Hopefully quick question, just can't find exact answer online.
I'm making a floating desktop using a laminate countertop (3/4" particleboard). The dimensions are ~2ft. by 7ft. I'm using shelf brackets mounted to studs - I have 5 of them, each rated to 500 lbs, directly to studs (standard 16" centers) - see here.
This should be enough weight support, however the far edge has an overhang of about 12" with no support. Since studs are 16" centers, I don't have a way of doing a mount nearby without a backer board, which I'm trying to avoid.
I've read that generally the maximum overhang for particleboard is 2-6", however that is with general 3/4" board. I'm also mounting an additional 3/4" particleboard piece under the countertop for strength - it'll be screwed/glued in, and will be like this, flipped over and looking at the bottom.
Question here is, is that 12" overhang a concern? Should I cut down the countertop more, or get a backer board, or build some other support? I really would like the full 12", and would really prefer to not have to take everything down and do a backer, but I'm concerned about sag/breakage, given how notorious particleboard is, and I'm not sure how much extra benefit I'm getting from beefing up with a second sheet of 3/4".
Thanks for any help!