4D/5D BIM
An extension of a [[concept-bim|BIM]] model that links its 3D elements to additional dimensions of project data: 4D ties the model to the project schedule, so a viewer can watch the building assemble in sequence over time; 5D ties it to cost, so quantities in the model connect directly to a live budget.
Why it matters
A traditional schedule or budget lives in a separate document from the model, which means the sequence or cost implications of a design change aren't automatically visible in either one. Linking the model to time and cost data makes the schedule and budget impact of a change visible immediately, in the same place the design change was made.
On a real project
A scheduler links the coordinated model to the project schedule and produces a 4D simulation showing the building assembling floor by floor over the construction timeline, a walkthrough that reveals a sequencing conflict between two crews scheduled to occupy the same area in the same week.
Who this matters most to
A Scheduler uses 4D BIM to visualize and validate a proposed sequence before committing to it, catching space conflicts a written schedule alone wouldn't surface. A Cost Engineer uses the 5D dimension to tie model quantities directly to cost data, keeping the budget synced with the design as it evolves.
Where this goes wrong
A team builds a 4D sequence simulation early in design but never updates it as the schedule changes throughout construction. The simulation drifts further from the actual plan with each revision, until relying on it for real sequencing decisions becomes riskier than not having one at all.