Yes, many of Baltimore’s older rowhomes still contain knob-and-tube wiring, especially in neighborhoods full of homes built before 1950. Baltimore’s rich stock of historic brick rowhouses is part of the city’s character, but a good number of them were wired in an era with very different electrical standards, and some of that original wiring is still in place. Knowing whether your rowhome has it matters for safety and insurance.

Here is what to know about knob-and-tube wiring in Baltimore rowhomes.

What knob-and-tube wiring is

Knob-and-tube wiring was the standard method for homes built roughly from the 1880s through the 1940s. It uses ceramic knobs to support individual wires and ceramic tubes to protect them where they pass through framing. It worked for the light electrical demands of its time, when homes had little more than a few lights and outlets.

The defining feature, and the problem, is that knob-and-tube wiring has no ground conductor. It was never designed for the electrical loads or the safety expectations of modern homes.

Where it shows up in Baltimore

Given the age of much of Baltimore’s rowhome stock, knob-and-tube is not unusual in older neighborhoods, particularly homes built before 1950. Many of the city’s brick rowhouses date to the late 1800s and early 1900s, and where they have never been fully rewired, original knob-and-tube can still be present in walls, attics, and basements.

If your rowhome is from that era and has not had a documented electrical update, it is worth finding out what is behind the walls.

Why knob-and-tube is a concern

Several factors make knob-and-tube wiring a safety and practical issue today:

• No ground. Without a grounding conductor, it cannot safely support modern three-prong appliances and electronics.
• Aging insulation. The original rubber or cloth insulation becomes brittle and can crumble after many decades, exposing conductors.
• Insulation contact. Knob-and-tube was designed to dissipate heat in open air. When later insulation is added around it, as often happens, it can overheat, creating a fire risk.
• Unsafe modifications. Over the years, knob-and-tube is frequently spliced or altered by amateur work, which introduces additional hazards.
• Capacity. It simply was not built for the electrical demands of a modern household.

The insurance factor

One of the most practical concerns is insurance. Many insurers will not cover a home with active knob-and-tube wiring, or they charge higher premiums for it. For Baltimore rowhome owners and buyers, this can be a significant issue, since a home that is hard to insure can be hard to sell or finance. Identifying knob-and-tube before buying lets you plan for updates and avoid surprises.

What to do if your rowhome has it

If you discover knob-and-tube wiring:

• Have a licensed electrician evaluate it to determine whether it is still active and what condition it is in.
• Avoid disturbing it or adding insulation around it until it is assessed.
• Discuss options, which for active knob-and-tube usually means rewiring the affected areas with modern grounded wiring.
• When replacing the panel, note that old knob-and-tube typically should not be reconnected into a new panel.

Rewiring a historic rowhome is very doable, and a skilled electrician can update the wiring while respecting the home’s plaster walls and character.

Many older Baltimore rowhomes, especially those built before 1950 and never fully rewired, still have knob-and-tube wiring. Because it lacks a ground, has aging insulation, poses a fire risk when covered by insulation, and can complicate insurance, it is a concern worth addressing. If your rowhome may have knob-and-tube, a licensed electrician can evaluate it and recommend the right path, which for active wiring usually means rewiring the affected areas.

Stella Electric evaluates and replaces knob-and-tube wiring in rowhomes across Baltimore and throughout Maryland, with flat-rate pricing and no overtime charges. If you own or are buying an older rowhome, we can tell you what is behind the walls. Financing is available on qualifying projects.