Fire, Flood and Mold Risks in Los Angeles County Homes

A Year of Risks in Los Angeles County

Los Angeles County does not have one damage season. It has several that overlap.

Housing age adds another layer. Much of the county’s housing was built before 1980, and many homes still have original galvanized water pipe, cast iron drains and building materials that may contain asbestos or lead paint. That matters every time you open a wall after a leak.

Local conditions also vary a lot. A beach home in the marine layer fights damp closets and bathroom mold. A canyon home fights fire and mud. Read the sections that match where you live.

Wildfire Smoke and Ash

Even homes far from the flames can end up with ash on patios, in yards and inside. The January 2025 Eaton and Palisades fires showed how far ash and smoke can travel, and how much of it comes from burned homes and cars, not just brush.

Ash from burned structures can contain heavy metals, asbestos and other toxic materials. Treat it with care.

• Wear a well fitted N95 respirator, gloves, long sleeves and goggles when you clean it.
• Lightly mist ash with water, then scoop or wipe it up. Do not use leaf blowers, dry brooms or ordinary shop vacuums, which throw fine particles back into the air.
• Indoors, use a HEPA vacuum and damp cloths. Wash cloths separately or throw them away.
• Run a HEPA air purifier and replace the HVAC filter with the highest rated one your system can handle.
• Bag ash in heavy plastic bags. Do not wash it into storm drains.

For a home that burned or had heavy smoke and ash inside, do not do the cleanup yourself. Debris removal after major fires is often run through government programs, and smoke damaged homes need professional cleaning. Follow Los Angeles County Public Health guidance for your area, and check with your insurer before you throw away damaged items.

Burn Scars and Debris Flows

A wildfire changes the hillside above it. Burned soil can shed water almost like pavement, and the plants that held the slope are gone. When a storm hits a fresh burn scar, rain can pick up mud, rocks, ash and trees and send them downhill as a debris flow. These move fast, carry boulders and can bury cars and knock homes off foundations.

The risk is highest in the first few winters after a fire, and it can be triggered by a short burst of intense rain even when the total for the day looks modest.

• Find out whether your home sits below a recent burn area. The county and your city publish maps and alerts for burn scar zones.
• Sign up for county and city emergency alerts.
• Leave when an evacuation order is issued. Do not wait to see the mud. Debris flows can arrive with little warning, often at night.
• Do not try to stop a debris flow with sandbags. Sandbags help with shallow water at doors, not with a moving slope.
• After a flow, stay out until officials say it is safe. Mud can hide broken gas lines, downed wires and sinkholes.

Mud that enters a house is contaminated. Drywall, insulation and carpet it touched usually must come out, and this cleanup is usually a job for a restoration company.

Atmospheric Rivers and Hillside Drainage

Atmospheric rivers are long bands of moisture that can dump days of heavy rain on Southern California. Many homes here see little rain for months, so roofs, gutters and drains get ignored until the first big storm finds every weak spot.

Before the rainy season, usually by October, do a storm walk.

• Clean gutters and downspouts and make sure water leaves the house and the lot.
• Look at the roof. Tile roofs rely on the underlayment under the tiles, and it wears out in the sun long before the tiles do.
• Check flat roof drains and scuppers for debris.
• On hillside lots, clear terrace drains, concrete swales and down drains of leaves and silt. Blocked drains can send water over the slope face and start a slide.
• Look at retaining walls for clogged weep holes, bulges or new cracks.
• Get sandbags ready for low doors. Fire stations in the county and the City of Los Angeles often offer free sandbags during storm season, so check before you go.

Signs a slope may be moving include new cracks in the ground, walls or patios, doors that suddenly stick, tilting trees or fences, and water seeping at the base of a slope. If you see these during heavy rain, leave and call 911. Afterward, a geotechnical engineer should look at it.

Older Pipes, Slab Leaks and Sewer Lines

Many Los Angeles County homes built before the 1960s still have galvanized steel water pipe. It rusts from the inside, narrows over time and tends to leak at threaded joints. Signs include brown water when a tap first opens, low pressure at several fixtures and pinhole leaks.

Drain lines in older homes are often cast iron. It can crack, rust through at the bottom or develop scale that slows drains. In slab homes, a failing cast iron drain can leak under the floor for a long time before anyone notices. Frequent backups, a sewer odor or damp flooring near a bathroom are clues. A plumber can run a camera through the line.

Water supply lines in slab homes can also leak under the floor. Watch for a warm spot on the floor, the sound of running water with everything off or a jump in your water bill. Turn off all fixtures and watch the meter. If it still moves, call a leak detection specialist.

The sewer line from your house to the street is usually the owner’s responsibility. Tree roots often break into older clay and cast iron lines. If you get repeated backups at the lowest drain, have the line inspected before it backs up into the house during a storm.

Earthquakes, Gas and Water

A strong earthquake can break water lines, tip a water heater and crack gas lines. A few minutes of prep now makes the moments after a quake much safer.

• Strap the water heater. California law requires water heaters to be braced or strapped. Use two straps, one in the upper third and one in the lower third of the tank. Use flexible connectors on the water and gas lines.
• Find the gas meter shutoff. Keep a wrench near it. The valve is closed when the tang is crosswise to the pipe.
• Only shut off gas when needed. Turn it off if you smell gas, hear a hissing or blowing sound, or see the meter dial spinning fast. If you shut it off, only the gas company should turn it back on and relight appliances.
• Find the main water shutoff. After a quake, closing it can keep the water in your water heater clean for emergency use and stop a broken pipe from flooding the house.

After shaking stops, check for gas odor first. Then look for leaks under sinks, at the water heater and at toilets, and look for new cracks in ceilings. If you smell gas, do not use light switches, phones or anything that sparks inside. Leave and call the gas company or 911 from outside.

Asbestos and Lead in Pre-1980 Homes

Water and fire damage often means opening walls, ceilings and floors. In older homes, that can disturb hidden hazards.

• Asbestos may be in popcorn ceilings, older vinyl floor tiles and their adhesive, pipe and duct insulation, some plaster and joint compound, and old roofing. Materials from before about 1980 are the most likely to contain it.
• Lead paint is common in homes built before 1978 and most common in homes built before 1950. Sanding, scraping and demolition create lead dust that is especially harmful to young children and pregnant people.

Before you cut out wet drywall, scrape a water stained ceiling or pull up old tile, have suspect materials tested. Do not dry sand, scrape or sweep materials you have not tested.

For pre-1978 homes, the EPA Renovation, Repair and Painting rule requires contractors who disturb painted surfaces to be lead safe certified and to follow lead safe work practices. The South Coast Air Quality Management District also has its own asbestos rules for renovation and demolition, so ask any contractor how they handle testing and notification.

If a leak or fire has damaged materials that may contain asbestos, keep people out of the area and let a licensed asbestos contractor handle removal. Ask any restoration company whether it tests before demolition.

Renting and Hiring in Los Angeles County

If you rent, California law requires landlords to keep rentals habitable, including working plumbing, weather protection and freedom from dampness. California law also treats visible mold growth, beyond minor mold on surfaces that normally get wet, as a substandard housing condition. Tell your landlord about leaks and mold in writing, keep a copy and take dated photos. Landlords generally must give written notice before entering, usually 24 hours, except in an emergency. In the City of Los Angeles, the Los Angeles Housing Department handles rental housing code complaints. Elsewhere, your city’s code enforcement or the county can inspect. Tenant rights groups and legal aid can explain options like repair and deduct, which has strict limits.

When you hire, look up the contractor on the Contractors State License Board website. Confirm the license is active, the classification fits the job and the bond and workers’ compensation are current.

• For most home improvement contracts, California limits the down payment to 10 percent of the contract price or $1,000, whichever is less.
• After a declared emergency, California’s price gouging law limits many price increases to 10 percent.
• Be wary of anyone who knocks on your door after a fire or storm and wants payment or a signature today.

Use the directory to find a specialist near you for work beyond DIY.

Step by Step

1. Strap the Water Heater

   Install a seismic strap kit with one strap in the upper third and one in the lower third of the tank. Check that water and gas connectors are flexible.

2. Learn Your Shutoffs

   Find the gas meter valve and the main water valve. Keep a wrench at the gas meter and show everyone in the house how each one works.

3. Stock for Fire Season

   Keep well fitted N95 respirators, spare HEPA filters for your air purifier and the best HVAC filter your system allows. Set up emergency alerts on your phone.

4. Do a Fall Storm Walk

   By October, clean gutters and downspouts, check the roof and flat roof drains, and clear hillside swales and retaining wall weep holes.

5. Check Your Burn Scar Risk

   Find out whether your home sits below a recent burn area. If it does, plan how you will leave and go when an order comes.

6. Test Before You Tear Out

   Before removing wet or burned drywall, ceilings or flooring in a pre-1980 home, have suspect materials tested for asbestos and lead.

Mistakes That Make It Worse

• Using a leaf blower on wildfire ash. It spreads fine toxic particles into the air and into neighbors’ homes.
• Waiting to see mud before leaving a burn scar area. Debris flows move faster than people can run.
• Turning off gas after every quake. Only shut it off if you suspect a leak, because restoring it takes a utility visit.
• Scraping a water stained popcorn ceiling in an older home without testing it first.

Where You Live Matters