How to Repair Water Spots on the Ceiling

Mark out a square border around the damaged area with a pencil and square. Mark it so the two vertical sides of the square are positioned along the center of the ceiling joists on both sides of the damage. (Note: If the damage isn't extensive enough for you to see or feel where the joists are, pull down enough of the damaged drywall until you can.)

Use your jigsaw to cut out the damaged area, exposing half the widths of the two joists on either side. If the joists are each 1 1/2 inches wide, expose 3/4 inch of each joist.

Measure the square hole. Transfer the dimensions to a piece of drywall. Cut out the piece by setting your square alongside the mark, running your razor knife alongside the square to score the piece, then bending the piece at the score until it breaks.

Lift the drywall piece into the cutout hole. Drive drywall screws along the vertical edges of the piece, into the joists, sinking a screw every 6 inches. (Note: If the damaged area spans several joists, mark the locations of the joists on the wall before you hang the piece, then drive additional screws into the drywall at each point where the joists are behind it.

Press drywall tape along the seams around the perimeter of the square patch. Spread joint compound onto the tape with a drywall knife. Get it flat and smooth.

Allow the compound to dry for four to six hours. Scrape along the surface of the dried compound with the drywall knife, knocking off the ridges and high points.

Apply a second layer of compound, spreading it flat and smooth. Let it dry. Scrape off the surface, apply a third layer and let it dry. Sand the third layer smooth with a drywall sanding pad. Repaint the ceiling.