Flood damage repair in process in Poughkeepsie, NY (C) Daniel FriedmanFlood Damage Rebuild & Floodproofing Procedures
Flood Damage Repair Guide FEMA/ARC expanded & annotated - Step 8

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How to re-build a water, storm or flood damaged building and how to include measures that reduce the chances of future water or storm damage.

Earthquake, hurricane, flood or storm & wind damage to buildings: action & repair priorities: If your building has been flooded, this article series provides a guide for flood damage assessment, priorities of action, safety,cleanup, repair, restoring utility systems, and rebuilding.

We include information on avoiding or minimizing mold damage. 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.

Green links show where you are. © Copyright 2017, All Rights Reserved.

Step 8: How to Rebuild and Floodproof a Building after a Flood

Photograph of  an oil tank floating up out of the ground after area flooding

Don’t just build it back; build it better. Now is the best possible time to think about floodproofing your home because you can take definite action to protect your property in the future. many floodproofing measures are quite simple, cost effective, and easy to put in place.

By floodproofing as you rebuild, you can make the next flood easier on you and your wallet.

However this reasonable advice from FEMA/ARC faces some stumbling blocks expressed by building managers & developers of costly high-rise and other large buildings in the Northeastern U.S. following extensive flooding caused by Hurricane Sandy in 2012.

While we do not completely agree with them, comments and opinions reported by the New York Times (January 2013) included the following: [14]

"It's a matter of economics - I'm not sure too many developers would want to comprommise lucrative space elsewhere in the building for a storm that was hopefully just a 25- or 50-year event"

"I don't want to say you are throwing your money away ... but if your electrical mains ... are in the basement, they are going to be damaged anyway, so it just may not be worth it"

We don't agree with these views because we suspect that climate trends mean that the frequency of severe weather and flooding continues to increase as a consequence of global warming, and because the total osts of flood and storm damage in lost occupancy, building repairs, and possibly human costs, will continue to exceed the optimistic hopes of some building managers. We do agree with another concern reported by the Times, that current building codes and their treatment of basement or upper floor spaces used for mechanical systems need revision to address building use and valuation concerns expressed by developers and owners.

Floodproofing Approaches to Towns, Villages, Homes

In February 2013 the New York Times reported on a remarkable plan by Highlands, New Jersey to raise the entire town by eight to ten feet above its present level. The town, just about at sea level, is thus located in a designated Flood Zone V - the highest flood risk designation in FEMA's flood zone maps. Of course, Highlands has still to convince federal funding sources to pvovide its share of the $25. million that will be needed for the project. The Highlands mayor and others recognized that left unchanged the town would simply continue to flood. The Times article explained the strategy for Highlands: a series of canals could ease the import of sand fill brought in to increase the elevation of the town as building by building, structures would be raised throughout the downtown area: a space about 1500 feet by a mile in length and involving about 2000 buildings to be elevated in sections, 1/4 sq.mi. at a time.. [17]

Choices facing a town at sea level include several options, but the viability of individual options will vary considerably from one locale to another:

Floodproofing means to remodel or rebuild using materials and methods that will prevent or minimize damage from future floods. Consider the benefits to flood- proofing your home:

Questions to Ask Before Rebuilding a Flood-Damaged Building

Should you rebuild at all? If the building is located in an area likely to be constantly flooded and damaged it may be that relocation is a better course of action.[16]

If you are going to rebuild the flood-damaged structure in its present location, before you repair or rebuild, the first thing you should do is talk to your town’s or city’s or county’s building department. You will need to ask the following questions:

Five Types of Floodproofing

1. Elevation of the building or of key building mechanical systems as a means of preventing future flood damage

Building Elevation for Flood Damage Resistance

Most buildings can be raised so that the lowest floor is above the possible flood level. If you had foundation damage from the flood, you may need to raise the house to repair it. It will be easier and cheaper to elevate the house at that time.

There should be many contractors qualified to undertake elevating your house above flood level. Elevation or relocation are the only reasonable ways to protect your home if it is subject to coastal flooding or to deep flooding (more than six feet deep.)

Elevation and relocation are also the most dependable measures for floodproofing your home.

An elevated building will need a new foundation. The contractor will jack up a structure and temporarily set it on a temporary framework called cribbing while the foundation is built underneath. The foundations of an elevated building may be columns, piers, pilings, or raised foundation walls. The elevated building will usually look better and have added protection if fill dirt is placed around the new foundation. But check with your building department before adding fill dirt. It may not be allowed in your community.

Elevation of Building Mechanical Systems for Flood Damage Resistance

Backup generator, commercial grade (C) Daniel FriedmanIn January 2013 and following the widespread damage occurring in 2012 due to Hurricane Sandy in New York, Julie Satow reported in the New York Times that in buildings located close to water boundaries ( the Ocean or the Hudson River, for excample) building developers and architects began an increased emphasis in combining building waterproofing measures with steps to raise mechanical systems out of basements and onto upper building levels. [14]

Backup generators in larger and public buildings, even excluding special requirements (such as for hospitals operating life-maintaining equipment) need to be able to handle the electrical demands of :

Backup electrical systems in new construction or in buildings undergoing extensive renovations may include distribution of at least one backup-powered electrical ciruit to each building apartment or room

By placing mechanical systems as well as emergency generators (GENERATORS, BACKUP ELECTRIC) on higher building floors, even rooftops, it may be possible to keep some buildings open during severe weather or flood conditions.

2. Relocation of the Building as a means of preventing future flood damage

Moving a building out of the flood-prone area is the surest way to protect it from flood damage. Most houses and smaller commercial buildings in good condition can be moved, and it is usually no problem to find contractors experienced in moving buildings. You will have to purchase a new lot unless your present lot is large and has a good spot on higher ground for your house. Relocation and elevation are the only reasonable choices for protecting a home that is subject to deep flooding (of more than six feet in depth) or to coastal flooding.

3. Floodwall construction & use of Flood Gates as a means of preventing future flood damage

Floodwalls, berms, and levees all work to keep floodwaters from reaching your house. They are built to at least the height of the flood protection level in your area. Floodwalls are usually made of concrete. Berms are simply small levees, usually built from fill dirt.

Floodwalls, berms, and levees can either surround the building (ring levee) or connect to high ground. They can also be built up against a building’s foundation walls. a sump and pump will be needed to pump out water that seeps under the wall. Floodwalls, levees, or berms may not be allowed in your area if they could create a drainage problem on your neighbor’s property. check with your building department before you build.

In 2013 the New York Times described developers' addition of portable five-foot tall floodgate assemblies that can be stored until needed, then assembled and installed to encircle the building "in a matter of hours". Other flood-gate designs extend in height as much as 13 ft. above grade. .[4]

Floodwalls of all types work best in places where flooding is less than three feet deep. If floodwaters near your home develop swift currents, floodwalls, levees, and berms cannot be used—they may wash away. floodwalls and berms may not be appropriate for homes with basements.

If there is not enough room for a berm or levee, you may be able to build a floodwall made of concrete, which takes up less room. The walls should contain internal reinforcing bars to give added strength as well as to help walls resist cracking and settling over time. Walls must be properly anchored to withstand the same water pressure that can destroy basement walls.

4. Dry floodproofing as a means of preventing future flood damage

Sump & Pump Systems for Flood Damage Minimization

In a building that will rely on pumping systems to keep water out of basements or low areas,

FEMA/ARC continue:

Dry floodproofing means sealing a building to keep floodwaters out. All areas below the flood protection level are made watertight. Walls are coated with plastic or rubberized sheeting or special waterproofing compounds. Openings such as doors, windows, sewer lines, and vents are closed permanently, or can be temporarily sealed with removable shields or sandbags.

Dry floodproofing can only be done if the walls of your home are strong enough to hold back the floodwaters without collapsing. For this reason, dry floodproofing is not recommended if floodwaters are expected to be more than two or three feet above the ground level. Dry floodproofing is generally not appropriate for houses with basements or crawl spaces.

5. Wet floodproofing as a means of preventing future flood damage

Wet floodproofing means modifying a building so that floodwaters will cause only minimal damage to the building and contents. Building materials below the flood protection level are replaced with materials that are resistant to water. Floodwaters are allowed into the building to counteract the pressure of the water on the outside of the walls.

The New York Times article cited above [14] also described installation of "floodgates and submarine-style [water-tight] basement doors" to control water entry into the basements of high-rise buildings. Allowing water to enter a building basement during periods of area flooding tends to equalize pressures on both sides of the building foundation, reducing the chances of potentially catastrophic foundation collapse. See FLOOD VENTS & FLOOD PORTS for steps used to protect smaller and residential buildings from foundation damage due to flooding.

In a companion approach to minimizing the damage and costs of building flooding, building designers convert the use of basement and even flood-prone fdirst floors of buildings whose structures can withstand the forces of floodwaters. Using a building basement as a parking garage rather than as the home to building mechanicals or occupied spaces substantially eliminates the presence of materials and mechanical systems that will be damaged or more-likely destroyed by flooding.

For flood-prone building levels that will remain in use as occupied spaces, the original FEMA/ARC flood damage prevention article suggested:

You should furnish areas that have been wet floodproofed with light, portable furniture that can be easily and quickly moved before a flood. Objects that are difficult to move, such as furnaces, water heaters, appliances, and bookcases, are either put on platforms or reinstalled upstairs.

Wet floodproofing has one advantage over the other four floodproofing times: even the smallest efforts will significantly reduce flood damage the next time. Thousands of dollars can be saved simply by moving furniture and electrical appliances out of areas that will flood. If you decide not to use one of the other four floodproofing types, you should use wet floodproofing measures as you repair and rebuild. The rebuilding Tips in this section give more wet floodproofing ideas.

Building permit requirements when rebuilding a damaged building

One you’ve determined the repairs and floodproofing measures you are going to take, local codes generally require that you get a building permit. Before you make repairs or alterations to your home or property, make sure your plans are reviewed and okayed by your building department. You may also need to get the okay of our homeowner’s association or mortgage holder before you make repairs or alterations to your home or property.

If you are just replacing items such as carpeting or wallboard, you will probably not need a permit—but you should check with your local building department before you proceed. You will usually have to get a permit for electrical work and repairs of structural damage, such as broken walls.

Most local and state building codes require that a building that is substantially damaged be treated as a new building. a new residential building must be built so that its lowest floor is at or above the flood protection level. In other words, if your home meets the criteria described above for “substantially damaged,” you will have no choice but to elevate or relocate your home in order to meet local building codes.

Failure to follow the local building code can result in an order to stop reconstruction, a fine, imprisonment, higher flood insurance rates, denial of flood insurance, or all of the above.

Rebuilding tips for Wet Basements or Flooded Homes

Give your house plenty of time to dry. Many problems result from rebuilding after a flood before everything dries. If it takes a week for the visible signs of moisture to disappear, allow at least another week for the parts you cannot see to dry. Don’t try to force a swollen door to close. Don’t force wooden parts to fit. When completely dry, the wood may regain its original shape. There are small, inexpensive measures you can take to make your recovery easier after the next flood.

Better advice for drying out a flooded building adds these tips:

Make sure that all demolition and removal of soaked materials that cannot be salvaged (such as drywall, carpets, upholstered furniture) are removed as quickly as possible. Standard advice to avoid a mold contamination issue is that a building must be dried within 24-48 hours of being soaked - a recommendation that may be impossible when floodwaters inundate a large area. If weather temperatures are cold, in the 40's F or below, you may gain additional time as cold temperatures tend to slow the growth of mold in building materials.

When it is possible to enter a building safely to complete demolition, initial dryout and cleaning, do not simply rely on time to adquately dry the building. When electrical power can be used safely, and when weather permits, the addition of fans to increase air circulation, portable heaters and dehumidifiers can significantly speed the dryout process.

Do not leave trim or soaked drywall in place; remove those items to expose wood structural components to air circulation. Review Step 4. BUILDING DRY-OUT PROCEDURES for details.

Flood Damage Insurance Payout May be Limited

Watch out: when deciding to restore & rebuild a basement-level apartment (also referred to as "garden apartments") be aware that flood insurance policies for below-grade-level spaces in buildings cover only damage to the mechanical systems (boilers, water heaters, electrical panels). Details are at Flood Damage Insurance Payout May be Limited for Basement Apartments discussed in Step 7. Check on Financial Assistance

Following Hurricane Sandy in 2012, by January 2013 The New York Times reported that in some areas such as Hoboken NJ, in order to even attempt to obtain financial aid and despite buildings being covered by required flood insurance under NFIP, owners of basement-level or garden apartments must apply for grants to receive a portion of storm damage aid approved by the U.S. Congress. Further, even if some grants are approved the levels will not be sufficient to cover the total costs of cleaning and repairs to these flooded dwelling areas.[15]

Use Products that resist water damage

Choose structural and furnishing materials that are more resistant to water damage and to absorbing sewage-contaminted waters during times of flooding:

Advice for Floodproofing Building Utilities & Mechanical Systems

Relocate Mechanical Systems & Electrical Components to resist future water or flood damage

Keeping a building open in times of storms, hurricanes and flooding will require much more than just providing emergency heat, fire alarms, or even a reservoir of water.

During flooding and often for some period afterwards, public sewers and private septic systems are not serviceable and may require pumping and mud or silt removal before those systerms can be returned to operation. Heat and electrical service will require additional steps to assure safe operation and a safe, functional fuel supply. Air conditioning systems may be inoperable even if the equipment itself is above floodwaters if ducts have been flooded.

Protect Electrical Panels & Switch Gear from Flooding

FEMA/ARC advise:

Move the main breaker or fuse box and the utility meters above the flood protection level for your home. Make sure each circuit is labeled so you know which circuits control which outlets and fixtures. If the electrical code allows, raise the electrical outlets and switches above your flood protection level.

Watch out: for basic safety, ask your electrician to review the building electrical ground system to assure that in wet conditions the connection between the electrical panel and your local electrical ground will remain intact. If the building is not safelyi and properly grounded in wet conditions, keeping electrical power on risks shock or death by electrocution.

Moving electrical panels to higher building levels may not be enough to assure safe funcational use of backup electgrical generators and emergency electrical circuits in a building if the isolation switch or other key switch gear are not also located above possible flood levels. The New York Times article cited above [14] reported that during & following Hurricane Sandy in New York, although a rental building had its boiler and generator located on the building roof, the switching gear (presumably the isolation switch used to disconnect the building from the public electrical utility lines and to connect its emergency circuits to the backup generator system) were located in the flooded basement. Building management cited both relocation cost and concern for loss of lucrative lower level spaces as issues in relocaing the switch gear.

FEMA/ARC advice continues:

If you are going to replace a flooded furnace, water heater, or air conditioner, install the new one on a higher floor. If your new air conditioner or heat pump will be outside, install it on a platform above the flood protection level. a water heater can be put anywhere near a hot water pipe. An updraft furnace located in a basement can be replaced with a downdraft furnace on a floor above the flood protection level.

Where the flood protection level is not too high, a furnace, water heater or other heavy appliance can also be raised on a platform inside the house. Put the appliance on concrete blocks or a wooden platform supported by concrete blocks. Make certain that appliances such as washers and dryers are secure and will not vibrate off the blocks or platform during use.

You can protect the furnace, water heater, washer, and dryer from shallow flooding with a low floodwall built around the appliance. a concrete or wooden wall 1 or 2 feet high can stop low-level flooding. The wall should be waterproofed with plastic sheeting or waterproofing compounds that can be purchased at hardware stores.

Provide fuel for emergency generators & heating systems in a floodproofed building

Warch out: unless the fuel supply for your heating equipment is also protected from flooding by location and type of fuel source you will not be able to use heating equipment even if it has itself been protected from flooding. For this reason some building designers installing emergency generators select a generator that can operate from LP gas, placing the LP fuel tank on the building rooftop or in another elevated location, and protecting the fuel lines from flood damage not only from submersion in water, but from impact by storm-driven debris.

Protect fuel storage tanks from water entry and movement

Diesel fuel, Heating Oil or LP gas storage tanks used to store fuel used for backup generators or building heating equpiment are at risk of movement, mechanical damage, and water entry during flooding. See

Isolate Flooded HVAC ducts to provide heating or air conditioning in a floodproofed building

You may be able to provide air conditioning to some building areas even if lower floors have been flooded if the duct design permits manual or automatic zone dampers to cordon off and deactivate supply and return ducts that have been flooded. Failure to isolate HVAC ducts that have been flooded, or return air ducts that might draw air from flooded areas risks mold contamination of the entire HVAC system and can present serious health risks to building occupants if the system circulates mold or sewage pathogens throughout occupied spaces.

Wall reconstruction for a wet basement or flooded building

Wash and disinfect the studs and sills if the wallboard and insulation had to be removed. If you are going to rebuild the walls, remember that metal studs and sills are not damaged by water as much as wooden ones.

Pressure-treated wood will resist mildew and wood eating insects outdoors, but it may swell as much as untreated wood when soaked. Some kinds of pressure- treated wood should not be used inside the house, where they will come into contact with food or skin. (It depends on which chemicals were used to treat them.) Ask your lumber company to help you choose the right products for jobs you will do. They would also have consumer information sheets that give specific precautions for some products. Ask for them.

Wallboard installation pattern to resist future water damage

Think horizontal rather than vertical. Install the wallboard panels sideways so they are only four feet high. If the next flood is less than four feet deep, you only have to replace half the wall.

1” gap between floor and drywall bottom edge

Leave the wall open one inch above the sill plate for all wood framed walls, starting of course with any finished walls in the basement. The baseboard will hide this gap. When you remove the baseboard after the next flood, the wall cavity will drain freely and air will circulate better. Check your local codes, however. If a firewall is required, the building code may not allow the gap.

“Greenboard” or other moisture resistant wallboard is made for bathrooms and other damp areas, such as basements. It may be more sturdy when wet than regular wallboard. However, if soaked with floodwaters, it will present the same health hazard and risk of mold growth as regular wallboard and should be replaced.

Floor reconstruction material choices for a wet basement or flooded building

Some floors are made with particle board or plywood, materials that fall apart when wet for long. Floor joists and some wood floors will regain their shapes if allowed to dry naturally.

After re-nailing, a wooden floor may need a little sanding to be smooth, or you can place a new underlayment for a new floor over it. Use screws or screw nails on floors and stairs to minimize warping. Do not lay new flooring or carpet until the subflooring is completely dry.

Painting details for finishing a previously wet basement or flooded building

Do not paint until the surface is completely dry. If the surface still contains moisture, the paint will peel. Things look dry on the surface long before they are dry on the inside, and this can lead to costly mistakes. It may take several weeks for the surface to dry out enough.

FEMA/ARC advised:

To get an idea if a wall or floor is dry enough to paint, dry an area approximately 18 inches square with a blow dryer. (When checking a wall, select an area near the floor where it will be most damp.) Cover the area with a piece of clear plastic sheeting. Carefully seal all the edges with tape. Check the plastic 24 hours later. If there are beads of condensation on the side of the plastic that face the wall or the floor, it’s still too damp to paint.

Generally, "completely dry" means that moisture levels in the building material to be painted should be well below 18%, 12% or lower is better. When using a moisture meter to check moisture levels be sure to check areas most likely to remain damp, such as lower on walls, close to floor level, areas more distant from points of ventilation such as windows or doors, and at intersections of walls/floors and walls/ceilings.

You can cover concrete surfaces with a clear coating or penetrating sealer to make cleanup easier next time. Don’t paint over water stains—they will bleed through several coats of paint. Coat the stained area with shellac or a commercial stain killer before painting.

If you are going to dry flood- proof your walls, don’t rely on waterproofing paints; they cannot keep floodwaters out. Such paints may protect a deck from rain, but they cannot protect walls and floors against the pressure of standing water. (Thick plastic or rubberized sheeting provides the most secure waterproofing seal.)

Products to Avoid Avoid using or storing in areas likely to flood

If you live near the coast, your home is likely to suffer damage from the high winds and floodwaters of a hurricane or nor’easter. Boarding up all your windows and doors are the best way to protect them from breaking and letting in the heavy rains that a coastal storm brings. Taping windows will not prevent them from breaking during a storm.

Cut plywood to fit each of your windows and doors well before a storm threatens. Label each piece so you’ll know which window or door it covers. Store the plywood with the nails or other fasteners you will need to attach them. That way, you will be able to put the plywood up quickly when a storm threatens.

How to Work With a Contractor for Reconstruction of a Building after Wetting or Flood Damage

You may need a contractor to help you rebuild, especially to handle the difficult jobs such as foundation repair and electrical work. If you have been satisfied with work done by licensed local contractors, try them first. If they cannot help you, ask them for recommendations. If you must hire a contractor you do not know, talk to several contractors before you sign anything.


Continue reading at FLOOD REPAIR CONTRACTORS - separate article describing how to work with contractors & insurance companies after building damage by a disaster or flood, what the contractor should do, and how to resolve disagreements.

Suggested citation for this web page

Step 8. Rebuild and Floodproof at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


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