Project schedule for a detached house: trades, companies and deliveries
Which company takes each trade, when does each work package start and when does each delivery arrive, so that the house is handed over early, crane and scaffold are rented briefly and material does not wait on the site?
Drag to rotate, scroll or pinch to zoom. The schedule below plays the whole build, from site setup to handover. While the interior trades work, the street side of the house is cut open. Hover a bar for details. Plan computed with a Timefold model.
The planning question
A fictional detached house of about 150 m² living area: a basement of precast concrete elements, ground floor and attic floor of sand-lime blocks, a 40° gable roof, external insulation with render, a heat pump with underfloor heating. Building starts on 1 March. 33 work packages in 20 trades lead from site setup to handover. A trade is one craft with its own contract, for example roofing or screed. Each trade has 1 to 3 candidate companies with crew size, day rate and their own calendar: other sites and company holidays.
The site is small. Materials wait on a storage area of 45 m², the tower crane and the scaffold are rented by the day, and several deliveries need the crane. Concrete is poured on arrival, so the truck mixers come on the day of the pour. Windows, roof timber and the kitchen have production lead times. Screed, the cement layer on top of the underfloor heating, needs 28 days before tiles and 35 days before parquet.
Companies, prices, durations and lead times are assumptions for this example.
How we plan it
The Timefold model chooses the company per trade, hold days per work package and the delivery day per material. For every change it builds the whole schedule: each work package goes on the earliest working days after its predecessors and their drying times, when its company is free, the house has room and the material can be there. From that schedule it derives crane and scaffold rental, the storage area day by day and the costs: company prices, rentals, materials waiting, idle days and every day until handover.
The comparison is a general contractor's bar chart, computed with the same code: the work packages start in a fixed order, each trade goes to the first company that can start, and every material arrives two weeks before its work.
What the plan shows
| KPI | Optimized plan | Comparison: general contractor's bar chart |
|---|---|---|
| construction time (weeks) | 26.7 −3.4 | 30.1 |
| handover | 2027-09-03 | 2027-09-27 |
| tower crane on site (days) | 63 −32 | 95 |
| scaffold on site (days) | 57 −49 | 106 |
| idle site days | 26 −25 | 51 |
| material waiting on site (days) | 4 −206 | 210 |
| storage over capacity (m²·days) | 0 −206 | 206 |
| cost of the schedule | 257,100 € −10,100 | 267,200 € |
Decisions
- company per trade, for all its work packages
- start of every work package, including holding one back on purpose
- delivery day of every material, counted in working days before its work starts
Constraints
- order of the work with curing and drying times for concrete, plaster and screed
- company calendars: other sites, company holidays, one crew per company at a time
- at most 3 trades inside the house at the same time
- no concrete, masonry or render on frost days
- earliest delivery dates and the delivery weekdays of the suppliers
- storage area of 45 m²
Objective
early handover, short crane and scaffold rental, few idle days on the site, material that arrives shortly before it is used, low cost
Questions
Why does the plan choose a shell builder with a higher day rate?
Shell builder A is cheaper per day but has another site from late April to mid May. Shell builder B starts one week later and works faster with a larger crew. The shell is finished about two weeks earlier, so the crane leaves earlier and the following trades can start.
Why do most deliveries come on the day the work starts?
Material that waits two weeks takes space, can be stolen or damaged and has to be moved again. In the comparison the storage area of 45 m² is not enough for several weeks. The plan only orders earlier where a supplier delivers on fixed weekdays.
What happens when a company cancels or frost comes early?
The schedule is computed again from the current day. Work that is done stays fixed, and the model moves the rest within the same rules.
Can it plan several houses at once?
Yes. The companies then work on several sites, and the model shares their crews between the houses. This is the usual case for builders of detached houses.
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