How to Choose the Right Architect for Your Extension

Choosing the right design professional is one of the most important decisions you'll make on your extension project. A good architect doesn't just draw pretty pictures — they solve problems, navigate regulations, manage budgets, and ultimately determine whether your project delivers real value or becomes an expensive headache. But the market is confusing: architects, architectural technologists, architectural designers — what's the difference, and who do you actually need?

Architect vs architectural technologist vs designer

A chartered architect is registered with the Architects Registration Board (ARB) and is typically a member of RIBA (Royal Institute of British Architects). They've completed a minimum of seven years of education and training. The title "architect" is legally protected in the UK. An architectural technologist (often a member of CIAT) specialises in the technical aspects of building design — they're experts in construction detailing, building regulations, and producing the technical drawings that builders work from. An architectural designer has no specific protected title or required qualification, though many are highly skilled. For a straightforward home extension, any of these professionals can do an excellent job. The key is their experience with residential projects similar to yours, not their title.

Fee structures: percentage vs fixed fee

Architects typically charge either a percentage of the construction cost (usually 8–15% for residential projects) or a fixed fee agreed upfront. A percentage fee aligns the architect's reward with the quality of the project but can feel open-ended if the build cost increases. A fixed fee gives you certainty but may lead to variations if the scope changes. For a typical London home extension, architectural fees range from £3,000 to £8,000 for design through to planning, and £6,000 to £15,000 for a full service including technical drawings, building regulations, and tender support. Some practices offer staged payments aligned to RIBA work stages, which can help with cash flow.

What to look for in a portfolio

When reviewing an architect's work, look for projects that are similar in scale, type, and budget to yours. If you're extending a Victorian terrace in south London, an architect who specialises in high-end new-build country houses may not be the best fit — however talented they are. Look at before-and-after comparisons to understand how they solve spatial problems. Pay attention to how they handle the junction between old and new. Check whether their completed projects look like the CGIs — the gap between render and reality tells you a lot about their ability to deliver.

Questions to ask before appointing

• How many similar projects have you completed in the last two years?
• Can I visit a completed project or speak to a previous client?
• What exactly is included in your fee, and what will be charged as an extra?
• Who will actually be doing the design work — you, or a junior member of your team?
• How do you handle planning applications and building regulations?
• Do you provide support during the construction phase?
• What is your typical turnaround time for design drawings?
• How do you communicate during the project — email, project management software, regular meetings?

RIBA work stages explained simply

RIBA (Royal Institute of British Architects) defines a series of work stages that provide a framework for the design process. For a home extension, the most relevant stages are: Stage 0 (Strategic Definition) — understanding what you need; Stage 1 (Preparation and Briefing) — site survey, brief development; Stage 2 (Concept Design) — initial design options and layouts; Stage 3 (Spatial Coordination) — developed design with technical input from engineers; Stage 4 (Technical Design) — detailed construction drawings and specifications. Not every project follows every stage rigidly, but understanding this framework helps you know what to expect and when.

Red flags to watch for

• No written fee proposal or appointment letter — professional practices always formalise the arrangement.
• No professional indemnity insurance — this protects you if the architect makes an error in their design.
• Reluctance to provide references from previous clients.
• Promises that seem too good to be true — "You'll definitely get planning" or "This will only cost £30k to build."
• Poor communication at the outset — if they're slow to respond before you've appointed them, it won't improve afterwards.
• No clear fee structure or scope of service — ambiguity leads to disputes.