A renter's checklist for documenting dampness or mold

The short answer

Treat it as a water problem. The repair that matters is fixing the source of the moisture, then cleaning or replacing what got wet. You usually do not need a mold test or to know the type of mold.
Document, then tell the landlord in writing. Take dated photos and notes and keep a copy of what you send. In California, a landlord's duty to repair mold begins once the landlord has notice of it.
If repairs don't happen, ask for an inspection. In California, dampness of living spaces and visible mold growth, as judged by a health or code enforcement officer, can make a home legally substandard.
Know your protections and the risky options. California limits retaliation after you complain. Deducting repair costs from rent, or holding back rent, can lead to an eviction case. Talk to legal aid first.
Watch your health. Get medical advice if symptoms last, if asthma gets harder to control, or if someone at home has a weakened immune system.

Get help now

Call 911 for severe shortness of breath at rest, extreme difficulty breathing, bluish lips or face, or drowsiness or confusion. For an active leak, call or text the landlord or manager right away, then follow up in writing.

Step 1: Look for the water, not the type of mold

Signs of a moisture problem include water stains, flaking or bubbling paint, a damp or musty smell, condensation that keeps coming back, and dark spots on walls, ceilings, floors or inside cabinets. Common sources are roof, window and plumbing leaks, and moisture from showers, cooking or drying clothes indoors.

You do not need a mold test to report a problem. The Centers for Disease Control and Prevention (CDC) does not recommend testing: sampling cannot reliably show who might get sick, and there are no set standards for acceptable amounts. The California Department of Public Health (CDPH) advises against using mold measurements to judge how hazardous a home is, and says the evidence does not support singling out particular types of mold as more hazardous than others. The U.S. Environmental Protection Agency (EPA) says there are no federal limits for mold indoors.

"Black mold" is not a separate category of danger. CDC says all molds should be treated the same way for health risk and removal: remove the mold and fix the moisture.

California's housing law does exclude minor mold on surfaces that get wet as part of normal use, such as a little mildew on shower grout. Routine cleaning of those spots is usually the tenant's job. Mold on walls, ceilings, closets or carpet, mold that keeps coming back, or any growth tied to a leak is worth reporting.

Step 2: Document it before anything changes

Start a dated record the first day you notice the problem. A printable dampness and mold photo-and-notice log has columns for each item below.

Photos and video. Take one wide shot that shows which room and wall, then close-ups. Put a ruler, coin or tape measure in the frame for scale. Keep your phone's date and time settings on.
Repeat from the same spot every week or two, so the photos show whether it is spreading.
Write down the details: where it is, roughly how big, whether it is wet to the touch, any smell, when you first noticed it, and whether it got worse after rain or a plumbing problem.
Record damage to your belongings (clothes, furniture, bedding) with photos before you throw anything away. Keep receipts for replacements.
Save every message and log every contact. Keep texts, emails and screenshots of portal requests. For calls and visits, note the date, who you spoke with, what they said and any promised repair date.
Look for move-in records. Find any move-in checklist or photos. For tenancies that began on or after July 1, 2025, California landlords must photograph the unit at the start of the tenancy. They must share their photos with you only if they later deduct repair or cleaning costs from your deposit, but you can ask for copies sooner.
Keep health notes private. If anyone at home has symptoms, a short private note of dates and clinic visits can help your clinician. You do not have to share medical details with your landlord.

Photograph before you clean anything. Cleaning or painting first can erase the evidence an inspector or a court would need.

Step 3: Tell the landlord in writing

California's Department of Real Estate (DRE), in its official guide for tenants, advises notifying the landlord in writing and keeping a copy. If the problem is urgent, call first, then put it in writing right away.

What to include:

the date, your name, address and unit number;
what you see, where, and when you first noticed it;
the likely water source, if you know it;
a clear request: fix the source of the water, then repair the damaged area;
when you can give access, and a reasonable date for a reply. If it is urgent, say why.

How to send it: The DRE guide recommends certified mail with a return receipt. It is not required, but it proves delivery. You can also hand-deliver the letter and ask for a signed, dated receipt. Repair laws mention oral or written notice, not texts or email, so the guide suggests following a text, email or portal request with a letter.

Example (fictional): "On March 3, I noticed a dark, damp patch about the size of a dinner plate on the bedroom wall under the window in Unit 4. The wall feels wet after rain, and the room smells musty. Please find and repair the source of the water and fix the damaged wall. I am home weekday afternoons for access. Please reply by March 10. Photos are attached. I am keeping a copy of this letter."

Letting the landlord in. California law lets a landlord enter to repair mold with proper notice; 24 hours' written notice is presumed reasonable. Note when workers came and what they did.

Your part. California tenants must keep the unit as clean and sanitary as its condition allows, use fixtures properly, and not damage the property. If a tenant's failure substantially caused the problem or blocked the repair, the landlord may not have to fix it. Steps that also strengthen your record:

run bathroom and kitchen exhaust fans during and after showers and cooking, and tell the landlord in writing if a fan does not work;
keep indoor humidity under about 50 percent, using an air conditioner or dehumidifier if you have one (CDC's guidance; EPA gives a 30 to 50 percent ideal range);
wipe up spills and condensation, and dry wet items within 24 to 48 hours;
report leaks as soon as you see them.

Step 4: If repairs don't happen, ask for an inspection

In California, Health and Safety Code section 17920.3 lists conditions that make a building substandard when they endanger occupants' health or safety. They include "dampness of habitable rooms," "visible mold growth, as determined by a health officer or a code enforcement officer," and ineffective waterproofing. Civil Code section 1941.1 treats a rental as "untenantable" (unfit to live in) if it substantially lacks effective waterproofing and weather protection or has a condition listed in section 17920.3.

CDPH says local code enforcement can cite an owner for hazardous visible mold, and the owner must then fix it. CDPH does not inspect homes, and it notes that renters often struggle to find the right local agency. When you call, ask: "Do you inspect rentals for dampness and visible mold? If not, who does?"

In Fresno and Fresno County:

Where the home is	Who to contact	What the agency says
Inside Fresno city limits	City of Fresno Code Enforcement, (559) 621-8400; or call 311, or (559) 621-2489, or use the FresGO app	Try working with the landlord first. If that fails, report it. An inspector must see a violation before the city acts, and serious health and safety problems are handled first.
Unincorporated Fresno County (outside any city)	Fresno County Department of Public Health, Environmental Health Division: (559) 600-3357	Renters should contact their landlords in writing about needed repairs. Cities such as Fresno and Clovis handle complaints inside their own limits.
A mobile home park	California Department of Housing and Community Development (HCD), which Fresno County says enforces codes in mobile home parks	Ask HCD how to file a complaint.

Phone numbers were taken from the agencies' websites as of October 2026. Bring your log, photos and copies of your letters to the inspection, and ask for a copy of the inspection report or notice to the owner.

Why the inspection matters. Under Civil Code section 1942.4, if an inspector notifies the landlord in writing and the problem is still not fixed 35 days later without good cause, the landlord may not demand or collect rent, give notice of a rent increase, or serve a three-day notice to pay rent or quit. This applies only if the tenant did not cause the problem. A landlord who breaks this rule can owe actual damages plus $100 to $5,000. The conditions are specific, so get legal advice before you change how you pay rent.

Step 5: Know your protections and the risky options

Option (California)	What the law says	The main risk
Protection from retaliation (Civil Code 1942.5)	For 180 days after you, in good faith, complain to the landlord about conditions, complain to an agency the landlord knows about (or an inspection or citation follows), or start a court case about conditions, the landlord may not evict you, raise the rent or cut services to retaliate. Your rent must be paid up. A landlord who retaliates can owe actual damages, plus $100 to $2,000 per act where there was fraud, oppression or malice.	You can use the 180-day protection only once in any 12-month period. Retaliation is still unlawful after that, but you have to show it.
Repair and deduct (Civil Code 1942)	For conditions that make the home unfit to live in: after notice and a reasonable time (30 days is presumed reasonable), you may pay for the repair and deduct it from rent. The cost can be no more than one month's rent, and you can use this no more than twice in 12 months. It does not apply if you caused the problem.	The landlord can sue to recover the money or serve a three-day notice and file an eviction case. If a court decides the problem was not serious enough, or your notice or timing fell short, you can owe the full rent and be evicted. Keep every receipt.
Withholding rent	The DRE guide describes this as a remedy for serious defects that threaten health or safety.	The landlord can serve a three-day notice and file an eviction case. Judges rarely excuse all rent. The guide suggests setting the withheld money aside.
Moving out (Civil Code 1942)	After notice and a reasonable time, a tenant may leave a seriously defective unit and stop owing future rent.	The landlord may sue for more rent. Get an inspection and photos before you go.

Before using any option that means paying less than full rent, talk to a legal aid office or a tenant lawyer. In the Fresno area, Central California Legal Services offers free civil legal help to people with low incomes. Its legal advice line is (559) 570-1200, and its toll-free number is (800) 675-8001.

When dampness or mold is a health concern

Damp, moldy homes affect some people and not others. CDC and CDPH link indoor dampness and mold with stuffy nose, sore throat, cough, wheezing, eye irritation and skin rashes, and with asthma attacks and new asthma. CDPH says the more extensive the dampness or mold, the higher the risk. People with asthma or mold allergies can have severe reactions. CDC says people with weakened immune systems or chronic lung disease can get lung infections from mold. CDPH also names infants, young children and older adults as more vulnerable.

Talk to a clinician if:

symptoms last (CDC advises seeing a doctor for persistent symptoms), or you think they are linked to your home (CDPH advises consulting a medical professional);
you have asthma and an attack needs more medicine than your plan recommends, or symptoms are getting worse or not improving with treatment (MedlinePlus advises contacting your provider right away in these cases);
someone at home has a weakened immune system or chronic lung disease, and you want to know how to limit exposure and which symptoms to report;
you have a health condition and plan to clean mold yourself (EPA advises checking with a health professional first).

Tell the clinician when symptoms started and whether they change when you are away. If you have asthma, ask about a written asthma action plan. CDPH has said that no environmental test shows whether indoor mold is making toxins, and that blood or urine tests cannot confirm exposure to them, so be cautious about paid tests that claim to.

In California, if you have Medi-Cal and asthma, ask your health plan whether it offers "Asthma Remediation." This Community Supports service covers home changes that help prevent asthma attacks triggered by things such as mold, for example dehumidifiers, air filters, filtered vacuums and ventilation improvements. Not every plan offers it; the Department of Health Care Services (DHCS) Community Supports search tool shows what plans offer in each county. It does not replace the repairs a landlord must make.

For more on asthma symptoms, action plans and warning signs, see Understanding asthma.

If you clean a small patch yourself

EPA says you can usually clean a moldy area of about 10 square feet or less (roughly 3 feet by 3 feet) yourself. For larger areas, EPA points to more detailed cleanup guidance, and water damage from sewage calls for a professional. In a rental, larger repairs are generally the landlord's to arrange.

Photograph it first. Tell the landlord if it comes back.
Wear an N-95 respirator, gloves and goggles without vent holes.
Clean hard surfaces with detergent and water, and dry them. Never mix bleach with ammonia or other cleaners, because the fumes are toxic.
Do not paint or caulk over mold.
Do not run a heating or cooling system you think may be contaminated, and do not use ozone-producing "air purifiers" in occupied rooms.
Leave building materials such as drywall, ceiling tiles and carpet to the landlord. Tenants should not remove parts of the structure, and soaked porous materials may need to be replaced.

Sources

Civil Code § 1941.1 — California Legislature (reproduced by California.Public.Law, verified October 19, 2026), accessed October 21, 2026.
Health and Safety Code § 17920.3 — California Legislature (reproduced by California.Public.Law, verified October 19, 2026), accessed October 21, 2026.
Civil Code § 1941.2 — California Legislature (reproduced by California.Public.Law), accessed October 21, 2026.
Civil Code § 1941.7 — California Legislature (reproduced by California.Public.Law), accessed October 21, 2026.
Civil Code § 1942 — California Legislature (reproduced by California.Public.Law), accessed October 21, 2026.
Civil Code § 1942.4 — California Legislature (reproduced by California.Public.Law), accessed October 21, 2026.
Civil Code § 1942.5 — California Legislature (reproduced by California.Public.Law), accessed October 21, 2026.
Civil Code § 1954 — California Legislature (reproduced by California.Public.Law), accessed October 21, 2026.
Civil Code § 1950.5 — California Legislature (reproduced by California.Public.Law), accessed October 21, 2026.
California Tenants: A Guide to Residential Tenants' and Landlords' Rights and Responsibilities, 2026 Edition — California Department of Real Estate, RE 26 (Rev. 1/1/26).
Mold and dampness — California Department of Public Health, Indoor Air Quality, accessed October 21, 2026.
Mold or Moisture in My Home: What Do I Do? — California Department of Public Health information sheet, December 2015 (copy hosted by the City of Santa Clara).
A Brief Guide to Mold, Moisture and Your Home — U.S. Environmental Protection Agency, last updated February 18, 2026.
About Mold — Centers for Disease Control and Prevention, September 26, 2024.
Facts About Stachybotrys chartarum — Centers for Disease Control and Prevention, May 29, 2024.
Asthma in adults — MedlinePlus, National Library of Medicine, reviewed January 1, 2025.
Code Enforcement — City of Fresno, accessed October 21, 2026.
Code Enforcement FAQs — City of Fresno, accessed October 21, 2026.
Substandard Housing and Substandard Housing FAQ — Fresno County Department of Public Health, Environmental Health Division, accessed October 21, 2026.
Central California Legal Services — Central California Legal Services, accessed October 21, 2026.
Community Supports Search Tool — California Department of Health Care Services, last modified July 16, 2026.