Rubber & Vinyl Floor Moisture Testing

Navigating the flooring world, we often come across the industry’s stalwarts: vinyl and rubber. Praised for their durability, versatility, and aesthetic appeal, these materials are mainstays in residential and commercial settings.
However, while their resilience to moisture is well-known, the significance of moisture testing for these materials is often underestimated. Let’s delve into why even “water-resistant” champions like vinyl and rubber aren’t exempt from the meticulous checks against moisture.

The Different Characteristics of Rubber and Vinyl Flooring

Vinyl and rubber floor products have a myriad of advantages including excellent water resistance, easy maintenance, and a natural scratch resistance. They are typically durable and long lasting and come in a variety of applications to suit almost any location.

The other advantage to vinyl floor products is that they are available in a wide range of looks and styles to compliment any décor. Vinyl flooring has increased well beyond the standard sheeting in the range of floor products available.

Vinyl tile, in both commercial and standard grades, and vinyl planking are options with either locking or standard glue-down installation. Some vinyl floor products include limestone or fiber additives or backings that increase their durability and chip resistance or offer more cushioning underfoot.

A good example is flex flooring, a product made to go over existing vinyl flooring. The combination of polyurethane top layer and fiber backing give it better flexibility for both installations and for comfort.

Rubber flooring provides a slip-resistant surface that holds up very well under heavy foot traffic. It can be purchased with a number of designs, colors and patterns for an easily customized look suited to either home or industrial use. Textures like round stud or diamond grip increase the traction level of foot traffic while still having an industrial-standard resistance to wear and damage.

Rubber flooring is available in either tiles or sheets and can be applied with glue, for a movement-free flooring, or as “loose lay,” attached with double-sided tape for quick removal if required. Rubber tiles are also available in interlocking styles for adhesive-free applications over a variety of surfaces.

Because both vinyl and rubber floorings are naturally impervious to water, it would seem that moisture testing for rubber or vinyl flooring applications might be unnecessary. But the cost of moisture-related problems can be just as high even with these seemingly “moisture proof” floors.

How Can Moisture Cause Problems with Rubber and/or Vinyl Flooring?

The real problem for vinyl and rubber flooring is often in the subfloor, or in giving moisture access to the subfloor. Moisture can impact the flooring in two locations:

  1. Seams (if there are any) – Tiles and planking in either vinyl or rubber styles will naturally contain more seams in a finished floor. In a loose-lay or floating installation, those seams provide spaces for moisture to seep down through the seams and either enter the subfloor or sit between the subfloor and the flooring affecting both the product, the subfloor and the adhesive used to connect the two. In a fiber-backed product, it is easy to see how this can also cause warping, buckling, swelling or even lead to mildew.
  2. The subfloor itself – Because rubber and vinyl products are so well suited to damp or humid conditions, they are often applied directly (or indirectly) over concrete or other sub floors. But if that subfloor is not dry to acceptable levels, the reality is that product and/or adhesive is at risk of a flooring failure.

How Do You Check for Moisture Under Vinyl Flooring?

Use moisture meters or conduct a relative humidity (RH) test to check for moisture under vinyl flooring. RH tests involves drilling a hole into the concrete and placing a probe to measure the moisture levels.

Can a Moisture Meter Read Through Vinyl Flooring?

While some moisture meters are designed to detect moisture beneath surfaces, their accuracy might be compromised when reading through vinyl flooring due to their inherent moisture resistance. For precise readings, it’s advisable to test the subfloor directly.

What is the Moisture Content for Vinyl Flooring?

While vinyl flooring is highly moisture-resistant, the acceptable moisture content in the subfloor before installing it usually hovers around 75-80% relative humidity, depending on the manufacturer’s recommendations. Always refer to specific product guidelines.

Does Vinyl Flooring Hold Moisture?

Vinyl flooring itself doesn’t retain moisture, but if installed over a damp subfloor without proper checks, moisture can get trapped beneath, leading to issues like mold, mildew, or flooring failures.

Moisture Prior to Installing Rubber and/or Vinyl Flooring

Moisture, particularly in a concrete slab, can come from a number of sources. If the slab does not have an adequate moisture barrier underneath, moisture can wick up from ground sources in a continuous cycle. And any existing slab can still be subject to moisture intrusion if it is in contact with leaking plumbing or irrigation systems, ground moisture or excess humidity in the environment.

In a new slab, if the concrete has not dried internally to the levels acceptable for the particular flooring and/or adhesive used, moisture will continue to work its way to the surface under the applied flooring. (Explanation of the process of moisture movement in a drying concrete slab)

For any flooring installation, adequate moisture testing is imperative. For a concrete subfloor, relative humidity (RH) testing is the best way to get a true picture of the moisture conditions within the slab to prevent any negative moisture impact to the finished floor.

The ASTM F2170 recommends in situ probes for RH testing. Test methods like the Rapid RH® L6 provide fast and accurate test results within the subfloor so that any issues can be remediated before putting the flooring at risk.

When installing a rubber or vinyl floor, moisture testing is just as, or even more, important than it is with any other flooring product. Because where the rubber meets the road, moisture can still jeopardize your installation.

While vinyl and rubber are touted for their moisture-resistant qualities, the adage “better safe than sorry” holds. Proper moisture testing, understanding the intricacies of these materials, and recognizing potential pitfalls can ensure your flooring stands the test of time, moisture, and wear.

After all, in the flooring world, providing a dry foundation can make the difference between an installation that flourishes and one that falters.

Last updated on August 31st, 2023


  1. Paul Kirk says:

    We had very heavy water damage from our roof having had shingles ripped off during a storm. One room below the damage had considerable flooding and the vinyl floor buckled very bad. When it was removed the Subfloor was swollen with water. Over the next few days other floors in the house started to get raised areas, starting in the next room and spreading through most of the house (ranch w/crawl space).
    The Insurance adjuster use a Moisture meter on the vinyl floor and said there isn’t any water under that flooring. Would the meter pick up moisture through the vinyl floor. I’m thinking that the Sub-flooring is soaked and causing the floors to bubble up in areas and now making noise. This started shortly after the initial damage.
    The adjuster says that the water wouldn’t travel under the floors, but I’m a retired Fire Captain (Professional) and have had considerable training in structure, fire travel and water travel. I know that “water seeks its own level” meaning it spreads horizontally. So, if there was copious amounts of water coming onto a surface the water will spread horizontally until enough of it has dispersed vertically, in the process soaking everything in it’s path i.e. Sub-flooring.

    Please advise,

    Thank you, Paul.

    • Jason Spangler says:


      Sorry for you issues here. First, any meter reading on top of vinyl into a wood subfloor would only be giving you a “relative” reading and would have to be compared to an area of the floor that looks to be unaffected by moisture. Some meters would work for this, others may not. I would also agree with your thoughts on topical water dispersion into a wood subfloor. Good luck.

  2. jacob l king says:

    I live a a newly built double wide manufactured home. recently had a hot water heater malfunction and had had water through a portion my home.i have linoleum flooring throughout the house.. an insurance adjuster came and was having moisture reading through the linoleum, which I was curious about . they are calling for extensive repairs even though the floors appear and feel the same as they were before aside from a few small patches in my laundry room where the hot water heater is located. I have friends that have years of experience in construction and repairs who have told me not to be concerned after they looked at it. the reason I ask is because of the level of extensive work the lender of the home wants to have done, obviously to make sure it’s back to like new condition. but I can’t find any contractor that will take the job.. I want take my buddies advice and let it go. if I could find someone with a crew to take the job I would probably do that, every contractor and independent worker I have talked to straight up tells me no when I ask them. I’m just trying to exhaust all angles of information. sorry the message is so long. thank you

    • Jason Spangler says:


      Thanks for the email. I would call out a remediation company and see what they think and can do. They take care of problems like this all the time. Good luck.

  3. Bridget says:

    I have a client who lives in a second story apartment (I am a licensed mold assessor though the state I live in currently doesn’t do licensing for mold). She had a minor leak from her shower that went undetected for maybe 2-3 months and a very minor leak under the kitchen sink (small area of the shelf was bubbled). The property management is not overly helpful and wouldn’t let me look into the lower apartment to assess the damage. I did see photos and the damage to the lower apartment was very minor. She had a remediation company come in and they read all the vinyl flooring as 99.9% saturated. Nothing was visibly damaged and the leaks appeared to be minor to me with no water staining of the baseboards/trim and the baseboards were reading about 10% on my meter. I highly doubt that this leak caused the subfloor to be that saturated (I am not entirely sure of the material of the subfloor because I couldn’t see from the inspection hole they cut). I guess my question is: could the remediation company’s meter have given false positive readings of the vinyl material? I highly doubt that the entire subfloor was wetted to that extent. Usually you will see some variation in values when moisture mapping wet floors, so I get very suspicious when I see all readings are 99.9%.

    • Jason Spangler says:


      Thanks for the question. Always remember that all meters are not created equally from a quality and accuracy standpoint and not all scales are necessarily the same from meter to meter. I am not sure what the 99.9% represents. Is this 99.9% out of 1000? What setting are they using on the meter? Etc. Lastly, not everyone knows how to properly use and/or interpret data from a meter. I hope this helps.

  4. Geoffrey Davies says:

    I have vinyl floor covering in my bathroom about 2 years ago and a dark patch appeared on the vinyl ,about 24 inches by18 inches , I’ve patch cannot be removed by cleaning ,nothing has been spilled on the floor and it does not appear to be damp , it is laid on a wood floor and I am pretty sure the guy who put it down didn’t remove the previous vinyl, which was nearly new .the vinyl he laid it on was colour black and the new vinyl is very light grey.What ca I do to correct? .

    • Jason Spangler says:


      Thanks for the question. I would reach out to the vinyl flooring manufacturer and ask them for feedback. It sounds like the color from the vinyl below may be showing through, but I’m not sure how that would be possible.

      Good luck.

  5. Andrew Kester says:

    I am a forensic and structural engineer, and I inspect buildings for a variety of problems including flooring damage throughout Florida. Moisture damage to flooring is one of the most common issues I see. Concrete slabs are permeable and actually transport vertically and horizontally due to capillary action, think of concrete as swiss cheese. A vapor retarder membrane is required by the Florida Building Code underneath the slab, but the required thickness is too thin in my opinion, and the result can be a damaged membrane that allows moisture into the slab. Unless you live in a desert area, there is always moisture in the soil trying to get into the slab.

    I often see flooring problems where new laminate or vinyl flooring products are applied over top of existing hardwood flooring, both on concrete slabs and on wood subfloors elevated above crawlspaces. The new flooring acts a vapor retarder preventing the moisture within the hardwood flooring from evaporating. Sometimes these are 50+ year old houses that never had a flooring problem until the new flooring was installed. With crawlspaces the situation can be devastating, I have seen entire subfloors completely decayed forcing the interior of the house to be gutted.

    To answer Karen’s question above, this certainly can occur without any evidence of moisture problems, because the wood could dry out enough not to have noticeable problems:
    “If there was moisture coming from the slab we certainly would have seen the discoloration or deterioration of the wood.”

    “The company pulled them up and told me there was moisture trapped under the parquet. The parquet was absorbing the moisture and buckling since the Cortec was vinyl and trapping it. ”

    The company was correct, and they should have known this beforehand, and refused to install that product over top of existing wood flooring.

    If you have a concrete slab floor system, I would not recommend installing anything over wood flooring, just pay the extra money to have it removed first. The only exception is carpet, which is not very popular anymore other than bedrooms (in Florida). And this presumes all carpet is vapor permeable, I don’t know much about carpet…

    If your floor system is a wood structure over a crawlspace, I would be very careful before installing any new flooring. You want to make sure your crawlspace is relatively dry and there are no current moisture issues with the wood subfloor and beams.

  6. Jeremy says:

    I recently had a fair amount of water get in after an external pipe burst. I’ve been using a moisture indicator to ensure everything has dried completely, and to identify what had to be removed. Everything is straight forward on how to measure different woods, concrete, and drywall. My question is: Can I use a moisture indicator to check that laminate or vinyl flooring is in a safe range? Or do I just need to wait for visible signs of damage? I’m not sure if the reader can be used on vinyl. I do know that I get the same readings on all vinyl flooring throughout my home. Even areas that did not get wet. Sorry about the length, and thanks so much for your time.

    • Jason Spangler says:


      Thanks for the question. Part of your question revolves around the quality of the moisture meter you are using. Some are going to perform better than others. On most installed floors that have suffered water damage as you describe, a good non-invasive meter will be used to give relative information, not absolute. Meaning, with the thickness of the floor product and the depth of the measurement scan, there is an aggregate reading between both surfaces. The nice thing here is that you can take a good meter and measure in areas that aren’t affected (using the results as a baseline) and rapidly scan towards the affected area, identifying suspect areas as the numbers increase. My guess is you aren’t “really” reading moisture IN the vinyl. Good luck.

  7. Karen Hardie says:

    Thank you so much for your response and the resouces provided. The installation instructions do say not to install Cortec over a wooden subfloor glued to the concrete. In reality that is what the parquet wood floor was. The installation company has a different opinion. I’ve also asked what the moisture reading was before they began; the evasive response tells me they didn’t check. However, the salesman and company are working with me to find the cause and solution. We will see!

  8. Karen Hardie says:

    My home was built in 1986 with parquet flooring installed in the living room and diningroom. I lived in the home since 2004 with no sign of any moisture related issues. The home is on a slab foundation and there is no exterior sign of any issues? Even through 4 hurricanes there has not been any penetrating water. In August, 2019 I installed CorTec flooring throughout the house. It was installed over the parquet in the LR & DR and on the concrete subfloor in the other carpeted rooms. In January I noticed a two planks buckling in the LR. The company pulled them up and told me there was moisture trapped under the parquet. The parquet was absorbing the moisture and buckling since the Cortec was vinyl and trapping it. I was told I needed to determine the source of the “leak or water issue”.
    I have talked to contractor professionals, no increase in water bill, water meter does not run with all water turned off, no sprinkler contribution, and no exterior signs of moisture. Also the between the installaton and buckling we had little rain, in fact there was a deficit of rain. Now there are a couple more planks buckling in another areas of the LR.
    If there was moisture coming from the slab we certainly would have seen the discloration or deterioration of the wood. How do I determine the cause and remedy?

  9. Sam says:

    Hi there would you please tell me how much moisture is it gonna be okay with cement slab all Wonder bored- slab and vinyl in the top thank you

    • Jason Spangler says:


      Thanks for the question. Unfortunately, you really need to check with the manufacturer of the products you are utilizing in order to get the maximum moisture thresholds. In general though, most floor coverings can be installed on concrete if the internal relative of the concrete is no more than 75%. Good luck.


  10. Christy Lynch says:

    We had vinyl plank installed in our laundry room over an old cement floor. We had also had a brand new furnace installed prior to that in the same room. The vinyl plank does not extend all the way under the furnace. Recently I noticed water spots on my floor and realized the trap where condensate drips was not properly installed and when the blower for the ac came on it was blowing water up and out behind the furnace. This potentially could have been happening for two summers. My builder is telling me the water didn’t get under the vinyl just running down the seems. When you step in certain areas it bubbles up between planks and if you wipe it up it smells mildewy. I’ve had a large fan and dehumidifier running but how do I know if water got under the plank and mold is forming or has formed? I just discovered this yesterday. The room is in the basement and there is a drain that the water would have tried to flow to. What should I do? Please help!!

    • Jason Spangler says:


      Thanks for the questions. About the only way I would know how to determine the extent of the damage would be to pull up an area of the floor and examine underneath. This may be best performed by a flooring professional in order to do as little damage as possible if only a repair is needed. Good luck.



  11. Milton says:

    Morning my name is Milton, and I have a cleaning company and one of my contracts is a kidney dialysis. They have a rubber wood like flooring and it’s been quite humid lately. How do I stop this or stop it from being humid.

    Milton Rosero morning

    • Jason Spangler says:

      Thanks for the question. I would say some type of portable dehumidifier in the environment would probably help. Good luck.

  12. Martin says:

    I have a vynil installation that after 6 months starts to appear circualar bubbles and looks like an orange skin. What could be the source of this problem?

    • Jason Spangler says:


      Thanks for the question. It could be moisture, it could be adhesive, it could be vinyl, it could be an installation issue, or a combination of any of these three. I realize this is a vague answer, but I don’t have much to go on. Is this a wood or concrete subfloor? Were moisture test done on the substrate? If so, what were the results? How many bubbles have appeared over how many square feet? Have you had anyone else look at it? Sorry I can’t be of any more help.

  13. Bree Ward says:

    I agree with you when you said that the advantage of vinyl flooring is that it has a wide variety of styles that can complement any decor. However, it can also be prone to moisture that might occur in the subfloor area. I like how you discuss it’s detailed and how testing is important in the installation. In case I’ll have to change my flooring to vinyl, I’ll definitely look for contractors who install them with moisture resistant techniques.

  14. Anna says:

    Cant mold grow under any floating floor with a moist slab? It doesn’t make sense to completely seal a wet slab that wont be able to breathe with a vinyl floor. I don’t care how waterproof this flooring is.

    • Jason Spangler says:


      Thanks for the question. This is one of the questions that people discuss with the increased interest and usage of WPC flooring. In my opinion, with the moist, humid environment created by the WPC, the likelihood of mold increases.


  15. Lilian M Rogers says:

    Jason’s article caught my attention and I wonder if I can get some advice about my situation. The concrete slab foundation of my 1950’s ranch house had glued down vinyl composite tile flooring. In August 2018, I bought luxury vinyl plank flooring from One of the big box stores who subcontracted to install it. A man came out to measure and take moisture readings. He said the moisture was high but if I bought 6 mil plastic and taped its seams it would do fine. So I did that. When I got home from work after the contractor left on the first day, at the edge where I could peek, I noticed no plastic had been put under for as far as I could see for about one third of the total flooring job. I called the big box store to complain. They spoke with the contractor and he insisted he had put down plastic. I went home midday the next day and the guy was putting down plastic but did not appear to be taping it, just unrolling big irregular pieces cut all jagged and overlapping them like a badly made jigsaw puzzle. I had to get back to work so I didn’t see if he actually taped it after. I called the store again to complain and they spoke with him and they said he claimed to have taped it. The store assured me there’s a one year warranty on workmanship so if I encounter any problems to let them know. Four months later I’m getting whiffs of mildewed vinyl smell. I’m thinking if I could measure the humidity of the flooring to see if it exceeds the manufacturer’s recommendations (Less than 5 percent), then I’d have a case with the big box store. Yesterday, a concrete guy measured areas in the house floor that are bare concrete and the highest humidity reading was .67 of one percent. So the slab itself appears dry, at least in the areas not covered by the vinyl. Do you think it’s worth my time and effort to do what I probably should have done at the onset- tear up some floor in the one room the worker insisted he did to find out did he actually put plastic? How important is it for the plastic to be taped? What kind of meter can I use to get the moisture reading for under the vinyl plank flooring? My concrete guy said his meter only reads concrete and wood. If I can’t afford to buy the appropriate meter, who would have one ( a flooring company?) can I ask the big box store to send out the first guy if I don’t know for certain that I have a problem? Thanks!

    • Jason Spangler says:


      Thanks for the questions. You ask many, on various subjects, so I hope to answer as many as possible. First, you don’t mention any real cosmetic or performance issues with the floor at this point. Many of these questions should be directed back to the manufacturer of the flooring product or big box store. Questions like, is the warrant still intact if the plastic isn’t taped? Does the floor have any antimicrobial backing on it? These may help you to answer the question of whether you should pull part of the floor up to verify any potential mold growth and taping of the seams. As far as the smell, again, I would contact the big box store and the manufacturer and have someone come out and inspect if it is really something that concerns you. You may also be able to have an air quality company come out and take samples. Many times odors on new floors may last for an extended duration and then go away, but there is nothing wrong with voicing your concern. As far as the concrete moisture scales you mention, none of them are concrete RH%. I can only guess that the one you reference from the manufacturer is moisture content, but I can’t be sure. The other scale from your concrete guy is one that I can’t even make a guess on. I hope this all helps. Good luck.


  16. Claire says:

    Hi. We had a new concrete slab laid over a damp-proof membrane a month ago, with piped underfloor heating laid within the slab. The underfloor heating has been on for two weeks now. The new slab is 4-6 inches thick. It is adjoining a much older slab (which also has a DPM) in the adjoining room (which we have just knocked through).

    The flooring company came today to lay Quickstep Pulse click vinyl wood-effect (plank shape) flooring with basic underlay. They did a surface moisture test and said the moisture was far too high at around 5-6% when instructions say it should be < 1.5%. They didn't lay the floor and said it might take 6 months to dry. The moisture levels seemed to be high across both slabs, even the old one (we don't know how old – possibly 30 years?).

    What happens if we lay this floating vinyl floor, with underlay, on a damp surface? How would it damage the floor? What are our options if it is still just as damp several months down the line? Would you recommend painting on a sealant?

    Thank you!

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