I have built several of these simple but sturdy lumber racks. This one is 15 feet wide with three uprights. They are made simply from 2 x 4 ‘s sandwiched between 1 x 4’s with the cantilevered 2 x4 arms filling the gaps between the sections of 2 x4 filler. The sandwich is glued and shot with finish nails. The uprights are secured to the studs with recessed lag bolts at bottom, middle, and top. The uprights rest on the shop floor and extend almost to the 8 foot ceiling.