of the 20th century, steel and concrete widely replaced wood in the construction of commercial buildings.
Nowadays, advances in fabrication techniques and connection engineering, along with a renewed interest in timber as an architectural medium and trends toward sustainable construction, are providing an environment for the re-emergence of timber in an array of projects.
Susan Jones, founding principal of Seattle architectural firm atelierjones, is among the veteran architects advocating for the advancement of the acceptance of mass timber construction in the United States. Her firm’s work has been recognized with numerous national, regional and local design awards.
Jones also is among the 18 American Institute of Architects’ representatives who are part of the International Code Committee (ICC) working to test the effectiveness of timber in construction projects and to define codes outlining building practices.
On the heels of the Timber in the City Symposium at Parsons School of Design this month in New York, Jones spoke with ProudGreenBuilding.com about the increasing popularity of mass timber commercial projects and the impact research will have on future building efforts.
Proud Green Building: What was the message you tried to convey about timber at the symposium?
Susan Jones: We introduced the audience to mass timber, to our work and the hurdles and opportunities we saw. We were joined by a panel, and we had an engaged discussion. The question was really what can we do to move this forward. If there are hurdles, what are they and how can they be identified and mitigated?
We all were involved with various levels of building with mass timber already and had experiences to share. Most were optimistic in determining what can be built today and what are the challenges. Sometimes, that message gets lost in translation.
For example, there is so much focus on building above six stories, which is currently not allowed in any of the ICC codes today. There is tremendous opportunity under six stories, and that’s where our work has been currently focused.
PGB: Are more and more architects and engineers looking to timber first when it comes to commercial projects?
Jones: Especially in the Northwest, where timber is part of the cultural heritage. Portland has built several beautiful, wonderful NLT (nail-laminated timber) buildings across the commercial landscape.
Architects in Portland and Seattle - because we’re so close to the Canadian border - are well aware of what has been done with wood over the last decade or so, especially with the Olympics back in 2008. There has been a lot of awareness. Certainly, when it’s appropriate, we’re definitely open to using wood. But BC’s Wood First policy that has been implemented several years ago was a huge impact on the BC (British Columbia) market. If something were to go ahead in the States, or even on a state level, it would have an excellent impetus on working with wood.
PGB: Why is timber becoming more prevalent in commercial projects? What is driving this trend?
Jones: Often you talk to a timber or lumber mill person or forester, and they say, “What’s with this trendy thing called timber? We’ve been doing this for 30, 50, 100 years and you architects were never interested in what we were doing. What’s going on? Are you guys finally seeing the light?”
I always laugh when I get a comment like that.
The impact of climate change has affected our world deeply. As an individual, as an architect, we all understand that we have a huge role to play in how our profession can affect climate change. It is one of the biggest ethical challenges our generation faces.
We’re responsible for specifying materials. We can specify steel and concrete. We can specify wood. Of course, this is done in concert with response to budget, our client’s needs and their market perception, etc. People are starting to get it. Architects have been leaders over the last three or four years to help their clients understand this can both be an environmental choice of materials and a beautiful one.
That’s my personal motivation. Wood - when it can be exposed - is a beautifully sensitive material that reflects light and daylight in very different ways and creates a calming sense of nature when you enter a space, whether it’s a commercial space or residential space. There’s just a different feel when you’re immersed within the textures, smells and touch of a natural environment.
The majority of growth has happened in our cities. We all love our dynamic, urban environments, but when you have the opportunity to touch a piece of wood, there’s just something very different about it – its smell, its texture. There’s a real connection to nature we all instinctively long for.
PGB: What makes timber a good alternative to steel or concrete? Is it as strong and durable?
Jones: On the West Coast, light-framed timber has always been around in low to midrise multi-family, up to six stories. That’s been a big stalwart of our multifamily construction market. As you start to get higher, building codes restrictions start to phase out light-frame timber. The excitement of working with mass timber is that it you are working with large, somewhat awkward but very strong and lightweight panels that can be prefabricated. Typically, they’re 8 feet wide by 40 feet long by 4 to 6 to 9 inches thick, depending on how many layers you use.
If you imagine an equivalent to concrete or a precast concrete system, they’re lighter than that and very strong. They can create a repetitive, modular system of construction. That’s a huge advantage to our contractors who, once the construction industry gets used to this system, they won’t go back because it’s such an easy modular way of putting things together on site, especially in tight urban sites.
It’s quicker, it reduces noise, reduces pollution with trucks and it appears that the schedule is impacted favorably to 20-30 percent, which is no small amount when time is money. A lot of this, of course, depends on the individual project and consistency in the quality of design and shop drawing coordination that’s being executed by the architect.
From a design point of view, it puts more control back into the architect’s hand. All of that work is done prefabricated in the factory before the panels even arrive onsite. So there’s a great deal more work that’s been done beforehand, but the architect takes charge of coordinating the panels with the fabricator directly. Depending how well the architect does, it can go together very fast with extremely tight and very precise tolerances. It’s an exciting environment to work in when you’re looking at really accurate millimeters or an eighth of an inch tolerances, which makes your finish work and exterior wall systems much easier to apply. It’s a great material to work with.
Once contractors understand that and owners realize the benefits, that’s going to be an advantage in the contracting industry.
Those of us deeply involved in this the last five or six years have been building that expertise to lead that process in a different way than the typical architect would lead a construction process or be part of a team. We’re very conscious about being good, integrated design team players. It is a different role, but it’s exciting for us who have been involved for a while and understand how to use it to everybody’s advantage.
PGB: Is timber for every project?
Jones: Most likely, yes. But the real barrier for taller buildings at the moment is codes. To answer that question appropriately, the answer is no. You can’t build over six stories without special approvals. However, there’s nothing prohibiting that in terms of its constructability or structural integrity.
One of the things that’s been really exciting recently is to watch the (cross-laminated timber) Framework building in Portland get closer to being approved by the municipal authorities. Portland is in a high seismic area, as is Seattle and Vancouver – the seismic codes are much more stringent on the West Coast than they are elsewhere in the country – so it’s exciting to seriously consider building a 12-story timber building in the next couple of years here on the West Coast.
That tells me the sky is pretty much the limit. If you look at it carefully, there’s no technical reason why you can’t go to 20 stories and probably 40. The real issue is codes, and the foundational issue, is fire codes. We can convince our structural engineers that our buildings are safe. We can convince our structural reviewers that they’re safe. The fire community has a longer way to go.
I’m one of 18 national code committee members, and the national American Institute of Architects’ representative to the ICC. Most of the committee’s focus has been on how to understand better and deal with fire concerns. If you look at the codes, and this gets a little technical, there’s Type 1A and Type 1B and those buildings have a high height limit with what are considered non-combustible materials, which are steel and concrete. When you add a combustible material, i.e. wood into the mix, there are a series of concerns that have to be met.
We’re going about that in a very methodical way. The good news is that the committee is functioning at a high level, all parties are involved, there’s a considerable amount of give and take and scrutiny.
The result is that we’re creating some important fire tests that will be some of the most rigorous in the world happening in the spring. Funding has been procured for these million-dollar fire tests. They take several weeks to construct a two-story apartment dwelling with a stair core and a corridor to mimic real-world conditions. Then we’re going to set the whole thing on fire five different times to see how it performs!
Assuming those fire tests go well – and we assume they will based on all of the other tests that have been done internationally and in Canada – I think you’ll start to see some fast movement on the codes and things will fall into place very quickly in the next year or two.
PGB: As far as the discussion of regulations related to timber, are they centered on fire codes? Is there concern about strength and durability?
Jones: The structural properties of the panels are fairly extraordinary. They have a very high level of shear and lateral resistance. Because the panels are lighter than typical concrete, the gravity loads are less and the foundation requirements, which need to be concrete, are known to be less.
Some of these aspects need to continue to be tested, but I think there’s a general acceptance in the industry about the structural issues. The fire question is an area we need to continue to be thoughtful and careful of and do strong research on.
But rest assured, all of the existing buildings, such as the built 14-story tall timber Treet building in Norway, for instance, or 18-story Brock Commons in Vancouver, would not have been built without careful, thoughtful scrutiny. There are many ways to protect the wood. They include gypsum wall board and the natural charring ability of the wood itself.
For instance, there’s really rigorous research going on right now about how to measure that char layer. What that means is that when a heavy timber member burns, it burns in a very slow way from the outside in and tends to char over and protect the inner structural layers from being burned further. There are scientific ways to design so that in the rare case of fire or event when a system might fail and that member starts to burn, there could be a protection borne out by the natural wood properties in order to achieve standard 2-hour fire rating.
If the testing bears that out, it will add a lot of momentum to the code process.
PGB: Will the tests next year dictate how the timber market and timber construction industry move forward in relation to commercial structures?
Jones: Once these tests results are in place, that will be the trigger. Once the codes committee – and I should stress that I don’t speak for the committee, I’m only one member of 18 – performs the tests and, assuming they’re performed at an acceptable level, once we have data that is very trustworthy and carefully thought out, the code committee will act quickly to assemble model code language. Once that goes ahead, it will go into a broader voting process sometime in early 2018.
Once the language is assembled, even in draft form, it can be used by authorities and cities at their discretion. They’ll know it has been carefully scrutinized by an interdisciplinary body.
Everybody is waiting for that sweet spot to move quickly ahead for construction of taller timber buildings. The industry is aware that for multi-family buildings up to six stories it makes sense to use light wood frame construction. But between seven and 14 stories, it is usually too cost-prohibitive to use concrete or steel, and light frame wood is not allowed. So, once that height is allowed for mass timber buildings, I see the industry moving very fast to adopt mass timber construction.
It’s really exciting to imagine growing your own high-rise from a handful of seeds. It’s the only material that is renewable.
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