Architect Fees for London Home Projects: RIBA Stages, Services, and What to Expect

The RIBA Plan of Work 2020 defines eight stages of a construction project, from Stage 0 (Strategic Definition) through to Stage 7 (Use). For a domestic home extension or refurbishment in London, the relevant stages are typically: Stage 0 — Strategic Definition: understanding the client's aspirations, feasibility, and constraints. For most householder projects, this is absorbed into a preliminary consultation or site visit rather than a formal stage. Stage 1 — Preparation and Briefing: developing the project brief, assessing the site, understanding planning history, and setting the design direction. This typically includes a measured survey of the existing house. Stage 2 — Concept Design: producing initial design options to explore how the project aspiration can be achieved within the site constraints. Concept drawings allow the client to explore spatial options before committing to a direction. Stage 3 — Spatial Coordination (Planning Drawings): developing the chosen design to a level suitable for planning permission submission. Drawings include floor plans, elevations, sections, and a design and access statement. Stage 4 — Technical Design (Building Regulations and Construction Information): developing the design into technical drawings and specifications suitable for Building Regulations approval, tender to contractors, and construction on site. This stage includes structural engineer coordination, materials specification, and detailed joinery and fitting information. Stage 5 — Manufacturing and Construction (Contract Administration): the architect visits site at regular intervals, certifies payment to the contractor, and issues instructions and variation orders during the construction period. Stage 6 — Handover: practical completion inspection, snagging list, and handover documentation. Not all projects use all stages. The most common commission for a straightforward London rear extension is Stages 3 and 4 only — planning drawings and building regulations/construction drawings — with the homeowner managing the contract directly with the contractor. For more complex projects, or clients who prefer professional representation during construction, Stages 5 and 6 are added.

Architect fees are structured in one of three main ways: Percentage of construction cost: the architect charges a percentage of the total build cost (exclusive of VAT and professional fees). For domestic projects in London, percentage fees typically range from 8% to 15% of construction cost, depending on the complexity of the project and the stages commissioned. A 12% fee on a £150,000 rear extension and refurbishment gives an architect's fee of £18,000. Percentage fees align the architect's earnings with the project scale, but they also mean that if the construction cost rises (due to design development or client-requested changes), the architect's fee rises proportionally — even if the additional work for the architect is minimal. Fixed fee: an agreed fee for a defined scope of work, regardless of the construction cost. Fixed fees provide budget certainty and remove the conflict of interest inherent in percentage fees. The risk to the client is that significant scope changes may lead to requests for additional fee — always ensure the scope of work is clearly defined in the appointment before agreeing a fixed fee. Hourly rate: fees charged at an agreed rate per hour of time spent. Useful for undefined scope projects or additional services beyond the agreed scope. London architect hourly rates range from £80-£200/hour for experienced chartered architects. Hourly rate appointments can be difficult to budget for at the outset, and it is advisable to agree a maximum budget estimate upfront even when the appointment is hourly. For most London homeowner projects, a fixed fee agreed for a clearly defined scope (e.g. "planning drawings and Building Regulations package for a two-storey rear extension at [address]") is the clearest and fairest arrangement for both parties.

Typical architect fee ranges for common London home projects (covering Stages 3 and 4 — planning drawings and Building Regulations/construction drawings — but not contract administration unless stated): Single-storey rear extension (25-35m²): £4,000-£7,000. Two-storey rear extension (50-70m²): £6,000-£10,000. Rear dormer loft conversion: £4,500-£8,000. Full house refurbishment (no extension): £4,000-£9,000 depending on scope. Wrap-around extension (kitchen extension plus side infill): £7,000-£12,000. Major house extension and remodelling (construction value £200,000+): £15,000-£30,000 for Stages 3-4; £25,000-£50,000+ for full Stage 3-6 services. Where contract administration (Stage 5) is included, add approximately 3-5% of construction cost for monthly site visits, payment certification, and instruction issuing, or a fixed additional fee of £3,000-£8,000 for a typical extension project. These ranges reflect the London market. Architect fees in the South East outside London are typically 10-20% lower.

A fee proposal from an architect should clearly state what is and is not included. Standard inclusions in most Stages 3-4 domestic fee proposals: a measured survey of the existing property (or working from a survey you commission separately); concept design options; planning application drawings (existing and proposed floor plans, elevations, and sections); design and access statement; planning application submission and management; Building Regulations drawings; structural engineer coordination (the structural engineer's fees are usually separate — typically £800-£2,500 for a residential extension); specification of materials and finishes; and one set of contractor tender drawings. Typical exclusions and additional costs: statutory application fees (planning fee currently £258 for a householder application, Building Control fee varies by project value); structural engineer's fees; party wall surveyor fees; acoustic or daylight consultant fees; pre-application advice fees; planning agent fees if a separate planning specialist is appointed; changes to design after a planning application is submitted; additional drawings required by the contractor during construction beyond the agreed set; and contract administration services (site visits, payment certification). Always read the exclusions as carefully as the inclusions, and always ask whether the fee covers resubmission if the planning application is refused.

When obtaining fee proposals from multiple architects, the headline number alone is not a reliable basis for comparison. Two quotes for the same project may differ significantly in scope. To compare fairly: ask each architect to break down the fee by stage (Stage 3, Stage 4, Stage 5 separately); confirm whether a measured survey is included or if you need to commission one separately (measured survey costs £400-£1,200 for a typical London house); confirm whether the fee covers the planning application management or only drawing production; ask what happens to the fee if the planning application is refused and resubmission is required; confirm the number of design iterations included before additional fees apply; and ask whether the structural engineer coordination includes issuing a brief and reviewing the SE drawings, or whether you need to manage the structural engineer separately. A lower headline fee that excludes measured survey, planning management, and Building Regulations detail design may cost more overall than a higher headline fee that includes all these elements. The most useful question to ask each architect is: "What will I receive at the end of your appointment, and what will I still need to procure separately to get to a point where a contractor can start on site?"

For straightforward householder applications — a simple single-storey rear extension, a small loft conversion, a garage conversion — you are not legally required to use a qualified architect. Architectural technicians (MCIAT), building surveyors, and specialist residential design draughtsmen can all produce drawings of sufficient quality for planning and Building Regulations applications. These practitioners typically charge less than chartered architects (RIBA members), and for a simple planning drawings package they can provide good value. The case for using a chartered architect (or RIBA-chartered practice) is strongest when: the project involves design complexity, unusual planning constraints, or a conservation area or listed building where design quality and heritage sensitivity are under scrutiny; you need a single point of professional accountability who can be held to RIBA Code of Conduct if something goes wrong; the project is large enough that contract administration — having a professional certify payments and manage the contract — provides meaningful financial protection; or you intend to use a JCT (Joint Contracts Tribunal) building contract, which requires a contract administrator to operate. For a standard rear extension or loft conversion in a non-designated area, a skilled architectural technician or residential designer can often deliver equivalent drawing quality to a chartered architect at meaningfully lower cost. The critical question is not the title of the person producing the drawings but the quality of the service, their experience with the local planning authority, and what happens if the application or design needs revision.