My client just had a Mirapatch concrete overlay done to flatten his concrete slab (above grade) for a glue down install of engineered wood floor. My question is: should the overlay be primed or sealed prior to using urethane floor adhesive? Is latex primer recommended? An epoxy moisture sealer? There are no moisture problems and overlay is fully cured.
Thanks for any help you can provide!

Which Mirapatch product was used? They offer several different types of overlays/underlays, and I don't believe that all of them are suitable for gluing hardwood to.

Generally speaking, the only sealer/primer you would want to use is one recommended by the adhesive manufacturer.

Anyone do a moisture test on that yet?

Yes, no moisture was found. Slab above grade, and 60 years old, cured and no signs of condensation under 6mil poly after 2 days

I believe it was Mirapatch DP, a trowel grade overlay.

You know the ole mat test is not really used anymore cept for some manufactures that want to risk replacing a few floors just to sell more and make it easier for DIY'ers.

Was the concrete darker than the unexposed? What does your manufacturer and adhesive manufacturer say to do for moisture testing?

Mirapatch DP is a portland based product, and they say it has a PSI of 5000, so technically speaking it is suitable for installing over. But, fyi, I had one other inquiry to install on top of it, and Miracote said they advised lightly sanding it before gluing directly to it.


Like Stephen said, the mat test doesn't tell you a whole lot. You really need to do more accurate moisture tests, make sure they are within the approved range for the adhesive manufacturer, and document all of your readings. If there's no elevated moisture condition, a vapor barrier is not necessary, but just because a slab is dry today, doesn't mean it will be tomorrow or next month, so you may still want to consider using a vapor barrier compatible with your adhesive.

Is that what it is ? I was looking at the pdf's on it. Interesting product that can be used as a surface all it's own.

The part about wetting the surface prior to installation brings up some flags. I would definetly throw down some cacl tests on that stuff. Heck, a 3 pack of taylor cacl tests cost only thirty bucks. Cheap insurance there buddy.