How Long Does it Take to Acclimate Hardwood Flooring?
Many contractors think that if you bring wood flooring into the installation site and let it sit for a few days, it will acclimate. This is a big mistake that costs flooring contractors time and money.
What Is Wood Floor Acclimation?
Wood floor acclimation is “the process of adjusting (conditioning) the moisture content of wood flooring to the environment in which it is expected to perform”. (According to the National Wood Flooring Association (NWFA))
Acclimation has less to do with the amount of time you should let flooring sit to acclimate on the job site. It has more to do with monitoring the moisture content of various components.
A controlled environment that remains within a relative humidity range of 30-50% is key for peak performance. The temperature should also remain within a range of 60-80 degrees Fahrenheit.
Job Site Preparation before Wood Flooring Acclimation
Wood flooring installation should always be the last job of any construction project, and the job site must meet certain conditions before wood flooring is delivered to the job site.
Make sure the job site is ready for the wood, and the wood is ready for the job site. Wet elements including plaster and paint should be completed and dry before the wood is delivered.
We asked Levon Karapetyan from Northern California’s prestigious Artex Flooring Inc. how he prepared a job site for the delivery of wood flooring.
He said, “Before we receive a shipment of wood flooring, we monitor the job site to make sure the relative humidity is in compliance with recommended standards, which is 35-60%. We also make sure the doors, windows, and HVAC are installed and functioning. We check the perimeter of the house for any suspicious areas that need to be brought to the contractor’s attention.”
Communication at this point between the flooring contractor and the general contractor is essential. Don’t buckle under pressure from the contractor or homeowner if the above conditions have not been met. They may say, “Don’t worry about it…put the floor in now…we’re running behind schedule.”
Clients may not care now. But, they will care 6 months or a year down the road when the floors buckle, split, or crown.
Levon believes it’s important to educate your clients with useful information.
“It’s always good practice to keep your clients informed, even though they are very educated. You need to give them as much information as possible to ensure the success of their wood flooring.”
Here’s how Levon deals with builders or clients who insist on installation even if conditions aren’t suitable: “If the moisture content is high in the concrete or on the job site, we tell the contractor we have to follow certain steps to bring relative moisture and humidity down with dehumidification or HVAC. Then we’ll come back and check again to make sure the moisture content is in regulation according to suitable moisture content standards. If it is, we will then bring in the wood flooring.”
What about humidity problems with new construction settings? Levon explained, “We always make sure the wet trades are completed before we bring the flooring in. We won’t deliver the material while they are still working. After we have taken all precautions and know the job site is ready, we will bring the wood flooring in and let it sit for 1 to 2 weeks depending on the situation. Then we will proceed with our installation.”
As Levon cautioned, it’s always better to delay bringing in wood flooring materials if the walls were painted or the subfloor isn’t completely dry. Wood flooring is hygroscopic, meaning it will absorb moisture and change dimensions. Wood will expand when it retains moisture and become smaller when it loses moisture, according to the NWFA.
If acclimated wood flooring is delivered to a job site before the paint is dry, the wood flooring will absorb the paint’s moisture, thus increasing the moisture content of the wood.
Wood Flooring Moisture Measurement Guidelines
Acclimated solid strip wood flooring (less than 76 mm wide) will not have more than a 4% moisture content difference between the flooring and the subfloor. For wider flooring (more than 76 mm wide) there should never be more than a 2% moisture content difference. Wider boards tend to have more movement issues than narrow boards.
The conditions listed below may vary because of geographical location and wood species:
If the subfloor moisture measurement comes in at 7-10% (measuring with a calibrated wood moisture meter) and your hardwood measures 7-10%, it’s usually safe to assume the job site is ready for the wood, and the wood is ready for the job site.
If the job site is normalized to an in-use reading for your region, and the subfloor and the wood flooring moisture content (for wood flooring less than 76 mm wide) are within 4% of each other, then the flooring is acclimated and ready for installation.
The following conditions should always be established before wood flooring is delivered:
- The building is completely enclosed (doors and windows installed)
- Final grading has been completed and all drainage runs away from the building
- All wet construction elements are completed and dry (concrete, plastering, drywall)
- Basement and crawl space areas are dry
- AC and or heating is functional and has been running for 5 days before installation
- Appropriate humidity and temperature inside the building has been achieved
Once the job site is ready and the wood flooring has been delivered, the time it will take to acclimate wood flooring will depend on:
- Expected seasonal change for your location
- Manufacturer recommendations
- Species of the flooring to be installed
- Climate conditions of the job site
- Use of imported or tropical species (which may need more time to acclimate because of higher density and oil and resin content)
To establish a baseline, the moisture content of the flooring should be measured immediately after delivery.
The most efficient way to record accurate wood moisture content is to measure the moisture content of 40 boards for every 1,000 square feet.
Levon agrees, saying, “We check up to 40 boxes and take moisture readings on different bundles.”
When we asked Levon if there was anything else he did to help acclimate the flooring product before installation he said, “The HVAC should be turned on 5 days before installation and left running after the job is complete. The main thing we need to do is to keep the environment as close to the living environment as we can. That’s very important when it comes to a successful installation.”
As the NWFA suggests, “Calculate what the optimal wood flooring moisture content is by dividing the high season and the low season. Example: If your region has an expected EMC from a low of 6% to a high of 9%, the baseline MC of the wood would be 7.5%.
How to Test Wood Flooring Moisture Content
Wagner Meters is the most respected moisture meter company in the world. It provides flooring professionals with quality tools that help establish a baseline and gather accurate moisture measurements.
These devices are instrumental for:
- Establishing baseline reading of wood moisture content at the time of delivery
- Concrete moisture testing to ensure conditions are ready to receive wood
- Subfloor moisture testing to ensure conditions are ready to receive wood
- Monitoring the wood flooring as it acclimates to the room
These moisture measurement tools are the most valuable instruments used in the acclimation process. They measure the moisture condition of the subfloor, the concrete, and the moisture content of the wood flooring to be installed. Obtaining precise, accurate measurements will help eliminate flooring failures.
Moisture measurements will also help you decide if the subfloor or concrete at the job site is dry enough for wood flooring. If the subfloor is too wet, the wood floor will absorb moisture and expand, and this can lead to problems.
If the flooring materials retain too much moisture at the time of installation, the flooring will shrink when equilibrium (EMC) is reached. This can cause wide gaps and spaces in the flooring.
These moisture content measurements are crucial if you have a problem with faulty flooring when it’s received from the manufacturer. The warranty of many manufacturers will be void if you can’t back up your work with solid evidence of a problem.
Levon recommends moisture meters to flooring professionals: “My moisture meter is always with me. If I ever have a situation, it’s there…I always have it handy. If you’re a wood flooring professional, you should always have a moisture meter with you.”
Free Download – 4 Reasons Your Hardwood Flooring Failed
How to Store Wood Flooring
Acclimation of wood flooring begins with proper storage at the job site.
Wood floor acclimation can be achieved by cross-stacking and spacing wood floor materials. This encourages air circulation around the boards.
How Long Does Hardwood Need to Acclimate?
Most manufacturers recommend hardwood materials acclimate for a minimum of 3 days with no maximum suggested.
In order to make a proper judgment call on the required acclimation time, you need to have a baseline and know what the moisture content of the wood flooring is when it is delivered.
Levon shared his on-site storage methods with us: “If the flooring is an unfinished material, we cross-stack the wood. If it’s a finished material, we read the instructions and follow the manufacturer’s recommendations. It doesn’t matter if it’s engineered or pre-finished. If there is a high content of moisture, it can still cause big problems.”
Wood Flooring Acclimation Takes as Long as It Takes
It’s important that wood floor materials reach a moisture content that is in equilibrium with regular living conditions. So, acclimation will take as long as it takes. Regular moisture readings will indicate when the wood flooring has stabilized and is in equilibrium (EMC) with its environment. At that point, no further changes will occur.
Wood Floor Acclimation with Engineered Flooring
Even with engineered flooring, manufacturers suggest coverage applies only if the job site is maintained between 30-50% relative humidity. These conditions must also exist after installation.
When asked if Levon acclimates engineered flooring, he said, “We don’t skip a step just because the flooring is engineered. We always check the moisture of the wood panels and the concrete. We take moisture content and relative humidity seriously. Those are 2 areas that can cause flooring failure.”
Floors perform well when you invest time during the installation process. The goal is to ensure stable and controlled moisture, temperature, and humidity.
Failure to properly prepare for wood floor acclimation before installation begins may compromise the integrity of your floor. Excessive gapping, warping, or cupping can occur after the installation is complete. The expansion joint may also be compromised, which will result in further damage.
Failure to acclimate the flooring will also void the manufacturer’s warranty if such problems arise.
When you take the time to prepare your job site location, bring in the wood flooring materials at the right time, determine the expected seasonal change for your location, and make sure everything is acclimated correctly, you’ll rarely if ever have a problem with hardwood flooring.
Make sure to use the most accurate wood moisture meter for your hardwood flooring moisture testing.
Free Download – 4 Reasons Your Hardwood Flooring Failed
Written by Wagner Meters, published first by ProInstaller
Larry Loffer is a senior technician at Wagner Meters, where he has over 30 years of experience in wood moisture measurement. With a degree in Computer Systems, Larry is involved in both hardware and software development of wood moisture measurement solutions.
Last updated on December 13th, 2021