Running New Wires through Old Walls
With an assortment of tools, a few tricks, and a little luck, you can make electrical cable go where you didn't think it could.
Synopsis: Remodeling projects often include moving or adding an electrical circuit, which in turn requires running wires blindly inside walls and between floors. This article gives an overview of the basics of snaking wires, as seen from the viewpoint of several experienced electricians. Highlights of the article include a look at the specialized tools that electricians use to make the work easier, plus tips on safety and techniques.
Renovating a house is akin to surgery: calculated mayhem, followed by judicious repair and renewal. Sometimes the job is of the minor, outpatient variety, and sometimes the job is more like a heart transplant. Electrical renovations fall somewhere between the two extremes, not life-threatening to the patient, but tricky work just the same.
Like doctors, most electricians believe in doing no harm, at least as it applies to existing walls. (Why spend more time cleaning up and repairing the damage?) The veteran electricians I talked to all winced at the thought of making big holes in plaster walls, and only as a last resort would they remove baseboard or trim to run a wire. Instead, they’d rather practice noninvasive surgery and drill a series of holes hidden behind interior walls to create a new path for wire. The trick then is to thread a flexible rod, string, or steel tape back down that new path and use it to pull the wire through. Fortunately, the electrical code doesn’t require that you staple these wires to the framing.
To learn about the art of snaking wire, I spent time watching different master electricians practice their craft. These guys rely on a number of special tools, many of which are explained here. But what really makes them successful are large measures of creativity, patience, and a thorough understanding of a particular house’s structure.
Start a tiny hole
Determine the position of the outlet or switch in the wall. To locate the corresponding spot in the basement, drill down in a convenient place (between two floorboards, for instance, or next to the baseboard) with an insulation batten. The long thin wire batten is easy to find and leaves a small hole that’s easy to patch.
Downstairs, find the wall-plate location by measuring over from the protruding wire batten. (You also can find the plate by locating the nail ends that anchor the plate to the floor.)
From the basement, use a 3⁄4-in.-dia. bit, and drill an access hole up into the stud bay.
Reach up from the basement into the bay with a fish tape; have a helper grab the tape from above and pull up. Fishing longer runs may require repeated attempts to snag the end of the tape. Thin, flexible steel tape is the most common fishing tool. Many electricians cut two lengths from a reel, about 12 ft. and 2 ft. long, and use them for the majority of their work. The grabbing end of the tape is bent back onto itself into a hook. Another common method is to drop a weighted line from above down into the basement and reverse the procedure.
From Fine Homebuilding #176
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