Glue-Down LVP in Basement. Anything BUT a straightforward install. Any help is appreciated.

[Boston_Engineer]

My home is 100 yrs old. I'm remodeling half of the basement. It's appx. 200 sq ft. The previous homeowner put down DRICORE and then did carpet on top of that. I tore it all up, revealing the concrete slab, half bare, half covered in black mastic(non-asbestos) from an old tile job. The old adhesive is not water soluble and it's very thin. It's mostly scraped down to a thin residual layer, and very well bonded to the slab.

The basement is almost 2 inches out of level over almost 20'. The perfectionist in me wanted to level the basement, but it would have been very expensive, and we're probably going to gut the house in 5 years or so. I just want a nice place to watch movies for a few years. With that said, I decided my goal is to simply flatten the floor as much as possible, and glue down some flexible LVP to keep this inexpensive.

A lot of research about how to tackle this led to this plan:

1. Put down a layer of Laticrete Prime-N-Bond to cover the black mastic/concrete and create a bondable surface.
2. Run a skim coat of Laticrete NXT Skim Lite to flatten the floor enough that the floor will adequately support flexible glue down LVP.
3. Glue down some "DuraDecor Polished Pro Silver Linings 20 MIL x 6 in. W x 48 in. L Glue Down Waterproof Luxury Vinyl Plank Flooring."

My plan seemed solid until I started reading and thinking about moisture issues. While my basement doesn't have any visible moisture issues, I know some level of moisture(is vapor the right term?) comes up through the slab because I have a gym in the other half of the basement with those padded floor tiles. They were down for about a year and recently I lifted some up and there's visible light moisture on the bare concrete and on the underside of them.

My thing is, I'm having a hard time finding factual information to reference that pertains to my specific situation and gives me a solid path forward.

Questions:

• Do I need to put some sort of moisture barrier down? If so, what kind?
• Should the moisture barrier(I'm assuming it would be a liquid-applied membrane type of thing) be applied before anything else? or would it be okay to install it on top of the skim coat?
• If I do need to install a moisture barrier all the way against the slab, is there any type of moisture barrier that bonds/works on both concrete and black mastic? Laticrete told me they don't have any product that can create a barrier over concrete and black mastic.
• Someone mentioned to me that the glue can act as a moisture barrier. 1st, is this true? And 2nd, if it's true, won't I still be trapping a bunch of moisture above the slab and below the glue causing issues for my skim coat?
• Am I just overthinking how the moisture will affect this?

I really need some help understanding what to do next. Thank you in advance.

 

[C.J.]

I would say moisture testing is required before you consider a glue down product, especially if you’re just going to redo it in a few years. Save your money now and apply what you saved to doing it correctly later. Carpet is easy and will breathe. Loose lay carpet or carpet tiles are a couple more quick and easy option. You could plop down some vapor barrier then install a floating floor. How about loose lay vinyl.

 

[Incognito]

Considering the very short term nature of this install I'd smooth out the floor with some patch and get some of the cheaper click-lock LVT. It's just got to be flat and smooth enough to keep the joints from failing from traffic and movement. Better types of underlayment (patch) have adequate polymers to bond and seal over any existing adhesive.

 

[Incognito]

I also like the ideas of carpet or carpert tile-------loose lay.

 

[highup]

NXT self leveler might be your friend here.
Maybe not applied overly thick, just enough to get it smooth.
pour it on, but spread it from the deepest side towards the thinnest side using say.... A half in by half inch square notched trowel, the type for thinset. It would flow flat to 1/4 inch thick when all is said and done. Depending on the angle of the slope, 1/4 inch of self leveler wouldn't all flow downhill like a thick pour would.
...but yeah it will still want to flow.
...or half way up, the slope, switch to a 3/8 by 3/8 trowel
.....or do it all with a 3/8 by 3/8. I'm thinking if the notches apply just enough material so that they flow together, it will at least be smooth......
I believe however we'll this goes, you could finish feathering out from there with a standard patch.
I don't know if Latacrete has a moisture emissions type primer.

 

[missouri_homeowner]

Hi Boston engineer. . .fellow engineer here (from Missouri, although I used to live in the greater Boston area)

I’ve been doing a lot of similar research as I’m planning on installing glue-down LVP in my basement. Mine is newer (1985), but does not have a vapor barrier under the slab so I have to think about moisture as well. I don’t have any residual adhesive. My tentative finishing schedule is to skimcoat the whole floor with Ardex MRF (also using it to build up some low spots), then install Armstrong Natural Creations LVT using Bruce Apex Pro unlimited-moisture adhesive.



Here are a few things other things I’ve learned through my research that might be useful. But first and foremost, I would recommend buying a calcium chloride moisture vapor emission test kit (can get them on Amazon) to quantify your moisture levels.



Moisture-resistant adhesives
There are definitely some adhesives that claim high levels of moisture tolerance. Some claim unlimited moisture tolerance (as long as there is no hydrostatic pressure), while others tolerate high (but finite) moisture levels. The hard-set adhesives listed below seem like they provide a very permanent bond and claim to form a vapor barrier that can tolerate unlimited moisture vapor. The pressure-sensitive adhesives don’t seem to tolerate as high of moisture levels as the hard-set options, but might be more forgiving if you want to pull up the LVP down the road


Here are a few examples of unlimited-moisture hard-set adhesives:

• Armstrong S-1000 (https://www.floorcity.com/products/armstrong-s1000-2gal-flooring-adhesive)
• Bruce Apex Pro (https://www.llflooring.com/p/bruce-...ier-hard-set-resilient-adhesive-10052127.html)
• Taylor Resolute (https://www.tayloradhesives.com/products/resolute)
• Note: I think all of these are the same product, just branded differently. The Bruce one seems to be the most accessible since it’s sold through LL Flooring which has a presence nationwide. The others seem to only cater to professionals

Here are some examples of high-moisture tolerant pressure sensitive adhesives:

• Mapei 399 (https://www.mapei.com/us/en-us/products-and-solutions/products/detail/ultrabond-eco-399)
• Bruce Bondlink (https://www.llflooring.com/p/bruce-...re-sensitive-resilient-adhesive-10052128.html)
• Henry 695 (https://www.wwhenry.com/product/henry-695/)

Moisture vapor barriers

You could also use a roll-on moisture vapor barrier to reduce moisture levels before applying an adhesive. Some (but not all) say that they can be used over residual cutback adhesive. A few examples are:

• Bostik Roll-Cote (https://www.llflooring.com/p/bostik...apor-barrier-coating-and-primer-10055256.html)
• Ardex VR98 (https://www.ardexamericas.com/product/ardex-vr-98/)
• Ardex VB100 (https://www.ardexamericas.com/product/ardex-vb-100/)
• Mapei Planiseal MSP (https://www.mapei.com/us/en-us/products-and-solutions/products/detail/planiseal-msp)
• Taylor Zephyr (https://www.tools4flooring.com/tayl...mSLC1DpzxP1zPP1JGO5RN-Kt09xuw5yBoCYoIQAvD_BwE)
• Taylor Sahara (https://www.tools4flooring.com/taylor-sahara-2-gal-moisture-vapor-barrier.html)

Patching/leveling

If you apply a patching or leveling solution over the concrete and apply a resilient flooring like LVP over that, I believe you’ll want a patching/leveling compound that is rated for high moisture. Otherwise, as you noted, the moisture trapped under the LVP could cause issues with the patching/leveling material. A few examples are:

• Ardex MRF moisture-resistant patching/skimcoat compound (https://www.tools4flooring.com/ardex-mrf-moisture-resistant-floor-patch-skimcoat-10-lb-bag.html)
• Ardex K60 moisture-resistant self-levelling compound (https://www.tools4flooring.com/ardex-k-60-leveling-compound-35-lb-bag.html)
• Mapei Planiprep MRS moisture-resistant patching/skimcoat compound (https://www.shagtools.com/product/m...h-compressive-strength-skim-coating-compound/)
• Mapei Ultraplan Extreme 2 moisture-resistant self-levelling compound (https://www.mapei.com/us/en-us/products-and-solutions/products/detail/ultraplan-extreme-2)

LVP/LVT brands and durability

• I got a few dozen LVP/T samples from different vendors and evaluated them for durability
• I tried the DuraDecor floor you mentioned, and it had mediocre scratch resistance
• The top contenders were Armstrong Natural Creations with their Diamond10 finish (I’m sure the “diamond” aspect is just a marketing gimmick, but it did have good scratch resistance). Karndean and Mannington also had good offerings.
• These are harder to come by and are more expensive though, so there is a tradeoff to make.

 

[missouri_homeowner]

And take all this with a grain of salt - I've only done a bunch of research but don't have experience with any of these products (yet)