Should you use Flex Seal on basement walls?

Author: Urban Hahn  |  Last update: Monday, April 28, 2025

Flex Seal Liquid is thicker than paint and dries into a strong, rubberized coating. It can also help seal out air, water, and moisture and is chemical and mildew resistant - making it a great choice for your basement walls.

Does Flex Seal really work on basement walls?

The only sealing of basement walls that will actually work, is sealing them from the outside. And flex seal wont do well in that application.

Where should you not use Flex Seal?

We do not recommend using Flex Seal on foam. Some foams may react poorly with Flex Seal, and may warp or dissolve. We also do not recommend using it in situations where it is subjected to high heat or pressure (such as engine radiators) or gas tanks. We do not recommend the use of Flex Seal spray on vinyl.

What is the best way to seal basement walls?

5 Steps to Effectively Waterproof Basement Walls
  1. Remove All Standing Water and Verify That the Area is Completely Dry. ...
  2. Clean and Prepare the Area. ...
  3. Plug Holes and Cracks. ...
  4. Reseal Windows, Doors and Window Wells with Caulk. ...
  5. Apply Waterproof Coating.

Can you use Flex Seal on concrete walls?

A: Yes you can use Flex Seal on concrete.

How to Waterproof Basement Walls With Flex Seal Products

How long does Flex Seal last on concrete?

Depending on the environment, coats added, and maintenance, many people have found Flex Seal will last for years without cracking, peeling, or losing any of its strength or sealing properties.

How to waterproof a concrete wall?

Use a wire brush or pressure washer to clean the surface thoroughly. Repair any cracks or gaps in the concrete with an appropriate filler. Choose the right waterproofing material There are several types of waterproofing materials available, including liquid coatings, membranes, and sealants.

What is the best sealer for a basement?

Epoxy is a robust sealer known for its durability and resistance to moisture, making it an excellent choice for basements that are used frequently or are prone to dampness. This type of sealer creates a thick, protective layer over the concrete, which helps prevent water penetration and resists stains and chemicals.

Why not use Drylok on basement walls?

Drylok is an indoor waterproofing paint, and while that has been mentioned several times, it is a crucial detail. Waterproofing your basement from the inside may be cheap, but it is by far the least effective way of waterproofing your basement, and this is because it never stops the source of the water.

Should I seal my basement concrete walls?

Sealing basement walls helps protect your home from water damage, ensuring a dry, healthy living space. Whether you're dealing with minor dampness or recurring leaks, understanding how to waterproof your basement can save you time, money, and headaches in the long run.

Which Flex Seal is best for concrete?

Flex Seal Liquid is optimal for sealing, repairing, and weatherizing concrete. It works by sealing out air, water, and moisture and is mildew, chemical, and UV resistant. You can either brush, roll, dip or pour the liquid directly onto the concrete surface.

What happens if Flex Seal gets wet?

Once dry, Flex Seal's watertight, rubberized coating can withstand water, heavy rains, snow, and more. Flex Seal can be applied to a wet surface or moist environment in the event of an emergency. However, it will always adhere better to a clean, dry surface.

Can I put drylok over Flex Seal?

Flex Seal Liquid is not compatible with Drylock.

Can I waterproof my basement myself?

For minor leaks and moisture, you can use hydraulic cement, silicate concrete sealant, and silicone caulk to fill cracks and gaps. You can apply these products yourself, followed by waterproof paint. Larger problems may call for exterior drainage improvements or professional foundation repairs.

How do you remove Flex Seal from concrete walls?

If the Flex Seal is still wet, it can be removed with a dry cloth or paper towel. If the Flex Seal is cured/dry, it can be removed with acetone, denatured alcohol, or mineral spirits.

Can I use Flex Seal on wet concrete?

A: Yes! Flex Caulk is 100% waterproof and can be applied to wet or dry surfaces. It will even cure underwater.

What is better than Drylok for basement walls?

Superior Waterproofing Performance: Crystalline Waterproofing offers a higher level of waterproofing performance compared to Drylok Extreme. Its crystalline technology penetrates into the concrete, forming insoluble crystals that block capillary pores and microcracks, effectively preventing water penetration.

Is Kilz good for basement walls?

RECOMMENDED USES:

This product is ideal for use on above and below grade basement, masonry, garage, and foundation and landscape walls. Use on properly prepared, interior or exterior surfaces, including: • Masonry • Stucco • Cinder blocks • Brick Not for use on floors and walls with active water leaks.

Does Drylok cause mold?

DRYLOK® Waterproofer not only repels water but also inhibits the growth of mold and mildew. By creating a hostile environment for these harmful microorganisms, DRYLOK® ensures a healthier living space for you and your family.

Is Flex Seal good for basement waterproofing?

Luckily many Flex Seal users have had great success with using our products in waterproofing their basements. We've received hundreds of 5 star reviews, check out a couple of them below: “Over the last few winter snow melts we noticed more and more wet areas in our basement.

What is the cheapest way to seal a basement?

Which is the cheapest basement waterproof? The cheapest basement waterproofing method is typically applying a waterproof paint coating, which can cost as little as a few dollars per square foot for materials if doing it yourself. Caulking cracks and opting for interior solutions is cheaper than exterior excavation.

What is the best concrete wall sealer?

Best Concrete Sealers: Our Top 7 Picks
  • Best Sealer Overall: TotalBoat Concrete Coating.
  • Best Acrylic Sealer: Foundation Armor Concrete Sealer.
  • Best Penetrating Sealer: Ghostshield Siloxa-Tek Concrete Sealer.
  • Best Glossy Sealer: Black Diamond Stoneworks Stone Sealer.
  • Best Sealer for Basements: RadonSeal Concrete Sealer.

How do you stop water from seeping through concrete walls?

If the water is seeping through the concrete walls themselves, it may be necessary to waterproof the exterior of the walls. This may involve applying a waterproof coating or membrane to the walls or installing a drainage system to direct water away from the building.

Can you use drylok on concrete walls?

DRYLOK® Masonry Waterproofer is not recommended for use on anything other than bare masonry and concrete surfaces. It can be applied to porous terra cotta, concrete, stucco, and cement.

How do you waterproof an existing foundation wall?

How to Waterproof House Foundations From the Outside
  1. Step 1: Excavate the Soil Around the Perimeter of your Foundation. ...
  2. Step 2: Clean and Prep Your Foundation Walls. ...
  3. Step 3: Fix Damage to Your Foundation Walls. ...
  4. Step 4: Apply a Waterproofing Membrane to the Outside of the Foundation. ...
  5. Step 5: Install Window Wells.

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