Most existing buildings do not accurately reflect the drawings prepared for them. Their drawings may be obsolete; modifications to the building may have gone undocumented; walls may be out of plumb; or hidden ceiling services may be unrecorded. Therefore, when design teams begin work assuming the building matches the drawings, they often discover how much the drawings differ from reality, and it is too late to make changes at a reasonable cost.
Point cloud to BIM service is a solution to the problem, as it creates an editable as-built BIM model based on laser scanning of site conditions. Point clouds record many millions of measured data points. Revit models organize interpreted geometric elements (walls, floors, openings, structural components) and project information. However, moving from a point cloud to a Revit model requires judgment and not simply tracing.
McLine Studios offers BIM modeling assistance to architects, engineers, and contractors. They provide point cloud to Revit conversion services for existing buildings. This article outlines the complete scan-to-BIM for existing buildings workflow: data assessment, registration review, Revit setup, modeling, quality checks, and delivery. Also, this article will help clients determine what they need to decide upon prior to the start of a project.
What Is Point Cloud to BIM, and Why Do Existing Buildings Need It?
Point cloud data versus an intelligent Revit model
A point cloud represents the positions of objects relative to each other as measured using a 3D laser scanner, etc., at the time of the measurement. However, a point cloud cannot identify the object type (i.e., wall, pipe, stack of boxes). All of these items will be represented by points.
A Revit model contains modeled elements: walls, floors, columns, doors, windows, and specified building systems, each with a category, type, and parameters. Our Point Cloud to BIM Services cover this point cloud to BIM conversion, in which captured conditions are interpreted into a structured model that design teams can edit, schedule, and coordinate. A point cloud alone does not give you that. It is a reference, not a working BIM model.
When does an existing building need scan-to-BIM?
Scan to BIM is typically the best option for projects where the present condition of the site will influence the final design decisions. Some examples of these types of projects are:
- Renovation planning and interior upgrades.
- Commercial fit-outs in older buildings.
- Building extensions that must tie into existing structures.
- Adaptive reuse of buildings with changed purposes.
- Facility upgrades and retrofit coordination.
- Documentation of buildings with missing or unreliable drawings.
An existing conditions model provides a common baseline for each project. Through the Revit Modeling Services, existing building BIM modeling converts measured data into organized and modifiable components. As a result, architects and engineers can create designs based on accurate physical measurements rather than previous estimates.
The Point Cloud to BIM Workflow: From Scan Data to Revit
The point cloud to BIM workflow consists of 5 stages, each with its own set of questions. The questions are: what occurs at this stage; what can go wrong; what does the client need to verify; and what is produced by the stage. Here is the brief description of these five stages.
Stage 1: Define the modeling scope and intended use
Before production, the group determines the project’s objective, discipline area(s), level of detail needed, the expected deliverable(s), and how it will be used in future steps. At this point, if the project is not clearly defined, it results in a majority of rework later.
Stage 2: Review and prepare the point cloud
The supplied scanned images were processed to determine their overall quality, the extent of coverage provided by each image, and point cloud registration. The output of this scan data processing was a clearer understanding of what could be successfully modeled with confidence, and what was too poorly defined or incomplete.
Stage 3: Link the scan into Revit
The point cloud is formatted to be used within Autodesk Revit. Then, it will be brought into Revit and placed at the correct location (with levels, grids, and coordinate system) in order for the model to sit correctly with respect to the survey and other discipline models.
Stage 4: Model building elements
Revit modeling from point cloud involves converting scan references into Native Revit Objects based on the agreed-upon scope and Level of Development. Your goal should be to produce a useful model, not just a representation of all the points that can be seen.
Stage 5: Validate and deliver the model
The as-built Revit model created from scanning data is then evaluated against the source data. At this point, any known limitations of the as-built Revit model are noted. All of the required deliverables have been completed. Finally, the files are made available to the client so that they may utilize them in their subsequent phases of the project.
How to Prepare Point Cloud Data Before Revit Modeling
Check scan coverage and missing areas
Scanners will only scan what is visible. For example, if there is a room that is locked, furniture, equipment, or other objects block the view of the scanner; it will not be able to “see” inside that space. Also, the scanner cannot “see” into spaces such as ceiling voids, shafts, or above and behind finishes. Therefore, each of these gaps in the scan creates a limit on how much can be accurately represented in the model. Therefore, it would be best to locate these gaps prior to beginning the process of modeling, as opposed to locating them after the modeling has been completed.
Verify registration and coordinate alignment.
Each scan is registered together to create a registered point cloud. When this process of registering is done poorly, the walls may seem to be double-imaged (or “ghosted”), and the measurement of distances between parts of the building will not always be consistent. Before beginning to produce the model, verify the registration report if possible, and make sure that you know what coordinate system is being used, and if there are other shared coordinate systems.
Review formats, file size, and usability
Scan data usually comes in the form of RCP and RCS files, E57, and LAS. The compatibility and conversion requirements for scan data will be determined by what type of scan data you receive, as well as the software that you use. If the scan data is large enough, then it may have to be broken down into smaller pieces (segments), or indexed in order for it to be accessible within Revit.
Our 3D Scan to Revit Services include translating scan data into Revit-compatible project information, which is easier when the supplied files are well organized.
Separate observed information from assumptions
Visible construction can be identified. However, construction such as wall thickness behind finishes, hidden structural elements, and concealed services must be represented as assumptions rather than scan-verified facts. Point cloud to BIM accuracy will depend upon the quality of the point cloud data being provided and how well defined the limits of that data are.
Modeling the Point Cloud in Revit: What Makes the Model Usable?
Establish levels, grids, and project coordinates
Levels, grids, and coordinate systems provide organization to the Revit model. If these are properly set up, then the project team can accurately associate the Revit model with survey data as well as the models created by other teams working on different aspects of the same project. If these are not properly established, then every subsequent connection to the model will inherit the problems caused by this poor establishment.
Model walls, floors, openings, and structural elements
Modelers will transform the physical representation of the object being modeled into appropriate Revit elements such as wall types, floor slabs, door and window openings, columns, and beams. Modeling decisions should be based on what is going to be used as opposed to trying to model every visible point. During the Revit point cloud modeling process, a renovation design model will require accurate wall locations and openings, rather than every surface irregularity.
Represent irregular and non-standard geometry.
Older structures rarely have perfect geometry. Floors may be tilted, walls curved, ceilings sagging, and there are many instances when a drawing showed a straight line, but the structure was actually built with a curve. Therefore, modelers must determine how to accurately portray such geometric irregularities. Some options include representing them as sloped elements, adjusting the wall geometry to match the irregularity, or including notes regarding tolerances in the model, depending on the needs of the design team.
Model architectural, structural, and MEP information to the agreed scope
Architectural BIM modeling, structural BIM modeling, and MEP BIM modeling all have different implications for scope. For certain types of renovation projects, existing ductwork, piping, and structural components will be critical; however, for many other types of renovation projects, these elements may be irrelevant. When services are concealed, the scope must specify what is being done with them.
Legacy drawings may sometimes be used to enhance the data obtained through scanning. The use of CAD to BIM Services would be applicable in cases where there exists CAD documentation that can serve as an additional reference for creating the model. The process of using CAD documentation as a source of information is an alternative workflow to the use of a point cloud as the primary source of information, but it should never replace the verification of the accuracy of the point cloud.
A convincing-looking model does not mean it will be a usable BIM deliverable. A usable model will use the correct families, appropriate element categories, meaningful parameters, consistently named items, and organized files. If you don’t have these items in your model, you can create a file with the correct shapes; however, you can’t edit, schedule, or coordinate the file.
Choosing the Right LOD and Modeling Scope for an Existing Building
Define the model’s purpose before choosing LOD
The level of detail (LOD) required for a scan to BIM depends upon the intended use of the model. For example, if you are conducting a feasibility study, designing a renovation project, coordinating multiple disciplines, or have specific requirements for construction documentation, you can determine the appropriate level of detail. It is important to remember that LOD (Level of Detail) requirements for scan to BIM should align with your objectives. Typically, when people select their LOD first and then their objective second, they often end up with models that are too basic or models that contain excessive amounts of information.
Match model detail to the project requirements
Not all elements require the same amount of development. For example, architectural walls will likely require a different level of detail than structural members and mechanical, electrical, plumbing (MEP) components. Applying a consistent treatment to all parts of the building would increase costs and file sizes without providing additional value in terms of decision-making.
Specify tolerances and exclusions
The client and provider need to reach an agreement about what constitutes acceptable modeling tolerance, element scope, assumptions, and exclusions. This includes how to address those parts of a project that are either not accessible or cannot be seen. Tolerances need to be defined so both parties understand what each means when they say “accurate.”
An example of a model used for early-stage space planning could require only reliable room boundaries, large wall elements, and major opening components. An MEP coordination model requiring close coordination would require more detail regarding each component of the systems of interest.
The process of defining these choices prior to the start of the project is essential to our Point Cloud to BIM Services. This is because the scope of the model will determine what happens next with the Point Cloud to BIM deliverables.
Quality Control: How to Check a Revit Model Against the Point Cloud
Compare modeled geometry with the scan
Review the location of walls, floor elevation, opening size, structural member location, and other critical elements with respect to the source data. A point cloud deviation analysis will demonstrate which areas of the model depart from the point cloud and the amount of departure. This will allow reviewers to prioritize those elements that are important.
Check coordinates, levels, and model consistency
Search for alignment discrepancies, errors in the height of objects, duplicate features, and inconsistent geometry. Even if a wall is accurately represented in the scan, it is still incorrect if it is located on the wrong level. Additionally, using consistency checks can reveal errors that would be overlooked through visual comparisons alone.
Review the model structure and information
Confirm that all of the elements in the model are categorized correctly, named appropriately, have proper parameters assigned to each element, and that the model is organized in a way that makes sense. Open the file and modify it exactly like the receiving team would. If you cannot adjust the walls in the model or populate your schedule with data from the model, then your model is not ready.
Document discrepancies and limitations
Unresolved gaps, uncertain geometry, and deviations outside acceptable limits should be documented, not hidden behind a model that is presented as being verified. When there is a documented limitation in the model, the design team can then use that documentation to help make a decision. If a limitation in the model is hidden, it will likely cause issues at the jobsite. Good point cloud-to-BIM quality control and BIM quality assurance rely upon the use of Revit model validation like what was described above.
Comparing a model to a point cloud is different from finding conflicts among the various disciplinary models. The focus of our BIM coordination service is to review the interfaces of the disciplines and find out where there are coordination problems. Both activities can be considered quality control processes; however, they provide answers to two distinct questions.
What Should a Point Cloud to BIM Deliverable Include?
Model and supporting files.
Depending on the agreed scope, the package may include:
- Native Revit (.RVT) model.
- Required point cloud reference materials and related documents as specified in the contract.
- IFC or other agreed exchange formats, when required.
- Model setup information, coordinate details, and relevant views or documentation.
- A record of assumptions, exclusions, limitations, and agreed quality checks.
The extent of the point cloud to BIM deliverables depends on what was specified in the project brief and agreed upon as part of the project scope. All of the items listed above are not necessarily standard inclusions.
Define acceptance requirements before handover
Before starting the project, make sure to agree on what file version will be used, how files should be named, which disciplines will be involved, the extent of the model, and the criteria for reviewing the model. Agreeing to these items before work begins allows you to have a clear definition of what is required to accept the Revit model as complete. This helps turn the Revit model delivery process into a simple check-off item rather than a negotiation over whether the model meets the required standards. It also establishes a standard for the completed as-built Revit model to achieve.
Common Point Cloud to BIM Problems and How to Avoid Them
| Common problem | Recommended response |
| Incomplete scan coverage | Identify gaps and agree on additional survey requirements or documented exclusions. |
| Misaligned scan data | Review registration and coordinate alignment before modeling. |
| Unclear LOD requirements | Define the intended use, element scope, and level of detail before production. |
| Overly detailed modeling | Prioritize elements that support the intended design or coordination task. |
| Unusable Revit structure | Agree on families, categories, naming, levels, and model organization. |
| Unclear acceptance criteria | Define quality checks, tolerances, deliverables, and review responsibilities. |
Most scan-to-BIM errors share a root cause: decisions that should have been made before modeling began. The point cloud-to-BIM workflow and quality sections above explain how to address each one, and a clear scope protects existing building documentation from the same problems.
How to Choose a Point Cloud to BIM Partner for an Existing-Building Project
Ask about relevant project experience
The first step should be to look for experience on projects of a similar type of building, similar existing conditions, and the different disciplines in your brief. When you ask for examples of work completed by the company, make sure they are relevant to your project, rather than providing only broad statements about what the company is capable of doing.
Confirm Revit standards and deliverable requirements
The scan-to-BIM provider will explain how they manage project templates, coordinate systems, model organization, file version control, and quality reviews. A scan-to-BIM provider that can clearly explain its processes is more likely to provide you with a usable model for your team.
Evaluate scope clarity and communication
Who is responsible for resolving scan gaps? How will assumptions be documented? How will changes or revisions be managed? And who has the authority to sign off on the final model? These four questions are crucial because they can help avoid potential problems with your team members in the future.
When choosing a specialist, clients will need to look at what they do (scope), how they do it (process), and what they produce (deliverables). This is where Revit Modeling Services and a clear point cloud workflow come together. It doesn’t matter if you do the work in-house or use BIM outsourcing services.
Understand what affects cost and turnaround
Understand the scan quality and the complexity of the building; the scope of the model; the level of development (LOD); the number of disciplines involved; how ready the files are for use; and when you would like your project delivered; all of these items affect each other. Do not make any promises regarding a fixed price or turnaround time before reviewing the scan data and model scope.
McLine Studios is a viable option for architects, engineers, and contractors who wish to review the scope of their projects, the required inputs for their projects, the types of Revit outputs they can expect from their projects, as well as any other modeling requirements that may be unique to their project.
Turn Existing-Building Scan Data into a Usable Revit Model with McLine Studios
To create a useful BIM model, you will need to have accurate scanning data, a well-defined work scope, the correct level of detail in the model, and relevant quality assurance procedures. Your next step in the process can be supported by the correct type of deliverable. Your deliverables should not just be what the building looks like.
McLine Studios has the capability of assisting you with your Point Cloud to BIM Services and other Revit modeling needs, from the initial scan review to an editable as-built BIM model. If you are looking for Point Cloud to Revit conversions, or if you require Revit modeling services, provide us with your project scope, any existing scans, required discipline(s), and intended use of the resulting model(s). We will then be able to determine what would constitute appropriate deliverable(s) for your specific requirements.
If you have an existing building to document or renovate, call McLine Studios to talk about your point cloud data, Revit modeling needs, and what you need delivered.
