Sub-Floor Humidity

Sub-floor humidity refers to the level of moisture in the air within the sub-floor space. High levels of humidity in this area can lead to dampness, mould growth, and timber decay, which may compromise the structural integrity of the floor and the property. Monitoring and controlling sub-floor humidity through adequate ventilation or dehumidification is crucial for maintaining a healthy and durable flooring structure.

Use a hygrometer probe in the sub-floor to monitor relative humidity. A probe can be pushed through cracks in floorboards or by discretely drilling out a hole. The sub-floor relative humidity will fluctuate. If it remains above 85%RH for an extended period then:

  • Check for a leak, such as a mains water leak.
  • Check that there is no rot to sub-floor timber.
  • Consider installing a fan into the sub-floor to blow air out.
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