Why mold is so common in Marin and Sonoma
Rain is the starting point. Kentfield, in the Ross Valley, averages roughly 44 to 48 inches a year, against about 32 inches in Santa Rosa, and most of it falls between November and March. Search interest in mold in both counties peaks in February, right when roofs, gutters, and crawl spaces have had months of water.
The housing stock is the other half. The median Marin home was built in the mid-1960s, and roughly 56 percent of homes predate 1970. That means older plumbing, original windows, raised wood floors over soil, and attics and bathrooms that were never vented to current standards. Fog and shaded, wooded lots slow drying further, so a small leak can stay wet long enough to grow mold.
Mold remediation and mold removal
A good remediation plan does three things: finds and fixes the water source, removes the mold and the damaged materials under containment, and dries the structure before it is closed back up. Contractors seal the work area with plastic and run HEPA air scrubbers so disturbed spores stay inside it. Moldy drywall, insulation, and carpet are usually cut out and bagged; framing is cleaned and dried.
The EPA says homeowners can generally clean up an area smaller than about 10 square feet themselves once the moisture is fixed. Larger areas, mold inside walls or ductwork, mold from flood or sewage water, and any job that could disturb asbestos in a pre-1980 home are better left to a professional. Spraying or fogging a product without removing anything is not remediation, because the EPA notes that dead mold can still cause allergic reactions.
Mold inspection and testing
Testing is not always needed. The EPA says that in most cases, if mold is visible, sampling is unnecessary, and the CDC notes there are no set standards for an acceptable amount of mold in a home. An inspection earns its cost when you smell mold but cannot find it, when you are buying or selling (termite reports exclude mold), when a landlord and tenant disagree, or at the end of a job.
For that last step, we recommend clearance testing by an independent firm that did not do the remediation, before walls are closed or tenants move back in. California law does not require it and does not bar one company from doing both, but a result from someone with no stake in the cleanup is easier for you, a buyer, or a tenant to trust.
Crawl space and attic mold
Under raised-floor homes, damp soil and winter runoff can keep floor joists and subfloors wet for months, and mold follows. Cleaning the framing is only half the job. The lasting fix is moisture control: drainage that moves water away from the foundation, a sealed vapor barrier over the soil, and either proper vents or a sealed, dehumidified crawl space.
In attics, the usual causes are bath fans that end in the attic instead of outdoors, warm indoor air leaking up through the ceiling and condensing on cold roof sheathing, roof and skylight leaks, and blocked eave vents. Remediation cleans the sheathing and rafters; the ventilation and leak repairs keep it from coming back.
Mold after leaks and floods
The EPA advises drying water-damaged areas and items within 24 to 48 hours to prevent mold growth. Burst pipes, water heater failures, and roof leaks are the everyday cases. In Sonoma County, the Russian River adds flood risk: in February 2019 it crested around 46 feet, and roughly 1,900 homes in the county were damaged. Guerneville and Monte Rio flood again and again. In Marin, the New Year’s Eve flood of 2005 put about four feet of water into downtown San Anselmo.
Coverage depends on your policy and the cause, and no contractor should promise what insurance will pay. FEMA notes that standard homeowners policies do not cover flood damage. Photograph everything before work starts and ask your insurer how they want the loss documented.
How it works
Call or send the form with what you're seeing, where, and whether there was a leak or flood. We pass the details to a local mold remediation contractor, who follows up to look at the problem and give you a written estimate. There is no obligation to go ahead.
North Bay Mold Remediation is a referral service, not a contractor. California has no mold-specific license, but any job of $1,000 or more in labor and materials needs a CSLB-licensed contractor. You can check any license at cslb.ca.gov.
Frequently asked questions
Does it cost anything to request an estimate?
No. Calling or sending a request is free, and there is no obligation. We pass your details to a local mold remediation contractor, who will tell you up front whether their visit or inspection carries a fee.
Which areas do you serve?
Marin County, including San Rafael, Terra Linda, Novato, Mill Valley, Sausalito, Tiburon, Larkspur, Corte Madera, San Anselmo, Fairfax, and Kentfield, and Sonoma County, including Santa Rosa, Petaluma, Sebastopol, Rohnert Park, Windsor, Sonoma, and the Russian River towns of Guerneville and Monte Rio.
Does California require a mold license?
California has no mold-specific license, and the CSLB does not list a mold classification. What the law does require is a CSLB license for any job of $1,000 or more in labor and materials, or any job that needs a permit. Local remediation firms commonly hold a B General Building license. If the work could disturb asbestos, which is common in homes built before 1980, it also needs CSLB asbestos certification or a C-22 license with DOSH registration, or a subcontractor who has one. Check any contractor at cslb.ca.gov and ask for proof of liability insurance.
Do I need to test mold before it is removed?
Usually not. The EPA says that in most cases, if mold is visible, sampling is unnecessary, because the fix is the same whatever the species. Testing is more useful when you smell mold but cannot find it, for a home sale or rental dispute, or as independent clearance testing after remediation.
Is the mold in my house making me sick?
We can't answer that, and neither can a contractor. The CDC says mold affects people differently, and that people with asthma, mold allergies, or weakened immune systems may react more severely. If you have health concerns, talk with your doctor. What a contractor can do is find the moisture, remove the growth, and keep it from coming back.
Will homeowners insurance pay for mold remediation?
It depends on your policy and on what caused the mold. Some policies cover mold that results from a sudden covered event, like a burst pipe, and limit or exclude mold from long-term leaks or humidity. Standard homeowners policies do not cover flood damage, which takes separate flood insurance. Check your policy or call your agent, and photograph the damage before work starts.