How to Measure Moisture in Hardwood Floors

Moisture, whether a persistent leak or sudden flooding, is never good news for a hardwood floor.

But there’s a more subtle danger—moisture in the wood itself. Because wood naturally absorbs and releases moisture depending on ambient conditions, floorboards need to be at the moisture content that matches the environment (known as the equilibrium moisture content, or EMC).

How do we know it has reached that number?

That’s where moisture measurement comes in.

Using a wood moisture meter is the simplest way to measure moisture, and the following sections will give you everything you need to know to get accurate readings. We’ll cover:

• Acceptable moisture readings in hardwood floors
• How to check for moisture in flooring
• Mistakes to avoid when measuring moisture

What is an acceptable moisture reading in hardwood floors?

Wood flooring installers typically want the moisture content of hardwood floorboards to be between 6% and 9%. That range is based on an indoor temperature of 60–80° F and 30–50% relative humidity.

But to know the exact number required for your flooring, you’ll need to determine the EMC of your area.

EMC is the moisture that a piece of wood will naturally reach when it remains in an environment with a consistent temperature and relative humidity. It is your baseline for acclimation.

The National Wood Flooring Association (NWFA) provides a simple chart for determining the EMC of your location based on temperature and relative humidity. You’ll want the moisture content of your hardwood floorboards to match or nearly match the EMC of your area. In addition, the NWFA recommends that it be within 2–4% of the moisture content of the subfloor:

• No more than 4% for solid-strip flooring (less than 3” wide)
• No more than 2% for wide-width strip flooring (3” or more)

Now that you know what numbers to look for, here’s how to measure moisture.

How to check for moisture in flooring

All you need for checking moisture in flooring is a good moisture meter. You’ll need one for wood. And possibly one for concrete, if you have a concrete subfloor to check also.

Scientists use the oven-dry testing method to determine the moisture content of wood. But this process is time-consuming and requires specialized equipment.

Moisture meters provide accurate measurements much more quickly and efficiently. They’re used by most professional flooring installers.

Wood

For wood flooring, you have two options: a pinless moisture meter or a pin-type moisture meter.

For either one, first, input the correct species into your meter.

With a pin meter, insert the pins into the surface of the wood you want to test. Be sure that you align the pins with the grain rather than across it. Then, turn on the meter to get your reading.

The downside of using a pin meter is that it’ll leave small pinholes behind—not ideal for keeping your hardwood floor pristine!

That’s why we recommend a pinless meter instead.

To use a pinless meter, all you have to do is firmly place the meter on the part of the floorboard you want to scan. You’ll have a reading within seconds—and without any pinholes left behind.

If you’d like to learn more, read our article discussing pin and pinless meters.

Concrete

Concrete moisture meters are helpful for indicating where areas of higher moisture are. They can give a comparison of the wetness of different areas.

For an accurate assessment of the concrete’s overall moisture condition, you’ll need more specific tests, such as the in-situ relative humidity test (ASTM F2170). But for the purpose of this article, we’re only covering moisture meters.

Get more details about concrete moisture meters.

Mistakes to avoid when measuring moisture

To set you up for success in measuring the moisture of wood, we’ve compiled some of the mistakes to avoid:

Not using a moisture meter

We know it sounds obvious, but not using a moisture meter is one of the biggest mistakes you can make.

It’s not enough to eyeball your wood or feel how heavy it is because the moisture in the wood won’t always be detectable by sight or touch. That’s why you need a moisture meter for the job.

Using the wrong moisture meter

Moisture meters are designed and calibrated for specific materials. Wood moisture meters for wood, and concrete moisture meters for concrete.

Check that you’re using the right one for your project.

Some companies advertise moisture meters that are “multi-purpose,” but we recommend being weary of such claims. These meters may lack the accuracy you need for a damage-free project.

Only taking a couple of moisture readings

If you have a large load of floorboards, a couple of readings cannot be expected to give you an accurate picture.

The NWFA recommends measuring about 40 boards for the first 1,000 square feet of flooring. Then, take four readings for every 100 square feet after that.

And even on the same floorboard, moisture can vary depending on the part of the board. Make sure you get readings from the center of the board where the wood holds the most moisture.

Failing to adjust for species or temperature

As we mentioned above, quality moisture meters will come with species charts that have numbers for each species. Be sure to input that number into your meter.

The reason?

Different species of wood have different characteristics that can skew the reading you get. By inputting the species number into your meter, the meter will adjust the readings for that particular species.

Pin meters are also sensitive to temperature (anything that isn’t around room temperature), so you’ll want to consider that in your measurement. The meter should come with a temperature correction chart for manually making the adjustment.

Not understanding what the moisture content needs to be

If you don’t know what you’re aiming for, measuring the moisture content of your wood won’t be helpful.

Determine the EMC for your wood in the area that you’re in. Then, use that number as the goal for your measurements. You may need to acclimate your floorboards before installation to reach the EMC and prevent damage.

A simple step for successful hardwood floor installation

Using a moisture meter is a quick and accurate way to determine the moisture content of your hardwood flooring.

With a pinless wood moisture meter, you can quickly and easily take multiple readings without damaging the wood. In the process, be sure to keep detailed records of the data.

This way, you’ll ensure that your wood has reached the necessary moisture content. And you’ll be confident that your floor installation will be successful.

The result?

A hardwood floor that lasts for years to come.

Head on over to our moisture meter buying guide for help choosing the right meter for you.