Aluminum Wiring

By the Orillia Home Inspector

Certified Building Code Official


Aluminum Wiring and Your Home


Aluminum Wiring Hazards and Solutions.  Primarily in the 1960s and 1970s, many electrical contractors used aluminum wiring instead of copper wiring as a way to save money and lower construction costs. However, a number of electrical fires have been attributed to aluminum wiring. Many building codes have been rewritten to not allow the use of aluminum wire for branch circuit wiring in houses.

Copper vs. Aluminum — The Test Results are in! Tests have demonstrated aluminum wiring has inherent properties that make it more susceptible to fires when it was not installed correctly. Here are some of the problems with using aluminum wiring to conduct electricity. Aluminum does not conduct electricity as well as copper. An aluminum wire generates more heat. Aluminum is more brittle than copper. Wire is more likely to break or crimp if it is brittle. Arcing can occur if a wire breaks or crimps. This can cause very high temperatures inside the wall or ceiling Aluminum is more likely to corrode than copper. Aluminum will oxidize if it comes in contact with moisture. This oxidation removes the pure aluminum and makes the wire thinner. A thinner wire creates more heat when electrical current is running through it. Oxidation also causes the wire to expand, puts pressure on the protective plastic coating on the wire, and can cause the plastic to split. If any of these occur, arcing may result which can cause fires. Aluminum expands and contracts more than copper. This puts additional stress at all connections such as outlets and switches. If these become loose, arcing can occur at these points. If contemplating buying an older home with aluminum wiring or updating a home with aluminum wiring, contact a certified electrician to gain their expertise and opinion regarding the dangers of aluminum wiring.  

How to Tell The wiring that is of concern involves the circuit wiring to your outlets and light switches, and to appliances that us 115 volt current, such as furnace and washing machine. It is a single-strand, solid aluminum wire, silver in color as opposed to the characteristic copper wiring color. Most homes of any vintage employ some aluminum wiring. Often service entrance cables from the street that run to the distribution panel and major appliance circuits (220v) are aluminum. The safety concerns are not with the cables, but rather with branch circuit connections involving the lighting and other 115 v circuits. The Problem Most problems arise with solid aluminum wire, sizes #10 and #12 gauge. These problems concern the ends, or terminations, of the aluminum wire, where they connect under the bonding screws. If the connections are improperly installed, there is a potential for intermittent, hot connections where the wires join to the outlets and switches. Again, the problem is with the connections, and not with the wiring itself. The main difficulty with connections using aluminum wiring is a phenomenon known as cold creep. Aluminums coefficient of expansion (how much it expands when electrical current passes through it) is higher than coppers. Simply put, when aluminum wiring warms up, it expands more than copper does, and when it cools down, it contracts more than copper does. This expansion and contraction, over time, will allow for loosening at the connections. Also aluminum wire needs to be larger than copper to carry the same amount of electricity. Because the wires are thicker, you cannot get the same tightness at the connections. Therefore, they may loosen more quickly. To make the problem worse, all metals oxidize or corrode in an oxygen environment. Copper oxidation forms as a conductor, while aluminum develops as a resistor. This resistance causes heat. Oxidation accelerates when two unlike metals are in contact with each other. This may be part of the source of increased resistance when aluminum wire joins to outlets or switches intended for copper. Eventually the wire may start getting very hot, melt the insulation or fixture its attached to, and possibly even cause a fire. Evaluation of Your Electrical System As mentioned above, aluminum wiring can be just as safe as copper when properly installed. Denver’s Building Department has always maintained-including during the years 1965 to 1977, when aluminum wiring was being installed nationwide- a force of electrical inspectors who themselves are licensed electricians and have worked diligently to ensure that all installations comply with local and national standards. Many of the incidents publicized from other parts of the country simply don’t occur here. Still, any potential electrical problem is a potentially serious problem.




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Inspection Definitions

1. Chimney - vent flue gases from fireplaces or heating equipment.
2.  Chimney flue top or chimney cap (if present)
3.  Chimney crown or chimney top seal
4.  Chimney Flashing seals the roof penetration to avoid leaks into the structure.
5. Masonry fireplace
6. Fireplace ash pit door. 
7.  Fireplace ash pit cleanout door.
8.  Fireplace mantel - horizontal trim attached to wall above fireplace opening.
9. Hearth - flat surface in front of the fireplace, protects flooring from fire.
10. Ridge cap or ridge vent (if present)
11. Ridge board
12. Cripple rafters or Jack rafters (between chimney and house eaves - rafters that do not extend the full distance between house eaves and the roof ridge board)
13. Rafter blocking or cross bridging, also found on floor joists and in some wall framing
14. Soffit or lookout or house eaves. The soffit is the enclosed portion of the roof that overhangs the house walls at the roof lower edges.
15. Roof sheathing or roof decking.
16. Roof shingles (asphalt shingles, clay tiles, slates, wood shingles, or shakes, similar materials)
17. Drip edge (used at lower roof edges or eaves). The drip edge is special metal flashing intended to divert water off of the roof lower edges into the roof gutter system. Drip edges should spill into the gutter, not behind it. 
18. Gutter (attached over or to fascia board) to collect roof drainage and prevent it from spilling down and along the building walls (leaks) and basement (wet basements
19. Downspouts (conduct roof drainage from the gutters to a destination away from the building or into a storm drain system).
20.  Downspout leader or downspout extension (hard to see, behind that front right entry porch column)
21. Gable end and gable-end attic vent. The gable end the house wall on a conventional simple gable roof such as shown in our sketch is the triangular end wall
22. Gable end fascia. The gable end fascia is the trim board attached to the roof edges, extending from ridge to lower roof edge, and where a rake overhang is present, covering the outermost rake rafter or barge rafter.
23. Gable end vent or attic vent at gable end