How to use the project timeline estimator
Clients almost always ask two questions at the first meeting: how much will it cost, and how long will it take? This estimator answers the second one in a few seconds. It builds a programme from typical stage durations, then scales them for the type of building, its size and how complicated it is, so you can talk through a realistic timeline before you've drawn a line.
- Pick a framework. Choose the RIBA Plan of Work 2020 stages (common in the UK, Ireland, Australia and much of Asia) or the AIA phases used in North America.
- Describe the project: type, gross floor area in ft² or m², and complexity. Use "complex or listed" for heritage buildings, difficult sites, steep slopes or heavy consultant coordination.
- Set the approvals and tender time you expect locally. Planning permission, permits or design review go in the approvals field; contractor tendering or bidding goes in the tender field.
- Choose a start date. The table gives start and finish dates for every stage, and the summary shows total design time, time on site and the expected handover date.
How the timeline is calculated
Design stage weeks = base weeks × type design factor × (area ÷ 250 m²)^0.25 × complexity
Construction weeks = 40 × type build factor × (area ÷ 250 m²)^0.28 × complexity
Total = design stages + approvals + tender + construction + handover
The base durations describe a standard new house of about 250 m² (2,700 ft²). Duration doesn't rise in proportion to area: a building ten times bigger takes nowhere near ten times as long, because larger teams and crews work in parallel. That's why the size factor uses a low power, so 2,500 m² comes out at roughly 1.8 times the design time and 1.9 times the build time of the reference house. Type factors adjust for what is typical: fit-outs have short builds, civic and healthcare buildings need more consultation and coordination. Size scaling is limited to between 0.4 and 4 times the reference.
| RIBA stage | AIA equivalent | Base weeks |
|---|---|---|
| 0 Strategic Definition + 1 Preparation and Briefing | Pre-Design | 2 + 3 |
| 2 Concept Design | Schematic Design | 6 |
| 3 Spatial Coordination | Design Development | 7 |
| Planning / permits | Permitting | Your input |
| 4 Technical Design | Construction Documents | 10 |
| Tender | Bidding or Negotiation | Your input |
| 5 Manufacturing and Construction | Construction Administration | 40 |
| 6 Handover | Closeout | 4 |
In the RIBA sequence the planning application goes in after Stage 3, so approvals sit before Technical Design. In the AIA sequence, permits are usually applied for with the construction documents, so the permit period follows them. Either way, the estimator assumes stages run one after another; fast-track overlaps would shorten the total.
Worked examples
A new 2,500 ft² house (AIA)
Standard complexity, 10 weeks for permits and 6 weeks of bidding. Design phases total about 28 weeks and construction about 39 weeks; with permits, bidding and closeout the whole project runs about 87 weeks, roughly 20 months from the first meeting to move-in.
A 60 m² kitchen extension (RIBA)
Extension type, simple complexity, 8 weeks for a householder planning application and 4 weeks to tender. Design comes out at about 12 weeks and construction at about 14 weeks, so with approvals, tender and handover the project takes roughly 41 weeks, a little over 9 months.
A 5,000 m² office (RIBA)
Commercial type, complex, with 16 weeks for planning and 10 weeks to tender. Design stages run to about 78 weeks and construction to about 104 weeks, for a total of around 214 weeks, just over four years from Strategic Definition to Handover.
Who this estimator helps
- Architects preparing fee proposals and resourcing plans, and setting expectations at the first client meeting.
- Project managers and developers building a first programme for funding, land deals or lettings.
- Interior designers scoping fit-outs and showing clients where design ends and site work begins.
- Homeowners planning a new house or extension and wondering when they can move in.
- Students and graduates learning how the RIBA and AIA stages fit together.
Practical tips
- Pair the programme with money: estimate the build with the construction cost calculator, then split your fee across the same stages with the architect fee calculator.
- Turn the brief into a structured questionnaire with the design brief generator so Stage 1 or Pre-Design doesn't drag on.
- Add buffer for client decisions: two weeks of sign-off per stage is common and isn't included above.
- Check the zoning envelope early with the setback calculator and FAR calculator; a redesign after a refusal can add months.
- Order long-lead items such as windows, lifts and structural steel as soon as the design is fixed.
Speed up concept design by turning early sketches and massing models into photoreal images for client sign-off with Sketch to Render.
