The short answer
UK architects bill three main ways. A fixed fee is an agreed lump sum for a defined scope — it gives the clearest budget and suits well-defined projects. A percentage of construction cost (typically around 7%–15% for a full service) scales automatically with the project and suits larger or full-service work, but the final figure isn't fixed until the build cost is. An hourly rate (typically £50–£150) is the most flexible and best for advice, feasibility and small open-ended tasks, but leaves the total uncertain. None is universally 'best' — the right choice depends on how defined your scope is and how much cost certainty you want. A common, sensible pattern is hourly for early feasibility, a fixed fee for design and planning, and a percentage for the construction stage.
The same project can be priced three different ways, and which model you pick affects both your cost certainty and how risk is shared. Here's a plain comparison of all three.
The three models at a glance
- Fixed feeLump sum, known total
- Percentage~7%–15% of build cost
- Hourly~£50–£150/hr
- Most certaintyFixed fee
- Most flexibleHourly
How each model works
- Fixed fee: you agree a single lump sum for a clearly defined scope of work. The architect carries the risk of it taking longer than expected, so the scope has to be tight — change the brief and the fee changes. Best when you know exactly what you want.
- Percentage of construction cost: the fee is set as a percentage of the build cost (not the total project cost), commonly around 7%–15% for a full service. It scales automatically — a bigger build means a bigger fee — which keeps it proportionate but means the final figure isn't pinned down until the build cost is.
- Hourly rate: you pay for the time spent, typically £50–£150 per hour depending on seniority and location. Flexible and fair for open-ended work, but the total is unknown until the work's done, so it's usually reserved for advice and small tasks or capped with a not-to-exceed limit.
| Model | Typical UK figure | Cost certainty | Best for |
|---|---|---|---|
| Fixed fee | Agreed lump sum | High | Defined scope |
| Percentage | ~7%–15% of build | Medium | Full service, larger jobs |
| Hourly | ~£50–£150/hr | Low | Advice, small tasks |
Indicative comparison of UK architect billing models, 2025–2026. Source: RIBA fee guidance.
Pros and cons in practice
Each model shifts risk and certainty differently:
- Fixed fee — pro: you know the total up front and can budget precisely. Con: any change to the brief triggers a variation and extra cost, and the architect may price in a contingency for the unknowns.
- Percentage — pro: proportionate and simple on a full-service job; the fee tracks the project's scale. Con: the fee rises if the build cost rises, and on a small project the percentage needed to make it worthwhile can feel high.
- Hourly — pro: you only pay for the time used, which is efficient for short or uncertain tasks. Con: no ceiling unless you agree one, so a long project billed hourly can become unpredictable.
For most homeowners, cost certainty is the priority, which is why a fixed fee is popular for the defined stages. But on larger or open-ended projects, a percentage or hourly arrangement can be fairer to both sides.
Mixing models — the common real-world approach
In practice many appointments blend the models stage by stage, which often gives the best balance. A typical pattern:
- Hourly for the early feasibility, where the scope genuinely isn't known yet and you're testing whether the project is viable.
- Fixed fee for design and the planning application, where the scope is now defined and you want a known budget.
- Fixed fee or percentage for the building-regulations drawings and the construction stage, where the workload becomes more predictable or tracks the build.
Whatever the structure, insist on a written fee proposal that states the model for each stage, what's included, and whether VAT and disbursements are extra. The best protection against fee surprises isn't picking the 'lowest-cost' model — it's making sure the scope behind the fee is clearly defined, so you and the architect are agreeing on the same piece of work. A clear scope makes a fixed fee genuinely fixed, a percentage genuinely proportionate, and an hourly rate genuinely controllable.
Matching the model to your project
If you're unsure which model to ask for, the project type itself usually points to a sensible default:
- A well-defined, smaller project — a single-storey extension or a loft to a clear brief — usually suits a fixed fee, because the scope is known and you want a firm budget.
- A larger or full-service project — a new build, a major remodel, or anything where you want the architect right through construction — often works on a percentage, which keeps the fee proportionate as the project grows.
- An open-ended or exploratory task — early feasibility, planning advice, or a one-off review — fits an hourly arrangement, ideally with a cap.
These are starting points, not rules. A good architect will recommend the model they think fits your job and explain why, and you can ask for an alternative if it suits you better — for example a fixed fee for cost certainty even on a larger project. What matters most is not which label the fee carries but that the scope behind it is clear and written down. Two architects quoting different models can be offering genuinely comparable value; the way to compare them is to look past the model to what each fee actually buys, stage by stage, and whether VAT and other costs are included. Get that clarity and any of the three models can work well; skip it and even the 'lowest-cost-looking' model can cost more than expected once the gaps in scope surface during the project.
Frequently asked questions
Which architect fee model gives the most cost certainty?
A fixed fee gives the most certainty because you agree a single lump sum up front for a defined scope. The trade-off is that any change to the brief triggers an extra cost, so the scope has to be clear from the start.
When is a percentage fee better than a fixed fee?
A percentage suits full-service or larger projects where the workload tracks the build cost, and where a fixed price would carry a risk premium. It scales automatically, but the final figure isn't known until the construction cost is.
Is hourly billing risky for a whole project?
It can be, because there's no ceiling unless you agree one. Hourly suits advice and small, open-ended tasks. For a full project, most people prefer a fixed fee or percentage, or an hourly arrangement with an agreed not-to-exceed cap.
Sources & further reading
- RIBA — how much does an architect cost
- HomeOwners Alliance — architect fees explained
- Checkatrade — architect fees guide
Figures on this page are typical UK ranges drawn from published sources and depend on your specific project. They are guidance, not a quotation.