Basement Waterproofing 101

Gemma Johnstone
Written by Gemma Johnstone
Reviewed by John Bryant
Updated March 15, 2022
Two friends playing video games in basement
Photo: Monkey Business Images / Shutterstock

Maybe something as simple as leaky gutters is causing the tiny lake in your basement after big rain, but often you'll need to consider basement waterproofing solutions

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Do your socks get damp every time you go downstairs, are your kids complaining about the funky smell, or are there patches of mold or mildew developing on the walls? Water in your basement isn’t always something to panic about, but it can lead to serious structural issues if ignored. 

Sometimes simple preventative steps, such as routine gutter cleaning, can be enough to keep any problems at bay. But, depending on what the problem is, you may have to consider a combination of basement waterproofing solutions to divert the water away from your home's foundations.

Understanding more about what can cause a wet basement and how you can tackle the problem will help you formulate a plan of action.

What Can Cause Water Damage in Your Basement?

The first step to keeping water out of your basement is identifying the cause. Often a basement inspection will reveal that the cause is something simple and easy to remedy. There are times, however, when the problem will require more effort to fix. Some common causes include:

  • Clogged or broken gutters

  • The existing exterior waterproofing medium is no longer effective

  • Deterioration in sewer lines

  • Poor soil, landscape sloping, or drainage issues preventing water from directing away from your home

  • Cracks or other imperfections in your basement walls, floors, or windows

  • Clogged drains

  • Foundation shifting

  • Condensation from excess humidity or dampness

  • Poor initial foundation construction

Main Types of Basement Waterproofing

If your leaky basement problems are not solvable by a simple step like gutter cleaning or repair, you’ll need to consider a basement waterproofing solution. There isn't a one-size-fits-all approach—it depends on what is causing the problem and the damage already done.  Often a combination of factors are at work, and you’ll need to employ more than one waterproofing technique for long-term effectiveness.

Unless you’re an expert, this isn’t a project you’ll want to handle yourself. Call in a basement waterproofing company to assess the situation and tailor their approach to best suit your circumstances.

Interior Basement Waterproofing Solutions

Interior basement waterproofing techniques rarely require as much work as exterior solutions, and they’re more affordable. If the leak is small or you can’t conduct exterior basement waterproofing for some reason, they can be helpful on their own. However, many homeowners pair interior solutions with exterior work.

Interior Sealant Application

Applying a waterproof paint or sealant to your basement's interior walls and floors is simple and economical. It prevents water from seeping through any fine cracks or small holes.

However, this usually isn’t enough on its own, as it doesn’t address the underlying reason for the water seepage. Also, these sealants don’t form tight seals on painted walls and won’t work on wide cracks.

“Many times, sealants will trap water in the foundation walls and can create more problems down the road,” says Angi expert John Bryant of AquaGuard Waterproofing Corp in Beltsville, Maryland.

Installation of a Floor Drain and Sump Pump

Although external work is more common, interior floor drain and sump pump installation are possible. The sump pump collects any standing water and pumps it back out of the house.

The shallower excavation work involved in this type of project is not as extensive or costly as that needed for external drainage. But, it doesn’t address the underlying reason for the water coming in, so it often occurs alongside exterior work.

Exterior Basement Waterproofing Solutions

Exterior waterproofing solutions are often the most effective long-term because they stop the water from getting into your basement in the first place. But they’re also the most expensive and complex methods and require professional help.

Installation of an Exterior Trench Drainage System

A common solution is to excavate the soil away from the foundation and install a drain tile, also known as a French drain. You may also need an external sump pump and soil grading. While this is the most extensive and expensive waterproofing solution, it’s usually the most effective.

Exterior Sealant Application

Your pro may also recommend applying sealants and epoxy injections to external walls and cracks. It’s a more intensive process than interior sealing, as the soil around the foundation requires removal.

Structural Repairs

Typically structural repairs, like cracks in the wall, are patched up, sealed and support the foundation at the same time as drain tile installation.

Average Costs for Basement Waterproofing

The cost of basement waterproofing can vary considerably. It will depend on the solutions used, the size of your basement, the age and structure of your home, and the type of foundation it has.

Minor repairs or carrying out basic interior sealing yourself may only cost a few hundred dollars. But installing a waterproofing system could range from around $3,500 for an internal one to $30,000 or more for major exterior excavation work.

Because it can be complex and costly, it pays to get quotes from several local basement waterproofing contractors before work commences.

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