Avoiding Mold Hazards in Your Flooded Home

Floods September 30, 2014 Print Friendly and PDF

A flood-damaged home requires special attention to avoid or correct a mold population explosion.  Mold is likely to multiply on materials that stay wet for more than two or three days. The longer mold is allowed to grow, the greater the hazard and the harder it is to control. So, as soon as floodwaters recede and it is safe to return, don’t delay clean-up and dry out. 

Take photographs to document damages for insurance purposes, and get started.  It is not wise to wait for the adjuster to see it in person. Most homeowner insurance policies do not cover mold damages or clean-up costs.

Mold and Health
Molds produce spores that float and spread easily through the air, forming new mold growths (colonies) when they find the right conditions – moisture, nutrients (nearly anything organic) and a place to grow.  

Although there is wide variation in how people are affected by mold, long term or high exposure is unhealthy for anyone.  Exposure to mold can trigger allergic reactions and asthma attacks, may suppress the immune system or have other effects.  Some types of mold can produce mycotoxins in certain conditions, which can be present in live and dead spores and fragments in the air.  “Black mold” is a misleading term since many types are black.

Mold testing is not usually needed and is rarely useful to answer questions about health concerns. If you see or smell mold, your time and money is best spent on immediate and safe remediation. Some insurance companies and legal services may require sampling as a form of documentation. Professional mold remediation contractors may test before and after clean-up to provide evidence of the clean-up’s effectiveness.

To Prevent Mold Growth

  • Remove wet carpeting right away.  It’s best to discard it, but if salvaged, quickly clean, disinfect and dry the carpeting with professional equipment or outdoors.  Never reuse flooded padding.

  • Cut away wet wallboard and remove all wet insulation right away – even if wallboard appears to dry. Wet insulation will stay wet far too long, leading to the growth of hidden unhealthy mold and decay fungi inside the walls. Fibrous insulations that have been wet also lose effectiveness.

  • Clean with non-phosphate detergents (any phosphate residue is mold food).  Rising flood water is likely contaminated with sewage, so cleanable materials should be disinfected.  If you disinfect, follow directions carefully and never mix bleach with ammonia or acids (vinegar). Disinfectants can kill molds, but do not prevent regrowth. (For more information, see article Steps to Restore Your Flooded Home.)

  • Do all you can to speed the drying of subfloors, slabs and wall framing before replacing insulation, wallboard and flooring. Use air conditioning or heaters, fans, and better yet, a dehumidifier. Water damage restoration contractors with special equipment (dehumidifying blowers) can provide the fastest drying.

  • Use a moisture detector to test the moisture content of studs and sheathing before replacing insulation.  Wood should drop below 20% moisture content by weight before you close the wall.

  • Do NOT use vinyl wallpaper.  That would prevent further drying to the inside.

Mold Removal Guidelines

To clean up mold, follow these steps and refer to more detailed information available online at www.epa.gov/mold.

Minimize Your Exposure During Clean-up
People are mainly exposed to mold by breathing spores or fragments, and can also be exposed through skin contact.  Wearing gloves and a respirator that can filter mold spores (N-95 or better) is recommended.

Isolate Work Area and Ventilate to Outdoors
Disturbing mold colonies can cause a massive release of spores, so seal off the contaminated area from the rest of the house.  If power is on, use a fan to exhaust air to the outdoors.

Remove And Discard  Moldy Materials
Remove, bag, and discard according to community guidelines porous materials that are moldy or sewage damaged. Porous materials include gypsum wallboard, insulation, plaster, carpet/carpet pad, ceiling tiles, processed wood products and paper. To minimize the spread of spores, cover the moldy material with plastic before removing and discarding it. Even if not moldy, all wet fibrous insulation and other materials that are unlikely to dry quickly should be removed and replaced.

Clean Surfaces
Surface mold on non-porous materials such as hard plastic, concrete, glass, metal and solid wood can usually be cleaned. Cleaning must remove, not just kill, the mold because dead spores can still cause health problems.

After cleaning, you may choose to use a disinfectant to kill any remaining mold.  In the case of sewage contamination, disinfection must be performed. On color-fast, non-metal surfaces, you may disinfect with a solution of 1/4 cup concentrated bleach per gallon of water or follow label instructions for the material to be disinfected. Do not use in the air system or on metals. Milder, less corrosive disinfectants include alcohols, commercial disinfecting cleaners and hydrogen peroxide. Always handle with caution, never mix bleach with ammonia or acids and test on a small area.

Speed Dry
Dry all wet materials as quickly as possible. Use air conditioning or heat with fans and dehumidifiers, if possible. New mold colonies can form in as little as three days if materials stay wet.  Wood and other materials that look dry can still be wet enough to support regrowth.

Remain on Mold Alert
Continue looking for signs of moisture or new mold growth. If mold returns, repeat cleaning and consider using speed drying equipment and moisture meters. Regrowth may signal that the material was not dry enough or should be removed. Rebuilding should wait until all affected materials have dried completely.

Do More Than Restore
You can reduce future damage and ordeal by restoring your home with flood resistant materials and elevating equipment where possible.  Consider ceramic or solid vinyl tile flooring and washable/dryable wall assemblies. The wall assemblies should have solid wood studs, plywood (no OSB), closed cell foam insulation, and paperless drywall finished with latex paint or removable wainscoting.

Also see Health Concerns in the Event of a Flood and Salvaging After Flooding.

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