Knob and tube electrical

[Brendan Chetuck]

Hi all,

Looking at a house in the Albany, New York area and had a question. Has anyone ever dealt with knob and tube electrical?

I know prices vary from region to region but I would like a rough estimate for how much it would take to replace knob and tube in a 2700 sq ft duplex but in 1914.

Also I was wondering if it is required to update it?

It’s a pretty nice house and a reasonable area, but depending on the knob and tube, it could be a game changer.

Thanks everyone!

[Stephen Gallagher]

Originally posted by @Brendan Chetuck:

Hi all,

Looking at a house in the Albany, New York area and had a question. Has anyone ever dealt with knob and tube electrical?

I know prices vary from region to region but I would like a rough estimate for how much it would take to replace knob and tube in a 2700 sq ft duplex but in 1914.

Also I was wondering if it is required to update it?

It’s a pretty nice house and a reasonable area, but depending on the knob and tube, it could be a game changer.

Thanks everyone!

Good Luck with your purchase.

Knob and Tube is very common and has its fair share of negative and positive comments.  This is a timely post as I am quoting a K&T upgrade on a house here in NH this week.  There is no cut and dry answer to this question.  The electrical needs to be considered a system.  The system should take into consideration the Service (From Utility to Panel), the Branch circuits (individual circuits running through the walls) and the utilization devices (switches, Receptacles, and other devices).  

The service may need to be upgraded.  Typically when K&T is on premise the panel usually is still screw in and buss fuses.  This will need to be upgraded as it is the foundation of your system.  Cost can vary for a panel upgrade and is dependent on the Electrical Code edition adopted in your jurisdiction.  in my area this upgrade can run from $2500 to $4500.

The branch circuits running through the walls can, maybe maybe not, be safe.  K&T undisturbed can present no problems and will last longer than I am alive.  The issue that arises with K&T is where the integrity of the wires are compromised.  This compromise can be from heat caused by over loading,  heat caused by Added insulation (blown in cellulose) and brittle conductor and sheathing from past work.

Utilization devices are a concern, most notably because K&T has no ground and either two prong devices are in place, or people have unsafely added three prong receptacles in their place.  Grounded receptacles are the safest and although one can replace non three prong receptacles with a Ground Fault Circuit Interrupter, this still provides no grounding conductor.  Dryers and Ranges also normally need to be upgraded when found in a home with Knob and Tube.

Cost wise will vary depending on requirements of the Authority Having Jurisdiction (AHJ).  Local Ordinance may require you to embark on a journey that may be way more than you want to undertake.  Smoke detectors, Upgrading service, complete rewire may be your only options.  When I estimate the rewire,  I always start with the Service, include Smokes and go into the entire job, knowing that the house will now be brought up to whatever the currently adopted code is.  In my case this will include things like Arc Fault Circuit Interrupter Protected circuits through out the house.  Updated range and dryer, Smoke/CO as required, Updating premise grounding, surge protection.  This can get costly quickly.

Any electrician quoting by Sq. Ft. will either be extremely high $15-$20 per sq. ft. or will not be in business for very long.

Just some rough numbers for your entertainment, again base on my jurisdiction of NH.

Service Upgrade $3-5K

Smoke/CO $1.5-2.5K

Dryer Upgrade $3-500

Range Upgrade $3-500

each bedroom $6-900

Kitchen $5-10K

Each Bathroom $700-$1500

Laundry $5-900

This does not include HVAC, Sump Pump, garage, basement, attic.

The last Victorian rewire I completed was a $28K endeavor and took 3 weeks to complete.  Owner refused to remove plaster and lathe.  entire job was holes, fishing wires.  Homeowner would have saved money gutting to studs.  The amount that was paid to the contractor to plug, patch, and finish was almost as much as if they had installed all new drywall.

When considering a K&T upgrade, you will have to bring the entire house up to code.  This will most likely require additional receptacles in each room, front and rear of home, basement and garage.  This will require lighting circuits and fixtures.  When the job requires fishing you can count on 3 to 4 times the normal cost.

Adding a receptacle with open studs can be tallied at $75 each, fishing that same receptacle could be estimated at $200.  So it is always better off, if you have to rewire, to gut to the studs.  You are going to pay labor somewhere, and sweat equity and general labor is cheaper than paying electrical fees.

You stated you have an electrician coming.  First ask to see their license, ask for an insurance binder and ask for some references of other K&T jobs they have done.  Not all electricians are capable and not all have experience.  Don't be afraid to ask question of their process, like how they fish their wires, how they cut into the know and tube, do they patch?

Feel free to PM me if you need any other help.

Stephen Gallagher

Master electrician Ma, Me, NH, VT.