Appointing an architect for a London residential project isn’t a single decision. It’s a framework of decisions that determines whether the finished home matches the brief the family walked in with. Get the framework right at the start and every downstream choice becomes easier. Get it wrong and no amount of clever design during construction rescues the project.
Most homeowners approach architect selection by looking at portfolios and asking about fees. Neither is the right starting point. Portfolios show finished photographs, not finished budgets. Fees are meaningless without understanding what they cover.
The decision framework below covers the six criteria that actually decide project outcomes, developed through years of running residential briefs as London architects across boroughs from Wandsworth to Camden. Applied properly at the appointment stage, the framework saves families months of misdirected work and tens of thousands of pounds in avoidable variations.
Criterion 1: Practice Model, Design Only vs Design and Build vs Full Service
The practice model determines how risk, cost certainty, and design flexibility get distributed between the architect and the client during construction.
| Model | Cost certainty | Design flexibility | Client decision load |
| Design only | Moderate (at tender) | High throughout | Heavy |
| Design and Build | High (fixed at contract) | Low mid construction | Light |
| Full Service | Adjustable per phase | Adjustable per phase | Adjustable |
Design only suits ambitious briefs where architectural intent needs to lead every construction decision. Design and Build suits predictable briefs where cost certainty matters more than mid project flexibility. Full Service suits complex briefs where the delivery model needs to adapt across project phases.
The mistake most homeowners make is treating this as a fee comparison rather than a risk allocation choice.
Criterion 2: In House vs External Structural Engineering
Every extension involves architectural intent meeting structural reality. Where that collision happens determines whether the design gets built as drawn or gets value engineered into something the client didn’t sign off on.
Pros of in house structural engineering:
- Beam sizes get sketched into the concept before the design locks in
- Coordination errors between drawings never surface at Stage 4
- One office signs off both architectural and structural drawings
- Building Regulations submission goes in as a single coordinated pack
Cons of external structural engineering:
- Cost transparency (engineer’s fee is separate and visible)
- Client can select engineer based on specific project type
- Practices can access broader engineering expertise for unusual briefs
For most residential extensions, in house structural engineering delivers better outcomes because the disciplines coordinate in real time rather than through drawing revisions after the fact.
Criterion 3: Borough Specific Experience
Every London borough interprets national planning policy through its own local plan, supplementary planning documents, and case officer culture. A practice with 20 approved applications in Camden over the past two years understands Camden’s decision pattern in ways that a suburban firm cannot.
Recent borough experience matters more than portfolio breadth on ambitious residential briefs. Ask the practice specifically:
- How many applications submitted to your borough in the last 18 months?
- What proportion were approved on first submission?
- Which recent refusals came from your borough, and what did you learn?
A confident practice answers these questions with specifics. A vague answer suggests the borough experience isn’t as deep as the marketing implies.
Criterion 4: Project Management Structure During Construction
Design fees typically cover RIBA Stages 1 to 4. Construction stage administration is where budgets either hold or drift.
Weekly site meetings with architect, structural engineer, and building control input on the agenda is the standard that keeps overruns short. Ask specifically who runs those meetings, what the weekly rhythm looks like, and how variation costs get communicated to the client.
The named project manager on the client’s project should be identifiable at the appointment stage, not assigned later. Practices without a clear PM structure produce the variation cost surprises that show up on the final invoice.
Criterion 5: Fee Structure Transparency
Architectural fees come in three common structures. Each carries different incentives.
- Percentage of build cost, where the fee scales with project size, aligns architect and client on cost control at concept stage, but can drift with variations
- Fixed fee, delivering cost certainty for the client and incentivising efficient design work, but requiring clear scope definition at appointment
- Time charge or hourly rates, flexible for evolving briefs, but requiring trust and regular billing reviews
Neither structure is inherently better than the others. The right choice depends on brief complexity, client preferences, and how tightly the scope can be defined at appointment.
Understanding what each structure actually costs against a specific brief becomes easier once realistic build cost figures are on the table. Running the numbers through an extension cost calculator at the pre appointment stage gives clients a working budget figure to test fee proposals against, which prevents the common problem of comparing percentage fees against fixed fees without a common baseline.
Criterion 6: References From Recent Completed Projects
Portfolio photographs show what the finished house looks like. References from clients whose builds completed in the last 12 to 18 months show what the process felt like.
Ask for two or three recent clients willing to speak on the phone. Questions worth asking them:
- Did the final budget land within 5 percent of the pre construction cost plan?
- Did the completion date land within 4 weeks of the original programme?
- Would you appoint the same practice again on your next project?
A practice confident in its delivery record supplies references without hesitation. Reluctance to share recent references is a red flag on any residential appointment.
How to Apply the Framework
The six criteria above form the framework. Apply them to three or four shortlisted practices at the initial meeting stage rather than trying to compare based on portfolios alone.
The practice that scores well across all six criteria delivers the project. The practice that scores well on one or two criteria and dodges the others usually produces the project that overruns.
