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How to Waterproof Basement Walls

Waterproofing Basement Walls From Inside

Learning How to waterproof basement walls is one of the simplest DIY projects a homeowner can accomplish themselves.  Perhaps you’re dealing with a wet or musty basement and trying to figure out how you can solve the issue yourself. Today, we provide 5 simple easy steps to waterproof basement walls from inside your home. 

You’ve probably come across many articles on how to waterproof a basement or advertisements for basement wall sealer, that claim they will rid you of the unwelcomed moisture, but do they really work?

Below, we discuss the 4 steps you can take as a homeowner, to waterproof basement walls.  Here’s our step-by-step guide, that once you’re completed – you should have a dry basement.

How To Waterproof Basement 


Step 1:  Find Out Where the Water is Coming from:

Your first order of business – Determine the source of the unwanted moisture.

  • Look for Cracks in Basement Walls:

    Visually Inspect all the exposed concrete basement walls inside of the home – from floor to ceiling.  Look for any hairline cracks that are clearly allowing outside moisture to penetrate inside, and mark location with chalk and or painter’s tape.  This will allow you to easily locate and patch each wall crack, before sealing all basement walls.

  • Look for  Wet Spots in Basement Walls

  • For wet or wet-stained walls without cracks, You can easily determine the cause by taping a piece of aluminum foil (about 1 sq. ft) on the inner side of your basement walls and leaving it there for 24 hours.

  • 1)  If you find condensation on the Outside surface of the foil, then you’re dealing with high humidity inside your basement. Alternatively to waterproofing products, you can fix such a problem using a portable dehumidifier or by installing a whole-house dehumidifier system.
  • 2)  If you find condensation on the Inside surface of the foil, water is seeping through the basement walls from the outside.  The wetness is likely coming from improper drainage around the outside of your foundation walls. 
  • Note:  In this instance, the soil around your house due to a high water table, is pressing against the outside of your basement walls and.  In this case, the most logical problem is a drainage issue outside, due to high amounts of rainfall or unusual flooding. 
  • This issue may eventually need to be addressed, and we will get to that as the last result at the end of this article: “How to waterproof walls from the Outside”. However, in many cases, waterproofing the inside of basement walls is the “First and Best”, and by far least expensive option to start with.


Step 2:  Prep Walls Before Applying Waterproofing:

Use a stiff brush to remove any loose impediments, dirt, or cobwebs from basement walls. In addition, You may notice some white stains on the surface of concrete or masonry walls.  This is called efflorescence and is a powdery substance left from salt pushed through the masonry wall. 

Waterproof paint and sealer won’t adhere to concrete or masonry, with this substance in place.  To neutralize efflorescence use Drylok liquid or Drylok powder etch.

Step 3:   Fix Basement Wall Cracks – From The Inside

Now that you’ve determined how the water is getting inside, it’s time to start fixing your leaky basement walls.

  • Fill Cracks in Basement Walls:

    First, repair all basement wall cracks (hairline cracks, and up to 1/4″ wide) – from Step 1;  using a top brand of epoxy wall crack sealer. We recommend PC Products crack sealer because it is a highly rated, affordable, and permanent concrete crack sealer.  PC Products includes one tube of two-part epoxy and is delivered efficiently to cracks with your own standard caulk gun.  

  • Note:  If you have wide basement wall cracks – exceeding 1/4″ – you consider using a basement wall crack plug material such as Drylok Fast Plug.  This product can even stop water under pressure from the outside.


Step 4:   Buy the Right Waterproof Basement Wall Sealer

Depending on the condition of your basement walls, the severity of cracks, or whether your basement walls have been previously painted, you will need to determine the best basement wall sealer for your particular situation. 

  • Waterproof Paint:

Waterproofing paints: these are acrylic formulas that are similar to regular paint. The difference is that you apply them in a much thicker layer, whether by rolling, brushing, or spraying.

Of all the good waterproof “paint” products on the market, our first choice is KILZ Interior/Exterior waterproof paint – white from Amazon.  It is easy to apply and water-based for simple clean up.  Get Enough – One gallon only covers 100 square feet.  A close second, but slightly more expensive, is the Drylok Waterproof paint for interior or exterior, which is White in color.

  • Silicate-Based Concrete Sealer:

Also known as densifiers, silicate is a mineral sealer that will dry with a “Clear” transparent finish and is therefore only suitable for virgin concrete walls (walls that haven’t been painted or sealed before).  One of the best silicate-based wall sealers on the market is the Siloxa-Tek 8500 product from Amazon.  This is a ready-to-use pre-mixed gallon, with 250 square feet (10 ft. x 25 ft.) of wall coverage.

Silit sealers work by chemically reacting with certain components of concrete or brick – then forming a solid waterproof surface. Apply silicate-based sealers with a roller, brush, or sprayer. It’s relatively simple, and won’t peel or flake off.

  • Concrete coatings:

If you have done extensive basement wall crack repair, you may wish to conceal all the patches with a concrete coating.  Concrete coatings are cement-like coatings that stick permanently to concrete and masonry walls once they dry. Use a heavy brush (preferably with Tampico bristles) to apply this product. Swirl the brush at the end to smooth out the final look. We recommend looking at Floor Tex 40 from Seal Krete.


Step 5:  Waterproof Basement Walls:

Once all wall cracks have been filled or patched, you can begin waterproofing the interior basement walls. This actually one of the easiest parts.

waterproofing basement walls - best home gear
Waterproofing basement walls – besthomegear.com


Note:  If you have applied any crack sealer or crack patch material, allow at least 4 hours of curing time before applying a waterproof sealer or waterproof paint to the walls. 

These are the 3 application methods to Waterproof Basement Walls: 
  • 18″ Paint Roller/Pan
  • 3″ Wide Paint Brush
  • Spray gun/compressor (optional)

In most cases, we recommend using a combination of a 3″ paintbrush, and a wide paint roller with a paint pole attachment – when applying the basement wall sealer. 

Simply, start the painting process with a 3″ wide paintbrush, by cutting in the paint at the floor lines and top of the basement walls.  Follow that step with the paint roller (fill in the box)  to complete, then repeat for each wall.

Optional Paint Spray Method:  If you have the equipment and expertise, you may additionally choose to use a professional paint spray gun and compressor.  However, the best basement wall seal products, especially paints are thicker than normal latex paint.


Alternate Method:  Waterproof Your Basement Walls from the “Outside”

If after sealing basement walls from the inside you still are finding moisture intrusion, you will need to consider removing the water from outside of the basement walls.  This is the surest way to eliminate water intrusion in extreme circumstances. It is also quite expensive and can cost tens of thousands of dollars.

Moreover, it requires professional personnel and equipment to achieve, since it involves digging all around the house to reach the full depth of the foundation walls; installing a waterproof coating on the outside of basement walls, as well as installing drainage tile and a sump pump to evacuate the high water table.


There you have it, our detailed guide on how to waterproof basement walls. Remember, none of these solutions will work efficiently unless the cracks and gaps in the walls are properly sealed. So make sure you use generous amounts of product to fill the cracks and gaps before you seal basement walls.


FAQ – How to Seal Basement Walls


Can you seal Basement Floors using a Basement Wall sealer?

Yes, in fact, you can and should fill any cracks in your floors, and use a basement wall sealer for basement floors.  Do consider, however, that if your using “white” basement waterproof paint, get it tinted first (gray or brown) to hide foot traffic or dirt.

Does waterproof paint stop water from coming in?

On its own, waterproof paint or waterproof sealer for concrete will prevent water intrusion on solid concrete and masonry walls.  However, if you have cracks in walls, you must first plug, or fill the cracks before applying basement waterproofing paint or sealer.

Can I Waterproof Basement Walls Myself?

Yes, if you have even minimal do it yourself skills, you can use our how-to waterproof basement guide above, and waterproof walls from the inside of your home. Doing the job yourself is also the cheapest way to build or accomplish any homeowner repair.

Video:   How To Waterproof Basement Walls from Drylock


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