How to Waterproof Concrete

You can waterproof concrete by applying an impermeable barrier to its surface. These barriers come in a variety of forms, including liquid waterproofing gels, crystalline slurry compounds, rubberized sheets, cementitious waterproofing, bentonite sheets, and waterproofing paint.

Do not let concrete fool you. While it appears to be an exceptionally sturdy building material, concrete is just as susceptible to damage as anything else. Taking the time to waterproof it using the proper materials ensures that it lasts.

Why It Is Important to Waterproof Concrete

On top of being required by law in most locations, waterproofing concrete is essential to the preservation of a concrete structure.

When water comes into contact with concrete it erodes away at the concrete. Over time this causes aesthetic issues like stains, but what you should be worried about is the structural damage.

By the time you are able to see the effects of water on concrete the damage is done. Any stability it had has been compromised, and any underlying structure has likely been damaged as well.

Some specific situations that can really affect concrete are:

  • Floods
  • High rain levels
  • High rise buildings
  • Extended humidity

Waterproofing concrete prolongs its life and keeps it durable. It also protects the rebar underneath from rust and erosion.

Because concrete is usually used as material for foundations, ensuring its stability is essential to the preservation of the entire structure.

How to Waterproof Concrete

What To Do Before You Waterproof Concrete

If you are waterproofing a new structure make sure the concrete is properly cured. This means that you must allow the concrete to set while maintaining appropriate humidity and temperature and over a specific length of time.


  • Relative humidity greater than 80%
  • Temperature greater than 50°F
  • A length of time greater than three but less than fourteen days

Regardless of whether the concrete is new or old, you should make sure that it is clean and dry. Use a scraper to remove any paint or residue from the surface. Sweep up any and all dirt, then use a specialized cleaning solution to deep clean the concrete.

HYDE 19424 Wall and Floor Scraper

HYDE 19424 Wall and Floor Scraper

  • Heavy-duty wall and floor scraper with offset design that makes it easier to get edge under material.
  • 12-Inch length for working in tight spaces.
  • Cushioned grip with protective hand stop.
Rust-Oleum 301243 Cleaner

Rust-Oleum 301243 Cleaner

  • Heavy-duty, multi-purpose cleaner/degreaser for residential and commercial applications thoroughly cleans surfaces and remove contaminates.
  • Use before coating concrete surfaces to promote adhesion of paints, stains and sealers.
  • Environmentally safe cleaner will not harm grass or plants and covers 200 sq. Ft. Per gal.

Rinse with water and let it dry for at least 24 hours before waterproofing.

Different Ways to Waterproof Concrete

There are many ways to waterproof concrete, though most work in the same way. Choosing a specific method can depend on how much concrete you need to cover, whether the surface is uniform, how you want the surface to appear post-waterproofing, and what is most readily available to you.

The most popular methods of waterproofing are:

  • Liquid waterproofing gel
  • Crystalline slurry compound
  • Rubberized sheets
  • Cementitious waterproofing
  • Bentonite sheets
  • Waterproofing paint

Read on to learn how each method works.

Liquid Waterproofing Gel

Liquid waterproofing is the most common method of waterproofing concrete. It generally involves a gel that turns into a rubber-like coating once it is applied.

This method is especially successful when working with structures like basement walls or foundations, and it is verified for working with concrete that is below grade.

You can use a mop or a roller to rub it on, and then give it ample time to dry. When it finishes drying you can backfill soil up against it to help secure the layer.

Liquid Rubber Color Waterproof Sealant

Liquid Rubber Color Waterproof Sealant

  • Flat roofs, metal roofs, sloped roofs, planter boxes, foundations, sheds, basements, metal, wood, concrete and more.
  • Final membrane has over 1000% elongation preventing adhesion failure, and is UV Stable stopping the sun from degrading the product.
  •  Liquid Rubber Waterproof Sealant/Coating is water based, containing no solvents, VOC's or harmful odors.
Wooster Brush R232-9 Epoxy Glide Roller Cover

Wooster Brush R232-9 Epoxy Glide Roller Cover

  • The product is Epoxy Glide, 9", 1/4" Nap, dark grey, smooth roller cover.
  • Easy and simple use kit, great pickup, release and flow for fast results.
  • Shed-resistant fabric for all epoxies and urethanes.

Crystalline Slurry Compound

crystalline slurry compound works by covering the concrete with a chemical that reacts with water and dry cement particles. The compound forms needle-shaped crystals that fill in any cracks or pores in the concrete.

These altered crystals also create a permanent barrier by blocking pathways for both water and waterborne contaminants. Moisture will continue to activate the crystallization process over the life of the structure.

You can apply one coat or even repeat the process for increased protection.

Xypex Concentrate

Xypex Concentrate

  • Resists extreme hydrostatic pressure.
  • Becomes an integral part of the substrate.
  • Can seal hairline cracks up to 0.4 mm.

Rubberized Sheets

If you want a more uniform look on your concrete structure you should look into using rubberized sheets. These large squares are backed with an incredibly sticky adhesive that, once stuck to concrete, is virtually impossible to remove, thus creating an impenetrable barrier.

While this gives you a smoother look overall, it is more expensive. You cannot move the sheet once it has adhered to the concrete, and seams between the sheets tend to be an entry point for moisture.

Using rubberized sheets is a great additional measure if you find your concrete structure lacking. You can even purchase them in smaller sizes if you only have an issue in one area, like the bottom portion of a wall.

MFM SubSeal40 Waterproof House Wrap

MFM SubSeal40 Waterproof House Wrap

  • Prefabricated, 40 mil self adhering sheet-type waterproofing membrane.
  • Roll Length: 75 ft.
  • Case Weight: 62 lbs.

Cementitious Waterproofing

Cementitious waterproofing products like MasterSeal 583 apply to concrete like a layer of mortar.

These additional layers dry hard, so they are likely to crack and need repairs, but they are a proven method of waterproofing a concrete structure.

MasterSeal 583 Formerly Super Thoroseal

MasterSeal 583 Formerly Super Thoroseal

  • MasterSeal 583 Formerly Super Thoroseal Waterproof Coating.
  • Harder than the wall itself.
  • This Product is manufactured in United States.

Bentonite Sheets

When using bentonite sheets you attach them to the concrete, and whenever water penetrates the membrane it causes the clay to expand instead of affecting the concrete structure.

While this works when it works, it is not foolproof. You must use water to activate the process, and you will not be able to tell that it is effective until the water is already present.

Waterproofing Paint

You can use waterproofing paint like Kilz Waterproofer on properly prepped and cured concrete surfaces. This method is especially great if you do not want to add much to the surface of the concrete but you still need to waterproof it.

It is especially useful for smaller structures or areas where the risk of water damage is not as intense.

KILZ Interior/Exterior Basement and Masonry Waterproofing Paint

KILZ Interior/Exterior Basement and Masonry Waterproofing Paint

  • This premium, interior/exterior paint is formulated to waterproof and seal porous concrete and masonry surfaces both inside and outside your home.
  • Using nanotechnology, this paint forms a barrier to help stop water infiltration while an alkali resistant coating provides a long-lasting, durable and decorative finish.
  • Apply this paint on properly prepped and cured above and below grade basement walls, masonry walls, retaining walls, cinder and concrete blocks, stucco and brick.

Keep Concrete Waterproof

When building there are many laws and regulations that require you to waterproof concrete, especially if you are working with a high-rise building. Beyond that, waterproofing helps prolong the life of the structure and protects it from erosion, mold, mildew, and stains.

Take the time to clean concrete and allow it to dry before starting to waterproof it. Pick a method that works best for your situation. For example, areas where water damage is more likely should uses thicker impermeable barriers like liquid waterproofing gel or rubberized sheets.

Thinner waterproofing layers like paint can be used for smaller projects, or on surfaces that have a unique shape that would otherwise be compromised by a thick waterproof layer.