In the five years since B.C. increased the height limit for wood-frame buildings, new structures have been popping up all over the province. Now lumber’s biggest advocates are predicting they can build higher than they ever expected.

Since 2009, when the province raised the limit for wood-frame buildings to six storeys from four, 202 new five- and six-storey buildings have been approved, including 58 that are already complete.

Among the finished structures are the two buildings at Sail, a six-storey condo development at the University of B.C., the five-storey Library Square development in Kamloops and the five-storey Riverport Flats rental development in Richmond. The new projects come as the province pushes to revitalize the forestry industry and find new markets for wood projects.

But builders can go even higher than six storeys if they use mass timber — also known as massive timber. Unlike the light-frame or stud construction used to build houses and low-rises, mass timber is made by bonding together thin layers of wood to create a material that is much stronger and more fire-resistant than lumber.

To get approval for mass timber structures higher than six storeys, developers must prove that the building will be just as safe as if it were built with concrete and steel.

Vancouver architect Michael Green has been one of the world’s strongest voices in support of tall wood buildings. He grabbed attention with the audacious claim that mass timber construction can be used for structures as tall as 30 storeys, but he now believes he wasn’t shooting high enough.

“I’ve been saying 30 for a long, long, long time … but I picked the number 30 out of the air,” he said.

“I am quite convinced that we’re going to get to 40, we’re going to get to 45. I don’t know where we’re going to end.”

He believes that as these buildings push higher and higher into the sky, concrete and steel will be incorporated into the structure in an attempt to get the most out of each material.

Green’s firm designed the Wood Innovation and Design Centre in Prince George, a seven-storey mass timber building at the University of Northern B.C. that was recently completed and should be cleared for occupancy in a few days.

Now he’s got his sights on much bigger things. Although he couldn’t give any details, he said his firm is now working on a “very large timber project” in Minneapolis with a large developer that has traditionally built skyscrapers.

And later this week, Green will submit his proposal for a groundbreaking new 16-18 storey wood student residence building at UBC.

“It will absolutely be the world’s tallest. It’s absolutely one of the most important wood projects to be announced in the last, well, ever,” he said.

“It’s a huge step for UBC and even if I don’t get the project, I’m tremendously honoured that everybody has embraced the idea to this extent.”

Green talks about wood with reverence, describing the beauty of lumber and the human desire to be surrounded by natural materials.

But he has practical reasons for advocating for wood as well.

“Sixteen per cent of the world’s fossil fuels go into making steel and concrete,” Green said. “How can we build big buildings in wood that sequesters carbon, that’s very low energy, that we can grow more of, that’s a renewable resource?”

On Monday, forest research organization FPInnovations launched a technical guide to help builders become familiar with wood as a construction material. It includes peer-reviewed research on building techniques.

Natural Resources Canada, which funded the creation of the guide, said in a news release Monday that “increasing the number of tall wood buildings is a priority for economic growth opportunity.”

Conroy Lum, FPInnovations’ research leader for structural performance in advanced building systems, said that incorporating wood will be key as the world’s population grows and becomes even more concentrated in urban areas.

“There’s going to be greater demand for buildings, both to provide service as well as to house people,” Lum said.

“If we can we do it with a material that allows us to deal with minimal impact to the environment, that would be preferred.”

He believes that Canada’s building codes are in need of a reboot to reflect the fact that fire-prevention science has advanced significantly in recent decades.

“Let’s start from fresh. Let’s look at the materials closely. Let’s see how can we go about building and designing with wood that will help us mitigate the risk,” he said.

blindsay@vancouversun.com