I have a 2 story house on a concrete slab. Old hardwood floor was removed (parquet) and we found out it was cutback/black mastic. It is not asbestos (had it tested) but now we are looking to float the new hardwood floor. The black mastic was scraped up to a very thin layer to which the concrete slab is stained black. We had a Wagner RH (relative humidity) test done and it was 85-87% sort of high . House was built in the 60s.

We are located in the DC Metro area and right now our humidity level in the house ranges from 45 to 58%. We had some 90* days. I have a full house humidifier which I will turn on in the Winter.

The flooring we are choosing is Mirage Lock Engineered 4 5/16" in a Natural Maple. http://www.miragefloors.com/ENG/hardwood-floors-maple-natural-exclusive.php?type=collection&id=e40a6784574194538eaceea2316d050c

We want to be sure the Mirage Lock is done safely and will last along with not breaking out Mirage warranty.

I need to know what to put down on the floor to help with moisture issues along with any type of pad or underlayment. I read about the Mirage Ulti-Mat Membrane http://www.miragefloors.com/pdf/Membrane-Ulti-mat-e.pdf but not sure what else will work.

Please let me know so I can do my research and get to work.

Thanks!

That one sounds like the ticket to me! I don't know why you're looking for alternatives, or are you seeking added insurance? Have you considered Bostiks MVP? It will need additional preparation to the leftover mastic/subfloor according to their specifications.

http://www.bostik-us.com/sites/default/files/MVP4.pdf

You may also want to investigate other sources when it come to moisture...some you may not be aware of.

http://www.hardwoodinstaller.com/prepar ... esting.htm

Stauf's new CBR 970 claims you can install over cutback. Page 21 of the June/July 2013 Hardwood Floors Mag.

MVP4 would require a skim coat of ardex feather finish for any chance of it to stick.

Approved Sub Floors:Cutback adhesive, well
bonded; tested negative
for asbestos)

http://www.staufusa.com/getfile.php/d7b ... BR-970.pdf

The stauff product is pretty new they have told me it works great, haven't had a chance to see it in action although. Ive sold their 930/950/960 and I couldn't say a bad thing about any of those.
If you float it you wont need an adhesive just a moisture barrier/ pad. The mirage one is nice Id be scared to ask how much. Check out mp global they make pad/underlay for just about anything. If you have moisture issues that that pad wont control then you are better off fixing the issue before you put the floor in.

The 970 goes over cutback but up to 75% RH. I have 85%. Their sealer is not supposed to go over cutback so I would have to remove the cutback to seal from moisture then put the glue down... so not going to work

I am looking at a 10 mil poly moisture barrier (not the typical 6 mil) to put over the cutback/black mastic and then I found out that MP Global's QuietWalk is the same what they sell as Blue Hawk at Lowes... so i can get that there.

I think the issue with my moisture is that when the house was made it was just a concrete slab and now vapor barrier was put UNDER the slab. There is no standing water near the house and all the gutters are fine.

Do you think a 10 mil polyethylene moisture barrier and then the QuietWalk pad then the Mirage Lock will work?

Yes, 10 mil will work. As a matter of fact Quietwalk recommends a 6 mil under it when your moisture tests come in high.

Yup, that is what I read on their website and tech specs. I called them and asked if a 10 mil would work also with my "high" RH % and they said it would be fine as long as it was polyethylene. The perm rating for 10 mil is better than 6 mil so that is why I looked that way. Also 10 mil is thicker and ensure that over time it wont rupture or rip over the cutback (not even sure that would be an issue). I like how QuietWalk dissipates moisture if there is any issue.

I have a call into VersaSheild also for pricing... so we will see.

Does anyone have recommendations for 10 mil Polyethylene moisture barrier?

I don't agree with Quiet Walk dissipating moisture. I ripped up a floor that was over it and the pad was soaking wet although it didn't make it through the moisture barrier the fabric part was very wet.

You could also try this product found a HD

http://www.custombuildingproducts.com/p ... dgard.aspx

Called them.. they said that it will not go over cutback residue or left over black mastic that has stained the concrete.... so that is a no go.

Something is missing here. I'm surprised it hasn't been mentioned.

It's called recommended manufacturer products. And I'll bet Mirage is very aggressive in that respect. It's their nature to be almost perfect.

From their site when this the lock product is mentioned...

Procure the recommended acoustic membrane

But I see they mention this...almost like they'll allow something else...

http://www.miragefloors.com/pdf/20-Tech ... r1.0-E.pdf

Many companies will void a warranty regardless of the problem, if their products are not used. Sure you may not encounter any problems, but...

I'd stick with that underlayment they have and anything else they recommend. Don't we have any inspectors around anymore? Where's Perry?

I saw that also.. my confusion for this is... the Mirage Ulti-Mat.. is that supposed to be used as just a moisture barrier and then you put a pad over it. I called Mirage yesterday but got a VM and left a message.

Do you not run the a/c? If you have that high of r/h your a/c isnt cycling properly. sounds like its short cycling. 85% rh is like a sauna and is odd in an occupied space. Most concrete m/c test give you a measure of #'s per sf . The r/h is going to change constantly throughout the day as the outside temps change.

Redguard is only for tile and keeps moisture from wicking through it from the top, not the bottom. Used under tile on walls and floors.

I've also seen quietwalk fail but then like I said before, they require a moisture test on the slab be performed. If it is high you use six mil. They are not the only ones either. Even floormuffler recommends the same thing.

Ken, Mirage says you can use other membranes but must meet their criteria or your on yer own as any manufacturer will do. This always complicates matters cus then your fighting with two different manufacturers each claiming it is the others problem.

For greater flexibility in selling Lock products, you may also use other membranes. However, they must
meet the following minimum criteria: yata yata yata

KevinD, we run the AC and the house is at 76 degrees constantly. My humidity meter of the house is between 45% and 58 to 60%. 85% RH is the reading from the Wagner RH in-situ testing that we performed IN the concrete slab. The calcium chloride test we have not done since it is not accurate over cutback/black mastic residue.

I just got a call back from Mirage and said they have no problem using a pad that is not theirs as long as...

It is less than or equal to 3.5mm thick
Its Compressibility at 25% deflection rating is greater than or equal to 8psi when dealing with 2.6 to 3.5mm thick pad
It also must have a water vapor transmission of less than or equal to 0.6 lb / 1,000 sq. ft. / 24 hrs

They stated if I have higher than normal moisture readings to lay 6 mil poly or 10 mil poly under the pad that meets the min specs listed above.