KNOB AND TUBE WIRING REPLACEMET RESOURCES

OVERVIEW

This platform was created to help homeowners clearly understand the risks, costs, timeline, permitting requirements, and step-by-step process involved in replacing knob-and-tube wiring. We bring together practical guidance from real projects, licensed professionals, and local code experience so you can make informed decisions, avoid surprises, and plan upgrades with confidence. 

HISTORY

Knob-and-tube wiring was an early electrical system widely used in homes built from the late 1800s through the 1940s.

At the time, it was considered safe and effective, using ceramic knobs and tubes to keep wires separated and air-cooled. While many systems are still in place today, they were never designed for modern electrical demands, insulation contact, or today’s safety standards. 

More here on wiki.

TODAY'S STANDARDS IN 2026

Today’s electrical standards and building codes no longer view knob-and-tube wiring as a safe or code-compliant system for modern homes. Modern wiring methods are required to provide grounding, proper insulation, correct splices in junction boxes, and circuit protection that knob-and-tube systems lack, and these features are mandated by the current National Electrical Code (NEC) adopted locally in San Francisco. Homes with active knob-and-tube wiring may still legally exist, but they often fail inspections during renovations or real estate transactions, trigger insurance coverage challenges or denials, and cannot safely support today’s electrical loads without a full upgrade. In San Francisco, electrical permits and inspections are generally required for any replacement or alteration of existing wiring to ensure the work meets modern code, and upgrades usually include grounding and updated circuit protection that the old system does not provide.

INSURANCE

As mentioned on the home page, most carriers will have a problem with knob and tube, but provide cure priod to fix the knob and tube, which typically takes less than 30 days. Talk to your real estate agent about insurance options and hire local experienced contractor to get it done fast and per code. 

PARTIAL VS. FULL KNOB AND TUBE WIRING

Some homes might have partial rewiring done, such as the kichen or bathroom, when recently remodeled. However, this only helps partially, as the contractor has to rewire the remaining areas and cut walls along the path leading to the main panel for the new wiring. 

In some cases, the previous contractor might have simply connected new outlets to the old knob and tube, not uncommon. Thus, its important to verify with your contractor what's behind the new outlets and how much rewiring was actually done.