As Built Documentation: Definition, Meaning and Usecases

Introduction

The basic definition of as-built documentation can be derived from its name with relative ease – it is a set of documents (either a drawing or a 3D data set) showcasing the building in question exactly how it was built. As-built documentation includes all of the current dimensions of the project’s results, from the facade to various doors, windows, cables, pipes, and more. It should also include every change made during construction without planning beforehand.

There is one main reason as-built documentation needs to exist in the first place, and it is self-explanatory. The issue here is that there is always a difference between the original project’s intent and the finished product since these projects are so massive in scale and complex. Many issues could lead to this problem – from scheduling problems and budget changes to unpredictable happenings that affect the construction process in one way or another.

Surprisingly enough, even some of the more recent changes to the building process, including VDC and BIM, are not capable of always producing buildings that are completely identical to their digital counterparts created at the design stage of a project. This turns as built documentation into a necessity, and there are also other reasons for it to exist.

Who exactly needs as built documentation?

But first, we will go over who exactly needs as built documentation in the first place. Several different groups have the need for as built documentation to exist:

• Facility managers and/or owners – they have to have the entirety of a building’s history at hand to be able to perform maintenance and other necessary operational tasks after the construction process is finished.
• General contractors – their goal is to prove that they have performed the construction task to its full extent, and up-to-date recordings of a building’s current state are a great way to showcase this kind of information.
• Other companies tasked with servicing said building in the foreseeable future – a good example of that would be contractors that need exact schematics and measurements of the entire structure to calculate and perform renovations properly.

The issue of accuracy in as built documentation

As built documentation requires an unprecedented amount of accuracy to showcase the exact specifics of an existing building. As such, the services of laser-scanning professionals and laser-scanning software are used to make these measurements as accurate as possible.

Using laser scanning as a whole is a relatively new approach to this process since as built documentation used to rely a lot on manual red-lining for existing 2D drawings to generate this kind of documentation. Since it was a manual process that relied a lot on manual marking for every difference between the plan and the final product, it left a lot of room for human error with a rather noticeable lack of accuracy in some cases.

Laser scanning served as a great solution for these situations, not only offering 3D plans of existing structures but also making them extremely accurate and far less prone to mistakes compared with manual marking in the context of as-built check.

As built deliverables and how they are changing

As built documentation used to rely a lot on 2D CAD drawings for quite a whole. This was the most common form of as built documentation for a lot of years, but now BIM methods are spreading far and wide in the industry as a whole – creating centralized, comprehensive 3D models and using them instead of a multitude of individual drawings and thus generating more pressure for as built documentation to also move towards 3D models. The creation of government mandates in different countries also considerably boosts these kinds of transitions, generating even more demand for accurate 3D as built documentation.

It is also worth mentioning that the transition to 3D as built documentation with the addition of BIM created a bit of confusion typical for many topics involving BIM. The biggest misconception here is that there is no difference between BIM models and CAD drawings because they are both 3D models at their core.

The answer to this misconception is identical to how this works for the BIM industry as a whole – with the BIM model always being much more useful and filled with information about each part of a building, be it the installation date, the model number, and many other parameters. This creates a lot of demand for as built documentation software to be able to produce “as-is” models that are as detailed as regular BIM ones.

Luckily enough, BIM has its solution to this problem called “scan-to-BIM,” which is a technology that uses 3D laser scanning to generate an accurate representation of an existing building and merge it with the data from the existing BIM model, creating an updated BIM model that works as both a general source of information about the project and an as built documentation.

The process of generating a modern as built documentation

Contrary to popular belief, creating as-built documentation includes several different methods of scanning a building in question. The process may differ depending on the specific technology and the hardware, but the general idea remains mostly the same. As such, we can go over four different steps for generating as built documentation:

1. The first step is to survey the construction site with little to no technology involved. This step is to determine control points that will be used later on. Control points are used to ensure that different building levels fit together, creating a unified georeference for the entire structure.
2. Control points surveillance. This is where the first initial scan of control points is performed, generating an overview of the structure, and providing a reference for any future measurements – since it would be impossible to match measurements from different time frames if the locations that are measuring the structure are not the exact same.
3. Construction site surveillance with cameras and lasers. Exactly what the name implies, this is where the main “scanning” process is performed with cameras, lasers, or both.
4. Data processing. Cameras and lasers generate a lot of data that later needs to be compiled into a single comprehensive model – this is where as built documentation software usually comes in, creating a point cloud model that is cleaned up, processed, compressed, and available for viewing for necessary parties.

The benefits of as built documentation

The main benefit of as built documentation is rather obvious – to have a digital 3D representation of what an actual building is like. However, we can also note a few more benefits that come to mind when working with as built documentation software:

• Compliance verification – the existence of two different models (the planned one and the as built one) makes it easier to compare the two, verifying various compliance regulations and updating documentation whenever necessary.
• Defect management – the addition of BIM validation software to the mix allows for proper IFC data management for every information exchange, generating successful quality reports that prove your model’s competence.
• Detection of issues – the implementation of highly accurate laser scanning for as built model creation allows for all kinds of issues and errors to be noticed even if they are not visible to the naked eye, offering a great way to avoid long-running issues that would be harder to fix later.
• Quality management – as a result of a previous advantage, the overall quality of a building grows higher due to many issues being fixed at their earliest stages.

Conclusion

As built documentation is an essential part of any construction process, providing a digital representation of the final product that can be used in several ways – including maintenance, renovation, and so on. The introduction of both BIM and laser measuring into the industry made the process of creating an as built model that much easier, with the ability to speed up the overall measurement process, make fewer mistakes when measuring, and also attaching all kinds of BIM data to each part of the final result.