The Challenge

A leading construction and real estate firm in Kolkata approached Desapex with a critical need As-Built drawings that mirrored on-site realities with millimetre-level precision. These weren’t just routine drawings. They needed to become the blueprint for all upcoming interior and structural planning. In a live construction site where time and accuracy go hand-in-hand, there was zero room for error.

Client’s Initial Hurdles

• The site was already partially constructed, making traditional manual measurements inefficient and error-prone.
• Structural details like lintel beams were difficult to detect visually.
• The deadline was strict just one month for a 3 lakh sq. ft. facility.
• The only input provided was a master plan image in PNG format, with no access to existing CAD or Revit files.

Why This Was Critical

Why were precise as-built drawings necessary?

The client was mid-way through construction. Any mismatch between actual site conditions and drawings could lead to misaligned interiors, service clashes, and rework all of which are costly.

Why not use traditional survey methods?

Traditional methods could not meet the required sub-3mm accuracy or match the speed needed. With parts of the structure already built, access was limited making laser scanning the only viable option.

Why was lintel beam detection a sticking point?

Lintel beams are often partially or fully embedded, and even reality capture has limitations when elements are concealed. Still, the client needed these for structural validation and interior anchoring.

How did the timeline affect decision-making?

The 4-week deadline pushed for simultaneous workflows scanning, registration, modeling, and drawing production all had to overlap to deliver on time.

What risks were at stake for the client?

Without accurate as-builts, the interiors could face clashes, spatial misjudgments, and rework. For a residential builder, this meant delays in handovers and client dissatisfaction.

Gaps in Existing Information

The only input shared was a non-scalable PNG master plan. There were no architectural CAD files, no section drawings, and no detailed structural references. This forced the team to reconstruct the built environment from scratch, relying entirely on laser-scanned point cloud data.

Why Specific Requirements Mattered

• Sub-3mm Accuracy: For load-bearing elements and services, even small deviations could snowball into larger issues during interior execution.
• Lintel Beam Visibility: These are critical for door/window alignment and curtain wall placement.
• Tight Schedule: The client had downstream contractors waiting for the drawings. Delays weren’t just about time they risked stalling the entire project.

The Desapex Solution

• Desapex deployed a laser scanning team on-site, capturing the entire architecture and structural layout of the base build. Using AutoCAD 2021, Autodesk Revit 2021, and Navisworks, our team developed a high-accuracy BIM model.
• Despite the limitation of lintel beam visibility, we devised a cross-verification method using scan registration and visual checks in Bluebeam Revu. We also kept a close feedback loop with the client to prioritize critical areas.

‍Project Timeline & Milestones

• Week 1–2: Full laser scan completed.
• Week 2–3: Scan data registered, and BIM model of architecture + structure developed.
• Week 3–4: As-built drawings produced, reviewed, and delivered.
• Total Area: 3 Lakh Sq. Ft.
• Delivery Timeline: Exactly 1 Month

Software & Technology Used

• AutoCAD 2021
• Autodesk Revit 2021
• Navisworks Manage 2021
• Bluebeam Revu

The Real Business Value Delivered

• Zero compromise on accuracy. The 3mm tolerance was met across key structural elements.
• Faster decision-making for interiors. With clear documentation, the client was able to plan services, MEP, and interior partitions efficiently.
• Digitally structured outputs. Drawings were clean, logically layered, and ready for BIM integration.

What This Means for Future Projects

For the client, this project proved that investing early in digital accuracy saves time and reduces costly rework during the finishing stages. They’re now considering making digital as-builts standard across all large developments.

For Desapex, this engagement reaffirmed the power of combining laser scanning with structured BIM workflows, even when starting with minimal inputs. It also strengthened our on-ground coordination and quick-delivery capabilities, particularly in live construction environments.

This wasn’t just another scan-to-BIM job it was a validation of how digital engineering enables clarity, control, and confidence in construction.