Hardwood Floor Moisture Problems: Learn the Warning Signs

Caution: Wet Floor

Wood’s moisture content (MC), the amount of moisture in wood, must be managed to achieve optimum flooring strength and durability. When relative humidity (RH) rises, wood absorbs moisture from the air. When RH falls, wood emits moisture back into the air. This natural process gives wood its strength and beauty, but excessive MC can cause many possible problems with your wood floors.

Visible Signs

Some moisture-related problems are visible to the discerning eye. Primarily, wood flooring problems can occur when the wood expands and contracts. This “wood movement” occurs naturally according to seasonal shifts or when ambient RH levels change in the home. These changes can also present a less-than-desirable change in the appearance of your wood flooring.

Wood Floor ProblemCracks and Separations between Boards: When homes are heated in the winter, RH levels can plummet, boards can shrink, and spaces appear between the boards as the wood loses MC. Some of these variations are seasonal and will close up on their own when the weather (and related RH) changes and the MC of the air increases. Monitoring the room’s temperature and RH level, then taking corrective action, can also minimize seasonal shifts in the wood floor. As an example, homeowners can add moisture to the air during dry winter months by installing a humidifier in the furnace.

Cupping: This is when the edges of a board are higher than its center, due to moisture which causes the wood to expand. This can occur after water spills onto the floor and is absorbed by the wood. However, usually high RH is the culprit. As the wood expands, compression can result as the boards are crushed together, deforming the boards at the edges. Cupping is caused by a moisture imbalance through the thickness of the wood. The wood is wetter on the bottom of the board than on the top surface, which dries quicker than the bottom. Cupping most often appears after the floor has been installed and may or may not be an installation issue.

Crowning: The opposite of cupping, crowning occurs when a board’s center is higher than its edges. A common cause is moisture exposure or imbalance. If the surface of the floor is left exposed to water or left in humid conditions for an extended period of time, the moisture can saturate the wood flooring and cause crowning. Another cause is that the floor was previously cupping, but was sanded before the MC returned back to its normal state. In this case, the floor should be given time to dry before sanding. The sanding process can cause the raised edges of the board to flatten while lifting up the middle of the board if the floor is sanded while the boards remain cupped and moisture is still present.

Buckling: This is the most extreme reaction to moisture in a hardwood floor. This occurs when the wood flooring actually pulls up from the subfloor, lifting several inches in one or more places. Fortunately, this is not a common occurrence. Buckling happens most often after a floor has been flooded for an extended period of time. If caught early, spot repair and replacement may be possible. Once the standing water is removed, several boards can be taken up from the floor so that the air can circulate across and below the floor. Once the floor has dried to a more stable moisture level, repairs can usually be made.

Invisible Moisture Problems

Some moisture dynamics can occur beneath a flooring substrate with equally devastating possible consequences for wood flooring applications.

Wood SubfloorWood Subfloors: Determining MC is an essential part of quality control within the flooring installation process. Flooring installers must know the MC of the subfloor as well as of the wood flooring. Test for moisture at several locations in the room- a minimum of 20 per 1,000 square feet- and average the results. You should make sure to measure all exterior and plumbing walls. In most regions, a dry subfloor that is ready to work has an MC of 12% or less. If you record high MC readings, do not proceed with the installation until the origin of the moisture is identified and all moisture related problems are remedied.

Concrete Subfloors: All types of flooring are susceptible to failure if moisture conditions are not properly monitored and maintained. When the subfloor is concrete, a moisture problem may begin long before the flooring is installed. If the slab has not been properly dried, moisture problems are almost guaranteed with wood flooring applications. Accurate moisture testing is critical for any concrete slab. ASTM International has provided several standards for testing moisture with two different test methods before installing flooring over a concrete slab: in situ probes per ASTM F2170 and calcium chloride testing per ASTM F1869. The best indicator is RH testing using in situ probes per ASTM F2170.

Leaks or Water Intrusion: Any moisture that comes from below a subfloor or gets between the subfloor and the flooring can cause problems over time. Leaking appliances, ground water intrusion through a perforated vapor barrier, condensation, and even moisture from a concrete subfloor that had not completely dried can introduce moisture to your flooring equation. Also from the outdoors, it might be the terrain of the home’s lot with rain and runoff not moving away from the foundation that can cause moisture-related problems with the wood flooring over time.

The Antidote

The best cure is to accurately measure and assess the moisture in the subfloors previous to wood flooring installation and also measure the MC of the wood flooring before, during, and after the flooring installation.

A wood moisture meter helps wood flooring lovers to navigate naturally-occurring seasonal MC changes on a regular basis. Pinless moisture meters for wood can measure the MC below the wood surface without doing any damage to the wood flooring. Wagner Meters uses pin-less technology to non-invasively measure the wood flooring’s MC, which can help accurately pinpoint possible problem areas for repair or remediation. Wagner Meters manufacture moisture meters for wood that can measure hardwoods, softwoods, and exotic wood species, and also manufactures specialty meters for wood finish applications. Wagner Meters also manufactures RH in situ probes for testing concrete slab subfloors.

When MC management makes all the difference, using a Wagner Meters wood moisture meter is an invaluable way to effectively resolve the warning signs on wood floors.

Take a look at our moisture meters here.

The following two tabs change content below.

Jason Spangler

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.


  1. Peter Barton says:

    Hi, I have a hardwood floor that seems squishy where the living room transitions into the hallway. I pulled the suspended ceiling and insulation from the basement cueing and didn’t see anything noticeably wrong. Any ideas what or where we should be looking for?

  2. jason Spangler says:


    Great question. Unfortunately, I have a few questions prior to being able to give my opinion:

    1) Is this solid hardwood or engineered?
    2) Are we dealing with any transition pieces? If not, how long of a “run” of wood do we have without transition?
    3) Is the flooring installation direct glue down or nailed?


  3. Zachary says:

    My floorboards are developing cracks/holes in the middle of the boards themselves; which seem to follow the pattern of the wood. Some say it is a natural process( the house is about 5 years old), but I was wondering if more polish, olive oil or other method could slow this process down?

  4. charles balasalle says:

    my first floor hallway floors,have signs of moisture on top of the hardwood floor boards>
    floor measurements are 3×18 most of the area are away from the front door door
    I do have central air. there is no cupping or buckling. I only have water./moisture satins.
    which i can feel with my hands. should i purchase a moisture meter ? would this help me find the cause or should i have a floor contractor look at my floor?

    • Jason Spangler says:


      I think in this instance, unless you were going to be using the meter on an ongoing basis, your money would be better spent either bringing in a wood flooring inspector or a wood flooring contractor to lend their professional opinion. NWFA.org can help you find qualified people to help.

  5. Kate Bristow says:

    I have cracks and separations between boards. Can I use a liquid cleaner?

    • Jason Spangler says:

      While you can use a liquid cleaner, I would recommend researching different types of products and determine if there is a specific one that may help address your issues.

  6. Roy Dreibelbis says:

    I had 3/4 inch (hard wood) flooring install a year ago over 3/4 inch sub-floor.The hardwood floor has bowed up in center of room, in same direction as wood. This goes from wall to wall of room. What is cause and how can it be repaired?

    • Jason Spangler says:

      Is the bow in each board width of the floor or is it just one big bow, where the entire section of floor is lifting off the subfloor?

  7. Fran Zwicky says:

    i just had new 3/4 quarter solid oak floors put in and am not happy with the installation. There are some gaps, chips in wood and one board is cracked. Some boards do not meet and have a rough edge. I am sick from this whole experience and don’t know what to do.

    • Jason Spangler says:

      Hi Fran,

      Talk with the installer to see if you can come up with a solution. If that doesn’t work, having an NWFA certified inspector come out and look at the floor can help.

  8. Connie Hargrave says:

    My new hardwood floors were installed about 2months apart (awaiting wood availability-carribean pine). They were left unfinished. Installer supposedly sanded first area and only slightly sanded second area. There are grout marks where bathroom was remodeled and shoe scuffs and now cracks developing between the boards and worst of all I have squeaky floors and flooring is butting against wall in many areas. Installer is arrogant and very difficult to talk to and becomes defensive and storms out of my house and raises his voice at me. He has been paid for all but about 6%. He refuses to use any other stain but Minwax.

  9. Teresa says:

    Bought our house about a month ago, guess the previous owners installed their own hardwood floors. In the front doorway and one other place in my house the flooring is rising up? I saw that one problem could be moisture getting into the wood. What can we do to fix it?

    • Jason Spangler says:

      This could be the result of inconsistent ambient conditions, improper acclimation, or many other moisture related problems. These types of problems can be fixed, but you really need a professional to diagnose the problem to come up with a remedy. I would attempt to identify a NWFA certified wood flooring inspector/installer to properly help you with this issue. The NWFA website is NWFA.org. I hope this helps.

  10. Amy Wouda says:

    We recently renovated a 20 year old house the was built slab on grade. The house had parquet floors that we covered with a thick underlay and then laminate flooring. This work was done in May and in September the laminate started cupping. We were worried there was not enough space left along walls that the laminate butted into. However after removing the laminate flooring the problem actually lies in the old parquet floor. It has cupped terribly. It is the original flooring that was installed 20 years ago. I think now the laminate and parquet will both have to be ripped up, however what is the best type of flooring to lay down to not have this problem occur again?

  11. Carlos Jimenez says:

    Mysterious Water stains in the middle of the living room. No plumbing near the vicinity in the crawl space beneath. No sense of humidity in the crawl space. New Roof was installed but when it rains the floor in the middle of the room gets wet.. When it does not rain all the wood seems to dry up except 1 piece which remains to always be wet. I really need some guidance on how this can be happening? House is under renovation and I’m looking into refinishing the floors as the last step of the reno.
    Carlos J.
    Miami, FL

    • Ron Smith says:

      Hi Carlos,

      I’d suggest trying to locate an ASHI-certified home inspector in your region to take a look at this and determine the source.

  12. Casey says:

    I have a condo with its original parquet floors from the late 80s/early 90s. The floor has started lifting up in places. I’m relatively certain it isn’t a moisture issue, as I had an inspection done upon move in 12 months ago, and no moisture detected. I’ve also felt around the area (it is near front door and laundry area) and can’t find moisture. I think it’s a combination of AGE and also FORCE/STRESS. What I mean by FORCE is- edge of floor comes up against the laundry area, and when the old washer is unbalanced it jolts around a lot. At times is pushes up against the parquet edge- I believe over time this is pushing the floor up. My question: is there a quick or temporary fix, other than new floors, for this? Screws or nails? Getting some new ashes under there? THANK YOU!!!

  13. Cotton Mendenhall says:

    I have obvious water penetration in my living area with my hardwoods buckled on a slab foundation. I live in Dallas. Do you have a recommendation on who I can call to check it out in Dallas?

    • Jason Spangler says:


      Thanks for the question. If you are looking for someone to measure the moisture levels in your concrete, here is one suggestion:

      Terracon Consultants, Inc.  
      Engineering Consultant
      Address: 8901 John W. Carpenter Fwy #100, Dallas, TX 75247
      Phone: (214) 630-1010

      I hope this helps.


  14. Nancy LeBoeuf says:

    My 90 year old house is 3 ft off the ground. My wood floors in the living room are buckling in the middle of the room. We have had 2 weeks of rain non stop. What can you recommend? We have a dehumidifier in the room but nothing is working. Help

    • Jason Spangler says:


      Thanks for the question. Unfortunately, based on the information provided, it is hard to say if it is the conditions in the house or from under the house causing the problems. I would go onto the NWFA.org (National Wood Flooring Association) website and call their hotline. They may be able to walk you through some of the questions and either give you solutions or recommend resources to look at the problem closer.

  15. Rob says:

    I’m in the process of installing hardwood floors on my sub flooring. I just noticed that in the center of the room there is a lift of the wood flooring. The wood flooring looks to be completely intact to subfloor. It looks like there’s a wave in the flooring. I went under the house and noticed that in the lifted area – – there’s a support beam directly in that area. My house is 25 years old. Have I done something wrong while installing the hardwood floor, or is the sub floor uneven? The hardwood is in the house one week prior to the install.

    • Jason Spangler says:

      Rob, it’s hard to say for sure based on the information, but I would be leaning towards the flatness of the subfloor. I hope this helps.

  16. Lisa Dodge says:

    We are refinishing the original wood floor in our house. There is a large area where a dog has repeatedly urinated. We dried the area with heat lamps and fans, finished the floor and 2 days after finishing the floor in that area was ruined with a bunch of moisture that came thru the wood. How can we fix this

  17. Bob Teachout says:

    My wife and I purchased a new condo with concrete floors, the builder never self leveled the floor and now there are several spots where you step you can feel the floor move. It’s engineered hand scraped hardwood. Also the builder got ceramic tile dust all over the floor and in the wood grain, when they tried to clean it up they just mopped it into all the grain and seams and it’s as hard as concrete. He wants to put stain over the entire floor, we let him try one room and in less than 3 months the white dust is coming back through. Are any of theses problems something you have experience with?

    Bob T

    • Jason Spangler says:


      Thanks for the question. I can’t say that we have had direct experience with this specific problem, but it seems to me the answers could be obtained by getting the right person (independent) to look at the job. Being that it is wood, I would contact NWFA at http://www.NWFA.org and look through their list of certified inspectors in your area. I hope this helps.


  18. Jeremy Brown says:

    We have some cheap engineered flooring in our kitchen. We just noticed a couple days ago an area about 15-20sf that is mostly in front of the sink and dishwasher that is slightly cupping and splitting on many of the boards. Here’s the mysterious part – after pulling out the dishwasher and inspecting it (and the area in which is rests) and fully inspecting the sink and and cabinet underneath – everything there is perfectly dry. There is no evidence of a leak from the ceiling either. Nobody spilled anything (It’s just my wife and our two children and we surely would have seen and cleaned up a spill). And….the flooring up against the typical sources of a leak is actually unaffected anyway. In other words – it doesn’t seem to be traceable back to any one source. We know the flooring needs replaced, but not without first locating the source of the problem. BAFFLED.

    • Jason Spangler says:


      It could be water from dishes, as you are loading the dishwasher, getting on the floor. Little bits of water over time. If this is a floor over a crawlspace, there could be something different in that area like penetrations in the vapor retarder/no retarder, moisture accumulation in that area, ventilation, etc. Also, with the cupping and splitting, it could be a “dry cup” which means the ambient conditions are too dry. This can affect small areas of flooring. I would say that in the course of replacing the floor you enlist a knowledgeable installer to explain/help you identify the issue(s) and ways to avoid in the future.



  19. C clark says:

    Our house was built last year. We have a cement floor, wall crawl space . On the main floor we immediately noticed low spots in several areas, floor felt soft or hollow almost sinking – not solid underneath (sorry don’t know how to explain better) , builder said that high spots were actually the problem so added extra support underneath in crawl space, I don’t feel an improvement. Also have many loud popping and cracking noises that are worsening with time.
    Builder replaced one area in family room near fireplace explaining the glue had not adhered well. I believe we have engineered hardwood. Any input would be greatly appreciated!

    Thank you.

    • Jason Spangler says:


      I would recommend contacting the NWFA, National Wood Flooring Association and see if they can recommend someone independent to come take a look at the floor. This way, if there is something wrong with the floor, you can have very specific, unbiased information to provide to the contractor for resolution. I hope this helps.


  20. Brian says:

    I recently bought an used house (20 years old) and after removing the carpet in the living room, I found along one particular seam of the subfloor (I think it’s plywood) the edges are cupping. It runs from wall to wall but is more prominent on one side. There is a larger than usual gap along this seam and although there are screws and nails running down the seam on both sides, it didn’t prevent that seam from rising up like a lump. It’s almost a quarter inch higher at the peak than the ground level. I’m wondering what caused this and if I need to look out for something in the future. How do I fix it? I want to put laminate on this floor and I was thinking to just sand it down to make it level.

    • Jason Spangler says:


      Thanks for the question. It sounds like moisture may have caused this issue. The questions are this:

      1) Is this moisture differential coming from below or did it happen from the top?
      2) Is/was it an isolated instance or is it still an ongoing problem

      Sanding may help the symptom, but if the problem isn’t fixed then the symptom will come back with a vengeance.



  21. Ryan says:

    Good Morning!

    We are preparing to install a wide plank solid wood 3/4″ thick by 6.25″ wide hickory wood floor. Our house is 140 years old and the subfloor is not level in certain areas. We have done alot of work and leveled it to an extent, but it is still outside the thresholds of the 1/8 to 3/16 inch specified by the NHFA guidelines. The floor is fairly level east to west, but north to south it currently is not level but has a slope.

    What the are implications of installing wood flooring on a sub floor that is not perfectly flat? Will this cause buckling, crowning, cracking of boards or any other visual issues (other than the final floor product possibly not looking flat) with the hardwood floor itself?

    Thank you!


    • Jason Spangler says:


      Thanks for the post. You continue to say level. A floor not being level is ok. The question is, is the floor flat? Not being flat can cause problems with plank adherence to the floor, hollow spots, T/G not fitting correctly, etc. I would consult with NWFA, the National Wood Flooring Association, for any additional symptomatic problems that may exist.



  22. Andrea M Devery says:

    We installed Morning Star Bamboo in our living rooms and kitchen. We removed old sub flooring and replaced with new thicker sub flooring. We used a high quality pad/water vapor recommended by the store where we purchased the flooring. The bamboo was acclimated in our home for around 8 weeks prior to installation. Now the wood floor in one section under newly (3 month old island) is cupping however there is no water source or moisture in that area?? We have check all appliances and sink for leaks and have found nothing. What could this be from?

    • Jason Spangler says:


      Thanks for the question. It could be from multiple areas normally, but in this case, it seems to revolve around the new island and may have something to do with the weight of the island and/or the island blocking any potential breathability of the floor. I am just guessing. Your best bet is to either have the manufacturer come out and look at it or contact NWFA-National Wood Flooring Association at nwfa.org and find a certified inspector to come out and look at it.



  23. Chris says:

    I had a company install solid Jatoba hardwood floors. It was clear that they did not seem to know how to install the very hard wood and put pressure on some corners and created a split. We had them try to repair, but that was worse. My biggest concern is that the floor are uneven even though the subfloors were screwed down and in good shape, the wood seems to be ‘rolling’ some boards are higher than others and the floors are squeaky. Can I do anything beyond replacing? It was very expensive and the wood covers 90% of the first floor of the house. We have tried monitoring the ambient moisture, but in winter it’s hard not to fall down in moisture. Any suggestions would be welcome. It’s sad because the floors looked awesome for about a month (barring the cracks).


    • Jason Spangler says:


      Thanks for the question. This may be answered, best, with a phone call. You may contact me at 800-634-9961 X235.

      Jason Spangler

  24. Francis Tremblay says:

    My floors are cracking and spitting all over my house . I had laid down pile and stick flooring throw out my home and now after time l have noticed large cracks all over the place hall ways bed room and in the kitchen . What would be causing such a problem throw out my home . I am not sure how to add pictures but if you need them l can send to you so that you can see to for your self what l am talking about.

    • Jason Spangler says:


      Thanks for the question. This may be answered, best, with a phone call. You may contact me at 800-634-9961 X235.

      Jason Spangler

  25. Ruth glenn says:

    I have a home build in 1968
    Well kept but the cracking and popping in my bedroom and hall l’m 85 yrs old and its. really scarring when someone walk when l’m sleeping ,its hardwoods laid concert laid can you please help me

    • Jason Spangler says:

      Ruth, thank you for the comment. I would contact a trusted, local flooring retailer in your area and have them look at your individual situation. If this avenue doesn’t work, I would recommend you go to http://www.nwfa.org and see if they can recommend a certified inspector that can come out and give you some guidance. Good luck.

Leave a Reply

Your email address will not be published. Required fields are marked *