Where leaks usually start
In our area, the top five are: flashing around chimneys and walls, the boots around vent pipes, valleys packed with leaves, broken or slipped tiles, and old underlayment under a tile roof. Skylights are a close sixth.
Flashing and pipe boots are small, cheap parts that fail before the rest of the roof. Replacing them is often the whole fix.
What to do while it is raining
Catch the water and move what can get wet. If the ceiling is bulging, poke a small hole in the low point so the water drains into a bucket instead of bringing the drywall down. Do not climb on a wet roof. Call us and we will tarp it if rain is still coming.
Why patches fail
A dab of roof cement over a crack can stop a drip for a season. In our sun it dries, shrinks and lets go. We use it only as a stopgap and replace the failed part instead.