as-built
A drawing showing how a project was actually built as opposed to how it was intended to be built.
as-built: reality checked against the blueprint
An as-built drawing is a set of construction documents that record what was actually installed on site, rather than what the original design specified. It shows dimensions, materials, locations, and specifications as they exist in the finished work. Where the design intent called for a wall at 12 feet, the as-built shows that it was built at 11 feet 10.5 inches. Where pipe routing was to follow one path, the as-built documents the actual route it took around an obstruction.
As-builts serve as the legal and operational record of the constructed asset. They become the baseline for maintenance, future renovations, and troubleshooting. Mechanical, electrical, plumbing, and structural trades each produce as-built drawings for their work. In building information modeling (BIM) environments, as-builts inform the final model. Architects, engineers, and contractors all reference them when problems arise or when the building must be modified years later.
Why they differ from plans
Field conditions constantly force departures from design. A buried utility discovered during excavation requires a foundation adjustment. A supplier delivers equipment 2 inches wider than specified. A structural member must be relocated to clear a ductwork run. These changes happen daily on construction sites. The contractor is responsible for measuring and documenting each deviation, ideally as work progresses rather than in a rushed final effort.
Accuracy matters because poor as-builts create liability and operational chaos. A mechanical contractor who records ductwork routing incorrectly will cause headaches when HVAC repairs or replacements are needed. Electrical as-builts with wrong circuit assignments create fire risk and code violations. Structural steel marked incorrectly on as-builts complicates future additions or safety assessments.
Creating as-builts requires discipline: field measurements taken with proper tools, photographs of conditions before concealment (especially for hidden utilities), and coordination among trades to prevent conflicting records. Many contractors now use laser scanning and photogrammetry to capture precise geometry, reducing manual measurement errors and producing as-builts faster than traditional methods allowed.