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Building Responses to Floods by Daniel Silvernail Architect

Building Responses to Floods by Daniel Silvernail Architect

Friday, February 16, 2024 by Daniel Silvernail Architect

Storm damage in Santa Cruz has been on the rise in recent years, making it essential to understand how to safeguard our properties. SCCG highlights expert advice from our community. Check out Daniel Silvernail Architect's blog on flood-resistant building techniques, essential reading for Santa Cruz residents seeking practical solutions.

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Building Responses to Floods by Daniel Silvernail Architect

With floods washing into low-lying areas throughout the U.S in recent years, there is a lot of discussion about way to prevent and manage floods. Given the fact that excessive flooding is not going to go away, let’s investigate five different ways to make a house more flood proof. As climatic conditions become more extreme, more houses will be at risk of flooding and these techniques will become increasingly important.

1. Elevation

This is the oldest and most obvious way to build a flood proof house. If you must build near a river or along the shore, just make sure you lift your building above the likely height of the flood waters. There are a number of ways to do that. You can build a house on stilts, a traditional form in many places. You can build it on a raised platform like a beach house, or on a bank of earth or concrete. FEMA, the Federal Emergency Management Agency, has published established guidelines as to how to do that.

2. Floodwalls

Rather than raise your home above the waters, a second common technique is to protect your home or property from the water by building a sturdy and waterproof wall. This can be done to protect whole towns and villages, but there’s no reason why it can’t be done on individual dwellings. Perimeter walls with watertight gates are one approach. You can also incorporate berms and walls into the landscaping, keeping the water out of a whole property or allowing the garden to flood while protecting the house.

3. Dry Floodproofing

If you’re prepared to let the flood waters reach the walls of your house itself, you might want to make them watertight. This can be done with sealant, or building in a waterproof membrane. Doors and windows will need to be flood proof. Airbricks and utilities entry points can be raised or sealed. Essentially, dry waterproofing is all about keeping the water out of the building. FEMA, the Federal Emergency Management Agency, has published established guidelines on the dry floodproofing of buildings.

4. Wet Floodproofing

Rather than keeping the water out of a building, an alternative approach is to let it in but minimise the damage it can do: fit a solid floor rather than wood, move power outlets up the wall and ensure that any unmovable furniture is made of a material that can safely take a soaking. Wet floodproofing is often used to retrofit flood-prone properties that the owners can’t sell, which is making the best of a bad situation.

Evaluating Flood-risk of Your Home

The first step to flood protection is to determine how likely you are to suffer a flood in your area, and how well your house is built to withstand it. The FEMA Flood Map Service shows general flood risk by region. Enter your address in the search bar to see your area’s flood zones, or click “Search All Products” and select your state, county and community to see reports of your region’s flood history. The flood maps include a number of zone markings that indicate the flood risk of a region and its relevant structures, such as bridges, dams and levees. Some of the zones are:

  • Blue Zones: These are the 1% annual-chance zones. FEMA blue zones are likely to face significant flooding at least once every 100 years. Although 1% may seem like a minimal figure, FEMA still considers this to be a high-risk designation, so you should take adequate steps to flood-proof your home.
  • Orange Zones: These are 0.2% annual-chance zones. FEMA states that orange zones are likely to face significant flooding at least once every 500 years. Since these regions face lower flooding risk than blue zones, your flood insurance rates will likely be lower. However, you should still make sure your house is not at risk of flooding due to leaks, or excessive surface runoff after rainstorms.
  • Yellow Zones: These are areas of undetermined flood risk. If you live or are looking to buy property in a yellow zone, we recommend researching the area’s flood history. Ask neighbors what kind of flooding they’ve seen over the course of their time there, and make certain with your appraiser or flood insurance agent that the property is built to withstand any likely flooding.
  • Blue with Red Stripes: These are regulatory floodways. These zones often include a river and its surrounding floodplain, and are usually kept clear in order to allow water to drain from adjacent flood zones. However, some houses are built in or near regulatory floodways. If this is the case for your home, take extensive precautions to protect the home from flooding.

When viewing maps for your region, note the year the map was made. Some maps are severely outdated, and the actual flood risk in your area might be different than presented on the map.

Next, work with your flood insurance agent or adjuster to determine the specific flood level of your house. The flood level is the height at which flood waters could rise during inclement weather. Ideally, your home should be built above this level in order to be reasonably protected from flood damage. If your house is at the bottom of a valley, for example, it could have a higher flood level than a neighbor’s house that’s uphill of yours, since more water might flow toward your home.

Learn how flood waters might enter your house by evaluating the surface runoff the next time you experience significant rain or snowmelt. Note whether the water flows toward or away from your home, as well as any doors or basement windows that it pools around. This will help you understand the overall risk of flooding and identify specific areas that might benefit from dry-proofing techniques.

Your standard homeowners insurance policy does not protect you from the risk of flooding. Instead, you’ll need to purchase flood insurance through either the National Flood Insurance Program or as an additional policy through your homeowners insurance company.

Prepare Your House to Resist Flooding

Once you’ve assessed your home’s overall risk of flooding, take any needed steps to properly flood-proof your home. Flood-proofing can range from expensive home renovations to free, basic maintenance. The steps you should take will depend on your home’s risk and how well the home was built to withstand flooding.

Flood-proofing Renovations

If you’re building in a flood-prone area, or if your home was not built to withstand rising water, some flood-proofing work may be required in order to minimize flood damage. Here are some methods of flood control to protect your home from rising water.

  • Raise your home on stilts or piers: While expensive to build retroactively, raising your house on stilts will raise your house’s flood level. Since even an inch of flood water can lead to significant damage, raising your home above the flood level will substantially protect your home.
  • Install foundation vents or a sump pump: Foundation vents, a form of “wet flood-proofing,” allow water to flow through your home, rather than pool around it. This both provides an outlet for flood water and relieves the significant pressure it can put on your walls and basement windows. Sump pumps are frequently used to pump water out of basements where flooding happens regularly. We recommend a sump pump with a battery backup in case the power goes out.
  • Apply coatings and sealants: A form of “dry flood-proofing,” coatings and sealants that you apply to your foundation, walls, windows and doorways help prevent flood water from leaking into your house through cracks.
  • Raise your electrical outlets and switches: All outlets, switches, sockets and circuit breakers should be at least one foot above flood level to avoid significant electrical damage in the case of a flood.
  • Install check valves on your pipes: Make sure that all pipes entering your house have valves to prevent a flooded sewage system from backing up into your home. Gate valves are preferred over flap valves, since they provide a better seal against flood pressure.
  • Grade your lawn away from the house: If your lawn tilts toward your house, rainwater will pool around your home. Use a heavy soil that contains clay and sand to regrade your lawn so that surface runoff empties into an appropriate place, such as a street gutter.
  • Point your downspouts away from your home: If your gutter runoff is not pointed away from your house in an appropriate direction, it can pool at the corners of your house and may eventually create leaks in your basement.

In addition to the renovations above, protect your home’s internal and external appliances by raising them above the flood level. Usually, you can do this inexpensively by placing them on concrete blocks. Here are some appliances that should be elevated above flood level:

  • Air conditioning units
  • Generators
  • Water heaters
  • Washing machines
  • Dryers

Take Preventive Steps when Flooding Starts

If a storm is imminent, or flooding has already started, follow these steps to minimize flooding and water damage to your property:

  • Turn off the water line, if that is the source of the flooding.
  • Clear out gutters and drains so that water can flow freely.
  • Use sandbags to block any gaps that will lead to flooding.
  • Move rugs, furniture, electronics and other valuables to a higher floor of the home, or elevate them.
  • Shut off your electricity at the breaker panel, if flood water is close to reaching your electrical system.
  • If it’s not raining, open windows to allow air flow through your home.
  • Turn on your sump pump or use a shop vacuum to remove water as quickly as possible.
  • Photograph or videotape any flooding to document and defend your claim with your flood insurance provider.

For Further Reading:

RIBA, the Royal Institute of British Architects, has published principals of floodproofing homes at:
Five Ways to Build a Floodproof Home is an article at The Earthbound Report:
“Five Flood Proof Strategies” is an article at Young Alfred:

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