While a leaky roof is a common occurrence, you probably don't realize how difficult it is to recognize one. The breach isn't readily apparent, in fact you often won't know that you have a leak in your roof until the water has soaked and spread through building materials and seeped through them. The resulting leak could be many feet from where the actual hole is. In some cases, it can be easy to spot a leak if you can visibly see damaged shingles or water stains. Otherwise, you may have to do a little detective work to find the leak before the whole roof goes bad. Here are some tips on how to identify the true location of a leak.
Head to the Attic
If you have an attic, then you could easily find the leak by going up on a rainy day. Be sure to take a flashlight with you as it will make it easier to spot the water that is dropping through the breach. Mark the area with a marker, and wait for a non rainy day to proceed. Go to the roof while somebody taps on the spot that you marked. The area should bend under the pressure of the taps. Seal in the area with roofing cement or new shingles depending on the problem.
If you Don't have an Attic...
For those who don't have an attic, there are certain areas of ceilings that can show moisture damage. Exhaust fan flashings and boots around plumbing vents and air vents can cause leakage.
Other ways to find leaks
Examining darkened ceiling tiles, corners that have mold in them, and insulation that remains damp for weeks after a storm are all telltale signs of leakage. If you don't want to wait until it is raining, then get out on the roof with a garden hose. Have someone watch while you hose different sections of the roof. In this situation, make sure that you are properly outfitted. Note that roofs are designed to become slick when water touches it, so you would need boots with proper traction. Begin at the outside of your roof, and be systematic about where you will cover. Do not point the hose at the apex of the roof, as gravity will distribute the water everywhere and make the experiment useless.
If you are still unable to locate where the leak is coming from, then it might be best to contact a professional roofer. Most leaks can be fixed inexpensively, and nearly every leak can be either plugged or patched with little cost or inconvenience. However, if there is a problem with your shingles, it is better to know sooner than later, as the problem only compounds with time.