Garage roof leaks are caused by a variety of reasons: wear from weather and the elements, wind damage, falling trees or branches, and warping from age. When a garage roof is damaged, it will begin to slowly rot, and leaks will form. At first a leak may be unnoticeable as water drips into an attic and insulation absorbs it. Eventually the insulation becomes saturated and the water seeps into the ceiling and into the garage itself.
Place a metal bucket of tar on a portable burner. Set the burner to low and slowly heat the tar.
Tie a rope around the handle of a 5-gallon bucket, then tie another rope around the handle of a bucket of warm/hot tar.
Put leather gloves, a pry bar, a hammer, a utility knife, roof felt, roofing nails, a mop and shingles into the 5-gallon bucket. If the shingles won't fit in the bucket, you'll have to hoist them onto the roof separately.
Place a ladder against the garage, near the leak. Grasp the free ends of both ropes and climb onto the roof.
Pull up both buckets. Unload the supplies out of the 5-gallon bucket.
Wedge the end of a pry bar under the damaged shingle. Pull up the shingle, then the nails, using the pry bar and/or hammer.
Cut into the existing garage roof felt with a utility knife, then pull it up by hand or with the aid of the pry bar.
Cut a section of roof felt to overlap the leak by 3 to 4 inches on all four sides with a utility knife.
Open the bucket of tar and pour the tar over the damaged area. Use a mop to spread the tar.
Press the roof felt into the wet tar, over the leak. The combination of tar and felt should begin to seal the leak. Secure the felt into place with roofing nails, using a hammer.
Spread more warm/hot tar over the felt with a mop, then nail a shingle over the roof felt with a hammer and roofing nails. The leak is now patched and sealed.
Put the supplies back in the 5-gallon bucket, close up the bucket of tar and lower both down, then climb off the roof.