Floor removed and lower drywall removed in a flooded basement to allow dryout (C) Daniel Friedman How to Dry Out Your Building after a Flood, Hurricane, or other Disaster
Flood Damage Repair Guide FEMA/ARC expanded Step 4
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How to dry out & clean up a wet basement or flooded building: If your building has been flooded or wet from extinguishing a fire or from hurricane or storm, this article provides easy step by step procedures to salvage materials & contents from a wet or flooded home, drain water from the building walls & ceilings, then dry out the building.

We discuss what can be saved and what should be thrown away after flooding and we explain how & where to make openings to speed building dryout or to permt inspector for & prevention of mold contamination.

Our page top photo shows flooring removed and lower drywall removed to permit dryout of a wet or flooded basement in Poughkeepsie, NY.

Green links show where you are. © Copyright 2015 InspectApedia.com, All Rights Reserved.

Building Dry Out Procedures after leaks or flooding

Removing wet contents from a flooded building (C) Daniel Friedman

[Click to enlarge any image]

Article Contents

Flood Response Step 4: How to Dry Out a Flooded Building or Wet Basement after a Hurricane, Earthquake, Flood or Other Disaster - Drying out a Home after Flooding - Details

Floodwaters affect a home three ways:


  1. The water damages materials. Wallboard will disintegrate if it remains wet too long; wood can swell, warp, or rot; electrical parts can short out, malfunction, and cause fires or shock.
  2. Mud, silt, and unknown contaminants in the water not only get everything dirty; they also create a health hazard.
  3. Dampness promotes the growth of mold - any of about two hundred common fungi that can grow on everything. (You may hear some people refer to this as "mildew" but that's a technically incorrect term as mildew actually only grows on living plants. Details are at

The following steps work on all three of these problems. It is very important that they be followed in order.

Adapted and expanded from Repairing your Flooded Home, American Red Cross & FEMA & from additional expert sources.[1] NOTICE: neither the ARC nor FEMA have yet approved the additions & expansions we have made to the original document.

Rapid Building Dryout Recommendations Following Wetting, Flooding, Storm Damage

Rapid dryout of a building reduces the chances of an expensive mold cleanup cost added to the costs of existing water and flood damage. As we discuss at FLOOD-CAUSED MOLD, PREVENTION, ideally we dry out the building within 24 to 48 hours of its having become wet, or as soon afterwards as is safe and practical.

What is effective in rapidly drying out a building is a combination of the following steps:

  • Watch out: Make sure that the building is safe to enter. See BUILDING ENTRY for DAMAGE ASSESSMENT
  • Remove standing water using pumps, mops, shop vacs, preferably as soon as flood waters have subsided and the building has been found safe to enter. When the building is safe to enter, photo-document all inside (and outdoor) conditions and damage - information that may assist you in making any loss or insurance claims as well as in rebuilding planning.
  • Remove wet materials including carpeting & contents from the building, discarding, or piling up for removal outside items such as wet wall-to-wall carpets, flooded furniture, wet drywall.
    • Watch out: be sure to make a complete inventory, both by photographs and in writing in order to be able to provide accurate loss information to your insurance company.
  • Use a combination of dehumidifiers, fans, heat (or electric heaters if your building has power and your heating system is not ready to operate), and/or if weather permits, open windows to dry out the building rapidly.
  • If the heating system is operable or portable heaters can be safely operated, use heat to speed the dryout process but do not run warm air heat and do not run air conditioners if there is a risk that these systems may become mold contaminated
  • Also see
  • Tip on using cold temperatures to retard mold growth and gain flooded building cleanup time: mold experts (including the author) opine that if you cannot thoroughly dry out a building in 24-48 hours, the risk of serious mold contamination becomes significant. But in fact you may have more time and the risk of rapid mold contamination growth is certainly reduced in cold conditions. So if your building has been wet or flooded in cold or winter weather, leaving the heat off until you have removed standing water and are ready to begin demolition, dryout, and cleanup, may be a better idea. Be sure to see WINTERIZE A BUILDING to protect from freeze damage.

How to Lower the Humidity in the Building to Complete the Dryout Process

Everything will dry more quickly and clean more easily if you can reduce the humidity in the home. There are multiple ways to lower the humidity and deter mold growth, described just below.

But you’ll have to delay using some methods if you have no electricity. (Read Step 5 before you attempt to restore the utilities.)

How Dry is "Dry Enough" When Salvaging Building Contents or Preparing for Re-Painting?

[Addition by DF]

To avoid problems with paint failure or mold growth, moisture content in salvaged materials or building surfaces should be below 18%.

Watch out: a ceiling, floor or wall or item that feels "dry to the touch" may still have a high internal moisture content if the dryout process has not continued long enough, as may thick or soft goods.

You can use a moisture meter if one is available, set to its "wood" setting, to check moisture content. Details about moisture meters are at MOISTURE METER STUDY.

Also see MOISTURE CALCULATIONS and MOISTURE CONTROL in BUILDINGS. When using a moisture meter or even when just feeling surfaces for evidence of dampness, for a building or basement that has been flooded, remember to check the areas that are likely to be last to dry: lowest points, corners, intersections.

If you do not have a moisture meter to check the dryness of surfaces or materials allow extra drying time (days or more)

How to Dry Out Building Ceilings, Walls, Floors, General Water & Moisture

Building Dryout Method 1 - Open up the house / building

Flooded cabinets and drywall partitions (C) Daniel Friedman

If the humidity outside is lower than indoors, and if the weather permits, open all the doors and windows to exchange the moist q indoor air for drier outdoor air. Your body will tell if the humidity is lower outdoors.

If the sun is out, it should be drier outside. If you have a thermometer with a humidity gauge, you can monitor the indoor and outdoor humidity. On the other hand, when temperatures drop at night, an open home is warmer and will draw moisture indoors.

At night and other times when the humidity is higher outdoors, close up the house.

Open closet and cabinet doors

Remove drawers to allow air circulation. Drawers may stick because of swelling. Don’t try to force them. Speed drying by opening up the back of the cabinet to let the air circulate. You will probably be able to remove the drawers as the cabinet dries out.

Watch out: our photo (above left) makes plain that flooding soaked cabinets and wall partitions in this home. In the example shown, just opening cabinet doors to help dry-out the building is futile. Demolition is needed to

  1. remove all wet drywall and further drywall to a 24" clear margin above the highest wet or visibly moldy surface
  2. remove the countertops and cabinets, take them out of the building for inspection, and if salvageable, cleaning and sanitizing, else disposal

Use fans to speed building dry-out but watch out about running air conditioning or heating equipment in a flood-damaged building

Fans help move the air and dry out your home and adding heat or air conditioning can speed building dry-out. But don't rush to turn on any air handling system in the building before considering the following warnings:

Watch out: Do not use central air conditioning or the furnace blower if the air handler ducts were under water. They will blow out dirty air, that might contain contaminants from the sediment left in the duct work.

Watch out: Do not use air conditioners, central air conditioning, nor warm air heating systems to speed building dry-out if the building is mold contaminated, unless you also plan to later completely clean and replace those components. Doing so will assure that the air handler, blower assembly, and duct work become mold contaminated.

If ductwork is uninsulated metal the ducts can be cleaned. Clean or hose out the ducts first. Insulated ductwork that has been flooded should be replaced or if insulation can be replaced separately it may be possible to salvage some duct components.


Building Dryout Method 2 - Run dehumidifiers To Speed Dry-Out of a Flooded or Wet Building

Dehumidifiers and window air conditioners will reduce the moisture, especially in closed up areas.

Building Dryout Method 3 - Use desiccants ???

Desiccants (materials that absorb moisture) are very useful in drying closets or other enclosed areas where air cannot move through.

Desiccants like those listed below are usually available at hardware, grocery, or drug stores.

  • Chemical dehumidifier packs used for drying boats and damp closets.
  • Cat litter made of clay.
  • Calcium chloride pellets used for melting ice in the winter. Hang pellets in a pillow case, nylon stocking, or other porous bag. Put a bucket underneath to catch dripping water.

Close the closet or area being dried. Be careful. Calcium chloride can burn your skin. It will also make the air salty, so do not use this product near computers or other delicate equipment. . Call a contractor.

Watch out: in our OPINION (InspectApedia) desiccants recommended in the original ARC/FEMA flood repair guide are a completely ineffective "band-aid" approach to drying out a home following flooding. The level of water and moisture far exceed the capacity of cans or piles of desiccants and worse, the rate of dry-out will be so slow that the risk of further water damage and mold contamination will be increased.

Building Dryout Method 3 - Hire a Flood Damage Restoration Contractor

There are contractors who specialize in drying out flooded buildings. They have large fans and dehumidifiers that can dry out a house in a few days. Look in the yellow pages under Fire and Water Damage Restoration or under Dehumidifying.

Be careful about contractors who inflate prices after a disaster and about out-of-town contractors who inflate prices after a disaster and about out-of-town contractors who request payment in advance. Be patient. Drying your home could take several weeks. Until your home is reasonably dry, damage caused by mildew and decay will continue. The musty odor will remain forever if the home is not thoroughly dried out well.

How to Sort Out Building Contents and Discard Debris Following a Flood, Fire or other Disaster

You have three types of contents that should go to three different places:

  1. items you do want to save
  2. things you don't want to save - items to be discarded (but not garbage)
  3. garbage

Things you do want to save

Move these to a safe, dry place, such as the second story or outside. The longer they sit in water, the more damaged they become. In some cases, you may only be able to move them to a dry or clean room in the same building while you clean the other rooms.

Watch out: leaving soft goods (that are costly or difficult to clean) in a mold-contaminated area means that those items are likely to need extra (and more expensive) cleaning before they can be returned to use.

Don’t leave wood furniture in the sun where it will warp as it dries.

To save an area rug, lay a sheet or some other material on top so the colors will not bleed. Clean it promptly.

For a detailed procedure on sorting and salvaging (store, clean, re-store) building contents following a flood, mold contamination, sewage backup or storm damage, see SALVAGE BUILDING CONTENTS.

Excerpts from that deatiled article are included just below.

How to Handle Things you don’t want to save

Flooded mattress (C) Daniel Friedman

Put things you don’t want to save outside to dry until the adjuster comes to confirm your losses.

Take pictures or videotapes and list each item for the record.

If you are not sure whether to throw something out, decide whether it is worth salvaging by checking the information in Step 6.

Garbage Items & Garbage Disposal

Get rid of food and anything else that could spoil or go bad immediately. Don’t let garbage build up.

Garbage piles will cause yet another health hazard by attracting animals and insects.

If your insurance adjuster has not come, tell your agent or adjuster that you need to get rid of potential health hazards. That person will tell you

Items Soaked by Floodwater

Flood damaged upholstered chair with severe mold contamination (C) Daniel Friedman\

Usually these items should be thrown out after wetting or a flood

Mattresses, pillows, foam rubber, large carpets, carpet padding, upholstered couches and chairs, books, paper products.

These items should always be thrown out after wetting or a flood

Food, cosmetics, medical supplies, stuffed animals, baby toys

Watch out: Don’t take chances with frozen food if electricity went off unless food is still thoroughly frozen and contains ice crystals. As a rule, food will remain frozen for up to three days in a closed freezer without power. Don’t refreeze thawed food. However, you can cook and then freeze raw meat that was partially thawed and then refreeze it.

Questions about the Safety of Your Food? Call the USDA Food Safety Hotline: 1-800-535-4555 Professional home economists will answer your questions from 10 a.m. to 4 p.m. eastern time, Monday through Friday. Professional home economists will answer your questions from 10 a.m. to 4 p.m. eastern time, Monday through Friday.

Then throw the stuff out, preferably in sealed plastic garbage bags.

How to Dispose of discarded items properly after a flood, hurricane, fire or other disaster

Flood damaged building contents & debris piled outside for garbage pickup (C) Daniel Friedman

Do not burn or bury them. There will usually be more frequent garbage pickups after a flood. Your local TV and radio stations will have announcements concerning trash pickup schedules and drop-off sites.

Framing and structural components can be kept

Unlike wallboard, wet studs and sills that are touched by floodwaters do not need to be thrown out.

Interior Hollow-Door Doors, Trim & Similar Items are usually Thrown Out

Our photo of floor baseboard trim exploration (below left) shows what happens when trim is left in place at the bottom of a wet floor. Better would have been to remove the trim and the bottom 12-inches of drywall to dry and inspect the wall cavity.

Photo of mold on the closet interior side of a hollow core hanging bypass door  (C) Daniel Friedman Photo of mold on the closet interior side of a hollow core hanging bypass door  (C) Daniel Friedman

At above right we show the right way to handle trim in a flooded building - remove it and pile it with site trash to be removed - as a first step in addressing wet walls and wall cavities (discussed below).

Photo of mold on the closet interior side of a hollow core hanging bypass door  (C) Daniel Friedman

Hollow wood and plastic or vinyl doors usually have cardboard spacers in the middle that lose their shape when wet.

Generally, hollow-core doors come apart after they are flooded sand need to be replaced.

How to Drain Ceilings & Walls after a Flood or Similar Soaking Disaster

Once building contents have been cleared outside for salvage & storage or for disposal, the next step in cleaning and repairing a soaked or flooded building is to get the water out of the ceilings and walls. How you drain and dry your ceilings and walls depends on what they are made of.

Ceiling inspection & draining after a fire, flood, hurricane, or other disaster

Check for sagging ceilings. Drain them carefully as shown in Step 2. If the floodwaters went above your ceiling, you should replace it if it is made of wallboard. A plaster ceiling will dry eventually, but if it has too many cracks or sags, you will have to tear it down and replace it. Remove any wet insulation in the ceiling to allow the joists to dry.

Wall inspection & draining after a fire, flood, hurricane, or other disaster

Remove water trapped within your walls. To check for water, take off the baseboard. Stick an awl or knife into the wall about 2 inches above the floor (just above the 2 X 4 wood sill plate). If water drips out, cut or drill a hole large enough to allow water to drain freely. (Use a hand or cordless drill or saw to avoid shock.) If you are going to replace the wallboard anyway, you don’t have to be neat: use a hammer to knock out a hole.

If your walls are plaster, a knife won’t penetrate them. Drill a hole above the sill plate to drain the water. (Use a hand or cordless drill to avoid shock.) Do not use a hammer or chisel on plaster because the plaster could shatter.

Draining walls with metal sill plates

Photo of Moldy drywall in a basement following a modest 6 inch flooding event

In a newer home, you may have metal sill plates. A metal sill acts as a trough at the bottom of the wall cavity. Drill a hole at floor level to drain the water, using a hand or cordless drill.

Repeat the process to drain all the wall cavities. Depending on the spacing between studs in your walls, make a hole every 16” or every 24”. Watch out for the wiring which is usually at the same height as your electrical outlets. If there is wet insulation, you will have to remove the wallboard in order to take out all the insulation.

Below at How to Dry & Restore Ceilings & Walls we discuss in detail the wall cavity mold contamination and floor damage that occurred in this NYC apartment as water traveled throughout the building floor in channels formed by metal wall partition sill plates.

What to do with Building Insulation that has Been Wet by Flooding, Fire Extinguishment, Hurricanes, or other Disasters

There are 3 main types of insulation and each reacts differently to floodwaters.

Foam Building Insulation Products & Flood or Water Contamination, Damage, Wetting

Styrofoam insulation [and similar foam board or sprayed-in-place foam building insulation] survives best; it may only need to be hosed off.

Watch out: open cell foam board or spray foam insulation that has been contaminated by flood waters (e.g. containing sewage pathogen s) cannot be effectively cleaned by hosing off or washing; such materials should be removed, the building cavity cleaned and sanitized, and when dry, re-insulated as part of the building restoration procedure.

Fiberglass Building Insulation & Flood or Water Contamination, Damage, Wetting

Watch out: original FEMA/ARC advice about wet fiberglass insulation stated:

Fiberglass batt or roll insulation should be discarded if they are muddy. f soaked by clean rainwater, remove them so the rest of the wall can dry. They can be put back in the wall, but it will take a very long time to dry.

That view about fiberglass insulation is not correct and is risky advice. Fiberglass insulation that has been wet, even if it looks "clean" is highly prone to developing hidden mold contamination. The potential cost of having to demolish and rebuild insulated walls and ceilings in which contaminated fiberglass batts were used far exceeds the cost of throwing away and replacing suspect fiberglass insulation. Our [DF] opinion is that you should never re-use soaked fiberglass building insulation. Details are at FIBERGLASS INSULATION MOLD.

Fiberglass Building Insulation & Flood or Water Contamination, Damage, Wetting

Watch out: original FEMA/ARC advice about wet fiberglass insulation stated:

Cellulose (loose or blown-in treated paper) insulation will hold water for a long time. It can also lose its antifungal and fire retardant abilities. Therefore, flooded cellulose insulation should be replaced.

We agree that flooded cellulose insulation should be replaced, both because of the very long dry-out time that delays building repairs and because of the risk of lost fire-retardant properties. But any type of building insulation that has been wet by floodwaters, likely to contain sewage or pathogens, should be disposed-of and the building cavities cleaned and sanitized before rebuilding.

For a complete guide to the identification and properties of all types of building insulation, see INSULATION IDENTIFICATION GUIDE

How to Treat Wood Framing or Subflooring Flooding that has Been Wet by Flooding, Fire Extinguishment, Hurricanes, or other Disasters

Watch out: ARC/FEMA's original advice for flooded buildings stated:

If allowed to dry naturally, wood will generally regain its original shape.

It is correct that wood framing will remain substantially the same size and shape when dried after a single event flood or wetting event unless severe warping occurs. But this is not true of subflooring in many installations where we find that the subflooring swelled, arched, and separated from the floor framing. And as we discuss below at How to dry the floor following a fire, flood, hurricane or similar disaster, it is absolutely not true for finish flooring of wood or most wood laminate or engineered wood floor products.

ARC/FEMA's original advice for flooded buildings continues:

Different layers of laminated wood, such as plywood, may dry at different rates, causing the layers to separate. Some contaminants will stay in the wood pores after it dries, but not as much as stays in flooded wallboard. Wood studs and sills will be covered by new wallboard and painted, so they are well removed from human contact. Therefore, wet wood studs and sills do not need to be replaced if they are allowed to dry properly.

We agree completely that wood framing in flooded buildings does not need to be replaced and thus should not be replaced unless it is rotted or otherwise damaged so that it cannot perform its structural function. But in a flooded building, before covering floor framing with new subflooring on top or with a new ceiling (for the floor below), if the floor structure was wet by floodwaters it should be cleaned and sanitized.

For more detailed help about fungicidal or sanitizing sealant coatings that can help reduce moisture uptake and mold growth in restored buildings after wetting or a flood see MOLD SPRAYS, SEALANTS, PAINTS

Black cosmetic mold - harmless (C) Daniel Friedmanb

Watch out: also for contractors who may propose costly cleaning and sanitizing of "black mold contaminated" framing lumber that may have been in that state, and may contain only harmless mold that has been present since original construction.

While flooded framing of walls, ceilings or floors may need to be cleaned and sanitized if contaminated by floodwaters, in some cases the extra cleaning (media blasting, sanding, scraping) proposed for what is really cosmetic mold, are probably not necessary.

See Black cosmetic mold for details.

How to Dry & Restore Ceilings & Walls after a fire, flood, hurricane, or other disaster

Drywall or Wallboard Affected by Flooding

Photo of Moldy drywall in a basement following a modest 6 inch flooding event

Most ceilings and walls are covered with wallboard, especially in newer homes. Wallboard will act like a sponge, drawing water up above the flood level. It becomes very fragile if it stays wet for long and will fall apart when bumped. When the wallboard finally dries, there will still be mud and contaminants dried inside.

Wallboard that has been soaked by floodwater presents a permanent health hazard. Therefore, this article series recommends that you remove and throw out flooded wallboard.

Watch out: original ARC/FEMA advice stating:

On the other hand, if the wallboard was soaked by clean rainwater, it can be dried in place with plenty of fresh air moving through the area.

is risky advice because of the high risk of mold growth in un-treated building ceiling, wall, or even some floor cavities. Below at How to Dry & Restore Ceilings & Walls we give better advice on how to inspect and where appropriate, remove wet drywall or wallboard, insulation removal, and how to clean & inspect building cavities for contaminants.

Mold contaminated wall cavity (C) Daniel Friedman

Flood soaked wallboard is usually removed and thrown away. Plaster and paneling can often be saved, but you still need to get air circulating in the wall cavities to dry the studs and sills. Different approaches are used for different materials.

Drywall or Wallboard recommendations for demolition/replacement after a fire, flood, hurricane, or other disaster

If floodwaters soaked the drywall or wallboard four feet above the floor or more, you should take down all the wallboard and replace it. If the water level was less than four feet deep, remove the lower four feet of wallboard. You can fill the gap with 4’ x 8’ sheets installed sideways.

Watch out: original ARC/FEMA advice for handling styrofoam-insulated drywall covered walls stated:

If you have Styrofoam insulation—or no insulation—and the wallboard was soaked with clean rainwater, you can dry the walls without removing the wallboard using the technique explained below for plaster walls. But you will need to remove wet insulation if it is not Styrofoam.

We advise against this advice which failed to recognize that any building wall or ceiling covered by drywall (wallboard) that has become wet is almost certainly going to develop severe mold contamination inside the cavity on the cavity side of drywall and very often as well on the surfaces of wood framing and exterior wall sheathing.

Our photo (above left) illustrates a severe and highly toxic mold contamination found inside an "apparently clean" wall on the upper floor of a Manhattan apartment whose floors had been wet from a plumbing leak in a different area more than 40 feet away. Water traveled inside the wall cavity (in the upturned metal stud used as a sill plate for internal wall partitions), leading to a large Memnoniella echinata mold contamination. You can just see the black mold growth on the opposing side of drywall exposed at our test cut made just above floor trim in this wall. Lifting the laminate flooring discovered additional contamination needing cleaning below the floor as well.

How Much Drywall Should be Removed Following Flooding, Water Damage, or Wetting or Mold Contamination?

Large test cut to explore wet wall (C) Daniel Friedman

Our larger wall test cut shown at left was made following observation of a very small amount of surface mold on the exterior or room side of the drywall. Unable to explain why mold was growing in this location we opened the wall to find a leaky plumbing drain pipe.

For detailed help and more examples of when, where, how & why to make test cuts in walls or ceilings see PHOTO GUIDE to FIND HIDDEN MOLD

Any drywall-covered walls or ceilings that have been wet should be handled by removing all wet or visibly water-stained or visibly moldy drywall and the insulation, if any, in that building cavity. Continue removing drywall until you have provided at least a 24-inch margin of clean, dry, un-stained materials.

Slight increases in the amount of drywall to be removed in a wet or flooded building can actually save labor cost & speed reconstruction

For additional cost-savings in time and labor, remove additional drywall or wallboard to reach either:

  • the center of a vertical stud or horizontal ceiling joist to which the edge or replacement drywall can be nailed or screwed


  • an open space that is in multiples of 12-inches, so that you minimize the waste of drywall cutting, installation, and taping during building restoration

Plaster walls & ceilings recommendations for demolition/replacement after a fire, flood, hurricane, or other disaster

How to Handle Plaster Ceilings or Walls Affected by Flooding or Wetting Disasters

Plaster will survive a flood better than wallboard.

Watch out: original ARC/FEMA advice stating

Plaster wall or ceiling coverings should not have to be replaced but it will take a very long time to dry. Sometimes the plaster will separate from the wood laths as it dries. Then the wall will have to be removed and replaced.

might be risky advice because we find that although plaster does not support mold growth as readily as drywall or "wallboard, there is still risk of mold growth in insulation and in or on surfaces of in un-treated building ceiling, wall, or even some floor cavities. We also find that mold growth is readily supported in paint coating drywall surfaces.

Below at How to Dry & Restore Ceilings & Walls we give better advice on how to inspect and where appropriate, remove sections of plaster-covered walls or ceilings, insulation removal, and how to clean & inspect building cavities for contaminants.

Mold in plaster wall cavity (C) Daniel Friedman

Watch out: original ARC/FEMA advice for handling plaster walls or ceilings stated:

If the plaster or wallboard is clean and in good shape, you can drill or cut ventilating holes in each wall cavity. Place holes low enough so they will be covered by the baseboard after the wall dries out. Open up the wall on both sides of interior walls. For exterior walls, drill or cut holes on the inside of the house. However, if there is wet insulation, you will have to remove the plaster or wallboard in order to take out all the insulation.

This is risky advice. Our field and forensic lab experience [DF] confirm that plaster is more resistant to mold growth than drywall, paneling, or similar materials.

However we have on occasion found significant mold contamination on wood surfaces in the previously wet wall or ceiling cavity regardless of the wall or ceiling covering material. Our photo (left) illustrates some interesting mold and fungal growth in the wall cavity of a plaster-covered interior where there had been plumbing leaks.

Now the risk of mold growth in any building cavity is significantly increased when the cavity has suffered leakage over a protracted interval compared with a brief (if dried quickly) single event. But in any case, the risk of problem mold growth and thus very costly future new demolition, cleaning, and restoration, is significant enough that a better approach includes these steps:

  • For uninsulated building cavities, cut and remove no less than 12-inches of plaster at the floor and ceiling level of walls or at the ceiling-wall margins if the plaster ceiling was wet. Use fans, heat (if possible) and dehumidifies to speed building dryout including of the opened wall and ceiling cavities.
  • For insulated building cavities, cut and remove enough plaster wall or ceiling material in continuous strips along the full length of the wall or ceiling at both floor and wall (wall cavities) or the full ceiling perimeter (ceilings) to permit removal of all wet or potentially wet and contaminated insulation.

Wall test cut for mold inspection (C) Daniel Friedman

  • In either case, when the wall and ceiling cavities are thoroughly dry and provided inspection confirms no problem mold growth, you can proceed with reconstruction. The cavity center will be last to dry so consider several small 2" x 4" test openings in locations to permit inspection and moisture testing.

    Our photo (left) illustrates an easy method for making small, easily-patched inspection openings in building walls or ceilings. In addition to inspecting the wood surfaces in the wall cavity, inspect the cavity side or "back side" of the test plug cut from the wall.

    Look for evidence of floodwaters (contaminated by sewage) and mold.
  • For building exterior walls, top floor ceilings, or other building cavities where insulation is desired, and where you have successfully left plaster ceiling or wall coverings in place, you can re-insulate using blown-in cellulose or foam insulation products.

Concrete block cavities & draining floodwaters

The cavities in a concrete block wall will drain on their own. The water will not damage the concrete like it will wood or wallboard.

Wall covering (wallpaper) dryout following flooding?

Mold behind wallpaper (C) Daniel Friedman

Vinyl wall covering seals the wall and prevents drying.

Watch out: The original ARC/FEMA advice offered this:

Wallpaper paste is a favorite home for mold and mildew. For these reasons, you should remove all wall covering that got wet and throw it out. (If vinyl wall covering is loose on the bottom, you may be be able to save it by pulling it off the wall up to the flood level.

FEMA/ARC's original advice to clean and reapply wallpaper after everything dries is an error if the wall was actually exposed to flooding (as opposed to high indoor moisture). Walls that have been flooded will require at least partial demolition.

Therefore, simply pulling off lower sections of wall coverings up to the flood level is dangerous advice.

Follow the drywall or plaster wall post-flood dryout, cleaning, and recovery advice described above.

However there are cases where limited wallpaper removal (and drywall removal) are appropriate, such as below a leaky window sill shown in our photo at above left.

Paneling treatment following a fire, flood, hurricane or similar disaster

Mold behind wall paneling (C) Daniel Friedman

Watch out: the original ARC/FEMA advice for handling wall paneling after a flood stated:

Carefully pry the bottom of each panel away from the wall. Use something to hold the bottom away from the sill so the cavities can drain and dry out.You may be able to nail wall paneling back into shape after they and the studs dry out.

Do not even consider simply following this bad advice.

Our field and laboratory tests confirm that the cavity side of wood type and vinyl wall coverings are very conducive to mold growth in buildings that have been wet or even just exposed to very high humidity.

Our photo at left illustrates a common situation. This basement was exposed to a single event wet-floor "flood" due to a burst drain pipe almost twenty years ago. Water was removed from the floor within 24 hours, and there was almost no visual evidence of a mold problem in the finished basement. But some building occupants experienced severe asthma attacks on entering the basement area or simply when standing at the top of the basement stairs. Our air, dust, and surface tests led to investigating the wall and wall cavity, for which this first inspection point produced the results you can see in our photo.

  • If a building wall cavity has been flooded to any depth whatsoever or exposed to wet conditions the wall paneling should be removed completely, any drywall behind the paneling should be removed in accordance with our drywall handling recommendations above, and the exposed wall cavity cleaned, dried, and sanitized.
  • We agree that if you get to paneling in time (before it has delaminated, warped, disintegrated due to water damage) it may be feasible to remove, dry, and clean the material for salvage and re-use - on occasion. Be sure to inspect the paneling front and back sides (wall cavity side) for mold growth and contamination.
  • Also inspect the wall cavity for mold contamination. If the paneling was not badly water damaged it may be possible to clean and sanitize it and nail it back in place. If there is or was wet insulation, you will have to remove the paneling and to take out all the insulation.
  • Modern fire codes require that wood type wall paneling be installed over a layer of drywall. If original construction omitted the drywall, as may be found in some older homes, you should install drywall (and depending on climate, insulation) in walls before restoring the final wall covering.

How to dry the floor following a fire, flood, hurricane or similar disaster

Air needs to circulate around flooded floors so they can dry out. This means removing the floor covering. Because floodwaters contain mud and dirt, most soaked floor coverings should be thrown away. Keep a piece of all discarded floor covering so the adjuster can tell its value.

Air needs to circulate below the floor to dry it out. If the crawl space of your home is flooded, pump it out. Remove any plastic sheets, vapor barriers or insulation from underneath the floor. (Be sure to replace them when the floor and foundation are completely dry.)

If a home with a basement was flooded over the first floor, remove finished basement ceilings, or cut or drill holes between all the joists to allow circulation. Don’t cut or drill near electric lines or pipes. You have now reached the stage where no more damage should occur to your home. Exterior holes have been patched, the utilities have been turned off, and the drying process has started. It may take days or weeks, depending on the humidity, for all the wood to dry out. You can do Steps 5, 6, and 7 while the home is drying. However, do not start Step 8, Rebuild and Floodproof, until the home is completely dry.

Advice for Cleaning & Salvaging Carpets & Other Floor Coverings that have been Wet by a Burst Water Pipe, Floodwaters, or other Disaster

Wet wall to wall carpeting and padding should be removed (C) Daniel Friedman

  • Small throw rugs can be saved and cleaned in a washing machine.
  • Indoor-outdoor carpeting can be removed from the building, hosed off and hung up to dry.
  • Carpeting & large rugs and those with foam backing should be discarded. After getting wet, wall-to-wall carpeting usually will not return to its former size and has to be thrown away. Therefore, make the job easier by cutting it in strips and discarding it in pieces that are small enough to be carried.

    Valuable carpets: usually only valuable carpets are worth the cost of professional cleaning. If you expect to preserve a valuable carpet it should be transported to or by the professional cleaning company promptly. Carpets wet by unsanitary flood waters or a burst sewer pipe should be thoroughly sanitized as part of the cleaning and dryout procedure.

    Watch out: Be sure to tell your carpet cleaner what the carpet has been exposed to - both to protect the workers from possible harm and to assure that proper handling and cleaning are performed. Don't leave a valuable but wet carpet rolled-up and stored for days - you are may find that the carpet will be destroyed by running dyes and colors, and you risk a badly mold-contaminated carpet that will be difficult to clean and restore.

    Watch out for the tack- down strips along the wall; they often have nails sticking up to hold the carpet down. Cutting or scratching yourself on a rusted or flood-water-contaminated carpet tack strip is asking for an infection.
Photo of mold and mushroom fungal growth on wall to wall carpets and wall trim (C) Daniel Friedman
  • Wall-to-wall carpeting handling after soaking or flooding:

    Watch out: Original ARC/FEMA advice offered this:

    A wall-to-wall carpet that was soaked by clean rainwater can be left in place and dried.

    In our experience wet wall to wall carpeting along with the padding beneath it most often forms a mold contamination reservoir. Most insurance companies currently agree that widely (over large areas) soaked wall to wall carpeting should be removed, along with its padding, and later replaced.

    Our photo (above left) illustrates what happened when a wet carpet was "dried in place" in a home.

    Rarely in nearly 30 years of field inspection and forensic lab testing have we [DF] found a carpet wet by burst pipe or roof drainage that had been left in place after soaking and that was not mold contaminated.

    We agree that if only a small area of wall to wall carpeting has been wet by clean water - such as from a burst water supply pipe) it is often possible to dry and retain the carpeting.

    For detailed information about wet or moldy or smelly carpets or carpeting & carpet padding see
  • Floor tiles, vinyl or sheet flooring: remove tile, vinyl, and linoleum flooring should be removed if it is warped, loose, or has a foam rubber pad (which should be thrown away).

Wet Wood Floor Dryout & Preservation - what to expect

Wood generally has some moisture content, but a flood can bring increase the moisture content of wood up to 30 percent or above. This causes swelling.

Watch out: The original FEMA/ARC comments about wood returning to its original size and shape after flooding are a bit optimistic when it pertains to wood floors. A wood floor that has been soaked can be salvaged if it can be cleaned and dried quickly - in hours. If you can dry the floor quickly enough some cupping will remain but the floor may be usable (photo, below left). But if days pass the wet wood floor is likely to swell, buckle, and will not be repairable without demolition and at least partial replacement (photo, below right).


Buckled ruined wet wood flooring (C) Daniel Friedman Buckled ruined wet wood flooring (C) Daniel Friedman

Salvage Kitchen & Bathroom Countertops & Cabinets

To salvage cabinets and counter tops that have not been badly water-damaged but that were mounted in a room that was soaked by flooding, fire extinguishment, storm damage or similar events, we [DF} find that you will need to remove wall mounted cabinets (on walls that were wet) and floor mounted cabinets (on floors that were soaked or flooded) to permit the cabinets to be properly dried and cleaned.

Photograph of inspecting below a bath vanity for hidden mold. Photograph of inspecting below wallpaper for hidden mold.

If there has been protracted leakage or spillage under built-in cabinets such as bath vanities, there may be a mold cleanup job under or behind these components.

Study the building carefully to decide on the building points at most risk of having been wet from leaks due to construction details or other site observations. That's where one would make a test cut.

Reader Question: Hurricane Sandy Flood Damage Cleanup: do white deposits on our walls after flooding mean that further cleanup and dryout are needed before we can put back insulation, drywall & trim in our home

We live in New Jersey where we had 2 feet of [salt water] brine in our living space. I removed 4 feet of Sheetrock and insulation from exterior walls. I left the interior walls for 4 weeks to see if mold had grown. Well it seems like white mold has paid us a visit. I enclosed photos.

Do you think it is dangerous to leave or should I bite the bullet and cut all the interior walls as well? Thanks for your advice. W.K. - 11/28/2012

White deposits in wall cavity oaked by salty floodwaters from Hurricane Sandy 2012 (C) Daniel Friedman White deposits in wall cavity oaked by salty floodwaters from Hurricane Sandy 2012 (C) Daniel Friedman

Reply: some warnings about mold or effloresence & adequacy of cleanup and dryout after flood damage

Of course I'm sorry to read of the flood, but not surprised given the extent of flooding caused by Hurricane Sandy in 2012.

Kudos to you if you were able to remove wet materials and drywall quickly enough to prevent more extensive water or mold or sewage damage to the building. In the case of hurricane Sandy we got a small break in that cold weather after the storm may have helped retard mold growth in buildings that could not be dried out in the recommended 24-48 hours. And "dried out" means really dry, not leaving tings mostly dry but with some wet spots.

Your photos were a bit blurry, so I'm not sure what we were looking at. It may be you are seeing effloresence, not mold. See EFFLORESCENCE, Salts & White / Brown Deposits for help in recognizing effloresence.

I don't have nearly enough information to offer much personally-tuned advice, bur if specific questions arise just ask and I'll try to assist.
Other than that, and addressing more of your question, one of the worst mistakes I've seen people make is to put the house back together before making sure the building cleanup is complete and adequate and that the building is really dry, including more subtle spots such as behind trim that should have been removed, or in insulation that was wet (and is at high risk of mold contamination)

So the white stuff you saw, even if it is effloresence, not mold, is an important clue that needs investigation, as it is in any case an indication of (previously if not present) high moisture.

I would:

  • Check by view (light and mirror) and surface testing, the wall cavity side of the lowest (closest to wet) drywall - to be sure that there is no mold growing on it, as well as checking higher areas in each wall cavity;
  • Remove any visibly moldy drywall, continuing to give a clean dry margin of 24" or one stud bay or floor joist or ceiling joist bay;
  • Vheck for adequate cleaning and sanitizing - I don't assume that floodwaters contained only seawater, as often during area flooding sewers back up, adding sewage to the mix that floods homes. A simple bacteria swab test, properly conducted, can test both representative cleaned surfaces as well as upstairs surfaces that might have become contaminated during building restoration if proper measures to prevent it were nto followed.
  • Do not enclose any wall cavity that has insulation that was wet and was not pulled out, cavity dried, and new insulation installed after any cleaning, sanitizing, and sealants - I look for moisture levels below 18%, preferably below 12% in the most-suspect, most-likely-to-be-wet, slowest-to-dry locations such as intersections between existing wood framing and drywall fastened to it, at wall bottoms, at wall sill plates and stud bases;
  • Iinspect the entire building, not just the area that was soaked, for possible problem mold growth, as high indoor moisture conditions could have made a problem elsewhere, such as in an attic, in closed cabinets, even under carpets on upper floors;
  • For more complete guidance on successful and durable cleanup & re-build procedures fter a building flood, please see our article series beginning at FLOOD DAMAGE ASSESSMENT, SAFETY & CLEANUP or see the step by step details found at the top of this page as well as at the top of other articles in this series.


For details about finding and handling mold and water damaged bathroom or kitchen cabinets and countertops see

More help


Continue reading at Step 5. RESTORE UTILITIES AFTER FLOODING - separate article - The rest of your work will be much easier if you have heat, electricity, clean water, and sewage disposal.

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