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Cupped Hardwood Floor and Crawl Space - What’s the Connection?

Cupped Hardwood Floor and Crawl Space  - What’s the Connection? Stéphanie Landry Poirier

Tuesday, 13 August 2019

We likely have all may have seen it from time to time; hardwood floors that are cupped, or buckled.  Often, this condition is found at an outside door or in front of a kitchen sink where water has infiltrated the floor. But what if this condition is in a much larger area, perhaps the entire main floor and surface water has not been a problem? Time to check your crawl space.

What causes hardwood floors to cup?

The relationship between wood and moisture.

A moisture imbalance has occurred between the top of the board and the underside or bottom of the board. The bottom of the board usually has a slightly higher moisture content than the top. When the moisture content rises in the bottom of the board, the board expands pushing up the edges and cupping occurs.

If the cupping is minor and is the result of seasonal changes in temperature, humidity, and surface wetting, the floor will likely return to its original position. In some cases, this can take, days, weeks, or longer. For the purpose of this blog however, we will consider how a crawl space may cause cupped hardwood floors and possible solutions.

The crawl space.

If there is evidence of excess moisture in the form of mold, mildew, or high humidity, moisture maybe creeping through the sub-floor into your hardwood flooring causing it to cup.

2 Solutions:

1. To stabilize an enclosed warm crawl space and maintain suitable humidity between the floor and the crawl space when no exterior vents are present.

Action: Dry and install adequate insulation, ground cover and a dehumidifier.

2. To stabilize a vented cold damp crawl space.

Action: Dry, insulate and encapsulate the sub-floor and all piping. This method will keep the humid crawlspace air from getting to your hardwood floor.


1. Contact a local insulation contractor or building supply store for the best solution for your particular home.

2. Never try to repair a cupped floor until all of the sources of moisture have been found and eliminated.

Wood floors add beauty and warmth that is not possible with any other types of floors. Being aware of the challenges helps us to appreciate them for a very long time.