Identifying Ideal MC for Hardwood Floors (and Next Steps)

The ideal moisture content (MC) of your hardwood floors will depend on the ambient conditions—or relative humidity and temperature—of the wood flooring installation area.

To determine this amount, you’ll want to find the equilibrium moisture content (EMC) for that location.

EMC is the MC level that a piece of wood reaches when it has finally acclimated to the moisture conditions of its environment. Because wood is a hygroscopic material, it swells and shrinks with the changing moisture content levels in its environment. This means, when it reaches EMC, the wood has finally stabilized to the point where it won’t change or warp anymore.

Hardwood floors are generally expected to have an MC of 6-9%, particularly in homes where the indoor environment is 60-80 degrees Fahrenheit and 30-50% relative humidity.

But if your home’s environment falls outside these specifications, you can base the ideal moisture content on the EMC of your geographic location using this EMC chart.

Because moisture is one of the biggest causes of hardwood floor damage, it’s important to check your floor’s moisture to make sure it’s reached the right moisture content.

That’s why you’ll want to understand:

• Why Moisture Content Matters for Your flooring Project
• How to Test the Moisture Content of Your Flooring
• How to Reach the Ideal Moisture Content
• Where to Find the Moisture Meter You Need

Let’s start from the top!

Why Ideal Moisture Content Matters for Your Hardwood Flooring Project

Moisture content of the wood may seem of little significance to your project. But it can be a huge deal. Having your floorboards at the incorrect moisture level can:

• Damage your project
• Impact your efficiency and productivity
• Cost you more in the long run
• Hurt your reputation

But let’s get to the positive side of things. Here’s how wood with the correct MC can benefit you:

It Will Decrease the Risk of Moisture Problems.

Making sure that your wood has the correct MC before installation can save you from dealing with moisture problems, such as cupping, crowning, buckling, warping, and gaps. Though you can repair or reverse some damage, the wood may never be quite the same. Why not avoid these problems in the first place?

It Will Make You More Efficient and Productive.

When you’re not having to deal with damage to the hardwood floor, you’ll be able to accomplish much more. You won’t have to go back and redo or fix the floor. Instead, you can be confident that the flooring you installed will stand the test of time.

It Will Save Money.

A damaged hardwood floor means more money out of your pocket. Think of the cost of extra wood and labor.

Preventing water damage to hardwood flooring—such as by buying and using a wood moisture meter—might seem like an unnecessary investment, but it’s worth it in the long run.

It Will Bolster Your Reputation.

When you install floors that are high quality, durable, and free from moisture damage or shrinkage gaps, you build trust with your customers. They will appreciate the work you do and sing your praises to others.

So what can you do to achieve that ideal moisture content with every flooring project? You can start by identifying the moisture content of your flooring materials.

How To Test the Moisture Content of Your Flooring

A wood moisture meter will help you measure your wood’s MC, which will help you understand how much it’ll need to change to reach its ideal MC.

Make sure you have the right kind of meter—one for wood. You’ll have two options of wood moisture meters: pin meters and pinless meters.

Pin meters give moisture readings when you insert their pins (or probes) into the wood. An electrical current runs between the two probes, and the moisture level of the wood is determined by the amount of electrical resistance.

But unfortunately, the pin meter will leave holes where the probes were inserted.

A pinless moisture meter, on the other hand, doesn’t have probes and uses an electromagnetic sensor. Thus, it’s the best option for solid wood flooring specialists because it ensures you won’t end up with ugly holes in otherwise beautiful flooring.

When you’re ready to use your meter, enter the correct specific gravity setting for the wood species you’re working with. Then, measure away!

You’ll want to check the wood prior to buying it so you can decide whether it’s worth buying. Is the MC of the wood close enough to the EMC that it will acclimate quickly? If it’s not, you could be looking at an unacceptable amount of time for the acclimation process.

The National Wood Flooring Association (NWFA) recommends measuring 40 boards for the first 1000 square feet of flooring as well as four readings per 100 square feet after that.¹ When you’re done, average the numbers. If the average is far from your target EMC, consider buying wood that has a moisture level closer to the EMC.

Once you’ve purchased the wood and brought it to the job site, check its MC again. This will help you to know how much the wood needs to acclimate.

Also, measure the subfloor moisture. The NWFA recommends measuring in 20 different places for the first 1000 square feet and then taking four readings for every 100 square feet after that. Average the numbers and make sure they’re within about 2% of the EMC.

The MC of the floor and the subfloor (including underlayment) should be close to one another. According to the NWFA, the greatest difference between these two MC levels should be:

• 4% for solid strip flooring (less than 3” wide)
• 2% for wide-width strip flooring (3” or more)

If your subfloor is concrete instead of a wood subfloor, you’ll have to use a special kind of moisture meter designed for concrete slabs or an in situ relative humidity test kit.

Now you know how to measure moisture content in your flooring and surrounding materials, but what do you do if your flooring hasn’t reached the right MC? We’ll explain that next.

How To Achieve Ideal Moisture Levels During Flooring Installation

You recognize the importance of getting your wood to the right moisture level, and know your wood’s current moisture content, but how do you get your current MC to your ideal one?

Here are two simple steps:

1. Prepare the installation environment.
2. Acclimate the wood.

1. Prepare the Installation Environment.

Your installation environment should be dry and at the right temperature and humidity level. Checking these off your list will keep you from sabotaging your project.

Howard Brickman, a wood floor expert in Norwell, Massachusetts, emphasizes the importance of removing any excess moisture at the job site. He advises:

“Make sure that excess moisture—from curing concrete, from less-than-dry framing lumber, or from rain or snow that may have soaked the structure before the roof was on—is removed before the wood flooring is even delivered.”²

In addition, you may need a dehumidifier, humidifier, or air conditioning system to keep the area at a consistent temperature and humidity level.

2. Acclimate the Wood.

Acclimation is the process of conditioning your wood to its environment so that its MC is near the EMC.

Be sure to start with wood that is already close to the EMC, unless you’re in the business of drying the wood yourself. After all, it can take a lot of time to acclimate wood—even 6-9 months! (That’s why we suggest you moisture test the wood with a moisture meter before buying it.)

But if your wood is already close to the ideal MC and just needs to adjust to the installation environment, acclimation may take only a few days. Check with the manufacturer for instructions.

Here’s a basic overview of the process:

1. Make sure the installation site has a stable climate. A hygrometer can be useful for monitoring humidity levels.
2. Remove the floorboards from any boxes or wrapping and stack them with spacers between the boards (per NWFA recommendations).
3. Check progress with a wood moisture meter.

You’ll know that your wood has acclimated once it has reached the ideal MC that you calculated. For more information on this process, check out our article on acclimation best practices.

Where to Find the Moisture Meter You Need

Whether you’re a hardwood flooring specialist or a DIY homeowner, you are reading this article because you care about excellence in your work.

And though some might ignore moisture content in their projects, you’re different. You want to understand the MC of your hardwood flooring so that you can do a job you’ll be proud of.

At Bessemeter, we’re here to support you in accomplishing just that.

That’s why we offer top-of-the-line moisture meters to help you get fast and accurate results for easy-breezy acclimation.

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1. “Acclimation/Conditioning,” National Wood Floor Association Technical Publication, 2019. (↑)
2. Brickman, Howard, “Controlling the Moisture Content of Wood Flooring,” The Journal of Light Construction, jlconline.com, May 1, 2012. (↑)