That's right - every now and then I run into the old knob and tube wiring.
The key word in that sentence is OLD.
Generally speaking, this older wiring system was used residentially in the United States from the 1880s to the 1930s. I have found reports of it being used residential construction in some areas as late as 1950. But that would be more on the unusual side probably.
When inspecting this house built in 1870 I found it everywhere, and still active, from the cellar to the attic.
Probably when the house was built there was no indoor electricity.
So, technically speaking, the listing for this house could have truthfully said that the electrical system had been "upgraded."
I say that tongue in cheek because while it may have been an upgrade at some point, today it is considered clearly outside of modern electrical practices, very obsolete, and most insurance companies, if not all, consider it to be dangerous. Many will not cover it, or a house where it is found.
I have had clients who purchased a house built in 1995 call me because their insurance application asked if the house had knob and tube wiring! And they did not know.
The photo above shows that the knob and tube wiring in that house was still active and live. It is still used, as I said, from top to bottom.
One problem I find in every house where it exists is that it is often tapped into and used to wire up new things!
Here, for example, the doorbell transformer is connected to it.
One problem with knob and tube wiring is that there is no conductor for modern grounding.
You can clearly see here how the ground wire that comes with the newer doorbell transformer has nothing to connect to!
My recommendation: this is a clear example of why a home inspection should happen with every home. And especially older homes! Home inspectors have knowledge and tools to be able to show their clients the condition of the house being inspected, and what it contains. When an odd circumstance exists, the home inspector will point it out!
Jay Markanich Real Estate Inspections, LLC
Based in Bristow, serving all of Northern Virginia.
Office (703) 330-6388 Cell (703) 585-7560