Assessing Knob & Tube Wiring

When buying an old home that may still be energized by some (or all) knob and tube wiring, what do you need to know?  What should you do?

By now most home buyers know that insurance companies, as a rule, don’t like knob and tube wiring.  Most will want it removed.  Some will give you a window of time in which to remover.  Still others won’t even entertain the idea of issuing a policy at all.  A few select insurers will still provide coverage depending on specific conditions.

A very common question home buyers are asked by their perspective insurer is about the percentage of knob and tube still present in the house.  This question is a misnomer and not particularly helpful.  It’s also something that’s very difficult to assess.  An example I routinely use when asked this question is:

 If the panel has two knob and tube circuits out of a total of 20, does that mean 10 percent of the circuits are knob and tube?   Technically –yes; practically – rarely.  If those two circuits energize 70 percent of the house, does that mean 70 percent knob and tube?  Perhaps, but what if they’re only energizing general low use/draw branch circuits like lighting and bedroom plugs?

A much more realistic method of describing the amount of knob and tube remaining in a house is through words like “substantially energized” (much or most of the house) or “appears to be minor” (usually one or two general branch circuits).  For a substantially K&T energized house, there should also be an indicator of whether or not the heaviest load circuits, like kitchens and baths, appear to have been updated.

For those insurers that still provide coverage for homes with knob and tube, the issues that are the deciding factors include the size of service, breaker (vs. fuse) panels, and type of circuits energized by the K&T.  Essentially, the heaviest load circuits like the kitchens and baths mentioned above need to be updated/modern for coverage.  This is not to suggest right or wrong; it simply is how the insurers still providing coverage tend to look at it.  There companies will also want the home inspected by either a home inspector on an approved list (people they trust to provide accurate information) or a full electrical inspection by a licensed electrician.

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