Is there a way to keep floodwaters out of my house?

By: Cristen Conger  | 
Flooding is the most common natural disaster in the United States.

Key Takeaways

  • Dry floodproofing involves preventing water from entering the house by sealing doors, windows and foundation with waterproof materials, suitable for homes on concrete slabs without basements.
  • Wet floodproofing allows some water to enter to balance hydrostatic pressure, reducing overall damage, ideal for houses with basements where appliances are elevated above flood levels.
  • Emergency preparedness might involve installing sump pumps and using external barriers like cement flood walls or sandbags to protect against floodwaters, alongside shielding vulnerable doors and windows.

The terrifying triumvirate of tornadoes, hurricanes and wildfires represents the worst-case scenarios for most homeowners. Yet the natural disasters that strike most often in the United States are floods. No matter your surrounding geography -- whether situated in wooded lowlands by a river or in higher-elevation suburbia -- flooding can happen. That's because it doesn't require an exclusive set of weather conditions for one to occur. Flooding can result from the effects of melting snow, breached dams and levees, excess rainfall and improper landscaping.

Although flooding can happen practically anywhere, certain landscapes are more prone to it than others. Areas most susceptible to flooding (usually due to a nearby body of water) are referred to as floodplains. The statistical frequency of flooding on a floodplain is denoted by a certain number of years, such as a 100-year floodplain. That figure indicates the probability of floods occurring in consecutive years, rather than the average number of years between them. For example, when flooding occurs on a 100-year floodplain, there is a 1 percent chance of it taking place the following year [source: Organization of American States]. And in the case of a 20-year floodplain, there's a 5 percent chance of repeat floods.


Whether your house is on a floodplain or not, a massive deluge can inflict devastating destruction. And as the floodwaters rise inside of a house, so does the amount of damage. According to the National Flood Insurance Program, even one inch (2.5 centimeters) of floodwater can necessitate $7,800 in repairs. Saturated paneling and floors become warped and disconnected from their foundations. Furniture and appliances have little chance of surviving the soaking unscathed. As time lapses, mildew begins to grow in the damp conditions.

In the case of rapid flash flooding, it may seem like there's little you can do to batten down the hatches against the rising tide. Floods that build up more gradually, like the one that ransacked Fargo, N.D., in the spring of 2009, leave slightly more room for preparation. Though as demonstrated with the icy conditions in Fargo, the weather might not allow much leeway for emergency measures.

Extreme alternatives of elevating or relocating your house are costly and time-intensive. Instead, with minimal upkeep, proper landscaping over time and a few buckets of waterproof sealant, you can convert your house into a fortress against floodwaters.


Flood Protection from the Outside

Before you begin implementing steps to prevent indoor flooding, take a walk around your house after a rain shower. Notice where the largest puddles are in the yard and how far away from the house they've collected. The closer that water accumulates to the foundation of a house, the more likely flooding becomes.

One of the easiest ways to divert water away from a building is to keep gutters clean. This will also reduce the amount of rainfall sitting on your roof, which can cause structural damage over time. If you don't have gutters, it may be wise to dig a drainage system around the perimeter of the house [source: O'Neil].


The downspouts that siphon the water from the gutters to the ground should also be cleared of debris. Ideally, the pipes will move the rain at least 10 feet (3 meters) from the foundation to ensure that it won't simply soak into the ground and seep to the structure [source: O'Neil].

Once the gutters and downspouts are prepped for rain, it's time to evaluate the overall landscape. Does the yard slope down gently from the house, or does it sit at the bottom of a decline as though located in the middle of a soup bowl? Especially if you live on a floodplain, the lawn should have some amount of grading, which channels water away from the house. That entails building up the amount of soil at the foundation of the house to form a downward slant. Different jurisdictions have varying ordinances regarding lawn regrading, so verify yours before digging in.

For those with green thumbs, beware the site of your flower or vegetable garden. If you routinely water a large plot in your yard, make sure that the excess doesn't stream toward the house. You can accomplish this by grading the garden plot to maximize the use of water.

Now that the yard is designed for flood safety, it's time to move inside.


Flood Protection from the Inside

Sandbagging can help prevent water from entering a house.

The speed and volume of floodwaters are powerful enough sometimes to whisk away people and cars and topple buildings. When the pressure of a flood tide against a house becomes too great in comparison to the pressure on the inside, walls will buckle, and the foundation will be destroyed. To help prevent that from happening, there are two primary methods for protecting a house from flooding, depending on its structure.

When you think about keeping flood waters out of a house, the effect of dry floodproofing is probably what comes to mind. Dry floodproofing involves blocking water from entering the house at all. This is largely accomplished by coating the foundation in waterproof sealants or plastic sheeting [source: Kane County Division of Environmental Management]. Doors and windows below the flood plain elevation must also be sealed.


Not all houses are suitable for dry floodproofing because hydrostatic pressure from the water may cause extreme external damage. For that reason, only those built on a concrete slab without basements or cellars are appropriate for dry floodproofing. Brick homes are also more appropriate for it than those with wood siding since they can withstand more pressure [source: Parker]. However, according to the Federal Emergency Management Agency (FEMA), most housing will succumb to floodwaters higher than 3 feet (0.9 meters).

Wet floodproofing, on the other hand, allows some surface water to enter the house. This option may seem counterintuitive, but it can actually decrease the amount of overall damage by balancing the hydrostatic pressure inside and outside of the house [source: FEMA]. This type of design is best utilized for houses with basements. Inside, appliances such as washing machines, water heaters and furnaces should be elevated above the flood level [source: Kane County Division of Environmental Management]. Concrete block walls and bare flooring leave nothing valuable at stake if the floodwaters enter.

Sump pumps installed in the basement can also gird the foundation from water damage. Situated in a sump pit, the pump draws in the groundwater around the house and directs it away from the structure through drainage pipes. Some local ordinances require houses to be outfitted with sump pumps. In emergency situations, external barriers can also effectively stave off floodwater. Whether cement flood walls or improvised levees made of sand bags, strategically placed obstacles can halt the flow toward the house. Shields made of plywood, metal or thick plastic block vulnerable doors and windows.

Each year, floods sweep away thousands of buildings, possessions and precious mementos. With planning and foresight, your homestead doesn't have to be part of that tide of loss.


Frequently Asked Questions

How often should floodproofing measures be inspected or maintained?
Floodproofing measures should be inspected annually, before the rainy or flood season, to ensure they are in optimal condition.
What should I do immediately after a flood has occurred?
Prioritize safety by turning off utilities, then document any damage for insurance claims, and begin cleanup and drying processes.

Lots More Information

Related HowStuffWorks Articles

  • Kane County Division of Environmental Management. "Guide to Flood Protection." November 2005. (April 1, 2009)
  • Federal Emergency Management Agency. "Homeowner's Guide to Retrofitting." June 1998. (April 1, 2009)
  • National Flood Insurance Program. "The Cost of Flooding." Federal Emergency Management Agency. (April 1, 2009)
  • O'Neil, Caitlin. "Spring Flood Watch." This Old House. (April 1, 2009),,228010,00.html
  • Organization of American States. "Floodplain Definition And Flood Hazard Assessment." Primer on Natural Hazard Management in Integrated Regional Development Planning. 1991. (April 1, 2009)
  • Parker, Dennis J. "Floods." Taylor & France. 2000. (April 1, 2009)