So I have a workshop that consists of a long double garage, 22'x40'. The rafters are 2x6, 24" oc. The joists span 22'. The joists are open, so there is no load from drywall or otherwise. The roof is metal, so it's lighter than shingles. Walls are standard 2x4 16" oc, with a double top plate, single bottom plate.
I have just put about 370 bf of hard maple up there, along with another 400-500# of 2x12 southern yellow pine. Total weight is probably about 1,500#, assuming a weight of 3.8#/bf for the hard maple. The load spans a space about 8'x9', or about 72 sq feet, over 5 joists.
My understanding is you can figure about 40-50 lbs per square foot, which would be about 3,500# in this case.
So I appear to be under the load limit for the span.
Is this valid, or should I be considering doubling up the 2x6 joists by sistering another 2x6 to each of them?
I'm also considering moving the load away from the middle of the span to the outside. It's in the middle because that's what seemed the easiest way to get it into the joists, and the added weight didn't seem like an issue before this.