We have an old camp on a lake in southern Maine. It dates to the 1920s. Our goal is to remodel a large bedroom (12' x 24') that runs the full length of the building on the lakeside. The floor joists in this room run perpendicular to the long axis of the room. The existing flooring (actually more like a subfloor) is 1" x 8" pine T&G that is nailed directly to the joists and that runs perpendicular to joists. We'd like to cover this with 1" x 6" red pine T&G flooring over a layer of rosin
paper.

Question is, how do we orient it to best anchor it? Ideally we'd run it perpendicular to the (sub) floor boards -
but that would be parallel to the joists and wouldn't provide much to anchor the floor to. If we lay it perpendicular to the joists - it'll be parallel to the subflooring boards. That doesn't sound good either. Is laying this flooring at a 45 degree angle a reasonable option? Are there other options?

Thanks in advance for any advice you can provide.

running on a 45 is going to be fine. I wouldnt recommend running it parrallel with the 1 x 8 subfloor. If you have 1" or more of subfloor and the joist are 16" centers or less then you'll be fine to run parallel with the floor joist (may have to sheet it with some 3/8 ply to get there) . The nails are 2" max, so with a 3/4 floor and your 1x8 subfloor going in at a 45 deg angle you only going to get about a 1/8" into the joist if that.