California has a lot of older housing, and with it two wiring types that worry buyers and insurers: knob-and-tube and aluminum. Neither means the house is about to catch fire. Both deserve a careful look.
Knob-and-tube wiring
Used into the 1940s, knob-and-tube runs individual conductors through ceramic knobs and tubes. Look for it in attics and crawl spaces. Its drawbacks are well known: no ground wire, insulation that turns brittle with age and heat, and a design that relies on open air to stay cool, so it should never be buried in attic insulation. Decades of amateur splices are often the bigger hazard.
Aluminum branch wiring
From the mid-1960s to the mid-1970s, some homes were wired with aluminum instead of copper. Aluminum expands and contracts more than copper and oxidizes at connections, so terminations at outlets, switches and fixtures can loosen and overheat. Warm cover plates, flickering lights and a faint hot-plastic smell are warning signs.
What are the options?
- Evaluate first. An electrical inspection documents what's there and what condition it's in.
- Repair connections. Aluminum circuits can be made safer with connectors rated for aluminum at every termination.
- Rewire in stages. Kitchens, bathrooms and the heaviest circuits first, the rest later.
- Whole house rewiring. New grounded copper circuits throughout. See whole house rewiring.
What rewiring involves
Most cable is fished through attics and crawl spaces, with small access holes where needed. Homes are usually rewired in sections so the owners can stay. It's also the natural time for an electrical panel upgrade, added outlets and hardwired smoke alarms.
Insurance and resale
Some insurers decline or surcharge homes with active knob-and-tube or unrepaired aluminum wiring. A written report and a clear plan often make the difference in a sale.