Technological transitions in design and construction do not occur abruptly, or at least should not.

Ideally, one model should be developed gradually, with more details to help plan and manage a structure during its construction and after it has been built.

The as-built plans are a final and accurate representation of how a construction has been carried out, incorporating the modifications and changes made during the execution of the project. In recent years, the BIM (Building Information Modeling) methodology has gained popularity for its ability to create detailed digital models that can be updated and maintained in real time, being very effective for generating as-built plans. However, there are other technologies that also allow the creation of this type of documents, such as traditional CAD (Computer Aided Design), 3D laser scanning and photogrammetry systems.

As-built plans in construction: BIM and its superiority over other documentation technologies

1. BIM (Building Information Modeling)

BIM is a methodology that allows the creation of intelligent digital models containing not only the geometry of the project, but also information associated with materials, costs and construction times. One of the main advantages of this system in creating as-built plans is its ability to update the model in real time as construction is carried out. Changes are automatically documented, and the resulting model accurately reflects the final state of the work.

Advantages of BIM for as-built plans:

• Real-time update: As construction teams make changes, they can be integrated directly into the BIM model.
• Coordination and precision: By integrating different disciplines (architecture, structural engineering, installations), as-built plans are much more precise and reflect the real interaction between the various building systems.
• Complete information: In addition to the geometry, the model contains detailed material information, which facilitates maintenance and future interventions.
• Ease of use later: BIM as-built models are easily usable for future remodeling, maintenance or extensions thanks to their rich data structure.

2. Traditional CAD (2D and 3D)

CAD has long been the standard tool for construction design. However, when it comes to the creation of as-built plans, the process is more manual and error prone compared to BIM.

Disadvantages of CAD versus BIM:

• Manual process: In traditional CAD, changes made during construction must be hand-drawn and then integrated into the drawings. This results in a margin of error and omission of details.
• Lack of integration: CAD drawings do not allow for smooth integration between different disciplines, which may lead to inconsistencies between the drawings of different specialties (structures, electricity, plumbing, etc.).
• Limited data: Unlike BIM, CAD only provides the graphical representation of elements, without information associated with materials or costs.

Advantages of DAC:

• Simplicity: For small or less complex projects, CAD remains a viable option due to its simplicity of use and faster learning curve compared to BIM.

3.- 3D laser scanning

3D laser scanners capture millions of points in space and generate a point cloud that can be used to create a three-dimensional model of an existing structure. This technology is very useful for the creation of as-built plans of already built projects or in situations where a digital model is not available.

Technical comparison with BIM:

• Accuracy: 3D laser scans offer high precision when capturing existing geometry, but lack the ability to integrate additional information such as materials, costs or relationships between different disciplines.
• Post-processing: Unlike BIM, laser scanning requires significant follow-up work to convert the point cloud into a usable CAD or BIM model, which can be costly and time consuming.
• Not in real time: While BIM can be continuously updated during the construction process, laser scanning is usually done once the project is almost finished.

4.- Photogrammetry

Photogrammetry uses photographs taken from different angles to generate 3D models using point correlation algorithms. This technology has been popular in the restoration of historic buildings and projects where it is difficult to use other capture tools.

Advantages and disadvantages of BIM:

• Affordable cost: Photogrammetry is cheaper than laser scanning, but it does not offer the same level of accuracy. This makes it useful in projects where you are looking for a rough representation rather than millimetric details.
• Less technical details: Like laser scanning, photogrammetry models do not contain detailed information beyond the captured geometry. This makes them less useful for as-built plans that require full technical information.