Structural Engineer vs Architect for Toronto Addition Permits

When adding a second storey or rear extension to your Toronto home, the City of Toronto Building Department requires sealed drawings from licensed professionals. The short answer: architects handle design and code compliance for the overall building, while structural engineers ensure your addition won't collapse. Most additions require both, though the scope of each professional's involvement varies based on project complexity.

The confusion between these roles costs Toronto homeowners time and money every year. Some hire an architect expecting structural calculations included, only to discover they need a separate engineer. Others skip the architect entirely, then face permit rejection because their structural drawings lack the required architectural context. This guide breaks down exactly what each professional does and when you need them.

What Architects Do for Addition Permits

Licensed architects in Ontario hold an OAA designation and take responsibility for the overall building design. For a second-storey addition in neighbourhoods like The Beaches, Leslieville, or North York, your architect handles the creative and regulatory puzzle of fitting new space onto an existing structure.

• Floor plans showing room layouts, dimensions, and circulation
• Exterior elevations depicting how the addition integrates with existing architecture
• Building code compliance for fire separations, egress windows, and ceiling heights
• Zoning analysis for setbacks, height limits, and lot coverage in your specific area
• Coordination with other consultants including structural engineers
• Responses to City examiner comments during permit review

Architects think about how spaces flow, how natural light enters rooms, and how your addition affects the streetscape. In heritage conservation districts like Cabbagetown or The Annex, architects also navigate the additional layer of Heritage Planning approval before your permit application even reaches the building department.

What Structural Engineers Calculate

Professional engineers with a P.Eng. designation focus on one critical question: will this structure stand up safely? For Toronto additions, this involves analyzing both the new construction and how it affects your existing home.

A structural engineer's scope typically includes beam sizing for new floor and roof loads, load path analysis showing how weight transfers to foundations, connection details where new framing meets existing walls, and foundation assessment to determine if your existing footings can support additional storeys. In areas with older homes like Etobicoke's Kingsway or Scarborough's Birch Cliff, foundation upgrades often become necessary when adding a second floor.

• Beam and column sizing calculations sealed by the engineer
• Floor joist specifications and spacing requirements
• Roof truss or rafter design for the addition
• Foundation recommendations, including potential underpinning
• Lateral load resistance for wind and seismic forces
• Point load details where beams bear on walls or posts

The structural engineer's drawings get incorporated into your permit set, usually as separate sheets with their own seal. City examiners review these calculations carefully, particularly for second-storey additions where the entire load path changes.

When You Need Both Professionals

For any addition that changes your home's footprint or adds a storey, plan on hiring both an architect and structural engineer. The City of Toronto requires sealed architectural drawings showing code compliance and sealed structural drawings showing the building won't fail. Neither professional can legally seal the other's work.

“

The most common permit delay we see at PermitsHub comes from homeowners who assumed their architect would handle structural, or vice versa. Clarify scope in writing before signing any contract.

Second-storey additions present particular complexity. Your existing first-floor walls, built decades ago, suddenly need to support an entire additional level. The structural engineer must assess whether those walls have adequate capacity or need reinforcement. Meanwhile, the architect ensures the new second floor meets Ontario Building Code requirements for bedroom egress, stair dimensions, and fire separation from neighbouring properties.

Exceptions: When One Professional Suffices

Small rear additions under a certain size threshold may qualify for permit with architectural drawings alone, provided no structural modifications occur to the existing building. However, this exception rarely applies in practice. Even a modest kitchen bump-out typically requires removing a section of exterior wall, which triggers structural review.

Some design-build firms employ both architects and engineers in-house, streamlining coordination. At PermitsHub, we work with both disciplines to produce complete permit packages, so you deal with one point of contact rather than managing multiple consultants yourself.

Interior-Only Renovations

If you're removing a load-bearing wall without adding square footage, you may only need a structural engineer. The engineer designs the replacement beam and posts, and a qualified designer or the engineer themselves can prepare the permit drawings. No architect required. But the moment you change the building envelope or add space, architectural involvement becomes necessary.

Cost Breakdown and Hiring Sequence

Architectural fees for a second-storey addition in Toronto typically run as a percentage of construction cost or a fixed fee based on project scope. Structural engineering fees are usually separate and lower than architectural fees, though complex foundations can increase costs significantly.

Hire your architect first. They develop the design concept and floor plans, then bring in the structural engineer once the layout stabilizes. Engaging a structural engineer too early wastes money, since every design revision requires updated calculations. Once the architect finalizes the design, the structural engineer needs only a few weeks to complete their analysis.

Red Flags in Professional Contracts

• Architect contracts that promise 'full permit drawings' without mentioning structural coordination
• Structural engineers who quote without seeing preliminary architectural plans
• Any professional unwilling to coordinate directly with the other discipline
• Fees that seem dramatically lower than competitors, often indicating reduced scope

Toronto-Specific Permit Considerations

The City of Toronto Building Department has specific submission requirements that differ from surrounding GTA municipalities like Mississauga, Vaughan, or Markham. Toronto requires digital submissions through its online portal, with drawings in specific formats and naming conventions. Your architect and engineer must be familiar with these requirements, or your application faces immediate rejection before substantive review even begins.

Zoning compliance adds another layer. Toronto's zoning bylaws vary dramatically by neighbourhood. A second-storey addition in a Midtown Toronto neighbourhood like Davisville might face angular plane restrictions that limit how high you can build near property lines. In Scarborough, the same size lot might have completely different height and setback rules. Your architect interprets these bylaws; your structural engineer designs within those constraints.

For properties requiring Committee of Adjustment approval for minor variances, the architectural drawings must support the variance application before the building permit can proceed. This sequencing adds months to the timeline, making early professional engagement even more critical.

Getting Your Permit Package Right

A complete permit submission for a Toronto second-storey addition includes architectural drawings showing all floor plans, elevations, and building code compliance, plus structural drawings with sealed engineering calculations. Both sets must reference each other consistently. If the architectural plans show a beam in one location and the structural plans show it elsewhere, the City examiner will issue a revision request.

Before submission, verify that your architect has coordinated beam locations, post positions, and foundation details with the structural engineer. Review the drawing set yourself for obvious inconsistencies. Catching errors before submission saves weeks of back-and-forth with the City.