Wave-Like Marks on Larger Floorboards


Wood floors are often seen with small wave-like bands. These appear on flooring usually across grain, and range between 5-20 mm in length. When a hand is run along the grain over the wave marks, a slight ripple may often be felt. It is not uncommon to see a larger wave-like mark effect with bands between 20 and 80 mm wide on floorboards.


Wave-like marks come in a variety of shapes and sizes, all of which are developed by different causes. The narrower wave marks can be seen on unfinished products prior to sanding. These may occur through the feed speed moulder being set too high. However these usually disappear with normal sanding and are not necessarily regarded as a product fault.

Similar small wave marks can also be caused by various faults in sanding machines. Faults with sanding equipment tend to happen more frequently with drum sanders as opposed to continuous belt sanders.

Larger wave marks are often caused by the unevenness of the floor itself. When working on a flooring of this type, imperfections transfer through the wheels to the sanding machine, which then affect the floor.

Broader wave marks are seen when the floor possesses various imperfections or undulation. Furthermore, incorrect electrical supply and worn/ damaged wheels may also be a cause for such an issue.

Diagnosis / Identification

There are ways in which different marks on the wood flooring can be identified. By locating the issue, diagnosing the problem becomes a much easier task. Small wave-like marks in flooring prior to the installation process for example, identifies minor machining imperfections.

Small wave-like marks after the installation of wood flooring will indicate a fault with the sanding machine used to finish the project.

Having larger wave-marks will mean the electrical supply was not adequate for the job. Additionally, there may have been a fault with the sanding machine or even damaged or worn wheels.


Each type of mark has a different solution, which should leave the flooring with the best possible results. The first of which is progressively sanding the floor, starting at 40 or 60 grit, without skipping papers, in order to repair small wave-marks that were present before any sanding had taken place.

If small wave like marks are visible after sanding, the recommended step would be to thoroughly check the installation, as well as the seams on abrasive paper. The drive belts and pulleys may also require closer inspection.

A drum sander could be a potential issue as it may not function correctly if worn, or if it is out of balance etc. Using a continuous belt sander as a replacement of a drum sander presents an alternative option. If you encounter broader wave marks, be sure to check that wheels are not excessively worn, damaged or out of round.

Correct faults with the sander, re-sand with a continuous belt sander, or a multi-disc equivalent ensuring that you with overlap the previous pass. Do not use a sanding screen, as this will tend to highlight wave-marks.


  • Fix all loose boards before any sanding commences.
  • Resolve any structural issues that may lead to undulation of flooring.
  • Be sure that you are using the correct electrical supply.
  • Ensure that sanding equipment is regularly maintained.