Mold Remediation and Post-Flood Mold Cleanup in Larkspur

Corte Madera Creek and flood history

Corte Madera Creek drains the Ross Valley and reaches the bay at Larkspur and Greenbrae, and it has a long flood record. A storm early on December 31, 2005, damaged about 1,200 homes and businesses in Marin, most of them along Corte Madera Creek. More recently, on January 4, 2026, the creek overflowed into the Larkspur Marina neighborhood. CBS News reported that roughly half the neighborhood's streets were underwater by noon, and that while many homes there are raised a few feet, garages flooded. Parts of the Riviera Circle area had knee-deep water.

Marin County's Corte Madera Creek Flood Risk Management Project covers the creek through Ross, Kentfield, and Larkspur. The county flood district paused the remaining creek work in February 2026, so check with the district for current status. Even when complete, it reduces risk upstream, but it does not change the tides, and low ground near the creek mouth still sees high water.

After the water goes down

Creek and tidal flood water is not clean water. The EPA's guidance is to dry wet building materials and furnishings within 24 to 48 hours where possible to help prevent mold growth. After a Larkspur flood, the usual sequence is:

• Document first. Photograph water lines, damaged materials, and contents before anything is removed. Your insurer, or your landlord if you rent, will want the record. Coverage depends on your policy, and many standard homeowner policies treat flood differently from a burst pipe.
• Remove what can't be dried. Carpet, pad, and drywall that sat in flood water usually come out, often in a band a foot or more above the water line, along with wet insulation behind it.
• Dry the structure. Dehumidifiers and air movers bring framing back to normal moisture levels before anything is closed up.
• Check the garage and under the house. In raised homes near the marina, garages, storage rooms, and crawl spaces take the water even when the living space stays dry, and they are easy to overlook until a musty smell appears.

Baltimore Canyon, Madrone Canyon, and shade

Above downtown, Larkspur Creek runs down Baltimore Canyon, where the county's 193-acre Baltimore Canyon Open Space Preserve begins at the end of Madrone Avenue. The canyon was logged in the 1800s and is now shaded by second-growth redwoods with bay, madrone, and big-leaf maple. Kentfield, just up the valley, averages roughly 44 to 48 inches of rain a year, among the wettest totals in the Bay Area.

For houses tucked under those trees, the result is a slow-drying site: little winter sun on roofs and walls, gutters full of needles, and runoff moving downslope toward foundations. That is a mechanism, not a mold rate, but it is why a canyon home on a raised floor deserves a look underneath. Growth on joists and subfloor usually comes from damp soil and poor ventilation, and the long-term fix is drainage, a vapor barrier, and working vents alongside the cleanup.

Older homes, rentals, and asbestos

Downtown Larkspur's historic district was listed on the National Register of Historic Places in 1982, and some of its buildings date to the 1890s. Countywide, more than half of Marin's housing units were built before 1970. In homes built before 1980, drywall joint compound, popcorn ceilings, and older flooring may contain asbestos. Testing may be needed before tear-out, and asbestos work requires a C-22 license or CSLB asbestos certification plus DOSH registration.

Under SB 655 (2015), visible mold can make a rental substandard. In Larkspur, Marin County Environmental Health Services handles complaints for rental buildings of three or more units, as it does everywhere in the county except San Rafael and Novato, and it says it does not test for mold. Greenbrae and Murray Park include unincorporated areas, which the county also covers.

Licensing and clearance

California has no mold-specific license. Any job of $1,000 or more needs a CSLB-licensed contractor, usually with a B General or C-61/D-64 license; check it at cslb.ca.gov. Before walls are closed, we recommend mold clearance testing by a firm that did not do the remediation.