Looking to change out that old wiring in your house? Does your house predate the 1950s? Wondering about the cost to change knob and tube wiring?
The cost to change knob and tube wiring is between $7000 and $14000 CAD. It depends on the extent of the knob and tube and how far you are willing to go with damage to the home.
Factors To Consider With The Cost To Change Knob And Tube Wiring
The largest factor that you should consider in the price of having your knob and tube wiring changed is how much damage are you will to have for ease of price. Older homes built in the 50s usually have old plaster walls which become brittle over time.
More on the cost to change knob and tube wiring here.
They are basically an electricians nightmare to work around. It very difficult to have no damage from a rewire. Especially with these type of old walls. Most knob and tube is fastened inside the wall with the porcelain insulator attached with a nail. When the knob and tube terminated to the plug or switch usually has an electrical box attached to it.
The plaster will break when you try to pull the old wiring out. A large majority of the cost plays into the amount of labor time spent trying to pull wiring and save the old walls.
A perfect condition for us would be no one living in the home at the time and free range to cut wholes which would need to be repaired after the fact. Most older homes have special features of design and architecture with cause yo to purchase it so tearing wall out may not be an option for you.
Will I Have Damage To My Home
The short answer yes, but there is more to it than that. An electrical company can usually rewire to first floor outlets from the basement and the upstairs lights and plugs from the attic.
The problem is in the first floor lights. Homes that are 2 story with a finished upstairs have not access between floors. In order to replace the wiring, small notches must be cut at the top of the light switch location. This is so we can fish the wire down to the switch from the light.
The top floor outlets can sometimes be an issue as well. A number of older homes have fire braces in the outside walls about half way down. This makes it difficult to run the wire down to the plug without cutting a hole in the wall.
Common Issues With Knob And Tube
Some common issues with this type of wiring are maintenance. It is incredible difficult for the handyman to even change a light fixture. You will find that most of the knob and tube wires for lights don’t even have an electrical box. This leaves you nothing to attach the new fixture bar to.
The outlet boxes for the wall plugs are extremely short, This will cause problems when you go to change a plug because the old one is worn. The boxes are also not large enough to except a gfci receptacle.
How To Tell If you Have Knob And Tube
It is very easy to tell if you have knob and tube wiring just look in the basement. You will see the old cloth wire running down or between the joists separated with porcelain insulators. The difference in voltage of 120 volt is between the two individual wires.
If you can’t identify you knob and tube in the basement then have a look in the attic. If you have an attic with old floor boards then you will see the same thing between the roof rafters.
Is Knob And Tube Wiring Still Safe to Use?
Surprisingly, knob and tube wiring is still safe to use providing it is not added too, changed or altered. With that being said electrical appliances and devices today will new more “juice” thank knob and tube can supply.
We often see an entire upstairs on one circuit which in today’s world just won’t cut it. If you plug in a window ac unit and a hair dryer expect a fuse to pop. Installing a larger fuse will just cause a fire. Just because a 30 amp fuse will fit where a 15 amp one was does not mean you get more power. You will for a short period until you smell smoke.
If we had to put a percentage on it, I would say 50 percent of all home owners do this. The wire is only rated for 15 amps of current to pass through. If you install a larger fuse you are letting more amperage be drawn from the circuit and more than the wire itself can handle. This causes heat which then cause a fire.
Can I Add Wiring To Knob And Tube
You can not add any additional wiring to knob and tube. It is grandfathered into the code as is for now. However you can do repairs to old broken wires. You can also install an electrical box to install a new light fixture.
In fact in some cases we have found the know and tube to be in excellent condition and if we strip back the wires it’s like new. When we run into a situation where the knob and tube must remain then we often protect the circuit with a 15 amp gfci. We can also install a small sub panel and use a gfci breaker for that purpose only.
Most power utilities or inspection authorities do no except you to tear your home apart if you are just doing what we call a service upgrade.
Can I Replace The Knob And Tub Wiring Myself ?
No you can not, at least not to have any reputable electrician put their name on it and have their license on the line. This also comes with a number of liability issues for you and the electrician so just don’t do it.
If you are looking to save money on removing the knob and tube I wouldn’t. It can be abandoned inside the wall as per code as long as it is cut off on both ends and clearly marked “not in use”. If you are looking to save money on the wiring job then approach the electrician and ask if they would might you helping pulling new wires with their strict present guidance to cut back on the labor. It doesn’t hurt to ask.
More on what we recommend for replacement devices here.