Heavy rain at the penetrations in Summerville
1435 mm of rain a year, and that volume finds every gap the heat has opened up, mostly at the penetrations and in the valleys; The median home dates from 2001, so most roofs here are still on their first or second covering and the problems are in the detailing rather than in age.
1435 mm of rain a year, and that volume finds every gap the heat has opened up, mostly at the penetrations and in the valleys
The median home dates from 2001, so most roofs here are still on their first or second covering and the problems are in the detailing rather than in age
Summerville takes about 1435 mm of rain a year, and that volume finds every gap the heat has opened up - almost always at a penetration, a valley or a flashing joint rather than in the middle of the slope.
How the damage actually happens
An asphalt shingle is a mat saturated with bitumen and armoured with granules. Sun does two things to it. The ultraviolet drives off the volatiles in the bitumen so the mat goes stiff and brittle, and the daily heating and cooling works the granules loose until bare patches show. A stiff covering no longer moves with the deck underneath it, so the tabs stop sealing down and the joints at every penetration open slightly. Nothing leaks while it is dry. Then the rain arrives all at once and finds every one of those openings.
Summerville spends about 53 days a year above 90F, and it is that heat, not cold, that ages the covering here: the asphalt loses its volatiles, the granules that shield it wear off, and the sealant strip that holds each tab down gives up.
What actually fixes it
- Get someone on the roof to check the granule cover across the whole slope, not just where the stain is - that tells you whether this is a repair or a replacement
- Reseal or rebuild the penetrations and valleys, which is where the rain actually gets in
- Ventilate soffit to ridge so the attic stops holding heat against the underside of the deck
- When it is replacement time, spend the money on the underlayment and the detailing rather than on a longer warranty number
Roof coatings sold as a way to add years to a worn asphalt roof are the thing to be most careful with here. On a covering that has already lost its granules they hide the evidence rather than restore anything, and they can void what is left of the manufacturer warranty. They belong on low-slope membrane, not on tired shingles.
Prices in nearby cities
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