Knob and tube wiring was commonly installed in homes built before the 1950s. While it was suitable for the electrical needs at the time, this old wiring system is inefficient and potentially hazardous by today's standards. Rewiring a home with knob and tube wiring can be a major project, but it is worthwhile to bring the electrical system up to code and add safety and convenience. Here is an in-depth guide on how I rewired my own home to replace the obsolete knob and tube wiring.
Dangers of Knob and Tube Wiring
Knob and tube wiring consists of insulated wires run through open air, supported by ceramic knobs and tubes. It lacks grounding and sufficient wire gauge for higher electrical loads. There are several risks posed by this outdated wiring:
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Fire hazard - The wiring insulation breaks down over time, exposing live wires that can arc and spark. This can easily ignite nearby combustible materials. Fires in older homes are often traced back to faulty knob and tube wiring.
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Insufficient power - Knob and tube wiring is insufficient for running multiple high wattage appliances at once without overload. Lights may dim when larger appliances turn on.
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No grounding - Ungrounded wiring presents a shock hazard. Without a proper ground path, a short could electrify metal surfaces like appliance housings and plumbing fixtures.
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Difficult to repair - The wires are very brittle, buried in walls, and cannot handle splicing. Any issues require complete rewiring of the circuit.
I wanted to feel safe and have full modern electrical capacity in my 70 year old home. Replacing the obsolete knob and tube wiring with new grounded NM cable was essential.
Evaluating Your Electrical Needs
Before deciding on rewiring, consider the age of your home's electrical system and what additional capacity you need.
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Take inventory of your home's electrical appliances and compare their wattage versus your electrical service panel size. Check for overload indicators like dimming lights.
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Consult an electrician to evaluate wiring condition. They can identify brittle insulation, improper splices and other hazards.
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Consider any large additions, like heat pumps or EV chargers, you want supported. Knob and tube is not sufficient.
For a 1930s small 2 bedroom home like mine, rewiring made sense to support higher wattage modern appliances. I budgeted for 200 amp electrical service and grounded wiring throughout.
Hiring an Electrical Contractor
Electrical work carries risk of injury or fire if done incorrectly. I strongly recommend hiring a licensed electrician for any major rewiring project. Here are some tips for finding the right pro:
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Ask neighbors for referrals and look up reviews. A local contractor with satisfied customers is a good bet.
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Verify they have an active electrical license and insurance coverage. This protects you from liability.
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Get at least 3 quotes to compare costs. Get a detailed bid spelling out the scope of work.
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Choose a contractor who specializes in wiring old homes. They're familiar with unique issues.
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Agree on a payment schedule with fair progress payments, not all upfront.
I selected a well regarded local electrical company that informed me throughout the project. Their expertise was essential.
Rewiring Step-By-Step Process
With an electrician hired, we systematically rewired my home circuit by circuit:
1. Shut Off Power and Remove Old Wiring
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The electrician shut off power at the main panel and meter before starting.
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We accessed each knob and tube run via attic and basement access points.
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He carefully extracted the old wires from the knobs and structure without damage.
2. Route and Install New Wiring
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We drilled pathways between joists and studs for running new NM cables.
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I assisted with routing cable between access points and pulling wires through conduit.
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At endpoints, the electrician added junction boxes and connected fixtures.
3. Connect to New Electrical Panel
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Once rewired, we installed a new 200 amp main service panel and connected all new circuits.
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Each circuit had a safety ground plus dedicated neutral. Much safer!
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The final step was removing the old panel and meter then connecting the utility drop.
Over 6 weeks, the house was systematically rewired to modern electrical code. It went smoothly thanks to an experienced electrician.
Common Rewiring Challenges
Rewiring a house as old as mine always involves surprises and challenges. Here are some we encountered and how we solved them:
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Inaccessible wires - We used long drill bits and fishing tools to access buried wires when walls could not be opened.
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Asbestos insulation - Wiring wrapped in asbestos had to be carefully extracted and disposed of according to hazmat procedure.
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Repairing plaster walls - Holes for new junction boxes had to be carefully patched to match old plaster walls.
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No existing ground path - We drove a new ground stake near the house since old homes lack grounding rods.
Careful planning and an adaptable electrician allowed us to work around all issues. I assisted to keep labor costs down while ensuring quality.
Costs of Replacing Knob and Tube Wiring
Rewiring a whole house is a major investment that pays off in safety. Here are the typical costs:
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Electrician Labor - For a standard 2,000 sqft house expect 40-60 hours total around $5,000. More for larger/complex homes.
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Electrical Supplies - At least $1,000 for new wire, junction boxes, conduits, breakers.
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Wall Repair - Up to $2,000 to patch holes if walls opened.
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New Service Panel - A 200 amp panel often runs $800-$1,500 installed.
In total, a full rewire like mine costs $8,000 to $15,000 on average. Regional rates vary. Check with local electricians.
While not cheap, the peace of mind and full functionality is worthwhile. Shop around for competitive pricing from qualified electricians.
Is a Rewire Required by Code?
Many wonder if removing knob and tube wiring is strictly required. Here are the facts:
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There is no federal or national mandate to proactively replace it.
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However, many local jurisdictions prohibit homes with knob and tube from passing inspection or being sold.
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Insurance companies may refuse coverage if they know old wiring is present.
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If making any major electrical changes, a rewire is usually triggered as a condition.
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Safety risks mean knob and tube wiring is never advisable to keep long-term.
I recommend consulting your local building department for rewiring requirements in your area. Most agree it should be done but timelines vary.
Conclusion
While rewiring a house is a major undertaking, safety risks and limitations of knob and tube wiring make it an essential upgrade. By hiring a professional electrician and budgeting appropriately, you can completely replace obsolete wiring for a safer, more functional home electrical system. It provides great peace of mind eliminating the risks of old wiring. I am thrilled to finally have a modern, grounded electrical system after rewiring my house.