Admitted "newbie" here - but I'm quite handy and try to do adequate research...

I want to lay up a 3/4 X 3-1/4 maple floor in a large room (about 25 feet by 10 feet), and have a few questions:

This is on the 2nd floor of an air-conditioned home, so I don't expect moisture control to be a big issue.

Q1. EXISTING SUBFLOOR:
3/4" X 5" planks, laid diagonally across joists
5/8" X 3-1/4" pine, T&G, laid along long axis of room.

If floor is level, can I keep the 5/8" pine - plan to use 2" staples, which should go into both layers, tying them together?

Q2. DIRECTION:
If I keep the 5/8", I would assume that I need to go perpendicular to it, or at least diagonally. (The wife wants me to run the long way in the room - I suspect that this would cause problems, but want to be able to provide a good explanation.)

Q3. WASHER ROWS:
With maple, in a room this size, would it be a good idea to throw in a few 1/16" joints every 6' or so? Since I am installing in Summer, I would tend to expect contraction, and not much expansion (winters around here are dry, and Summer / early Fall are dampish).

1) You may lay a new floor over your pine floor. However, there are some "rules" to this. And a 2" staple will not go very far into your bottom layer, diagonal subfloor, maybe 1/4". So don't condider this tying them together.
2)You are correct. You will need to lay a new floor at 45 to 90 degrees to the existing. Why? Because it is the correct way to do it for the floors to perform well.
3)Go ahead. no harm. Maple is a mover.

BTW, If it were me. I'd tear out that pine floor, renail/screw down the diagonal subfloor and install the maple over that longways in the room and at 90 degrees to the floor joists.

Thanks Gary,

Actually, we are going to do it just as you suggested, and tear out the 5/8" pine, then run the new maple perpendicular to the joists, which is lengthwise in the room.

Just a few more related questions:

Q4. The room is attached to a hallway - I am starting at the West wall, and working Eastwards -- The hallway enters the room at the East Wall, proceeds East for about 10 more feet, then turns South for about 6 feet. From the West wall of the room to the East wall of the hallway is about 22 feet. What would be the best way to allow for movement of the wood in the hallway? (I will have room for the shoe molding along the East wall of the hallway.)

Q5. I'm a little worried about expansion room, but my glorious wife who knows all insisted on painting the baseboards (without shoe molding) before floor install. The gap under the baseboards is quite deep (about 1.5 inches), but is only 5/8" high - while the new floor is 3/4". What do your guys think about tapering the edges & ends of the strips where I start, and at the ends, so that expansion can take place under the baseboards, and I will not see a gap at the shoe in the winter? (I know I can't do this for the last boards, so I plan to leave 3/8")

The idea that the floor will expand and contract a lot around the edges is really a bunch of crap. In all my years of doing flooring, the ONLY time a floor has moved more than 1/4" or so around the edges is when it has been FLOODED, and I mean under water for quite some time. Shrinkage is the same deal. If the floor shrinks, it will do it throughout the floor between all the boards, unless the finish has panelized some of the floor. It just never happens only at the edges. THE exception is floating floors. Expansion space for floaters is quite important. But for a nail down floor, 1/4" to 1/2" is more than adequate and baseshoe will easily cover that gap. Forget that tapering idea. If you really want more expansion space, get a jamb saw and under cut all the baseboards up to 7/8". And I didn't really get that east, west, south thing. I understand you're trying to give us directions of the floor layout but personally, I don't use those (maybe I should). I use terms like right and left and right angle and diagonal and 180 and so on.

Gary,

Thanks again for your helpful advice.

The floor is nailed down, and feels solid as a brick!

I undercut the baseboards in the hallway with a chisel (lots of short spans between doorways, with lots of ins/outs in the doorways). Doing this gave me a lot more leeway in cutting the strips, since I could slide them under the baseboards a little (particularly, where I had to meet the stair nosing with the ends of the strips).

Now, all I gotta' do is rent a sander and have at it, apply finish, and install new shoe moldings.