Flooring for very uneven below-grade concrete slab

Discussion in 'Help Selecting the Best Floor Covering' started by KateSw, Jan 10, 2019.

  1. KateSw

    KateSw Member

    F47A19DC-B06E-46CD-A0EA-B03471618631.jpeg 43B19D4B-FE67-4C60-B6CD-E05DB8681481.jpeg

    Hi. We just had the asbestos tile removed from the lower floor of our 1958 raised ranch. We’re left with a very uneven (1-3/4” variation over maybe 8 feet) below-grade concrete slab that has glue (negative for asbestos content) and occasional missing chunks, as well as a spot where a pipe seems to have been dug out.

    What are our flooring options?? This room is a rec/TV room. We haven’t tested for moisture but we’ve never seen any signs of dampness at all. We do NOT want carpet because we have dogs who have occasional accidents. We received an estimate of over $4000 for an epoxy floor which we didn’t really like anyway. Our budget is tight. We received one suggestion to use ceramic tile over lots of mastic, but we’re not sure about that.

    Any suggestions??
  2. Tom Potter

    Tom Potter I Support TFP

    How many square feet is the space? What are your expectations? A perfectly flat floor & your going to be paying for a lot of prep work.

    I would be thinking glue down LVP. If you can live with a few imperfections you could get away with not having the floor perfectly flat. Just be prepared to possibly see some humps/dips.
    • Agree Agree x 1
  3. Incognito

    Incognito No more Mr. Nice Guy! I Support TFP Senior Member

    You cant SEE dampness that's been migrating over 60 years through a basement concrete slab KateSw.......to the extent that it's a long term threat to 21rst century CHEAP plastic floors from China.

    What I do see is erosion of the concrete and remainder of the existing cutback adhesive that is evidence of "dampness" (moisture vapor emission pressure). There is also evidence in the photos of some degree of alkaline salts leaching through the slab from that condition.

    Here's the good news. If those asphalt tiles were original to the home built in 1958 you've really got a VERY modest alkalinity and moisture issue to contend with.

    Urinating pets in a basement? Wow, I can't think of any CHEAP solution that I would be comfortable with.
    • Like Like x 1
  4. Mike Antonetti

    Mike Antonetti I Support TFP Senior Member

    I talked to two people today about moisture, I think I’m just going to say vapor because they simply do not comprehend moisture other than it’s liquid form.

    Phone call was the homeowners garage paint was failing wanted me to remove two coats of paint so he could put epoxy down. Handyman and homeowner is supposed to pay for removal. I start talking about moisture and he says we’re high and dry.

    Another one is this hardwood job. Homeowner says the installer didn’t do good job.part of it buckled up and I see a liquid membrane but smell notch for adhesive. I explained about humidity, moisture causes cupping, he thinks it was 3 day acclimation. I ask what’s the current humidity? He did not know. I estimated this 1250 ft removal @2800$ 2-1/2 years ago. I vaguely remember, looked at my records. I’m thinking @ 4200$ now, I know too much more and what needs to be removed.

    So I don’t like seeing that cutback, they probably rolled an encapsulator over top, moisture vapor being trapped under chosen product.

    I need some rest to recharge. I’m sure you all would agree!

    Attached Files:

  5. KateSw

    KateSw Member

    Thanks for your response, Tom. We have about 500 sf including a laundry room, closet, small entryway, and the open area. We don’t care about having a perfectly flat floor. (We didn't notice the unevenness for 20 years until it was pointed out to us!) We just want a practical, decent floor.

    We looked at NuCore cork-backed LVP yesterday and were intrigued, but I’m concerned by some of the comments about buckling. Porcelain tile, as suggested by our contractor, would be great but I am concerned about the amount of mastic required to make the floor even enough for tile.

    (I appreciate the other responses too. I’m just not sure how to respond properly! I haven’t posted here before.)
  6. KateSw

    KateSw Member

    And what do you do about moisture/vapor issues? I assume you want a substrate that blocks the transmission of the moisture. What flooring material will do that without getting damaged? Or allowing the growth of mold?
  7. epoxyman

    epoxyman Pro Member

    If you do decide to go with epoxy
    Make sure to use a good moisture/vapor
    Primer like Koster if not there’s a big possibility of it coming up.
    And for the install of Koster the floor has to be shot blasted for it to get a good bond.

    • Like Like x 1
  8. Mike Antonetti

    Mike Antonetti I Support TFP Senior Member

    You had the flooring removed by an asbestos abatement company?

    Why didn’t they grind/remove the cutback adhesive? That gives you more options of flooring to choose.

    Moisture/vapor is quantified. To know how much is there or flows is needed to know how to Block/Control it.

    I see a window, that’s a good sign versus being totally underground.

    Large tile needs flat, smaller tile can follow contours. Sounds like you can adapt to conditions versus adapt the substrate to accept your product(large tile 1/8” variation in 10’ recommended)

    I don’t like floating as it provides some air, darkness, opportunity for mold to grow, smelly air.

    Properly installed tile minor levels of vapor from underneath the floor with a vapor barrier breached under the slab will allow flow into the space where monitoring and control of humidity can be accomplished through mechanical means (hvac/dehumidifier) to maintain RH of not more than 60% continuously.

    “Wet will go to dry” meaning it will migrate until reaching equilibrium. Your nice climate controlled living space is not balanced with the outside world. Heat goes to cold as an analogy. Fun huh?
    Last edited: Jan 11, 2019
  9. KateSw

    KateSw Member

    Hi Mike,
    Your response was very helpful. The concept of an artificial environment holding off the outside world made things click for me. Thank you!
    • Like Like x 1
  10. KateSw

    KateSw Member

    Hi Mike,
    I’ve been studying your response and I just want to thank you again for the feedback and suggestions. (I’ve been looking up “cutback” and “encapsulation”!) I don’t know why the asbestos abatement company didn’t remove the cutback but I’ll look into it further.
    Thanks for your help!
  11. kwfloors

    kwfloors Fuzz on the brain Charter Member I Support TFP Senior Member

  12. Mike Antonetti

    Mike Antonetti I Support TFP Senior Member

    Normally when they remove the asbestos containing cutback they use a dissolving chemical called bean-a-doo which is somewhat oily and clogs the slabs pores to allow thinset to bond/lock mechanically into the slab. Since/if the cutback does not contain asbestos it can be grinded off. You then have clean concrete to bond pretty much anything to. That doesn’t mean there is no moisture vapor issue that can cause flooring and adhesives to fail but it gives you more options.

    If it’s not flat locking mechanisms will have issues, lvp, laminate etc.

    Gluedown plank will follow curvature preferably no abrupt changes.

    If moisture vapor barrier under slab is 100% intact and a moisture test is conducted then you have a known RH of slab and can make proper decisions based on that number. A slab has an equilibrium where moisture is balanced without releasing H2O at the surface directly under finish flooring. If a barrier is breached then the Rh in slab is fluid meaning it’s a snapshot in time and may vary depending on moisture coming up from underneath.

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.