For many years non porous carpets have typically been installed with the use of pressure sensitive adhesives. This method allowed adhesive to totally dry to a tacky state before installation. These products were mostly heavy 6ft wide vinyl back products or were cut into carpet tile.

New technology has allowed manufacturers to create non-porous broadlooms without the typical heavy backings needed to seal moisture out from penetrating the backing material. The challenge has become installing these products over non-porous surfaces using conventional wet set adhesives where there is no avenue for moisture to escape through either of the surfaces. This article outlines points to be considered to ensure a successful installation when installing these products over a non-porous substrate.

Testing for Porosity

Place a drop of water the equivalent to the size of a nickel on the concrete floor. If the water beads up and is still visible after 30 seconds the floor is considered non-porous. If it soaks in to the surface it is considered a porous surface. Covering existing flooring such as sheet vinyl, VCT, and ceramic tile will classify the substrate as non-porous.

Porosity Effects on Adhesive

Any adhesive that contains water will require that water to be removed in order for the adhesive to cure.  The primary way this occurs is through the use of open time once the adhesive has been spread on the floor. This provides the time for the moisture to dissipate into the air allowing the adhesive partially cure, and increase the tack. The secondary way moisture escapes is through absorption into the substrate surface. The more porous the substrate the quicker the adhesive will cure.  A 3/32 x 3/32 x 3/32 V Notch trowel is the most commonly recommended trowel to use with these types of backings.

Applied Sealers

Curing Compounds: These are applied to concrete to slow the release of moisture from the slab effectively creating a stronger slab. Most of these sealers are designed to dissipate with either foot traffic or UV light. Because they are not intended to stay on the floor, it is required that these compounds be removed before any adhesive is applied.  Sanding with a heavy grit paper or grinding the floor will remove any remaining sealer and could convert an existing non-porous slab into a porous slab.

Moisture Sealers: Most sealers used on concrete floors to block moisture are typically 2 part epoxy systems which when cured leave a smooth slick surface to bond to.  It is important to test the floor before installation with a bond test approximately 2ft x 2ft square to determine if a good bond between the floor and the adhesive is achieved.  A primer is often needed to provide a better surface for adhesion.  Primers such as Koester’s Level Pro Primer E are suitable products for this purpose. These can be rolled on using a standard short nap paint roller.


• The keys to a successful installation with a non-porous broadloom over a non-porous substrate are as follows:

• Perform a bond test ahead of time.

• If the floor is slick and the bond test fails apply an approved primer.

• Use a 3/32 x 3/32 x 3/32 V notch trowel unless otherwise specified.

• Allow the adhesive enough open time until the adhesive when touched will create legs up to 2 inches long.  Use fans if necessary. Open time could vary from 30 min – 1 hr.

• Drop the carpet into the “flashed” adhesive and roll immediately with no heavier than a 75lb roller.

• Keep heavy rolling traffic off the floor for 48hrs.

• Maintain HVAC systems.  Airflow will speed adhesive cure strength.

- Charlie Nielsen, Technical Services Manager