Laminate

Acclimating Wood Flooring and Checking Subfloor Moisture

NWFA-based guidance on conditioning the jobsite, how many moisture readings to take, and the allowed difference between flooring and subfloor.

Updated · 2 min read

Wood moves with moisture. Acclimation isn't a set number of days in the room; it's getting the flooring and the subfloor to the moisture levels they'll live at, and measuring to prove it. The guidance below follows the National Wood Flooring Association's installation guidelines.[1]

Condition the jobsite first

Get the building to living conditions first, or the wood adjusts to the wrong ones.

  • HVAC should run for at least 5 days before the flooring is delivered.[1]
  • The general target for solid wood is 30 to 50% relative humidity and 60 to 80°F, with regional exceptions.[1]
  • There's no fixed number of days. If the flooring arrives at a moisture content that already matches the expected conditions and the subfloor, it can go in right away.[1] Otherwise, follow the flooring maker's instructions and your meter readings.

Take readings

Your readings are the proof the floor went in under the right conditions.

  1. Check the flooring's moisture on delivery to establish a baseline.
  2. Take subfloor readings: at least 20 in the first 1,000 sq ft, plus 4 per 100 sq ft after that, then average and record the results.[1]
  3. In most regions, a dry wood subfloor reads 12% moisture content or less.[2]
  4. Re-check the flooring after acclimation and compare it to the subfloor.
  5. Write down the readings, locations, dates and room conditions.

Allowed difference

The allowed difference depends on board width.[1]

Flooring width Wood subfloor moisture content can be
Under 3" (strip) No more than 4% greater than the flooring
3" and wider (plank) No more than 2% greater than the flooring

Over concrete

Concrete gets its own tests. Moisture testing on a new slab can start 30 days after it's poured, but that doesn't mean the slab is ready for flooring.[1] Use the tests your flooring and adhesive makers specify; see Subfloor moisture testing.

Common mistakes

Most acclimation problems come from measuring too little or too early.

  • Stacking boxes in a room without HVAC running.
  • Counting days instead of taking readings.
  • Taking three readings in one room and calling it done. The minimum count is per 1,000 sq ft.[1]
  • Using the 4% rule on wide plank. Wide boards get 2%.

Meters we carry

These meters read wood, and several read concrete as well.

References

  1. NWFA: Wood Flooring Installation Guidelines
  2. Shaw: Engineered hardwood installation guidelines

Linked PDF documents are archived copies saved by PreFloor Tools so they stay available if the publisher moves or removes them. Check the publisher's website for the latest revision.

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