I am planning on gluing some engineered wood on my stairs and into my upstairs loft area. The floor and stair tread is plywood. I was curious if i need to put anything down on the plywood first like moisture or sound barrier? Or can I just glue my engineered wood directly to the plywood? I live in Socal so I don't think extreme humidity is a problem.

As far as the loft area goes, your probably ok, especially if your using urethane to glue. As far as steps go, IMHO, I never glue to treads. Whenever possible, always go with solid stair treads finished to match the floor. If not, staple or nail....there's nothing as exciting as having a piece of wood pop loose as your heading down the steps! Any other ideas on the steps out there?

Thank you bw. Interesting your comment about using solid wood for the stair tread. I had someone come out to bid by custom stairs and he recommended the same thing. Is is a steadfast rule? Does anyone have experience using a good, thick engineered wood on the stair tread with long term success (BTW, I posted a new thread asking this same question prior to reading this thread).

If you have stair problems with flooring and nosing's, then they were not properly installed. Installer error!!

Fully glue all flooring and the nosing's, blind nailing the T&G flooring, as you go and top nailing the nosing's, too.

Done many staircases with flooring and nosing's. If there were ever concerns with them I certainly would have heard about them by now.