Product Description

KOVARA® AB 300 is a patent-pending, self-adhered, pre-fabricated moisture barrier designed to protect floor coverings from staining, warping and adhesive deterioration that may result from water vapor emissions and alkaline salts infiltrating through the concrete slab. 

KOVARA® AB 300 membranes self-adhere directly to the concrete subfloor with its own specialty designed moisture and alkaline-resistant adhesive suitable in conditions up to 99.5% relative humidity. The unique adhesive bond addresses membrane movement or buckling when heavy rolling loads and heavy foot traffic are expected. The unique adhesive is protected by a split release liner until placement.

Product Advantages

  • Installation in a fraction of the time of fluid-applied moisture barriers
  • Self-adhered to subfloor with a specialty designed adhesive to prevent movement under heavy rolling loads and foot traffic
  • Split adhesive release liner allows quick peel-and-stick application
  • Reduced labor costs and improved project capacity for contractors
  • Reduced downtime and business disruption for building owners
  • No shotblasting or surface grinding required
  • Self-leveling surface preparation only needed for uneven floors
  • Backed by 10-year limited replacement warranty (details below)
  • Patent pending


Thickness 41 mils (not including 2 mil release liner)
Roll Size 5’ x 100’ (500 sq. ft.)
Roll Weight 90 lb.
Shelf Life 1 year
Pallet quantity 12 rolls

Product Uses

KOVARA® AB 300 membranes can be used under any of these approved floor coverings:

  • Carpet tile
  • VCT – vinyl composition tile
  • LVT / LVT – luxury vinyl tile / luxury vinyl plank
  • Homogeneous sheet vinyl
  • Rubber flooring
  • Engineered wood
  • Laminate flooring
  • Bamboo
  • Broadloom carpet
  • Wood court flooring
  • Resilient sports flooring

The following specialty floors require review to verify existing conditions and use to ensure the best installation; please contact your local GCP flooring sales rep or GCP Technical Services for review:

  • Heterogeneous sheet vinyl
  • Ceramic tile
  • Porcelain tile
  • Natural Stone

For each roll of KOVARA® AB 300 membranes, the following additional installation components are required for sealing seams:

  • 1 roll of KOVARA® MBX Seam Tape
  • 1-2 rolls of KOVARA® Double-Sided Tape

Safety and Handling

Read and understand the product label and Safety Data Sheet (SDS) for each system component. All users should acquaint themselves with this information prior to working with the products and follow the precautionary statements. SDSs can be obtained by contacting GCP toll free at 1-866-333-3SBM (3726).


KOVARA® moisture barriers are backed by a limited 10-year replacement warranty. You can find the entire KOVARA® AB 300 membrane warranty information at gcpat.com, or contact your GCP Applied Technologies sales representative for details.

Technical Services

KOVARA® AB 300 membrane customers benefit from GCP’s Technical Service team, providing field support for successful job completion. Please contact GCP with any questions on the proper use of KOVARA products. 

Installation Guidelines

Slab RH Testing and Pre-Installation Requirements

All concrete slabs, regardless of grade, should be tested for moisture content using the approved method of RH in-situ probe testing in accordance to the latest version of ASTM F-2170. Slabs should only be tested 28 days after pour and once the slab has been allowed to realize appropriate service conditions, which includes permanent HVAC operations and complete enclosure of the space.

Acclimate all flooring materials and adhesives in accordance with the flooring manufacturer’s recommendation. Floors and the planned installation space should be conditioned at least 48-72 hours prior to the start of the installation. Environmental conditions should remain constant during the installation and after the installation is completed. Permanent HVAC should be in operation and set to between 65°F - 85°F.

Always inspect KOVARA® AB 300 membranes, KOVARA® tapes, and flooring materials for physical damage and/or defects. The installation of defective or damaged materials will void any future rights to a claim.

KOVARA® AB 300 membrane installations, including floor preparation and finished flooring, should not be started or installed where further trade work on or above the product will be required. Always read the associated documentation and installation instructions for all flooring, adhesives and underlayment to be installed.

When selecting adhesives, KOVARA® AB 300 membranes are considered a non-porous surface. The appropriate adhesive, recommended trowel size and/or spread rate should be specified by the flooring manufacturer. If considering adhesives classified for wet-set applications, contact GCP Technical Services for specific application recommendations.

Concrete Substrate Preparation

All of the recommended work practices contained in these guidelines are in conformance with the most recent version of ASTM F710 and acceptable industry guidelines as approved by the Resilient Floor Covering Institute (RFCI). The installation contractor is solely responsible for determining the suitability of a slab, moisture testing and use prior to starting the installation of KOVARA® AB 300 membranes.

The concrete slab should be smooth, dry, clean and structurally sound. Dust and other contaminants may have a detrimental effect on the bond of the KOVARA® AB 300 membranes and KOVARA® tapes to the substrate and overall performance of the system. 

All surface cracks, grooves, depressions, control joints or other non-moving joints greater than 1/8” should be filled and sanded smooth with the plane of the substrate using modified Portland cement patching compounds or an epoxy injection. Crowns in slab or protrusions should be smoothed in the same manner. Patching materials should be allowed to completely dry prior to the application of KOVARA® AB 300 membrane and finished flooring materials.

Existing adhesives should be completely removed to provide a tack-free substrate. Please follow the RFCI’s “Recommended Work Practices for Removal of Existing Floor Covering and Adhesive.” Substrates that have been installed with cutback adhesives should only be removed in strict accordance with local, state and federal guidelines. If the slab has been abated using a chemical process, immediately contact GCP Technical Services for additional encapsulation and installation recommendations.

Do not use gypsum- or plaster-based patching compounds underneath KOVARA® AB 300 membranes. Areas requiring deep fill, other than a skim coat, should only be repaired using a MRP (moisture resistant patch) or exterior grade patching/repair compound. Consult the manufacturer for additional recommendations on these types of substrate repair products.

KOVARA® AB300 Membrane Installation

Begin by laying 5’0” on-center chalk guidelines for KOVARA® Double Sided Tape. These lines will serve as an outside guide for the tape, to increase accuracy. If starting at a wall, adjust initial measurement by 2” (4’10”) to allow tape to center properly. Place the KOVARA® Double Sided Tape using the chalk lines as the guidelines for the outside edges keeping the tape straight and flat. Pass over the tape using a 6” putty knife to ensure flat and consistent bond with the substrate. DO NOT REMOVE THE RELEASE FILM FROM THE KOVARA® DOUBLE SIDED TAPE AT THIS TIME.

Unroll KOVARA® AB 300 membrane with seams centered on KOVARA® Double Sided Tape. Dry fit membrane net to within ¼” of all walls, being careful to not create compression and back bubbling at seams and vertical changes. At each seam, fold back both sheets of KOVARA® AB 300 membrane halfway, to expose KOVARA® Double Sided Tape, taking care not to move the membrane from its original position. Remove exposed half of release liner from both KOVARA® AB 300 membrane segments and remove release liner from KOVARA® Double Sided Tape. Gently roll the exposed membrane back into place, taking care not to fold or flop the material into a position that would cause buckling or bubbles. Do not place KOVARA® AB 300 membranes onto exposed KOVARA® Double Sided Tape without removing the membrane release liner, as the release liner will adhere to the tape. 

Continue process, removing release liners and adhering all KOVARA® AB 300 membranes to substrate. Small fill pieces can be rolled in the length to remove the liner, or completely removed and placed back into place with adhesive exposed.

Complete the installation by applying KOVARA® MBX seam tape across the top of all side seams and cross seams. Maintain adequate tension on the tape when setting to minimize bubbling and wrinkling. Roll the seam with a hand roller until tape finish turns from glossy to matte, indicating a complete bond with the membrane.

Finished Flooring Installation

Sweep the KOVARA® AB 300 membrane to remove any installation debris, dust or dirt that may have accumulated during the application. Complete the finished flooring installation in accordance with all manufacturer guidelines. Apply the adhesive directly to the surface of the KOVARA® AB 300 in accordance with the manufacturer’s recommendation for non-porous substrates. 

With the continuous advancement of flooring technologies, it is impossible to list all of the products that can be effectively installed using KOVARA® AB 300 membranes. If your product is not included in the list of approved floor coverings, please contact GCP Technical Services for additional information. Always follow the specific flooring manufacturer’s recommendations for installation over non-porous substrates.

Perform necessary planning and layout of all flooring materials. We recommend lighter chalks as they will be clearly seen on the surface of the KOVARA® AB 300 membrane.  Always adjust the layout to avoid seam joints falling directly over a KOVARA® AB 300 membrane seam.

Caution should be taken to ensure the KOVARA® AB 300 membrane is not cut, damaged or punctured. Some adhesives may take longer to flash off and cure compared to installations over porous concrete. Always use a new trowel with the recommended notch for each application.

DO NOT install broadloom carpeting requiring crab stretching, stay nailing or heavy knee-kicking to align patterns; they can cause distortion to the KOVARA® AB300 membranes.

Do not mechanically fasten wood flooring through KOVARA® AB 300 membranes. Regarding floating flooring systems, carefully follow all flooring manufacturer’s recommendations for the installation. When using a thin-set application method for ceramic, porcelain, or stone tile, either a polymeric modified or unmodified setting material is acceptable. Refer to the local building codes and ANSI/TCNA guidelines for approved installation practices. 

Initial Maintenance 

Upon completion of the finished flooring installation, KOVARA® AB 300 membranes require a minimum of 120 hours (5 days) before conducting initial ‘wet’ cleaning or maintenance. Failure to follow this requirement may result in improper adhesive curing and/or failure of the adhesive bond. Always clean and maintain flooring with neutral pH cleaning products.

Permeance <0.1 perms ASTM E96-B
Maximum PH Allowed 12 -
Fungi and Mold Resistance Does not sustain mold growth ASTM G21
Flammability Passes ASTM D2859
Dimensional Stability Meets most floor covering requirements ASTM D7570
Radiant Panel Meets Class I ASTM E648
Smoke Density <450 NFPA 258
Residual Indentation    Passes (<0.005 in @ 250 lbs.) ASTM F970



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We hope the information here will be helpful. It is based on data and knowledge considered to be true and accurate and is offered for consideration, investigation and verification by the user, but we do not warrant the results to be obtained. Please read all statements, recommendations and suggestions in conjunction with our conditions of sale, which apply to all goods supplied by us. No statement, recommendation or suggestion is intended for any use that would infringe any patent, copyright or other third-party right. 

KOVARA and VERSASHIELD are registered trademarks, which may be registered in the United States and/or other countries, of GCP Applied Technologies, Inc. This trademark list has been compiled using available published information as of the publication date and may not accurately reflect current trademark ownership or status.

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GCP Applied Technologies Inc., 62 Whittemore Avenue, Cambridge, MA 02140, USA

This document is only current as of the last updated date stated below and is valid only for use in the United States. It is important that you always refer to the currently available information at the URL below to provide the most current product information at the time of use. Additional literature such as Contractor Manuals, Technical Bulletins, Detail Drawings and detailing recommendations and other relevant documents are also available on www.gcpat.com. Information found on other websites must not be relied upon, as they may not be up-to-date or applicable to the conditions in your location and we do not accept any responsibility for their content. If there are any conflicts or if you need more information, please contact GCP Customer Service.

Last Updated: 2021-02-05