Do I Need a Structural Engineer? 7 Signs You Do
Many homeowners aren't sure when they need a structural engineer — or what one actually does. Here's a clear guide to the seven most common situations where hiring a structural engineer is essential.
1. You're Converting Your Loft
A loft conversion is one of the most popular home improvements in London — and one that always requires a structural engineer.
Why? Because you're turning a roof space into a habitable room. That means:
- Steel beams to support the new floor and roof structure
- Floor joist design so the floor can carry the weight of furniture and people
- Staircase opening cut through the existing ceiling, supported by new steelwork
- Ridge beam or purlins if you're changing the roof shape (dormer, hip-to-gable)
Building Control won't approve a loft conversion without structural calculations from a qualified engineer.
Learn about our loft conversion service →
2. You're Building an Extension
Whether it's a rear extension, side return, or wraparound, an extension involves:
- Foundation design — the type and depth of your foundations depends on soil conditions and tree proximity
- Steel beams — where the extension meets the existing house, you usually need a steel beam to span the opening
- Structural connections — tying the new structure to the old safely
Even single-storey extensions under Permitted Development need Building Control — and Building Control needs structural calculations.
Extension structural engineering →
3. You Want to Remove a Wall
Not all walls are load-bearing — but if you remove the wrong one without support, the consequences can be severe: cracked ceilings, sagging floors, or worse.
A structural engineer will:
- Confirm whether the wall is load-bearing
- Design a steel beam (RSJ) to carry the load the wall was supporting
- Specify padstones and bearing details for your builder
- Produce Building Control calculations so the work gets signed off
Never rely on a builder's opinion about whether a wall is structural. Get an engineer's assessment.
4. You're Removing a Chimney Breast
Chimney breasts carry the weight of the chimney stack above. Remove one without proper support and you risk the chimney collapsing — potentially through the roof.
A structural engineer designs:
- Gallows brackets or a steel beam to support the remaining stack
- Building Control calculations proving the support is adequate
This is a legal requirement, not optional.
5. You've Spotted Cracks in Your Walls
Cracks aren't always serious — but some are signs of subsidence, foundation movement, or structural failure. You need a structural engineer (not a surveyor or builder) to:
- Assess the crack pattern — diagonal cracks near windows/doors often indicate structural movement
- Identify the cause — subsidence, settlement, thermal movement, or something else
- Recommend the solution — monitoring, underpinning, repairs, or simply cosmetic filling
- Produce a written report — essential for insurance claims or property sales
A structural survey gives you facts, not guesswork.
6. You're Buying a Property and Something Looks Wrong
If a homebuyer's survey flags structural concerns — cracks, damp, bowing walls, uneven floors — you need a structural engineer to investigate before completing the purchase.
A structural survey from SBS will tell you:
- What's actually wrong (if anything)
- How serious it is
- What it'll cost to fix
- Whether it should affect the purchase price
This can save you tens of thousands or give you the confidence to proceed.
7. You Had Work Done Without Building Control
This happens more often than you'd think. A previous owner (or even you) had work done — a wall removed, a loft converted, an extension built — but never got Building Control sign-off.
This becomes a problem when:
- You try to sell the property and the buyer's solicitor asks for proof
- You need a regularisation certificate from the council
- Your insurer asks about structural modifications
A structural engineer can retrospectively assess the work, produce the calculations, and help you get the certificate you need.
How Much Does a Structural Engineer Cost?
For most residential projects in London, structural engineer fees typically range from £400 to £3,000 depending on complexity. A single steel beam calculation might be £400–£800, while a full loft conversion package might be £800–£1,500.
At SBS, we offer fixed pricing with no hidden costs. Read our full cost guide →
How to Choose the Right Structural Engineer
Look for:
- Residential experience — a structural engineer who works on homes every day, not one who primarily does commercial work
- Local knowledge — familiarity with your local Building Control department and typical property types
- Fixed pricing — you should know the cost upfront
- Fast turnaround — your project shouldn't stall waiting for calculations
- Clear communication — you should understand what's being done and why
At SBS Structural and Architectural Design, we focus exclusively on residential structural engineering across London, Essex and Kent. We deliver within one week as standard, with an express 48-hour option.
Get a Free Consultation
Not sure if your project needs a structural engineer? Call us and we'll tell you for free.
- Phone: +44 7401 650 600
- Email: sbs.structures@gmail.com
- Office: 61 Cranbrook Road, Ilford, IG1 4PG
- Areas covered: London, Ilford, East London, Essex, Kent — see all locations
