- Watch out
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- Experienced readers
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- In BIMpedia
Civil engineers design the ground and the networks around and under buildings: earthworks, roads, car parks, drainage, water and power connections, retaining walls. On infrastructure projects (roads, rail, bridges, pipelines) the civil team designs the whole asset. Their models are different from building models in a few ways that matter to a coordinator.
| Building model | Civil model |
|---|---|
| Levels and grids | Alignments, profiles and chainage |
| Local project origin | Real-world coordinates (a national grid or projected system) |
| Tens of metres | Hundreds of metres to kilometres |
| Elements (walls, doors) | Surfaces, corridors, networks |
IFC 4.3 added alignments, roads, rail, bridges and ports, so infrastructure can now be exchanged in open formats too.
Where buildings and civil works meet
- Finished levels at the entrances (the civil engineer's external levels vs the architect's ground floor).
- Drainage and utility connections: where pipes and cables leave or enter the building, at what depth.
- Retaining walls, ramps and steps at the building edge.
- Coordinates: the building's local origin must sit exactly on the civil engineer's real-world grid.
The architect sets the ground floor at +45.20; the civil engineer grades the forecourt to +45.05 using an older survey. Nobody compares the models. On site, the accessible entrance needs a 150 mm step, and a ramp has to be added to the forecourt after the paving is laid.
The coordinator adds an "external interfaces" test to the coordination cycle: entrance levels, drainage connections and utility entries are checked each month against both models, on the same coordinate system. The level difference is found at stage 3 and resolved on paper.
A new school sits on a sloping site with a car park, a bus drop-off and a connection to the public sewer. List five interfaces between the building and civil models you'd check every month.
Key takeaways
- Civil teams design earthworks, roads, drainage, utilities and external works; on infrastructure projects, the asset itself.
- Their work is linear (alignments, chainage) and tied to real-world coordinates, often over kilometres.
- Interfaces with the building (levels at the door, drainage connections, utilities entering the building) are where coordination matters most.
- Tools and formats differ from building BIM; IFC 4.3 now covers roads, rail and bridges.