Electrical risks in older homes explained

In B.C., approximately 180 house fires are reported every year due to faults in residential
electrical systems. This represents approximately10% of all reported fires in the province, yielding 9% of
all residential property loss. Total losses due to electrical fires between 2004 and 2007,including buildings and contents, were $71 million. The vast majority of electrical fires occur in residential buildings. The B.C. Fire Commissioner’s Office reports that, for the period2004 to mid-2007, almost all of the electrical fires in B.C. were residential. In general, older homes show a particularly higher degree of electrical fire hazards than newer homes. It’s no wonder then that insurance companies are concerned about electrical hazards in older homes. In recent years, “knob-and-tube” electrical wiring has been singled out by insurers as being a significant hazard and direct contributor to electrical fires in Canadian houses.

Underwriting requirements have also singled out homes with less than 100 amp service as being of high hazard. Such concerns have led to owners of older houses being obligated to spend many thousands of dollars to have their homes rewired with modern cabling or upgraded to a 100 amp service so that their homes can be insured. I’ll explore the facts to help you gain a better understanding of what the electrical hazards in older and newer homes really are.

That way, you will know what to look for when visiting your clients ’homes, you’ll be better able to guide your personal lines clients on their electrical fire mitigation needs, and you’ll be more comfortable talking with and even enlightening your personal lines under writers on the facts. The leading causes of residential electrical fires.

Numerous studies have shown that the leading cause of electrical fires in homes is not knob-and-tube wiring,60-amp electrical services or fuse boxes per se, but “handyman tinkering”. This is the situation whereby an inexperienced homeowner or another wise unauthorized individual has made changes to an original electrical system that are not in compliance with the electrical code. The phenomenon of handyman tinkering first became widespread in the 1960s as the trend towards do-it-yourself home renovations emerged. It still goes on today as owners of older homes look to save money on their renovation work. Faulty circuit breakers (not to be confused with the older technology – fuses) also play a significant role in causing. The predominant hazards found were a result of handyman tinkering. Data source: 500 pre-1950 homes in the Greater Vancouver area, examined by Power Check in 2007-09.Homes with dangerous wiring Homes with secondary suite All homes pre 25 years80%20%
electrical fires. One test conducted in B.C. in the 1970sfound that circuit breakers just 15 to 20 years old were faulty and contributed to electrical fires. Regardless of what it is or how old it is, deterioration of an electrical conductor will occur when it is subjected to electrical or physical abuse. As such, modern electrical cables are just as often found to be in a state of peril as knob-and-tube conductors. For example, live electrical cables for electric water heaters are frequently found dangling in basements, having been disconnected when the electric heater was replaced with a natural gas one. Overall, it is faulty and misleading for anyone – under writers, brokers or their clients – to make assumptions about residential electrical safety simply based on the presence of older wiring or electrical services. One assumption that can
clearly be made, however, is that as a house ages, the likelihood of electrical risk increases. In a house that is greater than 25 years old, the likelihood of electrical risks being present is particularly significant. Based on the author’s study of 500 homes selected at random in the Greater Vancouver area, all being more than 40years of age, 95% of them had one or more electrical fire hazard conditions present.

All of these hazards were as a result of handyman tinkering. In nearly all of the cases, the hazards were the result of unqualified individuals incorrectly adding extra circuits or altering existing circuits without adherence to the electrical code. If the house had a secondary suite (i.e., a basement suite or other), the number of dangerous add-on circuits or tampering with the original electrical system were particularly more prevalent. When your client purchases a home with a secondary or basement suite, it is always beneficial to recommend that he or she has an inspection of the electrical system done by a professional in the event the suite was added after the original construction and was wired by a handyman.

In addition to fixed-wiring hazards, many fire hazards identified were the result of actions taken by the occupant. These were much more common in rental properties and included:

  • Use of broken and deteriorated electrical extension cords
  • Over loading of circuits with heat-producing equipment
  • Stapling extension cords to walls, baseboards and under eves (for the wiring of outdoor Christmas lights)
  • Running electrical cords under rugs or in high traffic areas

Some insurance companies require regular inspections of rental properties. Others simply ask about the frequency of property inspections and who does them, such as the owner or property manager. Regardless, considering the hazards of rental properties that include but are not limited to electrical hazards, rental property owners should always be encouraged to inspect their properties on a regular basis. Knob-and-tube wiring Knob-and-tube wiring was the standard wiring in all homes built before 1950. It is still present to some degree in the vast majority of occupied houses in B.C. that were built pre-1950.Contrary to its bad reputation; knob-and-tube wiring is a well-engineered system. It consists of rubber-insulated electrical conductors wrapped in a flame-retardant cloth that are supported and secured throughout the house by porcelain knobs and tubes.

The wiring is made of heavy-gauge copper which, when compared to the cable commonly used in the wiring of houses today, gives off less heat. Knob and-tube conductors are typically well spaced, usually at eight-inch intervals, which prevents short circuits occurring along the length of the wires. And, to ensure that the electrical splices (i.e., the wire-to-wire connections) are sound, they are all soldered.

This minimizes the opportunity for connections to become loose and electrical arcing to occur.


Finally, another positive fact about knob-and-tube wiring is that it was seldom installed by non-professionals. The cost to completely replace knob-and-tube wiring in a single-family detached home is very expensive, typically in the $15,000 to $20,000range. Therefore, in the best interests of your homeowner clients, a careful examination of the knob-and-tube wiring should always be carried out by a professional electrical inspector before those clients are asked to take such drastic measures as having it entirely removed and replaced. Remind your clients and discuss with your personal lines underwriters that, while electrical fire hazards are usually found in homes with knob-and-tube wiring, the hazards are usually not due to the knob-and-tube itself and are typically far less expensive to fix than totally replacing the wiring.


Ungrounded three prong receptacles Knob-and-tube wiring was designed to provide power to two-prong “old-style” power outlets, properly known as “receptacles”. These receptacles did not provide ground protection. While knob-and tube wiring was phased out by the early 1950s, ungrounded receptacles (i.e., two-prong outlets) wired by a twin conductor cable were still installed up to the mid-1960s.In the 1960s, the applications for electricity expanded, with new appliances being developed that required ground protection for safe operation. In 1966, the Canadian Electrical Code required that all power outlets be of grounded, three-prong type. Unfortunately, many homeowners simply swapped their two-prong receptacles with the new three-prong ones without also providing the necessary ground protection.


This “retrofit” of three prong receptacles onto an ungrounded wiring system is hazardous.

It provides an opportunity to plug in appliances requiring ground protection when, in fact, there is none. These ungrounded three prong receptacles can be found in a staggering 99% of homes with knob-and-tube or ungrounded wiring, hence the “high risk” rating given to so many older homes. So, again, it is not the older wiring system by itself that is hazardous, it is what has been added to it later that creates the problem. Fortunately, there is a simple and cost-effective solution to providing ground protection to knob-and-tube fed receptacles, provided that the rest of the electrical system has not been tampered with.


This solution is the Ground Fault Circuit Interrupter (GFCI), which provides excellent ground protection to receptacles. Compared to knob-and tube replacement, GFCIs are inexpensive and easy for an electrical contractor to install and they meet the electrical code. They can be installed at each power outlet in the home or at the electrical panel. If you come across a situation where by a home owner client is being asked to have his or her knob-and-tube wiring removed and replaced because it is ungrounded, discuss with your client and the underwriter that GFCIs provide a safe and inexpensive solution for ground protection of ungrounded (knob-and-tube) circuits. You could end up saving the client a great deal of money, and you’ll save the account.60-amp service size refers to the amount of electricity that can be supplied to a home.

Until the 1970s, 60-amp electrical service was the standard in the majority of homes. Correct service size is determined from a “demand calculation” carried out by an electrical contractor according to a calculation procedure laid out in the Canadian Electrical Code. This calculation determines the minimum size of electrical service that is acceptable

in a home. The presence of a 60-ampservice is not necessarily an automatic red flag that a house is at high risk of electrical fire. If the electrical power demand of the existing house with 60-amp service has not been exceeded and all other conditions with the service and electrical panel comply with the electrical code, the 60-amp service is acceptable provided that no new circuits are to be added.

Only if the demand calculation indicates that a larger service is required or only when there are concerns with the existing 60-ampservicesuch as an insufficient number of circuits or overrated main fuses or breakers, should the existing60-amp service be deemed to be unacceptable.

Discuss this with your underwriters, as an upgrade from a 60-amp service to a new 100-amp service would cost your homeowner client a few thousand dollars, which would be a waste of money if the existing service is still acceptable.


Optimizing electrical risk management the best method for selecting houses to be checked for electrical hazards is to base the potential risk on the age of the house. In other words, if a house is older than a defined age, assume it to beat high electrical risk unless proven otherwise. The common underwriting practice is to demand that all houses25 to 30 years old or more should be inspected. Similarly, the author recommends that setting the benchmark at25 years of age is optimum, as this would include approximately80% of all homes with dangerous electrical hazards in them. The degree of dangerous electrical hazards with the potential to create fires in older homes is truly significant, but by working together with professionals in home electrical systems, electrical fires in homes can be prevented one house at a time. Correct evaluation of the risks will result in safe houses, satisfied underwriters, happy homeowner clients and, ultimately, happy insurance brokers.



Brian Cook, Power Check Electrical

Safety Services Inc., is a BC

Trade-qualified electrician and an

Electrical Field Safety Representative,

Class B (equivalent to Master

Electrician). www.powercheck.ca