I am renovating a mudroom that was originally built as a porch so the concrete slab is pitched for drainage. I installed 5/4 X 4 sleepers, 12" on center, shimmed every 10-12" to level, and am going to intall 3/8" engineered hardwood. My question is should I glue it down to the sleepers or install it as a floating system? And what kind of glue should I use? The room is only 3 1/2' by 6' so it is a small area. And do I have to put down a plywood subfloor or are the sleepers enough to hold down the flooring in a glue down installation? I tested a few flooring pieces before installing the sleepers for "give" and came up with the 12" spacing so the flooring wouldn't have any bounce when walked on.

If I am correct, engineered floors are not to be installed over "sleepers". They require a subfloor. If your sleepers are spanned that close, consider a 3/8" or 1/2" plywood, to which you could glue or nail that 3/8" engineered flooring.