Estimate Architect Costs for Extensions, New Builds & Commercial Projects – Updated 2026
Estimate the architect's fees for your UK project in 2026. Enter the project type, construction cost, and scope of services required. The calculator covers percentage-based fees (most common for domestic and commercial projects), fixed fees, and hourly rates — and breaks the total down by RIBA work stage.
Architect fees are typically structured around the RIBA Plan of Work 2020, which divides a building project into eight stages (0–7). The percentage of the total fee allocated to each stage reflects the relative amount of work involved. The splits below are indicative — actual splits vary by project type and the scope agreed with the architect.
The table below provides indicative architect fee ranges for common UK project types in 2026, expressed as a percentage of construction cost and as indicative fixed fee ranges. Fees at the lower end typically reflect straightforward projects, larger contracts (the percentage falls as contract value increases), and practices outside London. Higher fees reflect complex, heritage, or highly bespoke projects, or central London practices.
| Project Type | Full Service Fee (%) | Planning Only (%) | Indicative Fixed Fee Range | Notes |
|---|---|---|---|---|
| House extension – small (<30 m²) | 12–20% | 6–10% | £3,500–£9,000 | Higher % due to small contract value; fixed fees common |
| House extension – medium (30–60 m²) | 10–16% | 5–8% | £6,000–£18,000 | Most common domestic project; percentage most usual |
| House extension – large (60–100 m²) | 8–14% | 4–7% | £12,000–£35,000 | Economies of scale; can negotiate fixed or hybrid |
| Loft conversion | 10–18% | 5–9% | £4,000–£14,000 | Varies by type: dormer, hip-to-gable, mansard |
| New build single dwelling | 8–14% | 4–7% | £15,000–£60,000+ | Self-build vs developer specials; varies hugely by specification |
| New build 1–4 units | 7–13% | 3.5–6% | £25,000–£120,000+ | Economy of scale; developer-led projects at lower end |
| New build residential (5–50 units) | 5–10% | 2.5–5% | £50,000–£500,000+ | Larger projects: fee falls as % but absolute value increases |
| Commercial – small (shop fit / office) | 8–14% | 4–7% | £8,000–£30,000 | Interior-only often lower; shell and core higher |
| Commercial – medium building | 6–12% | 3–6% | £30,000–£200,000+ | Depends heavily on complexity and fit-out specification |
| Heritage / listed building works | 12–22% | 6–12% | £10,000–£80,000+ | Higher due to specialist knowledge, Historic England liaison |
| Interior design / fit-out only | 8–15% | — | £3,000–£25,000 | No planning; scope limited to interiors and specification |
| Feasibility study only | — | — | £800–£5,000 | Day rate / fixed fee; scoped tightly to the question |
| Role / Grade | Scotland / N Ireland | North England / Wales | Midlands / SW | South East | Greater London |
|---|---|---|---|---|---|
| Part I (Architectural Assistant) | £35–£50/hr | £38–£55/hr | £40–£58/hr | £45–£65/hr | £55–£80/hr |
| Part II (Architectural Assistant) | £45–£65/hr | £50–£70/hr | £52–£75/hr | £60–£85/hr | £72–£105/hr |
| Chartered Architect (ARB / RIBA) | £60–£90/hr | £65–£100/hr | £70–£110/hr | £80–£130/hr | £100–£170/hr |
| Senior Architect / Associate | £75–£110/hr | £80–£120/hr | £85–£130/hr | £100–£155/hr | £125–£200/hr |
| Director / Partner | £90–£140/hr | £100–£155/hr | £108–£165/hr | £125–£200/hr | £160–£260/hr |
All hourly rates exclude VAT. Rates shown are for time charged to clients (billing rates), which include practice overhead and profit on top of the individual’s salary. The typical billing multiplier is 2.5–3.5× the individual’s direct cost. Hourly rates are most commonly used for feasibility studies, additional services outside the agreed scope, and minor variation work.
In addition to the architect’s fee, clients should budget for disbursements (out-of-pocket expenses incurred on the client’s behalf) and fees for specialist consultants typically engaged by the architect or directly by the client. These are additional to the architect’s fee and are not always clearly communicated upfront.
| Item | Typical Cost (2026) | Notes |
|---|---|---|
| Planning application fee (householder) | £258 (England, 2024+) | Set fee for householder planning applications in England; Wales and Scotland differ; paid direct to LPA |
| Planning application fee (new dwelling) | £578 per dwelling (England) | Full planning application fee; increased significantly in 2024; architect usually submits on client’s behalf |
| Building Regulations application (Full Plans) | £200–£900+ | Charged by Building Control body; based on project value; full plans more expensive than Building Notice |
| Structural engineer | £800–£5,000+ | Required for most extensions, loft conversions, and new builds; separate appointment or included in architect’s co-ordination |
| Energy assessor (SAP / Part O) | £200–£800 | SAP calculation for Building Regs Part L; required for most new builds and significant extensions |
| Topographic survey | £400–£2,000 | Accurate site survey to 1:500 or 1:200; required for most new builds and complex extensions |
| Measured building survey | £500–£3,000 | Accurate floor plans and elevations of existing building; needed for extensions and alterations |
| Party wall surveyor | £700–£2,500 per owner | Required if works affect a party wall; each party appoints their own surveyor or agree one agreed surveyor |
| Ground investigation / soil survey | £800–£5,000+ | Trial pits or boreholes; required for new builds and extensions on unknown ground; structural engineer advises |
| Tree survey (BS 5837) | £300–£1,500 | Required by many LPAs when trees are near the development; arboricultural impact assessment |
| Ecological survey / bat survey | £400–£3,000 | Often required as planning condition; timing-sensitive (bat surveys seasonal); specialist ecologist |
| Architect’s travel / mileage | 45p–65p per mile | HMRC approved mileage rate; architect may charge travel time at hourly rate in addition |
| Print / CAD plotting | £50–£300 per submission | Planning drawings, Building Regs packs; largely displaced by digital submission but still charged by some |
Architect fees in the UK are not regulated — since the abolition of the RIBA mandatory fee scales in 1982, architects have been free to charge whatever they and their clients agree. This means fee levels vary significantly between practices, regions, and project types. In 2026, the typical approach to architect fees for domestic projects is a percentage of the construction cost, though fixed fees (lump sums for an agreed scope) and hourly rates are also common, particularly for smaller or clearly-defined scopes.
The percentage-based approach aligns the architect’s income with the value of the project — as the project grows more complex or increases in scale, the fee increases proportionally. However, this can create a perverse incentive (the more the client spends on construction, the more the architect earns), which is why many experienced clients prefer negotiated fixed fees for well-defined scopes. Most practices will quote a fixed fee once the brief is clear and the scope is agreed, even if the initial fee proposal is percentage-based.
In the UK, the title “architect” is legally protected under the Architects Act 1997 — only individuals registered with the Architects Registration Board (ARB) can call themselves an architect. RIBA membership (Chartered Architect) is an additional professional qualification above ARB registration. When engaging an architect, always check they are ARB-registered. Many designers offer similar services without being ARB-registered — these are typically called “architectural designers”, “architectural technologists”, or “building designers”. These can be excellent and cheaper for straightforward projects, but lack the full professional qualification and liability insurance of a Chartered Architect.
There is no mandatory fee scale for architects in the UK. Fees were deregulated in 1982, and architects are free to charge what the market will bear. This means significant variation between practices — always get at least three quotes from different practices for any significant project.
For a medium-sized house extension (30–60 m²) with full architectural services in the UK in 2026, a typical fee range is 10–15% of construction cost. On a £100,000 extension, this is £10,000–£15,000 excl. VAT. Fees above 15% for a standard extension or below 8% for full service should raise questions about what is included.
Engaging an architect for Stages 0–3 only (feasibility through planning application) typically costs approximately 40–50% of the full-service fee. This is a popular option for homeowners who want professional design and planning support but plan to manage the technical stages themselves or use a building technologist.
Most architect practices are VAT registered and charge 20% VAT on top of their fees. This adds significantly to the total cost — a £12,000 fee becomes £14,400 with VAT. Small sole practitioners below the VAT threshold (£90,000 turnover in 2026) may not charge VAT. Always confirm VAT status when comparing quotes.
Architect fees typically do not include planning application fees, structural engineer fees, building regs fees, surveys, or specialist consultant fees. These disbursements can add £2,000–£15,000+ to the total professional fees on a domestic project. Always ask for a full schedule of anticipated disbursements at the outset.
Only individuals registered with the Architects Registration Board (ARB) can legally call themselves an “architect” in the UK. Check any professional’s ARB registration at arb.org.uk before appointing. RIBA membership (letters RIBA or ARB after the name) is an additional mark of professional standing. Many competent “architectural designers” or “building designers” offer similar services without being ARB-registered — these can be good value for simpler projects.
Works to listed buildings or in conservation areas attract a significant fee premium — typically 2–5 percentage points above standard rates. This reflects the additional time required for heritage research, liaison with Historic England or local conservation officers, Listed Building Consent applications, and the specialist knowledge required to specify sympathetic and approved materials and methods.
Contract administration (Stage 5) — where the architect makes regular site visits, checks progress against the specification, certifies payments, and administers the building contract — is one of the most valuable parts of the architect’s service. It protects the client against poor workmanship and contractual disputes. The typical fee for contract administration alone is approximately 3–6% of construction cost for a domestic project.
Planning application fees in England rose significantly in December 2024: householder applications increased to £258 (from £206) and full applications for new dwellings rose to £578 per dwelling. These fees are paid to the local planning authority and are separate from the architect’s fee for preparing the application. Budget for these in addition to professional fees.
The value of a good architect extends far beyond drawings. A skilled architect will: challenge your brief and improve the design; navigate planning policy to maximise permitted development; add significant value to your property; identify buildability issues early; specify materials and details that avoid costly problems; and protect you during construction through contract administration. The fee is an investment, not just a cost.
For very simple, permitted development works (e.g. a small rear extension within PD limits, a garage conversion, a simple loft conversion in a standard house), an architectural technologist (MCIAT) or experienced building designer can often provide the necessary drawings and Building Regulations application at lower cost than a Chartered Architect. Consider the complexity and value of your project before deciding whether full architectural services are needed.
Always get at least three fee proposals from different practices before appointing. Compare them on a like-for-like basis — same scope, same RIBA stages, VAT status confirmed. Cheapest is not always best; consider the practice’s experience with similar projects, their portfolio, client references, and how well you communicate with them. A project can span 1–3+ years — you need to trust and communicate well with your architect throughout.
Architect fees in the UK in 2026 vary widely by project type, scope, and region. For the most common domestic project — a house extension with full services — typical fees are 10–15% of the construction cost. On a £120,000 extension, this is £12,000–£18,000 plus VAT. For planning only (no technical design or site supervision), expect to pay approximately 5–8% of construction cost. New builds typically attract 8–12% for full service. Hourly rates for a Chartered Architect range from approximately £65/hr in North England to £170/hr in central London. These are broad benchmarks — always obtain quotes from at least three practices for your specific project.
You are not legally required to use an architect for a house extension — an architectural technologist, building designer, or even a competent builder can prepare the drawings for a simple extension. However, a Chartered Architect brings design expertise, planning knowledge, project management skills, and professional indemnity insurance that can add significant value — particularly for extensions involving planning applications, complex sites, listed buildings, or where you want to maximise the value added to your property. For straightforward permitted development extensions (no planning needed), a building technologist is often adequate and more affordable. For anything requiring planning permission or Building Regulations full plans approval, the investment in an architect or technologist is almost always worthwhile.
Planning drawings (Stages 2–3) show the design of the proposed extension or building from the outside — floor plans, elevations, and site plan — at a level of detail sufficient for the local planning authority to assess the visual impact, massing, and relationship to neighbours. Building Regulations drawings (Stage 4) are far more detailed technical documents showing how the building will be constructed — wall build-ups, insulation specifications, structural details, drainage, ventilation, and compliance with all Approved Documents. Planning drawings typically take 30–50 hours to prepare; Building Regulations drawings take 60–120 hours for a medium extension. This is why Stage 4 (technical design) typically accounts for approximately 25% of the total fee.
When comparing fee proposals, ensure you are comparing like for like: (1) Same RIBA stages included: confirm exactly which stages are included in each proposal. (2) VAT: confirm whether the fee is quoted inc or excl VAT; a £10,000 excl VAT fee is £12,000 inc VAT. (3) Disbursements: are planning fees, survey costs, and specialist consultant fees included or additional? (4) Scope of services: does the fee include contract administration and site visits, or just drawings? (5) Number of design iterations: does the fee include a set number of revisions, or is additional design work charged at hourly rates? A well-written fee proposal should answer all these questions clearly.
Yes — and this is a common approach for domestic projects. Engaging an architect for Stages 0–3 only (up to and including the planning application) typically costs 40–50% of the full-service fee. Once planning permission is granted, you can then appoint an architectural technologist (typically cheaper than an architect for technical stages) to prepare Building Regulations drawings, and manage the project yourself or through a main contractor. The risk of this approach is that you lose the continuity of having one professional oversight throughout — the Stage 5 contract administration is where many client-contractor disputes are resolved by the architect. Weigh the fee saving against the value of professional oversight during construction.
Contract administration (RIBA Stage 5) involves the architect acting as the client’s representative during construction. It typically includes: regular site visits (typically fortnightly for a domestic project) to inspect work quality; certification of stage payments to the contractor; issuing instructions (variations, clarifications, RFIs); managing the contract (extensions of time, loss and expense claims); inspecting work at key stages (foundations, DPC, roof structure, first and second fix); and certifying practical completion and managing the snagging process. Contract administration typically costs 3–6% of construction cost and is often the most valuable part of the architect’s service — a good contract administrator will save the client far more than their fee through preventing substandard work and managing contractor claims.
For a typical loft conversion in the UK in 2026, an architect’s fee for full services (planning through contract administration, if planning is required) is approximately 10–18% of the construction cost, or approximately £4,000–£14,000 as a fixed fee. The construction cost of a standard dormer loft conversion ranges from approximately £30,000–£60,000, making the full-service architect fee approximately £3,000–£11,000 plus VAT. Dormer and hip-to-gable conversions visible from the street typically require planning permission; rear dormers on houses not in conservation areas may be permitted development. Where permitted development applies, planning drawings are not needed and the fee is lower. Always confirm with your local planning authority.
The RIBA Standard Professional Services Contract (for commercial clients) or the RIBA Domestic Professional Services Contract (for homeowners, provides additional consumer protections) are the standard appointment documents in the UK. These clearly define the services to be provided, the fee and payment terms, the basis for additional charges, intellectual property rights, professional indemnity insurance requirements, and dispute resolution procedures. Some practices use their own bespoke appointment documents — these are acceptable but less familiar and should be reviewed carefully. Never commence work without a signed appointment — verbal agreements are legally enforceable but extremely difficult to evidence in a dispute.
Architect fee resources UK 2026: RIBA – Find an Architect | ARB – Check the Register | CIAT – Find an Architectural Technologist | Planning Portal – Application Fees | GOV.UK Planning Fee Calculator