Questions about glue-down LVT in basement (moisture mitigation, floor flattening, and more)

[missouri_homeowner]

Hi all,

I am finishing my basement (~1500 sf) and my tentative plan is to install glue down vinyl plank flooring. I am leaning toward Armstrong Natural Creations vinyl plank. I did a bunch of durability tests on samples, and it was by far the best (couldn’t scratch it with keys/coin/etc. Could only scratch it with a steak knife). Mannington Adura Flex and Karndean Van Gogh came in 2nd place. All the others (mostly big box store brands) were pretty bad and scratched quite easily.


I have three categories of questions:

1. Moisture mitigation:

• Background:
  • There has never been any water intrusion and basement humidity stays below ~55% worst-case during the summer without running a dehumidifier.
  • I know the slab does not have a vapor barrier underneath, but I performed a plastic-sheet test (passed) and a calcium chloride moisture test measured a reasonable ~5 lb/1000 sf.
  • However, there was previously a small section of the basement that had sheet vinyl flooring, and it had a strong mildew smell when I pulled it up. So I’m paranoid about moisture issues.
• Questions:
  • Is this an appropriate prep/installation procedure?
    • Grind concrete to CSP ~1-2
    • Apply lithium silicate densifier to (hopefully) slightly reduce moisture vapor transmission through slab
    • Install LVT using Bruce Apex Pro adhesive (identical to Armstrong S-1000, just more readily available near me). It claims to be both an adhesive and a moisture barrier, and supposedly tolerates unlimited moisture vapor (just no hydrostatic pressure, but that’s not an issue here)
  • Would a product like Bostik Roll-Cote be helpful and compatible with the above prep/installation procedure?
  • Any other thoughts on how to ensure there are no moisture problems down the road?

2. Floor leveling:

• Background:
  • The floor is not very flat – can vary by almost 1/2” over relatively short spans. It also isn’t completely level – there is a ~1/4” slope from one side of the basement to the other.
  • The attached picture shows a rough contour map of the worst part of the floor.
  • The worst area is near the support post where the height changes by ~3/8” in about a 4’ span. You can feel it under foot when walking.
• Questions:
  • In reality, how flat does the floor need to be for glue-down vinyl plank flooring?
    • Most installation sheets state no more than 3/16” variation in 10’ or 1/8” in 6’
    • Is this to make sure the floor “feels” flat under foot, or is it actually for flooring integrity? I’m not worried about feeling the height variations under foot, but I want the floor to last a long time.
    • I would expect thin glue-down vinyl plank to mostly conform to the concrete height variations, although I do have concerns about whether or not the edges/corners would lay flat if they happened to fall on a sharp height transition.
  • This is my plan to get the floor as flat as possible. Any suggestions?
    • Grind down the regions between high and low to soften the sharp transition areas
    • Partially fill the low spots with self-leveling compound (e.g. Henry 555)
    • Feather the transition regions with patching compound (e.g. Henry 547)
    • All of this should help, although I think it will still be tough to get within 1/8” over a 6’ span.

3. Material sourcing:

• Where is a good place to buy Armstrong LVT?
  • I’ve found it hard to come by Armstrong Natural Creations LVT as it seems to be targeted for commercial installers, not residential homeowners.
• Anyone have experience with online retailers?
  • I’ve found it at a few online retailers (FloorCity.com, EFloors.com, FastFloors.com, QualityFlooring4Less.com)
  • I’m hesitant to order online as it’s hard to find good, reliable information on these companies.

Thanks in advance, and sorry for the long post!

 

[Incognito]

I cant see from the photo how rough that slab is and how severe any irregularities may be. We did not typically use a grinder to smooth out something like that because 12 grit sandpaper on a disk sander can get it pretty clean and smooth ENOUGH so after you clean it just up and toss a "skimcoat" (or two) it's plenty smooth for your needs. Like you say the vinyl will mold down to the contour with the adhesive pulling down any corners that might want to angle up. The only time we HAD to grind was where the inspectors wanted it pretty damn close to that 3/16" in ten. Seriously, we never really got big slabs that flat.

This is what I'd use rather than self leveling:

https://www.tools4flooring.com/arde...or-patch-skimcoat-10-lb-bag.html?gad_source=1

 

[C.J.]

Floorcity.com is legit. I’ve dealt with them before and personally worked with the guys through other companies and have nothing bad to say.

I would think for the amount of money you’re looking at spending on floor prep, adhesive and new flooring, dropping a few bucks on having actual moisture testing done would be a good idea.

 

[missouri_homeowner]

I cant see from the photo how rough that slab is and how severe any irregularities may be. We did not typically use a grinder to smooth out something like that because 12 grit sandpaper on a disk sander can get it pretty clean and smooth ENOUGH so after you clean it just up and toss a "skimcoat" (or two) it's plenty smooth for your needs. Like you say the vinyl will mold down to the contour with the adhesive pulling down any corners that might want to angle up. The only time we HAD to grind was where the inspectors wanted it pretty damn close to that 3/16" in ten. Seriously, we never really got big slabs that flat.

This is what I'd use rather than self leveling:

https://www.tools4flooring.com/arde...or-patch-skimcoat-10-lb-bag.html?gad_source=1

Thanks, this is good feedback.

I wouldn't call it rough or irregular, and the surface is actually pretty smooth. It's just that it's a bit wavy with a lot more height variation in a 6' span that the datasheet recommends.

 

[missouri_homeowner]

Floorcity.com is legit. I’ve dealt with them before and personally worked with the guys through other companies and have nothing bad to say.

I would think for the amount of money you’re looking at spending on floor prep, adhesive and new flooring, dropping a few bucks on having actual moisture testing done would be a good idea.

Thanks, good to have a datapoint with Floorcity.com.

I did an anhydrous calcium chloride test (purchased from Amazon). But are you saying that professional testing (e.g. in-situ testing) would still be useful?

 

[C.J.]

CaCl test will get you there. I was thinkin you were thinkin since you haven’t seen any moisture that there is none. I use a Tramex meter, some use the Wagner meters. Anything is better than nothing and if it alerts then you know you need to go to the next step.

 

[Incognito]

That mildew under the old vinyl (plastic) was a FAILURE that supercedes your duct tape/plastic and Calcium Chloride tests.

5lbs of MVER is borderline high for a glue down vinyl. The specially formulated adhesives nowadays can handle that and a lot worse. What will be the bigger issue is any self-leveling underlayment materials which by nature are very sensitive to moisture passing through the slab. That's why I'd trowel on the moisture resistant patch for a glue down.

 

[MSLI]

Missouri Homeowner, are you an engineer or architect ? Because Your plan and details are top notch professional. Have fun completing the project and don’t forget to show it off here when you’re done.

 

[missouri_homeowner]

That mildew under the old vinyl (plastic) was a FAILURE that supercedes your duct tape/plastic and Calcium Chloride tests.

5lbs of MVER is borderline high for a glue down vinyl. The specially formulated adhesives nowadays can handle that and a lot worse. What will be the bigger issue is any self-leveling underlayment materials which by nature are very sensitive to moisture passing through the slab. That's why I'd trowel on the moisture resistant patch for a glue down.

That was my thought too. Thanks for pointing me toward the Ardex MRF for leveling out the low spots. Is it also beneficial to use it as a skimcoat on the entire concrete floor prior to applying adhesive? Or would you just stick to using it in the low spots?

 

[missouri_homeowner]

Missouri Homeowner, are you an engineer or architect ? Because Your plan and details are top notch professional. Have fun completing the project and don’t forget to show it off here when you’re done.

Haha I am an engineer, albeit an electrical engineer so that doesn't help much with flooring. Thanks! I do have a tendency to overthink/overplan for projects. Usually serves me well, just makes the projects take 2-4x longer than they should. Will post pictures when I'm done but it will be a while (still working on framing & electrical right now).

 

[Incognito]

That was my thought too. Thanks for pointing me toward the Ardex MRF for leveling out the low spots. Is it also beneficial to use it as a skimcoat on the entire concrete floor prior to applying adhesive? Or would you just stick to using it in the low spots?

Yes, you generally use these sorts of underlayments for patches, small or big------across cracks or offsets and filling low spots. They also can be applied as a skimcoat. When circumstances dictate near perfect substrate I do one pass over all the cracks, holes and depressions and then just as that patch is HARD but not dry I can fly through a skimcoat----actually knocking down any trowel ridges or snots on that first coat before they really harden and turn to bumps than require scraping and sanding.

If your not Mario Andretti with a trowel MIX SMALL BATCHES at a clip to the precise ratio of water and take your time practicing small til your confident in working with a full bag. Rinse out your mixing pail between batches so you're not contaminating the batch with drying patch on the sides of the pail. That can suck moisture out of the following batch and sometimes generate enough heat to reduce your "working time". I always attempted to mix in a clean pail with clean, COLD water. I live outside Los Angeles. Cold water isn't always available on construction sites. CLEAN water wasn't always available either. Hard water can kick the batch off faster than you can trowel it out. That was often an issue.

 

[MSLI]

just makes the projects take 2-4x longer than they should.

When The power of preparation is respected as it Could be ! Then confidence level and quality will undoubtedly tip the scales towards success. So ! Maybe 2-4 times longer as a Rule Could be valued more than the speed and the use of that word Should

 

[highup]

Haha I am an engineer, albeit an electrical engineer so that doesn't help much with flooring. Thanks! I do have a tendency to overthink/overplan for projects. Usually serves me well, just makes the projects take 2-4x longer than they should. Will post pictures when I'm done but it will be a while (still working on framing & electrical right now).

Are you my uncle?
He's a (retired) electrical engineer also. Exact same traits. That's a compliment. It's a far better trait than guys that are so smart they won't even read the instruction.