How to Safely Replace Old Knob and Tube Wiring in Your Historic Home

What is Knob and Tube Wiring?

Knob and tube wiring was an early standardized method of electrical wiring used in buildings in Canada and the United States from about 1880 to the 1930s.

It consists of single insulated copper conductors run within wall cavities, passing through joist and stud drill-holes via protective porcelain insulating tubes, and supported along their length on nailed-down porcelain knob insulators.

This old wiring system presents safety hazards due to improper grounding, overloading, and deterioration over time. Replacing knob and tube wiring involves carefully removing the old wiring and installing new electrical cables and devices according to modern safety standards.

Dangers of Knob and Tube Wiring

Knob and tube wiring presents several safety issues:

• No grounding - There is no ground wire, increasing risk of shocks and fire. Grounded circuits are now required by electrical code.

• Overloading - The wiring is not designed to handle the electric load of modern appliances and electronics. Overloaded wires can overheat, melt insulation, arc, and cause fires.

• Deterioration - Old, cracked wire insulation can expose bare conductors, allowing shorts, arcing and sparks. Nearby combustible materials could ignite.

• Unsafe splices - Haphazard DIY repairs over the years may create connections prone to overheating.

• Exposed wires - Insulation can break down and crumble over time, leaving bare wires accessible.

These factors make knob and tube wiring too unsafe to remain in service. Replacement is recommended.

Dangers of DIY Knob and Tube Wiring Replacement

While it's tempting tackle a knob and tube rewiring project yourself, there are risks:

• Shock hazard - Live wires in walls can injure or kill if mishandled.

• Fire hazard - Mistakes can lead to electrical fires.

• Insurance issues - Home insurance may not cover damages caused by improper work.

• Historic preservation violation - Local codes may require special upgrades to preserve heritage features.

• Code violations - Improper materials or installation may fail inspection.

• No certification - As a DIYer, you cannot certify the work as properly and safely completed.

Consider consulting an experienced, licensed electrician for this hazardous project.

Finding an Electrical Contractor Experienced with Historic Homes

Seeking a qualified electrician is key for knob and tube replacement in heritage buildings. Look for:

• Licensed & Insured - Verify they carry liability and worker's insurance.

• Experienced - Search for contractors familiar with old wiring methods and historic home electrical needs.

• Specialty Certifications - Additional credentials in historic restoration or as a master electrician indicate advanced expertise.

• Reviews - Check online reviews and contact previous historic home clients for feedback.

• Listed by Heritage Organizations - Local historical societies may provide referrals to trusted specialists.

• Familiar with Codes - They must know the electrical rules for upgrades in designated heritage structures.

Choosing the right pro ensures your electrics are modernized to current standards while safely retaining the historic charm of your vintage home.

Planning the Rewiring Project

A certified electrician will oversee the technical details, but initial planning should cover:

• Permits - Electrical permits from your city are required for rewiring projects.

• Inspection - The existing wiring must be inspected to plan the new system.

• Electrical Load Audit - Review the home's circuits and calculate total electric usage.

• New Wire Sizing - Larger wire gauges may be needed for circuits powering newer devices.

• GFCI & AFCI Circuits - Installations in kitchens, bathrooms and bedrooms require special breakers.

• Removing Old Wiring - Knob and tube wires must be entirely removed and replaced.

• Preserving Historic Features - Update electrical while keeping heritage moldings, walls and decor intact.

Thorough planning ensures your historic house electrical upgrade improves safety and provides ample power while maintaining the structure's period-appropriate historic ambience.

Costs of Replacing Knob and Tube Wiring

Rewiring a house is a major project, so understand the typical costs:

• Electrician Fees - Labor will likely cost $100 per hour or more. Expect 10-30+ hours for a full rewire.

• Materials - Wiring, breakers, receptacles and other parts can range from $1000-5000 depending on home size.

• Wall Repairs - Plaster/drywall repair where walls are opened for new wiring may add $1000 or more.

• Permit Fees - Count on $100-$500 for required municipal electrical permits.

• Total - A full knob and tube rewire often totals $5000 to $15,000+, varying by home details. Get multiple quotes.

While not cheap, replacement by a licensed electrician ensures your vintage house wiring is modernized to meet safety codes and power needs while preserving heritage character.

Phase the Project to Fit Your Budget

If costs are prohibitive, consider a phased approach:

• Priority Circuits First - Rewire the most critical and used branch circuits initially.

• DIY Wall Repairs - Save on costs by patching and painting openings yourself after.

• Room-by-Room - Spread costs over time by rewiring one room or area per year.

• Independent Circuits - Disconnect problematic downstairs circuits from safely updated upstairs feeds.

• Basic Functions First - Focus first on wiring lighting, kitchen, laundry, and bath areas.

• Future Planning - Install wiring conduits for unfinished sections like basement and attic for later.

Working with your electrician to phase the rewire over several years can make the project more affordable while addressing the most hazardous wiring first.

Maintaining Historical Integrity During Rewiring

Balancing modernization with heritage preservation requires care:

• Minimize Damage - Use narrower cut openings and fish wires through walls to limit repairs needed.

• Match Finishes - Patch walls expertly and match existing paint, wallpaper, or plasterwork.

• Conceal New Components - Install boxes and conduits in closets, basements and crawlspaces rather than decor areas.

• Consult Experts - Local historical society provides guidance on balancing upgrades with preservation.

• Review Plans - Have your heritage committee or landmark commission approve project scope and methods.

• Document before Alteration - Photo/video record historic elements before they are disturbed in the rewiring process.

• Repair rather than Replace - Patch existing decorative switch plates and light fixtures when possible instead of replacing.

With careful planning and execution, your home's original allure and vintage appeal can be retained while hidden wiring and safety systems are modernized.

Replacing outdated and dangerous knob and tube wiring requires significant effort and expense. But renovating the electrical system in your heritage home to make it safer while keeping its historic spirit intact is a worthwhile investment. With proper project planning and an experienced contractor, you can have the best of both worlds - updated safety and power along with preserved historic charm.