An as-built survey records the actual positions and dimensions of a building after construction is complete, capturing deviations from the design that inevitably occur during the building process. These records serve multiple purposes: contractual handover, facility management, and a reliable base for any future renovation or extension work.

What an as-built survey captures

The survey documents the final state of all major structural and architectural elements:

  • Column positions and floor-to-floor heights
  • Slab edges, openings, and finished floor levels on each storey
  • External wall lines and setback distances from boundaries
  • Roof levels, parapet heights, and slope directions
  • Underground utilities, including invert levels of manholes and pipe directions
  • Access roads, parking layouts, and landscape features

The goal is to produce a complete, dimensioned record that reflects what was built, not what was designed. Differences between the two are noted but not edited out of the as-built drawing.

Why as-built records matter

During construction, minor adjustments are common. A column may shift 30 millimetres to avoid a utility clash, a slab opening may widen for a larger duct, or a finished floor level may change to accommodate a thicker screed. These changes are individually minor but collectively significant. Without an as-built record, the next professional to work on the building, whether for maintenance, tenancy fit-out, or structural extension, starts from drawings that no longer match reality.

For clients who engaged a surveying office throughout the construction phase, the as-built survey is a natural final deliverable that closes the project documentation.

Survey methods for as-built work

Total station internal survey

For interior spaces, the surveyor uses a total station to measure column centres, wall faces, door openings, and floor levels. Reflectorless measurement allows shooting to surfaces without placing a prism, which speeds up work in finished spaces where furniture or finishes are already in place.

GNSS for external features

Outdoor elements, boundary walls, access roads, landscaping, and external utility runs, are efficiently captured with GNSS RTK. The surveyor walks the site, collecting points at every change in geometry. Combined with the internal survey, this produces a complete picture of the property.

Drone survey for roofs and facades

For tall or complex roofs, drone photogrammetry captures geometry that is difficult or unsafe to measure from the ground. The resulting model shows roof slopes, parapet profiles, and mechanical equipment positions with centimetre-level accuracy.

Deliverables

A complete as-built package typically includes:

  • Plan drawings at each floor level with coordinates and dimensions
  • Elevation drawings of each facade
  • Cross-sections through the building at key locations
  • A schedule of deviations from the original design, with measured values
  • A digital point file in a format the client can import into CAD or BIM software
  • Photographs keyed to the drawing for context

The drawings should carry a title block that records the date of the survey, the coordinate system used, the datum reference, and the surveyor's name. This metadata ensures the records remain usable decades later.

Timing the as-built survey

The ideal time is after all structural and finishing works are complete but before the building is fully occupied and furnished. Once furniture, partitions, and stored goods fill the space, measuring wall positions and floor levels becomes difficult. If the project schedule requires early occupation of some floors, survey those floors first and complete the remaining areas as they become available.

For projects managed through a general contracting arrangement, the as-built survey should be included in the handover checklist to ensure it is budgeted and scheduled alongside other completion activities.

Common oversights

  • Omitting underground utilities, which are invisible after backfilling and impossible to survey later without excavation
  • Recording only plan positions and neglecting vertical data, particularly finished floor levels and ceiling heights
  • Delivering the as-built in a proprietary format that the client cannot open without specific software
  • Failing to document the coordinate system, leaving future users unable to relate the survey to national mapping or neighbouring projects

Building a long-term asset record

An as-built survey is not just a contractual requirement; it is the foundation of the building's information record for its entire lifespan. Investing in a thorough survey at handover saves far more than its cost when the first renovation project begins. To learn more about what a surveying office delivers and how to evaluate the service, read our detailed guide to choosing a surveying partner.