---
title: "Prime contractor — who owns safety on a multi-employer site"
description: "What a prime contractor is, in the provinces that use the term, what the role has to coordinate, and why the term does not exist everywhere in Canada."
term: "Prime contractor"
definition: "The party designated to coordinate health and safety on a workplace where two or more employers work at the same time. In the provinces that use the term, the designation is made by law or by written agreement, and it does not remove any employer's own duties."
alsoKnownAs:
  - "Constructor"
  - "Principal contractor"
jurisdiction: "Canada"
locale: "en-CA"
publishedOn: 2026-09-06
reviewedOn: 2026-09-06
canonical: "https://safeally.net/en-ca/glossary/prime-contractor/"
sources:
  - label: "Occupational Health and Safety Act, R.S.O. 1990, c. O.1 — duties of a constructor"
    url: "https://www.ontario.ca/laws/statute/90o01"
    publisher: "Government of Ontario"
  - label: "OHS Regulation, Part 3 — rights and responsibilities"
    url: "https://www.worksafebc.com/en/law-policy/occupational-health-safety/searchable-ohs-regulation/ohs-regulation/part-03-rights-and-responsibilities"
    publisher: "WorkSafeBC"
  - label: "Occupational Health and Safety Code, Part 2 — hazard assessment, elimination and control"
    url: "https://search-ohs-laws.alberta.ca/legislation/occupational-health-and-safety-code/part-2-hazard-assessment-elimination-and-control/"
    publisher: "Government of Alberta"
---

# Prime contractor — who owns safety on a multi-employer site

The party designated to coordinate health and safety on a workplace where two or more employers work at the same time. In the provinces that use the term, the designation is made by law or by written agreement, and it does not remove any employer's own duties.

Where several employers share a site, somebody has to own the space between
them — the sequencing, the shared equipment, the crane that lifts over another
crew. British Columbia and Alberta call that party the prime contractor; Ontario
calls the equivalent role on a construction project the **constructor**, with
duties that go further. The vocabulary is provincial, the problem is not.

## What it means in practice

- **The designation must exist before the work does.** By law where the owner
  does not do the work themselves, or by written agreement. On a site where
  nobody was designated, the duty falls back on the owner.
- **Coordination is the substance of the role**: knowing who is on site, when,
  doing what next to whom; a single orientation; one hazard communication; one
  set of emergency arrangements.
- **Each employer keeps its own duties** to its own workers. The prime contractor
  adds a layer; it does not absorb the layers below.
- **Ontario's constructor carries more.** On a construction project, the
  constructor is responsible for compliance by every employer and worker on the
  project — which is why owners take care with how a contract is written, since
  the status follows the arrangement rather than the label.

## What it is not

**It is not the biggest contractor by default.** Size does not create the role and
does not excuse a party from it if the agreement names them.

**It is not a signature.** A designation with no coordination behind it is what an
inspector uses to show that the arrangement was on paper only.

**And it is not everywhere in Canada.** Several jurisdictions have no prime
contractor concept at all and rely on overlapping employer duties instead — so a
national contract template that assumes the term will misdescribe the obligations
in half the country. The closest European instrument is different again: France's
_plan de prévention_ and Spain's _coordinación de actividades empresariales_
impose mutual information duties between companies without ever making one of
them answerable for the others.