Atmospheric River Roof Prep: The San Rafael Checklist

NOAA’s climate record puts San Rafael’s annual rainfall around 32–34 inches — and the monthly pattern matters more than the total. The rain concentrates from November into early April, and a handful of atmospheric rivers deliver a large share of it. The city’s wettest recorded day, in December 1995, dropped 8.74 inches. A roof does not need to survive average weather; it needs to survive the worst weekend of the year. October is when that gets decided.

What should be checked before storm season?

• Valleys: cleared of debris and checked for worn or cracked lining — valleys carry the most water per square foot on the roof.
• Gutters and downspouts: cleaned, re-pitched where they hold water, and discharge routed away from the foundation.
• Flashing: chimney, wall, and vent flashing inspected — flashing failures are the most common storm-season leak.
• Tile: slipped or broken tiles replaced before wind works them looser (and check the underlayment clock if the roof is past twenty).
• Low-slope sections: drains and scuppers cleared — ponded water finds every weak seam.
• Trees: branches overhanging the roof trimmed back; saturated Marin soil plus wind is how limbs arrive.

Why do roofs that “never leaked” leak in atmospheric rivers?

Because storm rain is a different test. Wind drives it uphill under laps and tile; gutters overflow back under eaves; valleys carry volumes they never see in ordinary rain; and 8 inches in a day exposes marginal details that a decade of drizzle politely ignored. Most “sudden” storm leaks are old weaknesses meeting their first real examination. The pre-season version of the same story is a maintenance list — which is the entire point of checking in October instead of January.

What should you do during and right after a big storm?

During: stay off the roof, full stop — wet roofs and ladders are how storm season hurts people. Contain water indoors, note where it appears, and photograph the stain and anything visible from the ground. After: walk the property for slipped tile, lifted shingles, and debris; photograph everything before cleanup; and if water got in, our storm damage team’s first job is making the roof watertight, with documentation your insurer can use — our insurance claim page explains how that file gets built.