When a ceiling leaks, two possible causes are an overflowing air conditioner dripping pan or a leak in the roof. In the former instance, simply draining the air conditioner's dripping pan will stop the leak. However, ceiling leaks that are a result of a hole or crack in the roof above require more attention. While a bit time consuming, repairing the source of the leak as well as the ceiling can be done by willing homeowners.
Heat a small amount of tar in a metal bucket on a portable electric burner to make it spreadable.
Put a claw hammer, a mop, roof felt, roofing nails, utility knife and shingles into another bucket.
Place a ladder against the roof and climb to the roof with the bucket of supplies. Retrieve the bucket containing the heated tar and bring it onto the roof.
Go to the source of the leak and pull up the old shingles with the claw hammer. Examine the felt underneath the shingles. If it is torn, pull it up using the claw hammer as well.
Spread the heated tar with the mop to fill in the leak. Press roof felt over the tar. Secure the felt with roofing nails and the hammer and cut off any excess with a utility knife.
Spread more tar over the felt and fasten a shingle to the roof using the hammer and roofing nails to finish patching the leak.
Place a ladder under the water-stained area and cut out the damaged portion of with a drywall saw, making an even, square-shaped cut.
Measure the size of the square with a tape measure and cut a piece of drywall equal to that size.
Fit the patch into the ceiling and fasten it to the roof trusses with drywall screws, using a screw gun.
Tape the joints around the square with drywall tape and spread joint compound over the tape using a putty knife.
Sand the joint compound once dry with fine-grit sandpaper and prime the patch with interior primer and a paint roller. Apply a coat of ceiling paint to conceal the patch and finish.