Do I need a structural engineer for my remodel?
PUBLISHED SEPTEMBER 8, 2026 · REVIEWED BY MILAD KAZEMI
You need a structural engineer whenever the permit set includes new or altered structure — a new house, an addition, opening up or removing a bearing wall, a new or underpinned foundation, a seismic retrofit, or a retaining wall above the exempt height. California building departments will not issue a permit for structural work without drawings and calculations stamped by a licensed engineer or architect.
What counts as structural work
The line is not how big the project is. It is whether the load path changes.
A kitchen refit that keeps every wall where it is has no structural scope. The same kitchen with the wall to the dining room removed does — because something now has to carry what that wall was carrying, and something has to resist the lateral load that wall was contributing.
Work that almost always needs an engineer:
- A new house, or an addition of any size
- Removing or widening an opening in a bearing wall
- A new foundation, or underpinning an existing one
- Adding a storey, or a roof deck
- A retaining wall above the height your jurisdiction exempts
- A seismic retrofit — soft-storey, cripple wall, or chimney
Work that usually does not:
- Finishes, cabinetry, fixtures
- Replacing windows in existing openings at the same size
- Re-roofing with a comparable material weight
The middle cases are where people get caught. Replacing a window with a wider one is structural. Converting a garage is structural, because the header over the old garage door and the slab both need looking at. Cutting a skylight into a rafter roof is structural.
What the engineer actually produces
Two things go to the building department, and both carry the engineer’s stamp and wet signature.
Structural drawings. A foundation plan, framing plans for each level and the roof, schedules for beams, columns, footings and hold-downs, and the details that show how connections are made. These sit alongside the architectural sheets in the same set.
A calculation package. The loads assumed, the seismic and wind parameters for your site, and the arithmetic that sizes every member. A plan checker reads this to confirm the drawings are justified.
On many projects there is a third piece: structural observation during construction, where the engineer visits at defined stages — usually foundation and framing — and signs that what was built matches what was designed.
How to tell before you hire anyone
Ask two questions of whoever you are considering.
“Who stamps the structural drawings on this project?” If the answer is a third party, you are hiring two firms, and the coordination between them is now your risk. That is not necessarily wrong, but you should know it before you sign, not in month four.
“Is responding to the plan-check corrections in your fee?” Structural corrections are normal. What is not normal is discovering they are billed hourly after the correction letter arrives.
What it changes about the design
An engineer brought in at the end can only work with the plan they are handed. That is how a great open-plan living room acquires a column in the middle of it.
In seismic California the lateral system — the shear walls and frames that resist earthquake load — decides where solid wall has to exist. Deciding that while the plan is still moving costs nothing. Deciding it after the plan is fixed costs either a column, a steel moment frame, or a redesign.
This is the reason we do the structural work in the same office as the drawings. It is not a convenience argument. It is that the constraint gets designed with rather than designed around.
Sources
Rules change. Confirm anything you are relying on against the agency directly.
Questions we get asked
- Can a designer or draftsperson do the structural drawings?
- Not the stamped ones. In California, structural design for a permit must be prepared under the responsible charge of a licensed civil or structural engineer, or a licensed architect within the scope of their practice. A designer can prepare the architectural drawings, but the structural sheets and calculations need a stamp.
- What does the structural engineer charge for?
- The design work and the calculation package, plus responses to the plan checker's structural corrections and, on many projects, structural observation during framing. Ask whether corrections and observation are included in the fee or billed on top — that is where quotes usually differ.
- Can I skip the engineer if I use an off-the-shelf plan?
- Rarely. A stock plan still has to be engineered for your soil, your seismic design category and your local amendments, all of which vary by parcel. Some cities offer pre-approved ADU plans that come pre-engineered; outside those programmes, expect to engineer the plan for the site.
Send us the address.
Tell us the property and roughly what you want to build. We come back with what the zoning allows, the likely permit path, and a fixed fee for the first phase.