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).
Best Answer
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).
Possibly related Q mentioning anti-mold paint: How can I paint over mold to prevent it from coming back again?
Might be worth considering, when XPS could act as a vapor retarder / air barrier when taped