A schedule can make sense one line at a time and still not work as an erection plan.

The crane move blocks the delivery route. Welding loses access. Two crews are planned for the same area. A sequence advances before the structure or the follow-up work is ready.

4D puts the schedule against the model so the team can see those problems before labor, equipment and material are committed in the field.

If the schedule is the time-phased expression of the erection operation, 4D puts it against the model and asks: can this operation actually work?

4D validationPut scope and time in the same place

The combined view turns the erection plan into something the team can pressure-test.

Test the operation.

Connecting scheduled activities to model scope shows what the plan means physically.

A useful 4D review should help the team determine:

  • Can the structure be erected in the proposed order?
  • Can the crane reach the work from each planned location?
  • Can deliveries, shakeout and follow-up work happen without losing access?
  • Does the sequence provide the required stability and allow the work to be released on schedule?

The purpose is to expose problems while the plan can still be changed.

The team can adjust the sequence, timing, resources, access plan or operating method and test the plan again before those changes become expensive in the field.

Start with the work packages.

The first test does not need to simulate every individual piece.

If the project has eight erection sequences, connect those work packages to the schedule and play the plan through the building. This is usually enough to review erection direction, crane locations, delivery access, overlapping work fronts and major crew handoffs.

See the sample plan in motion

The example below connects eight erection sequences to their schedule, planned man-hours, tons and picks. Open the interactive plan to move through the timeline, rotate the building and explore the sequence data.

Blue decks are erected, orange marks the raising gang, and transparent decks are still ahead. This simplified example shows planned steel erection progress; it does not track the follow-up operations discussed below.
Explore the interactive erection plan →Download the GIF

Each sequence can then move through the production cycle:

  1. Not started
  2. Erected
  3. Plumbed and bolted
  4. Welded
  5. Decked
  6. Punched
  7. Released

This makes work in progress visible. If the raising gang continues advancing while welding remains several sequences behind, the model shows where unfinished work is accumulating.

Use the same connection to make 5D practical.

Once work begins, the model can carry into production control.

One approach is to switch between two views of the building. A sequence view could match each work package to a row in the production table, connecting its location to pieces, tons, planned picks, man-hours and crane days.

A status view could recolor the steel based on where it sits in the operation: delivered, erected, plumbed and bolted, welded, decked, punched or released. Work that has not started could remain transparent or lightly shaded.

The table could shift with the model to show claimed progress, earned man-hours and actual man-hours for each sequence and operation.

If a large portion of the building is shown as erected but relatively little has advanced through welding or release, the team has a visible place to begin looking for what is holding the work up.

This does not require embedding every dollar in every model object. The model shows where the work stands. The table shows what has been completed, what that progress has earned and what it has cost in labor.

4D asks if the plan can work. Practical 5D connects what we can see to what we have earned and spent.

Interactive · Model, schedule and earned progress

See the work. Claim the completed scope.

Select a sequence in the model or schedule. Use the planned view to follow the baseline, then switch to actual status to accept completion gates and compare earned labor with hours spent. Changes are for exploration and are not saved.

Drag to rotate · scroll to zoom · click steel to select

Baseline schedule · working days

Sequence 4
Sequence budget
All five operations · MH
Earned hours
Actual hours
Eight-sequence sample · schematic geometry · illustrative budgets and follow-on timing. Erection durations use picks by work class and one raising gang. Follow-on bars show assumed timing, without checking crew capacity, access, crane reach or stability.

Add detail where it changes a decision.

Some conditions require more development. A crane move may need to be modeled by day or shift. A critical lift may require individual pieces, rigging and crane configurations. A transfer condition may need to show temporary works and the exact installation order.

Other parts of the project may be adequately represented by a sequence changing from one production state to another.

The appropriate level of detail depends on the question. Add detail when it helps the team compare alternatives, identify a conflict or make a decision.

For a quick geometry example, try the Luffer Envelope exercise: change the boom, jib and crane position to see which roof picks become reachable.

The software is not the method.

The schedule may be built in P6, Microsoft Project, Excel or another planning system. The model may come from Revit, Tekla or another platform. Navisworks, SYNCHRO, CM Builder and other tools can connect model objects to scheduled activities and help the team review the erection sequence.

The software will not correct poorly defined scope, arbitrary durations or sequence boundaries that do not reflect how the work will be performed.

The value comes from understanding the field operation, defining the work clearly and knowing what needs to be tested. The model should support those decisions without becoming the center of the process.

Once the plan has been tested and visual status is connected to the production table, the next step is to compare planned production with earned progress and actual man-hours, then adjust while the work is still moving.