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I'm going to finish one corner of my basement and want to insulate the two adjoining exterior walls so that the space will stay warm in the winter. The wall was painted a few years ago and the paint is peeling in places. I plan to scrape these sections to ensure the adhesive sticks well when I add XPS insulation boards. My intent is that the XPS insulation act as a vapor barrier.

Is it necessary to scrape away all of the paint, or will removing the loose flakes be sufficient?

After the insulation I'll add a stud wall right against the XPS, with batt insulation in between the studs, and drywall over that.

The home is 100 years old but a poured foundation was added at a later date. It is a shallow basement with no drains. We've had a wet winter but this corner has stayed dry (some seepage in another area due to an ice dam outside which I remedied).

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  • Is glue/adhesive the only thing that will hold the insulation up? And then will drywall or anything else be attached on top of the insulation, and how?
    – Xen2050
    Mar 2, 2019 at 3:47
  • @Xen2050 edited to add that detail.
    – LShaver
    Mar 2, 2019 at 4:18
  • How do you plan to get rid of the water that penetrates the walls?
    – Harper - Reinstate Monica
    Mar 2, 2019 at 6:26
  • @Harper I can't find the reference now, but my understanding is that with a sufficient vapor barrier, the moisture will stay in the concrete where it can do no harm. We bought the house in the winter -- in spring I plan to do the required outside work to prevent flowing water at the foundation.
    – LShaver
    Mar 7, 2019 at 2:18
  • In that case I would hold off on what you're doing until you have a wet spring (you can help it along with a hose :) so you can see how water behaves. Also, to get a real sense of water ingress, you have to cover the walls/floor with visqueen, the result will be quite different!
    – Harper - Reinstate Monica
    Mar 7, 2019 at 3:19

1 Answer 1

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It sounds like the adhesive only has to hold long enough to build the stud wall, and from then on the wall will be essentially holding the XPS in place. Similar to how batt insulation isn't attached and is just essentially sitting in between studs.

So I wouldn't spend more than a few minutes removing paint.

However, if the paint could later turn into "mold food" in your sometimes damp basement, then you might want to spend more time and remove it more thoroughly (unless it's already an anti-mold paint).

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  • Thanks -- yes, my intent is that the XPS will act as the vapor barrier.
    – LShaver
    Mar 2, 2019 at 4:49
  • That might put the vapor barrier in between the foam & batt insulation, that might not be a good idea for a regular vapor barrier, but this answer (near the bottom) did just about the same thing, but without the batt insulation in between studs, and says foam's a little different & is OK in a basement
    – Xen2050
    Mar 2, 2019 at 7:35

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