Results of XPS install in basement, so far
Happy Thanksgiving to everyone!
And, thanks to everyone for your help to date. During the week, we've installed the majority of the XPS in the basement; you can see a JPEG with two photos below.
In the top photo, you can see one corner of the room with XPS installed. For the wall on the left, which had a joist with a 1-in gap between it and the cinderblock wall (no rim joist), I sprayed Great Stuff Fireblock down to the bottom of the joist. I then inserted half-inch gypsum as another firebreak; there is a narrow gap between it and the cinderblock which will get filled with more GreatStuff Fireblock. Below that is the 2-in XPS, glued and mechanically attached with tapcons and fender washers at the tongue and groove seams. Cinderblocks hold the bottoms in place until the glue dries; I didn't want holes at the bottom.
In the bottom photo, you can see a closeup of the gap between the XPS and the gypsum board as fire block. Maybe I'm being overly cautious, but given the flammability of the XPS, I wanted to have this additional protection. As mentioned above, Great Stuff fireblock will go in the horizontal gap and will fill the narrow gap I left on the cinderblock wall side of the gypsum board; the gypsum board will therefore not be in contact with the cinderblock at any point and there should be a good seal at the top of the XPS.
So, before I move ahead and install the small XPS inserts between the joists, I wanted to see if anyone (worthy?) had any course correcting comments?
Also, question: if we're going to use gypsum board on the ceiling, do I need to put gypsum board on the interior side of the small XPS inserts up between the joists?
Do I need to seal any gaps at the bottom of the XPS?
Thanks for all your help!