How to find a roof leak

 Finding a roof leak in a flat roof can be extremely difficult, so we recommend that you hire a roofing contractor to find and repair a leak in this type of roof.  However, on a pitched roof, do-it-yourselfers can find the leak themselves. You may need to hire a contractor to repair the leak, but being able to tell the contractor where the leak is saves time and money. 

 The first step is to relate the area where the the leak is showing on the inside of the house to same area on the top side of the roof. Two different directions need to be determined. How far into the house and the position in the length of the house. This can be accomplished  by looking out windows and aligning the spot on the ceiling to something on the outside, such as a tree, bush or fence post. Seldom can you see out 2 windows from one area. If this is the case you will need to measure from an outside wall to the spot on the ceiling. Remember this measurement when you get on the roof and don't forget to add for overhang.  

  The leak in the roof is usually uphill from the the spot on the ceiling. Once you find the general area look for protrusions thru the roof such as chimneys, pipe flashings, valleys, solar panels. Inspect these areas thoroughly, look for loose solder joints in flashings, deteriorated rubbers on plumbing pipe flashings. Also check for broken and missing shingles. If a chimney is in this area check it for loose and missing bricks, cracked mortar joints and loose counter flashings. On a wood framed chimney check the metal cap for splits in seams and gaps in trim boards.

  If you do not find anything obvious get a flashlight and climb into the attic. If you have trouble determining the location of the problem area have a helper tap on the ceiling below. Lift up or spread  the insulation and look for wet spots or a stains. If found, follow the stain or wet spots up to the roof. Once you have found the end of the trail drive a nail thru the roof. Get back on the roof and find the nail, seldom will this be where the roof is actually leaking.  Inspect very carefully up the roof from the nail. If you do not find anything obvious then water test the roof.

 Water testing a roof can be a slow and tedious process, patience is a must. This process requires two people, one on the roof and one in the attic (or living space below if no attic exists). Use a garden hose turned to about half pressure. Start a point directly downhill from the suspected problem area. Do not force water between the shingles or spray the water uphill. This can cause a leak. Stand uphill from the water on the dry part of the roof, to help prevent slipping. Spray an area about 4 ft wide. Work your way up the roof about 2 feet at a time. Don't forget that sometimes the water has to travel  a long distance to show in the attic. This is where the patience comes in, if you move the hose uphill too quickly you will not be able to tell if the leaks is from where you had the hose or where you moved it to. Have your partner in the attic  and have him yell at the first sign of water.

   Tool to find your roof pitch. Here