Common Structural Terms

In this section of the course, let's learn about some common terms or phrases that are used in the construction and building industry, particularly related to a residential building. Understanding construction terminology and knowing the purposes of building components and framing members (for example, studs, plates, load-bearing walls) will help a home inspector to do a better home inspection. Even though most building components are not readily accessible and are not readily visible to a home inspector performing a home inspection on an existing (already built house), it's important to know how buildings and homes are built. Sometimes defects can be seen by a home inspector, because the hidden, covered, or inaccessible system or component has a problem.

What's an Arc Flash?

An arc flash occurs when a flashover of electric current leaves its intended path and travels through the air from one conductor to another, or to neutral or ground. It often happens unexpectedly and can be explosive but brief, or it can last seconds and be rather visually spectacular. It can cause a little damage or it can disable a system and require the replacement of equipment. An arc flash of any size is quite dangerous because its path is unpredictable; it will be attracted to the nearest item with the greatest conductivity, such as an unsuspecting rodent or house pet, or a person. An arc flash can cause a serious electrical burn or even fatal electrocution.

All electrical systems require a means of disconnection so that the service can be shut down quickly if any dangerous conditions exist. In this section, we will look at the types of disconnects, and the common problems that need to be reported.

Many people use the name Romex® when referring to type-NM cable. Romex® is a trademarked name that has come into common usage for referring to plastic-covered wires, but type-NM just means "non-metallic" and also applies to other cable styles.

This is often seen by the home inspector as the supply conduit to outside installations, such as air-conditioning compressors.

Wire types for North American wiring practices are defined by standards issued by Underwriters Laboratories, the Canadian Standards Association, the American Society for Testing and Materials, the National Electrical Manufacturers Association and the Insulated Cable Engineers Association.

Knob-and-Tube

Knob-and-tube wiring is so named because of the porcelain fittings used to support and insulate the conductors from the timber components in the home. The knob holds the wire away from rafters and joists, while the tubes are inserted into holes bored though joists and studs to protect the conductor and its rubber insulation.

Circuit Breaker Panels

These are probably the most common type that home inspectors will come across, as they have replaced fuse panels over the last 40 years or so. As we saw for fuse panels, breakers are far from foolproof and require some particular checking.

Moisture

A crucial point to always bear in mind is that water can be a very good conductor of electricity. Any panel that is damp or wet should NOT be touched or opened by an inspector.

Remote Distribution Panels

Although this topic is covered in other areas, because the emphasis is on safety, it's important to review.