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Basement waterproofing: solutions for wet basements

Finishing a basement is a popular way to increase living space, but basements are prone to moisture problems and leaks. When I was a kid, it was my job to run downstairs with towels to sop up water from the carpet whenever we had a heavy rainstorm. In my first house, I discovered a problem with moisture that would lead to me gutting the entire basement. Here are some basement waterproofing methods to deal with moisture and water problems and help you stay dry.

Signs of a water or moisture problem?

A sure sign that water is coming in the basement.

Some water problems are more obvious than others. For example, if your basement floor is wet after a rainfall, then you know water is coming in from outside. However, some moisture problems are not as obvious. Evaporation may take place before the problem is evident and you are never the wiser. However, you might find a white chalky residue on the wall. This is efflorescence which is the mineral deposits left behind after water that has infiltrated the foundation has evaporated.

Efflorescence: The mineral deposits left behind after the evaporation of water.

If the problem is buried behind a wall and vapor barrier, or under a carpet, evaporation cannot take place and the water accumulates resulting in property damage and mold growth. Not only is this a comfort issue, but the mold can lead to health complications as well. And then there are financial implications. Nobody wants to spend thousands on a basement renovation only to have to rip everything out after a few years to address the water and moisture issues that should have been addressed from the beginning.

Where is the water coming from?

There are a number of ways that water can find its way into your basement:

  • Cracks in the foundation
  • Moisture infiltration through the foundation or slab
  • Hydrostatic pressure between the foundation and slab
  • Condensation

The Moisture Test

Take a piece of vapor barrier or other plastic or tin foil and tape it in place on the floor or on the foundation wall.  Be sure to seal all edges with tape so it is air tight.  If moisture collects on the underside of the plastic, you have infiltration.  Moisture collecting on the outside of the plastic is condensation caused by moist air coming in contact with a cold surface.  This can be controlled by adjusting the humidity using a dehumidifier.  It can also be prevented by proper installation of insulation and vapor barrier. The object is to stop warm moist air from coming into contact with cold surfaces.

Your first line of defense

If you listen to The Money Pit Radio Show with Tom Kraeutler and Leslie Segrete, you have no doubt heard Tom give this advice. Because he gives this advice at least once a week, sometimes more. START OUTSIDE.

Keep as much water as possible away from your foundation, because any water that collects around the foundation could potentially find its way into the house. That means making sure that

  • Landscaping slopes away from the house.
  • Gutters (eaves troughs) are clean and water flows easily.
  • Downspouts discharge the water far enough away from the house (at least 4 feet).

And just how important are clean gutters?

This is our house. The upper level eaves trough drains to the lower level trough which drains to a down spout. Take note of the downspout between the upper and lower level trough.

The downspout was clogged with leaves and dead insects and other gunk that had collected into a pretty solid mass.

The mass that was clogging the downspout

This mass in the downspout caused the upper gutter to overflow. That water saturated the ground and eventually saturated the block foundation.

It appears to be a bit damp-ish.

We only learned of this problem after opening up the wall to install a French drain system in response to a flood that originated from the other side of the basement shortly after we moved in. There were no outward signs– no stains on the drywall, no wet carpet– that would have informed us that we had an issue in this area.

Foundation Solutions

While addressing the gutters and drainage outside the house goes a long way to preventing a wet basement, but you may want, or need, to take more drastic measures. You can stop the water OUTSIDE with an exterior membrane system, or you can control the water INSIDE with an interior French drain system.

Exterior Membrane System

By far, the best way to prevent water problems is to prevent water from coming into the house in the first place. As a retrofit, it is necessary to dig around the house down to the footings. Drainage tile is repaired or replaced. Any foundation cracks are repaired and the foundation is coated with tar or similar product. Then the membrane is fastened to the foundation. The membrane prevents water from coming in contact with the block. A weeping tile system at the footings directs the water to either a storm sewer, or to a French drain that dispels it away from the house or directs it to a collection pond or low point on the property.

The downside of this system is the necessary destruction of landscaping, driveways, patios, decks, etc. It may take a year or two for the back fill to settle enough to replace the landscaping.

The photos below are of the installation of a membrane system on my late father’s house prior to putting it on the market.

Repairs are made to the weeping tile.
The foundation is sealed.
The membrane is fastened to the foundation.
More drainage layer, then backfill.

Interior French drain system

This system works well for leaks that originate between the slab and foundation wall.

Weep holes drilled in the lowest blocks below the slab prevent the build-up of hydrostatic pressure. A weeping tile system controls any water coming in through the holes, carrying the water to a sump pump or directly to a storm drain.  This requires breaking up the slab around the perimeter of the basement. This can be a big drawback if you already finished your basement. But then, if you are considering the options for waterproofing, chances are pretty good that you will be renovating the basement to fix water damage anyway.

We had this type of system installed in our current house by our local Basement Systems franchise. It’s what they call their WaterGuard interior drainage system. It channels any water to the TripleSafe sump pump that we had installed at the same time. The gallery below shows the installation of this system.


Condensation occurs when warm moist air comes in contact with a cooler surface, such as the foundation wall or slab floor. Think of the water droplets that form on a cold can of pop (or, better yet, a bottle of beer).

The key is to stop water or moisture from passing through the concrete foundation and evaporating inside the basement increasing the humidity. However, humid air is still a fact of life in many parts of the country,

dehumidifier will help reduce the humidity in the air and proper insulation and vapor barrier will prevent that warm air from coming in contact with the cooler foundation wall where it can condense. As well, you will want to insulate your cold water pipes. On a particularly humid day, we actually had wet lines across our basement floor directly under “sweating” pipes.


  1. Keep water away from the foundation. Make sure gutters are clear and downspouts discharge several feet away from the foundation. Landscaping should slope away from the house.
  2. Stop water OUTSIDE with an exterior membrane system. AND/OR
  3. Control water INSIDE with an interior French drain system.
  4. These steps will help control humidity levels inside the house, but an additional dehumidifier may be necessary.
  5. Stop condensation with proper insulation and vapor barrier and by controlling the humidity

Listen to the podcast

I cover this topic in Episode 35 of The Thumb and Hammer Home Improvement Podcast: H2Woes: Fixing Wet Basements



  1. Alice Carroll

    Wow, I never knew that landscaping is one of the indirect ways to waterproof a basement. Whenever it rains, my basements tends to pool up with water but it never manages to become an actual flood. Perhaps it would be best to still get a wet basement remediation service before I start taking steps in waterproofing the place.

  2. Mia Evans

    Thanks for helping me understand that having an exterior membrane system will protect the outside of the house while installing an interior french drain system will protect the inside from water damage. I guess this is one of the things we should consider when it comes to waterproofing system installation for our future house, and we need to decide as soon as possible if you want to have an informed decision when it comes to our home. The best thing we can do is to talk to a contractor with a good reputation and have good reviews from their previous clients in order to believe that the recommendations will actually work well for the design of the house and the climate or weather conditions we will have in the long run.

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