I'm redoing my kitchen and am going to run the hardwood floors through the kitchen (it's tiles right now). After pulling up the tile and backerboard, there is a total of 1 1/4" of subfloor. Looking in the basement, i can see 7 1/4" wide planks that run perpendicular to the joists. I think there is plywood above the planks. I'm trying to get the floor level so the new hardwoods in the kitchen will match up evenly with the hardwoods in the rest of the house.

Couple of questions.

Any body know the depth of the planks that are above the floor joists?

Should i put the hardwoods on top of those planks, or is there a need for plywood in between??