Whether you are knocking down a load-bearing wall to create an open-plan kitchen, converting a loft, or building a home extension, you will need to hire a structural engineer. While architects design the aesthetic layout of a space, structural engineers perform the math and safety physics to ensure the building does not collapse under its own weight.
Their calculations specify the sizes of steel beams (RSJs), concrete foundations, and timber joists required. Local Building Control authorities will not sign off on structural work without an engineer's calculations. In this 2026 guide, we outline average structural engineer fees, calculations costs, and when you need one.
Average structural engineer fees in 2026
Most structural engineers charge a fixed fee for standard residential services (like steel calculations or a property survey). For custom consultations or complex builds, they charge an hourly or daily rate.
- Average Hourly Rate: £90 - £200 per hour (highly dependent on experience and location).
- Average Day Rate: £400 - £600 per day (for extensive site inspections and design drafting).
Here is a breakdown of estimated average structural engineering fees by project type (excluding VAT):
| Service / Calculations Type | Average Fee Range | Notes |
|---|---|---|
| Single RSJ Steel Beam Calculation | £250 - £500 | For standard load-bearing wall removal (up to 4m wide). |
| Multiple Steel Frame (Box Frame) Calculations | £600 - £1,200 | For wider knock-throughs or bi-fold door installations. |
| Standard Structural Inspection | £175 - £350 | Site visit to inspect cracks, subsidence, or load capacity. |
| Full Structural Property Report | £500 - £2,000 | Complete survey detailing defects and repair schedules. |
| Loft Conversion / Extension Design | £600 - £2,500 | Full calculation pack for foundations, floor joists, and roof steels. |
When do you need a structural engineer?
You must legally hire a structural engineer for any home renovation that alters the structural load of your house:
- Removing a load-bearing wall: To replace a brick wall with an open gap, you need a steel lintel or RSJ. The engineer calculates the size, weight, and padstone support required to bear the upper floors.
- Building an extension or loft conversion: Building control officers require structural calculations for the new foundations, retaining walls, floor structures, and roof joists.
- Installing heavy items: If you are adding a heavy marble bathtub, massive solar panels, or a roof terrace, you need an engineer to check if the joists can support the extra weight.
- Subsidence and structural issues: If your home shows deep, diagonal wall cracks or bowing walls, an engineer can diagnose structural shifting and specify underpinning or strapping remedies.
Understanding the structural engineering process
A typical engineer engagement proceeds as follows:
- Site Visit: The engineer visits your home to inspect access, take measurements of existing walls, and check the timber joist spans and foundation depths.
- Calculations & Drawings: Using specialized software, they draft structural calculation sheets and CAD drawings detailing beam sizes, steel connections, and padstone specifications.
- Building Control Submission: The builder submits these calculation sheets to the local Building Control officer (or an approved private inspector) for safety sign-off before construction starts.
Find qualified structural engineers on GetBuilder
Only hire engineers who are fully qualified. Look for members of the Institution of Structural Engineers (IStructE) or the Institution of Civil Engineers (ICE), and check that they hold valid Professional Indemnity Insurance.
- Post your design requirements: State your project scope (e.g. wall removal, loft design) for free on GetBuilder.
- Connect with local experts: Match with vetted structural engineers who hold valid credentials.
- Compare quotes: Ensure quotes outline site visits, calculation packs, and any revisions required by Building Control.
