Can a parging contractor work on my foundation if there's knob-and-tube wiring visible in the basement wall?

Knob-and-tube wiring visible in a basement wall does not automatically stop parging work from proceeding on the exterior foundation, but it raises serious safety and insurance concerns that need to be addressed before any contractor starts work.

Knob-and-tube (K&T) wiring was standard in Toronto homes built before approximately 1945 — which covers a significant portion of the housing stock in established neighbourhoods like The Annex, Roncesvalles, Leslieville, East York, and older parts of North York and Etobicoke. If K&T is visible in your basement wall, it almost certainly runs through other parts of the home as well.

The parging contractor's work is on the exterior foundation surface, so in most cases they won't be directly interacting with the wiring. However, if the K&T is exposed in the basement wall cavity and the parging work involves any drilling, chipping, or mechanical fastening into the foundation wall (for example, installing metal lath for a stucco or thick parging application), there is a real risk of disturbing wiring that runs through or near the wall assembly. A competent contractor should flag this before starting and may decline to work until the electrical situation is clarified.

The bigger issue is your home insurance. Most Ontario insurers either refuse to cover homes with active knob-and-tube wiring or charge significantly higher premiums. If you're undertaking any renovation work — including foundation parging — and your insurer discovers active K&T during a claim, coverage can be denied. Before starting any project on a pre-war home with K&T, it's worth a quick call to your insurer to understand your policy's position.

From a practical standpoint, if the K&T is visible in the basement wall, have a Licensed Electrical Contractor (LEC) assess it before parging work begins. They can determine whether the wiring is active or abandoned, whether it's safely isolated, and whether any remediation is needed. This assessment typically costs $150-$300 and gives you — and your parging contractor — clarity before anyone picks up a chisel. Any electrical work that follows requires an ESA permit and inspection.

The parging contractor is not an electrician and should not be making judgements about the safety of the wiring — that's outside their scope. A good contractor will simply note the concern and ask you to get it sorted before they proceed. If a contractor dismisses the K&T entirely and starts chipping away without asking any questions, that's a red flag about their overall approach to the job.

For the electrical side of things, find a Licensed Electrical Contractor through the Toronto Construction Network at torontoconstructionnetwork.com — and once the wiring situation is sorted, Toronto Parging can match you with a local masonry professional to get the foundation work done properly.