Spiked together
Nail-laminated timber – a good way to incorporate wood in public buildings

Green construction advocates get pretty excited about high-tech engineered wood products like cross-laminated timber (CLT), but at this point such products are specialty materials that are hard to spec into a project, due to the absence of local expertise and production capacity. There is, however, another approach to mass timber construction that can be adopted much more easily. Nail-laminated timber (NLT) has actually been around forever – or at least since mass-produced nails and lumber became readily available – and with the recent push toward wood construction as a means of carbon sequestration, it is regaining favour.

One example is the new East Hants Aquatic Centre, a $19 million project currently under construction in Elmsdale, N.S., led by Bird Construction. Patrick Crabbe, brand development manager with the company, says nearby Elmsdale Lumber provided warehouse space as a temporary shop where NLT panels were manufactured this winter by workers with Celtic Construction, which is a division of Bird. About 85,000 board feet of the mill’s premium lumber was used in the panels.

No glue is used in the process; lumber is simply stacked in a jig and fastened with nails, at spacings that depend on the span of the panel. “There are many engineering factors. It also depends on the thickness, and the length of the nail you’re using. In this case, we’re using 2”x4” 12-foot, just your standard Number 2 and better, like for house construction, and we’re nailing at 8-inch intervals,” says Crabbe.

“This is a product that has been around for the last century, and it exists in some public infrastructure throughout all of Atlantic Canada. It has just recently had a resurgence now that wood is kind of at the forefront of construction, and it’s now being integrated as a prescriptive solution, and to code, and being realized as a carbon benefit.”

NLT panels may be used in roof, floor, or wall applications. For the Aquatic Centre, they will be used in the roof over the 25-metre pool. “They will span in between steel purlins, so it acts as a structural member, but also has the architectural finish,” says Crabbe, noting that the panels will not be treated with paint or finish of any kind.

“Wood is perfect in a high-humidity environment, to a certain extent,” he says. “It can’t really exceed about 80 percent relative humidity, but other than that – it doesn’t condense like steel does with changes in temperature. You know, when you have condensation on steel and you have water pooling, then you have corrosion, and you could even have contamination in the pool if the drops are dripping into the pool itself. So it works really well above arenas as well, because that’s another area where you could have temperature fluctuations, and a lot of the time those droplets will drop on the ice and create little bumps, and that can make it difficult for players.”

Crabbe was formerly employed with Atlantic WoodWORKS!, a program of the Maritime Lumber Bureau aimed at expanding the use of regionally produced wood products in non-residential and multi-family construction. In that capacity, he had addressed the Municipality of East Hants a few years ago, talking up NLT as one way of using locally-produced sustainable building materials. Municipal staff were receptive, and Crabbe ended up being involved in bringing the idea to fruition.

“We’re just really happy to see it in this high-profile project, to hopefully influence government in more public projects in the future, as well as private ones,” he says. “I think it’s important to really pound home the point that in our public buildings, in government buildings, local products should be favoured. This is a perfect type of system for over a school gym, or the atrium of a school. It really does suit that well, because it does not require massive setup or capital costs, and it’s a cost-effective solution too. So it would be great to see the provinces really take a look at this seriously, because they’re the biggest client, and until they really start specifying stuff in buildings, it’s going to continue to be an uphill battle.” DL