Knob and Tube

Check out our Knob and Tube Guide on Amazon!

A Homeowner’s Guide to Knob and Tube Wiring Replacement
Author: Jesse Kuhlman, Owner Kuhlman Electrical Services

Now available for digital download. This e-book is especially made for those who want to upgrade the old electrical wiring system of their home or want to know more about knob and tube wiring replacement.


Click here to buy on

Knob and Tube Wiring Team

KES specializes in knob and tube wire mapping and remediation. As experts in this field, our team brings the experience you need when it comes to replacing knob and tube. The team has the advantage of knowing the tricks and methods to replace your knob and tube wiring with the least damage to your plastered walls. We handle wiring replacement jobs year-round. Depending on the job, replacement time can take a few days while others take four to five weeks.

Disadvantages of Knob and Tube Wiring

Insulation companies cannot insulate your home with knob and tube wiring. The wiring is run between joists with air space to dissipate heat. When insulation, whether it’s blown in or standard pink insulation is surrounding the old wiring, it can overheat and potentially cause a fire hazard. The insulation company will require an electrician to inspect all wiring to confirm that there is no concealed knob and tube. If knob and tube wiring is found; it must be rewired to the standard set forth in the 2014 NEC (National Electrical Code).

Knob and tube wiring was never meant to last 100+ years. Homeowners sometimes take out the proper 15 amp or 20 amp fuse and install a 30 amp fuse because they do not have enough power. Yes, this will prevent your fuse from blowing but it creates a fire hazard. The knob and tube wiring that is now overfused was not meant to carry such a high current and the wire insulation can begin to break down.

Squirrels, mice and other critters seem to love the insulation on this knob and tube wiring style. These pests can can leave bare copper wire exposed.

A knob and tube wiring system does not incorporate a ground. The ground wire on any circuit is the most important wire, as it is there for safety. Also, some electronic equipment requires a ground to operate correctly.

Switched neutrals. Electricians in the early 1900’s would switch the neutral feeding a ceiling light instead of the hot wire (today’s standard). Switching the neutral, would turn off the light, but live voltage potential would still be present at the fixture. Making a dangerous situation for a homeowner that is trying to change the light fixture.

Insulation becomes very brittle and breaks down when heated too much. Older light fixtures had no insulation in them to prevent overheating. These older light fixtures were usually not marked with a maximum wattage for light bulbs. Homeowners could be installing 100 watt bulbs in fixtures that were never meant to have such a high wattage bulb, the wiring above the ceiling fixture could break down, and sometimes the insulation would disintegrate.

Some insurance companies are not insuring homes with existing knob and tube wiring.

Do I Have Knob and Tube Wiring?

A few things to look for:

  • Old porcelain knobs and joist sleeves in an unfinished attic or basement.
  • Outlets throughout your home that have old two prong outlets in the baseboard.
  • Using a 3 prong tester or voltage meter to test all  outlets around the house. If an “open ground” is found (meaning there is no ground), there is a good chance that wiring is tapped into the older wiring.

The Majority of Homes Have Knob and Tube Wiring in the Same Locations

Homes that still have active knob and tube wiring seem to follow a similar format.

  • Front porch light and switch
  • Front Entry light and switch
  • Dining room light and switch
  • Any three-way switches going up / down stairways and corresponding lights tied into these switches.
  • Additional 1st-floor wiring – Typically the older outlets still mounted in the baseboard. If the cellar is unfinished, getting to the outlets on the 1st  floor is quite simple, so these floors are typically already rewired.
  • 2nd floor wiring – Any older outlets in the baseboards, and sometimes lights and switches on this floor if there is a finished 3rd floor
  • The 2nd floor (if there is a finished 3rd floor) is the hardest floor to rewire, as we have no unfinished space above or below
  • If there is a finished 3rd floor, that is original to the house, this space often has some degree of knob and tube wiring left

Careful Rewiring Techniques:

In order to rewire holes in the walls and ceilings must be made to route new wiring around the house. Our electricians pride themselves in planning ahead and making the fewest holes possible. Each of our electricians is highly skilled at fishing wire in the most proficient manner and work as neatly and cleanly as possible. After the wires are fished, our team ensures all holes are patched.


Tarps and plastic will be used to cover your floors and furniture. Furniture will also be moved if necessary. The rewiring process is a very dusty job and our electricians pride themselves on leaving an area as clean as possible.

While replacing knob and tube wiring, our team is conscience of leaving needed lights and outlets active and have specific methods to make the jobs run as smoothly as possible while trying not interfere with the homeowners daily activities.

Fact: 90% of our customers live in their home during the knob and tube replacement.

How Much Will it Cost to Replace Knob and Tube Wiring?

Home owners with knob and tube wiring are offered two options for replacement cost:

Completely free in-home estimate. The KES team will come to your home and identify the active knob and tube wiring. These circuits at the panel will be shut off.  A walk through the home will be done to identify all the lights and outlets that are no longer active. An estimate will be created off the findings, with an easy to understand “adjustments” section of the estimate.

Meaning – If there is any modern wiring, originally thought to be knob and tube wiring listed in the estimate, a credit will be due.  Any additional knob and tube wiring found that is not listed on the estimate will be considered an extra cost.

Transparent Knob and Tube Replacement Estimate:

A “cost per point” method of estimating is used to estimate jobs. A point is a switch, outlet, light, circuit from the panel, etc. There is no hourly charge for knob and tube wiring replacement jobs.

Let’s say the cost per point is $200.00 each, if you decide to add two outlets in a bedroom, the homeowner will know exactly what the additional outlets will cost.

The cost per point for homes can vary based on the type of home. Some homes are much easier to fish new wiring while others are quite difficult and more time consuming.

Knob and Tube Mapping Service:

The team will come to your home at an hourly rate, map and color code all the wiring throughout the home that is easy to understand. The estimate will be based on the map, which is the owners to keep. If hired, we will credit the amount paid for the mapping service.

There is no variation in cost using the mapping method once the knob and tube wiring replacement has started. This method is for the owner who prefers to know the cost. Most replacement jobs take two electricians  and about 2-5 hours to map properly.

Fact: 80% of our customers elect the free in-home estimate