San Ramon, CA Rental Property Rules: Mold Disclosure (2026)

San Ramon does not adopt a local mold ordinance; the governing law is California's Toxic Mold Protection Act (Health & Safety Code sections 26100-26156) together with Civil Code 1941.7 and the implied warranty of habitability codified at Civil Code 1941 and 1941.1. Under Health & Safety Code 17920.3(a)(13), visible mold growth (other than minor accumulations on surfaces that can be cleaned) is a substandard housing condition. Landlords must disclose in writing any known visible mold in a unit or common area before a tenant signs a lease. If mold renders the unit uninhabitable, tenants can invoke the repair-and-deduct remedy (Civil Code 1942), withhold rent, or sue for breach of habitability. California has not adopted permissible exposure limits for airborne mold, so enforcement is based on visible growth and associated building defects like plumbing leaks, roof leaks, or inadequate ventilation. Contra Costa County Environmental Health investigates mold complaints and can issue Notice to Abate orders requiring the landlord to identify the moisture source, remove contaminated materials following IICRC S520 standards, and repair the underlying defect. Tenants should document mold with photographs, preserve air-quality or surface samples if tested, and provide the landlord with written notice and a reasonable time to repair (typically 30 days, or less if the condition is severe) before pursuing remedies. Retaliatory eviction within 180 days of a habitability complaint is prohibited under Civil Code 1942.5.