If you’ve been following the conversations here at Mass Construction, then mass timber is likely something you’ve heard of by now. It has come up on the podcast and been featured as something to keep an eye on in Mass Construction Highlights and on Social Media. It makes sense to dedicate an entire blog post to this topic because it’s an innovative product that has been used effectively in Europe and Canada for years, and now companies are starting to use it in the US, too.
So, what is mass timber, or what’s commonly referred to as cross-laminated timber (CLT)? Well, the American Wood Council says that it, “is a category of framing styles typically characterized by the use of large solid wood panels for wall, floor, and roof construction…”
Products in the mass timber family include:
- Cross-Laminated Timber, which is dimensional lumber glued together at a right angle.
- Glue-laminated Timber, referred to as Glulams, which are glued together with the grain running in the same direction.
- Nail Laminated Timber is dimensional lumber laid on edge parallel to each other and nailed.
- There is also structural composite lumber (SCL), which consists of laminated veneer lumber (LVL), laminated strand lumber (LSL) and parallel strand lumber (PSL).
I’m not an expert on any of these products, nor is it the intent of the article to describe the uses and number of various products, but to look at the trend because it is touted as a more environmentally friendly product that produces a better environment for the end user. As well as being an efficient method of construction. In other words, it is considered LEED positive and WELL positive and can be built real fast.
While there have been other innovative, effective products out there, this is one that is making its way to the states. Lendlease, who built with the product internationally, decided to use it for a hotel near Huntsville, Alabama. It is a 62,688 ft2 structure that includes 92 guest rooms and utilized 1,200 CLT wall panels and 200,000 CLT fasteners. It took the 11-man Lendlease crew 10 working weeks to erect the building, which is a 40% reduction in crew size and man hours, and 37% faster than conventional framing materials and methods.
If LendLease experienced such a substantial increase in productivity right out of the gate, then just consider what happens when we become more efficient in our use of mass timber? Proponents of the product claim that buildings can be built faster, safer, and with smaller crews than traditional steel, concrete, and light wood frame variations currently in use.
Mass timber has something else on its side — code changes. The 2015 editions of the IBC and IRC both specifically call out CLT as an allowed use in Type IV construction, basically treating it as the equivalent of heavy timber. What does that mean? Well, prior to the 2015 edition, any use of CLT would have required an approval from the building official under alternate means and, in most cases, would result in a appeal. Now, assuming one complies with the massing of the building, you can build with CLT “as of right.”
Some states have taken it one step further by allowing mass timber buildings to exceed the six stories allowed by the IBC. Oregon passed an addendum to its state code via a “statewide alternate method (SAM), a state-specific program that allows for alternate building techniques to be used after an advisory council has approved the ‘technical and scientific facts of the proposed alternate method.’” This allows for buildings up to 18 stories based on the type of construction. The state of Washington has recently passed legislation that would direct the state’s building code council to “adopt rules for the use of mass timber products for residential and commercial building construction.” Additionally, the Washington State Senate is working on a bill that “would require all public buildings in the state rising 12 stories or less be built using Cross-Laminated Timber (CLT).”On an international level, the ICC is looking for future additions to update codes allowing for wood buildings up to 18 stories, though the proposed changes would not be adopted until 2021 at the earliest. The NFPA, seeing this trend coming, will have a new chapter its next edition of NFPA 241 that will cover large/tall wood structures.So, while that 12 story building in Oregon was permitted but didn’t move forward because of cost, there is no reason to cast mass timber aside. Cost is obviously an issue with the product; there does not appear to be a lot of producers in the US, but as states like Washington and Oregon put measures in place to encourage production it should only drive cost down. In fact, everyone’s favorite construction start up, Katerra, is betting big on CLT by opening a plant to produce the product for themselves and acquiring Michael Green Architecture, the leading mass timber designer in North America. I’m reading tea leaves here, but the tea leaves are getting clearer and clearer. If you’re in construction bet on mass timber.
In addition to the Alabama hotel built by Lendlease, here are a few other buildings that have made the news.
- In 2017 The University of British Columbia in Vancouver built the 18-story, 174-foot-tall Brock Commons student residence, claiming the title of tallest timber structure, for now. This surpassed Treet, a modular 14-story, 160-foot-tall housing project wrapping up construction in Bergen, Norway.
- A 500,000 feet2 mass timber office space is coming to downtown Newark, New Jersey. It has three buildings, one taller than the other, topping out at 11 stories high.
- Milwaukee-based developer New Land Enterprises is planning to build a seven-story office building and proposing a 21 story residential building which would be the tallest in North America.
- Oregon had a 12-story building permitted, but failed to follow thorough on construction because the product was cost prohibitive.
- In 2016, a seven story high-rise T3 Tower went up in Minneapolis, Minnesota
- In Amherst, the University of Massachusetts built a CLT “Design Building” to house their; architecture, building and construction technology, and landscape architecture and regional planning departments. The project intentionally left elements exposed in order to use the structure itself as an educational tool.
Let’s us know what you’re seeing? Are you bidding or designing mass timber projects? We’d love to hear from you.