How to read the reference duration
The range comes from published duration-quota tables for the building type and structure you selected, at a reference scale, then adjusted for your floors and gross floor area. It is a planning cross-check for bidding — not a compliance value.
| Building type | Typical structures | Reference range at typical scale |
|---|---|---|
| Residential building | Masonry, RC frame, RC shear wall | 120–190 d (low/multi), 300–640 d (high/tall) |
| Office / administrative | RC frame, RC shear wall, steel | 220–270 d (multi), 330–720 d (high/tall) |
| Retail / commercial | RC frame, steel | 120–180 d (low), 180–250 d (multi) |
| School / education | Masonry, RC frame | 130–195 d (low), 225–285 d (multi) |
| Hospital / medical | Masonry, RC frame | 240–345 d (multi), 480–580 d (high) |
| Industrial plant | RC frame, steel | 110–205 d (single/multi-storey halls) |
Ranges are indicative, in calendar days, for the reference scale of each row (see the basis line in the tool). Your project may sit well outside them.
How to use it in a bid
- Pick the type and structure first. They move the range more than anything else — steel frames run fastest per unit area, masonry slowest.
- Enter floors and area. Floors set the height tier; area shifts the range around the reference scale. The basis line under the result shows every adjustment applied.
- Compare your promised duration. Shorter than the floor means an aggressive promise — be ready to justify method and resourcing, and check the liquidated-damages rate. Longer than the ceiling is safe but may lose scoring points where shortest duration wins.
- Convert for the team plan. Tenders count calendar days; your crew plan counts working days. The converter uses your statutory-holiday setting.
Calendar days vs working days
Tender documents express the construction period in calendar days — weekends and public holidays count. A crew plan expressed in working days excludes them. As a rule of thumb, 300 calendar days contain about 205 working days at 11 statutory holidays per year. If your project shuts down for spring festival or winter, add those days on top before you promise a calendar duration.
Sources and caveats
- Reference ranges are compiled from published duration-quota tables, including the national installation duration quota (《全国统一建筑安装工程工期定额》) and provincial editions, cross-checked against international rules of thumb.
- Quota editions differ by region and year. Provincial standards, the current edition and the tender document always prevail.
- Norms assume conventional methods, normal site access and standard weather. Winter concreting, rainy-season earthworks, constrained urban sites and long-lead equipment (elevators, curtain wall) all push the real duration up.
- Infrastructure works (roads, bridges, utilities) follow separate norms and are not covered by this tool.
FAQ
What is a construction duration norm?
A duration norm is a reference construction period published by government or industry bodies for standard building types at standard scales. In China the classic reference is the national installation duration quota; many provinces publish their own editions. Bidders use these ranges to sanity-check whether a promised schedule — their own or a competitor's — is realistic for the building type, structure and size involved.
How should I use a duration estimate in a tender?
Estimate first, then compare. If your promised duration is shorter than the norm floor, expect scrutiny: be ready to justify the method, resourcing and working-hours plan, and check the liquidated-damages rate before committing. If it is longer than the norm ceiling, confirm the tender does not score shortest duration, and make sure the required completion date in the tender document still works.
Calendar days vs working days — which does my tender mean?
Tender documents almost always express the construction period in calendar days, so weekends and public holidays count. Working days exclude weekends and statutory holidays. This tool converts both ways using the number of statutory public holidays per year — roughly 11 to 13 in China and 10 to 11 in the United States — and you can set project shutdown days on top.
What affects construction duration the most?
In order of impact: structure type (steel is fastest, masonry slowest per unit area), number of floors, and gross floor area. After that come site constraints, season and weather — winter concreting and rainy-season earthworks routinely add weeks — plus procurement lead times for long-lead equipment such as elevators and curtain wall systems.
Are these duration norms official?
The ranges are compiled from published duration-quota tables and industry references, not from any single current official edition. Regional standards, the current quota edition and your tender document always prevail. Treat the output as a planning reference and a cross-check, never as a compliance value.
This tool provides planning reference only and is not engineering or legal advice. The tender document, current quota editions and your project's own conditions always prevail. DurationKit is a free tool by the team behind the Gantt chart generator and bid tools at ziliaobiao.cn.