As an NWFA Certified Wood Flooring Inspector, I get plenty of calls regarding acclimation. Many times, I will hear things from the consumer such as: “My installer brought in the wood flooring and started installing it right away; I checked and found out that’s not how it’s supposed to be done,” or “my wood floors are cupping, gapping, buckling, splitting, (you can add in the issue); I think they didn’t acclimate the wood flooring properly,” or “the wood flooring contractor has told me that this is normal, and these issues will take care of themselves in the next (either heating or cooling) season.” This is where the journey starts for most inspectors.
Most consumers are too sophisticated for that kind of talk these days. With the internet and all it has to offer, consumers are a click away from finding the needed answers to whatever problem their wood floors are showing.
Here in the Dallas area, I see a fair amount of acclimation issues with wood floors installed on both pier and beam foundations with a crawlspace, and with plywood attached to the concrete slab.
On a recent inspection, acclimation, or the lack thereof, was one of the underlying causes for the cupping and gapping in the consumer’s new wood floors. The call from the homeowner stated they had a water leak, and the wood floors were replaced, but now the new wood floors looked worse than what was removed.”
I like to start with getting a good timeline of the events: when the leak happened, moisture mitigation, removal, installation, etc.
I was a little shocked to find out that the leak happened in February 2021, moisture mitigation started the next day and took place for several days, then the removal of the water-damaged flooring didn’t happen until October 2021 (eight months later). The delay was that the leak happened days before the big Texas freeze that year. After that, you couldn’t find a contractor who wasn’t already booked out for months, as they were all dealing with homes flooded from the freeze.
The insurance company finally got back around to this job and got a contractor moving forward on the project. The HVAC system was in working order, and the homeowners had been living in the home.
They delivered the new ¾” x 2 ¼” red oak wood flooring into the home and stacked it on top of that existing water-damaged wood flooring. Upon delivery, there were no temperature or humidity tests done to see if the environment was correct. There were no moisture tests of the original wood flooring done to see if there was any lingering moisture from the leak.
The replacement wood flooring sat in the home for seven days, then the removal of the existing wood flooring started. They removed all of the wood flooring except where the wood was staged, which was removed later.
They started the wood flooring installation with no moisture testing of the subflooring or of the new wood flooring. There was no check of the crawlspace or the foundation vents.
Unfortunately, I see this quite a bit, and the thinking is that the old flooring did fine so the new flooring should be fine. Nothing can be further from the truth, without proper moisture testing to know what you’re dealing with.
The wood flooring began to gap in February 2022, as the winter was fairly cold. The homeowner reported the gapping to the contractor at the beginning of March 2022. They held a meeting in mid-April with the general contractor and the wood flooring contractor. The wood flooring contractor informed them that “it’s been cold this winter and the gaps are seasonal, and related to low relative humidity in the home; not to worry, they will go away early in the summer.” In mid-May, the entire wood floor cupped, and the gaps still were there.
As the outside humidity levels rise, so do the moisture levels in the crawlspace, and the pine board subfloor. At my inspection, the wood flooring moisture content averaged nine percent with my scan meter. I checked the moisture content of the pine board subfloor using my hammer probe with insulated pins, which averaged 15 percent. Then I went into the crawlspace to confirm my subfloor readings from below, and using my Lignomat scan meter, set at a 3/4” depth, my readings averaged 15.3 percent. The difference between the wood flooring and the subfloor is six percent.
The home originally was built in the 1950s and the crawlspace met the code back then, but when you install new wood floors, there needs to be a reevaluation of the crawlspace and proper moisture reading before moving forward. Unfortunately, that did not happen. The venting was about one-third less than today’s minimum code requirements. The general contractor could have added 6-mil plastic over the dirt, which could have brought it into compliance, but no one really looked into what needed to be done.
Acclimation is more than letting the wood flooring sit in the home for a few days and thinking you’re good to go. I also see a lot of companies bring the wood flooring in to an unfavorable jobsite (generally without HVAC in operation), and nail it down right away, and then let it sit for weeks or months before finishing it, but that is not proper acclimation.
Today’s proper acclimation recommendations are about conducting the proper jobsite review before delivery of the wood flooring. Make sure that the jobsite meets the manufacturer and NWFA requirements. This includes temperature and humidity testing for each room, and moisture testing of the subfloor to make sure there are no moisture issues. Your moisture meter and the proper number of tests will let you know when the home is ready to receive the wood floor. Depending on the materials you are installing, the difference between the subfloor and the new wood floor should be no more than a four percent MC for strip flooring, a two percent MC for plank flooring. Lastly, to protect yourself, document and take pictures of your readings, because if something goes wrong, it’s the first thing inspectors want to know.
Timothy McCool has 44 years of experience in the flooring industry, and is an NWFA Certified Wood Flooring Inspector. Located in Texas, McCool currently is a sales representative for MAPEI. He can be reached at email@example.com.