Why does compound crack when drying?

Question

Im trying to fix my bathroom wall, its a part where there used to be mold and remove the mold and put new compound over it and it keeps cracking any reasons why? or am i doing something wrong??

Answer 1

I agree with all the above.  But to put it on thick buy "setting type" compound.  This comes dry and you mix it with water just prior to use.   It cures by hydration, just like concrete, and does not shrink (and crack).

Answer 2

without knowing just what you are trying to repair, sounds like you might be putting it on too thick, or trying to span too big a gap. should go on in multiple thin coats, and will only span a gap of at most 1/8". use drywall seam tape for larger gaps: lay down a thin bedcoat, apply the tape into it, and cover with another thin layer of mud. three coats are usual, feather out into surrounding areas.

Hope that helps.

Answer 3

Drywall compound is meant to be applied in thin coats. When it dries, the moisture evaporates and when it is applied too thick, the outside dries faster than the inside and causes cracks.

Answer 4

Could be applying it too heavily.

Thinner , well dried , coats sanded in between  will work better.

Also possible that drywall in the area has softened or the paper surface has separated.

Might also need a few screws to secure it..

Old trick is to work a little shellac into the dry or ready mixed spackle & or  use a piece of brown paper bag to cover the area & skim w/ drywall "mud" as though " taping".

Best regards