Wood floors are a durable and renewable flooring option that can be refinished multiple times throughout their lifespan. When maintained properly, wood floors are capable of lasting hundreds of years, making them one of the most sustainable flooring options available. Generally speaking, most solid wood floors can be sanded six to eight times during their overall service-life. A traditional sand job will remove 1/32” to 1/16” of actual material from the surface of the floor. However, the amount of material that will be removed and the number of times a floor can be sanded depends on several factors, including the type of wood, the thickness of the wear layer, the skill of the contractor, the flatness of the floor, and the equipment used to sand the floor.
Factors That Determine How Many Times a Floor Can Be Sanded
When existing floors need to be refinished, the amount of sandable material on the wear layer of the floor is critical. You should evaluate the thickness of the wear layer in several areas to capture a good idea of what shape that floor is in. The primary determinant of how many times a wood floor can be sanded is the thickness of the wear layer. Solid hardwood floors typically have a wear layer of around ¼” or more, allowing for multiple refinishes. Engineered wood floors can have wear layers ranging from 1/16” to ¼”. Where the wear layer is less than 3/32” (2.38mm), sanding is not recommended. NWFA’s Engineered Wood Flooring Refinishable Program helps identify engineered wood floors that have a sufficient wear layer, ensuring they are capable of being sanded while maintaining their integrity.
Learn More!
To learn more about the NWFA’s Engineered Wood Flooring Refinishable Program, contact John Forbes at john.forbes@nwfa.org.
Removing Existing Finishes
The other component of evaluating a floor for a resand is assessing the finish that is on the floor. For any resand, your first rough sanding is always going to focus on removing the existing finishes, and flattening the floor. The type of finish, number of coats, and colors you need to remove will dictate how aggressive you need to be on your initial cuts.
The first cut normally is done with an abrasive that is coarse enough to cut through the finish, but not so coarse that it requires additional sanding just to remove the scratches they’ve left behind. Some of the high-abrasion finishes, like aluminum oxide, may respond best to fine-grit ceramic abrasives, in order to break the surface tension. This sanding process involves first cutting the floor with the fine-grit abrasive, then going back with coarser abrasives on the belt sander to get to raw wood.
Today’s sanding technology has made it easier to remove these old finishes, including factory finished floors, while preserving more of the wood beneath. Multi-disc sanders, buffers, and edgers with diamond abrasive attachments are capable of breaking through the existing finishes while minimizing the amount of wood removal from the floor surface. This process reduces the amount of time and the quantity of abrasives used to get to the raw wood.
Regardless of the tool and the process used to remove the existing finishes from the floor, the other task that often is accomplished within this same rough sanding pass is the flattening of the floor.
Flattening the Floor
Once down to raw wood, and also on newer floors, the sanding process still may require a belt sander to get the floor flat. This is where your first cut should be angled at 7° to 15° to the direction of the flooring in order to efficiently flatten the floor. The steeper the angle cut, the more aggressive your material removal will be. These are some factors that directly affect the amount of material removed, and the angle of your first cut during a resand:
- Excessive wear and deep gouges that will require more-aggressive sanding, will require additional floor surface material removal.
- Removal of existing bevels from a floor will require significant material removal from the surface of the floor, which will reduce the floor’s lifespan.
- Previous sanding jobs also play a crucial role in the life-expectancy of the floor. Poor sanding techniques, such as uneven sanding caused by a DIYer, or an inexperienced “professional” usually will result in deep drum marks, sander gouges, and that shadow along the perimeter where they tilted the edger against the baseboard.
All of these will increase the amount of wear layer removed from any wood floor significantly.
Reducing Material Removal During Refinishing
Once the existing finishes have been removed and the floor has been flattened, multi-disc sanders are particularly effective in maintaining uniformity throughout the sanding process, reducing the risk of inconsistencies and over-sanding in certain areas. The introduction of multi-disc sanders have revolutionized the entire sanding process, allowing contractors to achieve superior results while preserving more of the wood’s surface.
Choosing the correct abrasive sequence is essential. As mentioned before, the initial rough sanding should use the finest grit necessary to remove the existing finish and flatten the floor. The final sanding sequence is defined by where the rough sanding left off, and also the species being sanded. When compared to a belt sander with a medium- to fine-grit abrasive on the final cuts, the multi-disc sanders offer greater control over sanding pressure and movement, resulting in a more-refined cut-surface with a more-controlled impact on the wear layer. Additionally, effective dust containment systems maintain visibility and prevent over-sanding by allowing contractors to assess progress in real time.
High-quality abrasives often are paired with the multi-head sanders. This pairing helps achieve efficient material removal without leaving excessive scratches behind, further reducing unnecessary material loss.
Run Your Own Test
If you are looking to validate the concept of minimizing material removal from your sand jobs, consider conducting your own experiment. Sand one floor using a traditional sanding method with multiple passes from a belt sander followed by a final sanding with either a buffer or a multihead sander. On another floor, use a different approach: one pass with a belt sander followed by multiple passes with a multihead sander. To quantify the difference, you can either take some before and after caliper measurements of the wear layer, or just weigh the dust collected from each process. The dust produced by the belt sander will be more-coarse, while the dust produced by the multi-disc sander will be finer. This simple test can provide valuable insights into which method removes less material while still achieving excellent results.
By using modern sanding equipment, and by following best practices for grit selection and sanding techniques, your sanding process can extend the life of wood floors significantly. Understanding the factors that impact how many times a floor can be sanded ensures that each refinishing job maximizes durability and aesthetics while preserving as much of the wear layer as possible. With the right approach and the latest technology, contractors can deliver superior results while maintaining the integrity of the wood surface for years to come.
Brett Miller is the vice president of technical standards, training, and certification
for the National Wood Flooring Association in St. Louis. He can be reached at
brett.miller@nwfa.org.
