Roof leaks often go undetected because the moisture does not penetrate through interior ceilings and walls. But that doesn’t mean they don’t cause damage. Water that breaches a home’s building envelope is slow to dry. This can lead to structural decay, mold and insect infestation.
First you need to find the source of the leak. If moss roots have grown through your shingles you are looking at a new roof. On the other hand, if your roof is leaking around flashing or boots, you may be able to repair the leak and be done. Also, leaks from ice dams may have little to do with the roof. You may need to seal air leaks around ceiling fixtures, ductwork and wires and increase attic insulation and ventilation.
Determining the origin of a roof leak takes close inspection and an understanding of construction. Most important, never assume a leak comes from directly above. Flowing water is notorious for following sheathing, rafters and roof trusses before reaching ceilings and walls. Trusses are especially problematic because cords descend in two directions. That means a leak from a lower part of a roof can present on the ceiling below a higher roof section.
Minor, localized leaks can be patched. Repairs may show because new roofing materials are unlikely to match the old ones. You might not mind if the patch is on the back of your home. But it could dramatically compromise your home’s curb appeal if it is on the front. In that case, consider replacing roofing on the entire forward roof plane.
When installing or replacing a roof, always retain some extra materials in case you need to make repairs years later.