Ventilation: The Leak That Is Not a Leak — Inspection Notes
What a real inspection covers on an asphalt shingle roof in the Valley, and what usually gets skipped.
A roof inspection is only as good as what gets looked at, and a lot of what gets called an inspection is a walk round the garden with a phone camera. This is what a real one covers on an asphalt shingle roof in the San Fernando Valley.
What actually matters
A shingle roof is a water-shedding system, not a waterproof one. Every course relies on the course above it and on the underlayment beneath, so the covering and the layer under it fail together and have to be judged together. An inspection that does not account for that is looking at the wrong layer.
The detail that is usually left out
An inspection is only as good as what gets looked at, and photographs of specific defects are what let you get a second opinion without a second visit. The starter course and the drip edge are where cheap work shows first. A starter strip laid the wrong way round, or an eave with no metal under the first course, will wick water back into the fascia no matter how good the shingles above it are. Anything under half an hour on an average house has skipped something.
What is specific to the San Fernando Valley
Summer is the problem here. The Valley runs ten to fifteen degrees hotter than the coast and holds it for weeks, so a roof surface that reads 90 degrees in Santa Monica is well past 160 in Van Nuys by mid-afternoon. Everything on the roof expands into that heat and contracts again overnight, and it is that daily movement, not the peak temperature, that opens laps and backs fasteners out. Most of the housing went up between 1950 and 1975, which means original decking, undersized ventilation and at least one previous layer that somebody roofed straight over rather than tearing off.
The full inspection list
- Granule loss across the field, and how much is sitting in the gutters
- Curling, cupping or cracking, particularly on the sun-facing slopes
- Nail placement and whether shingles have begun to back off the deck
- Valley construction, and whether it is woven, closed-cut or metal-lined
- Flashing at every wall, chimney, skylight and pipe penetration
- Deck condition underfoot, checked by walking rather than by eye
- Attic ventilation, both intake at the eave and exhaust at the ridge
Common questions
How long should an inspection take?
Long enough to get on the roof and into the attic. Anything under half an hour on an average house has skipped something.
Should I expect photographs?
Yes, and of the specific defects rather than general views. Photographs are what let you get a second opinion without a second visit.
The honest summary
Shingle roofs rarely fail suddenly. They give years of warning through granule loss and edge curl, and the difference between a planned replacement and an emergency one is usually whether anybody was looking. In the San Fernando Valley the thing to watch is attic temperature and intake ventilation, because a Valley attic that cannot breathe cooks the underside of the roof as hard as the sun cooks the top.
Free inspection, drone photography where access is difficult, and a written estimate with deck repair priced per sheet. No obligation.
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- What a Shingle Re-Roof Costs in Orange County — The Short AnswerShingle Roofing
- What a Shingle Re-Roof Costs in Los Angeles — Long-Term ViewShingle Roofing