December 23, 2025

Why Knob and Tube Wiring Is Dangerous & Knowing When It’s Time to Upgrade

Many older homes in Colorado—especially those built before the 1950s—still contain original knob and tube wiring. While this electrical method was considered advanced at the time, it’s no longer suited for modern households or today’s electrical demands. If you live in a historic or older home, you may be asking: What is knob and tube wiring? Is knob and tube wiring safe? Why is knob and tube wiring dangerous?

Understanding the risks can help protect your home and your family. Here’s everything homeowners need to know about knob and tube wiring and how to recognize when it’s time for an upgrade.

What Is Knob and Tube Wiring?

Knob and tube wiring (often called K&T wiring) was the original method of electrical installation used in homes from the 1880s to the late 1940s. The name comes from the ceramic knobs and tubes that supported cloth-covered wires running along walls, ceilings, and joists.

Key characteristics include:

• Porcelain knobs that anchor and guide wires
• Hollow tubes that protect wires as they pass through wood framing
• Cloth or rubber insulation instead of today’s plastic coating
• No ground wires, meaning no extra protection against electrical faults

At the time, K&T wiring worked well for homes that only needed enough electricity for lights and a few small appliances. But today’s appliances, electronics, and HVAC systems draw far more power than this system was ever designed to handle.

Is Knob and Tube Wiring Safe?

The short answer is no—knob and tube wiring is not considered safe by modern electrical standards. While some of these systems may still function, the materials are well beyond their intended lifespan. Most K&T systems are now 70–100+ years old, making them vulnerable to dangerous electrical failures.

Additionally, many insurance companies refuse coverage or charge higher premiums for homes with K&T wiring due to its high fire risk. Some lenders will not approve mortgages for homes with active knob and tube wiring unless it is replaced.

Why Is Knob and Tube Wiring Dangerous?

Although knob and tube wiring may still carry electricity, it poses several major hazards that make it unsafe for modern use.

1. Worn or Brittle Insulation

The original cloth or rubber insulation deteriorates over time. Once insulation becomes brittle or falls off, wires can spark, arc, or overheat—leading to electrical fires.

2. No Grounding for Safety

Modern wiring includes a ground wire that redirects excess electricity during a fault. Knob and tube systems lack grounding, leaving your home vulnerable to fires, shocks, or damaged appliances.

3. Not Designed for Today’s Electrical Loads

Older homes had minimal electrical needs. Today’s households rely on heavy-duty appliances, smart home devices, computers, charging stations, and HVAC equipment. Overloading an outdated system dramatically increases the risk of overheating.

4. Hidden or Unpermitted Modifications

It’s common to find that homeowners or past electricians “patched” or spliced modern wiring into old K&T systems over the years. This mixing of old and new wiring can be extremely dangerous and often violates electrical codes.

5. Damage From Rodents or Moisture

Basements, attics, and crawlspaces where K&T wiring is installed often attract rodents. These pests chew through insulation, leaving exposed wires. Moisture can also damage insulation and the ceramic components.

6. Unsafe Insulation Practices

Knob and tube wiring must be surrounded by open air so it can dissipate heat. However, many attics with K&T wiring have been filled with insulation, trapping heat and creating a serious fire hazard.

For these reasons, electricians across the country strongly recommend replacing knob and tube wiring in any home still using it.

How to Tell If Your Home Has Knob and Tube Wiring

If your home was built before 1950, there’s a good chance it once had K&T wiring. To determine if any remains in use, look for:

• Wires stretched through ceramic knobs mounted on the framing
• Tubes protecting wires running through joists
• Two-prong (ungrounded) outlets
• Flickering lights or buzzing switches
• Warm or sparking outlets
• Frequently blown fuses or tripped breakers

Because much of a home’s electrical system is hidden behind walls, only a licensed electrician can confirm whether K&T wiring is active, partially replaced, or safely disconnected.

When It’s Time to Replace Knob and Tube Wiring

Even if your current knob and tube wiring appears to work, it’s still wise to request an electrical upgrade—especially if you notice any of the following:

• You’re installing large appliances like a new AC system
• You’re remodeling a kitchen or bathroom
• You need additional outlets or circuits

• Lights flicker when appliances turn on
• Your breaker panel trips frequently
• You smell burning or detect warm outlets
• Your insurance company requires replacement

Most homeowners choose to replace K&T wiring during renovations or when updating their electrical panels. Upgrading to modern wiring not only improves safety—it increases your home’s value, reduces insurance costs, and supports today’s electrical needs.

Why Upgrading Knob and Tube Wiring Is Worth It

Replacing knob and tube wiring offers several long-term benefits:

• Improved home safety and reduced fire risk
• Ability to handle modern electrical loads
• Compatibility with grounded outlets and surge protection
• Better energy efficiency
• Higher home resale value
• Lower insurance premiums

Most importantly, upgrading ensures that your home’s electrical system is reliable and compliant with modern electrical codes.

Protect Your Home—Schedule an Electrical Inspection Today

If you’re concerned about old wiring or wondering whether your home contains knob and tube, Applewood Plumbing Heating & Electric is here to help. Our licensed, background-checked electricians provide thorough inspections, honest recommendations, and safe, professional rewiring services.

We’re available 6 AM to 10 PM with NO overtime charges, and every job is backed by our industry-leading guarantee.

Call Applewood today at (720) 780-9143 to schedule your electrical inspection or wiring upgrade.