Find the Source of the Leak

• 1). Climb into your attic to search for the leak. Leaks can form when roofing shingles are damaged. If there is a leak inside your house or a mildew spot on the ceiling, start with the assumption that the leak is directly above this.
  
  
• 2). Shine your flashlight on the underside of the roof and look for wet spots. Also look for light shining through or obvious signs of exposure to water. Work your way toward the peak of the roof, since water (and leaks) flow downhill.
  
  
• 3). Climb the ladder onto the roof and search for missing shingles, missing nails or nails that appear to have worked themselves loose. Depending on how steep your roof is, you may need to get down on your knees and crawl. Check any valleys and along metal flashings. Flashings may be around vents, chimneys and in roof valleys. These provide extra weatherization but are prone to damage in adverse weather. Leaks can also occur during periods of heavy rain and wind. The water can be blown sideways and get under the shingles. These shingles may appear slightly bubbled.
  
  

Fix the Leak

• 1). Replace a missing or damaged shingle by sliding a new shingle where the old one used to be and securing it with three roofing nails. Place the nails at the top of the shingle so that the shingle above it covers the nails. This can be tricky and may require trimming the top of the shingle so that it can fit under the one above it.
  
  
• 2). Spread the roofing cement around suspected leaks in valleys or around flashings. Coat the area liberally. Use the putty knife to smooth out the cement.
  
  
• 3). Apply roofing cement under any shingles that appear warped. Carefully lift up the end of the nailed-down shingle, spread a small amount of cement under it with the putty knife, and push the shingle down. Stand on it to make sure a tight bond forms.