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Aluminum and Knob-and-Tube Wiring in Ontario: How to Tell, What ESA Allows, What Insurers Ask For, Pigtailing vs Rewiring and the Cost
Electrical & Lighting
Old Wiring: What Can Stay, What Has to Go, and What Your Insurer Will Ask Before Either
Two kinds of old wiring cause most of the phone calls: knob-and-tube in older houses, and aluminum branch wiring in houses built from the mid-1960s to the late 1970s. Neither one is automatically a fire waiting to happen, and neither one is automatically fine. ESA says when each may stay, many insurers want an inspection before they will cover the house, and the repair ranges from a few thousand dollars to the price of a good used truck. This page sorts out which you have, what is allowed, and what it costs.
What Each One Is
Knob-and-tube is two separate wires, each run on porcelain knobs along the framing and through porcelain tubes where it passes through a joist, with rubber and cloth insulation and no ground wire. It was built to shed its heat into open air, which is why insulation and knob-and-tube do not mix; that question has its own knob-and-tube and insulation page.
Aluminum branch wiring is solid aluminum on the ordinary 15 and 20 A circuits, from houses built between the mid-1960s and the late 1970s. The wire in the wall is rarely the trouble. The trouble is at the screw on the end of it, where aluminum and the wrong device or connector make a joint that loosens and heats over the years. The big aluminum cables feeding the panel itself are normal and are not what this page is about.
How to tell, without opening anything:
- In an unfinished basement or attic, porcelain knobs or tubes on the joists mean knob-and-tube, whether or not it is still live
- Exposed cable in the basement printed “AL” or “ALUMINUM” means aluminum branch wiring
- A house built from about 1965 to 1979: assume aluminum is possible until someone checks
- The home inspection report, if you bought with one, usually flags either
Do not take covers off receptacles or the panel to look. An electrician confirms it in an hour, and the assessment is cheap.
What It Costs
| Job | Range, before HST | Note |
|---|---|---|
| Aluminum wiring assessment | $100 to $250 | an electrician confirms what is there |
| Electrical safety inspection, written report | $250 to $450 | for insurance or a purchase |
| Pigtailing aluminum with AL-CU rated connectors | $40 to $100 a point | every termination |
| Typical house, 40 to 60 points | $2,000 to $6,000 | |
| Full copper rewire instead | $8,000 to $20,000 and up | plus patching |
| Knob-and-tube replacement, 1,500 to 2,500 sq ft, with the panel | $12,000 to $25,000 | large older houses to $45,000 |
| Plaster patching after a knob-and-tube job | $2,500 to $8,000 | plus paint |
October 2026 prices. The ESA notification fee is extra and small; the contractor files it. Rewiring in general is on the cost to rewire a house page.
Why Ontario prices are all over the map: the contractors and price guides we checked for this page quoted the same repair very differently. Pigtailing aluminum ran from $40 a point (a Toronto contractor) to $100 a point (an Ottawa contractor), which on a 50-point house is $2,000 against $5,000. For a full rewire, a national home-services marketplace said $8,000 to $20,000 and a GTA contractor $15,000 to $30,000 for 1,200 to 2,500 sq ft, with the patching often extra. Access to the walls, plaster vs drywall, the panel, and whether patching is in the price make most of the gap. Budget about $70 a point for pigtailing, and get two or three quotes on the same written scope.
What ESA Says May Stay
Knob-and-tube may remain in place if it is on 15 A protection, the conductors are sound, and nobody has added outlets to the original circuit so as to overload it. It should be replaced where the wires show mechanical abuse or deterioration. Any change to it needs an ESA notification, like any other electrical work.
Aluminum may stay too, connected properly. Devices of 20 A or less on aluminum must be marked CO/ALR (receptacles may be marked AL-CU instead). Connectors must be marked AL-CU or CU-AL. Push-in “backstab” terminals are never used with aluminum. Copper pigtails are allowed, joined to the aluminum with a marked connector, which is the repair most electricians mean by “pigtailing”.
Do not wait on this one: a receptacle or switch plate that is warm or discoloured, lights that flicker when nothing else is running, or a burning smell means turn that breaker off and call a Licensed Electrical Contractor today. Not on the weekend. Today.
What Insurers Ask For
ESA’s own notices say that many insurers will not provide or renew coverage on houses with knob-and-tube, and for aluminum many will not without an inspection. Some want the wiring repaired or replaced and a copy of the ESA Certificate of Acceptance; some want aluminum replaced with copper.
So the order matters. Before you hire anybody, ask your insurer, in writing, exactly what it wants: an electrician’s report, an ESA-inspected repair, or replacement. Then price that, not something else. Contractor websites print premium figures for old-wiring houses; I could not find an insurer behind any of them, so I do not repeat them.
If you are buying, ask the insurer before you waive conditions. Finding out on closing day that nobody will write the policy is a bad day.
Pigtail, Rewire or Both: Three Houses
A 1972 split-level in Barrie, aluminum throughout, no renovation planned. Assessment $175, the middle of $100 to $250. Fifty points at $70 is $3,500. Together $3,675 before HST and the ESA fee, against $8,000 to $20,000 and up to rewire. Pigtail it, keep the Certificate, send a copy to the insurer.
The same house, with the kitchen and basement being gutted. Rewire those rooms in copper while the walls are open, and pigtail the rest. Paying to pigtail a kitchen you are about to tear out is paying twice.
A 1925 two-storey in Orillia, 1,800 sq ft, knob-and-tube still live upstairs. Replacement with the panel, $12,000 to $25,000, plus plaster patching at $2,500 to $8,000: $14,500 to $33,000 before paint. While the walls and ceilings are open, that is the cheapest chance the house will ever get for air sealing and insulation; the older homes insulation page covers what to do.
Where People Go Wrong
- Swapping devices with whatever the store had. On aluminum, an ordinary receptacle with push-in terminals is the exact thing ESA says never to do. Doing your own work still means filing your own notification.
- Adding outlets to a knob-and-tube circuit. That is one of the conditions for leaving it in place, gone.
- Blowing insulation into the attic first. Read the insulation page before anyone brings a hose.
- Not telling the insurer. ESA says homeowners should. A claim is a bad time for them to find out.
- Skipping the record search when buying. The ESA permit page shows how to check what was permitted.
Questions people ask
Is aluminum wiring legal in Ontario?
Yes, if it is connected properly: CO/ALR devices (receptacles may be AL-CU), connectors marked AL-CU or CU-AL, and no push-in terminals. Copper pigtails joined with a marked connector are allowed. Many insurers still want an inspection.
Can I get home insurance with knob-and-tube wiring?
Sometimes. ESA says many insurers will not insure or renew without an inspection or replacement. Ask your insurer in writing what it needs before you hire anyone.
How much does it cost to pigtail aluminum wiring?
$40 to $100 a point in Ontario in 2026, and a typical house of 40 to 60 points runs $2,000 to $6,000 before HST. An assessment first costs $100 to $250.
Does knob-and-tube have to be replaced?
Not automatically. ESA allows it to remain on 15 A protection if the conductors are sound and the circuit has not been overloaded with added outlets. Where it shows abuse or deterioration, it should be replaced, and your insurer may want it gone regardless.
How do I know if my house has aluminum wiring?
Look for “AL” or “ALUMINUM” printed on exposed cable in the basement, and be suspicious of any house built from the mid-1960s to the late 1970s. Do not open devices or the panel; an electrician can confirm it in an hour.
Price the rewire before you decide
The whole-house electrical cost calculator prices a rewire by the square foot with a patching allowance, so you can set pigtailing against replacement on your own house. If you already have quotes, the $99 review reads up to three of them, or one quote plus the panel photos, and tells you what each one left out.
Sources and further reading
- ESA: knob and tube wiring: when it may stay, when it should go, and what insurers often ask for.
- ESA: aluminum wiring: what to look for in a 1960s and 1970s house, the approved repair methods and the insurance question.
- Electrical Safety Authority: homeowners: who may do electrical work in Ontario, why a hired electrician must be a Licensed Electrical Contractor, and what the Certificate of Acceptance is for.
