Electrical – Multiple holes in exterior wall studs for electrical wiring

canadaelectricalreplacementstudswiring

Our home in Toronto was built in the early 70s with aluminum wiring. Since we are doing a bunch of renovations we took the decision.to replace the existing aluminum wiring with copper wiring.

The electrician has created multiple holes in the wall studs to run the new wiring (pls see attached pics). According to him as per code he can only run a single cable through each hole. The studs look a bit like Swiss cheese and we wanted to get the opinion of the forum experts.
EDIT: Please note this is an exterior wall

Is he right?
Is there not a better way of running the wires?
Should wires be protected by metal plates across the studs to prevent damage from screws/nails?
Any other things we should be aware of or pointers you can share…

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Best Answer

You can divide this problem into 2 aspects: First, protecting the lumber integrity when running wires. Second, protecting the electrical wires from damage.

For load bearing studs (there are less stringent standards for non-load bearing), here are the key (U.S. - you can extrapolate for Canada) requirements for 2x4 studs under 10 feet in length:

LUMBER INTEGRITY

  1. No holes or notches in the middle 1/3 of the stud.
  2. Never put a hole and a notch at the same height.
  3. Multiple holes (except 2 side-by-side holes only) must be drilled in the centerline of the stud.
  4. Side-by-side holes require steel plates on both faces.
  5. Holes should not be bigger than 40% of the stud width (max 1 3/8").
  6. Notches should not be bigger than 25% of the stud width (max 7/8").

WIRE PROTECTION

  1. Steel plates should be at least 1/16" thick; plates should be notched flush with the stud edge.
  2. All notches require steel plates.
  3. Holes closer than 1 1/4" to the finish surface of the stud require steel plates.

OTHER COMMENTS

  1. A "better way of running the wires" is to use either armored cable or conduit. Either of these will dramatically increase the cost of this install.
  2. Your electrician is correct in running only one cable through each hole to avoid damaging the insulation with heat (otherwise they must be derated (reduces the current flowing through them), which is impractical).
  3. Holes for the same cable should be at the same level, to reduce wire length and protect the insulation when pulling the wire.
  4. Everyone should replace their aluminium cable and connectors, which cause many structure fires around the world, kudos to you.

REF: Journal of Light Construction

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