Mold After a Flood or Hurricane in Houston: What to Do and When
Updated October 7, 2026 · 2 min read
A timeline for the first 48 hours, first week and first month after flooding, plus what can be saved and what can't.
Houston has been through Harvey (2017), Imelda (2019), the 2024 derecho, and Hurricane Beryl (2024). Each one produced the same sequence: water in, a few days of hot humid weather, and mold in walls and ceilings people thought were fine. Speed matters, because the mold clock in a warm house starts within roughly 24 to 48 hours.
First 24 to 48 hours
- Safety first. Turn off electricity at the breaker if water reached outlets, and don't enter standing water. Floodwater can carry sewage and chemicals.
- Document. Photos and video of everything before you move or discard it. Call your insurance agent and, if you have it, your flood insurer.
- Stop new water. Tarp roof openings; fix burst lines.
- Remove standing water and start drying. Open windows only if outdoor humidity is lower than indoors (in Houston summers, often it isn't, so dehumidifiers beat open windows).
- Pull soaked contents out of the house: carpet, pad, furniture, mattresses.
First week
- Flood-contaminated drywall and insulation should come out. Cut drywall at least 12 to 24 inches above the highest water line and check inside the cavity with a moisture meter.
- Dry the structure with commercial dehumidifiers and air movers until moisture readings return to normal. Drywall and framing can look dry long before they are.
- Clean hard surfaces with detergent and water; disinfect non-porous materials that touched floodwater.
- Wear protection: N95 or better respirator, gloves, eye protection, boots.
What can be saved vs. what can't
| Usually salvageable | Usually discarded |
|---|---|
| Solid wood framing (after cleaning and drying) | Drywall and insulation soaked by floodwater |
| Tile, metal, glass, hard plastics | Carpet, pad, upholstered furniture |
| Concrete, masonry | Particleboard and MDF cabinets |
When mold appears anyway
If you see or smell mold after drying, or the affected area is 25+ sq ft, bring in a licensed assessor. Under Texas rules a protocol and clearance testing are required for projects of that size. Do not bomb the house with fogger products or paint over staining; both leave the source in place.
Insurance reminder
Standard homeowners policies typically exclude flood damage; that's what NFIP or private flood coverage is for. Mold coverage varies and is often capped. Document the date, source and extent early.
Health
If anyone in the household has asthma, a weakened immune system or is pregnant, keep them away from the work area. For the evidence on what mold exposure does and doesn't do to health, see Mold Macro.