When can an engineered wood floor be refinished? Two of the most valuable and defining attributes of wood flooring are that they can last hundreds of years, and they can be refinished. The idea that a wood floor can be refinished is no longer common knowledge to today’s consumers.
Refinishing a wood floor can mean different things to different people. To keep this article clear, I will be using the term “refinishable” to describe the process of sanding the wood floor back to raw wood and then adding new color and coatings.
Assessing an existing floor to determine whether it is refinishable or not can sometimes be a challenge.
First, you need to identify whether the floor is a solid or engineered wood floor. Even for wood flooring professionals, it’s sometimes hard to tell whether the floor is solid, engineered, or just a fancy picture of wood glued to plastic.
Solid Wood Flooring
Solid wood flooring is exactly what the name implies, a solid piece of wood from top to bottom. Solid wood can be refinished numerous times during its service life.
Engineered Wood Flooring
Engineered wood flooring is real wood flooring as well, but instead of a solid piece of wood from top to bottom, it is only the topmost layer of real wood that allows it to fall within the wood flooring category. The topmost layer is referred to as the wear layer or the lamella. The platform (or core) of engineered flooring is made using layers of wood veneers, solid lumber fillets, or some type of composite material. No matter what the overall construction of the engineered product is, the thickness of the topmost layer determines whether the floor can be refinished. The thickness of this wear layer varies by product. Some engineered wood floors may only have a paper-thin veneer of real wood that has been peeled from the log. Others have a sawn wear layer that can be up to ¼” (6.35mm) thick (comparable to the wear layer on most ¾” solid wood floors).
Wear Layers on Engineered Wood Flooring vs. Solid Wood Flooring
After you determine what type of flooring product you are assessing, you then need to determine how thick the wear layer is. In general, the wear-layer thickness of any wood floor (solid or engineered) that is being considered for a refinish should not be less than 3/32” (approximately 2.5mm). The number of times a given floor can be refinished depends on the skill of the person sanding the floor, the type of equipment being used, the thickness of the remaining wear layer, and the flatness of the installed floor. A “normal” sanding process should remove a minimal amount of wood, often less than 1/32”. An additional check for floor flatness can be verified with a laser level. Localized high areas or humps will cause greater depth of surface material to be removed.
Measurements often can be made at floor registers or by removing transition moldings. Where there are sufficient gaps between boards, an automotive feeler gauge may be used to measure the thickness of the flooring down to the top of the tongue. Be cautious though; this method works well with solid wood flooring, but may not be a reliable testing method with some engineered flooring since the wear layer on some engineered wood flooring may not be as deep as the tongue.
In situations where you are unable to pull a vent or transition piece to view a side profile of the existing flooring, you may have a couple of other options to help you determine what you are dealing with.
Check to see if there is quarter round or base shoe that can be removed to give you a look at the side profile. Look for an area where another floor covering, such as carpet, adjoins the flooring. See if you are able to pull the carpet back enough to get a side profile of the product. For prefinished flooring, check to see if there happens to be any leftover flooring in the basement, attic, garage, or storage rooms. When everything else fails, and with the permission of the building owner/occupant, find an inconspicuous area of the floor and drill a hole small enough to plug, but large enough to determine what it is you are working with. Use a drill bit large enough to give you a good view of the entire thickness of the flooring. This should help you see how thick the wear layer is. Then patch the hole with a dowel or wood plug and stain/color to match.
Some other unique characteristics of the wood floor also could affect how the floor should be assessed for refinishing. This assessment should focus on the existing thickness of the wear layer in comparison to how much material would need to be removed for a proper refinishing process.
When sanding eased- or beveled-edge wood flooring, the appearance of bevels may not be consistent after sanding. In the case of a micro-bevel product, it is possible that the bevel will be eliminated. If the bevel is to be eliminated, you will need to measure from the lowest point of the bevel profile to determine if there is enough wear layer remaining for an adequate sand job. In addition, the customer should be made aware that sanding a beveled-edge product will change the profile of the bevel and the look of the floor.
Similar to bevels, textured floors also require the lowest elevation in the flooring surface to be evaluated. Due to the variation in the surface wear layer thickness of textured floors (scraped, wire-brushed, sculpted), these types of floors are extremely difficult and often cannot be sanded. The wear layer may be less than the recommended 3/32” thickness in many of the low areas of the floor, which would become the lowest point that the remaining floor would need to be sanded to in order to get it flat.
For someone who does not take these preliminary steps, but takes on the challenge of refinishing a floor, the resulting consequences can be costly and devastating. Time and again, we hear of flooring contractors who took on a refinish job, and then ended up sanding through the veneer. When this happens, your best option may be to get creative with paints, dyes, and graining tools. When this is not feasible (as shown in the photo below), it often leads to floor replacement. Obviously, neither of these options is appealing. For more on what happens if you sand through a veneer, refer to the Inspector’s Report article on page 112.
Lastly, it is not always necessary to fully sand the floor to restore the finish. Unless the floor has visible dents, wear patterns, or permanent cupping, or the customer wants to change the color of the floor, a maintenance recoat may suffice. Maintenance recoats are an untapped side of our industry that can also give most wood floors new life. You can find more on the maintenance coating side of our industry in the NWFA Wood Flooring Sand and Finish Guidelines.
Keep an eye out, as the NWFA is launching a voluntary certification program for engineered wood flooring that helps sales professionals and consumers identify products with wear layers thick enough to be refinished.
Brett Miller is the vice president of technical standards, training, and certification for the National Wood Flooring Association in St. Louis, Missouri. He can be reached at email@example.com.