Visible Mold Is Now a Substandard Condition in California (SB 655)

Published August 10, 2026

SB 655 added visible mold growth to the list of substandard housing conditions in Health and Safety Code section 17920.3. Here is what the statute actually covers, what it excludes, and what that means for a South Bay landlord.

The short answer

California added visible mold growth to the legal definition of a substandard building condition through SB 655, codified at Health and Safety Code section 17920.3, subdivision (a), paragraph (13). It excludes minor mold on surfaces that normally accumulate moisture as part of their intended use, like a shower tile edge. A code enforcement officer or health officer can cite a property for it like any other substandard condition.

Last verified: August 10, 2026

What the statute actually says

Health and Safety Code section 17920.3 is the list California uses to define a "substandard building" for purposes of state housing law. It groups conditions into categories: inadequate sanitation, structural hazards, nuisance, faulty weather protection, and so on. Inadequate sanitation is subdivision (a), and it currently runs sixteen paragraphs, covering things like lack of a working toilet, lack of hot and cold running water, inadequate heating, inadequate ventilation, dampness of habitable rooms, and infestation of insects, vermin, or rodents.

SB 655 added paragraph (13) to that list. The current text reads:

"Visible mold growth, as determined by a health officer or a code enforcement officer, as defined in Section 829.5 of the Penal Code, excluding the presence of mold that is minor and found on surfaces that can accumulate moisture as part of their properly functioning and intended use."

Two things do real work in that sentence.

First, it has to be visible. The statute does not require air sampling, spore counts, or a lab report. A health officer or code enforcement officer determines the condition by looking at it. That is a lower bar to trigger an inspection finding than most owners assume, and it cuts the other way too: if nothing is visible, this specific paragraph does not apply, whatever a tenant's mold testing kit claims.

Second, it excludes minor mold in its expected place. Mildew forming on grout in a functioning shower, or a bit of surface mold on a windowsill that gets condensation, is not automatically substandard. The exclusion exists because some moisture-adjacent surfaces are supposed to get wet as part of normal use. The line the statute draws is between mold that is minor and confined to a surface built to handle moisture, and mold that signals something is actually wrong, a leak, poor ventilation, a failed vapor barrier, water intrusion behind a wall.

Where the mold paragraph sits inside the bigger law

Section 17920.3 is not standalone. It is the operative definition used across the State Housing Law (Health and Safety Code, Division 13, Part 1.5). When a jurisdiction inspects a rental and finds one or more of the conditions in that list, the building can be classified as substandard, which opens the door to notices, abatement orders, and in some cities rent escrow or receivership proceedings under separate local and state mechanisms. Mold sits in that same list next to lack of heat and lack of running water. It is not a separate, softer category.

The section has been amended multiple times since SB 655 added the mold paragraph in 2015. The version in effect today was most recently amended by a 2024 bill (SB 1465), effective January 1, 2025, which touched other paragraphs in the same subdivision. The mold language itself, paragraph (13), traces back to SB 655.

Table: where mold sits among the inadequate sanitation conditions (Health and Safety Code section 17920.3(a))

| Paragraph | Condition (summarized) |

|---|---|

| (1) to (5) | Missing or nonfunctioning plumbing fixtures, hot and cold running water |

| (6) | Inadequate heating |

| (7) to (8) | Inadequate ventilation, inadequate natural light |

| (9) to (10) | Insufficient room dimensions, inadequate electrical lighting |

| (11) | Dampness of habitable rooms |

| (12) | Infestation of insects, vermin, or rodents |

| (13) | Visible mold growth, excluding minor mold on surfaces built to accumulate moisture |

| (14) to (16) | General dilapidation, faulty materials, or sewage and waste disposal deficiencies |

Confirm the current full text of every paragraph directly at leginfo.legislature.ca.gov before relying on a summary, since the surrounding paragraphs get amended independently of the mold language.

What this means for a South Bay landlord

The practical shift is that a maintenance issue you might have treated as cosmetic, a stained ceiling tile, a musty smell in a downstairs bathroom, a moisture line in a garage-converted bedroom, now has a specific statutory hook if it is visible mold and it is not the minor, expected kind. That does not mean every tenant complaint about mold is automatically a code violation. It means an inspector who sees it does not need a separate finding of dampness or ventilation failure to act, because mold growth is its own listed condition.

The response that actually protects you is the same one good habitability practice already calls for. Investigate the moisture source, not just the visible mold. Mold growth back on the same spot after a wipe-down is a sign the underlying leak or ventilation problem was not fixed. Document what you found, what you did, and when, since that record is what distinguishes a landlord who responded promptly from one who painted over a problem.

South Bay housing stock adds a specific risk factor here: coastal humidity and older units with limited mechanical ventilation, especially ground-floor and garage-adjacent units in El Segundo, Hermosa Beach, and Redondo Beach, run warmer and damper than inland stock. Bathroom exhaust fans that vent into an attic instead of outside, and older single-pane windows that condense heavily in winter, are common contributors worth checking proactively rather than waiting for a complaint.

FAQ

Does a landlord have to remediate mold immediately once it is spotted?

The statute defines mold growth as a substandard condition; it does not itself set a specific remediation timeline. Response time obligations generally flow from separate habitability and repair-notice law and any local housing code. Treat visible mold as an active habitability issue and document your response promptly.

Does the exclusion for surfaces that "accumulate moisture as part of their intended use" cover a bathroom generally?

It covers specific surfaces built for moisture exposure, like tile grout in an actively used, properly ventilated shower, not a bathroom's walls, ceiling, or subfloor generally. A ventilation failure that lets mold spread beyond the shower surface itself is not automatically covered by the exclusion.

Can a tenant demand a mold test before a landlord has to act?

The statute does not require lab testing. A health officer or code enforcement officer can find a violation based on visible growth alone. Landlords are also not required to test before remediating; fixing the moisture source and the visible growth is generally the operative response.

Is mold covered by a standard landlord insurance policy?

Coverage varies significantly by carrier and policy, and many California landlord policies exclude or sharply limit mold-related claims. Confirm your specific policy language with your insurance broker rather than assuming coverage.

Does this statute apply to owner-occupied duplexes and small buildings the same as large apartment complexes?

Section 17920.3 defines a substandard building under the State Housing Law generally and is not limited by unit count in the mold paragraph itself. Confirm how your local jurisdiction applies inspection and enforcement authority to your specific property type.

This article is general information about a California housing statute, not legal or environmental health advice. Confirm current requirements and your specific obligations with a California landlord-tenant attorney or your local code enforcement agency before making remediation, disclosure, or litigation decisions for your property.

Topics: compliance, mold, habitability, South Bay, landlord duties, SB 655

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