Q. I’m getting ready to build a large room addition that needs a beam to support the floor joists. I’ve been told that a wood beam will work, but I’ve always seen steel I-beams in other houses.

A new kind of construction with a not-so-new material is taking off in the U.S. Mass timber can replace steel and concrete in large buildings and proponents say it's greener and faster to build with.

Cross laminated timber can be used in high-rise structures, as a replacement for materials with a high carbon footprint. And it also locks carbon into buildings for decades.

Canada’s national building code now approves laminated wood-beam buildings of up to 12 storeys. Smaller mass timber projects include two new firefighting stations in Welland, Ont.

But the floors above feature manufactured wood columns and beams braced by steel and as well as a flooring system that includes laminated 2-by-8-foot wood beams sandwiched with a layer of concrete.

According to the firm, they’re the first two brick-and-beam buildings—brick front over a wooden structure—to rise in the city in at least 100 years. An interior rendering for 320 Wythe Avenue.