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Water damage and mold are the same problem at two different moments. In the first day or two you're dealing with water, and fast drying can prevent most of the mold. After that, you should assume some growth has started. EPA's guidance draws the line at 24 to 48 hours, and its disaster cleanup guide says that if a flooded home couldn't be dried in that time, you should assume mold is growing. Here's what to do in that window and after it, with the Nashville specifics.
Restoration companies sort water by contamination using three categories from the IICRC S500 standard. Category 1 starts from a sanitary source, such as a broken supply line or an overflowing sink with nothing in it. Category 2 carries significant contamination and could make someone sick, such as discharge from a dishwasher or washing machine or seepage pushed through a foundation wall. Category 3 is grossly contaminated: sewage, a toilet backflow from beyond the trap, and rising water from rivers or streams. The newer edition of the standard adds that time and temperature can change a category, so a clean leak that sits for days stops being clean. Our risk checker walks through this for your situation.
EPA's table for clean-water damage gives a material-by-material answer. Wet ceiling tiles and fiberglass or cellulose insulation are discarded. Carpet can sometimes be saved if the water is extracted and the carpet and subfloor are dried within 24 to 48 hours. Drywall can be dried in place only if it isn't swollen and the seams are intact. With floodwater the bar rises: the disaster guide says to throw out anything wet with flood water that can't be cleaned and dried completely within 24 to 48 hours. Flood-damaged drywall is commonly cut out to the waterline in two-foot steps so that half or whole sheets can go back.
The May 2010 flood showed how far water can reach in Davidson County. Records fell on Mill Creek at Antioch and at Woodbine, on Whites Creek in Bordeaux, on Browns Creek at the fairgrounds and on the Harpeth at Bellevue. Metro Water Services ran a buyout afterward with FEMA hazard mitigation grants: 267 homeowners were offered buyouts and 226 accepted, according to Metro's internal audit. Metro now mails flood-risk brochures to properties in or near mapped flood hazard areas and notes that flooding can happen outside them too. You can check your lot on the Metro Parcel Viewer or FEMA's flood maps. A standard homeowner's policy doesn't cover flood, which affects who pays for mold that follows a flood.
Metro Codes doesn't require a permit to tear out wet drywall, carpet and doors. It does require a building permit before new drywall goes up on a weather-damaged home, and before damaged electrical, plumbing or HVAC work is repaired. Licensed electrical and HVAC contractors pull their own permits, insulation goes back to code, and a framing inspection comes before the drywall. Codes advises that if you've hired a contractor, the contractor should pull the permit, because an owner who pulls it takes on responsibility for code compliance. More in the licensing and permits guide.
Sources: EPA and partner agencies, Homeowner's and Renter's Guide to Mold Cleanup After Disasters; EPA, water damage response table; IICRC S500 categories as reprinted in Restoration & Remediation and 2015 changes in Cleanfax; Alabama Extension, Drying Out After a Flood; NWS Nashville, May 2010 Flood and ten-year retrospective; Metro buyout audit; Metro Water Services, flood risk information and 2026 brochure; Metro Codes, permits for weather-damaged homes.
EPA advises drying materials within 24 to 48 hours. Its guidance also notes that mold can still appear on materials dried within 48 hours and does not always appear after 48 hours, so the window is a guide rather than a guarantee.
Yes. The IICRC S500 definitions place rising water from rivers or streams in Category 3, the most contaminated group, and Extension flood guidance calls it black water.
Metro Codes says no permit is needed for the demolition and clean-up, but a building permit is required before drywall is installed and before electrical, plumbing or HVAC damage is repaired.
We are a referral service and send nobody out ourselves. Leave your town and a line about what is going on, and a local, independent mold business will phone you to talk it through and quote. Water still running? Close the main shutoff or the fixture valve before anything else.