Structural Engineer vs Contractor in Ontario — What's the Difference?

One of the most common questions homeowners ask is: "Can my contractor handle the structural work, or do I also need an engineer?" The answer depends on what you're building — but for most structural projects in Ontario, you need both.

What Does a Structural Engineer Do?

A structural engineer analyzes loads, designs structural systems, and produces P.Eng.-stamped drawings that are legally accepted by Ontario municipalities for building permit applications. They determine the size of beams, the placement of columns, the reinforcement in concrete, and the connections between structural elements.

What Does a Contractor Do?

A contractor builds the structure based on the engineer's drawings. They manage the construction process, hire trades, source materials, and execute the physical work on site. A contractor cannot design structural elements — they can only build what has been engineered.

When Do You Need a Structural Engineer in Ontario?

• Removing any load-bearing wall
• Adding a second floor or any addition
• Lowering or underpinning a basement
• Building a new custom home or accessory structure requiring a permit
• Any work involving foundation modifications

Can a Contractor Skip the Engineer and Just Build It?

No — not legally. Ontario Building Code requires P.Eng.-stamped structural drawings as part of the building permit application for structural work. A building permit cannot be issued without them. Work done without permits creates legal liability, voids home insurance coverage, and can result in orders to demolish unpermitted work.