4D BIM Planning: Model, Schedule and Sequence Review
A 4D simulation should help a team review a construction decision. Learn which model and schedule inputs to prepare, what to verify and what to request at handover.
4D BIM links a 3D model with time information from a construction schedule. The result can help a team review phases, work zones and installation sequences. Bentley describes SYNCHRO 4D as connecting the project schedule and model for time-based construction planning. SYNCHRO 4D.
The scope should begin with the decision being evaluated. A milestone presentation, a logistics review and an updated progress comparison need different inputs and checks.
Inputs to prepare
- The current schedule, its revision or data date, activities and milestones.
- Available models, their revisions and relevant disciplines.
- The work breakdown by zone, level, package or installation step.
- The scenarios to compare and the decision criteria.
- Access, logistics and other constraints that must be represented.
- Required outputs, update frequency and review dates.
If the model or schedule is missing, identify its preparation as a separate work item. A polished animation cannot compensate for an undefined activity sequence.
Make model elements match the work
A model may contain one object where construction happens in several stages. Conversely, many objects may belong to one activity. Agree the level of grouping or splitting needed to represent the sequence.
There is no universal LOD number that makes every model ready for 4D. The right representation depends on the decision: broad zone volumes may support an early phasing review, while an installation study may need specific components and access spaces.
A phased-renovation example
Illustrative example: a building must keep one access route open while two zones are refurbished. The team proposes two work sequences.
Represent the zones, the relevant temporary arrangements and the activities that affect the route. Review both scenarios with the people responsible for access and construction planning. Record what the simulation includes and what needs a separate assessment. A visible opening in the animation is not proof that the route satisfies all project requirements.
Review the simulation before presenting it
- 1Check that the schedule and models are the agreed revisions.
- 2Inspect whether included activities have the intended model links.
- 3Identify model elements or activities intentionally left unlinked.
- 4Review a representative sequence with the planning and delivery teams.
- 5Check dates, phase labels and scenario assumptions.
- 6Record decisions, unresolved questions and required updates.
Unlinked activities are not always errors: procurement or other non-geometric work may be outside the visual scope. Their treatment should be deliberate and documented.
What should a 4D service deliver?
Specify whether you need an animation, stills, a schedule-linked editable project, a link register, a review record or ongoing updates. Agree the receiving software and how a future schedule revision will be handled.
An MP4 is useful for communication, but it does not provide the same editing and inspection capabilities as the underlying 4D project. Compare proposals on the actual package.
Keep the model and schedule current together
When an activity changes, inspect the relevant links and sequence. When geometry changes, check whether the previous assignments still make sense. Give one person responsibility for confirming the revision used for the next review.
For progress comparisons, distinguish planned dates from reported actual progress and explain how progress information was collected. Do not present assumed status as observed construction.
Questions before requesting 4D planning
Do we need a detailed model of everything?
No. Define the elements and zones that affect the decision. Model detail should be sufficient for that use and its checks.
Does 4D replace the project schedule?
No. It adds a visual way to inspect and communicate selected schedule relationships. Schedule logic and planning assumptions still require review.
What affects price and timing?
Model preparation, activity count, scenario count, logistics representation and update cycles affect effort. Share those inputs with the 4D scheduling service, and use the proposal checklist to compare scopes.
Let's talk about your project.
Share the intended use, available information and target date. We can help define the scope and deliverables for your BIM or VDC work.
