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How Code Changes Affect Home Inspections

How Code Changes Affect Home Inspections


A home is a snapshot of construction techniques and code requirements in effect at the time the house was built. As materials and technology changes over time, these changes are reflected in the materials and building requirements incorporated in each individual home.

Home Inspectors approach houses as a system. The house system is designed to

1. shed water without allowing it to penetrate or re-enter the building envelope at any point.

2. withstand wind without losing or suffering damage to components such as roofing, siding or doors and windows, and

3. keep the conditioned air, meaning heated or cooled or filtered air, inside, and when it does inevitably escape allowing it to escape the house without taking too much heat or coolness with it and not deposit moisture where it will accumulate and damage the structure.

4. provide a safe, functional environment for living.

Let's look at how the house system has changed over the years and what the inspector will identify as a deficiency.

Electrical System

From the days when the light and heat in a home was provided by fire, meaning open flames on candles, fireplaces, and burning wood in iron stoves, to today's cold LED lighting, cold induction heating for cooking, and furnaces that do not have pilot lights and water heaters that do not have tanks, the electrical system has come a long way.

These changes are implemented on an unplanned, ad hoc basis, meaning in some cases electricity was added to an existing house as it became available and the home owner could afford it. In other cases a new home is constructed by an owner or builder who wants to attract first time buyers looking for a home that incorporates the most modern of conveniences.

The first form electrical systems in the house took was knob and tube, also called open wiring. Knob and tube is a single conductor, ungrounded system. The knobs support the wires, which are wrapped with a cloth/rubber insulation that breaks down over time, eventually dropping off the wire, leaving bare wire carrying electricity. The heat insulation capability of the insulation is minimal at best and requires air space around it to dissipate the heat. The tubes carry the wires through walls or floor joists, insulating the wire from the dry, flammable wood. These devices are made of a ceramic material that, in my experience is usually brittle as a dry bone and often broken.

knob and tube illustration

The problem is that an inspector will find the wiring is often hidden in the walls or under insulation in the ceiling. This is a very dangerous situation, because as mentioned, the wiring requires air space to dissipate heat and the crumbling insulation bares wires that only need contact with dry wood or shavings to start a fire.

For these reasons, knob and tube has been rmoved from the building code in North America for many years. Unfortunately, the best remedy for this circumstance is complete replacement of the knob and tube with new modern wiring. This may even be required by insurance As a shortcut, most likely at some time a previous owner has done some renovation and spliced new wire onto the old existing and then hidden it behind walls. There will usually be no documentation and with a house that is 60 to 100 years old, it could be a couple of owners back when the work was done and the current owner has no idea of the extent of the old wire and its attendant problems.

And of course none of the old wiring is up to code, which only references knob and tube as not recommended and should be replaced.

Next, what replaced knob and tube?

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Doug Bowman

Certified home inspector, condominium document analyst and Realtor. More than 10 years experience in general real estate.

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