What is a structural engineer, and what do they do?

If you’ve ever wondered why buildings don’t collapse under their own weight, give structural engineers the credit. A structural engineer plays a key role when you’re building an extension or planning a major home renovation. They can also provide vital support in property-related legal proceedings when you need an expert on your side.

As the name suggests, they specialise in the structure of buildings, assessing the strength and durability of a building’s structure during the construction process. Structural engineers are usually charged with rating a building’s safety, and making calculations for the design when a new building or renovation project is in the offing.

Structural engineers often specialise in specific structure types. For home renovations or inspections, you’ll need one with residential building experience.

When do I need a structural engineer?

There are numerous situations where a structural engineer can help, or where their services are an absolute requirement for success:

01 When you’re doing renovations

If plans for an extension or major renovation could affect the stability of a building, it’s safe to assume you’ll need the services of a structural engineer to ensure everything is safe and sound. They’ll provide you with calculations and drawings your architect and building contractor will use to execute the build.

If building regulations require it, the calculations and drawings might also need to be filed with the local authority and to planning officials if the work is extensive enough to require planning permission. That can include loft conversions, building an extension, and fitting solar panels — to name just a few.

As a general rule, anything that fundamentally alters the structure of a property requires approval from the local building control officer, and approval will be based on the technical information only a structural engineer can provide.

If you’re unsure whether you need a structural engineer or not, ask your, architect or contractor.

Most large-scale projects need an architect to oversee the design, use of space, and energy efficiency of a home improvement project; and a structural engineer to ensure the renovated building is still structurally sound.

02 When you need a structural inspection

If your property shows signs of structural damage like cracking walls, sagging ceilings, or subsidence, you may need an inspection by a structural engineer. They’ll assess the damage, identifying possible causes and recommending how to fix it.

Sometimes a property survey can prompt an inspection. If the surveyor identifies structural issues, they’ll likely advise you to have a structural engineer conduct a more detailed investigation.

03 When you need an expert witness

If you find yourself in a legal conflict with a neighbour over a structural matter related to your property, a structural engineer can act as an advocate.

They’ll provide the court with an unbiased opinion and deliver an independent report on the nature of the problem and what caused it. The report will also include recommendations and options for addressing the issue.

What does a structural engineer cost?

The fees charged by structural engineers depend on three factors:

• The type of project
• The size of the project
• The location of the project. Of course, this mostly means ‘London’, where higher costs are the norm.

For large projects like adding an extension, fees can range from £750+VAT to £1500+VAT or even upwards. The engineer’s quote will include a site visit, delivery of all necessary calculations, and drawings to guide the work of the architect and building contractor.

Other considerations

When you engage a structural engineer, it’s essential to clarify what’s included in their quote, and what isn’t.  Ask for a detailed breakdown of costs with a list of inclusions and exclusions, noting additional fees and any hard costs or expenses.

If you need the structural engineer to produce technical drawings as part of a submission to the local authority for approval/permission, see if site inspections are included. Any changes to the design or specification of the project will likely incur additional charges, especially if the engineer’s original calculations or drawings need to be updated as a result.

Bear in mind: any changes to your home that alter its appearance or encroach on the neighbouring properties will typically require a level of planning permission from the local council and/ or party wall agreement in order for it to proceed.