Older homes offer charm, character and solid workmanship. As with all
painted ladies, makeup and a pretty façade can often disguise hidden
flaws. One such problem that can be expensive to remedy is knob and tube
electrical wiring found in the majority of American homes built between
1890 and the late 1930s.
Except for new construction, knob and tube wiring is not illegal, but
it is problematic. Local building codes vary as to treatment of knob
and tube in existing structures. Most electricians agree that, by
itself, knob and tube wiring does not pose a serious safety threat. The
problem is that, over time, most homes constructed in the knob and tube
era have undergone major modifications and upgrades. The knob and tube
system that was perfectly suited to a 1925 bungalow with 60 amp service
may not be efficient, or safe, in a 21st century home with
modern appliances and gadgets. Knob and tube wiring may render that
perfect craftsman bungalow you have fallen in love with uninsurable.
Knob and tube wiring was a very efficient system in its day. Some
licensed electricians still regard it as superior to modern wiring. The system
consisted of two wires, insulated in rubber sheaths and running parallel
to each other along cellar beams or attic rafters. The wires were
encased in ceramic tubes through joists and looped around ceramic knobs
when running over the joists – hence the name, “knob and tube”. The
system was designed for the exposed wires to dissipate heat. Because of
the heat, wires touching materials such as insulation can create a fire
hazard. Age alone can lead to brittle wires and stretched out rubber
sheaths, which are potential problems in this ungrounded system.
Many surviving knob and tube systems are 100 years old. When the
system was put in place, electric power in a home was a new invention.
Even at the close of the knob and tube era, the only home appliances
powered by electricity were radios, toasters and irons. Compare that to
today’s typical home with multiple computers, televisions, clothes
dryers and charging stations.
Before considering the purchase of an older home, or any home for
that matter, hire an experienced home inspector to inspect the home and
all its systems. If the inspector fails to report the presence of knob
and tube wiring in a home where it still exists, he has not done his
job. If the inspection indicates the presence of knob and tube and you
still wish to proceed with the purchase, have at least one and
preferably two licensed electricians inspect the wiring for wear and
tear or modifications to the original system that could present a fire
hazard. At a minimum, the presence of knob and tube wiring in any
condition can be used to negotiate a reduced purchase price.
The National Fire Protection Association reports that in 2008,
approximately 24,000 electrical fires were reported in the U.S, with a
majority occurring in homes over forty years old. While the statistics
do not point directly to knob and tube wiring as a cause, there is
enough concern to make insurers skittish. Opinions vary greatly as to
the inherent dangers associated with knob and tube wiring; however, the
bottom line is that most insurers do not look upon it favorably. Many
will refuse to insure the home at all or offer inferior policies with
huge premiums and no replacement cost endorsement. In other words, you
will need to pay more for less coverage. You should always ask a licensed local contractor to check your electrical installation.
The cost of updating knob and tube wiring will vary according to the
size of the house and the extent of knob and tube that remains. It is a
messy, disruptive and labor-intensive job that should be performed by a
licensed contractor. Holes must be cut in the existing sheetrock or
plaster. The most cost efficient approach is to rewire in conjunction
with an overall renovation of the home.
In a buyer’s real estate market, the responsibility for addressing
knob and tube concerns rests squarely with the seller. Just a few years
ago, eager buyers were snatching up classic homes and the presence of
knob and tube wiring rarely factored into the selling price. Buyers
would either address the issue as part of an overall gutting and
modernization of the home or simply worry about it later. In today’s
sluggish market, that approach no longer works and the owner of a home
with knob and tube still in place should plan to attack the problem in
advance of selling the home, or be prepared to accept a major price