The first 48 hours
Water damage is unusual among household problems in having a published deadline. EPA and CDC both put it at 24 to 48 hours: dry it inside that window and, in most cases, mold does not follow. This page is that window, hour by hour, with the source for every step.
Two things that come before everything else
CDC: never turn power on or off, or use an electric tool or appliance, while standing in water — if you cannot reach the main switch from a dry spot, call an electrician. And if you smell gas or suspect a leak, turn off the main gas valve, open all windows and leave the house immediately.
The clock, in four stretches
- 0–2 h
Safety first, then the source
- If there is standing water and the main power switch is reachable from a dry spot, CDC says to turn the power off. If you would have to step into the water to reach it, call an electrician instead.
- CDC: never turn power on or off, or use an electric tool or appliance, while standing in water.
- If you smell gas or suspect a leak, CDC says to turn off the main gas valve, open all windows and leave the house immediately.
- Stop the water at its source if you can do so without entering standing water.
- 2–24 h
Water out, air moving
- CDC: clean up and dry out the building fully and quickly, within 24 to 48 hours of the flood.
- This is the part that takes equipment rather than effort: standing water has to come out before drying can start.
- If the water came from a sewer backup or from outdoors, CDC advises staying out of it, and wearing rubber boots, rubber gloves and goggles if you must enter.
- 24–48 h
The window is still open
- EPA: if wet or damp materials or areas are dried 24 to 48 hours after a leak or spill happens, in most cases mold will not grow.
- What matters now is whether materials are actually dry inside, not whether the surface feels dry.
- Anything that cannot be dried in this window is the decision to make here, not later.
- 48+ h
A different job now
- Past this point the question changes from drying to what has already grown.
- EPA puts the line at about 10 square feet: under roughly a 3 ft by 3 ft patch, in most cases a homeowner can handle the job; above it, the guidance is different.
- Water damage and mold are priced and done separately, which is why the two get quoted separately too.
Why the window closes
Nothing dramatic happens at hour 49. What changes is the balance of the job. In the first day or two, the problem is water that has not yet soaked into things that are hard to dry. After that, the problem is material that has been wet long enough to need removing rather than drying, and whatever has started growing in it.
That is why the two trades are priced differently. What restoration costs covers published national ranges for extraction and drying; mold is a separate job, and that is covered on water damage and mold.
What is worth photographing
Before anything is moved or dried, photograph the water and where it came from, with dates. An insurer and anyone quoting the work will ask for this first, and once a floor is dry there is nothing left to show. Keep receipts for anything you buy or pay for along the way.
What a policy actually covers is a separate question with a separate answer, and it depends on your policy rather than on the damage. That is covered on does insurance cover water damage.
If the water came from outside or from a sewer
Then this page is not the right one to follow on its own. CDC says nobody knows exactly what is in floodwater at any given point in time: it can carry human and livestock waste; household, medical and industrial hazardous waste; and coal ash waste containing arsenic, chromium and mercury. CDC's guidance is to stay out of the water, and, if you must enter it, to wear rubber boots, rubber gloves and goggles.
If your home has damage, CDC says not to reenter until it has been examined by a building inspector for safety, and to go back during daylight so you do not need lights. Sewage cleanup and flood damage restoration deal with those two cases specifically.
Questions people ask
Where does the 24 to 48 hour figure come from?
Two federal sources, independently. EPA: “If wet or damp materials or areas are dried 24-48 hours after a leak or spill happens, in most cases mold will not grow.” CDC: “Clean up and dry out your home fully and quickly (within 24–48 hours) after a flood.” Both are linked at the foot of this page.
The surface feels dry. Is it dry?
Not necessarily, and this is the most common reason a job comes back. Water moves into subfloor, insulation and wall cavities, and those dry far more slowly than the surface you can touch. What settles it is a moisture reading inside the material, not how the floor feels underfoot.
Can I turn the power off myself?
CDC draws the line at whether you have to step into the water. If there is standing water and you can reach the main power switch from a dry spot, CDC says to turn the power off. If you would have to enter standing water to reach it, CDC says to call an electrician instead, and never to turn power on or off or use an electric tool while standing in water.
What if I smell gas?
CDC is specific: turn off the main gas valve, open all windows, and leave the house immediately. Report it from outside. This is not a step to combine with anything else on this page.
What happens after 48 hours?
The question stops being “can this be dried” and becomes “what has already grown”. EPA puts a rough line at about 10 square feet: under roughly a 3 ft by 3 ft patch, in most cases a homeowner can handle it. Water damage and mold are separate jobs, priced separately, which is why they get quoted separately.
Where this comes from
- EPA — A Brief Guide to Mold, Moisture and Your Home — Where the 24 to 48 hour drying window and the 10-square-foot rule of thumb come from.
- CDC — About Mold — Federal guidance to clean up and dry out fully within 24 to 48 hours of a flood.
- CDC — Safety Guidelines: Floodwater — What floodwater can carry, and why the advice is to stay out of it.
- CDC — Safety Guidelines: Reentering Your Flooded Home — Power, gas and when not to go back inside.
- FEMA — National Risk Index — County-level flood, hurricane and riverine risk used on the city pages.