This occupation is included in the larger group of pipelayingfitters, pipefitters, and plumbers.. The median wage for this groupis $4,781 per month ($27.58 per hour). Half of all of these workersearn between $3,602 and $5,651 per month ($20.78 and $32.60per hour).
When supporting joists that span 12 feet with no overhang beyond the beam, a double ply beam can span in feet a value equal to its depth in inches. A double 2x12 beam can span 12 feet; a (2) 2x10 can span 10 feet and so on.
Most of the 24' spans I see use 2x4 bottom chord-I'd up that to a 2x6 for insurance. Most also use 3 each 8' 2x4 for the bottom-I'd use 2 x 6 x 12 with a single splice plus the gussets at the angles. I'll bet if you tried to buy a 2 x 4 x 24 these days it'd look more like a corkscrew than a board.