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If you haven’t faced it already, chances are you will.

Moisture is one of the biggest sources of problems for hardwood flooring installers. And the experts agree.

Brian Beakler, manager for Armstrong Floor Products, hasn’t forgotten the words of an old professor who told him, “95 percent of all problems that you will experience in wood in your career will be moisture-related in one way or another.”1

“Thus far, he is correct,” Beakler confirms.

Much of preventing these problems comes down to something very simple: testing wood moisture content. We’re here to guide you in that process by looking at nine mistakes to avoid:

  1. Not testing at all
  2. Not knowing the floor’s safe moisture level
  3. Measuring in an uncontrolled environment
  4. Using a wrong (or ineffective) tool
  5. Not checking the meter’s calibration
  6. Not accounting for wood species or temperature
  7. Reading at the wrong depth
  8. Testing in only one location
  9. Not documenting your work

Following these nine guidelines will give you the best grasp of the floor’s moisture condition so you can best prepare for a successful installation. You’ll avoid major moisture problems, such as cupping, buckling, and warping.

Let’s get into the details.

1. Not Testing at All

This one almost goes without saying, but we’re going to say it anyway. Testing wood moisture content with a moisture meter is the only way to know whether your floorboards are ready for installation.

Here’s why:

Wood always adjusts to the moisture content of its environment. And if its moisture content doesn’t match that of the environment already, it’ll shift to get there. That means it’ll either release moisture or absorb it, causing it to either shrink or swell, respectively.

The flooring will warp, cup, crown, or crack if any of this moisture-related wood movement is significant enough (often even just a few percentage points of change).

For this reason, it’s especially important to test the moisture content of your wood floorboards (1) when they arrive at the jobsite and (2) right before installation.

If the moisture content is too high or too low, allow the boards time to acclimate to the right number, remove the wetter boards from the ones you use, or send the entire batch back and get a batch that has the moisture content that you need.

2. Not Knowing the Safe Moisture Level for Your Hardwood Floor

If you don’t know the safe moisture level for your hardwood floor, you won’t know what to look for when you measure the moisture content.

The safe moisture level is the equilibrium moisture content (EMC) for the floor’s final destination. This number is the moisture content the wood will naturally shift to at a given temperature and relative humidity.

The National Wood Flooring Association (NWFA) provides a chart of the United States that shows the EMC by region. The typical EMC for moderate climates is about 8%, though it can range from 6-10%. Drier areas will be closer to 6%, while damp, coastal areas will be closer to 10%.2

Something else to keep in mind is the seasons. Since humidity can shift depending on the time of year, make sure you’re taking into account the EMC of both winter and summer in a specific area.

Otherwise, you and your customers could end up with a costly problem—like one family who had a solid maple floor installed at too low of a moisture content in the winter. They lived in Maryland, and as soon as humidity hit in the spring, the floor began to show the effects by cracking and squeaking.3

“The two experts told us the only real solution was to rip out and replace,” they shared on HardwoodFlooringTalk. And that was going to cost $20,000+!4

Save yourself and your customers that kind of hassle by knowing the EMC for the floor’s final destination, as well as what to consider for the time of year. Then make sure the moisture levels coincide with the numbers from the official guidelines.5

An EMC chart can help you do this—and some wood moisture meters even have a built-in EMC calculator.

3. Measuring in an Uncontrolled Environment

The NWFA recommends that when wood floorboards arrive at a jobsite, the site should already be at the temperature and humidity required by the manufacturer.6

That way, the floorboards will quickly acclimate to the indoor environment rather than fluctuating with the changes outdoors.

Typically, the safest condition for most wood is a consistent level somewhere between 60 and 80° F and 30 and 50% relative humidity.

4. Using a Wrong (or Ineffective) Tool

When measuring wood moisture content, check that you have a moisture meter specifically for wood, rather than for concrete or other materials. You have two options for wood moisture meters: a pin meter or a pinless meter.

Pin meters measure the moisture content of wood through two small probes (or pins) that have to be pushed into the wood. An electrical current flows between these two pins, measuring the resistance and, thus, the amount of moisture in the wood.

Pinless meters, on the other hand, use an electromagnetic field to scan the wood and measure its moisture content.

So, which is the best option for hardwood floor installers?

We recommend a pinless meter, simply because you wouldn’t want to put pinholes into your customer’s beautiful new floor. What’s more, with a meter that takes seconds to scan for moisture, you’ll be able to test many boards in no time.

Regardless of which meter you choose, though, avoid using a cheap meter. Cheaply priced meters are often cheaply made and poorly designed. They also lack the accuracy of better quality ones and can be as much as 5 to 20 percentage points off from the actual moisture content! Based on what we learned about EMC, that could mean a ruined floor.

5. Not Checking the Meter’s Calibration

According to the NWFA, “calibration ensures the meter is giving accurate readings.”7

High-quality meters often come with a calibration block that allows you to verify it yourself.

If the meter is out of calibration, you may need to contact the manufacturer and send it back for calibration.

Otherwise, you risk getting inaccurate results that’ll hurt your projects in the long run.

6. Not Accounting for Wood Species or Temperature

Two factors that can affect the accuracy of wood moisture meter readings are wood species and temperature. Different wood species have different densities and chemical compositions that can skew results if not accounted for.

In general, pinless meters are more affected by the density of the wood, while pin meters are affected by the chemical composition.

That’s why a quality moisture meter is going to come with a feature that allows you to set the species before measuring.

Pin meters are usually the meters affected by temperature. If the ambient temperature is much different than room temperature, use a correction chart to adjust your results. This kind of chart will typically come with the meter.

If not, the NWFA provides a temperature correction chart in its Wood Flooring Installation Guidelines booklet (see page 40).

7. Reading at the Wrong Depth

The depth at which you’re measuring should be appropriate to the thickness of the floorboards. The standard depths for pinless meters are ¼ or ¾ of an inch—and some have a setting for both.

If your planks are only ¼-inch thick, using the ¾-inch setting could cause you to test whatever’s under the board rather than the board itself. You don’t want to skew your reading that way.

With a pin meter, use pins that are an appropriate length for your floorboards. If you’re using insulated pins, the meter will measure from wherever the tips reach.

8. Testing in Only One Location

Testing in only one location won’t give you an accurate understanding of all the floorboards for the installation. There could be variations in moisture content in one batch of wood, and some boards may have too much excess moisture to be ready for installation.

To make sure you’re safe to install, you should know the NWFA guideline of measuring 40 boards for every 1,000 square feet of flooring and 4 additional boards for every 100 square feet after that.8 Some installers choose to take a quick reading of every single board, just to make sure they don’t have individual outliers that are going to cause them problems.

Ultimately, it’s a business decision you’re going to have to make for your specific risk profile and situation. Think about the value of the floor and of your time, especially considering taking enough readings versus dealing with a potential call-back.

If you have a wood subfloor, it’ll need testing, too. Test 20 locations for every 1,000 square feet and 4 additional locations for every 100 square feet after that. The moisture content of the subfloor should be within 2–4% of the flooring.9

If the subfloor is concrete, it’ll require a different test altogether. We recommend a relative humidity test, which will give you the most comprehensive picture of the slab’s moisture condition.

9. Not Documenting Your Work

Keep track of the moisture measurements you take to protect your work down the road. This will help prevent issues with liability if something does go wrong with the floor. You’ll be able to show your customers the moisture content at the time of installation, so they will be less likely to throw any blame in your direction if an issue comes up afterward.

“I could not be more thankful that I always use a moisture meter for every wood order,” says Leonard Hall, a flooring contractor in Florida.10

He had installed a Douglas 18” plank floor for a customer. But when warping occurred later, the general contractor accused him of improperly installing the floor. Fortunately, because he had been using a moisture meter, Hall knew that the floorboards had been at 10%, the EMC for the area.11

This precaution helped protect his reputation from being damaged by a problem he hadn’t caused.

Taking records doesn’t have to be complicated. Some high-end pinless meters connect with smartphone apps, allowing you to save records as you scan the wood. Reports can even be created for you.

What Success Looks Like with a Reliable Wood Moisture Meter

Proper wood moisture testing sets you up to:

  • Preserve the hard work you put into a floor
  • Save the cost and time of repairing floor damage
  • Build your reputation with your customers
  • Protect yourself against problems you didn’t cause

Imagine the peace of mind you can have with each job just by knowing that you’re working with the right tools and the right information.

Get your hands on a high-quality wood moisture meter and see for yourself the difference it’ll make.

For more guidance as you shop, try this moisture meter buying guide.

  1. Beakler, Brian, “Understand Wood Floor Moisture Content & Dimensional Change,” Wood Floor Business.
  2. Wood Flooring Installation Guidelines, National Wood Flooring Association, 2019, p. 33.
  3. “Repair for squeaking?!” HardwoodFlooringTalk.
  4. Ibid.
  5. Wood Flooring Installation Guidelines, p. 34.
  6. Ibid.
  7. Ibid., p. 40.
  8. Ibid., p. 34.
  9. Ibid.
  10. Hall, Leonard, “The Cupping 18-Inch Plank (or ‘Why I Always Use a Moisture Meter’),” Wood Floor Business.
  11. Ibid.