Knob & Tube Wiring
Pre-1950s electrical wiring using porcelain knobs and tubes with ungrounded cloth-insulated conductors.
Quick answer
Knob & Tube Wiring: Pre-1950s electrical wiring using porcelain knobs and tubes with ungrounded cloth-insulated conductors. Typical cost: $8,000–$20,000 to fully replace in a 1,500–2,500 sq ft home..
Why it matters
Most insurers will not write or renew policies on active knob & tube; replacement is a major but worthwhile expense for older-home buyers.
Typical cost
$8,000–$20,000 to fully replace in a 1,500–2,500 sq ft home.
Pros
- • Originally well-engineered for low loads
Cons
- • No ground
- • Brittle insulation
- • Insurance disqualifier
- • Cannot be safely buried in insulation
Common uses
- • Pre-1950 homes that have never been rewired
Alternatives
Modern Romex (NM-B) with grounded circuits
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Frequently asked questions
- Is knob and tube safe?
- Safe at low loads with intact insulation, but rarely meets modern usage or insurance requirements.
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