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How Long Does it Take to Acclimate Hardwood Flooring?
Many contractors think bringing wood flooring to the installation site and letting it sit for a few days 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 within a relative humidity range of 30-50% is key for peak performance. The temperature should also remain between 60-80 degrees Fahrenheit.
How Long Does Hardwood Flooring Need to Acclimate?
Most manufacturers recommend hardwood materials acclimate for a minimum of 3 days with no maximum suggested.
To make a proper judgment call on the required acclimation time, you need to have a baseline and know the moisture content of the wood flooring 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. We read the instructions and follow the manufacturer’s recommendations if it’s a finished material. It doesn’t matter if it’s engineered or pre-finished. If there is a high moisture content, it can still cause big problems.”
summary
Most manufacturers recommend hardwood flooring materials acclimate for a minimum of 3 days with no maximum suggested.
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 ensure the relative humidity complies with recommended standards, which is 35-60%. We also ensure 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 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.
Suppose 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. In that case, 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 five days before installation
- Appropriate humidity and temperature inside the building have 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.
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 five 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.”
summary
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.
Useful Tip:
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
Wagner Meters carries various wood and concrete moisture measurement tools that take the guesswork out of the acclimation process by providing accurate moisture readings you can depend on.
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, leading to problems.
If the flooring materials retain too much moisture during hardwood floor 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.”
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.
Wood Flooring Acclimation Takes as Long as It Takes
Wood floor materials must 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.
Acclimation for Engineered Hardwood 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.
Click here to decide which moisture meter is right for you
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 August 26th, 2022
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Wonderful information about moisture meters, wood info, how long acclimate wood flooring, thanks a lot for sharing kind of content with us. Your blog gives the best and the most interesting information. I wonder if we can gather such practical information about it, a great post definitely to come across.
Is it OK to install engineered hardwood (3/8 inch) over existing engineered hardwood.
Thanks,
cee_paul1@hotmail.com
Paul,
I appreciate the question. The best way to answer your question is to refer you to NWFA Standards. They can explain the best way to proceed. They can be reached at nwfa.org. Thank you.
Hello great article.
i have a question from the great Northeast.
i have a old 1940 house that is undergoing a mold mitigation and hardwood floor removal down to the subfloor due to a month long undetected steam leak in the basement . This caused mold to grow in the basement and between the floor and subfloor. so to treat correctly they needed to remove the floor down to the subfloor . my question is now that the floor removal has been completed and the mold has all been removed . The house is really dry, dryer than it will ever be due to all the dehumidifiers fans and mitigation equipment. Should i give the place a few weeks to acclimate without the new unfinished floors or should i bring in the flooring in now and let everything acclimate as one? The sub flooring are pine boards not plywood with small spaces between the boards about an 1/8 of an inch wide in some places . should i install a true vapor barrier between the subfloor like roofing paper or tyvek or just use the standard pink paper? The basement is unconditioned, cool in the summer due to the ground temp and warm in the winter due to the boiler, it also has a very dry dirt floor. The old floors had nothing between the subfloor and the hardwood white oak floors and there was noticeable cupping and crowning between the seasons.
Thanks in advance for your time and knowledge
Regards Ned
Hi Ned,
Thanks for writing in. I would suggest you contact NWFA.org. there you will find everything you need to know about acclimation and your flooring vs. subfloor moisture. Be sure to have a quality moisture meter to follow the process. Good luck!
Great article. I grabbed some beetle kill tongue and groove to go up on a ceiling in a laundry room. We live southeast of Denver where it is very dry pretty much year round and we keep the windows open as much as possible so humidity is very low usually ~22-30%(right now it is 20% in the house). Because the wood is dead when harvested, i imagine that the wood is pretty dry. I’ve had it sitting in the laundry room for two days, but i’m wondering if it is not necessary. Thoughts on how long this should sit? i do not have a hygrometer.
Hi Dan,
Thanks for writing in. I would suggest getting a thermo hygrometer and acclimate the wood as best you can prior to installation. Even with the best installations, you can expect to see some minimal gapping seasonally.
https://www.wagnermeters.com/shop/th-200-thermo-hygrometer/
Dan,
Yes, the wood is probably sufficiently dry, but the only way to quickly know for sure is to measure with a moisture meter.
Hello and thanks so much for this article and blog. I would very much appreciate any feedback on an issue we are having with our engineered hardwood flooring installed in January 2019. We are hearing creaking and popping noises on the 2nd floor, which seems to begin the the mornings and we wake up to the noise. Then at random times of the day, with or without walking on the floor. The house was built in 1995 and we are not aware of any issues with the wood subfloor. We are pretty sure that the wood was not acclimated before installation, and we believe the installation was with nails. Most of the noise is on its own (without walking on it), in 2nd floor bedrooms and no visual installation issues. The sound appears to be from the edges near baseboards/walls. An installer we consulted with recommended removing the baseboards to see if there is insufficient spacing, and cutting the wood back to give room. The installer believes that, as a result of not acclimating the wood, that the wood expanded and is pushing against the walls, causing the noise. This installer also recommends using a very thin glue gun to insert glue in certain areas. Humidity levels in the home are between 38% to 49%. The installer says that, no guarantee, however that this should resolve most of the noise issues. Do you advise proceeding with the installer’s advice? And, do you have any other suggestions?
Thanks for the question, Nabeel. Soundproofing floors or reducing noise is not our area of expertise, so I’d certainly recommend you listen to advice from professionals in that area. On a personal level, I’ve heard similar advice from installers in the past – that is, adding some sort of construction adhesive to the floor joists to restrict movement. If you can afford to attempt it and you think they know what they’re talking about, then go for it!
Nice informative post…I got very useful information about wood floors through this blog.,., Thank you and keep sharing such
blogs.
thank you so much for your response jason. the wood is dry per say – as it’s been inside, it’s just the moisture content. if I purchase a meter to test the moisture content, how would I know the real condition of the house to compare it to? so sorry to ask a million questions – just looking to understand my best step by step forward. especially with drywall needing to go up in the space the floor is also going in. thank you so much for any guidance you can provide!
Michelle:
If you purchase a thermo-hygrometer that measures %RH and temperature in the air you can enter that information into a “calculator” (WoodH2O app) that will give you what is called the equilibrium moisture content (EMC). Based on these measured parameters, wood left in that environment will equilibrate to that equilibrium moisture content. This is, in essence, the target number you use when measuring with the moisture meter. Thanks.
hello! thank you for this article. we are doing a remodel of a 1500 square foot home with original red oak floors from 1950 in marin county, california. it’s hot here in the summer (75-90 degrees) and cool and damp in the winter (humid and 50s) there are a few small areas of pet soil damage we are replacing and one area of the home that we are replacing vinyl floors, the rest is all being refinished. the hardwood 3” planks were delivered 2 months ago, in bundles, and have been sitting in our unfinished kitchen – where there are still some windows and door openings not sealed off until the house, and where the wood subfloor let’s in air from the unconditioned crawlspace. we were going to run heaters as the hvac is not yet installed. drywall is about to go up, and painting was going to be last. I’m really worried we have ruined the wood sitting in the house, and am wondering the best plan now! any advice?
Michelle:
Thanks for the comments/question. The uninstalled wood in the house is like a sponge and will absorb and expel moisture with changes in the environment. For the most part, wood in this uninstalled state will usually be fine barring rain or large amounts of physical moisture. Where there may be an issue is once the home is fully enclosed and HVAC is running. If the wood has absorbed moisture prior, it may take a while to acclimate the planks to the “real” condition of the house and if you install the floor prior to this acclimation, then your potential for problems will increase.
We moved into a new construction home in NC this past spring. Within a month of moving in we noticed our floors starting to splinter. Fast forward 9 months and we have over 250 planks in 1200 sq ft of white oak hardwood that are affected. Some are splintered (big splinters, something that would likely send you to the hospital if you took one in your foot), others are cracked (not surface checks. All the way through), some exhibit shake and some are checked.
We’ve had multiple NWFA inspectors through, but these folks were hired by the builder and will not talk to us directly. Apparently the wood was brought in prior to HVAC running, 5 months before the property went on the market (who knows in what phase of construction the floors were installed). It sat in the unconditioned home in the middle of summer for a couple days before installation. Obviously, it didn’t acclimate and we continue to see the fallout from this error. According to the installer, the MC of the wood pre-install was 7.5%. When they came back after the issue was reported MC was at 5%
My questions is this: Seeing that this has presented as a degenerative issue, do you foresee success by replacing the affected boards, sanding and refinishing, or do you believe replacement is the proper, comprehensive fix?
Concerned Consumer:
Thanks for the questions and sorry for the issues. The first question in my mind is 1) Do you keep the temperature and relative humidity in the home consistent throughout the year? 2) If so, based on these two parameters what should the equilibrium moisture content of the floor be? You can calculate that from various online apps or we offer one for your smart device called WoodH2O. If the installer did enough measurements for us to trust the 7.5%, our question would be if the 5.5% represents wood that is fully acclimated? If so, I would expect to also see some type of gapping or cupping in the floor along with the problems you are stating. Personally, I would hire my own NWFA inspector and pay him/her to work FOR you, giving you information. I hope this helps. Good luck.
The only way to paint prior to the floors is to paint the walls and either have the baseboard installed at the height of the thickness of the actual flooring (this option always ends up imperfect with gaps in places). Or you paint the walls and then install flooring, and then install trim after the flooring. Painters will never like this option because you’ll have to caulk and hand paint after the baseboard is installed. So, I’m not sure of a good way to wait until paint has been finished before installing the floors. Any ideas?
Morgan:
Thanks for the question. Usually what I have seen is the painters paint the walls and installed door casings, leaving the casings full length. They can then leave the painted base on the job (assuming it is going to be painted) and then the flooring trade cuts the casing with a backsaw and installs the base after the flooring is installed. Obviously they shouldn’t be expected to do this for free, but overall it makes for a cleaner install.
It’s interesting to know that wood flooring installation should always be the last job at any construction project. My husband and I are working on a remodeling project for our house, and we are looking for advice. I will recommend my husband to work on our hardwood last to help it acclimate.
Thank you for the tip about keeping the wood in a place that has 30-50% humidity. I’m replacing my carpet downstairs with hardwood, and I want it to last as long as possible. I’ll make sure my temperature and humidity are at the right place before I do anything.
I live in a new house with close to 3000 sq. Ft of narrow white oak floors in Dallas, TX. I know the wood was left stacked in the house for a while but do not know if the was left long enough for the wood to acclimate properly because now the floors are cupping everywhere. It’s not severe but is noticeable everywhere the light hits and worse in one area by a door to the garage where you can feel it when you walk across it. The flooring company is talking about sanding it all the way down and refinishing it, which means moving us out. The moisture reading in the house is a bit high it runs about 57%. They came and did moisture readings on the wood and deep down it is about 10% and higher up about 8%. I know that if they sand the floor while it’s cupped that it can later crown if the floor dries out a bit. If this floor is cupping because it wasn’t acclimated properly does the wood need to be removed and new wood installed or will sanding and refinishing solve our problem. I don’t want to move out have them do it and then it cups again or it ends up crowning and we have to be moved out again. We just moved in and this is heartbreaking.
Kelly:
Thanks for the questions and sorry for your issues. With cupping, there needs to be a moisture variance between the bottom of the board and the top, which there is here. (I don’t necessarily believe the absolute moisture readings, but that is of little issue here) Assuming the boards were acclimated to a proper moisture content prior to installation, the question then becomes why the moisture differential? Is the moisture coming from the bottom or is it being dried out from the top? Based on your comment about 57% RH (which is on the high side) I don’t see that the wood is being dried out on the top side, leaving the potential that the moisture is coming from the bottom. Is this floor installed on a concrete slab? Has the moisture been measured in the slab? The crowning potential you speak of here is usually when a floor is sanded and then the situation that caused the problem, in the first place, reverses itself. Sanding a cupped floor usually isn’t the best for the overall longevity of the floor, but severity and different situations will vary. I would want to have a better idea of what has caused the problem, solve it if necessary, and then come up with a solution.
I didn’t know that this was a thing as we’ve had new floors come and go at work with no issues. I’ll have to keep this in mind for when I do the floors at home. That and I’d for sure get the help of someone who knew what they were doing when it comes to this.
HOW SOON CAN YOU WALK ON THE FLOORS AFTER INSTALLATION?
CYNTHIA:
THANKS FOR THE QUESTION. IT REALLY DEPENDS ON THE TYPE OF FLOORING AND MANUFACTURER. THIS IS A QUESTION FOR THE SPECIFIC FLOORING MANUFACTURER YOU ARE USING ON THE PROJECT. GOOD LUCK!
I live in South Florida.
Several acacia trees (some huge) are going to be harvested and milled on site.
I hope to space-stack and air dry for flooring. Super humid and hot down here.
They’ll be restacked indoors and acclimated when HVAC is installed and house is
sealed. Yes- I need meter.
Does it need kiln drying?
If yes— how?
Hi Phyllis,
Kiln drying speeds up the drying process but is not required.
You can “air dry” these green boards but it can take weeks.
Make sure they are stacked evenly with spacers between boards and the spacers are right underneath each other to prevent warped boards while drying. It is also a good idea to have weight on the top.
Thanks. Exactly what we were looking for.
Since solid hardwoods are prone to scratches and dents, you need to pay special attention to its species (i.e. Oak, Maple, etc.) and how to better take care of it. But the great thing about solid hardwood floors is that it can be refinished or re-sanded numerous times, extending its life literally for years to come
Solid hardwood floors come either unfinished or pre-finished. This type of wood flooring is solid all the way from top to bottom. Unfinished hardwoods are a bit inexpensive to purchase and it requires immediate sanding, optional staining, and sealing after installation, which will require you at least 48 hours for the sealant to dry.
I’ve always wanted hardwood floors and this article convinced me even more than that’s what I want! I just bought a new home and I’m thinking about replacing all of the carpets with wood. I actually had no idea that wood floors could add value to a home. Thanks for the heads up!
The unfinished red oak flooring that I purchased was delivered today in 20 square foot bundles. The wood was stacked in bundles in the rooms where they will be installed. 15 in one room 10 in another and 13 in another.
My question is should I loosen the straps and spread out the wood (which would make quite a mess) or can I leave them to acclimate strapped in the bundles as they were delivered?
Ron,
“Wood floor acclimation can be achieved by cross-stacking and spacing wood floor materials to encourage air circulation around the boards. Most manufacturers recommend materials acclimate for a minimum of three days with no maximum suggested.”
In essence, the material will acclimate faster when all surfaces are exposed to the surrounding conditions. If the flooring is kept in bundles, pieces in the middle will not have that exposure.
I think it’s unfortunate that most sellers of wood flooring do not make the customer fully aware of the preparation issues. We bought a very nice engineered floor, yet we are now into a full week and still not able to install. If we had known this we would have ordered it and had it delivered much sooner, thought we just needed to get it there and the installer would come and put it in. The contractor says he will not install until it’s ready and although it is a major inconvenience now, we will regret it soon after. I am looking forward to the new floor, just frustrated and worried that we may have purchased a defective product since it has been almost a week and acclimation is not complete. Do you know how long we would have to wait before we actually learned that the flooring is not going to get any better? Feeling frustrated.
Thank you for all of the interesting information, wish I had seen this sooner!
Your installer is doing the right thing. It is very important to let the flooring acclimate in its installation environment before installation. This allows the flooring to slightly expand/shrink as it adjusts to its new environment BEFORE it is installed.
I love the look of oak floors, and I plan on having it installed in the spring. I want it to be perfect, so it is important that the wood has time to acclimate. It’s very dry where I live, so I doubt the humidity would level would fall in the 30-60% range. Should I humidify my house before I order the timber?
Hi Kairi,
It is important to allow the flooring to equilibrate in the environment it will be installed. It’s even more important to maintain a constant level of humidity as much as possible.
A moisture meter such as our Wagner MMC220 can measure every piece of flooring before installation to confirm even moisture content. Our TH-200 Thermo-Hygrometer monitors temperature and humidity. These two tools along with our free WoodH2O app are essential for a successful flooring installation.
Please visit http://www.wagnermeters.com/wood-flooring/ for more info and free flooring articles.
Larry, nice article with good information concerning MC, temp, and RH and other factors to consider before installing wood flooring. However, I do have a question as to which installation method is best to use after the MC, RH, and temp are at ideal conditions.
My wife and I live in Houston, TX and live in a single story house built over a concrete slab. The house is 22 years old. Our indoor RH is ~50%-55%. We would like to replace the existing vinyl and carpet flooring throughout the house and was looking at engineering wood flooring or tiled flooring that looks like wood.
We called various contractors and all seemed to offer up their own suggestion as to the type of installation regarding the wood flooring. Some say we should use a floating floor system, others want to build up the existing flooring ~ 1 1/2″ with wood underlayment and then nail in place, while others say go with glue.
Assuming that the concrete slab is completely dry and can accept wood flooring which of the three methods (floating, nail in place, or glue down) would be best to use here in Houston, TX. Thanks for your time.
Bob,
Since this is more of an application question rather than moisture related, I will refer you to the National Wood Flooring Association (NWFA.org). They can answer this question.
I’m beginning to believe that hardwood manufactors are drying the wood too much. I’m 3rd generation hardwood pro, been doing it everyday for over 20 years and I’m in the south so this may not be an issue in other parts of the country. We live and work in the south, our wood comes from the south. Here’s my theory. It seems that almost every hardwood delivery is under 3% moisture. In wide wood over 3 and 1/4 you will see cupping at 7% and under. Doing new construction you never really know where the house will settle after a complet season, if it’s an addition with hardwood existing it’s a lot easier to determine where you think it will settle. Its never guaranteed as new construction is a lot better than say 40 years ago, so a lot of time the new will hold less. Ok back to my theory manufactors are producing wood under 3% so if you deliver to a normal new construction site just the aculmation process is going to cause the boards to start cupping even before the instlation process begains. Say the house is going to hold around 8% (which is great if you live in GA) the 5% gain will defiently affect the floor. And if the wet Rainey, humid season hits just after the instlation or sanding process it can jump 3 to 4 points, I’ve personally seen 2 to 3% cause major headaches in floors over 4 inches in width No matter if it’s no more that a 3% difference between sub and your flooring when installed. I personally think the NWFA should hold manufacters in different parts of the country to different standrads, say in the south I don’t believe floors should be dried under at minum 5% Pretty much every house in the southeast is gonna hold around 7% or more, very few ocations will it hold less. So if it’s under 3 and climbs to 7 or say 9 your headed for a problem, your either going to fight it together( after its slightly cupped and the tongue and grove has actually swollen ) or put it in early and let it aclmate installed nailed to the floor which has its own problem areas( cupping and popping) so if it was dried down to around 5%, 2 to 3 % would be a lot less affected and could reasonably be aclimated in around a week. But natural products have a mind of there own sometimes. Curently sanding new 4 inch (builder installed his self) floor reads 7% but is cupped like crazy which is bad for people buying house sure to have issues with popping down the road. Sorry to ramble on but I’ll sum it up right here. I think the NWFA should set different standards for different regions in the south wood should probably not be dried under 5%, say out west in your dryer regions under 3 may be acceptable. But not in the south.