Summer roof leaks usually start at a weak spot the heat has opened up: the rubber boot around a plumbing vent splits, the sealant at a chimney or skylight cracks, a shingle curls at the edge. Then a thunderstorm finds the gap, often with wind pushing the rain sideways, and a clogged gutter adds more water at the edge of the roof. Late summer is when to find them. The fixes are still small, and the fall rain and the first freeze haven’t gotten to them yet.
What heat and sun do to shingles
Asphalt shingles wear hardest in two kinds of weather, below-freezing cold and the most intense sun and heat. A Lehigh Valley roof gets both, and summer brings the second.
The granules on a shingle shield the asphalt from the sun, and as they wear off, the asphalt dries out, the shingle turns brittle and its edges start to curl or crack. A curled edge is an easy way in for rain that’s blowing sideways. On your own roof, start with the slopes that face south and west, which take the strongest sun. Look for patchy, faded color, bare spots, and dark grit collecting in the gutters.
Rubber and sealant age the same way. The collar of a plumbing vent boot dries in the sun until it splits around the pipe, and the caulk that finishes the corners of chimney and skylight flashing hardens and pulls away. Neither shows from inside. Not until a long rain gets through.
Thunderstorms bring wind and falling limbs as well. Our guide to summer storm roof damage covers those.
A hot attic works on the roof from below
On a summer afternoon the sun heats the roof deck from above, and a closed-up attic heats it from underneath. Ventilation is what lets that heat out. Air comes in through vents under the eaves, called soffit vents, and leaves near the ridge. When insulation has been pushed into the soffit vents, or a bathroom fan blows into the attic and not outdoors, the attic stays hot and damp.
Humid air from the house adds to it. Our post on how humidity affects roof shingles explains what that moisture does. If your attic air is stifling and never seems to move, or the insulation smells musty, ask about the ventilation when the roof is next looked at.
Where the water gets in
- Vent boots, once the rubber collar has split.
- Chimney flashing that has rusted, or pulled out of the mortar joint it was tucked into. Leaks around a chimney have a guide of their own.
- Valleys, the channels between two slopes, which take the runoff from both. Leaves, seed pods and storm debris pile up there and hold water against the shingles. See our guide to roof valley leaks.
- Skylights, and the step flashing where a roof runs up against a wall. Our page on roof flashing repair goes through both.
- The eaves, when a blocked gutter spills over in a downpour and the water works in under the first row of shingles.
- Shingles that have curled, cracked or blown off, and nails that have worked loose and lifted the shingle above them.
A late-summer check from the yard and the attic
You don’t need a ladder for any of this, and you shouldn’t be on the roof. Our guide to the roof inspection process lists the rest of what you can check from the ground. These are the summer ones.
- Next time it pours, watch the gutters from an upstairs window. Water sheeting over the front edge means a clog, or a gutter that has lost its slope.
- With binoculars, go over the south and west slopes for curled edges, cracks and bare patches.
- Find each vent pipe from the yard. If its rubber collar looks cracked or has pulled back from the pipe, it’s due for replacing.
- The morning after a heavy storm, check the ceilings under the roof. If the attic is easy and safe to get into, look at the boards around the vent pipes and the chimney for dark, wet patches.
Get it fixed before the fall rain
Fall fills the valleys and gutters with leaves. Then winter’s freeze and thaw goes to work on any water that got in, and our guide to winter roof inspections explains what that does. Replace a split boot in August and that’s the whole job. Leave it through a wet fall and the decking around the pipe may need replacing too.
When you call about a leak, we track it back to where the water is actually getting in, then give you a free written estimate for the roof repair. For a look at the whole roof before winter, book a roof inspection. Call (484) 553-0213 or request an estimate.