How to Acclimate Wood Floors in Northern Climates

By Lee Senter

Most hardwood and engineered hardwood flooring products need to be acclimated to their environment prior to installation.

The problem in northern climates is in winter the air is typically extremely dry and relative humidity is very low. When hardwood is acclimated to its environment in summer, the air is moist and relative humidity is quite high.

Hardwood and associated flooring products swell and shrink according to relative humidity. In other words, if hardwood is acclimated to a high relative humidity in summer, the floor planks can shrink significantly in winter unless the building’s HVAC system can maintain the humidity moderately high. Conversely, if the flooring was acclimated in winter to dry air, it can begin to swell and ‘cup’ in summer.

This year is very humid in many parts of the northern hemisphere. Flooring installers should be aware of this and take necessary precautions to minimize potential expansion (cupping issues) and contraction (gapping issues).

Measures taken in summer can include but are not limited to:

  • Only acclimating the flooring to a climate-controlled environment and in the same area the floors are to be installed.
  • Installing floors only after all wet work is done (drywalling, painting and so on).
  • Never installing hardwood below grade, unless the flooring was made for below grade installs.
  • Leaving sufficient expansion gaps around each room’s perimeter and any vertical abutments.
  • Ensuring the air handling system is set to an indoor humidity level between 30 per cent and 50 per cent (preferably 40 per cent), which may include keeping the dehumidifier on.
  • Ensuring all substrates and subfloors are dry enough to receive the flooring.
  • Ensuring the moisture content of all flooring planks are within two per cent of each other.

The installer should also make sure all moisture readings are documented. The National Wood Flooring Association recommends measuring 40 boards for the first 1,000 square feet of flooring and taking four readings per 100 square feet thereafter. Similar measurements should be recorded for wood substrates.

If the flooring is installed over concrete, at least one of the following testing methods should be employed.

Surface level testing methods:

Sub-surface level testing methods:

Lee Senter is president of the Canadian Flooring, Cleaning and Restoration Association (CFCRA). The CFCRA offers discounted moisture meters for members and installers to make doing the right thing easier and less expensive. It also provides online and in-person training at little to no cost to help flooring dealers, installers and restoration companies properly take moisture and temperature/humidity readings.

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