An as built model records a building's observed condition rather than relying only on design intent. To create one from laser scans in Revit, define the survey scope, register the scans, prepare an indexed RCP/RCS point cloud, link it at verified coordinates, author existing elements, and check the result against measured evidence.
A BIM as built model is useful for renovations and facility planning because it contains editable objects, not just millions of measured points. But scanning cannot reveal concealed construction, and a neat model does not guarantee accuracy. The workflow below explains what to measure, what to model, and what evidence the owner should receive.
What is an as built model in BIM?
An as built model is a digital representation of existing or completed construction, based on field observation and other verified records. Unlike a point cloud, an as-built BIM model contains identifiable walls, floors, openings, equipment, and other modeled objects. Its stated accuracy and information completeness apply only to the agreed scope and survey date.
| Stage | Main action | Deliverable |
|---|---|---|
| Scope | Define elements, accuracy, and use | Survey brief |
| Capture | Scan accessible surfaces | Raw scans |
| Register | Align scans and check control | Registered point cloud |
| Prepare | Index supported scans in ReCap | RCP/RCS package |
| Model | Author existing objects in Revit | Editable RVT |
| Validate | Check positions, geometry, and attributes | QA and exception record |
| Handover | Package approved files and limitations | Owner deliverables |
A usable as-built BIM deliverable requires both modeled objects and evidence showing how their geometry was verified.
How does an as-built BIM model differ from design BIM?
A design model shows what was intended to be built; an as-built version records what can be substantiated about the actual building. Moved doors, altered slab elevations, and rerouted services belong in the latter when supported by evidence. Renaming a design model as built does not verify its contents.
What can laser scanning actually verify?
Laser scanning captures visible surfaces from accessible viewpoints. It can establish exposed column faces, opening positions, and accessible service runs, subject to survey uncertainty. It cannot directly identify concealed reinforcement, wall composition, or pipe contents. Document those properties from approved records where available, or explicitly mark them unverified.
How should you plan an as-built survey for Revit?
Plan an as-built survey around the elements and decisions the final Revit model must support. Define which rooms, disciplines, and interfaces require measurement before selecting scanner positions. Include control measurements and access constraints. More scan points cannot compensate for missing rooms, unsuitable registration, or poorly defined acceptance criteria. If the work is outsourced, a shortlist of the best scan to BIM services in US shows how providers split field capture from Revit production.
Which LOD, LOA, and information requirements matter?
Specify element development using the project's LOD convention, geometric accuracy separately, and the attributes needed for the intended use. BIMForum's LOD 500 describes observed existing conditions, not a guaranteed survey tolerance. State required identifiers, parameters, measurable tolerances, and exclusions for each relevant element category.
How should scanning and registration be checked?
Capture overlapping scans from stations that reveal floors, openings, ceilings, and exposed services. Register the scans, review station-to-station fit, and compare independent survey checkpoints where required. Record occlusions, moving objects, and reflective surfaces. A low registration residual does not, by itself, prove correct site coordinates or full coverage.
How do you prepare and link point clouds in Revit?
Prepare supported raw scans in ReCap, index them as RCP/RCS, and link the result through Revit's Insert > Point Cloud command. An RCP project normally references indexed RCS data. Preserve those dependencies and verify the placement against surveyed benchmarks. Choosing a positioning option is not independent proof of alignment.
How do you convert E57 into an RCP/RCS package?
Import the E57 into ReCap, confirm available scan poses and coordinate settings, and review whether the scans already share a registered frame. Complete any required registration, then index and save the project. Reopen the RCP with its supporting RCS files to confirm that the cloud, location, and attributes remain usable.
How do you place scans and set building levels?
Use Insert > Point Cloud in Revit and choose a placement method that matches the verified survey setup. Check known horizontal and elevation references before modeling. Establish levels from measured slabs in sections, then isolate working regions with section boxes and visibility settings. Center to Center placement is not survey verification.
How do you create native Revit elements from scans?
Create native Revit elements by interpreting the point cloud in plans, sections, and isolated 3D views. Establish levels and grids before tracing walls, columns, floors, openings, and scoped services. Revit can support snapping to recognized points or planes, but modeling decisions and geometry checks still require professional review.
How should architectural and structural geometry be modeled?
Fit walls and slabs to measured surfaces within the agreed tolerance, then place appropriate native families for openings and structural components. Distinguish irregular existing geometry from modeling noise. A leaning wall may require documented deviation rather than automatic straightening. Check both faces and centerlines where the specification calls for them. Model-derived sheets should agree with any as built architectural drawings issued for the same areas.
How should MEP and concealed elements be handled?
Model exposed ducts, pipe routes, cable trays, and equipment only where coverage and contract scope support them. Use the project's Existing phase for retained building elements as appropriate. Do not infer hidden service routes from nearby points alone. Label reconstructed or record-based geometry separately from field-verified components.
A focused Revit modeling sequence is:
- Check levels, grids, and the cloud's reference coordinates.
- Isolate one floor or element with a section box.
- Place native walls, floors, columns, and opening families.
- Author visible MEP routes using approved family types.
- Assign the appropriate project phase and source attributes.
- Review geometric differences before moving to the next zone.
How do you verify an as-built model's accuracy?
Verify the as-built model by comparing authored geometry with registered scans and, where required, independent survey control. Check critical wall faces, openings, elevations, and equipment interfaces against specified tolerances. Report directional deviations, coverage gaps, and exceptions rather than relying on a pleasing 3D appearance or an average residual alone.
| QA category | Evidence to review | Acceptance question |
|---|---|---|
| Survey control | Independent checkpoint differences | Is the cloud correctly positioned? |
| Architecture | Wall faces, door sizes, slab elevations | Are critical dimensions within tolerance? |
| Structure | Column locations and visible interfaces | Are relevant elements represented accurately? |
| MEP | Exposed routes and equipment positions | Are modeled systems supported by observations? |
| Asset data | Identifiers, sources, missing fields | Are unverified attributes flagged? |
Check geometry and information quality independently; a model can pass one test and fail the other.
What should an as-built model handover include?
An as-built model handover should include the reviewed native model, agreed exchanges such as IFC, coordinate definitions, supporting point clouds, and an exceptions register. Add the survey date, quality report, and required asset schedules. Recipients must know what was measured, what came from records, and what remains uncertain.
An RVT file is not automatically a complete facility asset register. Confirm linked scan paths, IFC properties, project phases, and model versions before issuing the package. If the owner also needs 2D sheets, the steps differ; see how to create as built drawings.
What mistakes undermine scan-to-Revit as-built modeling?
Common mistakes include treating the point cloud as editable BIM, assuming dense scans prove accuracy, ignoring survey coordinates, and copying unverified design dimensions. Missing RCS dependencies can also break references after transfer. Reduce these risks by testing file links, recording assumptions, and validating critical elements before the model is accepted.
How should missing evidence and inferred geometry be documented?
Document missing evidence with an element-level status, location, reason, and proposed verification action. A ceiling void may be inaccessible, or an existing pipe route may only appear on legacy drawings. Keep such information distinguishable from surveyed geometry so future designers do not treat an inference as a field measurement.
Frequently asked questions about as-built models
As-built models support renovation, coordination, and building operations, but their reliability depends on accessible survey evidence and the contract's information requirements. Revit models are authored from measurements rather than created automatically by indexing points. The following questions address automation and whether a high LOD or dense scan is sufficient proof of accuracy.
Can Revit automatically generate a verified as-built model?
No. Revit can display indexed scans and assist with point or planar snapping, but it does not automatically verify and author every building element from raw laser data. Modelers must interpret visible geometry, choose families, define parameters, and complete quality checks before the output can be considered an accepted as-built deliverable.
Does LOD 500 or a dense point cloud guarantee accuracy?
No. LOD 500 indicates existing or field-verified condition modeling within its defined context, not an automatic geometric tolerance. Dense points may still be misregistered or incomplete. Specify measurable accuracy requirements, then test both survey data and modeled elements against appropriate references. Keep the results with the deliverable.
