Finding an Architect for Your Extension

The drawings your architect produces will determine what your extension looks like, what it costs to build, and whether building control approves it. Get the wrong drawings, and your builder prices the wrong job. Get incomplete drawings, and your structural engineer can't size the steels. Your planning application gets bounced back if information is missing. Every professional and tradesperson downstream depends on what your architect puts on paper.

That makes this appointment the most consequential decision in the entire planning phase. Not the most expensive. The most consequential.

Do You Actually Need an Architect?

Legally, no. There's no law requiring you to hire an architect (or anyone else) to draw up your extension plans. You could sketch them on the back of an envelope and submit them to the council yourself.

In practice, yes. You need someone who can produce accurate scaled drawings and prepare building control documents covering thermal calculations and structural coordination. For anything more complex than a simple conservatory replacement, that means a qualified professional.

But "architect" is a legally protected title in the UK. Only someone registered with the Architects Registration Board (ARB) can call themselves an architect, and that requires seven years of training. The person who draws your extension might not be an architect at all. They might be an architectural technologist, a building designer, or a draughtsperson. That's not necessarily a problem, but you need to know what you're getting.

Three Types of Professional

For a standard single-storey rear extension, an architectural technologist is often the best value. They tend to have stronger technical knowledge of construction details and building regulations than a design-focused architect, and their fees are typically lower (compare the ranges in the table above). They can handle the full pipeline: outline drawings, detailed plans, planning submission, building control documents, and structural coordination.

Where you genuinely need a full architect is if your project involves design complexity (unusual geometry or a listed building), if you want someone with strong aesthetic vision, or if your extension needs to persuade a planning committee.