Installing Boxes in Unfinished Space
To wire a room with unfinished walls, such as a basement remodeling or a room addition, you’ll need boxes fastened to the framing. When attaching the boxes, be sure they protrude from the framing the same thickness as your drywall or paneling—usually 1/2 inch. Run cable from box to box and to the service panel. After you’ve roughed in the wiring, but before you install the switches and receptacles, put up the drywall on the walls and ceiling. Finish and prime the surfaces, and install the devices in the boxes.
Nonmetallic handy box - Many boxes have a series of gauging notches on their sides. Determine the thickness of the drywall and/or paneling you will be installing, and align the box to the appropriate notch as you attach it. A nail-up box like this one is the easiest to install.
Gangable boxes - These have detachable sides, so you can attach them together to form double- or triple-size boxes. To attach such boxes without special mounting hardware, simply drive screws or nails through the holes and into the framing.
Placing Boxes - In a typical room, place switch boxes 48-50 inches above the floor and receptacles 12-16 inches above floor level. Check with local codes to see how many receptacles you will need. In most cases they must be placed so that no point along any wall is more than 6 feet from a receptacle. This means that you’ll have to install at least one receptacle every 12 feet along the wall. For kitchens and bathrooms, special requirements apply.
L-bracket box - Some L-bracket boxes adjust to suit the thickness of your wall material. Others accommodate only one thickness. Hold the box in position against the framing, and drive two nails or screws through the holes in the bracket.
Utility box - Use a utility box and conduit or armored cable in an area where you don’t need a finished appearance. If you’re attaching boxes to masonry, use anchors or masonry screws.
Fixture and junction boxes are easy to install in unfinished space. Install boxes so they will be flush with the finished surface of the ceiling or wall. Do not place any electrical box where it will be covered by drywall or paneling. If there is a joist at the spot where you want the box, use a box with a hanger bracket or an L-bracket. These fasten to the joist with screws or nails. When attaching, allow for the thickness of the ceiling material.
If you need to install a fixture box between joists, use a box with a bar hanger. Attach the ends of the brackets to the joists, and slide the box into the desired position. Junction boxes protect wire connections or cable splices. Some junction boxes come with brackets. Others just nail or screw to a joist, stud, or rafter.
Regardless of the type of box you’re installing, always secure it with two fasteners. If the box will be supporting a ceiling fan or other heavy fixture, make sure it’s anchored securely enough to carry the weight. If a box has been correctly mounted but still doesn’t feel firm enough, add a framing piece and secure it to that as well.
Overhead Light Placement:
■ One pleasing way to light a room is with recessed can lights or small fixtures. To plan for a group of symmetrically placed lights, make a map of your ceiling and experiment by drawing circles, each of which represents the area lit up by a recessed fixture.
■ When you experiment with your design, try to arrange the lights so they are half as far from the walls as they are from each other. A pleasingly symmetrical pattern usually results. Start by arranging lights 6 feet apart and 3 feet from walls. Position them at least 4 feet apart. Add to your plan any suspended or track lighting you need for task illumination or to accent an attractive area of the room.
■ Don’t expect to achieve an arrangement that’s perfectly symmetrical; few ceilings will allow for that. Also keep in mind that with recessed lighting, you may not be able to put all the lights exactly where you want them because there will be joists in the way. In most cases, a less-than-perfect arrangement will not be noticeable.
Installing Boxes in Finished Space
Installing electrical work is a greater challenge when the walls and ceilings are finished. Often patching and painting can take far more time than the electrical work itself! Plan the placement so you avoid making unnecessary holes. Wherever possible, avoid making contact with the framing. Using special boxes designed for installation in finished space, you often can simply make a hole the size of the box and secure the box to the wall or ceiling surface. Before you begin, plan how you’re going to get cable to the new location.
1. Determine box location. Drill a small hole in the wall. Insert a bent wire and rotate it. If you hit something, you’ve probably found a stud. Try 6 inches to one side. If you strike wood again, you may have hit a fire block. Drill another hole 3 inches higher or lower. Keep trying until you can rotate the bent wire freely.
2. Trace around box. Some boxes come with a template that can be held against the surface and traced around. Otherwise, use the box itself and center it on the hole you could rotate the wire in. Make sure the template or box is plumb before you mark the outline.
3. Cut the opening. Carefully cut around the traced outline. If the surface is drywall, use a utility knife. If you are cutting into plaster walls, use a keyhole saw. If the plaster is crumbly, mask the outline with tape. For a wood-surfaced wall, drill a 1/4-inch access hole in each corner and use a saber saw. Run cable.
4. Fasten with side clamps... Side-clamp boxes grip the wall from behind when you tighten the screws. Pull 8 inches of cable through the box and insert the box. Hold the box plumb as you tighten the clamps. Alternate from side to side as you work so the box seats evenly. Avoid over tightening the clamps.
...or tighten wing bracket screws. Loosen the screw centered in the receptacle box until the wing bracket is at maximum extension from the back. Hold the wings against the body of the box and push the box into the hole. Tighten the screw until the box is held firmly in place.
With access from above - A ceiling box must support a fixture, so it must be securely attached to the framing. If you are fortunate enough to have attic space above, the job can be done without damaging your ceiling. Mark the location of each box on the ceiling, and drive nails as reference points. Cut the hole for the box. If there is a nearby joist, attach an L-bracket box directly to it. If not, either use a bar hanger or frame in a 2x4 support.
With no access from above - If you cannot work from above, use one of these methods. For light fixtures that weigh less than 5 pounds, use an old-work bracket. Cut the hole the size of the box, slip the bracket in, telescope it to fit between two joists, and attach the box to it. For heavier fixtures, such as chandeliers and ceiling fans, make an opening in the ceiling and install hanging hardware. With a drywall ceiling, cut out a large rectangle and install a bar hanger. With plaster, chip out a path and use an offset bar hanger.
Repair the ceiling - After checking the electrical installation, patch the ceiling. With drywall, you may be able to use the same piece you cut out. Nail the panel to the joists, and tape the seam with joint compound. For a plaster ceiling, fill with patching compound.