As-Built DrawingsIntroduction
In the world of commercial renovation and adaptive reuse, you cannot design the future if you don’t accurately understand the present. Traditional methods of gathering existing conditions—involving a junior architect, a tape measure, and a clipboard—are slow, dangerous, and notoriously inaccurate.
When multi-million dollar renovations are based on flawed “as-built” drawings, the result is catastrophic field clashes, structural surprises, and massive budget overruns. Today, the industry standard relies on 3D laser scanning (Scan-to-BIM). In this guide, we break down the modern workflow for capturing field data and generating millimeter-accurate As-Built drawings in CAD and Revit.
Key Takeaways
Key Takeaways
Problem Statement: The Cost of Assuming
Architects often base their renovation designs on the original 1980s blueprints provided by the building owner. This is the biggest mistake in adaptive reuse.
During the original construction, the contractor likely shifted a column a few inches, moved a plumbing stack, or changed a ceiling height. Over the next 40 years, unrecorded tenant improvements altered the space further. If the architect designs a new, high-end commercial kitchen based on those 1980s blueprints, they will inevitably discover during demolition that a massive structural column sits exactly where the new pizza oven was planned.
The only solution is a hyper-accurate, verifiable As-Built model.
The Step-by-Step Scan-to-BIM Workflow
Generating accurate As-Built drawings involves three distinct phases: Capture, Processing, and Modeling.
Phase 1: The Field Capture (Scanning)
- Site Assessment: A technician walks the site to identify scanning locations, ensuring all lines of sight are covered (including above drop ceilings and inside mechanical rooms).
- Laser Scanning: Utilizing a terrestrial LiDAR scanner (e.g., Leica, Faro, or Trimble), the technician captures 360-degree scans. The scanner fires millions of laser pulses per second, measuring the exact distance to every surface.
- Targeting: The technician uses reflective targets to help “stitch” the individual scans together later.
Phase 2: Registration and Processing
- Registration: Back in the office, software (like Autodesk ReCap) is used to align all the individual scans into a single, cohesive 3D Point Cloud.
- Cleaning: The technician cleans the point cloud, removing “noise” like walking people, cars, or temporary construction debris.
- Export: The cleaned point cloud is exported into an indexed format (.RCP or .RCS) that can be imported into drafting software.
Phase 3: The Modeling and Drafting Process (The Core BIM Solutions Workflow)
This is where the massive data file is turned into usable architectural documents.
- Import & Setup: The .RCP point cloud is linked into a blank Revit or AutoCAD template. The drafter establishes the primary levels (floor heights) and orthogonal grids.
- Tracing the Point Cloud: The drafter cuts horizontal “slices” (plan views) through the point cloud and traces the exact locations of the existing walls, columns, and windows.
- Modeling the Deviations: In reality, walls are never perfectly straight, and floors are never perfectly flat. The drafter models these real-world deviations based on the requested LOD (e.g., showing a wall that leans 2 inches out of plumb).
- MEP Extraction: If requested, the drafter models the existing exposed ductwork, plumbing lines, and electrical conduits based on the point cloud data.
- 2D Generation: Once the 3D Revit model is complete, the drafter extracts clean, traditional 2D floor plans, reflected ceiling plans, and elevations.
Comparison Table: Traditional vs. Scan-to-BIM As-Builts
| Feature / Metric | Traditional (Tape Measure & Disto) | Scan-to-BIM (Point Cloud) |
|---|---|---|
| Accuracy | +/- 1 to 3 inches (Human Error High) | +/- 1 to 3 millimeters |
| Speed in the Field | Very slow (Days to Weeks) | Extremely fast (Hours to Days) |
| Comprehensiveness | Only captures what you remember to measure. | Captures everything in the line of sight. |
| Safety | High risk (requires ladders, lifts, walking active sites). | Low risk (scanner does the work from the ground). |
| Cost | High labor cost, high risk of rework. | Higher upfront tech cost, massive savings on rework. |
ROI Analysis: The Value of Perfect As-Builts
Scenario: A 20,000 sq ft historic building being converted into luxury lofts.
- The Cost of Traditional As-Builts: $5,000 for a junior architect to spend a week measuring, plus $4,000 for drafting. (Total: $9,000). During framing, the contractor discovers the entire east wall leans 4 inches, throwing off all the custom millwork dimensions. The millwork must be remade. Total Cost of Error: $35,000+.
- The Cost of Scan-to-BIM: $12,000 for a professional scanning and Revit modeling package from Core BIM Solutions. The model perfectly captures the leaning wall, and the millwork is designed correctly the first time. Total Savings: $32,000 and weeks of schedule delays.
Best Practices for Point Cloud Modeling
- Don’t Over-Model: A point cloud is perfectly accurate, meaning it captures every dent in the drywall. You must establish a tolerance threshold (e.g., “model walls orthogonal unless the deviation exceeds 1 inch”). Otherwise, the Revit model becomes impossibly jagged and heavy.
- Use View Ranges Effectively: When tracing a point cloud in Revit, use a very tight View Range (e.g., cutting at 4’-0“ with a bottom at 3’-11“) to isolate the wall profile and ignore the furniture clutter.
- Deliver Both Formats: Always deliver the final 2D PDF plans and the federated 3D Navisworks/Revit model so the contractor has the visual context of the point cloud.
FAQs: As-Built Drawings
Q: Can you convert my old 2D PDF blueprints into a 3D As-Built model? A: Yes. If a laser scan is not possible, we can build a 3D Revit model directly from your legacy 2D CAD files or scanned PDF blueprints.
Q: How large are point cloud files? A: Very large. A typical commercial building scan can easily exceed 50GB. This is why many firms outsource the modeling phase—they don’t want to dedicate their internal servers and workstations to processing massive raw scan data.
Q: Do you provide the laser scanning on-site? A: Core BIM Solutions specializes in the processing and modeling of the data. You can hire a local surveyor to perform the scan (which is highly cost-effective), send us the raw Point Cloud, and we will build the Revit model.
Conclusion
Basing a modern renovation on outdated blueprints or hand-measured sketches is an unacceptable risk. The Scan-to-BIM workflow provides absolute certainty, transforming real-world chaos into millimeter-accurate digital twins.
By outsourcing the labor-intensive point cloud modeling phase, architectural firms can focus their resources on designing the renovation, confident that the underlying foundation is perfectly accurate.
Call to Action
Stop guessing at existing conditions. Send us your Point Cloud data or legacy blueprints. Contact Core BIM Solutions today for a quote on our highly accurate Scan-to-BIM and As-Built modeling services.
