PATH Technologies That Improve Flood Resistance and Reconstruction

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Buying a new home can be difficult at any stage in life. After a major disaster, the stress of temporary housing and time pressures can make the process overwhelming. Be cautious as you start to rebuild and give the decision the time it deserves.

Consider the type of home you want, the amount of space you need, and the size mortgage you can afford. Check with your local builders association for a list of builders in your area. Contact the Better Business Bureau to determine if any concerns have been raised about your builder. Look for builders who construct ENERGY STAR qualified homes as these homes will consume less energy and cost less to operate.

Aside from the number of bedrooms and bathrooms, consider the type of materials and equipment that will be used. See below for more information on materials that improve disaster resistance. Use PATH’s Durability Doctor to find the durable materials that will help you maintain your home at the lowest cost.

Ask your builder about the steps he/she will take to improve the home’s durability and energy efficiency. Here are a few questions to get you started:

What type of moisture mitigation strategies are in place? How will you waterproof the basement? How do you seal the joint between the basement floor and foundation walls?
How will you protect from termite damage and other pests?
Do you normally caulk and weatherstrip all windows, exterior doors and other house penetrations?
Are the appliances, windows, lighting and HVAC system ENERGY STAR qualified?
How do you ensure a healthy indoor environment?
Read PATH’s tips for buying an existing home.

HUD resources for homebuyers. HUD information on manufactured homes.

Floods are one of the most common hazards in the U.S. However, all floods are not alike. Riverine floods develop slowly, sometimes over a period of days. Flash floods can develop quickly, sometimes in just a few minutes, without any visible signs of rain. Flash floods often have a dangerous wall of roaring water that carries a deadly cargo of rocks, mud and other debris and can sweep away most things in its path. Overland flooding occurs outside a defined river or stream, such as when a levee is breached, but still can be destructive. Flooding can also occur from a dam break producing effects similar to flash floods. Flood effects can be very local, impacting a neighborhood or community, or very large, effecting entire river basins and multiple states. Be aware of flood hazards no matter where you live, but especially if you live in a low-lying area, near water or downstream from a dam. Even very small streams, gullies, creeks, culverts, dry streambeds or low-lying ground that appear harmless in dry weather can flood. Every state is at risk from this hazard.

What to do before a flood

Know the terms used to describe flooding:

Flood Watch: Flooding is possible. Stay tuned to NOAA Weather Radio or commercial radio or television for information. Watches are issued 12 to 36 hours in advance of a possible flooding event.
Flash Flood Watch: Flash flooding is possible. Be prepared to move to higher ground. A flash flood could occur without any warning. Listen to NOAA Weather Radio or commercial radio or television for additional information.
Flood Warning: Flooding is occurring or will occur soon. If advised to evacuate, do so immediately.
Flash Flood Warning: A flash flood is occurring. Seek higher ground on foot immediately.
Ask local officials whether your property is in a flood-prone or high-risk area. (Remember that floods often occur outside high-risk areas.) Ask about official flood warning signals and what to do when you hear them. Also ask how you can protect your home from flooding.

Identify dams in your area and determine whether they pose a hazard to you.

Purchase a NOAA Weather Radio with battery backup and a tone-alert feature that automatically alerts you when a Watch or Warning is issued (tone alert not available in some areas). Purchase a battery- powered commercial radio and extra batteries.

Be prepared to evacuate. Learn your community’s flood evacuation routes and where to find high ground. See the “Evacuation” chapter for important information.

Talk to your household about flooding. Plan a place to meet your household in case you are separated from one another in a disaster and cannot return home. Choose an out-of-town contact for everyone to call to say they are okay. In some emergencies, calling out-of-state is possible even when local phone lines are down.

Determine how you would care for household members who may live elsewhere but might need your help in a flood. Determine any special needs your neighbors might have.

Prepare to survive on your own for at least three days. Assemble a disaster supply kit. Keep a stock of food and extra drinking water. See the “Emergency Planning and Disaster Supplies” chapter for more information.

Know how to shut off electricity, gas and water at main switches and valves. Know where gas pilot lights are located and how the heating system works.

Consider purchasing flood insurance.

Flood losses are not covered under homeowners’ insurance policies.
FEMA manages the National Flood Insurance Program, which makes federally-backed flood insurance available in communities that agree to adopt and enforce floodplain management ordinances to reduce future flood damage.
Flood insurance is available in most communities through insurance agents.
There is a 30-day waiting period before flood insurance goes into effect, so don’t delay.
Flood insurance is available whether the building is in or out of the identified flood-prone area. 11. Consider options for protecting your property.
Make a record of your personal property. Take photographs or videotapes of your belongings. Store these documents in a safe place.
Keep insurance policies, deeds, property records and other important papers in a safe place away from your home.
Avoid building in a floodplain unless you elevate and reinforce your home.
Elevate furnace, water heater, and electric panel to higher floors or the attic if they are susceptible to flooding.
Install “check valves” in sewer traps to prevent flood water from backing up into the drains of your home.
Construct barriers such as levees, berms, and floodwalls to stop floodwater from entering the building. • Seal walls in basements with waterproofing compounds to avoid seepage.
Call your local building department or emergency management office for more information.
What to do during a flood

Be aware of flash flood. If there is any possibility of a flash flood, move immediately to higher ground. Do not wait for instructions to move. 2. Listen to radio or television stations for local information. 3. Be aware of streams, drainage channels, canyons and other areas known to flood suddenly. Flash floods can occur in these areas with or without such typical warning signs as rain clouds or heavy rain. 4. If local authorities issue a flood watch, prepare to evacuate:

Secure your home. If you have time, tie down or bring outdoor equipment and lawn furniture inside. Move essential items to the upper floors.
If instructed, turn off utilities at the main switches or valves. Disconnect electrical appliances. Do not touch electrical equipment if you are wet or standing in water.
Fill the bathtub with water in case water becomes contaminated or services cut off. Before filling the tub, sterilize it with a diluted bleach solution.

  1. Do not walk through moving water. Six inches of moving water can knock you off your feet. If you must walk in a flooded area, walk where the water is not moving. Use a stick to check the firmness of the ground in front of you. 6. Do not drive into flooded areas. Six inches of water will reach the bottom of most passenger cars causing loss of control and possible stalling. A foot of water will float many vehicles. Two feet of water will wash away almost all vehicles. If floodwaters rise around your car, abandon the car and move to higher ground, if you can do so safely. You and your vehicle can be quickly swept away as floodwaters rise. 7. See the “Evacuation” chapter for important information.

What to do after a flood

  1. Avoid floodwaters. The water may be contaminated by oil, gasoline or raw sewage. The water may also be electrically charged from underground or downed power lines. 2. Avoid moving water. Moving water only six inches deep can sweep you off your feet. 3. Be aware of areas where floodwaters have receded. Roads may have weakened and could collapse under the weight of a car. 4. Stay away from downed power lines and report them to the power company. 5. Stay away from designated disaster areas unless authorities ask for volunteers. 6. Return home only when authorities indicate it is safe. Stay out of buildings if surrounded by floodwaters. Use extreme caution when entering buildings. There may be hidden damage, particularly in foundations. 7. Consider your family’s health and safety needs:

Wash hands frequently with soap and clean water if you come in contact with floodwaters.
Throw away food that has come in contact with floodwaters.
Listen for news reports to learn whether the community’s water supply is safe to drink.
Listen to news reports for information about where to get assistance for housing, clothing and food.
Seek necessary medical care at the nearest medical facility.
Service damaged septic tanks, cesspools, pits, and leaching systems as soon as possible. Damaged sewage systems are serious health hazards. Contact your insurance agent. If your policy covers your situation, an adjuster will be assigned to visit your home.
To prepare: Take photos of your belongings and your home or videotape them.
Separate damaged and undamaged belongings.
Locate your financial records.
Keep detailed records of cleanup costs.

If your residence has been flooded obtain a copy of “Repairing Your Flooded Home” from the local American Red Cross chapter. 11. See the “Recovering From Disaster” chapter for more information.


Homes can be built to stand up to powerful storms. Choosing the right building materials and paying attention to construction details are keys to building a storm-resistant home.

While researchers still are working on design improvements and models that accurately predict how light-frame homes behave during extreme wind events, here are a few key recommendations from the PATH report Durability by Design:

Continuous uplift load path and anchorage: In hurricane-prone areas, use hurricane ties or clips to connect the roof to the wall system. Line up bracing and truss tie-down points, and anchor each level to the level below. Use light-gauge steel straps to anchor the first story to the foundation. (During Hurricane Andrew, hurricane ties had a 92% success rate.)

Wall bracing: Proper diaphragm and shear wall construction using a rated bracing material such as oriented strand board or plywood is critical.

Construction practices with durability in mind: Material durability is key to future disaster resistance. Buy and install materials that will last. Also, attention to small details – lapping wall top plates at intersections with interior walls and attaching sheathing to a common stud in corner construction – can make all the difference, according to full-scale shear wall testing done by the NAHB Research Center.

Proper nailing schedule: Size, type and placement are all factors. Inadequate nailing schedules in older building codes were implicated in the widespread roof sheathing damage in Hurricane Andrew. Preliminary findings of an NAHB Research Center study suggest that nail edge distance tolerance is quite tight (acceptable nail edge distance should be 1/4 to 3/4 inch) and that nail overdrive can reduce uplift strength of the connection significantly. Thicker sheathing can offset sensitivity to overdriving. When inspecting roof sheathing nails, attention to a gable end truss is especially important.

Ring-shank nails: To secure sheathing panels in hurricane-prone areas with basic wind speed of 110 mph or greater, ring-shank nails are recommended for their higher withdrawal capacity. Costs are comparable, and with a slightly smaller diameter, they offer the added benefits of less frequent reloading of pneumatic nail guns and more forgiving edge distance tolerances.

Wind-borne debris protection: Reduce forces on the structure and minimize water- and wind-related damages to the interior by protecting windows with approved shutters or properly fastened wood structural panels in coastal homes that might experience a hurricane.

Keep the Lid On

A key to minimizing water damage during severe storms is to keep the roof covering intact. PATH team members working in Florida have found two practical ways to do that: 1) rubber or asphalt sheets with peel-and-stick undersides (“self-adhering polymer modified bitumen underlayment” instead of standard roofing felt) beneath standard shingles, costing $700-1,000 more than standard asphalt roofing for a 2,400 sf house, or 2) a new Owens Corning roof shingle with a 130 mph wind rating, costing approximately twice the price of standard roof shingles.

Storm-resistant shutters for a 2,400-square-foot, single-story home with 312 square feet of windows cost about $700.

Build with Concrete

At a site demonstration in Melbourne, Florida, a PATH team is examining how to exploit the strength of poured concrete walls to enable homes to weather a major storm. Poured concrete walls are quicker to construct and better resist wind loads than concrete block walls.

Surprisingly small additional investments in the concrete wall system fortify the standard concrete home enough to withstand a 125-mph wind-force: extra tie-downs and alignment of the bearing walls with the truss tie-down points to create a direct load path configuration. Essentially a planning issue, these adjustments represent less than $10 in additional costs. Similarly, additional steel costs average about $13, primarily for reinforcing around windows and sliding glass doors. And with another nominal cost increase to cover a deeper reinforcing member, the team found that the wall system could reach 135-mph wind resistance.

See PATH tools and resources related to disaster resistance. For more on results from PATH’s research into high wind-resistant home construction see Technology vs. Nature, a PATH article in the August 2003 issue of Professional Builder.

Remember the Basics

In the haste to rebuild and restore, make sure your building practices and materials result in homes and businesses that are properly weatherized and energy efficient. By properly flashing and sealing buildings, you will minimize future water damage and mold growth. By selecting and properly installing energy-efficient HVAC equipment, lighting and appliances, and by weatherizing the buildings, you will maximize resources and minimize the owners’ future energy bills.


Site Work

If sewer reconnections are a problem during reconstruction, or if sites have high bedrock and/or low soil percolation rates Shared (Community) Wastewater Treatment Systems, sometimes called shared septic systems, are an affordable, space-saving solution. These systems consist of a single larger drainfield/treatment area connected to each house’s individual septic tank.


Concrete Footing and Pier Forms are quicker and less expensive alternatives to conventional forming methods for concrete footings and piers.

A Crawl Space Foundation System, also known as a Fast Track Foundation System, is a series of structural corrugated steel wall panels positioned along existing in-place structure, then cast into place, creating a foundation wall. The panels are quickly and easily installed with minimally trained labor. It is not appropriate for slab-on-grade construction, and may provide only limited cost benefit for basement foundation construction.

Walls, Roofs and Decks

Panelized Wall and Roof Systems, including Structural Insulated Panels and SIP Modular Housing, can be manufactured offsite while the sitework and foundations are being prepared, and then can be assembled swiftly by less skilled laborers, significantly accelerating the overall homebuilding process. Steel Framed Modular Housing has the same advantages with respect to decreasing the building cycle, and has less flammable content.

When entire subdivisions must be rebuilt, an On-Site House Factory could be established to build wall or floor panels, or modular homes. The home construction plant can be either a movable manufacturing facility, or can be planned into the subdivision’s development mix, and re-commissioned as a community or day care center, office, loft, apartment, or condominium suites.

Fiberglass Reinforced Plastic Exterior Decks need no maintenance, do not crack, split, or warp, and are stronger and more durable than traditional decking. Traditional wood decking materials, both preservative-treated and naturally rot-resistant materials, have a life expectancy ranging from 10 to 20 years when maintained periodically with chemical sealants, whereas FRP decks are expected to last the life of the home. Normally, the installed cost of FRP decks is about double that of decks constructed with preservative treated wood, and about 50 percent more than redwood and cedar decks. However, due to the high demand for wood during this rebuilding process, this price differential might be significantly less.


Electrical Raceways, commonly used in commercial buildings, are now available for residential applications. Electrical raceways can simplify and speed the task of wiring, and reduce wall penetrations that can compromise a building’s thermal performance.


Reduce the time it takes to install the domestic water piping by installing a home run plumbing system using a Plastic Plumbing Manifold and Aluminum-Plastic Composite Water Piping. Manifold plumbing systems are control centers for hot and cold water that feed flexible supply lines to individual fixtures. Plastic manifolds together with flexible plastic piping can be quickly installed and offer installation-related cost advantages over conventional plumbing systems. The Composite piping can be installed in walls, ceilings, concrete slabs and underground. The pipe’s flexibility makes it easy to snake through wall studs and floor joists, and increases its earthquake resistance.

Flexible Gas Piping is easier to install than traditional threaded black-iron piping because it is lightweight, easy to bend, and requires fewer connections and fittings than conventional piping. These benefits can speed installation and add up to substantial labor savings for builders. The flexibility of this piping also enhances its durability in earthquakes.

Air Admittance Valves (AAVs) eliminate the need for conventional pipe venting and roof penetrations. Manufacturers estimate a 25% to 75% reduction in the amount of venting materials needed for the system overall, so installation efficiency can be greatly increased. AAVs eliminate the need for lateral return vent runs that require cutting several holes through wall studs, or long runs of vertical piping that must pass through the ceilings, attic, and roof. AAVs can also eliminate the need for firestopping materials at floor/wall penetrations.

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