Hardwood is a classic flooring choice that will most likely never go out of style or demand. But before the consumer can enjoy the end result, installers and contractors must first take the proper steps to ensure the wood—whether engineered or solid—is acclimated to its new environment.

“Wood is hygroscopic, meaning when you add water to wood, it grows, and when you take water out of wood, it shrinks,” explained Jason Canton, an inspector with the National Institute of Certified Floorcovering Inspectors (NICFI).

Wood naturally contains moisture. However, wood flooring installation problems occur when the moisture content of the wood has not equilibrated with the moisture in the environment it is being installed in. Resulting issues can include gaps, shrinkage, warping, cracks, swelling, cupping and crowning.

“Crowning and/or cupping is when the individual planks aren’t flat, but either higher in the middle of the board or on the edges,” stated Jason Spangler, division manager-flooring for Wagner Meters. “Swelling or gapping of the boards in relationship to each other can also be caused by improper levels of moisture.”

According to Paul Laurenzi, Delmhorst’s vice president, sales and marketing, the type of moisture-related issue depends on several factors including where on the floor the moisture is, as well as the source of the moisture.

Always Acclimate 

Once wood planks have been dropped off at the installation site, they should be given time to become acclimated to the new environment before installation begins. This step in the process is crucial to a successful installation—and lasting results.

“The environment where you are trying to acclimate the wood needs to be at whatever temperature and relative humidity it will be at when someone is inhabiting the environment, and this must be maintained during the entire acclimation process.”

Chris Ranwell, global product manager for Protimeter, suggests leaving the wood in the environment it’s going to be installed in for “a period of time.” That period is determined by the humidity and temperature within the space, as well as the moisture content in the wood.

“There’s not a set timeframe,” said Canton. “Generally speaking, [acclimation] happens quickly, but every wood species is different, and every wood species gains and loses moisture at different rates.”

How the wood is stored at the installation site—whether that entails removing the planks from their plastic wrap when they arrive in from the manufacturer, or keeping them racked off the floor—can also determine the rate at which the flooring becomes acclimated to its new environment.

“One thing I find that’s being done wrong with acclimation is installers are bringing the wood into the house and then setting it on the concrete floor,” said Canton. “It needs to be off the floor because the floor has moisture in it. So, those bottom boxes aren’t acclimating as quickly as the top boxes. You need to have something to keep the wood off the floor so it can breathe.”

Canton added, “When installing wood, it’s also key we know the moisture content of the subfloor, so you can correctly adjust what you have to do with the wood.”

Tools of Success 

Upon arrival at the installation site, the level of moisture in the wood planks should be tested to determine if the wood needs to acclimate or if installation can begin right away. Various handheld moisture meters have taken away the guesswork. With the help of either a pin or pinless moisture meter, installers and contractors can determine the amount of moisture in the wood planks prior to installation.

“There are two types of moisture meters,” explained Grete Heimerdinger, vice president of Lignomat. “One, called a pin meter, has pins to insert into the wood. The other, called pinless, lies flat on the wood with a measuring plate on the back.”

She added that when selecting a moisture meter, installers and contractors should assess the environment and job first to make the right choice, or simply use whichever meter they are most familiar with—the most important step is to use a meter at all.

Another good tool to have on hand is a hygrometer, to measure the moisture content in the environment the flooring will be going in. With this tool and the moisture meter, installers can calculate the equilibrium moisture content (EMC) of the wood floor. EMC is the moisture content of wood when it is fully acclimated—not gaining or losing moisture.

“The environment where you are trying to acclimate the wood needs to be at whatever temperature and relative humidity it will be at when someone is inhabiting the environment, and this must be maintained during the entire acclimation process,” stressed Spangler. “You should then calculate the equilibrium moisture content of the environment, utilizing both the measured ambient temperature and relative humidity.”

According to Spangler, Wagner has developed an EMC calculator app, called Wood H20, to help with this calculation. With the environment’s EMC determined, installers will have the target moisture content to use when measuring the wood.

Don’t Cut Corners 

When it comes to installing flooring, it’s no secret that time is money. Because of this, manufacturers are constantly unveiling faster formulas for a quicker, timelier turn-around, and installers have found ways to do their jobs faster—and hopefully better—over the years. However, when it comes to installing wood flooring, testing for moisture and allowing the wood to acclimate are steps that should never be rushed or skipped.

When juggling multiple projects and the demands of the customer, it’s easy to buckle under pressure. But when it comes to mitigating potential failures, contractors can speed up the process and have greater confidence by using instrumentation—not by skipping the process altogether, according to Ranwell.

“The pressure on any floor contractor is to get as many jobs done as quickly as possible,” he said. “It’s a question of how to keep this schedule, while also mitigating potential failures.”