Originally Posted by Red Squirrel
I would go at least 2x6. But if you really must use 2x4 because of some clearance issue or something, set them on every 8" instead of 16". I don't know about the legality of that though.
I'm with you. Even 2x6 at 10 feet is going to flex a bit.
And finding the right species of lumber in the right grade as GBR suggests might work seems like tempting fate. Too close to the limits.
The lumber costs are pretty minimal to upgrade to a 2x6, in the overall cost of building out an office.