TL;DR
An as-built survey documents the final constructed position of a building or structure after construction is complete, verifying that it matches (or recording where it deviates from) the approved design. An existing conditions survey records the current state of a structure or site that was built previously—often years or decades ago—with no reference to an original design. The two are frequently confused because both produce a digital record of physical reality, but their purpose, timing, and standards are different. As-built surveys are contract deliverables tied to construction completion. Existing conditions surveys are investigative tools for renovation, retrofit, or design.
Key Takeaways
- An as-built survey is conducted after construction to verify and document what was actually built; an existing conditions survey records the current state of an existing asset with no design comparison
- As-built surveys in Australia should follow AS 5488 and project-specific contractual requirements; existing conditions surveys follow the scope defined by the designer or project manager
- Deliverables differ: as-built surveys include deviation reports comparing as-built to design; existing conditions surveys provide a baseline model or drawing set with no design reference
- As-built surveys are typically the contractor's responsibility under most construction contracts; existing conditions surveys are commissioned by the designer or owner before a new project begins
- Both use similar technology (total stations, laser scanners, photogrammetry), but the processing workflow and deliverable structure are different
Table of Contents
- As-built survey vs existing conditions survey: what's the difference?
- What is an as-built survey?
- What is an existing conditions survey?
- Side-by-side comparison table
- When is an as-built survey required?
- When is an existing conditions survey required?
- Standards and compliance: AS 5488
- Deliverables comparison
- Technology and methods: similar tools, different workflows
- Cost comparison
- Common mistakes and how to avoid them
- Frequently asked questions
- What to do next
What is an as-built survey?
Definition: An as-built survey is a post-construction survey that documents the actual position, dimensions, and geometry of a completed structure or infrastructure element, comparing the as-constructed reality to the approved design. It identifies and quantifies deviations from design and provides a permanent record for asset management, compliance, and future works.
As-built surveys are a standard contractual requirement on construction projects in Australia. Most standard form contracts (AS 4000, AS 2124, and project-specific agreements) include a clause requiring the contractor to provide as-built drawings and surveys before practical completion.
The as-built survey serves several purposes:
- Compliance verification: Confirming that the constructed work meets the design specification and any relevant standards
- Handover documentation: Providing the owner with accurate spatial records of their asset
- Future works planning: Enabling accurate design of renovations, extensions, or maintenance work
- Dispute resolution: Providing an independent, measured record in case of contractual disputes about constructed positions
- Asset registration: Feeding data into asset management systems (e.g., GIS, CMMS, digital twin platforms)
An as-built survey is fundamentally comparative. Its value comes from the comparison between "what was designed" and "what was built."
What is an existing conditions survey?
Definition: An existing conditions survey is a survey of a site, building, or structure that captures its current physical state, including dimensions, geometry, services locations, and structural elements. It is not compared to a design because the original design drawings are typically unavailable, unreliable, or non-existent.
Existing conditions surveys are commissioned before design work begins on renovation, retrofit, or adjacent construction projects. The survey provides the design team with an accurate digital model of what actually exists, rather than relying on outdated or inaccurate drawings.
The existing conditions survey serves several purposes:
- Design baseline: Providing accurate spatial data for architects and engineers to design around existing conditions
- Clash detection: Identifying interferences between proposed new work and existing structures, services, or equipment
- Feasibility assessment: Helping the project team understand spatial constraints before committing to design decisions
- Regulatory compliance: Documenting existing conditions for heritage, environmental, or planning approval processes
- Risk reduction: Reducing the risk of unknown conditions causing cost and programme overruns during construction
An existing conditions survey is fundamentally descriptive. Its value comes from accurately recording "what is there now" so that designers can work from reliable data.
Side-by-side comparison table
| Aspect | As-Built Survey | Existing Conditions Survey |
|---|---|---|
| Timing | After construction is complete | Before new design begins |
| Purpose | Verify and document what was built | Record what currently exists |
| Design comparison | Yes—measured vs design deviation | No—no design to compare against |
| Who commissions | Contractor (usually) or owner | Designer, owner, or project manager |
| Contractual basis | Required by construction contract | Defined by design brief or scope |
| Standards | AS 5488, project specification | Scope-dependent (may reference AS 5488) |
| Deliverable | Deviation report + as-built model/drawings | Model or drawing set of existing conditions |
| Key question answered | "Was it built to design?" | "What is actually there?" |
| Cost basis | Typically % of construction value | Fixed fee or hourly rate |
| Typical accuracy | Matches construction tolerance (5-25 mm) | Matches design needs (5-50 mm) |
When is an as-built survey required?
As-built surveys are required in the following situations:
- Construction contract handover: Under AS 4000 clause 37 and AS 2124 clause 35, the contractor must provide as-built documents before practical completion.
- Council/asset owner requirements: Many councils and infrastructure owners (water authorities, road agencies) mandate as-built surveys for works on their assets.
- Quality assurance: Large projects use as-built surveys as part of independent verification and validation (IV&V) processes.
- Building code compliance: The National Construction Code and state building regulations may require as-built certification for certain building elements.
- Warranty and defects: As-built records establish the baseline condition at handover for warranty and defects liability purposes.
Typical elements captured in an as-built survey:
- Building footprints and floor levels
- Structural element positions (columns, beams, walls)
- Service routes and invert levels (stormwater, sewer, water)
- Road and pavement geometry (centrelines, levels, crossfalls)
- Retaining wall positions and levels
- Utility locations and depths
- Landscaping and surface finishes
When is an existing conditions survey required?
Existing conditions surveys are commissioned in the following situations:
- Renovation or retrofit projects: Before designing alterations to an existing building or structure, the design team needs accurate current data.
- Brownfield expansions: When adding new infrastructure adjacent to or within existing facilities, clash detection requires an accurate 3D model of what exists.
- Heritage and conservation projects: Recording heritage structures before any intervention, to satisfy statutory requirements and conservation principles.
- Due diligence: For property acquisition or leasing, verifying that existing conditions match representations and identifying latent issues.
- Forensic investigation: Following damage, failure, or incident, documenting the state of a structure for engineering analysis.
- Digital twin creation: Creating a digital twin of an existing asset requires a comprehensive existing conditions survey as the geometric foundation.
Typical elements captured in an existing conditions survey:
- Complete building or structure geometry (walls, floors, ceilings, roofs)
- Structural system identification and dimensions
- Mechanical, electrical, and plumbing (MEP) services locations
- Site topography and drainage patterns
- Adjacent structures and their relationship to the subject site
- Underground services (via GPR, EM location, or excavation)
- Access constraints and spatial envelopes
Standards and compliance: AS 5488
AS 5488—Classification of Subsurface Utility Information—is the primary Australian standard referenced in both as-built and existing conditions surveys that involve underground services.
The standard defines four quality levels for subsurface utility information:
| Quality Level | Method | Accuracy | Typical Use |
|---|---|---|---|
| D | Desktop records review | Unknown | Preliminary planning only |
| C | Surface-visible feature survey | +/- 500 mm horizontally | General planning |
| B | Geophysical location (GPR, EM) | +/- 100-300 mm | Design development |
| A | Physical exposure (potholing) | +/- 10-50 mm | Construction and clash-critical design |
For as-built surveys, the construction contract should specify the required quality level for each service type. For existing conditions surveys, the design brief should define the quality level based on the risk of clash or interference.
In addition to AS 5488, as-built surveys on building projects should reference:
- AS 1100: Technical drawing standards
- Project-specific specifications: Often more detailed than standards, specifying tolerances, formats, and delivery requirements
- State survey legislation: In NSW, surveys of works on public land may require authorisation under the Surveying and Spatial Information Act 2002
Deliverables comparison
As-built survey deliverables
| Deliverable | Format | Content |
|---|---|---|
| As-built survey report | Survey methodology, accuracy statement, tolerance verification, deviation summary | |
| Deviation register | Spreadsheet (Excel) | Tabulated list of all measured vs design deviations with tolerances |
| As-built drawings | CAD (DWG/DGN) or PDF | Drawings showing as-built positions, annotated with deviations |
| 3D as-built model | IFC, Revit, or proprietary | 3D model of as-built conditions, colour-coded by deviation |
| Point cloud | E57, LAS, or RCP | Raw scan data for future reference |
| Utility survey report | AS 5488 quality level classification for all services | |
| Certificate of compliance | Signed certification by registered surveyor |
Existing conditions survey deliverables
| Deliverable | Format | Content |
|---|---|---|
| Existing conditions report | Survey methodology, accuracy statement, scope of capture, limitations | |
| Existing conditions drawings | CAD (DWG/DGN) or PDF | Floor plans, sections, elevations, reflected ceiling plans |
| 3D existing conditions model | Revit, IFC, or SketchUp | 3D model suitable for design team use |
| Point cloud | E57, LAS, or RCP | Raw scan data for design team reference |
| Services location drawing | CAD (DWG/DGN) | Traced service routes with quality level notation per AS 5488 |
| Photos and video | JPEG, MP4 | Visual record of conditions, damage, access constraints |
| Topographic survey | CAD (DWG/DGN) | Site levels, contours, drainage, features |
Technology and methods: similar tools, different workflows
Both survey types use the same core technologies, but the workflow and processing differ.
| Technology | As-Built Survey Use | Existing Conditions Survey Use |
|---|---|---|
| Total station | Control survey, discrete point verification of key elements | Control survey, selective dimensional capture |
| Terrestrial laser scanning | Full 3D capture of structure; deviation analysis against design model | Full 3D capture of existing structure; model creation |
| Drone photogrammetry | Large-area site capture, volumetrics | Site topography, roof geometry, surrounding context |
| Drone LiDAR | Earthworks verification, terrain modelling | Vegetated site topography, bare-earth extraction |
| GPR/EM location | Utility verification against design | Utility location and depth for design integration |
| Mobile scanning (SLAM) | Corridor surveys, rapid capture | Indoor building surveys, complex plant environments |
Workflow difference:
- As-built: Field capture → Register scans → Compare to design model → Generate deviation report → Certify compliance
- Existing conditions: Field capture → Register scans → Build 3D model from point cloud → Deliver model to design team
Cost comparison
| Project Type | As-Built Survey Cost | Existing Conditions Survey Cost |
|---|---|---|
| Small building (500 m) | AUD 3,000-6,000 | AUD 4,000-8,000 |
| Medium building (2,000 m) | AUD 8,000-15,000 | AUD 12,000-25,000 |
| Large industrial facility | AUD 25,000-60,000 | AUD 30,000-80,000 |
| Infrastructure (roads, pipelines) | AUD 15,000-40,000/km | AUD 20,000-50,000/km |
Existing conditions surveys for buildings often cost more than as-built surveys because the building geometry is more complex to model when there are no design drawings to reference. Every element must be interpreted and modelled from the point cloud or field measurements.
As-built surveys on simple, repetitive structures (e.g., standard roads, pipelines) can be relatively inexpensive because the comparison to design is automated.
Common mistakes and how to avoid them
| Mistake | Why It Happens | How to Avoid |
|---|---|---|
| Commissioning an existing conditions survey when an as-built is required | Confusing terminology in the design brief | Clearly define the survey purpose: "record what exists" vs "verify what was built" |
| Using outdated design drawings for as-built comparison | Poor document control | Always verify the design revision being used for comparison |
| Not specifying deliverable format | Assuming the surveyor knows what the designer needs | Define CAD format, BIM level of detail, and file formats in the scope |
| Inadequate services location | Relying on records without field verification | Specify AS 5488 quality level B or A for clash-critical services |
| Missing the defects liability period survey | Focus on practical completion only | Schedule a pre-DLP-expiry survey to record condition before handover |
Frequently asked questions
Is an as-built survey the same as a surveyor's certificate?
No. A surveyor's certificate is a formal document signed by a registered surveyor certifying that the survey has been conducted in accordance with relevant standards and that the results are accurate to stated tolerances. An as-built survey is the broader deliverable package that may include a surveyor's certificate.
Who pays for an as-built survey?
Under most Australian construction contracts (AS 4000, AS 2124), the contractor is responsible for providing as-built drawings and surveys as a condition of practical completion. The contractor typically engages the surveyor and includes the cost in their contract price. Existing conditions surveys are usually paid for by the owner or designer as part of the pre-design phase.
Can I use a laser scanner for both types of survey?
Yes. Laser scanning is the dominant technology for both as-built and existing conditions surveys of complex structures. The difference is in the processing: as-built compares the scan to a design model; existing conditions builds a new model from the scan.
What level of detail (LOD) should an as-built BIM model be?
The appropriate LOD depends on the project and the asset management strategy. For general handover, LOD 200-300 is typical. For facilities management integration, LOD 300-350 may be required. Always specify the LOD in the contract or design brief.
How long does an as-built survey take?
A typical as-built survey for a medium commercial building takes 2-5 days of field work plus 3-7 days of office processing. Large industrial facilities may require 1-2 weeks in the field and 2-4 weeks of processing. Existing conditions surveys of complex buildings typically take longer due to the modelling requirement.
What to do next
Getting the terminology right matters because it affects your contract, your budget, and your deliverables.
- Confirm which survey type you need. Are you verifying a recently completed construction project? That is an as-built survey. Are you planning to design work in or around an existing structure? That is an existing conditions survey.
- Check your contract requirements. If you are a contractor, review your construction contract for as-built survey obligations before practical completion. Missing this can delay handover and payment.
- Define your deliverables upfront. Specify the format (CAD, BIM, point cloud), the required accuracy, and the level of detail before engaging a surveyor. This avoids scope creep and disputes.
- Engage early for existing conditions. The existing conditions survey should be complete before design development begins. Late engagement compresses the programme and increases risk.
Call ISS on 0407 057 015 to discuss your project. We will confirm whether you need an as-built survey, an existing conditions survey, or both, and provide a detailed scope and fee proposal matched to your project requirements.