Redlines and as-builts serve different purposes in the construction documentation process. Understanding the distinction prevents miscommunication and ensures you get the documentation you need.
Redlines (Markup Drawings)
Redlines are annotations — typically in red ink — marked directly on the original design drawings during construction. They show changes, deviations, and field modifications that occurred during the building process.
Who creates them: Contractors, subcontractors, and field engineers When: During construction, as changes happen Format: Marked-up copies of original design drawings (paper or PDF with annotations) Purpose: Record of what changed from the original design
Common redline entries:
- Relocated walls, doors, or windows
- Modified pipe or duct routing
- Changed equipment locations
- Added or removed structural elements
- Field-adjusted dimensions
As-Built Drawings
As-built drawings are the final, clean documentation showing the building as it was actually constructed. They incorporate all redline changes into a revised, professional drawing set.
Who creates them: The design team (architect/engineer) or a documentation specialist When: After construction is complete (or at substantial completion) Format: Clean CAD or BIM files (DWG, RVT) reflecting actual conditions Purpose: Permanent record of the built facility
Key Differences
| Aspect | Redlines | As-Builts |
|---|---|---|
| Format | Marked-up originals | Clean, revised drawings |
| Creator | Field personnel | Design professionals |
| Timing | During construction | After construction |
| Accuracy | Approximate (hand-drawn notes) | Precise (measured) |
| Legal status | Supporting documentation | Official record |
| Usability | Difficult to interpret | Ready for FM/operations |
The Problem with Redlines Alone
Redlines are often incomplete, illegible, or contradictory. Multiple subcontractors may redline the same drawing differently. Without converting redlines into clean as-built drawings, future renovation teams face:
- Ambiguous field conditions
- Incorrect assumptions about hidden systems
- Costly discovery during demolition
- Change orders when actual conditions differ from assumed
How 3D Scanning Replaces Both
3D laser scanning captures actual existing conditions directly — bypassing both the redline and traditional as-built process. Instead of relying on a contractor's hand-drawn annotations, scanning measures the building as it actually exists with ±2-4mm accuracy.
This is especially valuable for:
- Buildings where redlines were never properly converted to as-builts
- Older buildings with no documentation at all
- Facilities that have undergone multiple renovations without updated drawings
THE FUTURE 3D provides 3D laser scanning for as-built documentation at $0.20-$0.70/sqft. Contact us for a free project estimate.