In This Article
- OHSA Framework: Who Is Responsible for What
- O. Reg. 213/91: Construction Projects Regulation
- Shoring Design: When a P.Eng. Seal Is Required
- Formwork Engineering Requirements
- Trench and Excavation Requirements
- Structural Stability of Existing Buildings During Construction
- Section 30: Designer's Duties
- Concept Safety Plan
- Engineer as Supervisor Under OHSA
- Due Diligence Defense
- Frequently Asked Questions
OHSA Framework: Who Is Responsible for What
The Occupational Health and Safety Act (OHSA) (R.S.O. 1990, c. O.1) is Ontario's primary workplace safety statute. On construction projects, OHSA defines clear roles and responsibilities:
| Party | OHSA Role | Key Obligations |
|---|---|---|
| Project Owner/Client | "Owner" | Register the project with Ministry of Labour; notify MOL of project start; ensure constructor compliance |
| General Contractor | "Constructor" | Overall responsibility for all workplace health and safety on the project; ensure all employer and worker compliance |
| Trade Contractors | "Employer" | Employer's obligations to their workers; provide PPE, safe equipment, trained workers |
| Structural Engineer | "Supervisor" (when directing workers) and "Designer" (under s.30) | Employer duties when supervising workers; designer duties regarding construction hazards |
| Workers | "Worker" | Follow safe work procedures, use PPE, report hazards |
O. Reg. 213/91: Construction Projects Regulation
Ontario Regulation 213/91 (Construction Projects) is the detailed technical regulation under OHSA that applies to all construction projects in Ontario. It covers everything from excavation and shoring to fall protection, cranes, and electrical safety. For structural engineers, the most directly relevant sections are:
- Part IV — Foundations and Excavations (ss. 222–246): Requirements for excavation safety, slope stability, and shoring design
- Part VI — Formwork and Falsework (ss. 87–92): Requirements for concrete formwork and supporting falsework
- Part XII — Structural Work (ss. 148–165): Requirements for steel erection, structural stability, and temporary support during construction
Shoring Design: When a P.Eng. Seal Is Required
O. Reg. 213/91 requires site-specific professional design for shoring systems in a range of higher-risk situations. Common triggers include:
- Deeper or more hazardous excavation conditions where the regulation does not allow a simple generic compliance path
- Any shoring adjacent to or supporting an existing structure
- Any non-standard shoring arrangement or site condition that cannot be safely addressed through a generic system detail
- Any bracing or support of an existing building during renovation, alteration, or demolition
Urban projects rarely fit a generic shoring assumption. Adjacent foundations, utilities, traffic loads, groundwater, and constrained access often push even modest excavations into a site-specific engineering review path.
Formwork Engineering Requirements
O. Reg. 213/91 requires professional design for formwork or falsework once the current project conditions exceed the simple cases contemplated by the regulation. Common triggers include:
- Heavier or deeper concrete pours
- Larger placement volumes or unusual pour sequencing
- Multi-storey reshoring or falsework conditions
The formwork drawings should include the loads, component sizing, shoring layout, reshoring strategy where applicable, and any construction-stage limitations needed for safe placement. These drawings must remain available on site throughout the forming and pouring operations.
Formwork stripping should follow the design criteria, the current specification, and the engineer's review of strength-gain evidence or other approved verification methods.
Trench and Excavation Requirements
Below-grade work in Ontario must comply with O. Reg. 213/91 Part IV. Key requirements:
- Excavations must be sloped, benched, or supported in accordance with the current regulation and the actual soil and site conditions
- Workers must not enter unsupported trenches or excavations where the regulation requires a protected configuration
- Before any worker enters an excavation, ground conditions must be assessed by a competent worker
- Water accumulation must be controlled to avoid soil softening and wall instability
- Spoil placement, traffic loading, and adjacent structure effects must be managed so they do not reduce excavation stability
Structural Stability of Existing Buildings During Construction
O. Reg. 213/91 Part XII requires that during construction, alteration, or demolition, the structural stability of existing structures must be maintained at all times. Specific requirements:
- Before any structural member is removed or altered, the method of maintaining structural stability must be determined and implemented
- A P.Eng. must design any temporary bracing, shoring, or support system used to maintain stability of an existing structure during alteration or demolition
- No load may be applied to a floor, roof, or other structure in excess of its permitted loading at any time during construction (no overstacking of materials)
Section 30: Designer's Duties
OHSA Section 30 imposes specific duties on designers of structures. A "designer" includes any person who designs a building, structure, or plant for a project in Ontario — which explicitly includes structural engineers who design or stamp structural drawings. Section 30(1) requires that the designer:
- Consult with a constructor (i.e., discuss with the general contractor or a representative) in the design phase about whether construction will create or be likely to create a hazard to a worker
- Take the results of that consultation into account in completing the design
This requirement applies to the structural engineer as a designer. In practice, it means engineers should engage in constructability reviews, consider temporary conditions during construction (shoring, erection, forming), and document their consideration of construction-phase hazards. The Ministry of Labour has issued guidance that the consultation does not need to be formal — a design team meeting with the GC where construction methods are discussed can satisfy this requirement if documented.
Concept Safety Plan
For large, complex, or high-risk projects, designers prepare a Concept Safety Plan as part of their Section 30 compliance documentation. The Plan:
- Identifies specific construction-phase hazards created by the structural or architectural design
- Recommends mitigation measures for the constructor to address
- Documents the designer's consideration of worker safety during design
- Is typically incorporated into the project's overall Safety Plan by the constructor
Concept Safety Plans are not universally required for all Ontario projects — but for deep excavations, tunnels, buildings with complex temporary works requirements, and any project where the design creates obvious construction-phase hazards, preparing one is both best practice and evidence of due diligence.
Engineer as Supervisor Under OHSA
When a structural engineer is present on-site and directs workers — even temporarily — they may be classified as a "supervisor" under OHSA. Supervisors have specific duties under Section 27, including ensuring workers comply with the Act and are aware of hazards, using PPE, and following safe work procedures. Engineers should be aware of this potential supervisory role and its legal implications whenever they are physically directing construction operations on an Ontario site.
Due Diligence Defense
The OHSA "due diligence" defense allows a party to avoid liability for a safety violation if they can demonstrate that all reasonable precautions were taken in the circumstances. For structural engineers, demonstrating due diligence in Ontario typically involves:
- P.Eng.-sealed design drawings wherever the regulation or the site condition requires engineered shoring, formwork, or temporary support
- Pre-pour inspection of formwork by the engineer or designate before concrete placement
- Field review notes documenting conditions observed and any compliance issues flagged
- Written correspondence when safety concerns are identified — don't rely on verbal direction
- Section 30 consultation documentation, including any Concept Safety Plan prepared
Frequently Asked Questions
Under OHSA and O. Reg. 213/91, Ontario structural engineers may have duties as designers, as authors of temporary works drawings, and in some cases as supervisors when directing site activity. The exact obligation depends on the engineer's role on the project and the hazards created by the work.
Professional design is typically required whenever the excavation or temporary support condition goes beyond a simple generic compliance path, especially near existing structures, in constrained urban sites, or wherever existing-building stability must be maintained during the work.
The formwork engineer designs the falsework system to safely support construction-stage loads, documents the required layout and limitations, and helps establish the criteria for stripping or reshoring once the concrete has achieved the required strength and stability.
OHSA Section 30 requires structural engineers (as designers) to consult with the constructor about construction-phase hazards created by the design, and to take those results into account in completing the design. This obligation must be documented. For complex projects, a Concept Safety Plan should be prepared to illustrate what construction-phase hazards were considered and what the designer recommends as mitigation.
A Concept Safety Plan documents the designer's Section 30 analysis — identifying construction hazards created by the design and recommending mitigation measures. It is especially useful on deep excavations, unusual structural systems, and other projects where the design creates non-obvious construction-phase hazards.
Need OHSA-Compliant Shoring or Formwork Engineering in Ontario?
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