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Flooded basement? How to deal with common causes

Wet basement problems can cost you thousands of dollars. Here are steps to help identify the source of the water and ways to minimize your risk.

Flooded room with rubber ducks floating

Unexpected water in your basement can damage walls and floors, destroy carpeting, ruin furniture, and lead — pretty quickly — to mold.

And perhaps the most upsetting of all: As these spaces are so often used for storage, a wet basement can ruin irreplaceable items like photo albums, antiques and family heirlooms. Can you safely leave your property downstairs once you clean the mess? Or does everything need to come upstairs immediately?

When you experience a flooded basement for the first time, it's important to determine if the water problems are going to recur or if it was a one-time event. If water in your basement is a consistent problem, it's time to start making decisions. Determining where the water is coming from is the first and most essential step in solving this problem.

What causes water to enter my basement?

Beyond observable flooding around your home and in your neighborhood, there are four common sources of water entering basements.

Basement water might be leaking down the foundation walls

If this is the first instance of water problems in your basement, the first thing to check for is surface water draining down next to the foundation walls. Water coming in at one location or only at the exterior foundation wall indicates surface water problems. Here are some things to look for once you get outside.

  • Overflowing gutters — leaves: Keeping gutters clean of debris should be a part of every homeowner's routine maintenance program. Depending on the surrounding trees, gutter cleaning may be required a few times a year. Products are also available to prevent leaves from getting into the gutters.
  • Overflowing gutters — downspouts: If you don't mind getting wet, you can do a self-check (your gutters must be cleaned out first). After at least 15 minutes of heavy rain, check your gutters. If you see any water overflowing, you have a problem. Any water overflowing out of the gutters is running down next to the house foundation. Even if the water isn’t getting into the basement, it could be eroding soil from under the house footings, which can lead to cracking of walls and ceilings.
  • Downspout distance: Downspouts should extend 10 feet from your home. While many homeowners do not like downspouts extending out this far, 10 feet is the minimum distance needed to discharge water coming off your roof far enough away from the house.
  • Pavement slope: Sometimes paving settles over time and water flow can change direction toward the house. If this is the case, the paving should be removed and replaced so it slopes away from the home.
  • Sealant: Sealant around pavement that borders the house sometimes cracks over time due to age or incorrect installation. If the sealant is cracked, it must be removed and replaced with new sealant.
  • Landscape slope: Does your yard or the land around your home slope away from your home? It should.
    • Look for any depressions in the ground next to the foundation walls. If any are found, fill in with dirt so the water drains away from the house. Use a clay-type soil that sheds water instead of sandy soil that allows water to soak into the ground. Make sure that at least eight inches is kept between the top of the earth and any wood or stucco on the house.
    • If there are large hills nearby sloping toward your home, and you think they may be causing the problem, a civil engineer may be required to analyze the situation and determine the appropriate solutions.
  • Irrigation: Avoid placing lawn irrigation next to the house. If this can’t be avoided, instruct the installer to limit the amount of water dispersed next to the house. Make sure the irrigation system includes a working rain gauge so the system does not turn on when there has already been plenty of rain for the plants and lawn.

Water-saturated soils pushed into the basement by hydrostatic pressure

If no surface water sources are found, then the source of the water is likely subsurface groundwater under hydrostatic pressure. Unfortunately, subsurface groundwater problems are more difficult and more expensive to fix than surface groundwater problems.

When the groundwater levels outside the basement rise above the level of the floor, the basement acts like a boat in a pond. If a boat is sitting in water, water will leak in through any open cracks or holes. It works the same way with a basement. Hydrostatic pressure can push water through hairline cracks.

Symptoms of this are water coming up through cracks in the basement concrete floor or water coming in at multiple locations.

If you have an older house within town and the house has a basement with no sump pump, it’s likely the perimeter foundation drain system connects directly into the city storm sewer system. If the level of the basement is below the street level, there is the potential of storm water backing up in the city storm sewer system and being pushed into the perimeter foundation drain system. This can saturate the soils around the house at the basement level with storm water under hydrostatic pressure, causing water to leak in.

No matter where it’s coming from, the best way to control subsurface groundwater is to install some type of perimeter drain system to relieve hydrostatic pressure. The groundwater is pushed into the drain system and not into areas where it can damage carpets, walls or belongings. The water drains by gravity into a sump pit where a sump pump discharges it out of the house.

There are two basic types of drain systems for wet basements

  1. Perimeter above-slab gutter system. This system is installed at the base of the exterior foundation walls on top of the floor slab. It doubles as a base material for the wall.
  2. Below-slab perimeter drainage system. The below-slab system requires the partial removal of the concrete floor slab and installation of drainage pipe, making it more expensive than the base gutter system.

It’s believed that an under-floor drainage system is better because the under-floor drains relieve the hydrostatic pressure before the water reaches the bottom of the floor slab.

Storm sewer water from the municipal storm sewer system backing up in to the home’s perimeter foundation drain

In many older houses with basements (mostly pre-1980), there is a perimeter foundation drain outside the exterior wall, at the level of the basement floor, next to the footings. A pipe was usually installed from the perimeter foundation drain to the street where it was connected to the city storm sewer system.

This can become a problem as the city storm sewer system becomes too small when more development causes more rain runoff. When this happens, the rainwater in the sewer system can get so high that water flows backwards toward the house.

Usually, the installation of an interior perimeter basement drain system connected to a sump pump will take care of the problem. If it doesn't, the (more expensive) alternative is to dig up and cap the pipe that is running from the house to the street from the perimeter foundation drain. However, this is not always possible; many times, this pipe is also draining sanitary waste from toilets and sinks in the house.

If you believe you have this problem, contact an experienced contractor for advice.

Sanitary sewer water from a clog in your home's sewer line, the municipal sewer line, or a combination of both backing up in sink and floor drains

If the water is coming up through floor drains or sink drains in the basement, then the problem is often water backing up from the municipal sanitary sewer system. During heavy rains, combined sewer systems can become overwhelmed with water. This can cause sewer water to back up in the system and sometimes into homes.

There are other possible explanations, too. Sewer backups can be caused by individual service lines being plugged by grease, waste, tree roots, breaks in pipes, or saturated ground. Sewer mains can also be plugged by vandalism or large items dropped down manholes.

This kind of flooding is an enormous problem for homeowners, as it's largely out of your control and probably means fecal waste is backing up into basements, possibly creating a serious health hazard.

To keep your individual lines clear, you can install backflow preventers that help stop sewer water from flowing backward into the house. Proper maintenance of your individual lines - for example, pouring tree root killer down your toilets once a year - can also go a long way in preventing sewage backups. Still, the problem is often out of your control.

Sewage in your basement means a major cleanup and a lot of uncertainty about future problems. If it's something you've seen in your home, you'll have to get your city government involved. At the very least, be aware of the problem and don't leave anything valuable near your downstairs drains.

Here are a few home improvement ideas that might help

Whether it's a plumbing leak, roof leak or a basement filled with water, water damage can require a costly fix. Here are a few home improvements to make water damage less likely:

  • Add or update drainage. Use gutters and downspouts to make sure water is diverted away from your home and its foundation.
    • The easiest solutions to overflowing gutters are to either add another downspout on that run of gutter or to increase the size of the downspout. The best solution between these two is probably adding another downspout; the second downspout can act as a backup if the first one gets blocked.
    • If you choose to replace the existing downspout with a larger one, make sure the contractor increases the size of the corresponding hole in the gutter.
  • Install a sump pump. Try this addition if water damage has been a serious problem in your home's lower level. Choose a cast iron sump pump, which may last longer, and consider buying a backup battery-powered pump in case the power goes out. Test your pump twice a year or as suggested by the manufacturer.
  • Replace your pipes. Much home piping has a lifespan of 50 to 80 years, so if you have an older house, ask a plumber to check its condition. PVC pipes may need to be replaced every 25 to 40 years.
  • Install a water leak detection system. An automatic water shut-off valve is a water leak detection system that will shut off the water supply to the home when it detects water on the floor or an irregular flow in the pipe.
  • Update your windows and doors. Look for watertight options in new windows and doors. Older wood windows should be cleaned, repainted and re-stained periodically. Cracks in trim should be resealed. Glazing compound around older windows should be replaced as needed.
  • Regularly check your roof for signs of damage. Look for things like excessive wear on shingles or missing shingles.
  • Seal your basement. Thick coatings, paint and silicate-based sealers may help minimize or prevent water damage. Each method varies in application and cost.
  • Replace washing machine supply hoses. Plan for new ones every three to five years as part of a proactive maintenance plan.

The information in this article was obtained from various sources not associated with State Farm® (including State Farm Mutual Automobile Insurance Company and its subsidiaries and affiliates). While we believe it to be reliable and accurate, we do not warrant the accuracy or reliability of the information. State Farm is not responsible for, and does not endorse or approve, either implicitly or explicitly, the content of any third party sites that might be hyperlinked from this page. The information is not intended to replace manuals, instructions or information provided by a manufacturer or the advice of a qualified professional, or to affect coverage under any applicable insurance policy. State Farm makes no guarantees of results from use of this information.


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