Hello everyone, this is my first post here.

We've been reading a lot on how to put wood-ish flooring in my house, but info is contradictory, and it seems like no one online has our situation of moist slab with asbestos mastic and wanting a floating floor (vs gluing)

So, floor situation:
* 1950s house
* slab foundation, used to have 1950s (asbestos) tile, now just has 1950s black mastic, which is 80% likely to be asbestos mastic, and we really don't want to have to wet-scrape 800+ square feet, so we want a way to go over that.
* no/inadequate moisture barrier under slab
* the carpets, and under the bed, under the furniture is musty, shows mildew spots.
* moisture tests with calcium chloride: worst spot was 5.6 lbs, best was 1.3 lbs. Done at the wettest time of year.

All the flooring we've looked at requires the moisture be less than 3lbs. Also, I just plain want to stop moisture from getting into the house and making it musty. (This will involve relining the ducts that go through the concrete, too)

From what we read, we think a floating floor is the way to go with a moist slab
But whenever I check what I'm supposed to do to moisture-proof some flooring that can be a floating floor, it involves using moisture barrier glue and then embedding the floor in the glue. Not floating it. (and that glue may not work on top of the mastic)

We read mention of moistureproofing by putting down 6 mil plastic and taping seams, (that seems so easy! Too easy? Will it work?) but so far floor manufacturers also add that you first put mastic down, and then the plastic into the mastic. Will doing just the plastic actually work with some type/brands of floor?

One site said LAMINATE is what you want in a moist situation. Then I read that it's bad for moisture, and ENGINEERED is better. I read that BAMBOO needs some moisture to stay in good shape, so would it also do better in a moist situation?

We were at Menard's and on sale right now is Tarkett brand, the Aurora line. It's a laminate with a 25-yr warranty. Reviews online are mostly good.

I just talked to Tarkett, who said to do 10 mil plastic, overlap 12", tape, and then use a moisture-barrier underlayment as well. Does that sound good, or will I be crying and tearing up the floor if I do that?

If anyone can advise us on what the heck to do, we'd really appreciate it. (We will glue if we have to, it just seems harder to get right, and slower)

Thanks

Hello zhoffritz. First off lets go over the CaCl test and how it was performed. Did you follow the test guidelines explixitly? Grind off the cutbac (with a vac attachment) down to fresh concrete? Ph test should read over 9 - 13ish for clean concrete, under that then it still contaminated. Wait 24 hours and set, then remove B4 72 hrs and retape the dish and weigh?

A reading of 5lbs/24/1000sf is pretty normal. Many roll type cushion/vapor retarders will only handle up to 5lbs so extra precation is necessary and just good to do anyway as Tarkett mentioned.
A better test would be to buy a Wagner Rapid Rh test and use in conjunction with the CaCl test if you can. This will tell you the rh in the slab. If your rh test probe is above 85 then your on the wetter side.
I'm not a believer of anything sticking to cutbac mastic residue for extended periods of time so IMO floating is the way to go. Especially with a gluedown. I float all the time out here in concrete land and use 6mil plastic all the time. Even under the roll type for extra precaution if slab moisture content is suspect. If you can get 10 mill, all the better. Make sure you run it up the wall an inch or two.

Laminate or engineered makes no difference, I float both.

Now you need to take care of the runoff from the roof, ie gutters, french drains and make sure the grade is away from the house. This will help immensely.

In worse case scenerios I use Bostik MVP4, then cover slab with 6 mil plastic. It's virtually fool proof. And I have successfully done this below grade with floating ply subfloor and solid naildown.

Thanks for your response.

For the moisture tests, they were not done 100% according to instructions. The mastic was wet-scraped off, not ground off. Other than that, I followed the instructions with timing, tape replacement, weighing, etc.. The pH was 6-7, so I guess I was measuring pH of the mastic smear.

I looked into the rapid rh test, and their brochure does a good job of selling it to people who already know what it does So, I'd drill holes in the slab, insert the meters, read them at a certain point, then...extract them? leave them there forever? (they seem to sell refill kits?). Can I call a pro to come do this for less than the $400 the kit costs?

There is more that could be done outside to help with moisture; one gutter has a dent and makes a waterfall. Also, a few inches of dirt was added to the whole yard and the house is now almost the lowest point. I have a plan for removing the front flowerbed and making a slope to a sunken garden, but that's better done in autumn. (And the wettest time of year is almost over, unless we're having one of THOSE summers)

For the 3-in-1 underlayment, could you recommend a brand or two? Some are a lot more expensive than others, and they're all "premium" (like, Roberts Harmony Premium vs Sound Solution Vapor Bloc).

Thanks again

Yea the CaCl test is void and also could not read emissions properly because of the adhesive residue.

Looks like french drains around the house is in order since the house is now the practically buried and the grading is totally wrong.

Rapid rh sensors stay in the slab and can be read for years! I do mine for 350 for 3.

Soundsolutions is good.

Thanks for explaining the rapid rh tests. Do you have flooring installed over them in some removable way? Like a secret liftable floorboard, to access the meter? That would be pretty cool.

Aargh. I really don't want to do french drains, but I would like a dry house...

All right, Sound Solutions it is, thanks for the rec.

Ha ha ha! Yes that would be nice. But they can be read again if you ever have an issue, just map it out and pull a plank. They have a graph on their website that allows you to map out the test areas. I always do it.

If I have the time I like to monitor them for about a few days to a week prior to an install.

Uzine makes a product that works terrifically well. We use their 414 turbo on all slab floors that we do. It acts as a bonding agent and a moisture mitigator. I haven't found anything that it won't stick to (wood, glass, brick, etc). They carry an epoxy version. I think it is the 480. I haven't used it but it will virtually waterproof the floor. I can give you the contact number of the southeastern regional sales rep if your interested. Plastic alone will not control the moisture well enough. You will get mold growing under it and you will have pockets of buckling where the moisture seeps out. If I were controlling the project, I would use the Uzine 480 along with 2n1 foam for a floating floor, or the 480 and the the Uzine 98 moisture cure adhesive for glue down. Whatever, you decide to do, make sure you speak with a sales rep that has direct access to a tech rep or speak directly with a tech rep. The adhesive manufactures are going to be more informed about the wood manufacturers than the other way around. This is very limited information with a lot of missing elements but hopefully it points you in the right direction.

Verhine, I didn't see where the 414 said it was a moisture mitigation system. It's a primer that bonds to adhesive residues for gluing down flooring.

The, on the 480 if you actually read these things, first they always claim you can bond to residues then on the second page, installation preperation it's scarify or bead blast. I'm certain a smooth cutbac adhesive residue does not fall under that test and is not water soluable;

Test the subfloor in accordance with applicable standards
and notices and report any deficiencies. Depending on subfloor
condition, the upper surface must have a good key
provided in all cases. Brush, abrade, grind or shot-blast to
remove any weak or soft surface layers, e.g. soft screed
edges, hard sinter, separating agents, loose residues of
adhesives, smoothing compounds, coverings or coatings.
Then thoroughly vacuum.