Bay Leveling

Removing floor boards

The pre-subfloor leveling isn’t quite done yet, and the bay window on the front of the house brought its own set of challenges. For starters, the joist running across the very front of the house (and across the widest part of the bay) is embedded in brick, meaning I couldn’t jack it up the way I did most of the others. There’s also a gap of nearly two feet between that joist and the joist in the center of the bay, which is considerably wider than the 16″ that most of the joists are spaced. Finally, the old floorboards rested directly on top of the brick foundation and extended under the bay walls, whereas in most of the balloon-framed house, it only reaches the edge of the wall.

Level? ish?

When we rebuilt the bay windows, I noticed the floorboard situation and debated replacing it then, but between doing only one window at a time and the corner studs not being replaced, I decided against it. That meant the first step was to use an oscillating multi tool to cut the floorboards back at the wall edge. Then I glued shims to the top of the existing joists and added some blocking joists to better support the gap between joists.

Shimmed, Reinforced, Re-mortared

Questions sprang to mind of how to control air and vapor infiltration through the foundation and through the gaps in the wood, and how to insulate the bay properly. We’ll be spray-foaming the cavities in the wall, and on the sides of the house we’ll spray foam the top of the foundation wall to air seal it to the wood, but here that isn’t an option because the brick comes all the way up to the underside of the floor. The exterior rigid insulation doesn’t help either because it doesn’t extend over the brick.

Front shim and spray foam

I decided to attach an inch-thick shim to the inside edge of the brick wall (on top of sill gasket) that will support the subfloor. In front of the shim, and along the top of the brick on the sides of the bay, we’ll fill with spray foam. I’ll also glue the outside edges of the subfloor to the framing to further seal everything. Hopefully that will be sufficient, since it will be damn difficult to do anything about it with the subfloor in place.

When I initially test fit the shim I realized that the brick was —perhaps unsurprisingly— uneven. In order to properly support the shim I had to mix up some mortar and straighten out the top of the foundation. That meant waiting a couple of days for the mortar to set up, but then I was able to drill some holes into the brick and secure the shim with Tapcon screws.

First piece of OSB

I went through a few cans of “big gap” Great Stuff, since the real spray foam won’t be for a bit. Fortunately it’s so cold that it cures slowly, giving me ample time to even it out. I got the first of three pieces of OSB down that go into the bay. I took my time and worked out the dimensions exactly, accounting for all of the unevenness of the studs. There’s still a small gap along the edge of the angle, but I’ll fill that with caulk. The important part is it’s secure, level, and insulated. I’m considering whether I should exchange the one piece of blocking in the center with two, since that would be a more proper 16″ spacing, plus there’s a good chance I’ll wind up putting an electrical outlet in the floor there. One of the reasons to use screws instead of nails is you can change your mind without too much hassle.