4D BIM links model elements to the construction programme, so the sequence of work can be seen and checked over time. 5D BIM links elements to quantities and costs, so the model drives estimates and cost reports. The terms describe uses of the model, not different kinds of model. Higher "dimensions" (6D, 7D) are also used, but their meanings vary between countries and authors.
At a glance
| 4D | 5D | |
|---|---|---|
| Adds | Time: programme activities and dates | Cost: quantities, rates and totals |
| Links | Elements ↔ activities | Elements ↔ cost items |
| Typical tools | Synchro, Navisworks Timeliner, Fuzor, Bexel | CostX, iTWO, Vico, Bexel, spreadsheets from schedules |
| Main users | Planners, contractors, site managers | Cost managers, quantity surveyors, contractors |
| Depends on | A model split the way work is built | A model with reliable quantities and classification |
4D: what it is used for
- Sequence review: watching the building go up shows activities in the wrong order or overlapping in space.
- Logistics: crane positions, laydown areas, access routes and temporary works over time.
- Communication: showing clients, neighbours and site teams what happens when.
- Progress tracking: colouring elements by planned versus actual status.
A 4D model needs elements that match how work is built: a slab modelled as one element for the whole floor cannot show a pour sequence by bay. A location breakdown structure (zones and levels) shared by the model and the programme makes the links far easier.
5D: what it is used for
- Quantity take-off from the model rather than from drawings.
- Cost estimating by applying rates to classified quantities.
- Design option comparisons with cost updated as the model changes.
- Cash flow when 5D is combined with 4D: cost over time.
5D depends on consistent classification (for example Uniclass or UniFormat) and on knowing what the model includes. Items not modelled, such as fixings, preliminaries and finishes below the agreed level of detail, still need traditional measurement.
Common misunderstandings
- "The model gives exact quantities." It gives the quantities of what is modelled, as modelled. Measurement rules and waste factors still apply.
- "4D is an animation." The value is in checking the sequence, not in the video.
- "6D means sustainability, 7D means operations." Usage differs; say what you mean instead of using numbers.
Where to read more
Planning and cost software documentation describes the linking methods. National measurement rules (such as NRM in the UK) govern how quantities are reported.