Results of XPS install in basement, so far

tigerninetyNovember 23, 2012


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!


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And a Happy Thanksgiving to you! (We celebrated ours--the first and the best--more than six weeks ago.)

Looks good. Just a couple of suggestions.

You can press the bottom of XPS boards tight to the wall with the baseplate. Shim if necessary.

As I mentioned earlier, the finished basement would look much better if you boxed in the area with the two electrical panels. You don't need anything elaborate. Just a 2"x6" box with a couple of plywood doors. And you might want to replace that top hinged single pane window with a modern set of aluminum or vinyl sliders with dual panes. I can get a custom made one here for less than $100.

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?

Here's the Fairfax Virginia information I posted on the other thread.

You can use drywall or the other materials mentioned in the information. The point is to create a discontinuity between the stud spaces in the wall and the spaces between the floor joists above, which includes the rim joist area you're insulating.

    Bookmark   November 23, 2012 at 10:38PM
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