Usually the question doesn't even get to "constructor" — Ontario's OHSA carves work on your own private residence out of the Act before that label would apply.
Short answer
Generally no, because the question doesn't arise for most private-residence work. Ontario's guide to the OHSA's application provisions confirms that under section 3(1), the Act does not apply to "work performed by the owner or occupant, or a servant of the owner or occupant to, in or about a private residence." If the exemption applies, the homeowner isn't being measured against constructor duties at all — those duties belong to businesses and projects the Act covers in the first place.
The exemption is about the homeowner's own status, not about the trades working on the property. Each contractor and subcontractor a homeowner brings in remains a separate employer subject to the OHSA in its own right — the private-residence carve-out relieves the homeowner of Act obligations, it does not extend that relief to the businesses they hire.
Where the Act does apply — a project a business is running, or work that falls outside the "in or about a private residence" description — the constructor role carries real duties. The same guide describes the constructor's obligation under section 23 to "ensure that every employer and every worker performing work on the project complies with the OHSA and the regulations." That is a substantial coordination duty, which is exactly why the private-residence exemption matters so much when it does apply.
A source commonly pointed to for this question actually addresses a different problem entirely: it walks through which Ontario court — Small Claims or Superior — a homeowner should sue a contractor in over a botched renovation. That's a civil-dispute-forum question, not an OHSA designation question, and the two shouldn't be conflated when you're trying to work out who owes what safety duties on site.
The private-residence exemption is Ontario-specific OHSA language, and other provinces frame their equivalent carve-outs differently — don't assume a homeowner project is automatically exempt outside Ontario without checking the applicable provincial Act. And even within Ontario, the exemption turns on the work being "in or about a private residence," which is doing real work in that sentence: a renovation on a rental or income property, or work run through a business rather than the owner personally, sits on shakier ground. When in doubt about who's coordinating the site, the same logic that decides whether a JHSC is required also depends on knowing who the responsible party actually is, and it interacts with who has authority to enforce site rules in the first place.
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