RC residence, 40 tsubo — 17-month model
| Stage | Duration |
|---|---|
| Schematic design | 2.5 months |
| Detailed design | 3 months |
| Permit + structural review | 1.5 months |
| Contractor selection | 1 month |
| Ground improvement + foundation | 1.5 months |
| Frame (concrete + curing) | 3 months |
| Envelope, waterproofing, roof | 1.5 months |
| Fit-out and services | 2.5 months |
| Inspection and handover | 0.5 month |
Wood residence, 35 tsubo — 9-month model
| Schematic + detailed design | 3–4 months |
| Permit | 1 month |
| Ground + foundation | 1 month |
| Framing + roof | 0.5 month |
| Fit-out and services | 2.5 months |
| Inspection and handover | 0.5 month |
Three forces that shape the calendar
1. Concrete curing
RC frames need minimum 3 days before formwork can be stripped, and 28 days to design strength. Rushing the strip causes cracking and weakens the shell.
2. Rainy season and typhoons
June–July (tsuyu) and August–October (typhoons) halt exterior works. Targeting foundation pours for spring or autumn dramatically tightens the calendar.
3. Permit congestion
Osaka and Tokyo review bodies bunch up in April and October — expect roughly two weeks of slippage. Pre-consultation with the architect mitigates this.
Compared with Western practice, Japanese timelines look long. The reason is permit rigour and the curing / drying time demanded by the humid climate. Length here buys precision, not slack.