Knob and Tube Wiring Frequently Asked Questions

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We receive many questions from customers who are looking to replace their knob and tube wiring. We thought it would be helpful to have all the questions and answers in one place.  If there are any questions you would like addressed, not on this list, please let us know.

Q: I’m having my house insulated, do I need to remove my knob and tube wiring?

A: Any walls or ceilings that will be insulated must have active knob and tube wiring deactivated or removed.  The reason is, knob and tube wiring is designed to dissipate heat in open air. Once insulation is packed around it, it can no longer do this.

Q: I’m not having insulation installed, do I need to remove my active knob and tube wiring?

A: Some insurance companies will not insure homes that have active knob and tube wiring. Other than insurance and insulation, there is nothing forcing replacement.  Keep in mind however, knob and tube wiring is an ungrounded wiring style that is at this point, over 100 years old.

Q: Should I replace the BX wiring in my house while replacing the knob and tube?

A: BX wiring is the second generation of wiring used in homes.  It does not have the same insulation or insurance issues that knob and tube wiring does.  It is also quite old, being used from the early 1900’s up till the 1940’s.  In some homes it may be 100 years old at this point.  Lots of homes built between 1905 and 1932 have a combination of knob and tube and BX wiring.

Most customers who are replacing their knob and tube wiring for insulation will leave the BX wiring in place.  We often joke that we are saving some work for later; that we will be going back through all these homes again in 10 years to replace the BX wiring.

If your house has both, we are happy to give a separate estimate to replace the BX wiring so you can decide if it’s worth it.  It will certainly be cheaper to do it now, then years from now!

Q: What are the issues with knob and tube wiring?

A: It lacks a ground with is needed for personal safety. 

It cannot have insulation around it as previously mentioned.

Three prong outlets cannot be installed on knob and tube wiring, unless a GFCI outlet is used.  Even with the GFCI, there is still no true ground present.

It has a cloth insulation which can break down and expose bare copper.  This is particularly an issue in lights where heat from light bulbs has baked the wiring for years.

Some insurance companies will not insure homes with it.

It’s old!! At the time or writing this (2021) it is likely 100 years old, or more. Expecting this wiring to last with the electricity demands of today is not realistic.

Want a more indepth information on issues with K&T? Be sure to check out the Kuhlman Electric YouTube Channel

Q: Will you gut my walls to replace the knob and tube wiring?

A: NO, walls will not need to be gutted.  If you are talking with an electrician that says your walls will need to be gutted, look elsewhere! 

Q: If you are not gutting the walls, how do you replace the knob and tube wiring?

A: Some small holes will need to be created to fish the new wiring around.  Electricians who are experienced doing this kind of work will only make the holes in necessary locations to minimize overall damage to the house.  Most holes are around 1” in size and we rough patch them.

A lot more information can be found here about holes needed and techniques used – Click Here

Q: Do you need to remove all the knob and tube wiring after rewiring is complete?

A: All visible knob and tube wiring will need to be removed in spaces like unfinished basements and attics.  Basically, anywhere the knob and tube wiring is visible it must be completely removed.  In walls and ceilings where the KT wire is concealed, it does not need to be removed, just deactivated. 

Q: Can I live in the house while the work is being done?

A: Yes absolutely.  I would say 95% of our customers are living in their home while we are doing the replacement. While working our electricians use plastic coverings and vacuums to mitigate all the dust created.

Q: Does my power need to be turned off during installation?

A: Only the knob and tube circuits we are working on for safety. The other non-knob and tube circuits, we do not work on will be left on with power.

Q: Do I need to add outlets around my house to bring it up to current code while having the knob and tube replaced?

A: No, you don’t.  At minimum it needs to be put back how it was.  For example, if the room with knob and tube wiring only has 1 outlet, but would require 4 by todays code, only 1 needs to be done as that puts it back how it was.  The only time this could change is if any room is gutted.  If the space is gutted it needs to be brought up to days code.

However, if you were ever going to add any outlets for convenience, doing it while the knob and tube wiring is replaced will be efficient (save money!).

Q: Should I consider other electrical work while having my knob and tube wiring replaced?

A: Yes, I would certainly consider it!  In most cases there will be a cost savings to have new electrical added while the knob and tube wiring is being replaced.  This is because we are already snaking new wire around your house, so it’s relatively easy to add new electrical.

Some things I would consider: Recess lights, hard wired smoke detectors, additional outlets, 200amp service upgrades.  The more we can install at once, the bigger overall savings.

Q: How much is my knob and tube wiring replacement going to cost?

A: Ah yes, the cost question! Customers will often ask us for a ballpark cost without any scope of work. It’s impossible to estimate these jobs with knowing where the knob and tube is.  Every house has a different amount of knob and tube wiring left at this point.  Some homes are still full of it, and some only have it in a few locations.  It varies widely and will depend on how much of the house was remodeled or altered.

We price these jobs per point. Meaning the more outlets, lights, switches the more cost.  Without knowing the number of points it’s not possible to estimate these jobs with any accuracy.

Our goal when estimating these jobs is to be as accurate as possible! Throwing out ballpark costs without any information is not our style.

Q: How long will my job take to be completed?

A: Just like the cost question it varies widely from job to job. The more knob and tube wiring that needs to be replaced the more time it will take.  On average we can replace 6-8 points (switches, lights, outlets, circuits) per day. 

Q: Will I get a letter/certification from your company stating the knob and tube wiring has been removed / replaced?

A: Yes! After every job is completed, we give our customers a certification letter stating the home no longer has active knob and tube wiring.

Looking for more information on knob and tube wiring?

We have some more information found here on our website- Click Here

If you are looking for even MORE, take a look at this E-Book (or print!) on Amazon, it covers everything related to knob and tube wiring replacement.  It’s the perfect guide for any homeowner hiring an electrician to do this work

Homeowners Guide to Knob and Tube Wiring Replacement

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Kuhlman, It's Electric

Electricians who specialize in working in homes just like yours

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