It’s not just the nation’s power grid that’s antiquated. The wiring inside many houses is also out of date, straining to supply our ever-growing collection of electricity-hungry appliances, lighting, and electronics.
“The circuits in these older homes weren’t designed to power the many gadgets of modern life,” says electrician Allen Gallant, who has wired six This Old House TV project houses.
The signs of strain may be obvious—a tangle of extension cords and power strips sprouting from a single outlet—or lurking unseen behind walls, ceilings, and cover plates.
Protecting the Fuse Box
Fuse boxes, like the one above, are less common these days than circuit breaker panels, but they work just fine — unless someone installs fuses with a higher amperage than the wires can safely handle. That can cause the wires to overheat, damaging their protective insulation and increasing the risk of fire.
Once the insulation has been damaged, the danger remains even if the offending fuse is replaced with one that’s the proper amperage. To fix it, the old circuit must be rewired.
Hire a Pro & Avoid Fire Hazards
Some wiring problems are just inconveniences. But others can pose serious fire or electrocution hazards. If you’re buying a house (especially one that’s more than 50 years old), or if you’ve never had your wiring inspected, it’s a good idea to hire a licensed electrician to give your home a thorough going-over.
“He’ll look at the insulation on the wires to see if it’s dried out and fraying, he’ll look for corrosion in the service panel, and he’ll look to see if a previous owner did anything unsafe,” Gallant says. After that, he recommends getting a quick follow-up inspection every five years.
Don’t be alarmed if the inspection turns up code violations. Each time the electrical code is revised, old wiring is “grandfathered,” on the assumption it was installed correctly. Code only requires you to update wiring in rooms being gut-renovated.
To help you assess the state of your own electrical system, we’ve asked Gallant to identify the 10 most common wiring problems he sees, the dangers they pose, and his recommended solutions.
Remember: Anytime you work with wiring, be sure to turn off the circuit at the main breaker panel.
Common Electrical Problems
What it means: A fixture has a light bulb with a higher wattage than the fixture is designed for.
Code violation? Yes.
Danger level: High. The bulb’s intense heat can scorch or melt the socket and insulation on the fixture’s wires, which increases the risk of arcing — sparks that jump through the air from one wire to another — a chief cause of electrical fires. The damage to socket and wires remains even after the bulb has been removed.
Solution: Stay within the wattage limit listed on all light fixtures made since 1985. For older, unmarked fixtures, use only 60-watt bulbs or smaller.
2. Uncovered Junction Boxes
What it means: Because a junction box houses the splices where wires are connected to one another, a person could inadvertently damage the wires or get a shock.
Code violation? Yes.
Danger level: Minimal, as long as wires aren’t within reach.
Solution: Spend a few cents to buy a new cover and install it with the screws provided.
3. Flickering Lights When It’s Windy
What it means: Frayed wiring in the weatherhead (the outdoor fitting where overhead cables from the power line come into the house) is causing a short whenever the cables move.
Code violation? No.
Danger level: High. Aside from the annoyance, the frayed wiring can arc and start a fire.
Solution: Contact the electric utility, which may replace the weatherhead at no charge.
4. Too Few Outlets
What it means: Heavy reliance on extension cords and power strips.
Code violation? No; grandfathered in. (Today’s codes require receptacles within 4 feet of a doorway and every 12 feet thereafter.)
Danger level: Minimal, as long as you use heavy-duty extension cords, 14-gauge or thicker. (The thicker the wire, the lower the gauge number.) Undersize extension cords (16-gauge or smaller) can overheat and ignite a fire if loads are too heavy.
Solution: Add more outlets. Expect to pay an electrician about $100 per first-floor outlet and double that for second-floor work. (There will likely be a minimum charge.) This work requires cutting holes in walls and ceilings to snake the wires. Some electricians will patch the holes; others leave the patching to you.
5. No GFCIs
What it means: Increased risk of electrocution in wet areas, such as baths and kitchens. GFCIs (ground-fault circuit interrupters) shut down circuits in 4 milliseconds, before a current can cause a deadly shock.
Code violation? No; grandfathered in. (Codes today require GFCIs within 4 feet of any sink and on all garage, basement, and outdoor outlets.)
Danger level: High.
Solution: Replace old receptacles with GFCIs (about $12 each). This is a simple job that many homeowners do themselves. Electricians charge about $20 per outlet. (There will likely be a minimum job charge.) Note: As an alternative, GFCI breakers ($25) can be installed on the main electrical panel. But then every time one trips, you have to go down to the basement to reset it.
6. Overwired Panel
What it means: The panel contains more circuits than it’s rated to handle because too many single-pole breakers (one circuit) have been replaced with tandem breakers (two circuits) in one slot. (Tandem breakers aren’t the same as high-amp double-pole breakers, which take up two slots with one circuit.) A label on each panel specifies how many circuits the panel can accommodate.
Code violation? Yes.
Danger level: Minimal. It may become an issue when the house is being sold and an inspector looks inside the panel.
Solution: Add a subpanel with a few extra slots ($250), or, if you’re planning major home improvements, replace the existing panel with a larger model ($500 to $800).
7. Aluminum Wiring
What it means: You have a type of wiring, used in the 1960s and ’70s as a cheap substitute for copper, that is no longer considered safe.
Code violation? No; grandfathered in.
Danger level: High. Aluminum corrodes when in contact with copper, so connections loosen, which can lead to arcing and fires.
Solution: Retrofit a dielectric wire nut approved for aluminum wire (a pair sells for less than $1) onto each copper/aluminum connection in light fixtures. These nuts have a special grease that stops corrosion while maintaining conductivity. Make sure any replacement switches and receptacles are labeled AL-compatible.
8. Backstabbed Wires
What it means: On newer switches and receptacles, wires pushed in the back are more likely to come loose than those anchored around screw terminals.
Code violation? No. The practice is allowed, even for new construction.
Danger level: It depends. At a minimum, loose wires can cause a receptacle or switch to stop working. In the worst case, they can start a fire.
Solution: Check for backstabbed connections by removing a switch or receptacle from its outlet box. If one is backstabbed, there are likely to be more. Release the wires and attach them to the appropriate screw terminals on the receptacle.
9. Ungrounded (2-prong) Receptacles
What it means: Your house’s wiring has no way to safely conduct any stray current that escapes the confines of the wires.
Code violation? No; grandfathered in. (Today’s code requires grounded circuits and receptacles.)
Danger level: Minimal, as long as you don’t use an adapter to fit a three-prong plug into a two-prong receptacle. Doing so could destroy the device you’re plugging in, and increase the chance of electrocution.
Solution: Replace two-prong receptacles with properly grounded three-prong ones, if wiring allows it (Also, test all existing three-prong receptacles with a GFCI circuit tester to make sure they’re grounded. Rewire any that aren’t.
10. Plug Falls Out of Receptacle
What it means: Worn contacts in receptacle no longer grip the prongs firmly.
Code violation? No.
Danger level: High. Loose contacts can cause arcing, which can ignite dry wood and dust.
Solution: Replace the old receptacles as soon as possible. (A new one costs about $2.) Many homeowners feel comfortable doing this themselves. Electricians will charge about $8 or $10 per outlet, although there’s likely to be a minimum charge for small jobs.
Old Electrical Wiring: Is It Safe?
Today’s standard household wiring is a plastic-sheathed, insulated three-wire cable, universally known by the trade name Romex. But the vintage copper wiring in many older houses works just as well as the new stuff, as long as it’s in good condition and hasn’t been altered in a way that violates code. Here are some wiring systems you’ll find in older homes.
Knob and Tube
The earliest residential wiring system has a cloth-covered hot wire and a neutral wire, which run parallel about a foot apart. Ceramic knobs anchor the wires to the house framing; ceramic tubes are used where wires cross or penetrate framing.
Caveats: Cannot be grounded or spliced into a grounded circuit. Its soldered connections may melt if too much current flows through them. Rewire or disconnect any circuits covered with building insulation; it causes this wiring to overheat.
Armored Cable (Bx)
The successor to knob and tube. A flexible steel sheath covers hot and neutral wires, which are insulated with cloth-covered rubber. The sheath provides a ground, so grounded receptacles are easy to retrofit.
Caveats: Sheath must be anchored securely to a metal outlet box. Check condition of insulation every five years or so; it degrades over time, as shown above, or if too much current is allowed to flow through the circuit.
Two-Wire Plastic-Sheathed Cable
An early PVC-insulated (Romex) wire.
Caveats: Plastic is easily damaged. Grounded receptacles cannot be retrofitted to this wire.
Where to Find It
Electrician: Allen Gallant
Looking for more help with repairs around your home? A home warranty may help. Check out the This Old Houses Reviews Team’s in-depth reviews on: