Log in to view the full article
The Problem
A contractor complained that the wood flooring he was installing was mis-milled.
What Happened
The contractor in upstate New York had begun an installation of solid ¾-by-3 1⁄4-inch ash flooring in August. He stopped his installation because he discovered the ends of several boards were wider than the rest of the board.
The Inspection
I asked: How long had the flooring been on the job site? One week. What were the RH and subfloor MC when the wood was delivered? What were the RH and subfloor MC when the installation began? He didn’t have answers.
At the mill, the flooring has extremely tight tolerances for milling and moisture control, so I was confident the wood wasn’t milled incorrectly. I asked the contractor to measure for width variations along the length of the problem boards. I also asked that he obtain accurate MC measurements of the board along its entire length. Here is what was discovered:
• The subfloor had a MC between 9–11%, typical for the area—likely not the culprit.
• The RH in the house was around 74%. This was too high for installation and too high for acclimation.
• The boards that had measurable width variation up to 1⁄32 inch also had MC readings 2–4% higher in the wide areas than in the areas measuring the correct width, which had a MC of 6–10%.
We realized the contractor had opened or removed the box ends when the wood was delivered, allowing the flooring closest to the ends of the boxes to absorb more moisture and swell. We confirmed this by pulling pieces out of the boxes; they measured wider on the ends by the open end of the box.
RELATED: Understanding How to Measure Moisture Can Avert Job-Site Disasters
How to Fix the Floor
I recommended they stabilize the job site environment and monitor the wood until it was back to the proper MC and the width variations were reduced or eliminated (unfortunately, wood flooring takes much longer to lose moisture than to gain it).
In the Future
Our antiquated ideas about acclimation go back to when the MC of flooring had a lot of variation and homes had only basic forms of heating, with no cooling. We rush to put well-made, moisture-controlled flooring into spaces where the environment is nowhere close to a “lived-in” condition. If conditions are in the right range of temperature and RH, there is very little reason to put the flooring on the job site to “acclimate” prior to install. If the job-site conditions are out of the acceptable range, you will be acclimating good wood to your bad environment!