Can you put wall filler straight over exposed joint compound?
Exposing the underlying mud while scraping away old paint or caulk means you are dealing with a water-soluble surface. Applying a primer or sealer first prevents the moisture in the wall filler from dissolving the exposed mud, which stops the patch from bubbling, failing to adhere, or washing out.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
- 1Applying primer to the exposed mud before putting on the filler to prevent it from soaking up moisture.
- 2Doing a full skimcoat instead of piecemeal repairs.
- 3Using a wet sanding sponge instead of traditional sandpaper
- 4Doing a wet wipe of the walls before painting
In their words
Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.
“After a paint job (not well done) by wall mending agent (water soluble), looking to sand and apply skim coat to match with wall colour.”source ↗
“Is it advisable to sand the current mud on these walls by wet sanding sponge (with maybe 120 grit sanding sponge or cellulose sponge)?”source ↗
“Now, prefer to sand the mudding and do skim coat.”source ↗
“The layers of paint just peeled off as I was trying to scrape the paint lumps and old bumpy caulk, and exposed the mud underneath.”source ↗