DO-IT-YOURSELF : Saving Wall Work by ‘Fishing’ Electrical Cable

Have you wondered how to add a switch, light or receptacle to your home with all those finished walls, ceilings and floors concealing the wiring?

Well, take heart.

With some careful measuring and a complement of luck, you can easily “fish” cable through ceiling and wall cavities, with little or no drywall repair.

Fishing cable, as it’s known, is not new. Electricians have been upgrading electrical systems in this manner for years, and you can do it too. Although the job is time-consuming, it’s not that difficult.

In many cases all you need to fish electrical wire are a cut-in box, sheathed cable, a screwdriver, a utility knife and drywall. In some cases a length of sash chain is handy.

For a short run, a piece of coat-hanger wire will serve as a fish tape. For longer reaches, a factory-made fish tape will save you hours of frustration. It costs about $20.

Fish tape is a thin, coiled steel ribbon with a hook on one end. It’s rigid enough to push through a wall cavity yet flexible enough to make tight-radius bends.

Some circuits are easy to expand. If you want to add an interior living room wall, check the wall’s back first. In many cases, you can pull power from a bedroom receptacle on the wall’s opposite side.

To do this, start by measuring carefully from a common feature on the wall, such as a door. The existing receptacle box will be mounted on a stud. The new box, known as a cut-in box, will not be mounted on a stud.

To determine where to put the cut-in box, poke a putty knife between the outside of the receptacle box and the edge of the drywall. Do this on both sides of the box. The putty knife will go in up to the stud on one side, but on the other side it will not hit the stud. This is the side on which you install the cut-in box.

On the opposite side of the wall, mark and cut the opening for the cut-in box a few inches from the existing box. Run the wire from the existing box to the opening. Push the wires through the cut-in box and install the box in its opening.

Now install the receptacle in the box and check that the receptacle is working properly before installing the cover plate.

When extending the cable along a wall, in most cases you will have to run the cable from under the house or the attic.

If you work in the attic, move the insulation aside to find the top of the walls through which you will bore holes to run cable. The wall will run parallel to the ceiling joists or perpendicular to them. If it runs parallel to the joists, look for a drywall nailer (two 2-by-4s or one 2-by-8) that appears to lie on top of the drywall. A wall perpendicular to the joists is evident by the horizontal 2-by-4 that forms the top of the wall.

After measuring carefully from a reference point, bore one hole to tap into the circuit and another to run the cable. Next, lower an eight-foot sash chain into the stud space from above. Secure the chain with locking pliers.

Poke the fish tape through the box opening (the one you are pulling power from) and snag the dangling chain. Pull the chain into the box and attach the new cable to it. Pull both into the attic. From the attic, feed the cable into the next hole, and push it down to the new opening.

Do not lay cable on top of the ceiling joists. If the cable runs across a joist, bore a hole through the joist and run the cable through the hole. If the cable runs parallel to a joist, staple the cable to the joist’s side. Space staples four feet apart.