Wood Floor Buckles From Lack of Acclimation

Bob Goldstein Headshot

The Problem

I do many wood floor inspections around Florida,and summer is the time for the usual rash of cupping problems. On the latest call, a contractor said the floor he installed had cupped and even was buckling in some areas.

The Procedure

The contractor installed a prefinished wood floor over an existing wood subfloor on the second floor of a home in Miami. He checked the moisture content of the subfloor, getting a reading of 11 to 14 percent. The flooring's readings were a consistent 8 percent. Since he had never installed this product before, the contractor called the manufacturer to ascertain what the moisture content of this product should be. The technical service person he spoke with told him that the moisture content when shipped usually is at 8 percent, and that it should be fine to begin the installation. Wrong! Shortly after the floor was completed, it began to cup, and within a week, it was buckled off the subfloor in several places. To say the least, the finger-pointing blame game had begun!

The Cause

Let's start with the fact that wood is hygroscopic; that is, it will either give off moisture or absorb it depending on the environment. To explain this, think about ways hardwood, such as oak, was used over the years to construct items like buckets and boats. The wood was soaked in water until it swelled up enough to become watertight. This process "acclimated" the wood to make it a bucket or a boat. If the wood dried out, the bucket wouldn't hold water, or the boat would sink. The same holds true for wine barrels or whiskey barrels. It almost makes one think that flooring is a waste of good hardwood. The key is, don't change the conditions.

Many years ago, when I was a kid in South Florida, (I think it was called the Jurassic Period), I loved to work with my dad during summer breaks from school. Thousands of tract homes had 3/4-by-21/4-inch and 11/2-inch red and white mixed oak flooring. The homes were built on raised footers, using a joist system with airflow under the house. The floors were hand-nailed over a 1-by-6-inch pine subfloor nailed to the joist on the diagonal. The wood flooring was delivered and left outside, usually in the carport. Homes in Florida were built to take advantage of the sea breezes using jalousie windows and ceiling fans, so the wood floors were acclimated for the high humidity in this area.

When the price of air conditioning became more affordable in the late 1960s and 1970s, the calls came in hot and heavy. "My wood floors are full of cracks." The air conditioning was removing moisture fromthe homes, and as the wood dried, it shrank. This floor I was inspecting now had the opposite problem—the floor swelled from the job-site moisture.

How to Fix the Floor

Since the customer doesn't want the floor fixed by sanding it, the contractor is stuck with having to replace it.

In the Future

The wood floor contractor's mantra is "acclimate the flooring to the conditions in which it is going to be used." This sounds simple, but in reality, it is like playing a game in which the rules keep changing during the game. As a professional contractor, you predict as best you can what the rules will be. Take into account your geographical area, and refer to NWFA's Water and Wood technical manual. Use a moisture meter to make sure the floor is within the suggested parameters. Talk to the end user—do they use the HVAC all year? Do they use a dehumidifier or humidifier? Do they shut the building down for long periods of time during the year?

With some flooring, to unwrap or not to unwrap—that is the question. Most floating floors must be left in the plastic-wrapped factory carton before they are installed. If the cartons are opened and the flooring exposed to the moisture in the environment, you may not be able to fit the tongues into the grooves. On the other hand, many imported solid products also are coming wrapped tight in plastic. Solid products always should be unwrapped and allowed to acclimate to the job site. Some of my recent inspections also would suggest that bamboo floors should be unwrapped and allowed to acclimate, as well.

Easy Formula for Acclimation:

1. Remove wood from plastic packaging, if applicable.

2. Use your moisture meter and hygrometer to check and monitor moisture.

3. Err on the side of the wood shrinking. Filling is afar better thing than refinishing.

Finally, if you are calling a manufacturer for information, be specific as to where the floor will be installed on the job site, as well as its geographic location. Let them know the particulars of the installation. The more information you give, the better answers you will get.

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