Upgrading Knob and Tube Wiring in Old Homes

What is Knob and Tube Wiring?

Knob and tube wiring was an early standardized method of electrical wiring used in buildings in the United States from about 1880 to the 1940s. It consisted of single insulated copper conductors run within wall cavities, passing through joist and stud drill-holes via protective porcelain insulating tubes, and supported on nailed-down porcelain knob insulators.

This old wiring system has some major drawbacks compared to modern electrical wiring:

• Fire hazard - The insulation on old wiring can become brittle and crack over time, exposing the conductors and increasing fire risk. Knob and tube lacks a ground wire which can prevent faults from safely tripping breakers.

• Insufficient for modern loads - Knob and tube was not designed to handle the amount of electricity used by modern lighting, appliances and devices. Circuits are often overloaded and prone to overheating.

• Inadequate safety features - No ground wire means no GFCI or AFCI protection. Breaker panels are often very old with no safe way to add capacity.

• Difficult to modify - The knobs, tubes and conductors are rigidly fastened in place making it very hard to access or reroute the wiring. Adding circuits or outlets is extremely labor intensive.

For these reasons, knob and tube wiring can be considered unsafe by modern standards. Home insurance companies may refuse to insure a home without inspecting and approving any existing knob and tube wiring.

Why Upgrade Knob and Tube Wiring?

There are several important reasons to consider upgrading from old knob and tube wiring:

• Safety - Modern wiring is designed with multiple safety features to prevent fires and shock hazards. Replacing knob and tube reduces fire risk and protects your family.

• Reliability - New wiring will provide steady, dependable power to all your lights and outlets without overheating or overloading.

• Expandability - Upgrading the wiring makes it easy to add more circuits, outlets and ground fault protection where needed.

• Insurability - Some insurance providers may require upgrading knob and tube wiring before issuing a policy. Fixing it can avoid coverage problems.

• Resale value - Houses with modern wiring and electrical panels are more attractive to buyers. The upgrade pays off when selling.

• Peace of mind - You'll have confidence knowing your home's electrical system is safe, sufficient and up-to-code.

Options for Upgrading

There are a few different approaches to consider when replacing old knob and tube wiring:

Complete Rewire

This option involves removing all the old wiring and starting fresh with entirely new wiring throughout the house.

Pros:

• The most thorough upgrade option
• Allows rerouting wires more conveniently
• Opportunity to add capacity and new circuits

Cons:

• Very labor intensive and invasive to home
• More expensive than other options

Pigtailing

This is a limited option where the existing wiring stays in place but new grounded wires are spliced onto it where outlets and fixtures are located.

Pros:

• Less destructive than full rewire
• Lower cost than rewire

Cons:

• Original wiring stays in place
• Doesn't resolve capacity issues

Hybrid Rewire

This approach leaves harmless sections of knob and tube in place but strategically rewires the most problematic portions.

Pros:

• Less invasive than full rewire
• Prioritizes the most important upgrades

Cons:

• Existing wiring still remains in parts of home
• Cost depends on how much is replaced

Electrical Permits

It's important to pull proper permits before replacing knob and tube wiring. The local building department will inspect the work to ensure it meets electrical code requirements. Failing to get a permit can risk:

• Invalidation of homeowners insurance
• Fines from city inspectors
• Force redoing unapproved work

Be sure to hire a licensed electrician willing to acquire the required permits and schedule inspections. This protects you from any penalties and ensures the new wiring passes inspection on the first try.

Cost Factors

Upgrading knob and tube wiring is a major project, so the costs involved need careful consideration. The most important factors determining cost include:

• Extent of replacement - Complete rewires cost more than targeted upgrades

• Home layout - Wiring access challenges in finished walls or tight spaces add expense

• Electrician hourly rate - Prices range from $40-$100 per hour based on location and experience

• Permit fees - Permit costs vary by municipality, expect $100-$200

• Panel upgrade - Upgrading the main panel for modern capacity adds roughly $1000-$3000

For a complete rewire of an average 1500-2500 square foot home, expect total costs in the range of $8000-$15,000. Get multiple quotes to find the best deal.

Is DIY an Option?

Upgrading knob and tube wiring is complex project best left to licensed electricians. But some key points to keep in mind on DIY:

• Meeting code is crucial for safety and insurance
• Extensive experience with household wiring required
• Work must pass tough electrical inspections
• State laws may prohibit homeowners doing electrical work
• Insurance unlikely to cover DIY electrical damage

Unless you're a very capable handyman with electrical experience, hire a pro for such an important job. Safety and compliance are top priorities.

In Summary

Replacing antiquated, hazardous knob and tube wiring brings your home electrical system up to modern safety standards. Prioritize upgrades based on budget and get professional help to avoid safety or compliance issues. The investment pays dividends in home value, insurance savings and peace of mind.