Solid Hardwood, Engineered and Laminate Flooring - subfloor question??

We are building a new house....and this seems like a stupid question, but here goes.................We have Avantec plywood down as the subfloor for building on. We're going to put down Engineered wood in the next few weeks. But someone just asked if we are planning to put "another subfloor" down on top of the Avantec before installing the Eng. wood. I wasn't sure how to answer as I had thought that the wood flooring would go directly on the Avantec.......what am I missing in a new construction???

I've seen this in my house and in others... after the floor joists the builer will lay down a leyer of decking (plywood) and then the walls on top of that. After the walls are up they will come back with a second layer. In mys house is was a combination of MDF or plywood (depending on what the finished floor was, carpet over MDF and harwood/tile over plywood, unless it was in a bathroom then it was plywood). If the decking is thick enough then there should not need to be an aditional layer of plywood for the subfloor.

Depends how stout that floor is now. Call the flooring manufacturer and see if they approve it as a subfloor for their flooring.

I do mainly remodels and not new construction for builders, and have yet to come across this subfloor material down here in Texas.