Construction

4D and 5D BIM: time and cost from the model

The programme linked to the objects and the quantities taken from the model: 4D construction simulation and 5D cost control.

At a glance

B1P Group's 4D and 5D BIM links the construction model to the programme (4D) and to the bill of quantities (5D): construction phases are simulated and compared with actual progress, the quantities for estimating, procurement and works accounting come from the model objects, variations are quantified before they are carried out and interim valuations are checked on the model. For contractors, works supervision teams and clients.

Definition

What are 4D and 5D?

4D adds time to the model: each object or group of objects is linked to an activity in the programme, so construction is simulated as a visible sequence and planned progress is compared with actual progress. 5D adds cost: the object quantities feed the bill of quantities, procurement and works accounting, and physical progress becomes financial progress.

The value lies not in the animation but in consistency: the same quantity is used for the estimate, the purchase order and the interim valuation, and the same date is used by the site manager and by the works supervision team.

Deliverables: Model with phases and work packages, 4D simulation, link to the programme, quantities by bill item, physical and financial progress dashboard, planned versus actual comparison, quantification of variations
Standards: UNI 11337-4 (LOD E for construction), exchange information requirements and BIM execution plan, UNI 11337-1 for model uses, works accounting practice
Tools: Navisworks for 4D and quantities, Autodesk Forma for the site and progress, Revit for the models, link to the contractor's programming and estimating software, in-house automation for the dashboards

4D and 5D BIM

How is the 4D simulation built?

The model is split into work packages and phases consistent with the programme (by floor, by zone, by system); each group of objects is linked to its activity; the simulation shows the site day by day and reveals impossible sequences, spaces taken up by two trades at once, machinery that cannot get through. The comparison with actual progress is made by updating the actual dates on the objects.

4D works if the programme has a level of detail compatible with the model: too fine and it cannot be maintained; too coarse and it tells you nothing. We calibrate it with the contractor at the start.

4D and 5D BIM

How are quantities and costs obtained from the model?

Each model object carries its quantity in the appropriate unit (area, volume, length, number) and a code that links it to the bill item. Quantities are extracted by item, by work package and by phase, and compared with the contract bill of quantities: differences show up before ordering, not at the final account.

Financial progress follows physical progress: when an object is marked as built, its quantity goes into the interim valuation. The dashboard shows progress by item, by work package and by period, and serves both the contractor and the works supervision team.

4D and 5D BIM

How are variations managed with 5D?

By modelling them before they are carried out: the variation is drawn in the model, additions and omissions are calculated straight away, and the effect on the programme shows in the simulation. The variation register records who requested each variation, what it is worth and when it was approved.

This is one of the areas where 5D saves the most, because variations are one of the main causes of disputes on site and the model makes them measurable for both parties.

Comparison

What changes compared with the traditional method?

Traditional time and cost management compared with management on the model, item by item.

Activity	Traditional method	With 4D and 5D
Quantities	Measured by hand from drawings, recalculated at every revision	Extracted from the model, updated with each revision
Programme	Bar chart separate from the design	Linked to the objects, simulated and compared with actual progress
Progress	Recorded on site and copied into spreadsheets	Recorded on the objects, physical and financial dashboard
Variations	Estimated after the work is done, often disputed	Modelled and quantified beforehand, with a register
Interim valuations	Reconstructed from the accounts	Extracted from the model with the contract quantities

Related services

What does it combine with?

Frequently asked questions

Frequently asked questions about 4D and 5D

Do I need special software for 4D?

We use Navisworks for the simulation and Autodesk Forma for progress, but the programme stays in the contractor's own software: the link is made through activity codes. We do not ask you to change your planning tools.

Do the model quantities match the bill of quantities?

They match when the model is at construction level and the codes are aligned with the bill items; on the first deliveries we compare the model quantities with the traditional bill of quantities and document the differences, which are often errors in the bill.

Does 5D replace the quantity surveyor?

No: the quantity surveyor remains responsible for the items and the rates; the model gives them reliable, up-to-date quantities. We work with the contractor's technical office, not in its place.

How much does it cost to set up 4D and 5D?

It depends on the level of the starting model and on the detail of the programme and the bill of quantities. Our quote separates the initial set-up from the periodic updates, so the contractor knows what it is paying for over the duration of the works.

Contact

Want to read time and cost from the model?

Send us the model, programme and bill of quantities: we will reply with the method, the deliverables and the price.

Request a meeting B1P Group's BIM consultancy