California's Department of Public Health (CDPH) puts it simply: mold needs food and moisture, food is almost always available, so whether mold grows depends mostly on moisture (CDPH). An inspection that finds mold but not the water behind it hasn't done the job.
Signs you need an inspection
CDPH lists these signs of a mold or moisture problem:
- Water-stained, discolored or moldy surfaces
- Warped floors, peeling or bubbled paint, or rotting wood
- Damp surfaces, including condensation on windows or walls
- An earthy, musty or moldy smell
CDPH says not to ignore mold odor; it's one of the best indicators of potential health risk, even when you can't see anything.
What a thorough inspection covers
- Visual inspection of living areas, bathrooms, kitchen, laundry, attic and crawlspace.
- Moisture readings with meters, and often thermal imaging, to find wet materials inside walls, floors and ceilings.
- Source tracing: plumbing leaks, roof and window leaks, poor venting, condensation, groundwater and drainage toward the house.
- A written report with photos, the likely moisture sources and a recommended scope of work.
Finding hidden mold can require opening small areas of wall or flooring; CDPH notes that thorough investigations may involve some damage to building materials.
Sonoma County hot spots
- Crawlspaces under homes in Sebastopol, Forestville and other damp, shaded west county areas. See crawlspace mold.
- Flood-affected homes on the lower Russian River, along the Laguna and near the Petaluma River. See mold after a flood.
- Attics where roof leaks or poor ventilation leave sheathing damp. See attic mold.
Want a local pro to take a look?It's free for homeowners and there's no obligation.
Who does inspections?
CDPH says there are no California regulations for mold inspectors and suggests professional associations such as IAQA and AIHA for consultants, and NORMI and NAMRI for inspectors. Ask about experience, what the inspection includes and whether the inspector also sells remediation. Some homeowners prefer an independent inspector for that reason.
Request a mold inspection or call (628) 336-1777.
Where we connect homeowners
- Mold removal in Santa Rosa
- Mold removal in Petaluma
- Mold removal in Rohnert Park & Cotati
- Mold removal in Windsor
- Mold removal in Healdsburg
- Mold removal in Sebastopol
- Mold removal in Sonoma
- Mold removal in Glen Ellen & Kenwood
- Mold removal in Cloverdale
- Mold removal in Guerneville & the lower Russian River
- Mold removal in Forestville
Other services
Dealing with this right now?Tell us what's happening and we'll connect you with an independent local provider.
Sources
Sources checked October 18, 2026.
Frequently asked questions
How long does a mold inspection take?
For a typical home, often one to a few hours, longer if the crawlspace and attic are large or hard to access.
Will the inspector take air samples?
Some do. CDPH says that if you can see or smell mold or moisture, testing isn't needed and doesn't give more useful health information. Ask what any sampling is meant to answer.