BIM as Built: Meaning, How It’s Created, and Its Purpose

To manage a project after its completion, it is essential to have the corresponding BIM “as built” model updated and detailed regarding every modification handled during the construction phase.

Let’s see precisely what a BIM as built model is used for, who is responsible for updating it, which BIM software to use, and who it is useful for.

What is a BIM as built model?

A BIM as built model is the faithful digital representation of the current state of a building or infrastructure at the time of its delivery or at a later appropriately recorded moment. Unlike a design model (which describes how the work should be constructed), the as built documents how the work has actually been carried out, including variations, changes on site, technical adjustments, and execution tolerances.

The as built model integrates geometry, informational attributes, and, when necessary, scanning or surveying data (point clouds, georeferenced photography) to ensure that the digital replica corresponds to the physical artifact. It is a fundamental tool for operational management (facility management), scheduled maintenance, compliance assessment, and for any future renovation or expansion interventions.

The key features of an as built model are:

• spatial accuracy: correspondence between actual positions and dimensions and those represented;
• informational completeness: metadata on elements (materials, finishes, codes, installation dates, manufacturers, manuals);
• traceability of changes: history of variations compared to the initial project;
• management orientation: data structure designed for maintenance and operational use, not just for construction.

From the existing building to the BIM as built model

How it differs from the BIM design model

The BIM design model is a tool for ideation, coordination, and simulation: it usually contains architectural choices, proposed technical solutions, and informative assets useful for performing analyses (structural, energy, interference). The as built, on the other hand, is created (or updated) after execution and reflects the physical reality.

Main practical and methodological differences:

• purpose: the design model supports design and construction, the as built supports management, maintenance, and certification of the actual state;
• data sources: the project is based on design choices and theoretical data, the as built incorporates field surveys, testing reports, and actual measurements (e.g., laser scanner surveys, direct measurements);
• level of detail (LOD): the project often uses increasing LOD during the design phases, the as built requires LOD and LOI (Level of Information) that make the element fully usable for maintenance and management (e.g., codes, life cycles, references to spare parts);
• accuracy and tolerances: the as built documents actual tolerances and any construction deviations, while the project uses nominal dimensions.
• revision management: the as built model must integrate and maintain the history of the variations made on site and the technical or economic reasons that motivated them.

In organizational terms, the transition from project to as built requires clear procedures: identification of as built deliverables, survey methods, responsibilities for updating the model, and quality controls (QA/QC). Without these processes, the so-called “as built model” risks being a simple copy of the project and therefore of little use for the actual management of the work. Furthermore, to develop the BIM model, in addition to the survey, it is essential to use a 3D building design BIM software.

We also recommend reading the article “From point cloud to BIM model ” to get a complete idea of all the steps to follow.

What information does an as built model contain?

An as-built model should include comprehensive information that not only describes the geometry but also captures the behavior, maintenance requirements, and identity of the construction elements. The following are the key informational categories:

• identifying data: unique codes of the elements (asset ID), numbering of rooms, references to site drawings;
• technical properties: materials, thicknesses, thermal/acoustic performance, load-bearing capacity, material class, reference standards;
• supply and installation data: manufacturer, model, serial number, installation date, technical documentation and certificates of conformity;
• maintenance information: recommended maintenance cycles, spare parts, deadlines, user manuals and technical data sheets, links to maintenance contracts;
• survey data: references to point clouds, georeferenced as built photos, measurement reports, and maps of deviations between project and actual;
• change history: design and operational notes explaining the variations introduced on site, signed and dated;
• regulatory and safety information: certifications, CE markings, data for compliance verification, and updated safety plans;
• FM metadata: historical cost of the element, estimated remaining useful life, contractual responsibility for maintenance.

The informational structure must be consistent with corporate standards and, if required, with client specifications (e.g., IFC for interoperability, COBie for data delivery to the facility manager).

Important: not all information is needed in every context. The content and level of information must be defined upstream through the EIR (Exchange Information Requirements).

Section of a point cloud created with Edificius

How to create an as-built BIM model

The creation of an as built BIM model is a structured process that combines field surveys, site information management, and controlled updates of the digital model. It is not just a simple final modeling activity, but a true phase of the life cycle of the work, requiring method, appropriate tools, and well-defined responsibilities.

The process can start from an existing project BIM model or, in the case of already constructed buildings or those lacking reliable digital documentation, from surveying and reconstruction from scratch. In both cases, the goal is to obtain a model that accurately represents the actual state of the work, both geometrically and informationally.

The geometric survey of the existing building

The first step in creating a reliable as built model is the geometric survey of the building or infrastructure. The choice of survey methodology depends on the complexity of the project, the level of accuracy required, and the purposes of the model.

The most commonly used techniques include:

• 3D laser scanner survey: allows for the acquisition of high-density point clouds, essential for representing complex geometries, existing systems, and actual deformations;
• terrestrial or drone photogrammetry: useful for facades, roofs, and difficult-to-access contexts, often integrated with laser scanning;
• traditional direct survey: still used for punctual checks, detailed measurements, or in small-scale contexts.

The result of the survey is not yet a BIM model, but an objective metric base on which to build the as built model. It is essential that the survey data is correctly georeferenced, organized, and validated, as any errors at this stage will reflect throughout the subsequent process.

Updating the project BIM model

When a project BIM model exists, the realization of the as built mainly occurs through its systematic updating. In this case, the design model becomes the starting point, but it must be verified and modified to reflect what has actually been built.

Typical activities include:

• verification of the dimensions and positions of elements against the surveys;
• updating of materials, stratigraphies, and components actually installed;
• insertion of unforeseen variants during construction;
• removal of designed elements that were not realized.

This process requires continuous comparison between the model, surveys, and site documentation (minutes, executive drawings, supply orders, certifications). The update must not only be geometric but, above all, informational: an as built model that does not contain reliable data on the installed elements loses much of its operational value.

It is good practice to define clear rules on who is responsible for updating the model and at what stages, avoiding the as built being hastily prepared only at the end of the work.

Reverse engineering in the BIM process

BIM reverse engineering comes into play especially when there is no reliable project model or when the building was constructed without structured digital processes. In this scenario, the as built model is built directly from the survey data.

The reverse engineering process involves:

• interpretation of point clouds and visual information;
• reconstruction of building and plant elements according to BIM logic;
• progressive attribution of technical and maintenance information.

Unlike updating an existing model, reverse engineering requires greater technical expertise and interpretative ability, as the modeler must translate raw geometric data into intelligent and coherent BIM objects.

This approach is particularly widespread in renovation projects, existing heritage, and advanced facility management interventions. If correctly set up, reverse engineering allows for the creation of high-quality as built models, usable as a digital base for long-term management of the work.

Point clouds and BIM as built modeling

Point clouds represent the direct digital translation of the built environment and constitute the basis on which informative three-dimensional modeling is developed. In the as built context, the point cloud is not a conclusive result, but a support tool that guides modeling choices and allows for verification of the correspondence between model and reality.

The correct use of point clouds reduces the risk of approximations, allows for the detection of geometric deviations, and makes the final model more reliable for subsequent uses, such as technical management of the work or the design of interventions on the existing structure.

I recommend reading the in-depth article “How to implement a “Scan to BIM” process: the GEOSLAM case study” for more details on the topic.

Techniques for acquiring geometry

The geometry necessary for creating point clouds is acquired through advanced survey technologies, selected based on the characteristics of the building and the objectives of the as built model. The most widely used methodologies today allow for continuous detection of surfaces, volumes, and construction details, even in complex or difficult-to-access contexts.

The acquisition phase requires careful planning, as the quality of the collected data directly affects the reliability of the final model. Incomplete coverage, inaccurate registration, or poor resolution of the survey can generate interpretative ambiguities that only emerge during BIM modeling. For this reason, geometry acquisition must be considered an integral part of the BIM as built process and not just a simple preliminary activity.

From survey to 3D modeling

The transition from point cloud to BIM as built model represents a critical phase, in which the metric data is interpreted and transformed into parametric objects with constructive meaning. The point cloud provides a continuous representation of reality, but it is up to the modeler to select, simplify, and structure the information in a way that is coherent with BIM logic.

At this stage, it is essential to maintain a balance between geometric fidelity and functionality of the model. The goal is not to reproduce every irregularity of the built environment, but to create a representation that is sufficiently accurate and at the same time usable for the operational purposes of the as built model. Continuous comparison between the survey and the model allows for the control of actual tolerances and ensures that modeling choices are conscious and justified.

BIM software for creating as built models

BIM as built modeling based on point clouds requires software tools capable of managing large amounts of data and supporting smooth interaction between surveying and modeling. The BIM software for reading point clouds used in this context must allow for effective reading of the point cloud and offer tools that facilitate the construction of the model directly on the surveyed data.

In the as built workflow, BIM software is often complemented by applications dedicated to processing the survey, creating an integrated environment where the geometric data is progressively transformed into structured information. The choice of platforms should not be guided solely by technical functionalities but also by their ability to ensure interoperability, informational continuity, and consistency with the management and usage objectives of the model over time.

Who is responsible for creating the BIM as built model?

In the construction sector, there is a distinct division of roles and responsibilities for each figure involved.

Usually, the designers responsible for drafting the project models also have the responsibility of creating the BIM as built model at the end of the work.

However, it should be noted that designers are not always updated on all changes made on site, and consequently, it is the contractor who bears the burden of updating the final drawings.

Regardless of who drafts the as built models, the most effective way to ensure that everything is documented is to update the project model through regular revisions as construction progresses. This is certainly the most time-consuming and costly method but ensures a high degree of detail in the final model.

The professional fee for as built models represents about 1-2% of the total construction budget.

Keeping track of all changes and recording every modification ensures a reliable final result. Conversely, the inability to document changes during the construction process can lead to final models that are inaccurate and inconsistent with the completed works.

Who benefits from the as built model?

The BIM model is undoubtedly essential during the management phase of the work. In fact, in the event of maintenance or renovation interventions over time, having the updated model of the artifact helps designers, facility managers, and contractors to carry out the work efficiently, limiting errors, interferences, and modifications during the process, thus saving time.

The time savings also translate into cost savings for the client.

In summary, we could say that the BIM as built model is useful for:

• contractors;
• owners;
• professionals;
• facility managers;
• buyers (in the case of sale of the asset).

Useful tools for managing and maintaining an as built model

Managing a BIM as built model does not just mean preserving it as a digital document, but keeping it updated and easily usable for all activities related to the life of the building. For this purpose, tools capable of centralizing information, tracking changes, and supporting operational decisions are essential.

The BIM platforms for managing as built allow for associating technical data, maintenance histories, technical documentation, certifications, and material information to each element. This approach provides a complete and immediate view of the actual state of the building and allows for more effective planning of maintenance interventions.

Other important tools include applications for revision control and change tracking, which ensure the correspondence between the digital model and the built environment over time. Integration with facility management software allows for monitoring consumption, scheduling preventive maintenance, and coordinating operational activities, making the as built model a living and updated tool, useful not only for technical management but also for optimizing costs and resources in the long term.

I remind you that to create the BIM as built model you can use a design software BIM, while to manage it throughout the useful life of the artifact, you can use a BIM management system that is free and completely online.

FAQ about BIM as built

What is an as built BIM model?

An as built BIM model is the faithful digital representation of the actual state of a building or infrastructure at the time of its delivery or at a later appropriately surveyed moment. Unlike a project model, the as built documents how the work has actually been carried out, including variations, changes on site, technical adaptations, and execution tolerances.

How does the BIM as built model differ from the project BIM model?

The project BIM model is a tool for ideation and simulation, while the BIM as built model supports the management, maintenance, and certification of the actual state of the work. The as built incorporates field surveys, testing reports, and actual measurements, while the project is based on design choices and theoretical data.

What information does an as built BIM model contain?

An as built BIM model must contain identifying data (such as unique codes for elements and numbering of rooms), technical properties (materials, thermal/acoustic performance), supply and installation data (such as manufacturer, serial number), maintenance information, survey data, the history of changes, regulatory and safety information, and metadata for Facility Management (FM).

How is an as built BIM model created?

The creation of an as built BIM model involves a geometric survey of the building, which may include the use of 3D laser scanners, photogrammetry, or traditional surveys. The survey data is then used to update the project BIM model or, in the absence of an existing model, to create a new model through reverse engineering techniques.

Who is responsible for creating an as built BIM model?

In the construction sector, designers responsible for drafting project models generally have the responsibility of creating the as built BIM model. However, it is often the contractor who must update the final drawings, as they may be more informed about changes on site.

Who benefits from an as built BIM model?

The BIM as built model is useful for contractors, owners, professionals, facility managers, and buyers, especially in the case of maintenance or renovation interventions. It helps to carry out work efficiently, limiting errors and saving time and money.

What tools are necessary to manage and maintain as built BIM models?

Managing an as-built BIM model requires tools that centralize information, track changes, and support informed operational decisions. BIM platforms enable the integration of technical data, maintenance histories, documentation, certifications, and material specifications, streamlining the management of the building throughout its entire lifecycle.

You might also be interested in “What is HBIM“