The Causes and Costs of a Flooded Basement

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If your basement floods, you need to know where the water came from, and how much it will cost to fix the problem
Despite some insurance companies claims to the contrary, basement flooding stands as a real possibility for all homeowners, even those who don't live on a floodplain or anywhere near a river.
According to the National Flood Insurance Program, floods are the No. 1 disaster in America, averaging over $3 billion in claims per year. If you come home to a basement knee-deep with water, you need answers: How did the flood start, how can it be stopped, and how much will it cost to repair?
The most common basement flooding causes
All basements are prone to flooding. Water always runs from high to low ground, and this means that under the right circumstances your basement becomes an unwanted swimming pool. But where does the water come from?
One common culprit behind basement flooding is rain. Excessive amounts of rain in a short period of time can overload basement waterproofing systems, saturating the earth around your basement and then pushing in through foundation cracks.
Properly waterproofed basements and homes should have a tar sealant on both the inside and outside of foundation walls, in addition to what's known as "weeping tile." This tile pulls water away from your home to the local sewer system. If these systems fail because they can't handle the incoming water load, your basement will flood.
The slope of your lawn, also called the "grade," can contribute to your basement flooding. Your lawn should always slope away from your house, directing rainwater toward the sewer system. To make sure your lawn isn't the problem, take a walk around your home when it's raining. If you see water pooling next to your house, you have a problem.
Sewer backups also cause basement flooding. Suburban homes usually have a sewer tie-in line that is lower than the floor of the basement, allowing dirty water from tubs, toilets and sinks to be carried away. If this sewer line becomes clogged or damaged and its waterline rises above that of your basement floor, expect water to come rushing back into your home.
In communities built on swamp or marshland, a sump pump failure can cause the flooding. Sump pumps are set in basins drilled into the floor of the basement and act as a fail-safe by mechanically pumping out excess water. Experts recommend installing a back up sump pump in case the primary pump fails.
Repair costs after a basement flood
The costs to fix basement floods and their damage vary significantly depending on how much water infiltrated the foundation and how much of your property was damaged. A minor flood with several inches of water could cost $10,000 to repair, whereas a more substantial flood could cost between $25,000 and $50,000 to remediate. The length of time the water sat also affects the price to repair the flooded basement, because of mold issues.
To help keep costs down, the first thing you need to do is dry out the basement. If you're dealing with puddles on the floor, consider renting a wet vac or similar product to suck up and dispose of the water. Invest in a dehumidifier to help dry out the rest of the basement.
Remove any organic items such as bedding, towels and upholstery that have been damaged by the basement flood. If they don't dry within 48 hours, throw them away because they'll start to mold. Next, take a look at the basement structure. Any wet drywall needs to be completely removed, as does wet insulation or wood underneath. Water will spread through these materials quickly, and even slightly damp wood grows mold. Mold spores and contamination can lead to serious health issues, address any mold concerns immediately, as mold spreads quickly throughout a home.
Dealing with homeowner's insurance after a basement flood
If you have flood insurance, call your insurance provider. If you're not sure, check your plan. Some companies deliberately omit floods or "acts of God' and won't cover the replacement of any water-damaged items. Knowing this upfront is very important.The insurance company will send out an adjuster to assess the damage, take a list of all the items and call in a professional. Whether you go with insurance or not, chances are you'll want to call an expert. You have several choices here. Basement waterproofing companies can get the water out and deal with any foundation issues, whereas disaster restoration specialists will remove the water, deal with any mold and mildew issues and then return your basement to (nearly) its original state.
Bear in mind that, just like with auto insurance, you have the final say over who does work in your home. Insurance adjusters can recommend preferred contractors, they but cannot force you to use a specific company. As always, check the list before hiring a remodeler or purchasing home owner's flood insurance.
Editor's note: This is an updated version of an article that originally published on September 20, 2013.