In my backyard there is an old bank barn of sorts. The top story is 50' long and 15' wide. The bottom story is about 35' long and 15' wide, so part of the second story is on the top of a hill and has a crushed stone floor. I plan to store my garden tractor and a few other outdoor tools on the stone floor side of the second story, since my garden is located right next to it. I plan to put my woodworking equipment (tablesaw, bandsaw, molder, workbench, etc.) on the wooden floor of the second story.
I have most of what I'm going to do figured out, but I'm not sure what to do with the floor of the second story. It is just wide enough that I think I either need to go with 2x12 floor joists, or if I go to 10x2 I think I would need a center beam under the joists, and then of course some sort of posts every few feet to support the beam, which I want to try and avoid. I am planning on putting the joists on 16" centers, but would go to 12" if it changes anything. I plan to use 2x6 tongue and groove as the flooring on the second story.
So what do you guys think, will 2x12 span the 15' with no problems, or should I use a center beam, or could I even go with 2x10 and span the 15'? If I need to use a center beam, can I just go with 2x8 for the joists? I would prefer to avoid the hassle of the center beam and posts, and I don't want to go with the engineered I-beams for the joists as I'm attempting to keep the costs down. Although, I have no idea how much engineered 15' I-beams go for.