Re: How do you repair interior wall by window properly
First step is to fix the window or else that great patch job you just did will fall apart just as this has done. Also, is the window actually leaking or is it a sweating issue?
Once the window is fixed, then you'll want to scr-ape off the flaking bits and determine if the drywall is sound or needs replacement as well. If it is crumbling or the paper is significantly damaged, cut out the damage and replace it.
Apply fiber tape to all joints, even the metal corner bead where it meets the drywall. Apply drywall joint compound (not spackle) in thin even layers until you've built it up to match the existing wall and it is smooth. The more work you put into getting the compound even and smooth during application, the less sanding and dust you're going to have when it's dry and ready for another layer. Typically patches can be floated out in 3 layers, a novice may need more, just depends on your skill with a drywall knife.
Once the patch is complete, you apply two coats of primer, Zinsser Bull's Eye 123 (blue label) is a good choice. After the primer, apply two coats of paint. To match the rest of the wall, the whole wall will need to be painted to blend in the fresh, new paint.
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