Hi guys
I'm curious to know if Sika ,Bostich ,etc have come up with adhesives for plywood substrates that block moisture ?

I have used Bostich Best and Sika T-55 to glue down floors to plywood and was asked what adhesives can block moisture and I don't really know .Thanks for your input

From what the guys at Bostik (not Bostich) say their single step will perform better then their specs say.

I always do that .Sorry

Paul, just wondering why you want a product like that when there's other roll products out there than can inhibit moisture. As theories go you dont want to trap moisture under your floor in the subfloor/underlayment due to rot.

I've used Sika-Bond T-21 effectively on concrete, its a step up from T-55 as it's all in one. IMO the best is the newer Ultra-Set Single Step, now the new Ultra-Set Single Step2 won't etch finish. Ultra-Set is white. Regular Single Step is brown.

I just glued some bamboo on a very damp slab with the Ultra-Set, wagner rh test was high 90's and after a month there is zero cupping. knocking on wood, not grass.

http://www.bostik-us.com/market-product ... singlestep

Stephen, what I'm trying to figure out is if there's a better way to glue down a wide plank (heart pine ) floor to a plywood sub floor than what I normally do . In glue down applications , my best technique to combat moisture is to use spacers in some rows to allow for the wood to expand .I've used Sika and Bostik and both hold great but the wood still receives moisture from below in some homes. And all I can do is leave spacer rows to give the flooring somewhere to expand to without cupping


So moving along , the customer I met told me his builder wants to install the flooring by putting down a plastic barrier and then blind nailing and then face nailing . So I told the homeowner , "one he nails through the plastic , it is no longer a barrier".

So I recommended a full spread glue down which would allow the builder to "not" face nail. And of course , no plastic between the flooring and plywood.

But my only concern is that the homeowner claims the crawl space under the room is very damp . So I'm trying to figure out if there is more that can be done than just spreading a good adhesive for this kind of install to resist moisture migration through the sub floor so that the moisture in the crawl space can be blown out of the home through the venting system he is having installed.

Single step all day..but expensive and poor spread rate.

figure 150 sf a pail if your lucky. ( with 1/2" trowel for solids)

Thanks for the info gentlemen.