Scan to BIM — How We Build an As-Built Revit Model from a Point Cloud

What Is Scan to BIM?

Scan to BIM is the process of using laser scan data as the basis for producing an as-built BIM model of an existing building. Rather than modelling a new design from scratch, the model represents the building as it currently exists — capturing actual wall positions, ceiling heights, structural elements and all existing conditions with millimetre accuracy.

The result is a fully structured Revit model that your design team can use immediately as the basis for refurbishment design, planning applications, engineering coordination or facilities management — without having to survey the building themselves or trust in potentially inaccurate historical drawings.

Why Revit?

At SurveyX we produce all as-built BIM models in Autodesk Revit 2025 — the industry standard for BIM modelling in the UK. Revit is used by the vast majority of architects, structural engineers and M&E consultants working on refurbishment and new-build projects, which means our models integrate seamlessly into the wider project team's workflow.

Revit models can also be exported to IFC format (Industry Foundation Classes) — an open standard that allows the model to be used in any IFC-compatible software including ArchiCAD, Bentley AECOsim and Trimble products. If your design team works in a different application, we can provide the IFC export alongside the native Revit file.

The Complete Workflow — Step by Step

Step 1 — Site Scanning with the Leica BLK360

The workflow starts exactly as described in the scanning article — the BLK360 is set up at multiple positions throughout the building, capturing a dense point cloud of every space. For a scan-to-BIM project we typically capture more scan positions than for a 2D drawing survey, paying particular attention to ceiling geometry, structural details and any MEP (mechanical, electrical, plumbing) elements that need to be modelled.

Step 2 — Processing in Autodesk ReCap

The raw scan files are imported into ReCap, registered and processed as described in the previous article. The registered point cloud is exported as an RCP file, which loads directly into Revit as a reference dataset.

Step 3 — Loading the Point Cloud into Revit

The RCP file is linked into a new Revit project. In Revit, the point cloud appears as a three-dimensional reference dataset overlaid on the model space. It can be sliced at any height or angle, and individual points can be snapped to when placing model elements.

Before modelling begins, the Revit project is set up with the correct grid, levels and coordinate system — matching the coordinate system of the point cloud so that all model elements will be correctly positioned in space.

Step 4 — Setting Up Levels

Levels (the horizontal datums in Revit that define each floor) are set up first, using the point cloud to establish the exact finished floor levels for each storey. These levels form the skeleton of the model and control the height of all elements placed on each floor.

For a typical two-storey house this might involve setting up Ground Floor, First Floor, Second Floor and Roof levels. For a multi-storey commercial building there might be ten or more levels, each precisely positioned from the scan data.

Step 5 — Modelling Walls

Wall modelling is typically the most time-intensive part of the process. Each wall is placed in Revit as a wall family — a parametric element with a defined thickness, height, material and structural properties.

The point cloud slice at each level shows the exact position of every wall face. External walls are modelled first, followed by internal walls and partitions, using the point cloud to set the exact position of each wall within the Revit coordinate system.

Wall thicknesses are taken directly from the scan data — the distance between inner and outer faces is measured from the point cloud and matched to an appropriate Revit wall family.

Step 6 — Modelling Floors and Ceilings

Floors are placed at the established level datums, with the point cloud used to verify the actual floor profile — particularly in older buildings where floors may not be perfectly level. Ceiling heights are taken from vertical section cuts through the point cloud, with Revit ceiling elements placed at the correct heights.

Step 7 — Doors and Windows

Door and window families are placed in the host walls at the positions shown in the point cloud. Opening widths, heights and cill heights are all taken from the scan data. Standard Revit families are used where they match the actual openings — custom families are created for unusual or non-standard elements.

Step 8 — Roof Geometry

Roof modelling uses the point cloud to capture the exact geometry of the roof structure — pitches, ridges, valleys, eaves heights and any dormers or rooflights. Complex roof geometry that would be difficult to measure manually is particularly well-suited to scan-based modelling, as the point cloud captures the complete three-dimensional form of the roof surface.

Step 9 — Structural Elements

Where structural elements are visible — steel columns, beams, exposed concrete structure — these are modelled from the point cloud as structural families. The scan data captures the actual dimensions and positions of structural elements with sufficient accuracy for most design coordination purposes.

Step 10 — 2D Drawing Extraction

One of the key advantages of a Revit model over standalone 2D CAD drawings is that floor plans, elevations and sections can all be extracted directly from the model. Because the model is three-dimensionally consistent, all the drawings automatically agree with each other — a dimension on the plan matches the elevation, which matches the section, which matches the model.

Extracted drawings are set up on standard drawing sheets with the SurveyX title block and issued as PDFs alongside the native Revit file and IFC export.

Level of Detail

BIM models are produced to an agreed Level of Development (LOD) — a standard that defines how much detail is included in the model. For as-built survey models we typically work to:

• LOD 200 — elements modelled as generic shapes with approximate dimensions. Suitable for early-stage design and spatial planning.
• LOD 300 — elements modelled with accurate dimensions, positions and orientations. Suitable for detailed design, planning applications and engineering coordination. This is our most common delivery standard for refurbishment projects.

The appropriate LOD is agreed at the quote stage based on how the model will be used. Higher LOD requires more modelling time and increases the cost — we'll always advise the most appropriate level for your specific project.

What You Receive

• Native Revit model (.RVT) — Revit 2025 format
• IFC export (.IFC) — for use in non-Autodesk applications
• Registered point cloud in RCP and E57 format — for use as a reference dataset
• 2D drawings extracted from the model — floor plans, elevations, sections in DWG and PDF