How To: Flooring Acclimation

06 Sep How To: Flooring Acclimation

The facts about flooring acclimation might just save your investment.

A client of ours who just invested substantially (think about the ballpark price for a brand new Corvette) into their floor renovation project recently asked, “I don’t really need to worry about this whole moisture thing do I?”

Yes, you do. It’s like buying a new Corvette, driving it all winter and expecting it to maintain its original performance.  Not a chance.

corvetteImagine explaining this to your wife over dinner

Regardless of whether you’ve hired a professional or attempted a DIY, there is one critical aspect that you must take into account in order to maintain your wood flooring installation: control of the moisture content (MC).

But what’s the worst that could happen, right?

Controlling moisture content is the most critical aspect to properly installing (by the pro’s) and maintaining (by you) any wood-based product because wood is “hygroscopic.” That’s just a fancy way of saying “water loving,” and hygroscopic materials gain and lose moisture depending on the environment (hello Canada and our four lovely seasons).

When wood gains or loses moisture, it changes dimension. Dimensional change in solid hardwood and (to a lesser extent) engineered wood flooring can wreak havoc and, depending on the amount of dimensional change, possible defects such as buckling, gapping, checking, splitting, cupping and crowning. It is important to understand a bit about the manufacturing process and how the ambient atmospheric conditions can affect your wood flooring’s performance.

  bucklingAn example of a buckling floor from moisture damage

Let’s break it all down here.


For example, most manufacturers produce solid and engineered wood flooring products going into the box with an MC (remember, that means ‘Moisture Content’) of 6–9%. MC is defined as ‘the weight of the water contained in the wood, expressed as a percentage of the weight of the dry wood’. Wood products produced for residential use here in Canada are generally manufactured to hold the 5–9% MC range.

Generally speaking, those interior environments (your home) hold approximately that same atmospheric MC, also known as equilibrium moisture content (EMC), year-round. EMC is defined as the MC at which wood neither gains nor loses moisture when surrounded by air at a given relative humidity and temperature (in other words, the perfect balance for the perfect floors). In essence, when wood at a specific MC is placed into an environment that does not match its MC, the wood will gain or lose moisture until equilibrium with the environment is met. The result of this gain or loss in MC is dimensional change (remember above when we mentioned gaps, splitting etc?  Ya, not a welcomed feature after all that money you’ve invested in to your floors).

Most manufacturers require that wood flooring products be “acclimated” to the environment (your home) in which they are going to be installed. Improper acclimation typically results in gapping between boards (in drier conditions) and buckling or crushing (in wetter conditions). For example, if an installer fastens 3⁄4-inch-thick, 31⁄4-inch-wide Northern red oak (predominantly flatsawn) flooring with an average out-of-the-box MC of 6% in an interior atmosphere that has an 11% EMC without proper acclimation, he or she can expect approximately 4.4 inches of expansion in an installation 20 feet in width.

acclimated vs not

Not a pretty picture.

No matter where you are or which product you’re installing, controlling moisture on every job site is critical to avoiding those 95 percent of wood floor problems.

So, the point of this article is to inform and educate you on not only the risks of moisture to your wood floors – but also to the solutions!

We’re going to provide you with easy steps you can implement to acclimate your home, so you can maintain your investment and enjoy those wood floors for years to come.

Here’s how you do it:

In winter time

In the winter time when homes are heated and the air is dry, wood flooring gives up some of its moisture and contracts as a result. When this happens, thin gaps can appear between planks. This is normal, and a homeowner should be prepared for it to occur. Once indoor heating is turned off in the spring and humidity levels rise again, most of the gaps will close up.

To avoid these separations, try to control and monitor air humidity levels during the dry season by installing a humidifier in the furnace or bringing a movable humidifier into the room that has good air circulation. Optimal humidity level falls in 45-60% range. As long as humidity does not fall lower than 45%, no gaps at all will appear between the planks. Installing a simple humidity meter will allow you to monitor and control humidity levels in your home all year round.

In summer time

During warm and humid summers when indoor humidity can rise up to 90%, the opposite occurs. Wood absorbs moisture from the air and expands as a result. Even just a few days of exposure to high humidity can cause wood flooring to cup. When a wooden board cups, its edges are higher than its center. Cupping can also happen when spilled water is absorbed by the wood. Once cupping has occurred, it takes a while for the wood to restore its internal moisture and flatten out.

When extensive moisture or humidity causes the wood to expand significantly, adjoining boards start pressing against each other. In extreme cases, this increased pressure can cause the affected boards to lose their structural integrity and crack. To avoid cupping, keep indoor humidity level in your home or job site (prior to hardwood installation) within 45-60% range. Never allow indoor humidity to rise over 65%. Maintain optimal humidity levels by keeping air conditioner or dehumidifier running during hot humid summer weather.

There you have it, easy solutions to an otherwise painful problem.

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