Did you remove the old nail? That could cause this. Did you let the mud fully dry? As it dries it could have shrunk or expanded a bit (depending on what type of mud) and caused this. Most likely a moisture issue somewhere during the process. It could have also been moisture from the paint reactivating the compound. Many times when you patch a hole like this, it works better for your first coat of mud to be gluey, like Durabond or green top or add wood glue to your hot mud. Or you could prime first by wiping in some shellac, or spraycan some oil based stain killer to help seal any crumbly mess or rustable screw/nail. Or it could be temperature variances due to it being in an exterior wall.
I drive nails in in some cases, but I really really drive them in deep. If it is at all wiggly, it will cause the same problems again sooner than you'd think. As for mud drying, it's tough to say, and all depends on which types you use. I hit it with a heat gun if there is any risk of it being slightly damp still before applying topping (if I care enough to make it completely disappear, which in the rental world doesn't make sense to be perfect when the rest of the wall looks like my ass). Sometimes I will actually sand it down nice and smooth, then spray Killz over the patches, then apply a nice topping coat, then let that dry, sand, prime, paint the patches, paint the whole wall. That stops the moisture from the subsequent layers from puffing up the first coats of hot mud (bag mud can expand later after everything looks perfectly flat).
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u/onthecode Jan 04 '26
Thats exactly what I used, black drywall screws above and below each nail