Quoting a renovation BIM project on new-build modelling-hour benchmarks is one of the more common and costly estimation errors in Indian BIM services, and it traces to genuinely structural differences in the workflow, not simply extra caution applied to a similar underlying task.
| Project type | Typical modelling time relative to new-build baseline | Primary time driver |
|---|---|---|
| New-build | Baseline (1x) | Modelling from clean design intent, no existing-condition uncertainty |
| Renovation/retrofit (scan-to-BIM based) | 2x to 3x | Point cloud processing, existing-condition verification, and resolving discrepancies between as-built reality and any available original drawings |
Where the Extra Time Genuinely Goes on a Renovation Project
Point cloud registration and cleanup alone can consume a considerable share of total project time before any actual BIM modelling even begins - a step that simply has no equivalent in new-build work, where modelling proceeds directly from clean design intent without needing to first process a physical survey of existing conditions. Existing buildings also routinely deviate from their original drawings, whether through undocumented modifications made over years of use or genuine as-built variance from the original design intent, and reconciling the model against physical reality requires iterative verification that new-build modelling, working from a clean design brief, never has to do.
A Scenario Showing Why Occupied-Building Renovation Adds Yet Another Layer
Picture a renovation BIM project inside a partially occupied hospital wing, where the design team needs to model both the existing conditions and the proposed new work while the building continues functioning around them. This adds complications new-build modelling simply doesn't face - capture and site access needs to be scheduled around ongoing operations, certain areas may only be accessible for limited windows of time, and the sequencing of both modelling and eventual construction needs to account for maintaining operational continuity throughout. This kind of occupied-building complication compounds on top of the baseline renovation time premium already shown in the table, which is why renovation projects inside active facilities often run toward the higher end of that 2x to 3x range rather than the lower end.
Why the LOD Premium and Renovation Premium Compound Rather Than Simply Adding
A renovation project modelled to LOD 400 for a specific fabrication-critical package experiences both the renovation-specific time premium and the LOD 400 premium simultaneously, and these two effects compound rather than simply summing - a genuinely accurate cost estimate for a renovation project needing LOD 400 detail on any package needs to account for both factors together, not apply either one in isolation to what would otherwise look like a standard new-build estimate.