If you own a historic home in Aiken, SC, there's a good chance you might have knob and tube wiring hidden behind your walls. While this electrical system was state-of-the-art when it was installed between the 1880s and 1940s, it poses serious safety risks today and can create significant obstacles when trying to insure your home. Understanding what knob and tube wiring is, why it's dangerous, and what you can do about it is essential for any Aiken homeowner living in an older property.
What Is Knob and Tube Wiring?
Knob and tube wiring was the standard method of electrical installation in homes built from the 1880s through the 1940s. The system gets its name from the ceramic knobs and tubes that were used to route electrical wiring through wall studs and floor joists.
The knobs were porcelain insulators nailed to wooden framing members to support the wires, while the tubes were ceramic cylinders that protected the wires where they passed through structural elements. The actual wiring consisted of two separate rubber-coated copper conductors—one hot wire and one neutral wire—that ran parallel to each other but were kept separated by air gaps.
This open-air design was actually quite clever for its time. The air space around the wires helped dissipate heat, which was important since the rubber insulation of that era wasn't as heat-resistant as modern materials. For several decades, knob and tube wiring performed reliably in countless American homes.
Why Knob and Tube Wiring Becomes Dangerous
While knob and tube wiring was safe when it was new and properly installed, several factors have made it a serious hazard in modern homes:
Deteriorated Insulation
The rubber insulation that covered knob and tube wiring was only designed to last about 25 years. After 80 to 140 years, this insulation has typically become brittle, cracked, or completely disintegrated. Exposed copper conductors create a serious shock and fire hazard, especially in areas where people might come into contact with them in attics or basements.
No Ground Wire
Knob and tube systems only have two wires: hot and neutral. They lack the ground wire that's standard in all modern electrical systems. The ground wire provides a safe path for electrical current to follow in case of a short circuit or fault, protecting you from electrocution. Without this safety feature, you're at much greater risk of electrical shock.
Contact with Insulation
The original knob and tube design relied on open air around the wires for heat dissipation. However, many Aiken homeowners have added blown-in insulation to their attics and walls over the years to improve energy efficiency. When modern insulation covers knob and tube wiring, it traps heat around the conductors, creating a fire hazard. The wiring can overheat and ignite surrounding materials.
Inadequate for Modern Electrical Loads
Homes from the early 20th century used far less electricity than we do today. They might have had a few lights, a radio, and maybe an electric iron. Today's homes run air conditioning systems, computers, large-screen televisions, kitchen appliances, and numerous other devices. Knob and tube wiring simply wasn't designed to handle these electrical loads safely.
Amateur Modifications
Over the decades, many knob and tube systems have been modified by unqualified individuals who didn't understand the system's limitations. We frequently find improper splices, connections to modern wiring that aren't up to code, and overloaded circuits. These amateur modifications compound the existing dangers.
How to Identify Knob and Tube Wiring in Your Aiken Home
If your home was built before 1950, there's a possibility it contains knob and tube wiring. Here's how to check:
Visual Inspection of Accessible Areas
Start by examining your unfinished basement or attic. Look for ceramic knobs about 1 inch in diameter nailed to the floor joists or rafters. The wiring will be cloth-covered or rubber-insulated, and you'll typically see two separate wires running parallel to each other rather than bundled together in a single cable.
Check your electrical panel as well. If you see old cloth-covered wires entering the panel or a fuse box instead of a modern breaker panel, this is a strong indicator of knob and tube wiring.
Two-Prong Outlets
While not definitive proof, two-prong outlets (without a ground hole) are common in homes with knob and tube wiring. However, be aware that some homeowners have replaced the visible outlets with modern three-prong versions without actually upgrading the wiring behind the walls.
Professional Inspection
The only way to know for certain whether you have knob and tube wiring—and how extensive it is—is to hire a licensed electrician to perform a thorough inspection. At Unity Power & Light, we can assess your entire electrical system, identify knob and tube wiring even in hidden locations, and provide you with a detailed report on your home's electrical safety.
Insurance Complications with Knob and Tube Wiring
One of the most significant problems Aiken homeowners face with knob and tube wiring isn't just the safety risk—it's the insurance challenge. Most insurance companies today either refuse to insure homes with active knob and tube wiring or charge substantially higher premiums.
Insurance companies have recognized that knob and tube wiring dramatically increases the risk of electrical fires. According to industry data, homes with knob and tube wiring are significantly more likely to experience electrical fires compared to homes with modern wiring systems.
If you're trying to buy a home in Aiken that has knob and tube wiring, you may find that your lender requires you to replace it before they'll approve your mortgage. Similarly, if you're selling a home with knob and tube wiring, you may need to replace it to close the sale, or you'll need to significantly reduce your asking price.
Some insurance companies will provide coverage if a licensed electrician certifies that the knob and tube wiring is in good condition, isn't overloaded, and doesn't have insulation in contact with the wires. However, this certification is becoming increasingly rare, as most electricians are reluctant to certify aging knob and tube systems given the inherent risks.
Replacement Options and Costs
If you discover knob and tube wiring in your Aiken home, you have several options:
Complete Replacement
The most comprehensive solution is a complete rewiring of your home with modern NM (non-metallic) cable, commonly known as Romex. This involves running new wiring throughout your home, installing a new electrical panel if needed, and bringing everything up to current National Electrical Code (NEC) standards.
For most Aiken homes, a complete knob and tube replacement ranges from $8,000 to $20,000, depending on the size of your home, accessibility of the wiring, and whether your walls are finished. While this represents a significant investment, it dramatically improves your home's safety, makes it insurable, and increases its resale value.
Partial Replacement
In some cases, you might be able to replace only the most critical circuits—such as those serving kitchens, bathrooms, and bedrooms—while leaving other portions of the knob and tube system in place temporarily. This approach costs less upfront but still leaves some risk in your home. It's typically only appropriate as an interim step toward full replacement.
Panel Upgrade
Many homes with knob and tube wiring also have outdated electrical panels with insufficient capacity for modern needs. If your home has a 60-amp or 100-amp service, you'll likely need to upgrade to a 200-amp panel when you replace your knob and tube wiring. This ensures your electrical system can handle today's electrical demands safely.
National Electrical Code Requirements
The National Electrical Code (NEC), which South Carolina has adopted, doesn't explicitly prohibit knob and tube wiring that's already installed. However, the code does establish strict requirements:
- Knob and tube wiring cannot be extended or modified—if you're doing electrical work in a home with this wiring, you must replace the affected circuits with modern wiring
- Knob and tube wiring cannot be in contact with insulation, building materials, or other heat sources
- The wiring must be maintained in good condition with intact insulation
- Circuits cannot be overloaded beyond their original design capacity
- Any modifications must be performed by a licensed electrician
As a practical matter, these requirements make it nearly impossible to keep knob and tube wiring in service while maintaining a safe, code-compliant home. Any time you want to add a circuit, upgrade an outlet, or make other electrical improvements, you'll be forced to replace at least part of the system.
Why Professional Replacement Is Essential
Replacing knob and tube wiring is not a DIY project. It requires extensive knowledge of electrical codes, proper installation techniques, and safety protocols. An improperly installed electrical system can be just as dangerous as the knob and tube wiring it replaces.
At Unity Power & Light, our licensed electricians have extensive experience replacing knob and tube wiring in Aiken's historic homes. We understand the unique challenges these projects present, from working around old construction methods to minimizing wall damage during installation. We'll also handle all necessary permits and inspections to ensure your new electrical system meets all local and national codes.
Moving Forward with Your Aiken Home
If you've discovered or suspect knob and tube wiring in your Aiken home, don't panic—but don't ignore it either. This is a serious safety issue that requires professional attention.
Start by having your electrical system professionally inspected. We'll provide you with a comprehensive assessment of your wiring, identify all areas where knob and tube wiring exists, and give you a detailed estimate for replacement. We can also provide documentation for your insurance company if needed.
While replacing knob and tube wiring represents a significant investment, it's one of the most important safety upgrades you can make to an older home. It protects your family from electrical fires and shock hazards, makes your home insurable, and gives you the electrical capacity you need for modern living.
Many Aiken homeowners are surprised to find that the rewiring process is less disruptive than they expected. Our electricians work efficiently to minimize wall damage, and we coordinate our work to fit your schedule. In many cases, you can remain in your home throughout the project.