Plaster and Drywall Repair

Plaster is applied wet and is forced into wood or metal lath. As it dries, the material that has oozed onto the back side of the lath forms plaster keys that hold the plaster in place. After you’ve cut the lath away to run your cable, you have to either patch in new lath for backing or use a small section of drywall for your repair. The cleaner your access holes, the easier your repairs. You might have to repaint the entire wall (maybe the rest of the room, too), depending on how much the paint has faded.
Patching a hole in drywall is a little easier than doing the same with plaster. All you need to do is …

• Even up the hole in the wall by tracing an outline an inch or so in each direction. Take these dimensions and cut out an even rectangle or square of new drywall.
• Hold the drywall patch against the wall, trace around it, and cut out an even, level hole.
• Cut a second drywall patch two inches larger in each dimension.
• Drill a hole in the center of the larger patch and pass a cord through it, knotting one end so it holds tight against the hole.
• Apply construction adhesive to the outer two inches of the face of the patch.
• Insert the patch into the wall and align it with the hole. Pull it tight to the wall with the cord.
• Tie the other end of the string to a pencil or a small piece of scrap wood, and twist it until the patch holds tight. Tape the end of the wood to the patch so it doesn’t slip. (You also can screw through the wall and secure the patch.)
• After the adhesive has set, test the smaller patch for fit and trim down the edges if necessary. Drill a hole in the middle of the patch.
• Pull the cord through the second patch, and glue the smaller patch to the larger patch, securing it by twisting the cord.
• After the patch has set, cut the string and push any excess back into the hole. Apply fiberglass drywall tape to the edges, and cover the patch with a thin application of joint compound.
• When it’s dry, lightly sand the patch with 100-grit paper and apply a second coat of joint compound, spreading it slightly beyond the tape. Sand it when dry and apply a third coat if necessary.
• Run your hand over the patch after each layer of joint compound has dried. (You don’t want to end up with a lump.)

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.