Considering a home extension to expand your living space?

While the idea of having more room is undoubtedly appealing, it’s essential to recognise the crucial role that a structural engineer plays in such undertakings. These professionals are not merely technical experts armed with blueprints; instead, they serve as indispensable contributors to ensuring the success of your project and safeguarding it from potential pitfalls.

This article aims to shed light on the significance of engaging a structural engineer in the context of home extensions.

By delving into the nuanced complexities and considerations involved, we seek to provide a comprehensive understanding of why their expertise is paramount in achieving the desired expansion and the structural integrity and safety of your dwelling.

Interested In A Career In Structural Engineering?

Due to our continued growth, we regularly seek new professionals to join our team. We actively invest in our people and their development, supporting their passion and expertise in architecture and structural design. View our job listings to find out more! 


Many people may believe they only need to appoint an architect when considering extending their home. This is not the case.

At some point throughout the planning and building of your extension, you will be required to submit calculations from a structural engineer to ensure that you can get your extension through both the building control and the warrant stage.

So why is this?

Once you appoint a builder for your extension, they will require a set of drawings to work from. These drawings will provide the builder with precise measurements and instructions on how the build will come together. Every project in Scotland and England requires this.

In Scotland, your structural engineer will also need to SER certify your extension. This may seem like an extra hurdle to jump, but the presence of an SER certifier will drastically decrease the time needed for your building to pass inspection.

If you involve a structural engineer at the start of your project, this can also help you save on the overall cost of your build and help make the process easy for your builder by considering buildability & reviewing the architectural proposals.


Given that you will require a structural engineer, it is best to get one involved in the project as early as possible in the design of your extension. Leaving it late could result in unnecessary delays, additional costs, and changes to your architectural plans.

Bringing in a structural engineer early means they can advise on possible cost savings and ensure the construction phase will be as efficient as possible for the builder.

ACS does offer a retrospective service for historic works undertaken without a building warrant or engineering design. This normally comes to light when Clients are in the closing stages of selling a property and can add unnecessary stress by jeopardising the sale.

Retrospective design is always more costly, as as-built construction needs to be confirmed by inspection (which may require intrusive investigation to expose structure) and you are not always guaranteed that what has been built will satisfy building standards.

Structural Integrity Issues

Without a professional assessment, there is a heightened risk of compromising the structural integrity of your existing property. An extension imposes additional loads, and proper analysis is necessary for the original structure to support the new weight adequately. This can lead to issues such as subsidence, sagging floors, or even structural failure.

Alterations to the existing structure may cause excessive movement if not designed appropriately and can also increase loading on existing foundations by altering the way loading is transferred through the building.

Safety Concerns

A lack of expert oversight may result in safety hazards within the extension. This could include inadequate support for walls or floors, poorly designed foundations, or other structural deficiencies that pose risks to the construction works and future occupants.

Legal Challenges 

Please comply with local building codes and regulations to avoid legal complications. Without a structural engineer’s guidance, you may unintentionally violate zoning laws or fail to obtain necessary permits, leading to fines, delays, or even the need to dismantle and redo the extension.

Insurance Implications

Homeowners’ insurance policies often require compliance with building codes. Suppose your extension is not up to code due to the absence of a structural engineer’s input. In that case, it may affect your insurance coverage, exposing you to potential financial losses in the event of damage or accidents.

Resale Value

A poorly executed extension can negatively impact the resale value of your property. Prospective buyers will likely be deterred by structural issues, leading to difficulties in selling the property or potential decreases in its market value.


The answer to this question varies due to many factors related to your build.

The size and complexity of your extension can be contributing factors. Typically, you should factor in around 1-3% of your overall project cost. Appointing a structural engineer who engages with the clients and is responsive to their needs can also help save money, as anything that needs action will be done efficiently. At Allan Corfield Structures, we pride ourselves on building relationships with the clients and understanding what they want to achieve. 



A structural engineer plays a crucial role in ensuring the safety, reliability, and longevity of your building. Our primary focus is to design a structure that is not only stable but also comfortable for your needs. From foundations to floors, walls to roofs, we handle the entire design process, providing comprehensive structural plans and details for your builder.

Some of the services that would be included when appointing a structural engineer from Allan Corfield Structures are:

Initial Site Evaluation Service

  • Specification and arrangement of Site Investigation
  • Assessment of foundation type
  • Visual inspection of the existing building and any available archive information
  • Review of surface & foul drainage solutions (if required)
  • Porosity test (if required)
  • Existing Building Survey (If there is one)

Structural Design & Analysis Of All Main Structural elements

  • Foundations
  • Ground floor slabs
  • Lintels
  • Structural ties and fixings
  • Floors, walls and roofs – SIPS, Timber frame, ICF or traditional
  • Additional structural framing (timber or steel) required to transfer loadings down to the foundations
  • Secondary support for any proposed glazing systems
  • Off-grid/SUDS drainage design
  • Structural Engineers Registration Scheme (SER) Certification of all structural elements in support of the Building Warrant application. This will include a review of third-party design elements such as stairs, balustrades and glazing
  • Ad hoc on-site assistance & reporting (recommended at the beginning of the project, on opening up of existing structure and prior to enclosing new structure).
  • Specialist kit contractors’ line & point load design

We’re here to answer any questions and guide you through the design process, whether you’re planning an extension or making alterations to your existing house. Our services also include on-site inspections and reports to ensure your home meets the necessary standards.

Additionally, we offer valuable advice on cost-saving measures, suggesting changes that align with your plans without compromising quality. Our goal is to optimise your project for efficiency and affordability.


Engaging our experienced team of Structural Engineers for your project is essential for its smooth, safe, and professionally managed progression. Their expertise ensures optimal project flow, safety, and a high level of professional know-how.

If you are considering extending your home and wish to discuss your options, follow the link below to arrange a consultation with our highly skilled team.

Do you have any question regarding your project?

Contact us, and we will help you move on with your Self Build dream!