Key takeaways
- The stages exist to make expensive decisions in the order that keeps cheap ones cheap.
- Cost certainty is mostly gained during design development, not during concept design.
- Signing off a stage you have not read moves the problem downstream where it costs more.
- RIBA and AIA use different labels for the same underlying progression.
Continue exploring all architectural design process guides.
Why there are stages at all
Design is a sequence of narrowing decisions. The stages are not administrative theatre — they are the points at which a decision stops being cheap to reverse.
Move a staircase during concept design and you redraw a plan. Move it after the structural engineer has designed the floor plates and the services have been routed around it, and you are paying three consultants to redo coordinated work.
Stage 1: Brief
Establishes what the building has to do. Who uses it, what happens where, what the budget and programme actually are, and what the site and the regulations will and will not allow.
What gets fixed: the problem definition.
Common failure: a brief that lists rooms but not requirements. “Four bedrooms” is a schedule. “Four bedrooms, two of which are used as offices during the day and must be acoustically separated from the living space” is a brief.
Stage 2: Concept and schematic design
Tests arrangements. Massing, orientation, how the building sits on the site, rough room relationships, circulation. Output is deliberately loose because the purpose is comparison, not resolution.
What gets fixed: the arrangement — which is the single most consequential thing in the project.
Common failure: falling in love with a render before the arrangement has been tested against the brief. See floor plan vs elevation vs section for why a render is not a commitment to anything.
Stage 3: Design development
Fixes what was loose. Dimensions, structural approach, envelope build-up, service routes, principal materials. Coordination between architecture, structure and services happens here.
What gets fixed: almost everything that drives cost.
Common failure: deferring material decisions past this point. Materials have structural, fire and detailing consequences — choosing them late means reopening resolved work. The material selection process belongs here, not after.
Stage 4: Technical design and construction documents
Produces what a contractor prices and builds from: fully dimensioned drawings, details, schedules and specifications.
What gets fixed: the instruction set.
Common failure: assuming this stage is just “drawing up” what was already decided. It is where every junction that was drawn as a line becomes a detail with real materials, tolerances and sequencing — and where unresolved earlier decisions surface as questions.
Stage 5: Construction stage
Answering contractor queries, reviewing samples and shop drawings, inspecting against the specification, administering the contract.
What gets fixed: nothing, ideally. Changes here are the most expensive changes available.
The cost curve
| Stage | Cost to change the arrangement | Cost certainty |
|---|---|---|
| Brief | Negligible | None |
| Schematic design | Low | Rough order of magnitude |
| Design development | Moderate | Substantial |
| Technical design | High | High |
| Construction | Highest | Fixed by contract |
The two columns move in opposite directions, which is the whole problem: you have the most freedom when you know the least, and the most information when you have the least freedom.
What to do with this
- Decide at the stage the decision belongs to. Ask your architect which decisions are open now and which are closing.
- Read what you sign off. Approval is not a formality; it is the point where a decision stops being free.
- Ask what a change would cost before requesting it. Sometimes the answer is “nothing” and sometimes it is three weeks.
For what your architect is responsible for across these stages, see what does an architect do. For the overall picture, see the architectural design process guide.
Frequently asked questions
How long does each stage take?
It varies enormously with project size, procurement route and approval requirements. What is more predictable is the ratio: concept work is short, design development and technical design consume most of the programme.
Can stages overlap?
They often do, particularly on fast-track projects. Overlapping increases risk, because later stages are being built on decisions the earlier stage has not yet finished making, and rework follows when those decisions move.
What is the difference between RIBA stages and AIA phases?
They describe the same progression with different boundaries and names. RIBA runs 0 to 7 including strategic definition and in-use; the AIA phases run from schematic design to construction administration. Neither changes what actually has to be decided.
At which stage should I fix the budget?
The budget should be a constraint in the brief and tested at every stage. Meaningful cost certainty arrives during design development, when structure, envelope and principal materials are resolved.
Sources
- RIBA Plan of Work — Royal Institute of British Architects (RIBA) Accessed August 27, 2026.