Do I Need a Structural Engineer for My Project?
A useful rule: if you are changing how loads travel through the building, or the jurisdiction asks for calculations, you need one. Here is how to tell before you spend anything.
You almost certainly need one
These jobs change the load path, and nearly every jurisdiction requires sealed calculations for them.
- ✓ Removing or altering a load-bearing wall
- ✓ Adding a second storey or building over an existing structure
- ✓ Cutting a new large opening in an exterior wall
- ✓ Any addition that ties into the existing foundation
- ✓ Retaining walls above the height your jurisdiction sets, commonly four feet
- ✓ Decks attached to a dwelling above a set height
- ✓ Foundation repair, underpinning or slab remediation
- ✓ Most commercial and all industrial structural work
You probably do not
These generally stay within the prescriptive tables of the residential code, which means a builder can work from published spans without engineering.
- ✓ Replacing windows in the same opening size
- ✓ Non-structural interior finishes, cabinets or flooring
- ✓ Like-for-like roof covering replacement
- ✓ Small freestanding sheds below the permit threshold
The grey area
Plenty of projects sit in between, and the answer comes down to your specific jurisdiction. If the building department says the design is outside prescriptive limits, or asks for calculations at intake, engineering is required regardless of how small the job feels. It is cheaper to ask first than to be told at plan review.
Engineer or architect?
Broadly: an architect deals with layout, code compliance, egress and how the building is used; a structural engineer deals with whether it stands up. Many permits need both. Some jurisdictions accept either seal on residential work, and some are specific. We confirm which applies to your address before starting.
Frequently asked questions
How do I know if a wall is load-bearing?
If it runs perpendicular to the floor joists above, sits above a beam or foundation wall, or is stacked with a wall on the floor above, treat it as load-bearing until an engineer confirms otherwise. Never assume from appearance alone.
Can my contractor decide instead?
An experienced contractor can often tell you whether engineering will be required, and that advice is worth having. But the jurisdiction will still want sealed calculations from a licensed engineer where the code demands them; a contractor cannot substitute for that.
What does the engineer actually produce?
Typically a framing plan, member sizes, connection details and a stamped calculation package showing the load path. That set is what the plan checker reviews and what the builder builds from.