Im working on a closet sized bathroom. I want tile on the floor. The square footage is only about 7'. It's an old house. Under the old asbestos tiles I torn up, is 1x3 planking. It's tight and in good shape (but not level for sure). I planned on just thinsetting then throwing down 1/2 inch hardyboard, then tile. The drywall is already up, so I don't think I have room to throw down plywood. Would it be needed in such a small space?