A flooding basement is when there is standing water in the basement to a level of 6" or more.  Basement flooding usually occurs when there is general flooding, like when a nearby river overflows its banks and there is standing water above the house foundation grade outside the house.  The only way to avoid flooding is to raise the entire grade level of the house, which is not usually possible.  If the ground around your house is higher, it may be possible to dig out a swale to help drain the water away from your house.  If you live in a flood plain, it is highly recommended that you get a house on higher ground.  There is no real 100% foolproof solution to flooding.  The house was simply built in a place where it should not have been and the municipality you live in does not provide adequate drainage and flood prevention measures.

Most times, basements do not flood, but have seepage.  Seepage is when your basement floor gets some rivulets of water, usually no deeper than 1/2 to 1" deep, which soaks and ruins the carpet in the finished portion of a basement.  Seepage usually occurs when there are small cracks in your basement's concrete foundation walls or, if you have an old house, when the brick, CMU or stone foundation leaks.

 

If you live in a large city, such as Chicago, the municipal storm and drain sewers can become overloaded with  floor drains or basement sink drains backflowing because of the large amount of water in the storm sewers.  This condition can be fixed by one of two methods: The expensive, but "fix and forget" method is to have a check valve installed between your house's drainage system and the municipal sewer system.  A check valve is a plumbing fixture that allows water to only flow in one direction.  Installing a check valve will allow water from your house to drain into the sewer, but prevent any sewer water from backflowing into your house.  This solution works very well, but requires a plumber and some expensive digging to install. The inexpensive fix is to install a stand pipe in all the basement floor drains.  When I was young, this used to be a pretty involved installation issue, with breaking up basement floor concrete and leading floor drain pipes.  Nowadays, this is a relatively easy process.  You can purchase a flood drain stand pipe for under $15 that will fix your floor drain and has an expanding rubber gasket to seal it tight.  Once installed in each basement floor drain, this gasket allows you to screw a threaded pipe into the gasket.  This pipe, usually about 1 1/2' long, stands above the floor level and any backflowing water rises up into the pipe and NOT onto your basement floor.  This utilizes an simple principle of physics.  The pressure of the water flowing back into your basement can be easily countered by the pressure of the water "standing" in the standpipe.  I know it sounds implausible, but it works.  Go figure.

Sump pumps are commonly seen in houses, these days, but their function is largely misunderstood.  Most people thing that a drain tile and sump pump system will prevent water from entering their basement through the walls, during a heavy rain.  This is not true.  Under your house, and depending upon where you live, is the water table.  This is the level at which is you dig down, you would hit water.  In the Chicagoland area, this is not very far because of our proximity to Lake Michigan.  When it rains, the water table rises.  If the water table rises higher than the floor of your basement, water can seep in between the basement slab and the foundation wall.  In areas with high water tables, builders install a "drain tile" system around the house's foundation.  This is a system of perforated pipes that run parallel to the bottom of the house's foundation and drain into a pit located in the basement floor (the sump).  Because the bottom of the sump pit is lower than the basement floor, water drains from the drain tiles into the sump.  Many times, the bottom of the sump pit is also perforated to allow water to drain into it, directly.  Also in the sump pit is a pump with a float switch.  When the water level in the sump pit rises, this switch turns on the sup pump.  This pumps the water out of the pit and into a pipe which ejects the drainage water out of the house and (hopefully) far away from the house.  Some common errors with sump pump system installation is to drain the water back into the sewer system (not allowed in most areas) or to have the sump drain right outside the house, where is just flows back into the drain tiles and can overload the system.

 

Make sure that your roof's gutters and downspouts are in good condition, free of leaves and debris, that they drain at least 6' away from the house (12' is better) and that they drain down slope from the house.  The grade around your house should, ideally, slope away from the house at a rate of 1" down for each 12" away.  This is a quick, easy and inexpensive solution.  If rain water is drained away from the house, it will not come back into the basement.  Added downspout sections cost as little as $4.95 for a 10' section.  Avoid the cheap plastic add-on extensions and buy the metal ones, they last longer and do not leak.  Downspout additions should also be secured with sheet metal screws and your landscaping company should be warned to not remove or physically damage them.  This is a very simple, but the most overlooked solution, in my experience.

 

If you don't have room to extend the downspouts, underground PVC drain pipes can be installed and the rain water can be directed to the back or front yards.  These drainage pipes are equipped with "pop-up" drains at their ends, which pop up to allow the water to empty away from the house (just make sure that the don't wind up flooding out your neighbor's basement!).

 

Make sure that you have a good quality de-humidifier in your basement (65 - 70 pints per day capacity, or better) and run it 24/7 from April through October (Chicago area advice, it's humid here 3 seasons of the year).  Buy a model that has an optional drain hose option.  This will allow the water to drain directly into a floor drain or sink and save you the grief of having to empty the de-humidifier when it gets full.  (Just remember to clean the de-humidifier coils every month so that they do not become clogged with dust or pet hair.)  Even if you don't have seepage problems, ALL basements  still have high moisture and humidity levels (finished or not).  A basement is underground, it is just a big hole and it will always be moist.  Your house's foundation and basement slab are cooler than the rest of the house.  They are underground and the ground is cold.  During the summer, when there are high humidity levels, this humidity will condense on the foundation walls and slab and produce moisture.  Use of a dehumidifier will also keep down your air conditioning bill.  Dryer air feels cooler than humid air.  It is also a good idea to run your furnace's blower fan, 24/7, during the summer to ensure proper air flow.

 

If you have a full or partially finished basement with carpet or hardwood on the floor, make sure that you have a 10 mil plastic vapor barrier between the carpet pad and the concrete slab floor.  When you think about it, a carpet pad is just a big sponge.  This sponge will soak up any condensing (or seeping) water and wick the moisture right up to your carpet or hardwood flooring.  Eventually mold will form or the wooden floorboards will buckle and you will have to replace the carpets.  Install the plastic directly on the concrete slab floor.  Overlap the seams of the plastic sheeting at least 6" and tape them with waterproof tape (NOT duct tape).  Bring the edges up the walls, at least 2", and install the baseboard over the plastic.  Also, make sure that basement carpets are made of synthetic materials, like polypropylene.  These materials are much less prone to mold and, if dried quickly (within a couple of days) can be re-installed.  There are even some newer products that allow a small air space between the slab and the floor, which will still keep the carpet dry but will also allow for any condensation to be air dried  (See here: www.dricore.com ).

 

Make sure that all the drywall walls in your basement are properly installed.  The bottom of the drywall should be installed at least a 1"" space above the concrete floor.  This gap will keep water from wicking up the drywall and will help to keep it dry.  If your drywall was not installed correctly, it is usually easy to just cut out 1" at the bottom.  Most new finished basements are constructed with fiberglass faced drywall at the run closest to the floor.  Fiberglass faced drywall will not support mold growth like standard paper faced drywall will.  The face paper on normal drywall is manufactured using re-cycled newspaper and is a very good mold food.  This is true for normal drywall as well as the so-called "water resistant" greenboard.  Mold doesn't see the color of the drywall paper and only sees a big, fat meal waiting.

 

Make sure that your sump pump, and if you already have one, is equipped with a 102 volt UPS battery backup power supply. NOT a cheap, 12 volt battery powered back-up pump.  (A regular 120 volt uninterrupted power supply).  Many of our past clients have ignored the recommendation to install a 120 volt UPS backup and have suffered greatly for it.  Their basements got wet, their carpets were ruined and the drywall got all moldy.  Power failures usually occur along with rain storms and the time you most need your sump pump is when it is raining.  In addition, you should install a 2nd, full sized, 120 volt pump beside the main pump.  These back-up pumps are usually placed 6-8" higher (on a couple of bricks) than the main pump and will provide extra drainage flow if there is a large amount of water draining into the sump, or in the case your main sump pump fails.  When buying a sump pump, do not get a cheap model from your local Home Improvement store.  Go to a reputable plumbing supply dealer and buy a heavy duty, cast iron cased commercial grade pump.  They last much longer and have greater pumping capacity and are well worth their higher price.  Make sure each sump pump is equipped with a check valve (allows water to flow out, but not back in) and make sure to change the check valve every 5 years because they wear out.  It is also a good idea to have your sump pipe drain outside and away from the house and not drain into the local sewer system (in some municipalities, draining the sump pipe into the sewer is illegal).

 

Before you finish your basement, make sure that all of the small, vertical cracks in the foundation wall have been properly sealed.  It is not a good idea to purchase a new house with the basement already finished.  As new houses settle (which ALL houses do) they will develop a few small, vertical (within 30 degrees of vertical) cracks in the concrete foundation.  This is normal and to be expected.  These cracks are best fixed by a professional foundation contractor and using epoxy or high pressure polyurethane foam injection.  I have never seen such a repair fail and most contractors give 50 year warranties.  Once the house has finished settling (usually in 2 - 3 years) and these cracks are sealed, the basement can be finished.  Just make sure that the contractor who finishes the basement properly insulates the walls (closed cell spray foam, Icynene is the best) and installs the required fire stops.  Remember, cheap contractors do cheap work, which is very much more expensive, in the long run.

ASAP, make sure that there are no electric wires that are under the water level.  Also, make sure that you are extra careful with electric devices in wet basements.  If you have standing water (flooding) in your basement, disconnect the main electrical switch or call your local fire department to do it for you!  Only, use ONLY double insulated and grounded vacuums and dehumidifiers.  If you are in doubt about the electrical safety of your basement, stay out of it!  You can live through the water damage MUCH better than you can being electrocuted.

 

The key to the next step is go get the basement dry, ASAP.  As soon as possible, suck up the water with a Wet-Dry vacuum and get some extra de-humidifiers running.  You can easily rent an industrial strength de-humidifier from a restoration company for $100 - 200 a week.  Your air conditioner should also be running (it also de-humidifies).  Add a few fans to keep the air circulating.  Keep the windows closed, the air outside is usually humid after a rainstorm.  The idea is to get all the air in the house, and especially in the basement, as desert dry as possible as quickly as possible.  This dry air not only evaporates the standing water but will also draw moisture out of the walls, carpet and other areas.  Remember that this takes time (usually, 1 - 2 weeks) so take your time and do it right.  If the basement is dried quickly, the likelihood of mold formation is lowered.

 

Take off the basement wall baseboards and drill 1" holes halfway between the wall studs at the base of the walls, about 2" off the floor.  When you re-install the baseboards, they will cover these holes.   The holes will allow moist air from behind the drywall or paneling to be dried as the de-humidifiers suck out the humidity.

 

Usually, if you get the basement dry in 3 to 4 days, there will be little damage and minimal mold formation.  Even if mold does start to form, as soon as you dry out the basement the mold will stop growing (mold requires moisture to grow).  It is usually necessary to rip out drywall and wood ONLY if there is a large mount of mold.  Most times, there will only be a little mold growth and this will be behind the walls.  If you keep the basement dry, the mold will not start growing again.  Mold can be a problem to those with sensitivity or allergies, but mold only affects people because of the spores it puts out.  If the mold is dead and not growing, it isn't putting out any spores.  Most types of mold are harmless.  If there is visible mold growth, there is no reason to have it tested.  If you see mold, you already know it is there and you have no need to find out what kind of mold it is because the remediation will be the same.

 

If you do get mold growth, DO NOT use bleach to clean or kill it.  The EPA has determined that bleach is NOT an effective fungicide for mold growth on drywall and wood and bleach puts out harmful fumes when used in large quantities.  There are much more effective (and less harmful to humans and pets!) fungicides available at the major home stores.  Spray them directly on the affected areas (following the label directions) and let them kill the mold.  These products will soak into the wood and drywall get to the roots of the mold, killing it completely.  When the wood in the walls is completely dry, cover it with a mold encapsulating paint.  This will seal up the mold and keep it from growing further.

 

If you have extensive mold growth, DO NOT TRY TO GO ON THE CHEAP!  Hire a professional and certified mold remediation company to clean the mess up.  Sure, I know this can be expensive, but doing the cheap and easy thing is ALWAYS more expensive, in the long run.  Stay away from handymen or the proverbial "Two guys in a white van".  Mold remediation is a complex and technical trade, requiring a great deal of specialized training and certification.  If not done properly, the mold will come back, and much worse!  Do it right.  The EPA standards state that if the mold is plainly visible, there is no reason to have the mold tested, however, it is highly recommended that the affected areas be air sample tested one week after the remediation is done by an independent mold testing professional, NOT by the remediation contractor.  This testing will determine if the remediation work was properly completed.  Remember, test AFTER and have the testing professional be independent.

 

When all is dry (keep the basement windows closed and run the de-humidifiers, usually, for about a week or two to ensure complete dryness), it helps for your to call a licensed and certified home inspector who is also specifically trained and certified to perform mold testing.  If you can hire an inspector who is also specially trained in thermal imaging, that will help to verify that the basement is fully dry.  Ask the inspector for a mold clearance test, which is an air sample that ensures that mold spores are not present in the air.  Make sure that the inspector does not also do mold remediation work, and that any mold remediation company you hire does not do the testing.  This is a conflict of interest.  If there are mold spores present, call a professional, licensed and certified mold remediation company.  When they are done cleaning up, have the area re-tested by an independent mold inspector.  For large or long sitting (you were flooded while away on vacation, for example) it is also wise to hire a licensed, certified and professional industrial hygienist to evaluate the problem and prepare a clean-up plan.  Most professional mold remediation companies have industrial hygienists on their staff.