The Problem

I was called to inspect a house with cupping of the 20-year old, 2 1⁄4-inch oak flooring.

What Happened

An ice maker in a minibar leaked while the homeowner was on a weekend vacation. A restoration company placed drying mats on the hardwood flooring around the minibar and dehumidifiers in the basement room under the minibar. When it was time to refinish the flooring, a hardwood floor refinisher inspected the wood floor and noticed cupping in areas distant from the ice maker. He suspected another source of moisture and wanted those issues resolved before he refinished the floor.

The Inspection

I inspected the house approximately one month after the ice maker leak. Moisture levels in the flooring around the ice maker were up to 28%, as compared with 9–10% throughout the rest of the house. Flooring within 5 feet of the ice maker area was cupped near 0.025 inch with buckling; the rest of the house was cupped up to 0.015 inch.

The temperature and relative humidity (RH) in the house were 74 degrees Fahrenheit and 65%. The thermostats on the house's two AC systems were both set to 72°. The supply air at a floor register at the east end of the house was 60°; at the west end it was 71°. In a properly functioning AC system the difference between supply air and room air temperature should be around 20°.

The space above the basement's drop ceiling was open to a mechanical room housing the two AC systems. A large fan there exhausted air to the exterior, while a large vent in the opposite foundation wall provided make up air above the drop ceiling. This was bringing a massive amount of humid air into the house. Efflorescence and water stains were on the foundation walls. Irrigation sprinkler heads surrounded the foundation.

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The readings showed the restoration company did not fully dry the ice maker leak and showed the rest of the flooring was affected by elevated humidity levels in the house that were not caused by the ice maker leak. This cupping resulted from improperly functioning AC systems, along with an excessive amount of moisture intrusion via the ventilation system and foundation walls.

How to Fix the Floor

Moisture issues in this house from the ice maker, basement ventilation and foundation need to be corrected. The AC systems need to be repaired, or preferably replaced since they are 20 years old. Once a new environment is established and the floors acclimate to the new environment, any remaining floor issues can be addressed.

In the Future

The floor refinisher made a good call. Fixing a floor before fixing moisture issue(s) will likely result in another fix to the floor.


See more on this topic: Moisture & Wood Floors


Craig DeWitt, PhD, PE, is president of RLC Engineering LLC in Clemson, S.C. Craig has a PhD in engineering and specializes in wood, moisture and indoor environments. He has provided inspection and consulting services for over 20 years.