In 40 seconds
Hiring a RIBA-chartered architect for a full service in the UK typically costs around 7–15% of your build cost, so a £100,000 project usually means roughly £7,000–£15,000 in fees. Many homeowners only commission the early RIBA stages 0–4 — feasibility, concept design, planning and building-regulations drawings — and manage the build themselves, which often falls in the region of £1,500–£8,000+ for a typical extension depending on scope and location. Architects can also work to a fixed fee or an hourly rate, commonly around £50–£150 an hour, and plans-only packages often sit at roughly £1,200–£3,000. You do not always legally need an architect for a standard extension, but for complex, listed or design-led projects a chartered architect's experience often earns its place. The honest answer is always a range, because it depends on your project's size, complexity and location.
Most guidance on architect fees is published by practices selling their own services, so the numbers can be vague and the stages glossed over. The pages below give honest fee ranges, explain how percentage, fixed and hourly pricing actually work, set out when you do and don't need an architect, compare architects and architectural technologists fairly, and walk through the RIBA work stages — before you commission a single drawing.