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How to Seal Basements And Keep Water Out

Sam Smith Foundation Repair Consultant

create a powerful barrier for your basement by combining it with interior applications and good drainage.

If you’re in search of accurate costs related to waterproofing your basement, you’ve come to the right place.

Here’s what you’ll learn by the end of this article:

  • Reasons why your basement leaks
  • How to waterproof your basement
  • How to make sure your waterproof seal is working
  • How to save money on basement waterproofing solutions

Most homeowners have or will at some point face water problems in their basement or crawl space. The underground placement of your foundation walls and concrete floor leaves them open to water vapor and liquid water from the saturated soil around them.

Many people don’t know how to find the source of their basement leaks, and fewer know how to waterproof their concrete walls and slab to keep their basement dry.

In this article, we will discuss the most likely reasons your basement might be leaking, how to waterproof your basement from the inside and outside, and how to keep costs as low as possible while you do so.

Why Do Basements Leak?

Below are the reasons that are probably causing your leaky basements. These are the common problems most homeowners face.

Settling Cracks

Small cracks in your concrete walls and basement floor form when your concrete is poured and begins to cure. They can grow over time and usually reach their widest within a few years of curing. These cracks offer water an easy way into your foundation.

Worn Plastic Barriers

Slabs and even basement walls are sometimes treated with a plastic vapor barrier during construction. Soil movement, concrete settling, and exposure to the elements can wear the barrier down over time and leave openings for water vapor or liquid water to seep in and cause water damage.

Hydrostatic Pressure

Hydrostatic pressure happens when the soil outside your foundation gets saturated from rainwater or groundwater. The heavy dirt can add enough pressure to your concrete to force water through.

Efflorescence from Water Leaks

If you’ve ever noticed white, powdery-like staining on your concrete walls, you’ve seen efflorescence. It’s a residue of minerals and salts left behind on your walls after water seeps in and evaporates into your basement air.

Is Exterior Waterproofing Effective?

basement waterproofing system

Exterior waterproofing is usually most effective for blocking water vapor, but some solutions are fully waterproof and can be very good at stopping leaks.

We usually recommend that homeowners not rely on exterior waterproofing to prevent a wet basement and instead create a powerful barrier by combining it with interior applications and good drainage.

We also recommend you contact one of our foundation professionals to evaluate your unique situation to ensure your home is safe and fully sealed.

What Is The Best Exterior Waterproofing Product?

Polyurethane sealants applied to the outsides of your basement walls are usually the best exterior waterproof solution.

They’re very good when used with a drainage system to reduce harmful water near your foundation and an interior waterproofing paint.

What Are The Best Interior Waterproofing Products?

Interior waterproofing can be better at sealing your basement because it’s easy to reapply and gets worn down more slowly.

Below are the best basement waterproofing products for the insides of your concrete walls.

Concrete Coatings

Concrete coatings like hydraulic cement are usually cementitious solutions that are added to your basement wall to seal cracks.

They bridge gaps and reinforce the concrete to help it stop water from getting into your home.

Silicate-Based Sealers

Concrete sealers can be applied with a brush or roller, making them an easy DIY solution to water issues.

They bind with the concrete on a molecular level and make it less porous. They are clear coats that won’t change the appearance of your concrete much.

Waterproofing Paint

Waterproofing paint

There are many waterproofing paints for basements that are easy to apply and good at stopping water intrusion. They are also good solutions for DIYers because of how similar they are to drywall paint to apply.

Plastic Panels and Sheets

Plastic treatments are good if you have frequent basement water problems. They are barriers for liquid water and direct it down to a drainage system in your concrete slab.

They work best with drain tiles or floor drains connected to a sump pump.

How To Waterproof Your Basement

Your waterproofing system can be as simple or as complicated as you’d like and can include just exterior solutions, just interior fixes, or both.

Below is a good mix of solutions that I’ve found works very well for fixing most wet basement problems.

Step 1 – Start with Good Drainage

Tile drain in basement

Even the best waterproofing product won’t be fully waterproof. Your goal with this step is to limit the amount of water your products need to stop. Start with installing gutters, downspouts, and gutter extensions.

Grade the soil around your foundation to help move heavy rain away from your concrete. Consider installing a French drain system or footing drain too. These things together may actually stop basement flooding for good.

Step 2 – Seal Cracks in Your Foundation

The easiest point of entry into your basement for water is through gaps in your concrete, so you need to seal any foundation cracks. Use an epoxy sealer or caulk on wall cracks or hairline cracks in your slab.

Step 3 – Use an Exterior Waterproofing Sealant

A sealant on the outside of your basement walls can require expensive excavation but is usually worth it if your home isn’t equipped with dampproofing already.

Apply dampproofing, an exterior waterproof paint, or another waterproof coating to help stop water from reaching the insides of your walls.

Step 4 – Use an Interior Concrete Sealer

A silicate-based sealer on the insides of your walls will make your concrete less porous and lower the chance of water reaching your basement.

Step 5 – Use an Interior Waterproof Paint

Finally, a waterproof paint applied over the concrete sealer will help stop water that gets through the concrete from coming into your basement.

How To Check That Your Waterproofing Is Working

Waterproofing materials don’t always make a complete seal because of problems with the application or wear on the product as time goes on.

You should use the below tests to periodically check to make sure that your waterproofing products are still working.

Dampness in the Basement

Most water that slowly seeps in through your concrete or foundation cracks will evaporate into the air and make your basement or crawl space damp.

Your waterproofing system may be failing if the space under your home feels damp.

Rust Stains

efflorescence on walls

Rust stains are like efflorescence but form on your walls because of metals in your soil. These are a good sign that you are still having problems with water seepage.


Efflorescence is powdery white staining that forms on your walls when evaporating water leaves salt behind.

Peeling or Bubbling Paint

Waterproofing that you apply to the interior walls doesn’t stop water from wicking through your concrete.

When it does, it gets trapped between your paint and your wall. Paint usually starts to peel or bubble if water continues to build up behind it.

Mildew & Mold Stains 

A damp or wet basement will almost always cause mold and mildew to grow and can help identify weaknesses in your waterproofing.

Musty Smells 

The mold or mildew in your basement may grow behind drywall if you have a finished basement and may not be visible.

You can usually smell if they are forming, though. Your basement or crawl space will have a musty odor.


Water that has evaporated often condenses on surfaces in your basement. You may notice windows fogged on the inside or damp drywall.

An easy DIY test for less obvious condensation is to attach a square of aluminum foil to the wall with tape on all four sides. Check for condensation on the inside of the foil after 24 hours.

Clogs in Your Gutter System

Gutters, downpipes, and extensions are some of the best tools for stopping water intrusion. A clog or leak in your gutter system that causes pooling of water near your foundation will often be a warning sign that water intrusion is inevitable in that area.

Improperly Graded Soil

Runoff naturally flows with the slope of soil to some extent. It will move into your foundation, where it’s more likely to cause water intrusion if it isn’t graded correctly.

Are There Other Ways To Waterproof Your Basement?

Waterproofing systems can include a large number of different methods that I haven’t mentioned here. Two of the more popular methods are footing drains and interior drainage systems.

Footing drains are installed near the bottom of your foundation and are best for removing groundwater from the soil. We haven’t included this in the guide above because runoff is a much more common problem, and footing drains don’t do much to remove surface water.

Additionally, footing drains are one of the most expensive drainage systems you can install because of the heavy excavating that is needed.

Interior drainage systems like floor drains, sump pumps, and interior tile drains are common too, but I haven’t included them in the guide above because they are reactive solutions that don’t fix the root cause of the water problem.

How To Save Money When Sealing Your Basement?

The best way to save money when sealing your basement is to fix the real problem that is causing water intrusion. Waterproofing basement walls with silicate-based sealers, dehumidifiers, and waterproofing paint works well but doesn’t solve the root cause of the issue.

Installing a gutter system and a French drain and grading your soil are cheap DIY projects that can permanently fix your problems. We recommend doing this first. You may not need more waterproofing, and you will help stop leaks from happening again.

You can also save some money sealing your basement if you develop a system that works best for your home. Using concrete sealer, waterproofing paint, and dampproofing will help make the best seal but may be overkill for your water problem.

Fix drainage issues and then apply only the products that are needed to avoid overspending on your system.

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Sam Smith Foundation Repair Consultant
SHORT BIO: Hey, I'm Sam Smith. I'm one of our service techs here at Regional Foundation Repair. I'm here to help you learn more about your home's foundation. I've been doing this for a while, so I have a few insider tips and tricks to share!

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