fill in the crack between your wall and the replacement piece of drywall with joint compound. When dry, sand the drywall compound smooth. Put a second coat of drywall joint compound on the wall, feathering it out as you go. When dry, sand the drywall compound smooth. Put a coat of primer on it, and then paint it to match. Then charge your roommate a hefty fee for fixing his damage. How much does it cost to do baseboard and drywall repair? The baseboard is about 3 inches high and about 6 feet long. The drywall from behind it has been cut out, so I need to replace that drywall and install the baseboard (I can paint the baseboard myself). How much would it cost to replace/repair this peculiar strip of drywall and baseboard? At most home improvement stores around the country you can either buy pieces of a standard sheet of drywall cut to a size you can handle, or if you asked, they might even cut the piece you need for you to your dimensions. That way all you would need would be some drywall mud, (plaster patch material), a couple of putty knives and some sand paper and you're ready to do this yourself. Actually if the baseboard comes above the opening where you're going to put the drywall, it will cover the crack when you put it up and you wouldn't even have to do the patching, just install the drywall and the trim, paint and