Twenty years in this trade, and few sentences change a home sale faster than "the house has knob and tube." In older pockets of downtown Brampton, Toronto, Richmond Hill and Old Oakville, I still find original 1920s–1940s wiring in otherwise beautiful homes. Here's what it means for insurance, safety, and your wallet — Updated for 2026, because the insurance landscape keeps tightening.
What knob and tube actually is — and why it's a problem now
Knob and tube (K&T) was the standard residential wiring method in Ontario from roughly 1900 to the late 1940s: individual conductors run through ceramic knobs and tubes, with no ground wire, insulated in cloth and rubber. It was perfectly safe for the electrical loads of 1935 — a few lights and a radio.
It struggles with the loads of 2026 for three reasons:
- No ground wire — modern electronics and appliances expect one.
- Aged insulation — after 80+ years, the cloth and rubber become brittle. Bury it under attic insulation, as so many energy retrofits do, and it can overheat.
- Amateur modifications — decades of handyman splices, taped junctions buried in walls, and circuits extended past their design. This, honestly, is the biggest real-world fire risk.
Why Ontario insurers are walking away
Ontario home insurers have tightened dramatically over the last few years, and their positions cluster into three groups:
- Refusal: many mainstream carriers simply won't write a new policy on a home with active K&T.
- Conditional coverage: some insure it only if a licensed electrician certifies the system is unmolested — with higher premiums, higher deductibles, and sometimes an exclusion on fire loss caused by the wiring. The precise loss you were buying insurance for.
- Renovation triggers: most policies require any accessible K&T to be replaced when you renovate — insurers treat a permit application as their inspection moment.
If you're selling, expect buyers' insurers to demand removal or certification. If you're buying, a "knob and tube present" note in the inspection report can stall your financing approval until it's resolved. Neither is a good surprise two days before closing.
Which Ontario insurers still write K&T policies?
The honest answer, as of 2026: a shrinking minority — and it changes often enough that any list I printed would be stale within months. What I can tell you from working with buyers, sellers and brokers across the GTA:
- Mainstream national carriers have largely exited K&T for new business; renewal of an existing policy is easier than a new one.
- Specialty and high-risk insurers — often reached through a broker rather than direct — will still write older-wiring homes, at a price.
- Broker channels matter. A broker who specializes in older homes can sometimes place a policy a direct insurer declines outright, sometimes conditioned on an electrical inspection report.
The consistent requirement across every carrier that still plays? Documentation. Either proof of replacement or a written electrical safety assessment from a licensed ECRA contractor. That letter is the single most useful piece of paper in this whole process.
The ESA inspection letter: your fastest first step
Before you spend a dollar on replacement — or walk away from a house you love — get the facts in writing. Our electrical safety inspection documents exactly what wiring the home has, what condition it's in, what (if anything) has been modified over the decades, and whether any portion can honestly be certified. You walk away with a written report you can hand to your broker, your buyer, or your lawyer.
Sometimes the answer is genuinely good news: a home where the K&T was fully removed in 2008 and the panel updated last year. Sometimes it's "three bedrooms are still live knob and tube, buried in blown insulation." Either way, you now have a document instead of a rumour — and brokers can work with a document. This inspection is the lead item on every K&T file we open, and it routinely saves clients thousands of dollars in either unnecessary work or avoidable panic.
What replacement costs in 2026
Full knob and tube replacement means new modern wiring to every receptacle, switch and fixture on the old circuits, a new grounded panel (many K&T homes also have 60-amp fuse service — see our panel upgrade service), and an ESA inspection with certificate.
| Home size / type | Typical full replacement (2026, CAD) |
|---|---|
| Small bungalow / cottage (under ~1,000 sq ft) | $6,000 – $10,000 |
| Typical 2-storey semi or detached (~1,500 sq ft) | $8,000 – $15,000 |
| Large, finished or heritage home (2,500+ sq ft) | $15,000 – $25,000+ |
The wide ranges reflect access: homes with unfinished basements and attics are straightforward — we fish wire with minimal drywall damage. Fully finished homes with plaster walls take longer. Most family homes take three to six working days with power on overnight, and we schedule around your household. Partial replacement (one floor, or abandon-in-place with new home-run circuits) can cut the cost substantially for homes on a tighter budget — the assessment tells you which approach fits.
What a replacement week looks like in your home
Homeowners picture demolition; the reality is quieter. Day one we map the circuits and open strategic access points. The middle days are fishing new cable through walls and ceilings from the basement and attic, replacing devices as we go — we protect floors and furniture, keep power on to finished rooms overnight, and tidy before leaving each day. The ESA rough-in inspection happens before walls close, and the certificate arrives after final inspection. Most families stay home through the whole job; the disruption is real but manageable, and nothing like a renovation.
What the premium consequences look like
Every file is different, but the pattern we see across GTA clients: insuring a K&T home through a specialty carrier commonly costs 15–40% more than the same home rewired, often with a higher deductible and an electrical-inspection condition. On a $2,000 annual premium, that's $300–$800 every single year — which means a full replacement at $10,000 can pay for itself in insurance savings alone within a decade, before counting the sale-price benefit or the peace of mind. Get your specific numbers from your broker; treat mine as directional, not a quote.
Can knob and tube ever be grandfathered?
Sellers ask me this constantly, so let's be direct: the Ontario Electrical Safety Code doesn't force you to replace wiring simply because it's old. In that narrow legal sense, it can be "grandfathered." But that protection ends at the insurance company's underwriting desk — and increasingly, they don't care about grandfathering. Some will accept an electrical safety inspection and certification from a licensed contractor if the system is genuinely unmolested, but that certification is getting harder to give honestly: after eighty years, most systems I open up have been touched by someone. The practical rule I give clients: if you're selling within five years, budget for replacement; it's cheaper than the price reduction a nervous buyer will negotiate.
Buying or selling a house with K&T
Buyers — make these four checks part of your offer process:
- Ask for the insurer's position in writing — before waiving financing conditions, not after. Your broker can confirm whether the home's wiring is insurable at reasonable terms.
- Get an actual electrical inspection, not just a general home inspection. Home inspectors identify visible K&T but can't open walls or assess the whole system.
- Check the panel, not just the wiring. Fuse boxes, 60-amp service and double-tapped breakers often travel with knob and tube.
- Ask what was already replaced. Partial replacements are common and can be worse than none — new owners assume the whole house is modern when three rooms aren't.
Sellers — a completed ESA-certified replacement with the certificate in hand is a genuine selling feature. Buyers pay more for documented, insurable electrical, and in older downtown Brampton streets where most of the stock is pre-war, a rewired home stands out the day it lists.
The Ontario-specific angle: ESA, not NEC
One warning for anyone researching online: most knob and tube content is American, written against the US National Electrical Code. Ontario governs this under the Ontario Electrical Safety Code and the Electrical Safety Authority — the inspection regime, the certificate of acceptance, and the rules about what must be brought up to standard when work is done are all provincial. When your insurer or buyer asks for documentation, it's an ESA certificate or a report from an ECRA-licensed contractor they want — not a generic US-style inspection. Make sure whoever you hire holds an ECRA electrical contracting licence and files the inspection properly.
Questions homeowners ask me
Is knob and tube wiring illegal in Ontario?
No — and this surprises people. The Ontario Electrical Safety Code doesn't ban existing K&T or force its removal; new installations simply haven't been permitted for decades. The legal permission and the insurance reality are two different things, though. The code may grandfather your wiring while your insurer declines to cover it, which is why the inspection letter matters more than the statute book.
Can I get insurance with knob and tube wiring?
Often yes, but through a narrowing door. Expect to need a written electrical assessment, plan on higher premiums and deductibles, and work through a broker rather than a direct insurer. Some carriers accept K&T only if it was certified within a recent window. Get the answer in writing from your specific broker before you waive conditions on a purchase — never after.
Is it safe to live in a house with knob and tube?
Unmodified K&T on light-load circuits is less dangerous than its reputation. The real problems are the modifications: handyman splices, buried junctions, circuits extended past their design, and insulation packed over ageing conductors. That's why I can't certify most systems honestly — after eighty years, someone's been in there. An assessment tells you which category your home falls into.
Can I remove it myself to save money?
Removing old wire is easy; replacing it safely is the job. Every circuit you abandon needs new cabling run to code, and the finished work requires an ESA inspection and certificate. Homeowners who DIY the removal and hire halfway through usually pay more than a straightforward professional job, because fishing wire through finished walls of a partially stripped house is slower than doing it in the right order.
Does a home inspection cover the wiring?
A general home inspection identifies visible knob and tube — it can't open walls, test insulation condition, or map circuits. Treat the home inspection as a screening tool and follow it with a proper electrical assessment before you make any final decisions. The two documents answer different questions.
Will replacing it increase my home's value?
Documented, certified electrical is one of the few invisible upgrades that pays at resale. In older Brampton and Toronto streets where most listings carry the same wiring warning, "rewired 2026, ESA certificate available" genuinely differentiates — and removes buyers' favourite negotiation lever. Sellers routinely recover most of the replacement cost in sale price and time-on-market.
The bottom line
Knob and tube isn't a death sentence for a house — it's a known, fixable condition with a real cost attached. The expensive mistakes come from ignoring it, half-fixing it, or discovering it after closing. Whether you're buying, selling or staying put, the first step is the same: an honest, documented assessment from a licensed electrician.
We replace knob and tube across the GTA with ESA certification, and we'll tell you straight whether your home needs full replacement, can qualify for a safety certification, or is fine as it sits. Call 416-903-7166 — assessments are free.
