How to Replace a Sheet of Drywall. It's often easier to replace a large amount of damage to an area of drywall than it is to "patch." Here's how to get it done quickly and easily.
Remove any baseboard trim from the wall you're going to repair. (If the wall has crown molding leave it in place. Crown molding is usually attached much more firmly than baseboard and difficult to remove without damage. It is easier to make a horizontal cut about 6 inches below it from stud to stud.)
Locate the nearest wall studs on each side of the damaged area. (See "How to Locate Wall Studs.") Any repair work over a large area must span from stud to stud in order to give the drywall the proper strength and stability.
Mark the studs from the ceiling all the way to the floor with a straightedge. (You will need to find the approximate center of the studs so that you have good support under both the new and the old drywall.)
Cut along these lines with a utility knife. It will take several passes to cut all the way through to the studs below.
Remove the drywall inside your cuts. Remove any old nails or screws in this area and clean up ragged edges, using the cut lines you made on the wall as a guide.
Cut a new piece of drywall to the dimensions of the piece just removed. It can actually be slightly smaller - 1/16 to 1/18 of an inch in width and height - to make it easier to refit. You'll close the small gaps with tape and mud.
Attach the new piece of drywall to the studs with nails or screws spaced approximately every 8 inches.
Tape and mud the joints. (See "How to Apply Joint Tape.")