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Can Wood Floor Cupping Be Fixed?
You’ve had a beautiful hardwood floor installed in your home. But after a while, something doesn’t look right—or feel right. Maybe the floor seems “wavy” or even rippled. You may notice small, raised ridges along the edges of some planks on the floor.
What’s happening to your previously gorgeous flooring? And can it be stopped?
In this article we’ll cover some wood floor cupping topics such as:
- What is Wood Floor Cupping?
- How to Fix Hardwood Floor Cupping
- What Does Cupping on a Wood Floor Look Like?
- Why Does Cupping Happen?
- What are the Common Causes of Cupping in Flooring?
- How Long Does it Take for Cupping to Go Away?
- What Happens if Cupping Doesn’t Get Fixed?
- What NOT To Do When You Notice Cupping in Your Floor
- The FIRST Thing To Do When Cupping is Discovered
Cupping is one of the unfortunately common issues that can plague hardwood floors. It can happen to most types of wood, and it’s often the first observable sign your floor is being affected by moisture.
Since wood reacts to moisture quickly, floorboards can warp as they react to the change in their internal moisture content (MC) after the floor’s installation. But if you catch it early and can address the moisture issue, there is hope in returning your floor to normal.
Here’s what you need to know.
What is Wood Floor Cupping?
Cupping in hardwood floors is caused by changes in moisture levels, whether decreases in the air RH above or increases in moisture from below. Whatever the cause, a moisture imbalance develops from the bottom of the floor to the top. This imbalance causes each plank to develop a concave shape with pronounced raised edges.
How to Fix Hardwood Floor Cupping – 5 Steps
1. Make sure you have a reliable wood moisture meter
So you know how much the wood moisture content has risen or can identify wet problem areas. While several types of meters are available, few allow for multiple tests in multiple areas over and over without damaging the wood. The Wagner Meters Orion® moisture meter line uses electromagnetic wave frequency (EMF) to measure large areas.
2. Determine where the moisture is coming from.
As referenced above, is the cupping uniform and seasonal? Is it confined to one area? Has the floor been installed recently, or could there be more moisture in your crawlspace or basement than in the living space?
3. Get a dehumidifier
If you have a basement or an area of the house that tends to be more humid than other areas. If you live in a place with humid summers, you may need to run it seasonally to keep your wood floors in top shape year-round. The key is controlling the climate in your home and keeping it as consistent as possible.
4. Maintain your floor properly
Using the correct cleaning methods and products made specifically for wood floors. Always dry spills thoroughly, and routinely check wood floor areas around sinks, dishwashers, bathtubs, and other areas more likely to have leaks or spills.
5. After a significant leak or spill
If water or other liquids have had time to absorb into the floor and subfloor, you may need to contact professionals for high-powered drying equipment. A dehumidifier is great for humidity in the air, but wet warped floors need a more direct and aggressive approach to avoid lasting damage.
What Does Cupping on a Wood Floor Look Like?
When moisture interacts with a hardwood floor, the side of the boards closest to the moisture expands. This expansion can be in the form of cupping (the center of the board is lower than the edges) or crowning (the center of the board is higher than the edges).
Both situations, although different, are both due to a moisture imbalance in the boards caused by either the addition of moisture or the extraction of moisture from the floor.
Sometimes the early stages of cupping can be noticed when the light comes in from a window and reflects onto a wood floor. You can see small shadows where the edges of each floorboard are slightly higher than the middle.
Why Does Cupping Happen?
In short, moisture. Wood, even when it’s treated and sealed, is still a porous, fibrous material. It can still react with the moisture content (MC) in the air around it. Materials like wood will balance (equilibrate) their MC with their surroundings, similar to the principle of osmosis.
So if the air is humid, the wood will absorb more moisture from the air, and it will swell. If the air is dry, wood fibers will release some of its moisture back into the air and it can shrink back down.
It’s common for moisture to enter the floorboards from below through the subfloor. This is why the bottom of the board swells and makes the edges curve upward into an almost wave-like pattern.
Cupping can happen even to a flawlessly-installed wood floor, depending on the conditions of the building and the environment. However, several common situations that are known to cause cupping can be addressed and can even be reversed.
Avoid cupping-related moisture issues with an accurate wood moisture meter to test hardwood flooring.
What are the Common Causes of Cupping in Flooring?
Here are the 5 common causes of wood floor cupping:
1. Change in the amount of moisture in the air (relative humidity)
If you live in an area with humid summers and dry winters, or even vice versa, your wood floor can react to the changing amount of humidity in the air. It expands during one season and contracts in the other.
If cupping is happening in a relatively uniform manner throughout your house, and the degree of cupping is not drastic, this is likely the cause.
2. Subfloor moisture
If there is excess moisture in the concrete slab, crawl space, or basement below your wood floor, this can cause cupping. This is especially common with new construction if the floor is installed before any HVAC runs within your home. It can also happen later if your basement or crawl space harbors more humidity in general.
3. Leaks or spills
Cupping due to leakage will usually be confined to areas around sinks, dishwashers, etc. If a leak is slow or small, the cupping can occur gradually, and you may not notice it until it worsens. Sudden leaks or spills can cause cupping if they aren’t cleaned up quickly or thoroughly or if some moisture is left behind.
4. Improper care/cleaning
On a similar note, especially when cleaning up more significant leaks and spills, cupping can come about if any moisture is left behind after cleanup. What’s more, unless proper cleaning techniques and supplies are used, further damage could result as well.
5. Improper installation
If a hardwood floor is installed before a subfloor is adequately dried or before the floorboards reach an equilibrium moisture content (EMC), such as before the inside of a building’s air is conditioned, there is a chance for cupping later on.
As furniture and people begin to inhabit the area, it will bring about a new level of moisture and temperature to the air.
You want to ensure that moisture levels between the subfloor and the finished floor have reached proper EMC for the long term. And to make absolutely sure the moisture readings are optimal for beginning the installation, you want the most accurate moisture measurement tools possible.
How Long Does it Take for Cupping to Go Away?
In many cases, if cupping isn’t severe, the issue can be fixed once the moisture issue is fixed. Since the cupping process is the wood reacting to moisture, if the wood’s moisture level returns to the proper equilibrium, the cupping can resolve.
Depending on the type of moisture issue, however, will determine how easily it can be fixed or how much effort it will take.
Free Download – 4 Reasons Your Hardwood Flooring Failed
What Happens if Cupping Doesn’t Get Fixed?
Besides the visible warping of your hardwood floorboards, the floor could fail. The cupping could continue to worsen and create gaps between the boards. If/when the relative humidity drops, the boards may not return to their original shape and can buckle away from the subfloor or even splinter and crack.
The big issue, however, is still moisture. If the cupping in the floorboards doesn’t go away, it could mean that the underlying moisture issue was not properly addressed and still needs some attention. While cupping can remain after a severe event like flooding, persistent cupping is worth investigating.
Prolonged moisture issues can lead to many types of flooring failures, so it pays to be safe.
What NOT To Do When You Notice Cupping in Your Floor
One rookie mistake is to simply sand the floor down until its level again. But once again, the moisture problem that caused the cupping has not been dealt with. For example, if the cupping happened due to humidity from an exceptionally wet summer and you sanded down the cupped areas, the air dries out the wood can warp the other way, causing crowning.
You also don’t want to assume your floor has already failed. There is still hope! Many moisture issues can be fixed through household climate control, taking moisture readings throughout the house, or seeking out undetected leaks or spots where moisture could creep in from other areas.
To avoid these mistakes, there is a way to test for a change in your home’s ambient conditions over time. Relative humidity data loggers can tell you what had changed in ambient moisture levels when it changed, and for how long. This information can help you determine what actions to take with your flooring.
The FIRST Thing To Do When Cupping is Discovered
If nothing else, the appearance of cupping tips you off, and your hardwood floor is susceptible to moisture problems. Even before you call a professional if you have a reliable wood moisture meter, you can use it to take multiple readings throughout your home. You’ll have a much better idea of what kind of situation you have on your hands.
You might be able to figure out how to remedy the situation yourself if you find it’s due to humidity in the air or a leak or spill. And if you do discover it’s a severe issue, you’ll have much more precise information to give the professionals, so they don’t have to spend as much time (and your money) doing detective work.
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Safeguard your beautiful hardwood floors with moisture measurements you can trust. Learn more about how Wagner Meters’ Orion® moisture meter line is easy to use while providing the most accurate readings available on the market.
Avoid moisture-related issues with an accurate wood moisture meter to test your hardwood flooring.
If you want to learn more about other hardwood flooring problems, check out our other two articles:
Hardwood Floor Problems
Spotting the Trouble
Learn the 10 reasons why wood flooring installers need a wood moisture meter.
Jason has 20+ years’ experience in sales and sales management in a spectrum of industries and has successfully launched a variety of products to the market, including the original Rapid RH® concrete moisture tests. He currently works with Wagner Meters as our Rapid RH® product sales manager.
Last updated on March 20th, 2024
800-634-9961
Hi Jason,
I am looking at acquiring my dads old home built in the 60’s. My father replaced the floors with both tile and oak hardwood. There has been some water damage under the house from both plumbing leaks and water leaking under the foundation over time. I’m seeing a lot of cupping, lifting, and crowning throughout the hardwood and tons of cracks in the tile. A sump pump has been installed under the house as well as new vapor barrier and I saw some insulation put under the floorboards but it looks like the pink fiberglass insulation that can soak up moisture. I also was seeing dark spots in the insulation in the attic that makes me concerned mold has been growing from all of the untended to damage. We are working on stopping a new found leak under the foundation and a dehumidifier has been installed and is running on a timer to go on every few hours for an hour to see if we can dry everything out and see how they resettle. The property has been in renters and third party property managers hands over the years and I’m still getting clarity on how long this has been going on but I know for at least six years the more serious issues have been getting patched but am unclear on the damage that was done before the water issues were found. What would you recommend?
Briana:
Thanks for the question. Honestly, I would hire a reputable building inspector to evaluate the entire structure. Once you have this evaluation, you can start to piece together what it may cost to make repairs to ensure the house lasts another 60 years. Good luck.
Hi Jason,
I recently had my cupped, factory finished 5″ Hickory floor sanded and finished (original installer did not glue, just stapled). The floor was cupped due to poor acclimation to the home. The Inspector from the NWFA said the subfloors moisture content was too high vs the hardwood (over 2% difference). The cupping started about 7 months after the floors were completed (new build home). We waited until the moisture levels were in check (over 200 readings over 7 months) and had the floors sanded and refinished (about a year and 4 months after first being noticed), so just over 2 years after flooring was originally installed, with two full heating and cooling cycles. One week after the floors were refinished they started to cup again. The sand and refinish was done by a certified NWFA installer. Any ideas? Will it lay down again or am I out 20k?
Jason:
Sorry for all of the issues. There are a lot of details here, many of the pieces are moving and many are vague. Due to this, I really have more questions, for details, than I do answers. I would be more than happy to discuss this if you would like, 1-800-634-9961 x235.
To simply answer the question, it is obvious that there is a moisture imbalance happening somehow, so until that reason is identified, I don’t see the floor relaxing.
Hi Jason. We have solid oak floors and we had a kitchen faucet run over for an unspecified amount of time by accident (the water was at a low volume but could have been a couple of hours. I came downstairs to a big puddle 6×12 that I cleaned up, we left the fan running and some dry towels down on the floor. A few hours later two planks were severely cupped and still are (1 month later) and the rest of the hardwood floors extending to the living room look cupped from an angle, some you can definitely feel when you walk. Will this settle down or is it ruined at this point.
Nora:
Thanks for the question. The answer, its hard to say. In theory, yes, it really depends on how much moisture got under the floor and how much is still there. You can either do nothing, maintaining conditions in the house, and hope for the best or look for companies that use products like this and see if they can help https://www.airmovers.com/products/water-damaged-wood-floor-drying-mats I’m am not recommending one over the other, just giving you options. Good luck.
Hello my name is Peter DL, I was in the flooring industry for over 20 yrs. My son has taking over the business for 3 plus years now, my question is I installed a 4” maple 3/4 “ solid som10 yrs. Or so , on my neighbor’s ranch style home in the living room,2- bedrooms and hallway. Floor was acclimated for about a wk or so in summer time in a south shore community about 200 yards across bay .it was installed above crawlspace at the time of installation the wood was at 6.7 on my moisture meter sanded and finished with a waterborne finish. Neighbor started noticing minor cupping about 2 yrs. Later and gradually it’s become worse , fyi I did not ck under crawl space and have mentioned to my neighbor about possible moisture problems . He’s been saying that he has plastic and insulation underneath. I see the cupping to be about 3-5 mm , he’s asking me to sanded down to a flat condition and as I have read on some of your answers that I can create more of a problem witch I agree what can I do to help to take care of this problem. Thank you
Peter@sparklefloorsandcarpet.com. I appreciate your response.
Peter:
Thanks for the question. A few general questions:
1) 6.7% MC at time of install seems quite low for a coastal environment. What was the temperature and RH% then?
2) What is the general RH% and temperature of the interior of the home during the year? Do we know what the temperature and RH% is in the crawlspace of the house?
3) What is the ventilation like in the crawlspace?
In the end, 5mm is a decent lift on the edges. Sanding it down MAY be ok, as long as the conditions that are being experienced stay consistent. The problem you run into is many will sand the problem away and then the conditions will get back to the “normal” range and the floor will relax. Unfortunately, when that happens after sanding away the problem, it can cause crowning in the floor. Good luck.
Dear Jason: I live in Italy. On two separate occasions during the night, I knocked over drinks onto my bedroom floor and have slight cupping on a couple of the floorboards where the ends meet. The wood is perhaps oak. The cupping is not drastic, just noticeable (a foot or two in total) when you walk barefoot or slide a chair. You mentioned sanding is not advised, but isn’t there an easier way, through applying pressure, or by sanding a few square inches to the slightly cupped corner areas? You see, see they were water spills. Several months have passed so I don’t the curved corners are going to flatten. Best, David
David:
Thanks for the email. I’m not sure what the humidity is like in your area specifically, but it sounds like you may need to bring a dehumidifier into the area to help things dry out. The moisture may have gotten below the surface of the wood and the environment in the room may not be conducive for the moisture to escape. Having the humidifier for a bit may help. Sanding a curled floor like this will look ok cosmetically, but when the floor/subfloor does dry, the floor will show the inconsistent thickness of the floor.
Can adding weight on a cupped wood floor following a water leak help the floor to flatten or is mostly a matter of time for the wood to hopefully return to its original shape?
Mike:
Thanks for the question. If the wood hasn’t been permanently damaged, time and consistent temperature and humidity in the space are the keys to “flattening”. Good luck.
Hi Jason,
I have a friend who had their house gutted & rebuilt last year. The 3″ white oak floors were laid in June last year after acclimating in the house for 30+ days. The atmosphere in the house is all electronically controlled. Humidity at 50% & temperature 50° Oct – May & 69°June-Sept. The owner first noticed the cupping in July & it has not changed.
Is it possible the floors were not sanded prior to installation? Any other suggestions? Part of the floor is on slab but most is above a crawl space. I have been a cabinet maker for 30+ years and have never seen cupping this bad. Areas are off by 2-3mm within a 3″ span.
Many thanks,
Jeff
Jeff:
Thanks for the question. The information you have provided doesn’t really establish why this cupping would be happening based completely on the ambient environment. The one thing we don’t know, though is, even though the floor acclimated for 30 days, what was the actual moisture content of the floor at installation we also don’t know what the moisture content was of the subfloor before installation. Both of these should be compared to the current readings obtained from both. Also, most wood flooring manufacturers recommend 60 to 80F, so you may want to let your friend know that the environment should be warmer Oct-May. Good luck.
We have had our hardwood floors for about 7 years and they have weathered time with no issues.
We have an elderly dog that during the night last week had an accident on our kitchen floor. I cleaned the area as soon as I found it, but I don’t know how long the urine was on the floor. There is a small area of very noticeable cupping (can feel it through my shoes). Will the cupping improve with time? We live in a pretty dry climate, so I know that humidity is not an issue.
Chris:
I wish I could say yes…for sure, but the best answer is it may, but it will take some time.
hello,
We are in the process of buying a house that was taken over by HUD after it was abandoned. It has been vacant with HVAC turned off for over a year.
Location: Near Toledo, Ohio so humid summers and cold wet winters.
Build 1958
Thin strip hardwood over basement (thankfully the sump pump appears to have had power this whole time.
Obvious cupping is evident throughout (expected with no environmental control, but doesn’t look quite as bad as your article picture:).
The whole house needs some work so our plan is to
1. get the HVAC hooked back up,
2. possibly run a dehumidifier in the basement.
3. Do need demolition and prep and sourcing building supplies for everything else (we figure at least two weeks, possibly a month before we are ready to do anything with the floor.
4. See if the cupping has improved and go.from there.
So, is a floor that has likely been cupped for a year or.more worth.trying to save (there are about 6 planks near a bay window that we will need to replace after replacing the window)?
If we do need to install all new flooring what can we install over this? Would sanding before installing over it, if the cupping is still present, be best?
Our house is a little over 100 years old with unfinished wood floors. We want to lay laminate flooring on top of it. But in the summer time the humidity causes the floor to cup in certain areas is there anyway I can fix that so I can lay laminate flooring on top of it. So the laminate won’t get ruined.
Stephanie:
Thank you for the questions. The cupping is probably happening because there is some kind of moisture imbalance either in the home or crawlspace. It would be best to measure the relative humidity and temperature in the home, and the crawl space, when the floor isn’t cupped and when it is to see which area is changing. I would also check for proper ventilation and some type of vapor retarder on the soil in the crawl space. Obviously, this is assuming your floor is installer on a wood subfloor, not concrete. As for installing over the wood floor, I would consult the manufacturer of the laminate to ask this question. May won’t allow it due to just the issue you are describing where the wood floor cups beneath the laminate and cause issues with the laminate. Good luck.
Hi
I have a Red mangaris deck on the front and back of my house. I used 18 foot planks uncut and used side screws not visible on top. It’s been there about six months. I finished it with penofin oil though the front only has one coat. I live in Southern California and we had some rains over Christmas holiday and my beautiful wood deck started cupping mainly the one in the front. That deck was built over top of an existing concrete deck. I am wondering if there’s a way to fix the cupping?
Thank you
Angela
Angela,
The only way to fix the cupping is to allow it to completely dry and hope it retains its original shape. Best of luck.
I have a newly installed wood floor in my newly built home. The floors were installed in mid April and we moved in in May. By mid July we noticed the floor was cupping. We have a ranch home with full finished basement. I placed a dehumidifier in the basement and had it continuously run. I was emptying it out 2-3 times a day. The builder has installed a auxiliary heater in the basement which he suggested I keep it at 74 degrees. I have. The builder feels we should have run a dehumidifier from the start of the summer.
Any suggestions on how to move forward? My contractor has suggested placing heat mats on the floors to dry out the wood and see if the cupping improves.
Thank you for your help.
Charlie
Charlie:
Thanks for the questions. I am assuming the issue is with the floors in the basement or is it the entire house? If the basement, are these solid or engineered wood floors? There are so many questions here and without them, there really are no answers. If it’s installed on concrete, it could be a concrete moisture issue. I would recommend that you have a wood flooring inspector come out and give a better idea of what the culprit might be. Here is a link to find an inspector NWFA Professional Search (https://www.woodfloors.org/find-a-professional.aspx) | NWFA (woodfloors.org).
Good luck.
Hi, this page is a great resource. Do you know if there is a specification or tolerance for cupping / flatness? In other words, what degree of measurable cupping qualifies as a defect?
Michael,
I would refer to NWFA for proper guidelines on cupping tolerances.
Hi Jason,
Our existing wood floor for 30 years is located in the foyer, hallway, powder room, kitchen and dinette rooms. Our renovation builder purchased wood that matched our maple floor and stored the wood in our garage during the following winter months. He installed the new wood 3″ planks in our family room, living and dining rooms, and small den. The entire wood floor was sanded, stained, and sealed in the early spring. We noticed the edges of the floor planks were slightly raised in June after the renovation was completed. The family room floor looks fine, however, all the other rooms floors are cupping. The floor in the powder room is crowning.
Why would the flooring in the family room be fine while in all the other rooms it is cupping?
Thank you,
Doug
Doug:
Thanks for the email. Based on the information you provided, it would be really hard to pinpoint the culprit. Obviously, there is a moisture imbalance in the wood. What was the moisture content of the wood prior to installation? What was the temperature and humidity in the home during the construction process and new floor acclimation? Storing the new wood in the garage MAY have been fine, but the floor would still need to be moved inside to acclimate for a duration of time to the indoor conditions. There are actually more questions than answers here. I would contact a certified wood flooring inspector to come out and evaluate the floor. One can be found at http://www.NWFA.org Good luck.
My husband and I just bought a cute 100 yr old house a couple of months ago (during the summer it is now winter) and the two upstairs rooms both have cupped floors.
There is evidence of previous water damage to both rooms. But both floors dont show much water damage (beyond the cupping.) We have so far been unable to determine where water could have entered the room (based on the damage.) So im not so worried about a major water leak (there is also no plumbing upstairs of any kind.)
The downstairs wood floors are beautiful and have no evidence of warping Im hoping you have a solutions that means we don’t have to replace the floors.
Hi. HNY! About 18 months ago 1 x 6 select t&g oak flooring was installed in my home. This was recently milled stock. The house is on raised brick piers. The soil under the house was covered with a heavy plastic which partially extends up each pier, one year ago. Plan is to resand the floors in late January. Is there a better way? Thanks.
Snyder,
I would make sure the wood has reached its Equilibrium Moisture Content before sanding. For more information, please visit http://www.nwfa.org.
Dishwasher leaked – My fault but after watching fir leaks when doing final install of dw in place I loosened the supply hose The slow drip wasn’t discovered until floor boards were cupping. Guessing it dripped for 2 weeks enough to when discovered there was a pint of water in crawl space. Cupping is such you almost need look or feel for it. No visible water staining on joists in crawl space. The cupped board area is maybe 4 x 4 foot area. mostly. We fixed leak. Ran fan over the top of the area for days. Set up a dehumidifier to try move air and dry out crawlspace. How long do we wait to see if the area increases or improves more? I believe it is improving but after a week I can feel barefooted. Not when wearing shoes. Visible when look for always. Hard to notice unless looking for. Thought comments appreciated greatly
Steve,
I have had experience with this first hand. It all depends on the time of year and how badly the floor was damaged. It doesn’t sound like its that bad indicating to me it should be flat within 6 months. Hope this helps.
Hey Jon hoping you could give me some much needed help. My apartment has sealed wood floors but it’s those that snap in. The other day as stupid as it’s gonna sound I fell asleep for only a few minutes less than 5 as I was running a bath but when I woke the tub over ran and my area rug was soaked. Of course I jumped up, turned off the water and opened up the drains and scrambled to get a mop towels bed covers anything to get the water. By the time I got rid of all the running water everywhere, I removed the area rugs (I have two as I live in a studio apartment). The one underneath my bed which was furthest from the entry of the water and got pretty wet doesn’t have a protective pad underneath it but the area rug that got hit by most of the water and because the pad underneath (which ironically enough I bought in order to protect the floors) was made of felt it absorbed a lot fo the water and cause some cupping in three areas. Everywhere else is fine, underneath my bed looks normal, and even the floor right in front of the bathroom is perfectly fine, it’s just the area where I had the protector pad and area and it’s only three raised sections. So here are my questionns I’m hoping you answer:
1) will this go away over time? I understand that it will definitely take weeks if not months for the moisture to dry out. The water and area rugs where there for all of ten minutes if that and nothing else is leaking.
2)I have replaced the now dry area rug but should I remove it and let it breath? Should I place a new protector pad?
3)Assuming it will dry over time, how much time would you guesstimate for one off time?
Just to give you an idea of the climate where am in, I stay on a 9th floor with 5ft height west facing windows that span 80% of wall so lots of sunlight and I’m a beach city in the southern California, so again lots of sun. Any helpful advice or diy tips would be suuuuuper appreciated. Thanks!
Jason,
My new 6” white oak floors look just like the picture in this web site.
I’m in the process of dehumidifying my crawl space.
How long does this take? My dehumidifier is showing 40 % . But, I’m guessing that’s the air and not the wood.
Am I looking at weeks? Or months? To go back to normal? Thanks
Leo,
Thanks for writing in. In a situation like this, there are too many variables to narrow down a time frame.
Hello,
Our new home was finished about 5 months ago. After about 2 months of living in the house I noticed the Red oak floors were cupping. My builder went under the house and didn’t notice anything. Two months later, the cupping was getting worse. Apparently there was inadequate ventilation and one section of the insulation was completely wet. That was removed and we just had a dehumidifier installed under the house. I just noticed a small area where about three floor boards are also crowning. How can I have both cupping and crowning in different spots at the same time? I’m so bummed since this is a brand new home. I’ve also been running a dehumidifier in the house and the relative humidity has been around 50 or 55. I live in South Carolina and we’ve had a very humid, wet summer. If the crowning doesn’t improve, is it possible to only sand and restain a small area? I really don’t want to have to sand my entire house. My floors are stained with Jacobean stain. How long should I wait before making a decision to sand? It is finally cooling off and we should start using our heater within the next month.
Thanks,
Heather
We installed hickory 5″ x 3/4 ” think floors in our Maine home. The floors are cupped and failing. We have a crawl space under the house. We sprayed the entire crawl space with the foam insulation before we installed the floors. The contractor that installed the floors did not deliver the flooring until the day before they installed the floor. We plan to replace these floors. The floors are only 5 years old. My question is what can we do to prevent this from happening again. Should we spray foam insulation the actual subfloor under the house? We did a reading on moisture under the house and it is dry. Where could moisture be coming from? It showed no moisture with a moisture reader. We had a company come out and test the subfloor. They got the same results. No moisture. Could it be that the contractor didn’t have the wood acclimate to the space? We are fearful that this could happen again. We have wood floors upstairs and have had no issues up there. We live where we have ledges all around us. The house has concrete stem walls. Remember we sprayed the entire floor with the foam. Please help us. How long does the wood flooring need to be in the house before it can be installed? Does the flooring need to be out of the packaging? We also close our home in the winter. We live in Florida in the winter. We keep our heat set on 50 degrees while we’re gone. We have tried dehumidifier under the house in the spring. Everything we have done has not worked. Help!
Helen,
It’s possible that it wasn’t acclimated properly. Acclimation is when the flooring had reached the conditional moisture context where it will be installed. Wood is gyroscopic and will lose or gain moisture depending on its conditions.
It may be best to visit http://www.nwfa.org to get installation guidelines for your next floor. Hope this helps.
We installed a new ac 3 1/2 ton 2 phase variable speed unit with heat pump and has a dehumidifier. We live in a pier and beam house in East Texas. 3 months after installing the ac our laminate flooring has started cupping and paneled walls buckling we keep ac around 71 and moisture is usually around 60 how can we correct this problem when we redo our floor should the AC contractor known this could of caused this. Floors are 7 years old
Christy,
It’s hard to tell what is happening with your laminate floor without gathering more information. It may be best to contact NWFA.org to get an independent inspector to review your floor and determine the cause. I hope this helps.
Hello Mr Spangler,
During the first week of December 2019, we installed new Cumaru wood flooring throughout the house.Our house is divided on 2 levels, divided by a mini staircase. The part where the kitchen, dining room and living room are located is a concrete slab.
The installer we chose for the installation had no choice but to lay the floor in this section on plywood sheets of different sizes (3/8 and 5/8), nailed and glued.He installed the plywood on Monday, and the floor over it the next day. Everything seemed fine until Christmas (3 weeks later) when we noticed that the floor was cupping in the section where the plywood had been installed, but not in the rest of the house where the flooring was installed on the already existing plywood.
At the seller’s request, an NWFA inspector recently came to our house to do several tests and came to the conclusion that the humidity level was high in our house. We live in Canada and our house is normally heated with a heat pump in winter and even a wood fireplace that we use every day. We have some doubts about the inspector’s honesty because his report makes no mention of our comments on the installation. But anyway, what happened is that the plywood sheets the installer (40 of them) used by the installer stayed outside at least during 2 weeks prior the installation, and the day they were installed (very cold and icy day), they were pretty wet and frozen. Once the sheets were definitly installed, he placed some roll of white paper on top and then the flooring. I don’t know if this is the proper way to install new flooring, but after reading your interesting article, I’m wondering if the wet plywood sheets could be the culprit of this whole mess, and that maybe, the installer should have waited for a couple of days before installing the flooring. Please, what do you think ?
Thank you for your imput.
Chris
Chris:
Thanks for the question and sorry for the problems. Your theory could be true, but it’s not necessarily exclusive. Using a wood stove can decrease the humidity in the air and can dry the top of the wood out causing dry cupping ALSO, the plywood could have been excessively wet and this would exacerbate this issue. Knowing what the concrete, plywood, and finished wood floor moisture content/condition where, prior to installation, would give a solid baseline for where the floor components started and should have all been measured prior to installation. This information would then be compared to current conditions, along with other things, to see what, if any, conditions have changed. I would hope all of these things (then some) led the inspector to his/her conclusion.. I hope this helps.
Hi Jason,
I installed 4 inch, 3/4 red oak hardwood floors in January in my addition. They were perfect. In May, I cemented around the surround exterior of the addition. In June, I began to notice cupping throughout. 1) Do you know if exterior moisture from cementing can get under your foundation and create cupping? 2) Can 1/4 inch expansion gap have a compounding effect on cupping? I live in Los Angeles where we don’t get adverse humidity. I am using a dehumidifier which has lessened its affect. Thank you.
Jose:
Thanks for the question.
1) This is possible, but I would expect to see more localized issues around the interior perimeter of the floor.
2) ¼’ expansion isn’t enough for most wood floors, especially in larger spaces, and could be adding to the issue.
You have many things that may be contributing to this issue:
1) Did you moisture test the concrete slab prior to the installation of the wood? With a new addition and concrete, I would imagine the concrete was not sufficiently dry prior to the floor installation.
2) What was the moisture content of the wood prior to install to installation? Where those measurements appropriate for the living conditions within the addition?
In the end, the cupping is being caused by a moisture imbalance in the thickness of wood. This moisture imbalance could be from the bottom or it can be drying out from the top. Knowing the answers to the above question may help lead to the reason.
Hi Jason,
We had new white oak hardwood floors installed in our brand new ranch one year ago over our crawl space. Almost immediately we noticed cupping in certain rooms and some hallways. The builder has said that there is absolutely no moisture in the crawl space that would have caused the cupping. Now that a year has passed and no settling has taken place to resolve this situation are there any options short of completely replacing the floors that you could suggest. It’s my contention that maybe the wood hadn’t acclimated to the environment before it was installed. Also, there are plenty of rooms that are just fine. Thank you.
John:
Thanks for the questions and sorry for the problems. There could be a few different issues potentially causing this problem and it might not just be one by itself. It could be a ventilation issue under the house, fluctuating relative humidity in the crawlspace and/or home, improper acclimation of the floor prior to installation, etc.. I would have a certified wood flooring inspector come out and evaluate the situation because once they give their opinion on cause, you can make a better decision on remedy. Look on http://www.nwfa.org for a certified inspector.
Hi Jason,
We built our home over 30 years ago. We had carpet and linoleum throughout until 2 years ago. We had oak prefinished 3/8 boards installed. We live in middle Tennessee with cool wet winters and hot humid summers. We noticed cupping over the whole house last summer. We put new heavy duty plastic in the crawl space and were told by the flooring company to close the foundation vents. The cupping still remained until the fall/winter and the floors went back the way they should be. Well it’s summer again and the whole house has cupped again. What do you recommend? Thanks so much for any advice you can give us. We are stumped!
Thanks for the questions. I can make some assumptions based on what you explain. First, obviously you have some seasonal condition changes going on. Changes in the relative humidity and temperature in the occupied space, the crawlspace, or both. It seems you have taken one good step in placing heavy duty plastic in the crawl space. Now, whether closing the vents was good, I have my doubts. Most of the time if the crawlspace humidity is an issue and there is enough ventilation, closing off some vents and utilizing some type of power vents to increase circulation and pull humid air out of the space is desired. But, we don’t know if this is a correct assumption because we don’t know what the conditions were/are, relative humidity and temperature, in the crawl space. The same can be said for the conditions in the occupied space. Are you using air conditioning? Is this drying out the air? Are the summer conditions in this space different that the winter conditions? Probably the best way to find this out is with a thermo-hygrometer of some type. You can either get one and take static readings in these space’s during the seasonal changes with something like this https://www.wagnermeters.com/shop/th-200-thermo-hygrometer/ or you can place something like this https://www.wagnermeters.com/shop/smart-logger/ in each space and it will log data, over time, so you can download and compare the information between seasons. Typically wood’s “happy place” is between 30-50% relative humidity, so when conditions change, so does the wood. Good luck.
Dear Jason, thank you for the helpful article, I would really appreciate some advice from you. The living room of this house has 140 year old original 4″ wide 3/4″ thick wood floors underneath the wall to wall carpet, half of the wood planks are super water damaged, the other half are in good condition. Some water damaged wood planks have about 1/4″-1/2″ difference in plank height due to cupping… All planks have about 1/2″ gap in between due to shrinkage over time.
Is it possible to put new wood over the entire living room? Am I better off fixing half of the floor that is water damaged, is that an expensive process? Thank you!
Lucy:
Thanks for the question. First, it wouldn’t usually be recommended to install wood over a wood floor, especially one that has known damage. I would have a wood flooring contractor, one that has experience in site sand and finish work, come over and evaluate the existing floor and give you options. You would be surprised what an expert can do to a floor that normal people, like you and me, might think is unrepairable
Hello Jason,
I purchased a 15 year old townhouse in SW Colorado in March 2020. Hardwood floors are original to the property and are installed in living area which is over the lower level insulated and heated garage. The hardwood floors had a few nicks and scratches at time of purchase but were definitely flat. Evening of June 1 or morning of June 2 a pipe burst in living area. Water covered floor, was flowing out balcony of living area and flooded lower level garage. I hired a restoration company that were onsite by afternoon of June 2. So water sat on hardwood floor for no more than 24 hours. Restoration company got to work immediately removing water, set up fans, dehumidifiers. Moisture readings were collected throughout the living area and were 99% everywhere. Restoration company also removed baseboards, drilled holes in walls to blow hot air into space behind dry wall. All drywall in garage was soaking wet and was removed almost immediately. Same with insulation in garage. Removal of drywall from garage ceiling allowed drying of living area subfloor from below. I think restoration company did everything right. It has now been six days since flooding and there are clear signs of cupping of every plank of the entire hardwood floor in living area. In addition, there are small cracks between planks indicating water seeped into planks and was not simply sitting on surface of hardwood floor. One employee of Restoration firm told me floor does not need to be replaced since cupped floor will eventually settle back down into place. Then he said even if it doesn’t settle down it can be easily repaired simply by sanding and refinishing floor and it looked like floor needed refinishing anyway. But this is not what I learned from reading several websites including yours. Indeed I think sanding a cupped floor can cause more damage down the road. My question is given the extent of damage throughout the entire floor is it better to replace entire floor now or just sand and refinish now and hope it won’t get worse? Any Professional insight you can provide will be greatly appreciated. Thanks so much
Linda:
Thanks for the questions and sorry for the issues you are having. Especially this early in this process, I wouldn’t even entertain sanding and refinishing. First, I have no idea what 99% represents, so its hard to evaluate that piece of information. What you really need to know is how wet is the wood floor (moisture content %), how wet is the subfloor, and how does that compare to what that wood would have been prior to the broken pipe. I agree, it sounds like the restoration company is being thorough, but how are they evaluating if they are having impact on the floor. You could have (and probably do have) moisture under the floor and on top of the subfloor. This will take time to dry and you won’t know the effect on the floor until this is gone. It will take time. Good luck.
thanks so much! appreciate your response.
Hello,
We extended our breakfast nook area last year. Our orginal home is on a crawl space but the extension was done on a concrete slab. the contractor put down hardwood in the new area to match the existing floors. Right afterthe job was done we saw some cupping in just the new extension. We called our contractor & he said that happens sometimes due to moisture in the concrete floor & all we need to do is run a de humidifier in that area. He said sanding will not help. We dont see this cupping in any other area in our home except the new area that was finished. what should we do? the contractor has used polyurethane glue to put down the hardwood floors on the slab. Is it due to installation issues? or may be the concrete floor was not cured properly? pls suggest
thanks so much!
Jogita:
Sorry for the issues with your floor. The cupping is due to some type of moisture imbalance in the wood flooring itself. This imbalance could either be moisture from the concrete, environmental conditions in the space being to “dry” and drying out the top of the wood, and/or a wood floor that wasn’t properly acclimated to the environment prior to installation. Unfortunately, I can answer which of these is the culprit. There should have been moisture testing done on the concrete prior to installation to guide installation and there should have been moisture testing done on the wood prior to installation to ensure it was properly acclimated. The contractor is correct that that sanding will not help, it will potentially make it worse. In order to get an unbiased opinion of the floor, it may be best to look for a certified wood flooring inspector in your area at http://www.nwfa.org. Good luck.
We have cupping on our hardwood floors just around the dishwasher. There was a leak in the pipes that was minor and we didn’t notice the cupping till later after we got the leak fixed. We live in a condo and was wondering what the best way to resolve the cupping would be?
Bshah:
Thanks for the question. Depending on how bad the cupping is, left alone with no additional water, it may relax to an acceptable level. If it doesn’t return to an acceptable level, depending on the type of product you may be able to resand and finish the section. Worst case you will need to do a replacement in that section. Good luck.
Hi Jason,
When I moved into my house there was a ceramic tile floor over mortar and lath with roofing paper oner oak floors in the foyer. I stripped it back to the oak. The oak was cupped, so I left it exposed for a couple of years. Most of the planks flattened out but there are still issues. The planks have some shrinkage and a few of them are still cupped. I was thinking that the mortar bed dehydrated the wood. I was told to steam the floor to correct the problem but, am looking to see if this is the right direction or what would be best.
Thanks, Jerry Ickles
Jerry:
Thanks for the question. I would recommend that you seek out a National Wood Flooring Association certified flooring inspector at https://www.woodfloors.org/find-a-professional.aspx to evaluate and give you specific recommendations. Good luck.
Help! I live on Lake Sinclair in middle Ga where we are having tons of rain. I have lived here with no problems with me oak floors for 4 years but did have some fungus. Last year I spent $5000 installing n Atmox dehumidifier in my crawl space with top rate plastic. This week I noticed cupping in only a retangular area about 5ft by 15 ft. I looked under the house. Things looked dry except for a small puddle of water near the hot water heater. What do you think? Who do I call?? Plumber? Electrician??
Donna:
Thanks for the question. If it were my house, based on what you said, I would call a plumber to see if you can narrow down the cause of the puddle. Good luck.
Thank you. I am on it. Serv Pro was in our home for 5 days with 6 fans and dehumidifier. When they left today…. they said the floors were toast. They assured me they would send a copy of their findings. The floor has lifted and everyday the lifting is a little larger. I am calling Certified NWFA today!
Many Thanks – we will get someone to look at it. What do you mean by “grown” ??? I see it has grown UP (LOL) but any thoughts on why it has done so? Feel free to use pics! Cheers, Anne.
Anne:
When I say “grown”, the overall dimensions of the floor has grown due to moisture and this may be why you are seeing the lifting of your floor. In extreme situations where there isn’t room left for flooring expansion and moisture conditions increase in a floor, the entire floor can grow so much it can actually move walls. Hope this helps.
Jason:
I have Brazillian teak 3/8 thick solid wood floor, glued to slab foundation. They have been in my home 11 years. We came home from the gym last week to find a leak in the hot water tank. Most of the water was carried out into the garage, however 10 ft by 5 feet was completely soaked. Insurance came to the house the following day but waited 4 more days to decide to dry the floors out. The floor have starting cupping and pulled away from the slab. Some board have crack. Because these are solid wood teak our insurance company feel they can be salvaged. Is that possible when boards are split and crack along with cupping. We are running 6 fans in the area that was soaked as well as a dehumidifier brought in by Serv Pro. I need help with how to deal with insurance Company.
Barbara:
Thanks for the question. Depending on the severity of what you describe, yes, the boards may be able to be salvaged. I would contact the National Wood Flooring Association at http://www.nwfa.org and find a certified wood flooring inspector in your area to evaluate the specific situation. They should be able to give you the information you need to deal with the insurance company. Good luck.
Hello Jason … Great info here! We are stumped at our dramatic floor situation. Our cottage flooring as all pine (rather wide boards). All recently refinished. They sit on a subfloor with a crawl space underneath. Heating is very low in the house during the winter (approx 10 degrees – subfloor is about 5 or 6 degrees). In only ONE place in the whole house we are getting substantial crowning of the floor boards. They have risen right up off the subfloor and look as though they are about to pop any second! We have checked the humidity levels in the sub floor (higher than above ground – maybe a difference of 7 degrees) .. and we see NO indication of water or moisture below the flooring (checked below and saw nothing). Confused as to why the flooring would expand so much during winter ????!!!! The crowning occurs below a window, and there is an electric baseboard heater there too (we have never turned it on – off at the breaker) but the crowning seems to be happening in the same space as these two elements (window / baseboard). No sign of ice or water though …. but the floorboards are clear off the subfloor! Thoughts? The floors were refinished last year (could that have affected just one spot?), could it be just one spot was badly installed? It is a new place for us .. so we are baffled … here are some pics for you – would love your thoughts on the subject.
https://1drv.ms/u/s!Ag-aQU8wF_D_gzF8Ivj26frARZsr?e=crx01Y
Many Thanks!
Anne:
Thanks for the question and sorry for the issue. The obvious thing is that the floor has “grown”. Keep in mind, the issue may not necessarily be in this area, this may just be the weakest link in the floor and where the issue manifested. I would reach out to http://www.nwfa.org and find a certified inspection professional in your area to take a look at the entire floor. Good luck.
P.S. If it’s okay with you, may we have permission to use your photos in marketing materials?
Jason,
Thank you for your response. The engineered wood floors are installed on a raised pier and beam foundation. The crawl space is vented and dry. The bottom of the subfloor(1 1/8″) is insulated with closed-cell foam. The joists are not insulated. It looks like the floor installer used 15 lb felt paper for the vapor barrier. It also looks like the installer did not follow the nailing guidelines. The planks are not nailed within 2 inches of each end or every 4-6 inches. The rows were not always staggered 8-10″ row to row for the 5″ wide planks. So far the peaking is slight throughout the floor. Right now in Houston the weather has been cool and dry. Would you expect to see more distortion in the floor in spring and summer when the weather is more humid and wet?
Molly,
It’s hard to say whether you will see more peaking in the spring. Typically during spring and summer, you have more humidity causing all wood to absorb moisture. This includes everything wood in your home. My suggestion would be to have an independent inspector come to your home and evaluate the situation. He will determine the cause of the peaking and provide a written, detailed report for you to follow up with.
I hope this helps.
Jason
Hey Jason, we live in NW Florida and had engineered hardwood install three years ago over a cement slab in our great room. Within a year after the installation about a half dozen planks have cupped. The installer said it was moisture under the slab and eventually every plank would start to cup. The installer suggested we have the flooring removed, place a moisture barrier over the slab and have a new floor installed. Seriously!
Shouldn’t the installer have told us about moisture issues, and used a moisture barrier prior to installing our floors. I’m contemplating legal action. What are your thoughts? Thanks, Tom
Tom,
Thanks for reaching out. We understand your frustration. I have added some information from NWFA that should help out. National Wood Flooring Association (www.NWFA.org) is the standard for which ALL installations of hardwood flooring must follow. Please see below the information from NWFA. I hope this information is helpful, best of luck!
Engineered Wood Flooring
A. Prior to delivery of the wood flooring, check and record the jobsite ambient conditions and the subfloor moisture to ensure they coincide with the wood flooring requirements that have been selected.
B. Upon delivery of the flooring to the jobsite, recheck and record the temperature and relative humidity in the space receiving the wood floor. The temperature and humidity must be within the manufacturer’s requirements.
C. Upon delivery of the flooring to the jobsite, recheck and record the MC of the subfloor. Check with your moisture meter manufacturer to determine the correct setting on your meter for the wood subfloor being tested. 1. Take MC readings of the wood subflooring at a minimum of 20 test locations per 1,000 square feet, and an additional 4 readings per 100 square feet thereafter, and average the results. In general, more readings will result in a more accurate average. Any unusually high or low moisture readings should be isolated and addressed individually. Record, date, photograph, and document all results. 2. The average of the wood subfloor readings should coincide with the manufacturer required temperature and humidity levels in the facility receiving wood flooring. (Refer to the MC chart in Part I of this chapter.) 3. Concrete subfloors must be moisture tested, and adequate moisture control systems should be in place prior to installation of any engineered wood floor. 4. Any unusually high or low subfloor moisture readings should be isolated and addressed prior to wood floor installation.
D. Follow the flooring manufacturer’s moisture testing, acclimation, installation, and maintenance instructions to retain all warranty coverage.
E. When the wood flooring is to the expected in-use (e.g., normal living) and manufacturer’s required ambient conditions within the facility, and this coincides with the subfloor moisture conditions, and these conditions are being maintained, the flooring may be installed immediately.
I have a newly installed engineered oak wood floor throughout the first floor of our new construction home. The ends of the planks are lifting-edge lift? The floor was installed about a month before the HVAC was installed or running. The peaks are 1/8″ or under in certain areas. The floor inspector came today and read about 10% on the veneer (3mm) part of the floor and 18&20% on the 2 subfloor tests. My question is if it is possible for the floors to eventually flatten out? Is it possible for the subfloor to dry out? There are 2 coats of polyurethane on the floors.
Molly,
Thank you for the questions. Is this an engineered, sanded and finished floor on wood subfloor, or concrete? I will assume Engineered sand and finish floor. What’s happening with your floor is called “Endlift/Ski.” It’s a condition where the ends of installed engineered wood flooring boards deviate from the flat plane and appear raised or curved upward. There are several reasons this happens:
• Flooring incompatible with the environment in which it is installed.
• Engineered flooring that has experienced an increase in moisture, where the core material running perpendicular to the face of the board swells at a different rate and in a different direction than the adjoining layers, forcing the ends of the material to lift, which can then telegraph to the surface of the plank.
• Inadequate or inoperable HVAC systems resulting in elevated humidity levels. (See Greenhouse Effect.)
• Improperly selected, improperly installed, or improperly applied moisture control systems (vapor retarders) that do not provide adequate protection from below the floor.
(Again, assuming Wood Subfloor and crawl space)
The most critical aspect of this installation is for the moisture content (MC) to reach an equilibrium with the wood flooring, humidity, and subfloor MC. This is also known as the “Greenhouse Effect.”
Once the subfloor, wood flooring, and humidity levels all equalize, then you can repair the floor by replacing them, or re-sand and finish the affected planks. It’s very likely they will not return to normal.
It’s very important to make sure no repairs are done until the EMC (Equilibrium Moisture Content) has stabilized. The moisture content of the subfloor is very high based on your information. I would definitely find out what’s causing that. If its “green” wood subfloor and there is no cause for the moisture at your residence, the subfloor should dry out as long as you have proper ventilation under the home. I would make sure there are no leaks under the house. Also, make sure that there is black plastic covering the crawl space.
Hope this helps.
Hi I have solid pine 22 yr old floor. I had a sink overflow and water went about 10×10 feet area. It prob sat for 15mins. I then got rid of water and ran 2 dehumidifiers and have wood stove on for 4 days. The floor is going back down but isn’t 100% flat yet. It is winter and when I leave in 3 days there’s will be no heat as it’s a seasonal cottage and we drain it and turn heat off. Will the floor continue to dry or will the cold temps make it worse. Thx for any info. Sue
Hello Jason,
My hardwood floors are newly installed in the upstairs throughout. Downstairs half of the floor was hardwood and the other half carpeted so we converted It all to hardwood. 3 months after the installation and cupping is occurring to all new hardwood floors. It is not existing in the old hardwood that was already there downstairs. I spent over $17K on my flooring and now I have cupping to all new hardwood. What can be done?! Thanks!
JK
John:
Thanks for the question and sorry for the issues with your new floor. I guess the first thing to do would be to get the installer involved to give you an explanation and a course of action to remedy the situation. If that remedy doesn’t meet your expectations, I would look for a certified wood flooring inspector at http://www.nwfa.org and have them evaluate the situation.