I took last week off, and Caleb and I made rapid progress. We finished framing, sheathed the walls and roof in plywood, got most of the tar paper up, insulated the roof and one wall, and installed the metal roof. Whew!
I used pressure-treated lumber to frame the shower area. It is regular lumber treated with stuff that bugs and fungus don’t like. Why do this, you ask? The foam insulation I plan to install on the outside of the house is vapor-impermeable polyisocyanurate (building science nerd-speak for fancy foam board). Because the foam board doesn’t allow any moisture to pass to the outside, the building has to dry toward the interior. Since the interior is a humid shower, I wanted some insurance against rot and termites. We didn’t use plywood around the shower, either. Confused? Good. Just know it’s awesomely over-thought.
This is the roof deck shortly before we finished nailing on the plywood. We tried installing the plywood on the roof before installing the plywood on the walls, but the structure was very wobbly. The plywood really provides incredible strength. We were using a nail gun that shot smaller nails than are in the code book, so we had to use extra nails. There are thousands of nails in this little room!
This is what the room looked like when we called for inspection. The inspector needed to see that all the plywood was nailed on properly and in the right locations. We mostly passed. Which is to say, we slightly didn’t pass. One panel didn’t provide enough shear bracing for the west wall (it’s the one right in front of you, to the left). Long story short, there was some confusion about what I thought I permitted and what was actually allowed. But the inspector was cool and said we could continue, we just needed to show that we had provided adequate shear bracing before we put up drywall.
I was glad to move on to roofing. After shooting thousands of nails I was really tired of plywood. The roof is pretty unusual: the insulation is on top of the roof deck. Four and a half inches of polyiso foam over felt over plywood. And steel on top of all that.
The thick foam provides a little more insulation value than is required by code in our area. There will be another six inches of rock wool insulation between the rafters below, making a fairly superinsulated roof. Cozy!
We installed the galvalume roof ourselves. A local metal roof manufacturer measures the roof deck and fabricates all the pieces, then delivers them. They provide some basic instructions and loan you a few necessary tools. Installing the roof was pretty easy. There was some cursing over the waste vent pipe flashing, though.
We finished the roof as it was getting dark, so no pic yet. But it’s purdy.