Q: Can I use a low luster polyurethane to coat my interior wood floor, that was recently painted with a satin latex porch and floor enamel?
A: I honestly don’t know, but have serious reservations about it. I am sure of one thing. If you are to have any hope of gaining adhesion, the paint will have to be buffed or scratched, just like applying multiple coats of polyurethane, and that is likely to make the paint job look terrible.
Polyurethane over a peeling painted floor
Q imported from our old site, Face Lift Floors: We just took the carpet up from our staircase and refinished it using polyurethane on the treads and white latex paint on the risers. It looks great, but the latex paint seems kind of soft, and peels away quite easily.
Can we top it with a coat of clear poly or varnish to harden it, or should we leave well enough alone?
My fear is that the white paint might yellow if we put something on top of it.
A: I am not a painter, but I do know quite a bit about coatings. One or both situations are likely affecting the paint on the risers. If you did not at least lightly sand the risers, the paint may not have made a bond with whatever finish was on them. Also, if there was any sort of wax type of finish used on the staircase and risers, you won’t get a bond. This applies to polyurethane also.
I definitely would not apply a coat of polyurethane to the white paint. For one, as you have noted, it won’t stay white and will yellow over time. Also, applying another coating on top of one that is not sound will not make the undercoat stick to what is behind it. Put another way, if the existing finish coat is failing, every coat applied above it will fail also.
Sorry for the bad news. I would inquire of a paint professional or a paint store, but I suspect you will have to sand off all the loose paint first. Find out if there is a primer that will bond to just about anything and apply it first to act as a sort of blocker. Or perhaps shellac will work.
Original / moved link https://faceliftfloors.com/q-and-a/softpeels.php