A roof that stays dry in light rain and then drips in a real storm is not failing everywhere. It is often a drainage, flashing, or wind-driven rain problem. Those are different scopes. Top Pro Roofing SD refers. We do not install. Call (760) 750-5557.
Field-wide failure (worn covering and underlayment across the slope) tends to show in ordinary rain, not only in storms. Storm-only leaks are still real water. The entry point often hides in dry weather.
This page does not rank causes by county frequency or assign dollar ranges. The independent roofer prices the actual house. Confirm current climate normals on NOAA’s published tables if you need a number. Coast, inland valley, and mountain sites are not the airport.
What changes in a storm
Two things change: water volume and water direction.
Volume matters because valleys, gutters, and low-slope laps are sized for a flow. Light rain can leave them. A short, hard storm can back water up over a flashing edge, a debris dam, or a membrane lap.
Direction matters because many flashings are built to shed water coming down the slope. Wind-driven rain can push water sideways into gable rakes, vents, and ridge details that stay dry the rest of the year.
A heavy-rain-only leak may appear only a few times a year. That does not mean the last repair worked. It may mean it has not rained hard enough to test the same path again.
Six source families to sort, not to guess
1. Marginal flashing at a transition
Chimney, skylight, pipe, and wall-to-roof flashings live where two materials meet. At low volume, a small gap can still shed. At high volume, water can pond at the gap and enter.
The indoor clue is a stain near a chimney, skylight, vent, or wall intersection. Water can travel along the deck before it drops, so the stain may sit off-center from the outdoor detail.
Ask the roofer to name the flashing type, what was visible, and whether counter-flashing, step flashing, or a curb kit is in the scope. See chimney flashing repair and roof flashing leak repair.
2. Wind-driven rain at gables and vents
Southwesterly storm flow, or rain overlapping a high-wind event, can drive water under rake edges and into vent openings.
Gable rake flashing, ridge vents, box vents, and turbines each have a different opening. Ask whether the leak lined up with a windy storm. The National Weather Service San Diego archive can help you date the event. Weather history is context. It does not prove the failed part.
The proposal should name the vent or rake detail being changed, not “seal vents” as a whole-roof line.
3. Valley overflow and debris dams
Valleys concentrate two slopes into one channel. Leaves, palm fronds, and eucalyptus litter can lodge there. Water then rises above the metal edge and runs under adjacent tile or shingle.
A long indoor stain parallel to a valley is a reason to look at that valley, not proof by itself. Between storms, a debris line or mineral stain on the valley can be worth photographing from the ground.
Ask whether the valley metal width, underlayment, and adjacent courses were actually seen. Code and manufacturer details are product- and jurisdiction-specific. Do not accept “valley is fine” from a dry walk-around if the leak only happens in storms. For tile-specific leak paths, see common causes of tile roof leaks.
4. Low-slope ponding above a lap
On a flat or low-slope roof, water that sits in a depression can stay below a membrane lap in light rain and overtop it in a long storm. Light rain that drains in a day and a storm that raises the pond are different tests of the same seam.
The inspection should record pond location, drain or scupper condition, and which laps were visible. Drainage work and membrane work are different scopes. Flat roof ponding water and flat roof replacement cost cover that family without mixing it into a steep-slope leak.
5. Gutters that spill behind the drip edge
A partly blocked gutter can pass a drizzle and overflow in a storm. Water that goes over the back lip can wet fascia, then find a path under the drip edge into the soffit or wall.
An eave-line stain, especially near a gutter corner, is a reason to watch the gutter in the next light rain from the ground. Cleaning, re-securing, and drip-edge work are separate line items from field-roof replacement. See gutter repair and roof overhangs and eaves.
6. A local covering break over tired underlayment
On tile, the tile is often the UV shield. The underlayment is the waterproof layer. A cracked tile can shed light rain onto underlayment that still drains. Heavy rain can saturate a brittle spot. Shingle roofs can show a similar volume effect at one damaged unit.
A leak that starts during a heavy storm, stops soon after rain ends, stays quiet in drizzle, and returns in the next hard storm is a reason to inspect that local area. It is not automatic proof of whole-roof replacement. Clay tile roof repair covers unit-level tile work.
What to record during the storm, from inside
Stay off a wet roof. From indoors, note:
- How long into the rain before the first drip
- Whether the drip speeds up as rain intensifies
- Whether dripping stops soon after rain ends or continues for hours
- The ceiling location relative to chimneys, skylights, valleys, and eaves
Photos and timestamps help the independent roofer, and they help you if you later talk to an insurer. They do not replace a water test. For a wider diagnostic walkthrough, see how to find a roof leak.
Why a dry-weather walk-around often misses this
A clean valley, an evaporated pond with a faint ring, and a hairline tile crack can all look quiet when it is not raining. Ask whether the visit includes an attic look for staining and rusted fasteners, and whether a controlled hose test is part of the diagnostic if the source is still open.
“We’ll look from the ladder” is not the same as a zoned water test. Ask which method they will use and what remains unconfirmed if they cannot test.
Storm still running versus a stain after it ends
If the storm has ended, dripping has stopped, and the ceiling is intact, you usually have time to get a written diagnostic and compare independent proposals. If water is hitting a fixture, the ceiling is bulging, or multiple new drip points appear, treat it as an active leak. See active roof leak emergency response and emergency roof repair.
Do not climb a wet tile roof to tarp it yourself. If a tarp is needed, that is work for a licensed contractor who accepts the job. Emergency roof tarp covers that step.
Insurance language stays on the policy
California policies vary. Sudden storm damage and gradual wear are different conversations. This page does not decide coverage. Document the storm, the timing, and the interior damage. Read does homeowners insurance cover roof leaks in California. Confirm with the carrier, not with a blog rule of thumb.
How we help
Top Pro Roofing SD is a referral service. We connect San Diego County homeowners with licensed, independent local roofing professionals. The matched roofer inspects, proposes, and contracts with you. Check any license at the CSLB license lookup. Ask for the C-39 number before you sign.
If you need a diagnostic visit for a storm-only leak, call (760) 750-5557 or contact us.
FAQ
Why does my roof leak in heavy rain but not in light rain? Some details shed low volume and fail when volume or wind direction changes. Flashing gaps, valley overflow, gutter backup, low-slope laps, vents, and a local covering break over aged underlayment are common families. The independent roofer still has to match one of them to evidence on your roof.
How do I find the source if it only shows in a storm? Record timing and location from inside during the next hard rain. Then ask for attic observation and, if needed, a controlled water test in zones. A dry visual pass often misses these leaks.
Should I call during the storm or after? If water is actively damaging finishes or fixtures, call for emergency response. If the leak has stopped and the ceiling is intact, schedule a diagnostic in dry weather and compare written scopes.
Is a full roof replacement the usual answer? Not from the fact that the leak is storm-only. Storm-only leaks often sit at a transition or drainage path while the field still sheds ordinary rain. Replacement is a separate finding about the covering and underlayment as a system.
How much does repair cost? This page does not publish prices. Ask independent roofers for a written scope that names the failed detail. Compare those proposals, not a county average.