What’s the Ideal Moisture Content for Hardwood Floors?
Getting ready for a wood floor installation and wanting to make sure the project is a success?
Then, you’ll need to know your flooring material’s moisture content and ensure it has reached its ideal level.
Why? Turns out, moisture is one of the biggest causes of damage to wood floors, so understanding moisture content will prevent mishaps during and after installation.
Read along in this article to learn more about how you can have a damage-free project. We’ll look at:
- What’s the ideal moisture content for your hardwood flooring project?
- Why moisture content matters for your project
- How to achieve that moisture content level
What’s the ideal moisture content for your hardwood flooring project?
The ideal moisture content (MC) for hardwood flooring is about 6–9% when the indoor environment is 60–80 degrees Fahrenheit and 30–50% relative humidity. The ideal MC will depend on the ambient conditions at the location of installation.
To begin, you’ll want to figure out the equilibrium moisture content (EMC) for that area.
What is EMC?
Wood expands or shrinks with changing moisture levels in its environment. EMC is the MC level that a piece of wood eventually reaches in a specific environment when conditions remain stable.
Two conditions determine EMC:
- Relative humidity—the ratio of the amount of water vapor in the air to the amount of water vapor the air can hold
- Temperature—the temperature of the air affects how much water vapor it can hold. Warm air can hold more water than cool air.
To figure out the EMC for your region, you can use an EMC chart like the one provided by the USDA Forest Service.
The optimal moisture level for your wood will be the average of the high season EMC and the low season EMC.
Why ideal moisture content matters for your hardwood flooring project
Moisture content 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
- 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, 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 re-do 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 extra labor.
Preventing moisture 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, 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? We’ll answer that next.
How to achieve the ideal moisture content
You recognize that MC is important, and maybe you’ve looked at that EMC chart and figured out your wood’s ideal moisture level. Now, how do you get your wood to that point? Here are some simple steps:
- Measure the wood with a moisture meter before purchase.
- Measure again before installation.
- Prepare the installation environment.
- Acclimate the wood.
1. Measure the wood with a moisture meter before purchase.
A wood moisture meter will be your best friend. It’ll help you know the wood’s MC and 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 meter, on the other hand, doesn’t have probes and uses an electromagnetic sensor. Thus, it’s the best option for hardwood 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 different from the EMC you determined, consider buying wood that has a moisture level closer to the EMC.
2. 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 or air conditioning system to keep the area at a consistent temperature and humidity level.
3. Measure again before installation.
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 MC. 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 that of the subfloor (also known as 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 rather than wood, you’ll have to use a special kind of moisture meter designed for concrete or an in situ relative humidity test kit.
4. 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 measure 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:
- Make sure the installation site has a stable climate. A hygrometer can be useful for monitoring humidity levels.
- Remove the floorboards from any boxes or wrapping and stack them with spacers between the boards (per NWFA recommendations).
- 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.
Put in a hardwood floor you’ll be proud of.
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. Reach out to us with any questions, or check out our store for your moisture meter needs.
Here’s to beautiful, damage-free hardwood floors!