I have a concrete slab and want to put 3/4 wood flooring on top. I'm going to lay a plywood subfloor and want to know if 1/2 inch plywood is good enough. I plan on nailing down the wooden floor.
Agree with diceless that a floating engineered wooden floor is more normal over a concrete slab. Thermal movement in fully fixed wooden floors causes problematical expansion/contraction more often than not.
Even using stable wood, the humidity in the room will change season to season, as will the temperature of the underlying/surrounding structure, all can affect the appearance of the wooden floor.
Was there a specific design/idea you had in specifying the ply subfloor?