Structural Engineer vs Architect: Do You Need Both?
One of the most common questions London homeowners ask before starting a project is: do I need a structural engineer, an architect, or both?
The answer depends on your project — but for many residential jobs, you may only need a structural engineer. Here's the straightforward breakdown.
What Does a Structural Engineer Do?
A structural engineer ensures your building is safe and structurally sound. They:
- Design steel beams to support openings where walls are removed
- Calculate load paths so weight transfers safely through beams, walls, and foundations
- Design foundations for extensions and new structures
- Produce structural drawings and calculations that your builder works from
- Satisfy Building Control — the council needs these calculations to approve your work
At SBS, structural calculations and drawings are our core service. Every project we deliver is Building Control ready.
What Does an Architect Do?
An architect focuses on the design and layout of your project. They:
- Create the overall design concept and floor plans
- Handle planning applications (when needed)
- Produce architectural drawings showing the look of the finished project
- Manage the aesthetic: materials, finishes, spatial layout
An architect's drawings show what it will look like. A structural engineer's drawings show how it will stand up.
When You Need Both
You typically need both an architect and structural engineer for:
- Large extensions that need planning permission — the architect handles the planning application, the engineer designs the structure
- Major renovations that change the layout significantly
- New builds — the architect designs the building, the engineer makes sure it won't fall down
When a Structural Engineer Is Enough
For many common residential projects, you don't need an architect — just a structural engineer:
Loft conversions (most types)
If you're doing a rear dormer under Permitted Development, you don't need planning permission and therefore don't need an architect for a planning application. Your structural engineer designs the steelwork, floor joists, and staircase opening — everything your builder needs. Loft conversion service →
Wall removal / steel beams
Knocking through a wall is a structural job, not a design job. Your structural engineer calculates the beam size, specifies padstones, and produces the Building Control submission. No architect needed. Steel beam calculations →
Chimney breast removal
Same principle — this is structural support work. A structural engineer designs the gallows brackets or steel beam, and your builder installs it. Chimney breast removal →
Structural surveys
Investigating cracks, subsidence, or structural defects is purely engineering work. An architect can't assess whether your foundations are failing. Structural surveys →
Retrospective Building Control
If you need to regularise work done without approval, you need a structural engineer to prove the existing structure is adequate — not an architect. Retrospective applications →
Can a Company Do Both?
Yes. At SBS Structural and Architectural Design, we provide both structural engineering and architectural design services. For projects that need both, working with one company means:
- One point of contact instead of two
- Coordinated drawings — the structural design matches the architectural layout
- Faster turnaround — no waiting for one to send drawings to the other
- Lower total cost — a combined package is usually cheaper than hiring two separate firms
Cost Comparison
| Service | Typical Cost | |---|---| | Structural engineer only (e.g. beam calc) | £400 – £800 | | Structural engineer (full loft conversion) | £800 – £1,500 | | Architect only (planning drawings) | £1,500 – £4,000+ | | Both together (full design + structure) | £2,000 – £5,000+ |
For projects where you only need structural calculations, you can save significantly by skipping the architect. See our full pricing guide →
How to Decide
Ask yourself:
- Does my project need planning permission? If yes, you likely need an architect (or at least an architectural designer) for the application.
- Am I just removing a wall, converting a loft, or fixing a structural issue? If yes, a structural engineer alone is usually sufficient.
- Do I want someone to design the overall look and layout? That's an architect's role.
- Do I need Building Control calculations? That's a structural engineer — always.
Get Started
At SBS, we can advise you on exactly what you need — and we won't push services you don't require. If you only need structural calculations, that's what we'll quote.
- Request a free consultation →
- Call us: 07401 650600
- Turnaround: 5–7 working days (express 48-hour available)
- Coverage: London, Essex & Kent →
