u/Critical_While_4435 — reddlx

Hey everyone,

I’ve got some water damage on the drywall sill under a basement window and I’m trying to figure out the best way to fix it myself.

A couple summers ago I had a window AC unit installed, and water ended up pooling on the sill. Over time the drywall got really soft, and now there are a few holes from light pressure. It also looks like there may be a bit of mold starting.

The damaged area is about 33" x 16". I’m planning to include photos for reference.

My main questions:

Should I cut out the damaged drywall and replace it with a new piece?
Do I need to add any backing/support behind it before installing new drywall?
Is this something reasonable to DIY, or should I just get a professional to take a look?

I’m planning to move out within the next month, so I’d like to fix it properly but also not overcomplicate things.

Any advice would be appreciated!