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Should I repair or replace my Marin roof?

Short answerIn Marin, moss is the usual tiebreaker. If shingles under the trees are still flat and intact, clean and repair. If moss has lifted shingle edges across the roof, or the deck is soft, replace. Replace too when a Novato or San Rafael roof has two layers or heat-cracked shingles on its sunny slopes.

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Updated · Sources reviewed November 11, 2026 · By Marin Roof Replacement

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The moss question

Moss holds water against the roof and pushes shingle edges up so wind-driven rain gets under them. On a younger roof, cleaning and a few replaced shingles can work. On an older one, lifted, brittle shingles across the shaded slopes mean the roof is done.

Damp side vs. sunny side

Fog and shade (Mill Valley, Fairfax, the San Geronimo Valley) cause moss, rot and corroded fasteners. Sun (south-facing San Rafael and Novato slopes) causes granule loss and cracking. Many Marin houses have both, on different slopes.

Code limits

No new roof over two layers, over water-soaked roofing, or over tile or slate (CRC R908). Many older Marin homes already have an overlay.

Expected life

InterNACHI lists architectural shingles at about 30 years, 3-tab at 20 and wood shake at 25 (InterNACHI).

Fire zone factor

If you're in a mapped very high fire hazard severity zone, a replacement over half the roof must be Class A. Small repairs usually don't trigger that.

Every roofer we work with is licensed, insured and highly reviewed by Bay Area homeowners.

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Frequently asked questions

Will cleaning moss damage my roof?

Aggressive pressure washing can. Ask a roofer about gentle cleaning and treatment.

My Mill Valley roof leaks only in big storms. Repair?

Wind-driven rain often enters at lifted shingles or flashing. If it's isolated, repair; if it's roof-wide, plan to replace.

Is an overlay allowed in Marin?

Only over one sound layer that isn't tile or slate.

Related questions

Sources

Sources reviewed November 11, 2026. Figures are published estimates and official fees, not quotes. Confirm prices, permits and requirements with your contractor and building department. This page is general information, not legal or insurance advice.