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United States

Helping with Wood Floor Cupping

No one wants wood floor cupping, but you can help customers find solutions to their floor cupping problems.


Hardwood floor cupping is caused by a moisture imbalance in the flooring.  It is a condition when a wood floor gains more moisture on the underside of the board causing the boards to swell on one side, giving the outside edges of the plank a raised look while the center remains flat. This U shape can cause gaps to occur between the planks, leaving many homeowners in a state of worry and concern.

While all wood floors can be affected by cupping, the wood floor professional can help alleviate customer concerns and find solutions to serious cupping issues. Be sure to give your customers this important information regarding wood floor cupping.

Floor cupping can be a seasonal issue.
Seasonal temperature and humidity fluctuations will have an effect on wood floors. It is natural for wood floors to expand and contract throughout the year, and seasonal Relative Humidity swings can have a big impact here. Remind customers that minor cupping may be due to seasonal changes and that this kind of cupping usually disappears on its own when the Relative Humidity stabilizes. 

Floor cupping can be a moisture issue.
If you suspect that customers are experiencing wood floor cupping outside of seasonal effects, then a different moisture issue needs to be identified. First, make sure customers have stable humidity conditions in their homes. Help them troubleshoot any potential HVAC issues. Remind customers to use humidifiers/dehumidifiers to help stabilize the relative humidity levels in their home in the range of 40% - 60%.

Floor cupping can be a maintenance issue.
If moisture levels in the home are stable and wood floor cupping is still an issue, the source of moisture still needs to be identified. Check with customers to see if other maintenance issues could be the culprit: leaking pipes, appliances, subfloor issues or foundation issues. Remind customers that finding the source can take more time than they might expect, and other professional help may be needed.

How to prevent floor cupping.
If your customers are in the process of getting floors installed, remind them of some simple ways to prevent floor cupping:

  • Before installation, let wood acclimate to normal living conditions in their home.
  • Always clean up spills on floors ASAP. Never wet mop wood floors.
  • Monitor moisture levels in the home.
  • Check with installers to ensure a proper moisture barrier is installed on the subfloor.
  • Never sand down a floor that’s cupping.  Wait until moisture issue has been resolved and then if necessary, the floors can be sanded. If floors are sanded prior to resolving the moisture issue, the floors can end up with a convex shape after the floors are sanded and the moisture dissipates. 

To best prevent wood floor cupping from moisture in the substrate (concrete or wooden subfloors) , an effective moisture barrier is needed between the subfloor and wood floor planks. Bona R540 is a superior moisture barrier/primer that can be used in new and existing construction. Bona R540 is a one-component roll-on moisture barrier that dries fast, allowing for immediate nail-down installation.

Bona Professional Adhesives work well in conjunction with the R540 to help alleviate moisture issues as well as potential  popping, creaking and squeaks that may occur after the floor is installed Our silane-based adhesives have the right amount of elasticity and strength to get the job done right the first time with exceptional results.