The faults that govern Marin
The San Andreas comes ashore at Bolinas Lagoon and runs north up the Olema Valley and beneath Tomales Bay. In 1906 a fence line near Point Reyes Station was offset by roughly twenty feet — the largest measured slip of that earthquake, and the reason the fault's behavior was first properly understood. The Rodgers Creek fault lies north across San Pablo Bay, and the Hayward fault to the south-east.
Soils, slopes and site conditions in Marin
Most of Marin's hill country is Franciscan bedrock, which is comparatively favorable ground. The exceptions are significant: Bay Mud along the Richardson Bay shoreline through Sausalito and Mill Valley, and across the Corte Madera and Larkspur flats, plus fill in Marin City and Strawberry. Southern Marin's slopes are steep and have a long landslide record, and West Marin sits directly in the fault zone.
What Marin is actually built out of
Mill Valley, Sausalito, San Anselmo, Ross and Fairfax are full of 1900s to 1930s houses on steep lots — stepped foundations, post-and-pier under the downhill side, long stair access and frequently no vehicle access at all. San Rafael, Terra Linda and Novato add 1950s to 1970s slab and raised tract housing. Tiburon and Belvedere carry very high-value custom construction, and West Marin has ranch and coastal properties sitting on or beside the fault trace.
Carriers price each of these differently. Wood frame on a bolted raised foundation is treated differently from slab-on-grade, post-and-pier carries the highest foundation surcharge in the standard model, and pre-1980 construction without documented retrofit faces an age surcharge that retrofit reduces but does not erase.
How Marin risk turns into a premium
Marin's county factor is only moderate-high, but its building stock is not. Steep-lot houses on post-and-pier or cripple-wall foundations, at Marin replacement costs, with restricted access for equipment — that combination narrows carrier appetite and pushes the available deductible range up more than the tier by itself would suggest. The bedrock under much of the county is the offsetting advantage.
- County risk factor: Marin County carries a moderate high tier and a 1.18x multiplier against the CDI-anchored base rate.
- Dwelling limit: Premium scales with the earthquake dwelling limit, which should track your real rebuilding cost rather than your purchase price.
- Deductible: A 5% deductible costs roughly 42% more than a 15% baseline; 25% costs about 22% less. It is the largest lever you control.
- Construction type: Brick and masonry add roughly 38% to the base rate; wood frame sits slightly below baseline.
- Foundation type: Post-and-pier runs about 1.22x, raised about 1.08x, slab about 0.94x.
- Year built and retrofit: Pre-1980 raised-foundation homes without verified retrofit carry an age surcharge. Documented retrofit reduces it.
Choosing a deductible in Marin
Because values are high, run the percentage-to-dollars conversion explicitly. Retrofitted and slab homes in San Rafael and Novato usually reach the lower options. Steep-lot pier-foundation houses in southern Marin often do not, so establish availability before optimizing.
Remember that a percentage deductible applies to the dwelling limit, not to the claim. On a $750,000 limit, 15% is $112,500 you pay before coverage responds — whether the damage is $120,000 or $700,000. That is why the comparison has to be made in dollars.
What documentation is worth most in Marin
For a Mill Valley or Sausalito house stepping down a slope on posts and piers, an engineer's letter describing the foundation and the lateral load path is worth more than any other single document. For the flatter pre-1940 stock in San Anselmo, Fairfax and San Rafael, bolting and cripple-wall bracing apply normally. Chimneys on the older stock should be disclosed.
Partial documentation still helps. A permit showing bolting was completed, photographs of cripple wall work, or an Earthquake Brace + Bolt completion certificate all give an underwriter more confidence than a blank field. The application captures retrofit year, contractor, permit number and notes.
If you are buying earthquake coverage in Marin
If your house is on posts and piers down a hillside, invest in the engineering description before you invest in shopping. Bolinas, Olema, Point Reyes Station and Inverness addresses sit in or beside an Alquist-Priolo fault zone and should expect that question. Everyone in the county should get a real replacement cost — Marin land values distort dwelling limits badly.
These are the Marin communities this page is written for: San Rafael, Novato, Mill Valley, Sausalito, Tiburon, Larkspur, Corte Madera, San Anselmo, Fairfax, Ross, Point Reyes Station, Bolinas.
Before you start the application, gather your homeowners declarations page, year built, square footage and stories, foundation type, retrofit permits or certificates, water heater strapping status, masonry chimney condition, any prior earthquake or structural claim, and lender details if earthquake coverage is required by a mortgagee.
Related Marin coverage pages
Nearby counties we publish:
Sonoma County · Contra Costa County · San Francisco · Solano County
Fault corridors that reach this county:
San Andreas Fault corridor
Coverage and underwriting guides that matter here:
Raised and pier foundations · Hillside homes · High-value homes · Older homes
Start wider:
All California county pages · California earthquake insurance guide · Deductible calculator · Carrier markets
Common questions about Marin earthquake insurance
Why does a post-and-pier hillside house in Marin cost more to insure?
Post-and-pier foundations carry the highest foundation surcharge in the standard model because the load path from the house to the ground is the weakest of the common types. On a steep lot with limited access, repair costs after a loss are also higher. An engineer's description of the lateral system is the most effective way to improve the terms offered.
Are West Marin properties in an Alquist-Priolo zone?
Many are. The San Andreas runs up the Olema Valley and beneath Tomales Bay, and the state has mapped earthquake fault zones along it. Properties in or adjacent to those zones should expect the question on an application and should have any available disclosure or geological report to hand.
Does standard homeowners insurance cover earthquake damage?
No. California homeowners policies (HO-3, HO-5) explicitly exclude earth movement including earthquake shaking. You need a separate earthquake policy for dwelling, contents, and loss-of-use coverage.
How is a percentage deductible calculated?
It applies to your insured dwelling limit — not the claim amount. A 15% deductible on an $800,000 home means $120,000 out of pocket before insurance responds, regardless of total damage. Use the calculator in the sidebar to see your number.
How long does it take to get coverage?
After submitting the application, a broker typically follows up the same business day with market options. Binding and policy issuance generally takes 1–5 business days depending on the carrier and whether additional documentation is needed.