I met a contractor yesterday for an esitmate to install 3/4" solid pre-finished in my old house--part has new plywood subfloor, part has original 1x6 perpendicular plan subfloor. You can see the crawl space dirt down below through the gaps between boards (1/4" max).

He says he only does gule-down these days, since nailing splits some boards, creates more waste, and eliminates having to rip-out a nail-damaged board. And besides, he adds, the Bostic Best glue is great stuff. Plus, the glue replaces the paper that you would put down between the subfloor and the new boards in a nail-down--eliminating a step.

Is this true? Is glue-down equivelant to nailing in this situation?

-Brad

Not in my opinion. And it increases the installation costs as the adhesive is way more expensive than nails. Consult the manufacturer of the flooring you are buying but my guess would be that they recommend installing their solid 3/4" flooring over a wood subfloor by nailing/stapling. That installer is in a very small minority in choosing to glue down a solid 3/4" to a wood subfloor. The exception is IF the new wood floor was a solid 5" plank or wider, then gluing AND nailing could be a viable and recommended option for installation.

You should be looking down through the 1x6's and see a plastic moisture barrier, in the crawl space, covering that dirt.

I don't know of many installers who would prefer to glue rather than nail on a crawl space & wood subfloor. As mentioned above, the adhesive is expensive, more time consuming, and much messier to work with.

I got the impression that this contractor's only experience was in housing developments, that is: slab-on-grade with the only option being glue-down. (Did I mention his comment that he does'nt even own a nail gun?)

Anyway, I found an installer who will glue over the slab (addition) portion of the home and nail to over the wood portion.

Starts tomorrow!