House extension by Architects Grace Fletcher and Archer + Braun. Photo Rachel Ferriman.
If you're starting a home improvement project, one common question is: Do I need an architect for an extension?
There’s no legal requirement in the UK to use an architect, but your decision depends on factors like budget, project goals, and site conditions. This article outlines when you should consider an architect and when alternatives might be more suitable.
An architect offers a range of benefits that can help elevate your project, such as:
Exterior and interior of a high quality extension to a detached 1930s home by Dempsey + Gannon Architects, completed for £105,000. Photo by @KanoKane.
You may not need an architect if you have a clear vision for your project, are working with a tight budget, or prioritise adding space over design. An architect may also be unnecessary if you're planning a simple extension under permitted development rights, the site has no complex constraints like heritage issues or unusual boundaries, or you've already appointed another professional to handle the design.
If an architect doesn’t seem like the right fit for your project, consider these alternatives.
An Architectural Technologist is skilled in construction and serves as a practical option when design isn't the primary focus. They operate under a code of conduct and have Professional Indemnity Insurance (PII).
Design and Build Companies provide a one-stop shop for design and construction. While some employ architects or technologists, others may use less-qualified designers, so it's essential to check who will manage the design.
A Building Surveyor often offers basic architectural structural design services; they are RICS-qualified and adhere to industry standards.
Lastly, an Architectural Technician has some architectural training but isn’t regulated and may not carry PII.
READ: Architect Verses Architectural Designer: What's The Difference?
While some builders might offer design services, it’s unlikely they can produce the necessary drawings and documentation. Builders often work with one of the professionals mentioned above to handle the design aspects.
Choosing to let your builder lead the design may save on fees, but you risk losing control over the details and relying heavily on their interpretation.
A compact extension utilising redundant external space at a rural farmhouse by Emil Eve Architects. Photo by Mariell Lind Hansen.
If you’re confident in your design skills, you could produce your own drawings. However, without professional experience, this can lead to costly mistakes. You’ll also be responsible for planning, building regulations, and coordinating the design with others.
Regardless of whether you hire an architect, certain consents are essential for any extension project.
You must obtain Planning Permission before commencing construction, and if you're building under permitted development, applying for a Lawful Development Certificate (LDC) is advisable for added peace of mind.
Additionally, you will need to secure Building Regulations Approval, which can be done through either the Building Notice or Full Plans route.
If your extension is on or near a boundary, a Party Wall Agreement with your neighbour is necessary.
Finally, if you are building near a public sewer, you'll need a Build Over Agreement from your water company.
Rear and side return extension to a Victorian terrace house by VATRAA Architects, which required planning permission and party wall agreements in addition to the mandatory building regulations approval. Photo by Jim Stephenson.
In addition to architectural services, whether provided by an architect or another professional, you'll likely need a structural engineer to produce structural drawings and calculations for building control.
If a Party Wall Award is required, you may also need a Party Wall Surveyor.
For sustainable heating options, such as a heat pump, you'll need a qualified heating engineer to design, install, and commission the system.
For high-value or complex extension projects, it may be advisable to enlist a quantity surveyor for expert cost advice.
If your budget is tight or you’re confident in handling parts of the project, consider hiring an architect only for specific areas. Many architects offer tailored services, such as planning-only services to help you with the overall layout and appearance or building regulations services to secure the necessary approvals.
This way, you can benefit from professional input while controlling costs.
Architects quote fees as a percentage, lump sum (fixed fee), or time charge, depending on the project stage and clarity of your brief. Full services typically cost around 12% of build costs. Planning fees range from 3-5%, while planning and building regulations approval costs 7-9%.
An architectural technologist or surveyor is generally 10-20% cheaper for drawings-only services.
READ: How Much Does an Architect Cost In The UK?
Extension interior by Emil Eve Architects. Residential architect can also provide interior design services for a fully cohesive final project. Photo by Mariell Lind Hansen.
The decision depends on the complexity of your project and how confident you are in managing the design and build process. Hiring an architect ensures a well-designed, and compliant extension. However, for simpler projects or tighter budgets, alternative professionals may suffice.
The information provided in this article is intended for general guidance and educational purposes only. For specific expert advice on your project, consult a skilled residential architect featured on Designs in Detail.
About the Author
Aron Coates is an architect with over two decades of experience, working on projects ranging from historic building restoration to contemporary home design.
