What does repairing damaged wiring in a wall involve?

Repairing damaged wiring inside a wall is work for a licensed electrician. The job usually means finding the damaged section, opening the wall to reach it, replacing or properly joining the cable, testing the circuit and closing the wall again. The Consumer Product Safety Commission's guide to home wiring hazards says that finding specific defects in electrical systems and repairing them are jobs for qualified electrical professionals.^[1]

How you know wiring in a wall is damaged

Damaged cable behind a wall rarely announces itself. The signs show up at outlets, switches and lights: lights that dim or flicker, sparks or flashes anywhere in the system, sizzling or buzzing sounds, switch plates or outlet covers that are hot to the touch or discolored, the smell of hot insulation, and any shock, even a mild tingle.^[1] A breaker that keeps tripping on one circuit also points toward a fault somewhere on it.

Common causes include a nail or screw through a cable during a renovation, rodent chewing, water, an old cable that has dried out and cracked, and a connection that has worked loose. Unseen damage is not a small risk. Nearly half (47%) of the residential building electrical fires where equipment was involved were caused by the building's wiring.^[2] Inside the walls, wiring that is overloaded heats up and damages its own insulation.^[2]

What the repair involves

The details change with the house, but a licensed electrician's visit usually covers these stages.

Diagnosis. The electrician asks what you saw, which outlets and lights are affected and what the breaker did, then works out which circuit is involved. They check the circuit and its connections to narrow the fault down to a stretch of wall, ceiling or floor. This can take longer than the repair, especially in a house where several rooms share one circuit.

Opening the wall. Once the fault is located, the electrician cuts an opening in the drywall or plaster just large enough to reach the cable. In a finished room with plaster, a masonry wall or insulation packed around the cable, the opening takes more effort than in a simple stud wall.

Fixing the cable. A short damaged section is typically replaced, or the cable is joined in a way the electrical code allows. Ask the electrician to explain which, and where any connection will be. If the insulation is brittle along the whole run, the sensible fix is to replace the run, not the damaged inch. For the larger question of old wiring, see how long house wiring lasts.

Testing. After the repair the circuit is re-energized and checked, including the outlets, switches and fixtures on it, before the wall is closed.

Closing up. Patching drywall, texture and paint is a separate trade. Many electricians leave the opening cut but unpatched, so ask what the quote covers.

Permits and inspection

Virginia's Uniform Statewide Building Code requires a permit to be obtained before starting installations or alterations involving "electric wiring".^[3] The same section says applications for emergency construction, alterations, or equipment replacement are due by the end of the first working day after the work starts.^[3] Whether a particular repair falls under that rule is the local building official's call, so ask the electrician and, if in doubt, your county or city building department.

DPOR's consumer guide says the contractor should apply for and obtain any necessary building permits, that this should be spelled out in your contract, and that you should not let work start until you have copies of the officially issued permits.^[7]

What affects the price

The cost depends mostly on how hard the fault is to find and reach, how much cable is damaged, whether the wall is plaster, masonry or insulated, whether the old wiring is brittle, and whether patching is included. Our guide to what electrical wiring repair costs in Virginia explains these and what to ask for in a written quote.

When to call a licensed pro

For this whole job. Virginia law defines a tradesman as anyone who works for the general public for compensation in the electrical, plumbing and HVAC trades.^[4] No individual may work as a tradesman unless licensed, though someone working under the supervision of a tradesman licensed in that specialty does not need their own licence.^[5] The Board for Contractors requires a master tradesman licence as a condition of licensing an electrical contractor.^[6] Check the licence before you agree to anything.

If the circuit is giving off sparks, a burning smell or hot cover plates, read when a wiring problem is an emergency first. Loclis lists DPOR-licensed electrical businesses with their licence number and class: browse electrical repair services or read more electrical repair answers.

To get prices for your own wall, describe the job once and licensed local electricians quote it.