Cutback is the black asphalt-based adhesive that was frequently used to install vinyl asbestos tile, asphalt tile and vinyl composition tile. In the replacement market today, most adhesives including carpet and resilient flooring adhesives are not compatible with cutback because it is an oil based product. As such, it is necessary to remove or encapsulate cutback residue before installing floor coverings since the residue of cutback can bleed through standard patching or leveling compounds and react with the adhesive and/or discolor some resilient flooring materials.
If the installation is over a wood subfloor, the easiest way to deal with cutback is to cover the entire floor including the floor covering with plywood underlayment and install the new floor covering on top of the new plywood. However, if the goal is to completely remove the asbestos containing materials from the building, then the flooring and the wood substrate beneath it must be removed and new plywood underlayment installed.
For concrete substrates, is advisable to remove cutback residue mechanically rather than with a chemical adhesive remover. Use the wet-scraping method as outlined in the RFCI "Recommended Work Practices for the Removal of Resilient Floor Coverings". Do not sand, grind or blast this residue as the airborne dust may contain asbestos, a known health hazard. Wet scrape the floor so that the cutback residue is nothing more than a thin transparent layer, much like a stain on the concrete. Allow adequate time for the concrete surface to dry and then apply an approved underlayment or patching compound. Be sure the product is approved for use over cutback residue. Many products will adhere to cutback residue but not all such products will prevent bleed through.
In the case of trowel applied patching compounds, two coats are usually necessary in order to assure the complete coating of the floor. While chemical adhesive removers may be used, most floor covering manufacturers and the Resilient Floor Covering Institute (RFCI) have specific warnings against the use of solvents and adhesive removers since any residue of the adhesive remover left on the floor or in the cracks of the concrete may also dissolve the new adhesive or discolor floor coverings. If a chemical remover has been used, it is advisable to mechanically clean the surface of the concrete and then apply a self-leveling underlayment.
FCICA: Installing Resilient Flooring over Cutback Adhesive
October 1, 2006