Problems Causes and Cures


Deep scratch that go through the refinish.

What it is: A crushed spot in the wood.

  • High heels.
  • Dropped heavy objects
  • Metal tips on furniture legs.
  • Shipping damage.

Remove and repair the damaged boards. The entire floor may need to be resanded and refinished.Institute good floor maintenance procedures, such as removing high heels and using floor protectors.

Cupped Floor

What it is: Cupping occurs across the width of the individual pieces of flooring. The edges are high and the center is lower. It generally develops gradually.

  • A moisture differential within individual pieces of flooring, usually excessive moisture on the underside of the flooring. More subtle cupping can be caused by lack of proper acclimation (this is generally permanent cupping). Potential sources of excessive moisture include:
    – Building leaks
    – Poor drainage
    – Plumbing leaks or overflows
    – Leaks from dishwashers or refrigerator icemaking units
    – Wet or damp basements/crawlspaces
    – Concrete subfloors that have not cured
    – Plywood subfloors with excessive moisture
    – Poor or no ventilation
    – HVAC system not operating.
  • Solid flooring also may cup when a wood floor experiences conditions that cause rapid drying on the surface. This condition occurs with gaps as the flooring shrinks.
  • Low humidity levels can cause cupping in engineered flooring that is usually referred to as “dry cupping.” With dry cupping, the wood in the top layer attempts to shrink across its face while the shrinkage of the plywood backer is considerably less. (Dry cupping is also often accompanied by “face-checking”—cracks in the board faces).

Never attempt to repair a cupped floor until all of the sources of excessive moisture have been located and eliminated. This can be verified only with a moisture meter that takes readings of the underlying subfloor. As long as the wood is not permanently deformed or damaged, the flooring will return to its original shape and size when the excessive moisture is removed. This may take
weeks, months, or even an entire heating season. Attempting to sand a cupped floor while it is still too wet may cause subsequent crowning when the floor dries. Flooring that does not return to its original shape, even after completing
an entire heating season, probably is permanently deformed. (Taking moisture readings at different levels in the wood flooring also can help determine this—if there is a difference of 1 percent or more between the top and bottom of the
boards, they probably are not done drying.) If the boards are permanently deformed, the cupped edges may be sanded off. For floors that have cupped due to drying, relative humidity should be increased. Relative humidity below 20 percent is considered very dry for wood flooring, and it is suggested that humidification be provided under such conditions.