Probably the most difficult decision to make in the floor covering business is whether to install over the existing floor covering material, use an embossing leveler or to use a board underlayment. The following is a general guideline of do’s and don’ts for installers and estimators.
The resilient manufacturer’s guidelines for going over existing materials are:
One Layer Existing: Every resilient manufacturer recommends no more than one layer existing. The main reason is that each layer allows the indentation resistance of the newly installed material to decrease, not allowing it to recover from indentations received from a static load.
Completely and Firmly Bonded: Existing material must be fully adhered to the substrate. No perimeter installed or modified loose laid materials should be present. It also means the material was installed with the proper adhesive and was rolled properly to form a good bond.
When checking old floor covering materials, take a good hard look at the backing of the existing material (Chart 1). A good rule of thumb: the material is usually well bonded if the adhesive is properly applied, rolled and in good condition. The material and adhesive must be checked to be sure of bond. Check the adhesive bond by tapping with a pocketknife to sound out any hollow spots and by visually checking to ensure the bond is adequate.
Check the adhesive’s appearance and color to determine the adhesive type (Chart 2). Next, make sure the existing material is not textured or embossed enough to show through the new material. Most floors have a texture, but there are a few that can be gone over without the concern of telegraphing. Consider the following when making the determination as to whether a new material can be installed over an existing material:
1. Does the existing material have more or less texturing than the new material to be installed? If the existing material has more texture than the new material, then either an embossing leveler or a board underlayment panel must be used. If the existing material has less texture than the material to be installed, there is a good chance the texture will not show through. However, the responsibility of that decision rests with either the retailer or the installer.
2. How much natural light will the floor be exposed to? The more natural light the more likely you are going to see telegraphing of the surface of the existing floor beneath.
The greatest concern for moisture is below and on-grade concrete. Caution should always be exercised when installing over an existing material below-grade. Always look for these signs of moisture; including alkaline salt deposits, discoloration of materials and de-bonding of the adhesive from the concrete.
Don’t forget about moisture around toilets, showers, tubs, sinks, washers, dishwashers, refrigerators and along exterior doors. Look for swelling of the underlayment, underlayment joints show-through, existing material discoloration and a de-bonding of the existing material.
No Existing Heavy Cushioned Or Cushioned-Backed Materials
Check the existing material to determine its firmness. If the existing material is soft and flexible or if you can dig your thumbnail into the material, the new installation will probably have indentation problems. Normally, when a material has been down for a period of time the surface will firm-up with age, but some of the materials with a heavy foam core are not acceptable for laying over. Using an embossing leveler will not help increase the new material’s resistance to indentations.
If the existing material is foam-backed it must be removed. You cannot install a board-type underlayment, as the underlayment will move up and down with the resilience of the material, creating a fastener show-through problem. With vinyl foam-backed materials, the norm is to remove the material, and over a wood substrate, place a builder’s paper down to prevent the adhesive from sticking to the back of the underlayment. This is followed by installing a board type underlayment. When going over concrete the adhesive must be completely removed, as it is still active.
Existing Material is Properly Installed Over Underlayment and Subfloor
Check the underlayment to ensure that it is thick enough, fastened properly and with no signs of fastener popping or underlayment joints showing through. It should also have minimal squeaks. Floors with poor structural integrity are the result of many installation failures.
Floor Waxes and Finishes Must Be Completely Remove
All finishes on the surface of a resilient flooring material must be removed. Adhesives will usually bond to the finish, but the finish is not well bonded to the surface of the material, especially during the drying of the adhesive. Use a commercial floor stripper to remove all finishes.
All Damaged Areas Must Be Repaired Or Replaced
Peaked seams, tears, severe indentations and loose spots must be cut out and repaired with a patching compound. All patching must be done with a cementitious patching compound and allowed to thoroughly dry prior to the use of an embossing leveler, or direct installation.
All Seams Must Be Offset a Minimum 6” From Old Seams
When there is a seam or joint in the existing material, all new flooring seams must be kept a minimum 6" away. In many cases, seam failure is a result of the seam being placed too close to an existing seam or joint. Installers must be aware when cutting seams over an existing material not to cut into that material.
Knowing when to go over an existing material, when to use an embossing leveler, or to use a board-type underlayment has always been a difficult decision. The situation requires a lot of thought and investigation regarding the material, adhesive and substrate. Failure to review all of these variables will result in an unsatisfactory installation and a dissatisfied customer.