The Finish Work

Electrical boxes must be set so they’re flush with the surrounding wall or ceiling when wood framing is used for construction (NEC Section 370-21). The gaps around the box cannot be greater than 1/8 inch; anything greater must be filled with patching plaster. The code wants to diminish the possibility of a fire spreading if a device or fixture has a short circuit. Boxes are secured by
…
➤ Nailing to the stud or joist.
➤ Plaster ears.
➤ Snap-in brackets.

Metal boxes can be used with …

➤ Nonmetallic cable.
➤ Armored cable.
➤ Metal conduit.

Nail-on plastic or nonmetallic boxes can be used with nonmetallic cable. Others are rated for use with plastic conduit.

Insulation Obstacles

Insulation is great for maintaining your house’s temperature, but it’s terrible to pull wires through, especially the blow-in cellulose type. Worse yet is solid foam. You’ll never get a cable through that stuff. If you have insulation and you’re not inclined to pull your walls apart and remove it, consider …
➤ Using some form of raceway or conduit.
➤ Installing floor receptacles.
➤ Looking for alternative locations on interior walls instead of exterior walls.
➤ Going through closets or cabinets.

Get Your Drill Out

The smaller the drill, the tougher the job when drilling holes for running cable through your house’s framing. I’ve already discussed drills. When access is limited, a rightangle drill can be very advantageous. Your holes must be drilled at least 11/2 inches from the edge of the stud or joist! This is to avoid damage to the cable from drywall nails or screws or any other fastener used to attach anything to a wall or ceiling. If the studs are exposed, you should install a metal nailing plate in front of the hole for added protection.

The Woodwork Comes Off

Cutting very visible holes in your walls and ceilings (and repairing them later) might not be at the top of your list of fun projects. If you have wide baseboards, you might have a way out. You have to decide if it’s less of a mess to carefully remove a length of baseboard, pull the nails, reinstall, and possibly repaint it. With the baseboard out, you can drill behind it and not bother with patching up the plaster or drywall. This only works with wide baseboards (six inches wide and wider). With narrow baseboards, you would have to drill too close to the bottom of a stud, which could weaken it.

No Access, Now What?

Finished basements and attic spaces (or service panels located in finished garages) call for a more deft approach to your wiring. You have to decide if you should …

• Run part of the circuit in conduit across the basement or garage ceiling.
• Run conduit on the outside of your house and then into the walls.
• Tear into the walls and ceiling at regular intervals, exposing the studs and joist to run the cable.

Most studs and joist are spaced at 16 inches on center (which means the center of the nailing side of one will be 16 inches from the center of another). The spacing offers predictable nailing surfaces for drywall and interior trim, especially baseboards. If you have no other way of getting into the wall or ceiling, you’ll have to open up the wall on each side of the studs and joist until you’ve reached the locations for your new boxes.

Dealing with boxes in ceilings

Light fixtures and fans require an electrical box installed in the ceiling. (Fans are heavy and require special boxes. If you use anything else, the fan might fall out of the ceiling.) An unfinished attic gives you plenty of access to the joist. All you have to do is drill a small pilot hole at the proposed box location into the ceiling from below and poke a section of metal hanger up and into the attic (check the approximate location in the attic first for obstructions and wires). This will enable you to see if there are any obstacles in the attic such as existing wiring or framing that might be in the way of a box. Once you’ve established that the location will work, you can either …

• Cut the round hole for the box with a hole saw.
• Use a keyhole saw or a drywall saw for cutting the hole.

Ceiling boxes can be either nailed to a joist or attached with bar hangers. Nailing to a joist is simpler, but your light might fall between two joists and thus require hangers.

How to deal with plasters?

Plastering is quite a craft. Older plaster jobs consist of three coats of material applied over wood or metal lath. Some old plaster (Victorian homes come to mind) is a little on the crumbly side. If you’re careful cutting through it, you’ll keep your repairs to a minimum.
To cut through plaster …

1. Determine the location of your new box (next to a stud if possible, but do your initial cutting at least a few inches away to make sure nothing gets in the way of the saw blade).
2. Place a drop cloth or a piece of plastic on the floor.
3. Drill a test hole so you can determine where the edge of the stud is located. (Ignore this if you’re not going to be near a stud.)
4. Place the front of your new box against the plaster, and use a pencil to draw around it (ignoring any plaster ears) to give you a line to cut into. You can apply masking tape around the outline to help keep the plaster from chipping when you cut.
5. Drill a hole in each corner to provide starter locations for the keyhole saw or scroll blade.
6. Hold a straightedge against the pencil lines, and score the plaster several times with a sharp blade.
7. Carefully saw through the lath in smooth movements. Go through about 7/8 of the way on one side and then cut the other side completely, returning to cut the remainder of the first side. This prevents the lath from excessively shaking the plaster.

If you have metal lath, you can’t really saw through it. You can try to chisel it out, but this can cause further cracking if you’re not careful. I’d just drill as many holes as you need, following the pencil outline to minimize the chiseling. Once the metal lath is exposed, cut through it with tin snips and smooth out the plaster with a saw blade or a rough file, or tap it with a small hammer.