My partner and I are new to this home owning business, and really have no idea what we're doing!
Our subfloor is made of 1" x 5" pine boards installed at a 45 degree angle over the joists, which are 16" oc. There is about 1/4" between each board. We have purchased hard maple plank flooring, tongue and groove, 4 1/4 wide, 3/4" thick to be installed. The floor has been in the area where it is to be installed for over a week now, so it should be good to go. There is pre-existing 3/8" thick by 1 3/4 wide" oak flooring in the living room and bedrooms.
My question is this: can we install the new hardwood directly over the plank subfloor? If we need to put down 1/2" plywood, as some threads suggest, the new floor will be 1 1/4" taller than the existing flooring. At this point in time, we have no money to tear out the old floors to make everything level (I've just been accepted into school, so there will be no income coming in from my side, and the rest of the house needs pretty much everything done to it as well).
The subfloor planks are in great shape with no evidence of water damage. We used 2 1/2" deck screws to further attach the planks to the joists. There is some mild deflection in some of the boards in the high traffic areas when we step between the joists, and a few small areas where the floor is not perfectly level. We live in southern Ontario, Canada, so we get all kinds of different weather (not sure if that matters).
What should we do?
Also, what is recommended for underlayment? We would prefer to not use anything that contains asphalt.