For anyone who has experienced water damage in a basement, you know how costly and frustrating it is to make repairs. And that’s to say nothing of the heartache of ruined furniture, carpet, or special items. But basement flooding is something you can prevent. Before you have a real issue on your hand, learn how to identify the causes of water in a basement, along with ways to waterproof basement walls.

Causes of Water in a Basement

Many things can cause water or dampness to get into a basement. Here are some of the most common culprits.

  • Condensation can occur when warm, moist air hits the foundation walls, cool or cold-water pipes, rusting appliances, or carpets. If it looks like your basement walls are “sweating” you probably have condensation.
  • Runoff is rain or melted snow that is improperly routed away from the house and can seep into a basement. To determine if this is the cause of water in your basement, check to see if your basement walls and floors or crawl space is damp or wet after a snowstorm or rainfall.
  • Groundwater swelling happens when an underground water table overflows. A water table overflows when it is full to capacity and the soil is no longer able to drain the water. You can think of the ground as a sponge — it will soak up water, but only to a point. And once it’s soaked up all it can, the excess water can flood your basement. To determine if this is your problem, look for water bubbling between the floor and wall joints, or if there is water present after a rainstorm.
  • Floor cracks if you have cracks in your basement floor, water can seep into your basement from an overflowing water table. The cost of repairing floor cracks can run anywhere from $620 to $850 per 20 square feet, depending on the contractor.
  • Sewer & pipes can cause a leak in any room of your home, which is why it’s smart to fix any cracked or frozen pipes or a sewer. Sometimes identifying this problem is as easy as checking your pipes for drips, but some pipes may require a professional inspection.
  • Window wells if you have wells around your basement windows, water can collect in them causing drainage problems. If this happens, pressure can build up causing the water to seep through gaps or cracks around the window. You can install a window well drain for around $500-$2,000.

How to Waterproof a Basement

There are several options for waterproofing your basement, and they generally fall into one of two categories: interior or exterior.


For every interior waterproofing idea, it’s important to note that none of these will work unless all gaps and cracks are properly sealed. Be sure to fill any gap or crack with either polyurethane caulk or an epoxy filler. Here are several ways for sealing basement walls.

  1. Waterproofing Paint
    Basement waterproofing paint is an acrylic form of paint quite similar to any other wall paint. It can be applied to previously painted walls and can even paint over it once it’s cured. Since you have to apply it pretty thickly, one gallon may only cover about 75 square feet (or fewer). Each gallon costs around $35 and can be applied easily as a DIY project.
  2. Silicate-based Concrete Sealer
    This kind of sealer is called a densifier and only works on walls that haven’t been sealed or painted. They’re great for brick or concrete walls, as the sealer soaks into the material and chemically reacts with the ingredients within brick and concrete, forming a hard, waterproof surface. Since these sealers soak in, they won’t peel or flake off your walls, and you can paint over them (just check the label to be sure). This option is a great DIY project, costing about $40-$50 per 1-gallon can that will cover up to 200 square feet. Just note that you will need at least two coats.
  3. Concrete Waterproofing Coating
    A concrete coating is a thick coating that is almost like cement; once it dries, it will permanently adhere to masonry walls and concrete. You can apply it with a heavy brush made from Tampico bristles. The only downside to this approach is that you cannot apply it to previously painted surfaces. However, it is one of the cheapest options, costing about $30-$40 for one 5-gallon bucket that will cover 100 square feet.
  4. Plastic Sheets and Panels
    This approach to waterproofing a basement is best done when you have an interior drainage system. Water will run down the back of the plastic into a drainage system in the basement floor where a sump pump will move it out of the basement completely. The plastic sheets and panels won’t stop water from getting through the walls, but it will stop it from ruining any items in the basement. This kind of system will cost about $3,000 to $5,000 for a 20-by-20-foot basement.


Although there are many options for waterproofing your basement by the interior, the best way to waterproof it through the exterior. In order to waterproof your basement from the exterior, you will need to excavate around the entire house to the full depth of the foundation walls (be sure to call 811 before beginning any digging project). You can then install a waterproof membrane or coating covered by drainage panels. These panels will provide an easy pathway for any water to flow down into an exterior French drain at the base of your foundation. The water can then flow away from your foundation to a storm drain or another part of the property. You can also use a sump pump to move it away from your foundation. Unfortunately, this option is far more expensive, ranging from $15,000 to $30,000; however, it will pay off in the long run.

Dos & Don’ts

There are some really important things to note before you pick an option for waterproofing basement walls.

  • DO determine the source of the water before attempting any repairs.
  • DO take steps to keep water away from your basement.
  • DO fill cracks with hydraulic cement.
  • DO apply a masonry waterproofing product to bare interior basement walls.
  • DON’T make wall repairs with standing water in the basement.
  • DON’T forget to address window well leaks.
  • DON’T apply a sealer over painted walls or efflorescence.
  • DON’T forget interior drainage solutions.

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