Knob and Tube Wiring in Older Pittsburgh Homes: What Homebuyers Need to Know

As a home inspector working throughout Pittsburgh, I often get called into charming older homes that have stood tall for a century or more. From the elegant Victorians in Highland Park to the classic Four Squares in Squirrel Hill, these homes are packed with character. But they can also come with a surprise or two behind the walls. One of the most common—and most misunderstood—finds? Knob and tube wiring.

What Is Knob and Tube Wiring?

Knob and tube wiring (often abbreviated as K&T) was the standard electrical system used in American homes from about the 1880s through the 1940s. It gets its name from the ceramic knobs that anchor the wires to framing members and the ceramic tubes that protect wires passing through joists. If your Pittsburgh home was built before 1950, there's a decent chance it might still have some of this wiring in place.

Is It Safe?

K&T wiring wasn’t inherently unsafe for its time. In fact, when it was first installed, it worked just fine for the relatively low electrical demands of early 20th-century homes. But here’s where things get tricky:

• Aging Components: The insulation on K&T wiring is often made of rubber or cloth, which can become brittle and break down over time, leading to exposed wires.

• Overloaded Circuits: Modern electrical loads (think hair dryers, microwaves, computers) far exceed what K&T was designed to handle.

• Improper Modifications: Over the years, homeowners or handymen may have added to or altered the system in ways that aren’t up to code.

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What Do Homebuyers Need to Know?

1. Insurance Hurdles: Some insurers won’t write a policy on a home with active knob and tube wiring, or they may charge a premium.

2. Cost of Replacement: Rewiring a home isn’t cheap. Depending on the size and layout of the house, it could run from $8,000 to $20,000 or more.

3. Inspection Clues: During a home inspection, I look for signs of active K&T, including old-style wiring in the attic or basement, ceramic knobs/tubes, or outdated fuse boxes.

   
   

Can You Keep It?

In some cases, K&T can be left in place if it’s still in good condition and not serving high-demand circuits. But generally speaking, I advise homebuyers to budget for its eventual removal and replacement.

Final Thoughts

Buying an older home in Pittsburgh is like buying a piece of the city's history. But make sure you're also buying a home that can safely handle your family's needs. If you're not sure whether a home has knob and tube wiring, a thorough inspection will give you the answers—and peace of mind.