Mackay Laneway House: Ground floor steel complete

The ground floor steel for Mackay Laneway House was completed and inspected last week. Framing of the ground floor is now underway. As you can tell from the above photo, the house is going to essentially float above the ground on top of 8 helical piers. This was the foundation solution we landed on because of a nearby tree (not pictured) that is creating a Tree Protection Zone (TPZ) for a good chunk of the house’s footprint. Because of this, a basement or slab-on-grade construction were not possible.

Working with Urban Forestry at the City of Toronto, the team came up with this helical pier solution as a way to avoid impacting the roots of the tree. (Approvals process took about 3 months.) An arborist was on site while each pier was installed and each location was hand-dug or airspaded to ensure that there were no major roots in place. One of the benefits of going with steel is that it ensured there was some flexibility should any of the piers need to be relocated as a result of site conditions. That didn’t end up being the case, though, and the piers were installed without any real hiccups.

One of the challenges of going with this floating house approach is that it now means the services (which run from the main/existing house) will exist above-grade right before they enter the laneway house’s mechanical room. This includes water, sanitary, and gas. (It also means that the house’s mechanical room had to be located outside of the TPZ.) This is a problem in Toronto’s climate and so, in addition to being insulated, the services will also be heat traced. And just to be extra cautious, a backup generator is going to be installed in case the power goes out in the dead of winter.

As a rule, we think it’s always better to have passive rather than active systems whenever possible. That is, you ideally want systems in place that don’t require power and aren’t liable to breakdown. Unfortunately, we had to break that general rule of thumb in this situation. A pump-up ejector also had to be installed within the existing house in order to deal with some of the drain elevations. Still, we think we’ve arrived at a pretty clean solution given the circumstances. Like most construction projects, a lot of the uncertainty can happen below-grade.

And now, it’s time to frame.