Knob and Tube Wiring Has No Ground, No Insulation Compatibility, and No Place in a Modern Home.

No — knob and tube wiring is not illegal, but it is prohibited in new construction and heavily restricted under current California and San Jose codes. Existing K&T is permitted to remain in place as long as it is not actively unsafe, modified, or covered by insulation without proper certification. However, the practical reality in 2026 is that it has become nearly impossible to insure a home with active K&T. K&T cannot be extended or added onto — any new circuit runs must use modern grounded wiring. It cannot be buried under insulation without a licensed electrician certifying it in writing to the local building department. And it cannot be used in any remodeled areas that require a permit.

Not freely — it requires a formal certification process and carries real risk. K&T wiring was designed to dissipate heat into open air. Covering it with insulation traps heat against the wire and can cause a fire. Under the California Electrical Code, insulation can only be installed over K&T if a licensed C-10 electrical contractor inspects the wiring and certifies in writing that it is in good condition with no deterioration or improper splices, that certification is filed with the local building department, and warning signs are posted at all access points. If the electrician finds any deterioration, insulation cannot be installed until repairs or rewiring are completed. Most insurance companies will not accept a certification as a substitute for full replacement.

Cali Rollin Electric pricing for knob and tube replacement in Santa Clara County: partial replacement covering the kitchen, bathrooms, and visible runs runs $8,000–$14,000. Whole-house K&T replacement runs $15,000–$25,000 or more depending on home size. Attic and crawl space K&T removal for non-active wiring runs $2,000–$5,000. Adding a panel upgrade at the same time adds $1,500–$3,000. Permits vary by city and typically add $500–$1,000. All pricing is provided in a written quote after a full circuit assessment.

Yes — this is increasingly common across the Bay Area. New policy applications with active K&T are now denied by most major carriers including State Farm, Farmers, and Liberty Mutual. Existing policyholders are receiving non-renewal notices giving 30–90 days to rewire or lose coverage. ABC7 reported in March 2025 that Bay Area homeowners are being denied or canceled specifically for K&T — carriers are treating it as an unacceptable underwriting risk regardless of whether a fire has occurred. Real estate transactions are also collapsing when K&T is flagged in a home inspection, since lenders won't approve a mortgage without insurable coverage. The only solution carriers reliably accept is full rewiring.

Technically only active — meaning energized — K&T circuits must be addressed. Inactive, disconnected wiring that carries no current poses no fire risk and can legally remain in the walls. In practice, if your goal is insurance compliance, most insurers require a written certification from the electrician that no live K&T remains anywhere in the home. A partial rewire that leaves some active K&T in service will not satisfy most carriers. During the free estimate walkthrough, Cali Rollin Electric maps all active K&T circuits using a circuit tracer, identifies what is truly live versus already abandoned, and gives you a clear scope. Homeowners are often surprised to find that portions of their home were already rewired at some point — reducing total scope and cost significantly.

On-site electrical work takes 3–15 working days depending on home size and accessibility. The full project timeline from first call to final inspection runs 4–10 weeks for most San Jose single-family homes once permitting and inspections are factored in. Permit approval in San Jose takes 5–15 business days. Plaster walls in older homes require slower, more careful wire fishing. Two city inspections are required — a rough-in inspection before walls are closed and a final inspection after completion. Drywall patching and painting by a separate contractor follows electrical sign-off. You can live in the home during the rewire in most cases — Cali Rollin Electric works room by room to keep most of the house functional throughout the project.