Knob and tube wiring: what it means on your inspection report

What knob and tube wiring is

Knob and tube was the standard residential wiring method in the United States from roughly the 1880s through the 1940s. Two separate conductors, a hot and a neutral, run through open air rather than inside a shared cable. Ceramic knobs hold the wires away from framing, and ceramic tubes protect them where they pass through joists and studs. The insulation is rubber and cloth, not modern thermoplastic.

Homes built before about 1950 in Atlanta, Marietta, Savannah, and most older Georgia neighborhoods may still have live knob and tube circuits, often in an attic, a basement, or a crawlspace that was never touched during a cosmetic renovation.

How to identify it yourself

• White or off-white ceramic knobs nailed to attic joists with a single wire looped around each one.
• Hot and neutral running as two separate wires several inches apart, instead of one jacketed cable.
• Two-prong outlets throughout the house, with no ground slot, and no GFCI protection in the kitchen or bathrooms.
• Cloth-wrapped wiring entering an older fuse panel, or splices wrapped in friction tape rather than housed in a junction box.

Why it is a safety concern

Knob and tube itself was well engineered for its era. The risk comes from what the last hundred years did to it:

• No ground conductor. There is no safe path for a fault, which is why modern appliances and surge-sensitive electronics should not run on these circuits.
• Buried insulation. The system was designed to shed heat into open air. Blown-in or batt insulation packed over it traps that heat and accelerates breakdown of the rubber jacket.
• Amateur splices. Decades of homeowner extensions tie modern cable into brittle century-old conductors, often outside a junction box.
• Overloaded circuits. These circuits were sized for a few light fixtures, not window units, space heaters, and a kitchen full of appliances.

What it does to your homeowners insurance

This is the part that surprises buyers. Underwriting, not the inspection, is usually what stalls the deal. Carriers generally take one of three positions: decline the property, bind coverage only after a licensed electrician certifies the circuits are intact and unmodified, or issue a policy with a surcharge and a deadline to rewire.

Call your insurance agent the same day the report lands and ask for a written position on the specific address. A verbal yes at quote time is not binding, and finding out at the closing table is the expensive version of this conversation.

What to do if this shows up in your report

1. 01Get a licensed electrician out for a scoped evaluation, not a phone estimate. You need to know how much of the original wiring is still energized.
2. 02Get the insurance position in writing before your due diligence period ends.
3. 03Price both options: a partial rewire of the active knob and tube circuits, and a whole home rewire. Insurers frequently want the second one.
4. 04Negotiate with the bid in hand. A credit at closing, a seller-completed rewire with a permit, or a price reduction are all normal outcomes.
5. 05If the seller does the work, require the permit and the final electrical inspection sign-off, then schedule a re-inspection.

Common questions