What is the difference between as-built drawings and existing conditions documentation?

As-built drawings and record drawings are based on field markups made at the time of original construction, updated only when someone documents a subsequent change. Existing conditions documentation, produced through methods like 3D Laser Scanning, measures a space directly at the time of capture, independent of what any prior drawing recorded.

How accurate is laser scanning compared to traditional as-built surveys?

Laser scanning is typically capable of millimeter-level accuracy, with the specific tolerance depending on the equipment, range, and registration process used. The U.S. Institute of Building Documentation's Level of Accuracy framework defines these tolerances at a stated confidence level so project teams can specify the accuracy a project requires. Traditional manual surveys measure a limited number of discrete points, while a scan captures the entire visible surface of a space.

Do I need existing conditions documentation for a permit application?

Requirements vary by jurisdiction and project type. Many permitting authorities and historic district review boards expect documented existing conditions as part of a renovation or alteration application, particularly for buildings with a significant renovation history or historic designation. Confirming requirements with the local permitting authority early in project scoping typically avoids delays later in the review process.

What is the difference between Level of Accuracy (LOA) and Level of Development (LOD)?

LOA describes how closely captured data matches physical reality, typically expressed in millimeters. LOD describes how much information and geometric detail a model element contains. The two are independent of each other, so a project scope should specify both rather than assuming one implies the other.

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BIM Coordination

As-Built Drawings: Why Engineers Design Better From Verified Reality Than Old Drawings

August 18, 2026

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As-Built Drawings: Why Engineers Design Better From Verified Reality Than Old Drawings

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