Panels & wiring

Knob-and-tube wiring replacement

Knob-and-tube replacement removes early wiring (about 1880s to 1940s) that runs on ceramic knobs and tubes without a ground, and replaces it with modern grounded cable. It is commonly done before insulating, during renovations, or when an insurer requires it.

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An electrician running new wiring through open wall studs

About knob-and-tube wiring replacement

Knob-and-tube wiring was designed to release heat into open air. Over a century, its insulation becomes brittle, connections are often modified by later owners, and it has no ground conductor for modern three-prong outlets or GFCI-friendly appliances.

The biggest practical issue is insulation: blowing insulation into walls or attics around active knob-and-tube traps heat, so many insulation programs and contractors require it to be assessed or replaced first. Insurers also frequently ask about it.

Knob-and-Tube Wiring Replacement at a glance: Panels & wiring
Who does the work: An independent licensed electrician
Urgent calls: Usually scheduled
Typical first step: Trace active circuits

Signs you need this

Ceramic knobs and tubes visible in the attic or basement
Two-prong outlets throughout the house
An insulation contractor or energy program requiring an assessment
An insurer asking about wiring type
Fuses or a small service alongside old wiring

What the electrician does

1
Trace active circuits
The electrician identifies which knob-and-tube runs are still live and where they go.
2
Plan the routes
New cable routes are planned through attics, basements and walls to minimize openings.
3
Install new circuits
Grounded cable, boxes and devices are installed and the old wiring is disconnected.
4
Inspect and patch
Rough-in and final inspections are completed, and access holes are patched.

What affects the cost

Electricians set their own prices. These are the factors that move a quote up or down, so you can compare like for like.

How much knob-and-tube is still active
Plaster versus drywall walls
Attic and basement access
Number of floors
Panel upgrade at the same time
Wall patching and painting

What you can do safely, and when to stop

Safe to do

✓ Look in the attic or basement for ceramic knobs and photograph them

Stop and call

✕ Do not insulate over active knob-and-tube
✕ Do not splice new wire onto old

Knob-and-Tube Wiring Replacement FAQ

Is knob-and-tube wiring illegal?

Existing knob-and-tube is generally not illegal, but it cannot be extended, and many insurers and lenders treat it as a reason to replace.

Can knob-and-tube be insulated over?

It is not recommended, and many codes and insulation programs prohibit it, because the wiring relies on open air to cool.

How do I know if mine is still live?

An electrician can test it. Many homes have a mix of active and abandoned knob-and-tube.

How long does replacement take?

From a few days for a small home with good access to a few weeks for larger plaster-walled homes.

Do walls have to be opened?

Some small openings are usually needed, but most new cable is fished through walls from above and below.

Where electricians offer this

Local guides to knob-and-tube wiring replacement in cities where local housing makes it a common job:

Birmingham, AL Mobile, AL Montgomery, AL Little Rock, AR Fayetteville, AR Los Angeles, CA San Diego, CA Sacramento, CA Fresno, CA Long Beach, CA Oakland, CA Stockton, CA Pasadena, CA Denver, CO Fort Collins, CO Boulder, CO Hartford, CT New Haven, CT Waterbury, CT Stamford, CT Wilmington, DE Dover, DE Washington, DC Pensacola, FL Saint Petersburg, FL Gainesville, FL West Palm Beach, FL Atlanta, GA Augusta, GA Savannah, GA Marietta, GA Boise, ID Peoria, IL Rockford, IL Indianapolis, IN Fort Wayne, IN South Bend, IN Cedar Rapids, IA Wichita, KS Louisville, KY Lexington, KY New Orleans, LA Baton Rouge, LA Portland, ME Baltimore, MD Boston, MA Springfield, MA Worcester, MA Detroit, MI Grand Rapids, MI Lansing, MI Ann Arbor, MI Minneapolis, MN Saint Paul, MN Jackson, MS Hattiesburg, MS Kansas City, MO Saint Louis, MO Missoula, MT Omaha, NE Lincoln, NE Reno, NV Manchester, NH Nashua, NH Trenton, NJ Newark, NJ Jersey City, NJ Paterson, NJ New York, NY Albany, NY Syracuse, NY Rochester, NY Buffalo, NY Raleigh, NC Greensboro, NC Durham, NC Wilmington, NC Columbus, OH Cleveland, OH Cincinnati, OH Toledo, OH Akron, OH Oklahoma City, OK Tulsa, OK Portland, OR Salem, OR Eugene, OR Philadelphia, PA Pittsburgh, PA Allentown, PA Scranton, PA Providence, RI Warwick, RI Charleston, SC Columbia, SC Greenville, SC Knoxville, TN Chattanooga, TN Memphis, TN Fort Worth, TX Waco, TX Salt Lake City, UT Ogden, UT Richmond, VA Norfolk, VA Seattle, WA Spokane, WA Tacoma, WA Vancouver, WA Huntington, WV Milwaukee, WI Madison, WI Cheyenne, WY

By state:

Available through our network in 48 states and DC. Metro guides:

Birmingham, AL Mobile, AL Montgomery, AL Huntsville, AL Phoenix, AZ Tucson, AZ Mesa, AZ Little Rock, AR Fayetteville, AR Los Angeles, CA San Diego, CA Sacramento, CA San Francisco, CA San Jose, CA Fresno, CA Riverside, CA Bakersfield, CA Long Beach, CA Oakland, CA Stockton, CA Anaheim, CA Modesto, CA Pasadena, CA Santa Rosa, CA Denver, CO Colorado Springs, CO Aurora, CO Fort Collins, CO Pueblo, CO Boulder, CO Hartford, CT New Haven, CT Bridgeport, CT Waterbury, CT Stamford, CT Wilmington, DE Dover, DE Washington, DC Miami, FL Tampa, FL Orlando, FL Jacksonville, FL Pensacola, FL Fort Lauderdale, FL Saint Petersburg, FL Kissimmee, FL Lakeland, FL Gainesville, FL Tallahassee, FL West Palm Beach, FL Fort Myers, FL Sarasota, FL Daytona Beach, FL Bradenton, FL Fort Pierce, FL Naples, FL Atlanta, GA Augusta, GA Savannah, GA Athens, GA Marietta, GA Kahului, HI Boise, ID Nampa, ID Chicago, IL Peoria, IL Rockford, IL Indianapolis, IN Fort Wayne, IN South Bend, IN Des Moines, IA Davenport, IA Cedar Rapids, IA Wichita, KS Overland Park, KS Louisville, KY Lexington, KY New Orleans, LA Baton Rouge, LA Shreveport, LA Metairie, LA Portland, ME Baltimore, MD Silver Spring, MD Annapolis, MD Boston, MA Springfield, MA Worcester, MA Detroit, MI Grand Rapids, MI Saginaw, MI Lansing, MI Ann Arbor, MI Minneapolis, MN Saint Paul, MN Gulfport, MS Jackson, MS Hattiesburg, MS Kansas City, MO Saint Louis, MO Columbia, MO Missoula, MT Omaha, NE Lincoln, NE Las Vegas, NV Reno, NV Henderson, NV Manchester, NH Nashua, NH Trenton, NJ Newark, NJ Jersey City, NJ Paterson, NJ Albuquerque, NM New York, NY Albany, NY Syracuse, NY Rochester, NY Buffalo, NY Schenectady, NY Charlotte, NC Raleigh, NC Greensboro, NC Durham, NC Winston-Salem, NC Wilmington, NC Columbus, OH Cleveland, OH Cincinnati, OH Dayton, OH Toledo, OH Akron, OH Oklahoma City, OK Tulsa, OK Norman, OK Portland, OR Salem, OR Eugene, OR Beaverton, OR Philadelphia, PA Pittsburgh, PA Allentown, PA Scranton, PA Harrisburg, PA Lancaster, PA Reading, PA Wilkes Barre, PA Providence, RI Warwick, RI Charleston, SC Columbia, SC Greenville, SC Nashville, TN Knoxville, TN Chattanooga, TN Memphis, TN Murfreesboro, TN Houston, TX Dallas, TX San Antonio, TX Austin, TX Fort Worth, TX El Paso, TX Denton, TX Corpus Christi, TX Waco, TX Plano, TX Tyler, TX Salt Lake City, UT Ogden, UT Virginia Beach, VA Arlington, VA Richmond, VA Norfolk, VA Alexandria, VA Chesapeake, VA Newport News, VA Hampton, VA Seattle, WA Spokane, WA Tacoma, WA Vancouver, WA Olympia, WA Everett, WA Huntington, WV Charleston, WV Milwaukee, WI Madison, WI Cheyenne, WY Casper, WY All locations →

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