Architect Fees London 2026: What You'll Actually Pay
Architect fees are one of the least transparent costs in a London extension project. This guide breaks down exactly what architects charge, what you get for your money, and how to avoid overpaying.
Quick Answer
London architects charge 8-15% of build cost (average 10-12%) or £3,000-15,000+ as a fixed fee depending on project complexity. A typical rear extension costs £4,000-8,000 in architect fees. Hourly rates range from £80-200/hour for ad-hoc work.
8-15%
% of Build Cost
£3k-£15k+
Fixed Fee Range
£80-£200
Hourly Rate
Check your specific property constraints
Free Property CheckWhat Architect Fees Actually Cover
When homeowners hear architect fees, they often think they are just paying for drawings. In reality, a full architectural service covers far more than that. Understanding the scope helps you compare quotes fairly and ensures you are not paying for services you do not need.
A full architectural service typically includes:
- Site survey and measured survey: Visiting your property, measuring the existing building, and creating accurate plans
- Design development: Creating initial concept designs, refining them based on your feedback, producing final design proposals
- Planning application: Preparing planning drawings, writing design and access statements, submitting and managing the application
- Building regulations drawings: Technical drawings showing construction details, structural layouts, insulation, drainage
- Tender package: Preparing documents for builders to quote from, helping you compare builder quotes
- Site visits during construction: Periodic inspections to ensure the builder is following the design and addressing any issues
Fee Structures: Percentage vs Fixed vs Hourly
London architects use three main fee structures. Each has advantages and risks, and the best choice depends on how well-defined your project is at the outset.
Percentage of Build Cost
The most traditional approach. The architect charges 8-15% of the final construction cost, with the London average sitting at 10-12%. For a £100,000 extension build, that means £10,000-12,000 in architect fees.
- Pro: Fee scales with project complexity, so simple projects cost less
- Con: No incentive for the architect to control build costs, as higher costs mean higher fees
- Con: Final fee unknown until the build is complete, making budgeting difficult
Fixed Fee
A set price agreed upfront for a defined scope of work. Fixed fees for London extension projects typically range from £3,000 to £15,000 or more depending on scope. This is increasingly popular with homeowners who want cost certainty.
- Pro: Budget certainty from day one, no surprises
- Pro: Architect is incentivised to work efficiently
- Con: Additional revisions or scope changes may incur extra charges
Hourly Rate
Less common for full projects but useful for ad-hoc consultations, planning advice, or design reviews. London architects charge £80-200 per hour, with chartered architects (RIBA Part 3) at the higher end.
Watch out: Hourly rate engagements can escalate quickly. A 2-hour initial consultation at £150/hour seems reasonable, but if design revisions extend to 40+ hours, you could end up paying £6,000 or more without realising. Always agree a cap or switch to a fixed fee once the scope is clear.
Cost Breakdown by RIBA Stage
The RIBA Plan of Work divides architectural services into stages (0-7). Most homeowners only need stages 1-4, with stage 5 (construction monitoring) as an optional extra. Here is what each stage covers and its typical cost for a London residential extension.
| RIBA Stage | What It Covers | Typical Cost |
|---|---|---|
| Stage 0-1: Briefing | Initial consultation, site appraisal, feasibility study, brief development | £500-£1,500 |
| Stage 2: Concept Design | Measured survey, initial design options, outline planning strategy | £1,500-£3,500 |
| Stage 3: Developed Design | Detailed design, planning drawings, planning application submission | £2,000-£4,500 |
| Stage 4: Technical Design | Building regs drawings, construction details, specification, tender documents | £2,500-£5,000 |
| Stage 5: Construction | Site visits, contractor queries, quality monitoring, practical completion | £1,500-£4,000 |
| Full Service (Stages 0-5) | Complete architectural service from brief to completion | £8,000-£18,000 |
Most common approach: The majority of London homeowners commission stages 1-4 (design through to building regs drawings) and manage the build themselves or with a project manager. This costs £5,000-12,000 and accounts for roughly 70% of the total architectural fee.
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What Affects the Price
Not all extension projects cost the same in architect fees. Several factors push the price up or down.
- Project complexity: A simple rear extension with standard details costs less to design than a wrap-around extension with structural glazing, split levels, and basement works
- Conservation area: Projects in conservation areas require additional design sensitivity, heritage impact assessments, and more detailed planning submissions. Expect 20-30% higher fees
- Listed building: Listed building consent is a separate application with stricter requirements. Architect fees increase 30-50% for listed properties
- Architect experience: A recently qualified architect may charge £3,000-5,000 for the same scope that a 20-year veteran charges £8,000-12,000 for. More experience typically means fewer issues on site
- Location within London: Practices in Zones 1-2 tend to charge more than those in outer boroughs, though many architects work across all London zones
Typical Architect Fees by Project Type
| Project Type | Build Cost Range | Architect Fee (Stages 1-4) |
|---|---|---|
| Single-storey rear extension | £45,000-£90,000 | £4,000-£8,000 |
| Loft conversion | £50,000-£80,000 | £3,500-£7,000 |
| Two-storey extension | £80,000-£180,000 | £7,000-£15,000 |
| Basement extension | £200,000-£500,000+ | £15,000-£35,000 |
| Full house renovation | £150,000-£400,000 | £12,000-£30,000 |
Want to compare architect costs?
Get an instant estimate for your projectHow to Compare Architect Quotes
Getting three quotes is standard practice, but comparing them fairly requires looking beyond the headline price. Two quotes that appear similar can cover very different scopes of work.
Checklist for comparing architect quotes:
- Does the quote specify which RIBA stages are included?
- How many design revisions are included before extras are charged?
- Is the measured survey included or an extra cost?
- Are structural engineer coordination fees included?
- How many site visits during construction are included?
- What happens if planning is refused and needs redesign?
- Are planning application fees (£206 for householder) included in the quote?
Red Flags When Hiring an Architect
Not all architects operate to the same professional standards. Watch out for these warning signs before you commit.
- No Professional Indemnity (PI) insurance: Any architect working on your project should carry PI insurance. Ask for proof. Without it, you have no recourse if their design causes problems
- Vague scope of services: If the proposal does not clearly state what is included and excluded, you are likely to face unexpected additional charges later
- No written contract: Professional architects use a formal appointment document (RIBA Domestic or similar). Working without a contract leaves both parties exposed
- Requesting full payment upfront: Stage payments linked to deliverables are standard practice. An architect asking for 100% upfront is a major red flag
- Not ARB registered: The title "architect" is legally protected in the UK. Only ARB-registered professionals can use it. Check the ARB register at architects-register.org.uk
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How Mayfair Studio Compares
Traditional architectural services work well but come with high costs and long timelines. Mayfair Studio offers an alternative approach with fixed-price design packages that cover the most common extension types.
| Factor | Traditional Architect | Mayfair Studio |
|---|---|---|
| Price (rear extension) | £4,000-£8,000 | £1,295-£1,795 |
| Pricing model | % of build cost or hourly | Fixed price |
| Initial consultation | £150-£500 | Free (AI chat) |
| Timeline to planning | 6-10 weeks | 2-4 weeks |
| PD check | Included in initial consultation | Free (AI chat) |
Important note: Mayfair Studio is not a replacement for every architectural service. Complex projects, listed buildings, and unusual designs benefit from a traditional architect's bespoke approach. Our service works best for standard residential extensions where the design principles are well-established and the homeowner values speed and cost certainty.
Frequently Asked Questions
Should I use an architect or architectural designer?
For straightforward extensions, an architectural designer (not ARB-registered but often equally competent for residential work) can save 20-40% on fees. The key differences: only ARB-registered architects can legally call themselves 'architects', and they carry mandatory PI insurance. For simple rear extensions or loft conversions, an experienced architectural designer is often sufficient. For complex projects, conservation areas, or listed buildings, a chartered architect's expertise is worth the premium.
Can I use drawings from one architect and get another to build?
Yes, but check the copyright terms in your contract. Most architects retain copyright of their drawings, granting you a licence to use them for your specific project. You cannot typically reuse drawings for a different project or modify them substantially without the original architect's consent. If you want to switch architects mid-project, negotiate copyright transfer or a broader licence upfront.
Do I need an architect for Permitted Development?
Strictly, no. PD extensions do not require planning permission, so you do not technically need planning drawings. However, you still need building regulations drawings, and many building control bodies prefer drawings from a qualified professional. Using an architect or architectural designer ensures your PD extension actually complies with PD rules and Building Regulations, which is worth the £2,000-4,000 investment to avoid costly mistakes.
How much does a planning application cost on top of architect fees?
The council's application fee for a householder planning application is £206 in England (2026). On top of this, you may need: a Design and Access Statement (usually included in architect fees), a flood risk assessment (£300-800 if required), a heritage statement for conservation areas (£500-1,500), or specialist reports like tree surveys (£400-800). Total planning-related costs beyond architect fees typically add £500-3,000 depending on complexity.
What if my planning application is refused?
Check your architect's terms regarding refused applications. Some include one redesign and resubmission in their fee; others charge extra. A good architect will have pre-application discussions with the council (£50-200 fee) to minimise refusal risk before submitting. If refused, you can appeal (free but takes 6-12 months) or redesign and resubmit (second application is free if submitted within 12 months of the original).
Are architect fees tax deductible?
For your primary residence, architect fees are not tax deductible. However, they form part of the allowable cost base if you sell the property and are liable for Capital Gains Tax (applicable if you have been absent from the property or it exceeds the private residence relief limits). For rental properties, architect fees for extensions are a capital expense that can be offset against CGT when you sell.
How do I find a good architect in London?
Start with the RIBA Find an Architect service (architecture.com) or the ARB register. Ask for recommendations from neighbours who have completed similar projects. Review portfolios for projects similar to yours. Meet at least three architects before deciding. Check reviews on Google, Houzz, or Trustpilot. Most importantly, choose someone you communicate well with, as you will be working together for several months.
Summary: Architect Fees in London
Fee range: London architects charge 8-15% of build cost (average 10-12%) or £3,000-15,000+ as a fixed fee for residential extensions. Hourly rates are £80-200 for ad-hoc consultations.
What you need: Most homeowners need RIBA stages 1-4 (concept design through building regs), costing £5,000-12,000. Stage 5 (construction monitoring) is optional but valuable.
Key advice: Compare quotes on a like-for-like basis. Check what RIBA stages are included, how many revisions are covered, and whether the measured survey is extra. Always verify ARB registration and PI insurance.
Alternative: For standard extensions, services like Mayfair Studio offer fixed-price packages from £1,295 that cover design and planning, typically saving 50-70% compared to traditional architect fees.
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