How to Find a Leak in an Asphalt Shingle Roof

Examine the bottom of the roof from the attic space of the house. Water can run along rafters and other structures, so the location of the leak seen in the living quarters may not be directly below the actual leak in the roof. Look for discoloration of the rafters or the underside of the roof sheathing to locate the leak. Measure from the peak to this point as a reference. In worst-case scenarios, light may be visible through a hole in the roof. Push a straw or other narrow item through the hole to mark the location on the exterior.

Measure from the peak of the roof to the point indicated by the measurement in Step 1. Explore the general area for defects. Look for cracks around nails or breaks in shingles. This step helps locate the hidden leaks that sometimes occur even though the exterior of the shingles look fine. It's not necessary if the hole was obvious and marked with a straw or other item.

Explore areas where the shingles are sealed to metal flashing with roofing tar. These are high-risk areas for roof leaks and should be checked if obvious leaks such as those described in steps 1 or 2 aren't visible. Check areas such as where chimneys, vent pipes or other fixtures extend through the roof. Check the roofing tar for cracks or breaks.