Six Storeys



Six Storeys

By Michelle Ervin – from CondoBusiness:


The race is on to erect the first six-storey wood structure in each of Ontario’s municipalities.

Before 2015, the province’s building code limited this type of construction to four storeys in height. Now, developers are moving quickly to unlock its potential to save time and money, and ultimately deliver new, more affordable housing options.

Northland Properties was first out of the gate with a building permit from the City of Hamilton for a 209-unit Sandman Hotel featuring an indoor pool and two restaurants. Excavation and foundation work on the project began in the spring.

Location, location, location

Developers may be eager to take advantage of six-storey wood construction, but virtually everyone involved in planning, approving and erecting these structures faces a learning curve. Even companies that have experience in B.C., which began allowing six-storey wood construction in 2009, must adapt to Ontario’s unique building code requirements.

“You can’t simply pick up a B.C. architectural drawing and engineering drawing and bring it to Ontario,” as Joe Vaccaro, CEO of the Ontario Homebuilders Association (OHBA), puts it.

At least a dozen of the OHBA’s member companies are reviewing technical plans for building code compliance and looking at their land holdings to determine where to locate these structures, he says. Generally speaking, six-storey wood buildings are geared toward transit corridors.

“The six-storey wood structure is community-friendly enough that it won’t disrupt the existing community, but there’s enough intensification there that it supports transit ridership,” Vaccaro explains.

He points to Waterloo Region, which is building an LRT (light rapid transit) system, and Burlington, which is built out and will have to start building up as it continues to intensify, as areas of interest.

New opportunities

Over in Toronto, six-storey wood construction is viewed as a way to drive some of the mid-rise development city planners are actively promoting. The push began with its 2010 Avenues and Mid-Rise Buildings Study, says Lorna Day, director, Scarborough Community Planning.

The city aimed to add certainty to the application process with mid-rise building performance standards for everything from height and setbacks to at-grade uses and vehicle access.

After five years of monitoring, Day reports that the performance standards have been effective, with 217 applications received and 61 applications either approved or built. But her analysis sheds light on untapped mid-rise opportunities, finding that corner sites are over- represented.

“So what’s going to be left now are the smaller, mid-block sites,” she says. “Wood-frame is probably more suited to more constrained sites, because you can presumably get in and out in terms of your construction more easily and more quickly.”

Without the recent building code change, those sites might have remained undeveloped, adds Day, who is hoping to see uptake on the new material option for six-storey structures.

“I was doing this consultation when the building code changed and a number of the developers I spoke with were very enthusiastic and really wanted to be the first one on the block doing wood frame.”

Lessons from B.C. and Sweden

Although some developers are enthusiastic about six-storey wood construction, Bryan Tuckey, president and CEO of the Building Industry and Land Development Association (BILD), says that the industry is still working through how to use the technology.

BILD groups have traveled to B.C., which now has more than 150 five- and six-storey wood buildings, and Växjö, Sweden, a world-leading municipality in wood buildings, to glean general lessons.

“What we found in Sweden is, as they built more buildings, the costs began to reduce when they got better at it,” says Tuckey.

Some of the cost savings came from the faster construction times made possible by wood construction.

“These companies were building homes that they put up a floor a week,” says Tuckey. “The components for the floor would come on a Monday and the floor would be finished by Friday.”

Getting to that point took several generations of wood construction. As developers set about building the first generation of this building type up to six storeys in their home province, they’re starting from scratch. But guidelines are coming, with Ontario Wood WORKS! due to launch a Mid-Rise Wood-Frame Construction handbook at a symposium in Vaughan next month.

(The province is also expected to release fire-safety guidelines for the construction of five- and six-storey wood buildings soon.)

Methods and materials

Steven Street, technical director at Ontario Wood WORKS!, has already consulted for a number of development teams. He predicts six-storey wood construction will rev up in the next six months to a year.

“There is a time drag; the code just doesn’t change and all of a sudden there’s buildings springing up everywhere,” notes Street. “It was 12 months before B.C. really got going.”

Development teams essentially have two ways to construct six-storey wood buildings, he says. Traditional “stick” construction involves carpenters working from plans to erect the structure on site; new prefabricated solutions involve bringing factory-built panels to the site by truck and using a crane to put them in place.

Street cites the advantages of prefabricated solutions as moisture and quality control, as well as speed of on-site assembly.

“It will have a significant shortening of the framing stage, for sure, because you’re basically erecting a giant Lego set,” he says.

Street expects to see development teams largely use spruce-pine-fir (SPF) for framing with a possible preference for engineered wood products for floor framing materials, wall plate material and for the assembly of tall walls and beams. Others are investigating cross-laminated timber, a solid floor slab made from wood; others still are looking at hybrid solutions that combine wood and concrete hollow core slab.

Design freedom

Paul Stevens, principal of ZAS Architects, is working with a client who is now weighing different framing systems for a mid-rise project. He’s urging the client to go with wood.

Concrete and steel systems lend well to large projects, as they demand repetition to make them cost-effective, Stevens offers by way of comparison. Because wood comes in smaller pieces, it allows for greater design freedom.

“We have an ability to customize them a little bit more and add a greater variety of unit types as a result of that on the inside,” he says. “And on the outside, there’s even greater flexibility in what you can do in terms of roo ines, balconies and setbacks, stepbacks and so on and so forth.”

Stevens believes six-storey wood construction will fit well into Ontario cities as a sort of missing, medium- sized piece between townhouses and high-density towers. And he believes that the new housing type will sell — but the industry needs to deliver strong product from the get-go.

“It’s important that the quality of that work be of the highest caliber, so that the general public see that not only is it affordable, but there’s something that’s unique in terms the unit types, the look, the location,” he said. “All of these things are very important to do well the first time.”

Engineering challenges

Doing six-storey wood construction well requires a lot of work upfront. David Moses, principal of Moses Structural Engineers, likes to get everyone around the design table at the beginning, including code consultants, re engineers and city of cials.

The strategy for six-storey wood buildings necessarily diverges from that for its three and four-storey cousins, he says, which are built under the prescriptive Part 9 of the Ontario Building Code. That means they have to be completely engineered without rules of thumb. Some of the key challenges are acoustical performance, re separations and wood shrinkage.

“The height of building will go down somewhere around three- eighths of an inch per floor,” Moses explains. “So if you add that up over six floors, it’s well over an inch that the roof is coming down over first few months of the life of the building because the wood is drying out.”

One of the areas where the wood shrinkage would be noticeable is at doors opening out to stairwells, he says, which must be made from non-combustible material (concrete) under the Ontario Building Code and so will maintain their height. The shrinkage either needs to be minimized or accommodated.

None of the engineering challenges is insurmountable, Moses adds, and once the housing type is nished, it’s largely indistinguishable from concrete construction.

A Toronto proposal

Moses is working with architect Roland Rom Colthoff, principal at RAW, on a six-storey wood-structure development slated for 45 Dovercourt Rd., an offshoot of Toronto’s trendy West Queen West strip. Curated Properties has dubbed the project CABIN, marketing the collection of 25, two-storey townhouses as Muskoka-inspired living in the city.

Colthoff had just saved the boutique residential developer money by recommending the use of wood for a four-storey collection of townhouses up the road, so the use of wood on this project was an easy sell. Though wood construction doesn’t change the way the architect approaches the design process, it does impose certain restrictions when it comes time to determine how to bring that vision to life.

“With concrete, because it’s a monolithic, poured-in-place structure relying on reinforcing rods running in all kinds of directions, you’re actually much more free to create cantilevers, to create asymmetric or eccentric structures,” he says. “With wood, because of the earthquake loading, it’s much more important to have things line up top to bottom to get continuity of the membranes in the building.”

Colthoff gave CABIN sculptural form by cantilevering the upper bedrooms floors over the lower living room floors, which does double duty as outdoor terrace space for the units above. A steel skeleton running north-south through the building will ensure the structure’s lateral stability.

The proposed project is currently going through rezoning at the City of Toronto, with Curated Properties planning for a fall launch. The goal, says Colthoff, is to secure a building permit in the spring. Construction is projected to take roughly 16 months.

Whether CABIN could become Toronto’s first six-storey wood building is unclear at this point. Since the Northland Properties hotel project slated for Hamilton pulled the first building permit, it is likely to be the first of these structures constructed in the province.

As developers move along the learning curve at different paces, and some wait in the wings to see how the new housing type fares, the race to build each municipality’s first six-storey wood building remains wide open in many Ontario cities.