In the process of tearing off all the drywall, I exposed this mess.
That was just drywalled in, with water clearly getting in past the cracked caulk on the outside. How the drywall in the sill hadn't disintegrated yet is beyond me.
I don't know how you're
supposed to install a window in brick, but I'm pretty sure this isn't the way, and wasn't the way 25+ years ago when some previous owner last remodeled this. I couldn't bear the thought of leaving that there, or even reinstalling that window, it has to go. Of course it's a non-standard size, and all the custom window makers I talked to were 4-6 weeks out, so off to Lowes I go. They had a basic window that was a couple inches too small in each direction and a bunch of lumber and I'm hoping that's all I need.
A pair of 2x4s top and bottom ended up bringing that dimension exactly where I want it. 1x4s are too thick for the sides and shims don't quite cut it, but I think I can rip some slices off a 2x4 to fill that gap and give me something to fasten it to. The window is wide of the brick cavity by a couple mm and won't quite seat, I'm gonna massage the brick in the morning with the Wheel Of Death and the window should slide right in to where the old one sat. It's thick enough that I won't have to screw with brackets like the PO did, I should be able to fasten to the framing (I think? Fingers crossed!). Then some spray foam in the gaps and fresh caulk on the outside and I'll have a window again.
Did I mention I don't know how you're supposed to install a window in brick? This whole thing is going much slower than I wanted it to and about exactly as fast as I expected.