Knob and Tube Wiring:
Should You Replace It?
Knob-and-tube wiring is part of many charming older Los Angeles homes. Its presence is not a reason to panic, but it is a reason to understand the system’s condition and limitations before remodeling, adding loads, or renewing insurance.
Published: September 2, 2026 · Updated: September 2, 2026
How Knob-and-Tube Wiring Works
Knob-and-tube systems were installed in many homes built before modern cable became standard. Hot and neutral conductors run separately through walls and ceilings, supported by ceramic knobs and protected where they pass through framing by ceramic tubes. The air space around the conductors helped dissipate heat, and early installations generally did not include an equipment grounding conductor.
A home can have a mixture of original knob-and-tube, later cable, and undocumented alterations. You may see porcelain knobs in an attic, but only a careful inspection can determine whether the wiring is still energized, whether insulation is intact, and whether later work was connected correctly. Do not pull insulation aside or disturb conductors yourself.
Why Condition Matters More Than Age Alone
Insulation and heat
Rubber or cloth insulation can become brittle, cracked, or missing after decades of heat and movement. Modern blown-in or batt insulation may surround wiring that was designed to dissipate heat in open air. A professional can identify unsafe contact and recommend a remedy.
Ungrounded circuits
Many knob-and-tube circuits lack a grounding conductor. That does not mean every receptacle is immediately dangerous, but it can limit modern three-prong equipment, surge protection, and certain protective devices. Never use an adapter to defeat grounding.
Alterations and overloads
Previous owners may have spliced, extended, or overloaded old circuits. Loose connections and improvised junctions are often more concerning than the original ceramic supports. Adding large modern loads such as HVAC, induction cooking, EV charging, or workshop equipment needs a new load review.
Moisture and physical damage
Roof leaks, pests, remodeling nails, and attic traffic can damage insulation or supports. Any burning odor, buzzing, warm outlet, flickering, or repeated trip warrants prompt electrical repair rather than cosmetic work.
Do not make a decision solely from a home-inspection checkbox or a contractor’s sales pitch. Use the inspection to understand the condition, then choose work that fits safety, code, insurance, budget, and the way your household actually uses the home.
What a Knob-and-Tube Evaluation Includes
- History and goals. Tell the electrician about remodeling plans, insurance questions, nuisance trips, and appliances you want to add.
- Panel and service review. The inspector checks panel condition, labeling, grounding and bonding, overcurrent protection, service capacity, and evidence of unsafe modifications.
- Representative-access inspection. Attic, crawl-space, basement, garage, and accessible receptacles reveal conductor routing and insulation condition. Walls do not need to be opened everywhere to begin.
- Testing. Voltage, polarity, grounding, GFCI/AFCI operation, and selected circuit continuity can expose problems that are invisible from the room.
- Written options. You should receive clear distinctions between monitor-and-maintain, targeted correction, circuit replacement, and a complete rewire, with permit and finish implications explained.
An inspection is not a guarantee that hidden wiring is perfect. It is a disciplined way to find accessible hazards and make a proportionate plan.
Repair, Partial Replacement, or Whole-Home Rewire?
Targeted correction can make sense when a limited section has damaged insulation, an unsafe splice, or an improperly added outlet. The electrician may install a new grounded circuit for a specific room while leaving sound legacy wiring undisturbed.
Partial replacement is common during a kitchen, bathroom, service, or addition project. New circuits can be brought to current standards while an evaluation identifies old circuits that should not be extended.
Whole-home rewiring becomes more compelling when original wiring is widespread, insulation is deteriorated, circuits lack grounding, previous alterations are undocumented, or the home needs substantially more capacity. Our whole-home rewiring service explains the planning conversation.
A rewire is a coordinated construction project. Expect circuit mapping, permits, access through attic or crawl spaces, careful removal or abandonment of old conductors, new cable and boxes, grounding and bonding, device installation, inspection, and possible drywall or plaster repair. Ask who handles each finish item and how rooms will be kept safe during the work.
Which LA Neighborhoods Still Have Knob-and-Tube?
Knob-and-tube wiring is common in pre-1960s homes across Los Angeles. The neighborhoods most affected include:
Hollywood & East Hollywood
Many homes built 1920s–1940s still have original wiring. Dense construction and aging insulation increase risk.
Highland Park & Eagle Rock
Craftsman and Spanish-style homes from the 1920s–1940s commonly have knob-and-tube. Insurance companies flag these neighborhoods.
Boyle Heights & East LA
Older housing stock with frequent insurance issues. Many homeowners discover knob-and-tube during purchase inspections.
Los Feliz & Atwater Village
Historic homes with mixed wiring — original knob-and-tube plus undocumented alterations from previous owners.
Silver Lake & Echo Park
Renovated homes may still have hidden knob-and-tube in attics and crawl spaces behind new drywall.
West Adams & Harvard Heights
Large historic homes with extensive original wiring. Whole-home rewiring is common here.
Insurance Problems Caused by Old Wiring
Coverage denial risk
Some insurers will not renew policies for homes with active knob-and-tube wiring. Others require an inspection report or electrician's letter confirming the system is safe.
What insurers typically ask for
- Written inspection report from a licensed electrician
- Evidence that no insulation contacts the wiring
- Confirmation that circuits are not overloaded
- Documentation of any modifications or repairs
- A commitment to replace the wiring within a specified timeframe
Get it in writing
Do not rely on verbal assurances from your insurer. Ask for the specific requirement in writing — some carriers require replacement, others accept inspection and monitoring. AMY Electric provides inspection reports and electrician letters that satisfy most LA-area carriers.
Knob-and-Tube Replacement Cost Guide
| Scope | Typical Cost |
|---|---|
| Targeted correction (1–2 circuits) | $1,500 – $3,000 |
| Partial replacement (kitchen/bath) | $3,000 – $6,000 |
| Whole-home rewire | $8,000 – $20,000 |
| LADBS permit (residential) | $150 – $400 |
| LADBS inspection | $100 – $250 |
Costs depend on home size, access, and finish repair needs. AMY Electric provides fixed-price estimates before work begins.
Ask your insurer
Requirements differ by carrier and policy. Ask whether an inspection, electrician letter, replacement deadline, or documentation is needed. Get the answer in writing; do not rely on a general internet rule.
Check your jurisdiction
Los Angeles-area cities can apply different permit and inspection procedures. Confirm current requirements with LADBS or your local building department before work begins.
Plan modern loads
Discuss panel capacity for heat pumps, solar, induction ranges, and EV charging. See EV charger installation and panel upgrade guidance.
Older housing stock appears across neighborhoods such as Los Angeles, Pasadena, Burbank, Glendale, and Hollywood. Use our service areas page to find the communities we serve.
How to Plan a Rewire in an Older Home
Start with a room-by-room inventory. Note outlets, lighting, smoke alarms, fixed appliances, attic and crawl-space access, and any areas that cannot be opened easily. Decide whether the home will be occupied. A phased plan may reduce disruption, but it can also extend the project and leave some legacy circuits in service temporarily. Your electrician should explain the tradeoff.
New wiring is typically routed through accessible attics, crawl spaces, basements, closets, and carefully selected wall openings. Boxes must be secured, devices must be correctly rated, and circuits need clear labeling. Kitchens, bathrooms, garages, exterior areas, laundry rooms, and sleeping areas may require different protection. The exact requirements depend on the work and current adopted code; the authority having jurisdiction makes the final inspection determination.
Do not assume a rewire automatically includes plaster repair, painting, cabinetry removal, asbestos or lead testing, or correction of unrelated structural problems. Put those responsibilities in writing. Protect furnishings and keep temporary cords, open boxes, and construction debris away from children and pets. After inspection, retain circuit maps and photographs before walls are closed.
A thoughtful contractor will also discuss future flexibility: spare capacity, dedicated appliance circuits, surge protection, data pathways, EV charging, and solar readiness. These choices can reduce future wall opening, but they should be based on your actual plans rather than a sales checklist.
What a Good Recommendation Sounds Like
A useful recommendation explains the evidence, urgency, and alternatives. It should identify which circuits were observed, what was tested, whether insulation or grounding is deficient, and what could happen if the condition is left unchanged. It should also separate required corrections from improvements that are convenient during a remodel. Ask whether the proposal includes permits, inspection, temporary power, access openings, device upgrades, panel work, and finish restoration. Two contractors may recommend different scopes because they found different access conditions, so compare the written findings rather than only the total price. If an insurer requests documentation, provide the inspection report and ask what exact wording or work it requires. Taking time to understand the options is especially valuable in a historic or architecturally distinctive LA home, where preserving finishes and making safe, code-compliant improvements must be planned together.
Start With Facts, Not Fear
A careful inspection gives you a decision you can defend to your family, insurer, and future buyers. It also helps prioritize urgent corrections while avoiding unnecessary disruption. If the system is stable, you can plan improvements in stages; if a hazard is found, address it before cosmetic remodeling or adding major appliances. keep the report with your home records so future electricians do not have to repeat basic discovery today or tomorrow.
Knob-and-Tube Questions
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Concerned about old wiring?
AMY Electric provides careful inspections and C-10 electrical work in Greater Los Angeles.
☎ (818) 302-5614Amram is a California-licensed C-10 electrical contractor (License #981578) with 15+ years of hands-on experience and EVITP certification (#4051604) for EV charging infrastructure. He founded AMY Electric in 2012. Verify the license: CSLB license lookup.