The original wiring (1994) is along the best route where wires are stapled at the top of the interior wall plate above the finished drywall. I want to run 4 new circuits, but there is no room to staple new wire, and I don't wish to drill all the floor joists. Can I staple new wire to the bottom of a running board mounted perpendicular across the floor joists and about 6 inches away and parallel to the original run?
This is finished basement with an unfinished ceiling and the run area is where the plumbing, air etc. also run across the joists and hang well below the proposed running board. I consider to be not subject to damage. While unlikely that the ceiling will ever be finished in this area, any ceiling would have to be installed at least 6 inches inches below any wiring to clear the existing services.
If so what would be the required staple spacing on the running board? As an alternative, can I secure the new wire to the bottom of the running board using a plastic MultiCable Staple (NEC 300-4-(d) compliant) which snaps closed, or are these only for horizontal or vertical cable support, you know, not cable supported hanging down?
If I decide to drill the joists, can you give me a guide for the max number of cables (12ga NM) through one hole, what size hole for x number of cables gives good clearance, and avoids "bundling" concerns, and are any grommets and what kind are required though timber joists? I know about drilling center and so on.
Also, the original wiring occasionally put two wires under a single staple where room was scarce. Are max 2 wires under a staple still permitted when necessary, and would a preferred method be to stagger which 2 wires are under one staple, i.e. not run the same 2 wires continuously under one staple to avoid bundling over more then 24"? I live in Western MA.