Magazine for professional home renovators.

The product that keeps basement floor installations dry

I visited the manufacturing facility of DMX a few weeks ago and got the story on a new product named DMX One Step Underlayment made right here in Ontario. I wanted to take some pictures of the process to prove that this product is not actually made in China, but president Steve Sennik said if I published photos of the process, he’d have to kill me.

The next best thing is right here in this video. Learn its properties, and why you will want to use this product on every basement floor you install from now on. For a more detailed video on the installation process watch this video.


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Rob Koci is the publisher of Canadian Contractor magazine. 647 407 0754
33 total comments on this postSubmit yours
  1. I need to shim my floor because it has a slope toward a drain. The gap is about 2 inches at the drain hole.
    Do I shim directly to the floor then lay the underlayment or do I shim on top of the underlayment.
    I do intend to lay a 5/8 board over the underlayment then my carpet or other finish.
    Any info would help.


    • Hi Brian,

      We recommend the application of a cementitious self leveling compound on the top side of the concrete slab to bring the slope to within 1/4″ in 4 feet prior to the installation of the 1-Step membrane, the recommended standard slope for floors.

      This will direct any water that does get into the basement area to be drained to the outlets beneath the 1-Step membrane. Using a shim method to apply a top side correction for too much slope has not been successful for most do-it-yourself handymen if they are not experienced at using the proper tools and fasteners for this type of repair.

      In addition, this would most likely require some use of fasteners that pierce through the 1-Step membrane that would need to be sealed, something that adds work to the install.

      Should you have further questions we would be happy to answer.

      You can reach us at or me directly at

      Thank you,

  2. We have a basement with a moisture issue. No puddling, or evidence of it when we did the ‘patch test’ in various areas, but enough that we had to remove and toss all the previously laid laminate due to mold and mildew build up underneath. Our contractor convinced us we did not need a vapour barrier underneath as the concrete needs to breathe and laminate is apparently totally waterproof. We have no leaks in the walls, and we have cut open sections of the wall to test for moisture and odours and found none. It all seems to be coming in through the floor. At present there’s a ‘wet dirt’ type of odour that becomes stronger during humid/rainy conditions. We’re also looking at possible causes of water build up under the house itself.

    We’ve since chemically sealed the floors throughout, painted (3 coats), added a portable dehumidifier, and are ready to redo the flooring. On average I’d say we have about 50-60% relative humidity down there without the dehumidifier running. I like the laminate for the fact that it shouldn’t hold moisture or odours like carpet would. Would it be okay to do a double layer of 6mm vapour barrier directly on the concrete, and this ‘DMX 1 Step’ on top of that as a sub-floor/extra vapour barrier insurance? Or would it cause additional potential problems? Allowing the concrete to ‘breathe’ into the basement in any way just leads me to believe it’ll ruin any flooring we try down there.

    • Hi Tim,

      From the details described in your question, it does appear as though you may have ground moisture conditions that are affecting the home environment with too much humidity, as evidenced from the “wet dirt” type odours that you have noticed. If you have not experienced or seen evidence of leaks in the foundation walls, then there are some conditions which may apply to your home that are contributing to the high humidity;

      a) The age of the home, or the construction of the home may not have allowed for proper vapor control by the use of vapor barriers, ventilation fans in the bathrooms and kitchen areas, or the lack of use of these fans when needed.

      b) Ground moisture may be high in your particular area, meaning that you could be affected by a high water table level. This can cause excess vapor moisture to migrate upwards toward the dryer air in the basement and wicking through the pores or capillaries of the concrete slab, which can have an impact on the humidity levels in the basement

      c) The grading around the property may not be directing surface away from the building properly, which can lead to high moisture conditions in the soil around the foundation and high humidity levels in the living area due to what is termed “vapor moisture pressure equalization”. In simple terms this means that the high concentration of ground moisture is trying to equalize itself to the interior dryer air so both the interior and exterior environments have the same humidity levels.

      d) Improperly installed or lack of perimeter foundation drainage of ground moisture to a positive outlet can lead to high moisture conditions in the soils around the basement, and under the concrete slab, which can lead to high humidity in the basement area.

      There are others factors as well which can lead to high humidity in homes such as described in your question, but for the most part, the conditions above are the more common links to the reasons for the humidity.

      As for the use of a vapor barrier (flat sheet) on the top side of the concrete slab it is not recommended since any moisture condensation will collect and allow mold/mildew to propagate, and if you ever do get a leak in the foundation the water can build up under the poly sheet and stay wet for some time. This will have a negative effect on your laminate flooring and assist in the propagation of moisture induced damage to wood and other porous materials.

      The use of the DMX 1-Step provides the properties of a high quality vapor barrier material with the added advantage of providing drainage for leakage water to flow to the floor drain area, thereby not accumulating water of any quantity for an extended period of time. If your basement is not yet completed to the drywall stage, you can seal the 1-Step to the concrete walls using a limited expansion polyurethane foam to seal off any vapor moisture from finding its way into your living space.

      If your walls are finished to the drywall stage you could look to sealing the vapor barrier used to separate the bottom plate of the exterior wall framing from the concrete slab to the top of the 1-Step thereby creating a seal around the perimeter of the basement walls. This also would provide protection from vapor moisture traveling into you living space in the basement from beneath the concrete slab area. The use of an elastomeric sealant to seal the two membranes together would create the appropriate seal, which can be found at most building supply outlets.

      When dealing with high humidity levels in a home there are many factors that can influence the cause that need to be investigated and ruled out one by one in order to find the true source of the humidity input source. Basements are cooler than the rest of the home because of their location, and humidity shows up usually first in this area than in any other area of the home. Good ventilation and moisture controls are the first line of defense against most humidity related conditions within a home.

      Our technical person has given some information on conditions that may happen, but if you would like to be more specific you can contact me directly and we will get all your questions addressed.

      Thank you,

  3. Hi, can I lay vinal ( Allure ) planks directely over DMX or do I have to lay plywood between the vinal planks and DMX?

    Truly, Mike.

  4. Hi Mike,

    We would suggest that you use a plywood or OSB board on top of 1-Step and if you are using a Vinyl flooring.

    The reasons we suggest this are as follows:
    – In most cases Vinyl is too flexible, and would move too much if laid directly over 1-Step, which would wear at the seams of the planks.
    – Vinyl may be too light. We have found that if a product weighs less than 1.8 lbs/sq.ft. it is too light to keep from moving too much.
    – Vinyl flooring also has an ability to telegraph the surfaces irregularities in the substrate through the vinyl planks over time. It would do this by settling into the negative void of the 1-Step, which would be a problem over time.

    I hope this does not deter you from using our product, however, with Vinyl planks we suggest using plywood.

    Thank you,

  5. Hi, Paula

    i think i’ve had moisture issues through my concrete floor. i have no evidence of leaks anywhere. Before covering up my floor, i have never had any musty smell on the floor. When i finished my basement, i used a special underlay and then carpet. After a few months, my basement started smelling very musty even wtih a humidifier running. Since then i tore out the carpet and underlay and left it for a few months and there was no smell at all. So bizzare. I then did some research and was thinking i was getting some moisture through the floor when covered and was going to install drycore until i stumbled uopon DMX step 1. With the idea of allowing the floor to breath better, I installed the DMX product with 12mm lamminate on top and left the quarter rounds a couple mm above the lamminate to allow airflow. It has been almost a year with the DMX product but still notice a very light musty smell; probably because im paranoid and go looking for it. when i bend down to the baseboards/quarter rounds and put my noise to it, i can detect a slight musty odour; keep in mind I run a newer dehumidifier. Again the smell is no where as bad as when i had the last underlay and carpet. i was wondering if you recommend that i cut out vents around the perimeter every 10 feet (like as for drycore); exposing right down to the concrete and put vent covers to allow more airflow. Again, when the floor isn’t covered, there is never a smell. i am thinking that more airflow would help. i would appreciate your opininion. Note, i have several air ducts + a cold air return in the basement to aid in air circulation. Looking forward to your comments.

  6. We are looking at possibly using DMX One Step over a concrete basement floor. We are going to use vinyl planks as our flooring. Is there a certain size of plywood/OSB board you suggest. 1/4 or 3/8. We have ceramic tile that is laid by our doors and we want to try to match for a seamless transition between the two.

    • Hello Tristan,

      I am sorry for the delay. We suggest 5/8 OSB or Plywood with the Tongue and Groove.

      Thank you,

  7. I am looking at installing DMX 1 step under a hardwood floor. I want to float the hardwood floor. I assume that i will need to put down T&G plywood first on the DMX to get a good surface or could it be applied directly.

    • Hi Glenn,

      Yes you are correct the T&G would need to go on top of the 1-Step in order to ensure that you have the correct surface for your hardwood.

      Thank you,

  8. I see that DMX-1 is used on basement, but can this product also be used on a crawspace floor? If so, how would it be installed and what prep needs to done to the floor? At this time I have hardwood on the kitchen floor and plan to remove and install tile. Look forward to hearing back from you.

  9. Hello Michael,

    Your question was very intriguing, so I included

    Crawl Space w/Kitchen over:

    1) Level out the floor of the crawl space (if it is dirt now), if concrete with self leveling compound.
    2) If the walls of crawl space are insulated, lift up insulation 12″ above dirt or concrete floor and tack with tape.
    3) Install the DMX AG (if it is dirt floor) over entire floor area, ensuring overlaps are 6″ minimum and taped with Tuck Tape.
    4) Install the DMX 1-Step (if it is a concrete floor) over floor area, ensuring butt joints are taped with Tuck Tape.
    5) In both cases, seal the membrane to the exterior walls using a polyurethane foam (from the can) to make the membrane vapor tight (see dwg on our web site).
    6) Return the insulation on walls (if it exists) back to the floor elevation, ensuring the vapor barrier over the insulation is intact (no tears or holes).
    7) Since the area is a crawl space, the plastic HDPE of the DMX membranes should not be left exposed and should be covered with a product such as wood paneling, steel sheeting, to protect it in case of fire as the plastic can contribute to smoke development in a fire situation and required chemical extinguishing not water when left exposed.

    Trusting this answers your question, good luck with your project. Get back to us if you should have additional questions.

    Thank you,

  10. Hi, we are planning to use DMX or Delta FL to apply directly to the concrete floor in the basement. We want to use laminate flooring. of 10mm or more. My question here is:
    1. What is the difference in using Delta and DMX
    2. Is it necessary to hae a plywood sub floor to be put on top of the DMX/Delta
    before laminate is installed?
    3. Should we use foam padding between DMX and Laminate

    Please advise

    • Hello Puneet,

      1. DMX 1-Step has a foam on the base of our product, at the very least this will eliminate the clicking sounds of the rigid plastic from clicking on the cement. In the Delta installation video they suggest that you use a needle-punched geo-textile (landscaping cloth) below the Delta FL in order to eliminate this noise.

      2. With a 10mm or thicker Laminate you do not need to use OSB or Plywood, you would just need to ensure that your cement is within a 1/4 inch differential within a 4 foot radius.

      3. If you would like to use a foam padding in between DMX 1-Step and your Laminate this will add an additional layer of friction, however, you do not need this as protection for your floors as the DMX 1-Step is a vapor barrier.

      Please feel free to contact us again should you have more questions. Also on our website we have links to videos that compare us to our competition and more information about our product including testimonials from other customers that have used DMX 1-Step.

      Thank you,

  11. I want to install carpet in my basement. I am planning on using DMX 1-step and will put OSB on top. Can I put a tapcon through the DMX?


    • Hello PA,

      You are absolutely able to use Tapcons to secure the OSB into the cement. We recommend that you predrill the OSB and the DMX 1-Step before you use the tapcon screws so that you can dip the tapcon screws in a butyl rubber or a polyethylene sealant in order to coat the DMX 1-Step and maintain the seal.

      There is more detailed information about this on our Frequently Asked Questions page on our website:

      Please feel free to contact us with more questions.

      Thank you,

  12. I converted a garage into a playroom and the floor is cement. I put laminate flooring down; however, the floor gets so cold in the winter, it’s unusable because the floor is basically like a high powered air conditioning unit. Will DMX stop the cold. Should I put plywood down to further help insulate? Thanks

    • Curious if there were a reply to Matt’s post. I am converting part of my garage into a home workout room. Trying to determine best application for the flooring, keeping it from being too cold, etc..

      • Hello Matt, David,

        Yes DMX 1-Step provides a thermal break that will help increase the warmth of the floor.

        So you will definitely notice a difference if you use DMX 1-Step under a 10mm or thicker laminate or a 3/8 inch Engineered Hardwood, but there would be additional warmth from adding an additional layer like plywood.

        Thank you,

  13. I am planning to use it in Basement. In case, After flooded in basement(with DMX Underlay), Can i wash this product and re-use it ? Please explain test case scenario for this product ?

    • Hi Anthony,

      Yes you can wash the DMX 1-Step and then relay it and use new tape for a new vapor seal.

      What type of test case scenario would you like explained Anthony?

      I would be happy to provide you with any specifics you would like. Feel free to post the specifics you are requesting or email me and I will provide it direct, whichever you are most comfortable with.

      Thank you,

  14. Hi Robert, Great product and great video, thanks to you guys.
    When can we see the next interview on the OCOT?
    If you go there, please do us a favor, let no stone un touch it.

    Good luck

  15. Hi there. . Looking to install allure vinyl tile and plank (click version) throughout a one floor 1150 building on concrete slab. Please explain best process from laying dmx to finished surface. Thx

  16. Hi,

    So I am looking to do a basement that is generally dry but gets some minor foundation leaks through the wall in the spring. I am not framed yet and i have seen the suggestion of running 1Step up the wall an sealing it. Can I do this and then have spray foam insulation or am I going to have issues?

    Also I here lots of talk about hardwood, can this be used for real hardwood or is it just the engineered hardwood? is the a way to do ceramic over 1Step?

    Thx in advance

  17. Just wondering if i can use DMX AG for underlayment in basement?
    If not why. If yes then what is the difference between DMX AG & DMX step-1

  18. Hi! Do you recommend the use of 1-Step with ceramic tiled flooring, in the basement, and if so how would you suggest that I do this? We want the tiles to be warmer, and match-up in height to the carpet that will also be installed in the basement.

  19. I am finishing my basement and plan on using laminate flooring on concrete. The concrete floor is slightly uneven in certain areas, 3/4 on an inch over a 5 foot radius. Can I use Dmx and shin in te low areas.

  20. We are using sheet vinyl in the basement. Can this be laid directly over 1-Step.

  21. Hello, I live in northern MN and have built a 3 season (soon to be heated) porch on the back of our cabin. I have a 3/4″ treated plywood subfloor and wish to install your DMX 1 Step on top of it and vinyl plank flooring on top of your DMX. Good idea or not. Suggestions! Thank you.

  22. Hi Paula, just I wander the perimeter of DMX 1 as it is mentioned above should be sealed (closed), my question is: if this will not create a moister/air trap and in time to develop moisture? Those bubbles are not designated to allow the air/moisture to travel and escape? Thank you!

  23. Hi Paula… thanks for all the tips… just wondering why there is no answer to Tim from November 2013… we are having dampness issues in our basement and looking at installing your product with Laminate flooring… Tim is saying he still smells a musty smell and wonders if he should install air vents in the floor… please advise.. thanks so much

    • Paula, I am wondering if this product can be installed so that it is run up the wall an inch or two and sealed to the wall’s rigid foam insulation and then have floor vents cut every 10 feet or so like with other basement subfloor products. If not, please advise. Thanks

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