Why does nobody warn you that drywall mud shrinks so much

Ngl I was patching a hole in my living room wall last weekend and I swear it looked perfect after the first coat. Then I came back the next morning and there was a visible dip in the middle like I barely put anything there. I had to do three coats total on a hole that was maybe 6 inches across. It took me like 4 hours waiting for each layer to dry plus sanding in between. Has anyone else found a way to guess how much extra mud you need on the first pass to avoid doing three rounds?

3 comments

3 Comments

aaronroberts1d ago

Guy probably didn't use enough mud.

david_palmer20h ago

Oh man, I gotta jump in here and say something real quick. The tip about overfilling is good advice, but that quarter inch thing is a bit much for most patches. In my experience, piling it up that high just means you're gonna be sanding forever and probably make a bigger mess than you started with. I'd say go for maybe an eighth of an inch above the surface, tops, especially if you're using the setting-type mud like the comment mentioned. Your mileage may vary of course, but I've found that patience with thin coats saves more time than trying to engineer the perfect first pass.

garcia.cameron1d ago

Not enough mud is definitely part of it, but there's more. You gotta think about how drywall mud is basically water with some glue and dust in it. That water evaporates out, so the mud shrinks like wet clay does. The trick I learned is to deliberately overfill the patch on your first pass. Like pile it up a quarter inch higher than the wall surface. Then when it dries, it shrinks right down to flat. But don't go too nuts with it or else you're sanding forever. Also using hot mud (the kind that sets chemically) shrinks way less than the regular all-purpose stuff.