After a wet winter, mold often shows up weeks after the storms are over: a musty closet, spots on a ceiling under the roof, or a dark patch behind a dresser on an outside wall. Mold needs moisture to grow, so the fix always starts with finding and stopping the water. This guide covers where to look in a San Pedro-area home, what you can safely clean yourself, and when to call a professional.
Where to look after the rain
- Ceilings and attics under roof valleys, vents, chimneys and skylights.
- Around windows and exterior doors, especially sills and the wall below.
- Closets and furniture on outside walls, where air doesn’t move and walls stay cold and damp.
- The crawlspace in raised-floor homes: standing water, wet insulation, or a musty smell coming up through the floor. See our mold prevention guide and moisture diagram.
- Garages and laundry rooms, where rain blows in under doors.
Small patches you can clean yourself
The EPA says most homeowners can handle a moldy area smaller than about 10 square feet (roughly 3 feet by 3 feet) themselves:
- Fix the water problem first, or the mold will come back.
- Scrub hard surfaces with detergent and water, then dry them completely.
- Throw out porous materials such as ceiling tiles and carpet if they’ve become moldy.
- Don’t paint or caulk over mold.
- Never mix bleach with ammonia or cleaners that contain it.
- Protect yourself: a well-fitted N-95 respirator, long gloves and goggles without vent holes.
Source: EPA: A Brief Guide to Mold, Moisture and Your Home.
When to call a professional
- Mold covers more than about 10 square feet, or keeps coming back after cleaning.
- The water was sewage or floodwater (the EPA says to call a professional for contaminated water).
- You suspect mold in the heating or air ducts. The EPA says not to run the system if you think it’s contaminated.
- You can smell mold but can’t find it; it may be inside a wall or under the floor. A mold inspection can find the moisture source.
- Anyone in the home has asthma, allergies or a weakened immune system.
Keep it from coming back
- Keep indoor humidity below 60%, ideally 30 to 50% (EPA). An inexpensive hygrometer shows you where you stand.
- Run bathroom and kitchen fans, and dry wet areas within 24 to 48 hours.
- Fix roof, window and plumbing leaks as soon as you find them, and keep gutters and downspouts clear.
Renters and insurance
Renters: tell your landlord about leaks and mold in writing right away; see mold in your rental for your rights and who to call. Homeowners: insurance usually treats sudden leaks differently from slow ones and from flooding; see our insurance guide before you file a claim.
Talk to a local mold inspection or removal company
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Sources checked October 31, 2026: U.S. EPA, “A Brief Guide to Mold, Moisture and Your Home.”