How to Seal a Concrete Basement Floor

June 8, 2010

The floors in a basement are made of concrete. Of course, water and water vapor can get into a basement through the floor and cause mold, mildew and a musty odor to develop. Also, a wet or damp floor will cause any paint to blister and peal. Any carpeting placed on the floor will collect moisture and be damaged. A concrete basement floor can be sealed against water, water vapor and gas transmission.

Sodium Silicate Vapor Impermeable Concrete Sealers

It is best to use a sodium silicate penetrating sealer because it is vapor impermeable on an interior concrete floor. These are better than a surface film sealer because the surface film sealers still let water and water vapor into the concrete. The surface sealers trap the water under them and eventually the pressure exerted on to the surface film causes it to blister and fail.

The sodium silicate penetrating sealer works by soaking into the concrete up to 4 inches. Once inside the concrete, it reacts with the naturally occurring free lime of the concrete. A crystaline structure is formed from this reaction. This seals the microscopic pores of the concrete floor. After curing the concrete will be hardened and densified. Water and water vapor will remain on the exterior portion of concrete, away from the living space.

Gas and Vapor Transmission

Because the microscopic pores of the concrete are filled, gas and vapors cannot travel through the concrete. They are blocked from migrating from the surrounding soil and into the basement living area.

Stops Efflorescence

The chalky white substance that is sometimes seen on a basement floor is called efflorescence. This is simply the solid salts leaching out or the concrete and being deposited after the water has evaporated. While it is natural for this to happen, this efflorescence will be stopped after using the penetrating concrete sealer.

Penetrating Sodium Silicate Vapor Impermeable Concrete Sealer Advantages

  • Stops water vapor transmission 
  • Prevents water seepage 
  • Reduces gas and vapor migration 
  • Paintable surface 
  • Appearance remains the same 
  • Hardens the concrete

Easy Application

Application of concrete sealers can be done with a brush or roller. However, most people use a pump up garden spray with a flat fan pattern spray tip. This gives the most even coating of materials. Of course, the basement floor should be clean, dry and free of grease prior to application.

This article is written by Aaron Kuertz with Applied Technologies Aaron has been in the waterproofing industry since 1998. Applied Technologies is a manufacturer and supplier to professional waterproofing contractors and homeowners in the United States.  To learn about basement floor sealers, visit


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