Unpacking the Jigsaw Puzzle Approach to Prefab Construction

Vienna House is a great example of how prefabricated construction techniques can be used to quickly and cost-effectively assemble an exceptionally energy-efficient building. But how does it all work?

Our latest video explains the process at a high level, but we wanted to also share this more detailed overview of the project. As we roll into the cooler weather, the Vienna House site is teeming with activity. Two of the building’s six floors are now in place and the third is well underway!

Here’s a quick low-level aerial view of the site, looking west from the east end of the project, captured on September 6, 2024.

Low-level drone footage looking west from the east end of the project site.

Several times a week, trucks loaded with prefabricated building components arrive on Stainsbury Avenue and park beneath one of the project’s two bright-red cranes. As documented in our video, a crane operator then hoists the materials off the truck and onto the job site.

From there, a team from Seagate Mass Timber works with a crane operator to again lift and lower the pieces onto their precisely planned locations on the project.

So far, two different off-site construction companies are supplying the Vienna House project with prefabricated building components:

TAG Panels, in Squamish, British Columbia, is manufacturing the exterior and interior walls. The exterior walls are fully insulated and sealed with air-barrier material for high energy efficiency performance.

Kalesnikoff Mass Timber, just north of Castlegar, British Columbia, is manufacturing the cross-laminated timber (CLT) floor and ceiling sections. CLTs are essentially super-strong “slabs” of wood, made by laminating together layers of smaller boards under immense pressure.

Kindred Construction and Seagate are assembling Vienna House with a carefully choreographed sequence of alternating wall and ceiling panels.

First, the crew brings in a floor’s worth of prefabricated exterior wall sections, braces them in place, then fastens them together. The company also supplies prefabricated interior walls, which are placed within the exterior walls to build out each individual apartment.

A worker on a stepladder uses a nail gun to attach specialized tie plates that connect neighbouring exterior wall panels. — A worker uses a nail gun to attach the lateral tie plates that connect adjoining exterior wall panels.

A team member uses a laser level digital receiver to check and adjust a sill plate. Workers levelled all the plates before the crane lowered the walls onto them.

The angled temporary bracing on the right is holding the prefabricated exterior walls in place until the cross laminated timber floors and walls arrive.

Once all the framing for a given floor is complete, the crew takes delivery of a set of floor/ceiling panels from Kalesnikoff Mass Timber, cranes them into place, and fastens them down. The CLTs arrive on site with pre-cut holes where plumbing, ventilation, and electrical services will run between floors.

A cross-laminated timber (CLT) section is craned on to the project site.
Workers use the dangling ropes—called taglines—to stabilize the component while it is in flight, and guide it into place.

Workers guide a CLT into position on the northeast corner of the project.

This image clearly reveals the five layers of wood—each is referred to as a “ply“—in Vienna House CLTs. CLTs are generally available in three, five, or seven-ply configurations.

This worker checks a detail where a CLT floor panel has topped out the first floor at a “party wall”—a double interior wall dividing neighbouring apartments. The gap between the two walls will help with soundproofing. Though typically drywalled, the CLT ceilings at Vienna House will be left exposed in the main living areas.

The Vienna House assembly will continue in this manner, coming together like a giant jigsaw puzzle, for each of the six floors of the building. Then prefabricated aluminum balconies will begin arriving on the site; Kindred’s cranes will lift them and workers will maneuver them onto pre-installed supports on the building’s south and west facades.

Once that work is complete, roofing will begin and interior work will also get underway, including mechanicals, electrical, and plumbing.

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