What Caused These Subfloor Streaks?

How did everyone like the Thanksgiving floor in my blog last week? OK, it wasn't real. It could have been. I don't know if turkey oak gets big enough to make flooring, and doesn't have the characteristics I gave it. Roasting is a real technique used to darken some woods. What species is pumpkin ash anyway? It could be a name I gave Osage orange. It's all in the marketing.

Now back to serious. I looked at a floor this week, or maybe I should say I looked at the remnants of a floor. When I walked in, all I saw were uniformly spaced streaks in the plywood subfloor (take a look at the photo below). The hardwood flooring had already been removed. They discovered the issue in swapping out flooring for a purchaser of these brand new units. The units have been on the market for a while.

We cut into it in areas. Here's the construction detail from the ground up: unconditioned, enclosed parking area, elevated concrete slab, 2x4 sleepers with rigid foam insulation cut to fit between the sleepers, plywood subfloor, blue foam underlayment pad, then the floating hardwood floor. What's wrong with that setup? I'll wait until next week to see what others think.

The architect (my client) and his engineer are disputing my findings. Their words start with something like, "It can't be that." I'll tell you next week what they finally decide.