In the world of BIM modeling, one particular service, which oftentimes gets swept under the rug and given little attention, is the provision of as-built models. In a previous piece, we’ve went over the BIM levels of development and how each one represents a step above its predecessor, with LoD 500 being the peak point of BIM design. This final LoD also coincides with the delivery of as-built drawings or models.
What is an as-built drawing/model?
As-built drawings or models are a revised set of illustrations, which a contractor offers to a client, once a project is completed. These illustrations can be in the form of 2D/3D physical drawings or 3D CAD-based models.
They reflect every single shift in design, specifications, modifications and field changes that occurred over the life span of the construction process. As-built drawings/models contain exact dimension, geometrical and location information about all of the elements that were part of the project.
These drafts are essentially the final set of outlines that you receive once everything is done, and come accompanied by handwritten notes and sketches, explaining each shift in detail.
Example of a 3D BIM as-built model Source : Indiamart.com
Why are as-built drawings/models important?
As-built drawings/models provide three important functions, which derive from one another:
Transparency – given that these illustrations serve as the project’s legacy, owners are able to see all of the critical information they need about any parts or components, from concealed elements, pipe & duct routing, to terminal unit locations and control system sensor locations.
Accountability – since it is easy to find information about the entire array of pieces that went into a construction project, owners can track vendors, producers and contractors, in order to request further information, if needed.
Sustainability – probably the single most important function that these models serve. By having a detailed, 3D drawing/model on hand, owners can easily engage in facilities management operations, whenever needed, either due to maintenance reasons or parts replacement, as a result of attrition.
As-built drawings/models ensure that future renovations are more efficient and timelier, as they offer owners, contractors, architects and designers alike a way to confidently plan expansions, additions, alterations or complete turn-arounds.
The different levels of information and design that go into an as-built model. Source: Rivistageomedia.com
Another reason as to why these illustrations are so important is due to the fact that they contain vital information for Process Safety Management and Process Hazard Analysis. Since they include the highest level of information, as-built models contribute to emergency preparedness, by offering a clear & straightforward portrayal of safety concerns and potential hazards within the building. In addition to this, they can also provide a full list of the necessary equipment, shutdown switches and keys, if the project features such elements.
Moreover, if we take a look at specific individuals that may benefit from these drawings/models, we’ll quickly find out that all of the parties involved benefit greatly from them. Owners may use the information they provide for lease area audits, asset tracking or facility management operations. Architects & engineers employ these models to understand pre-retrofit conditions. Fabricators need precise as-built data to create off-site parts as requested and identify incompatibilities before installation.
How do you obtain as-built drawings/models?
There are two primary methods of obtaining an as-built drawing/model: 2D/3D hand-made physical drafts and 3D BIM models.
When it comes to physical drafts, these can usually come in three forms:
- Plan drawings – a detailed map of the project, which offers an aerial view that showcases different design elements, by cutting through walls. This drawing may depict rooms, walls, windows, fixtures, stairs, furniture and appliances, among others.
- Section drawings – similar to the first type, it offers a glimpse over interior elements, however this time it is from the inside, making it deal for representing floor heights and any unique design choices.
- Exterior drawings – also known as elevation drawings, these portray a building’s exterior design, offering insight on materials, heights, textures, in addition to the space between any of the visible components.
Physical drafts usually employ coloured mark-up lines, to delineate the difference between the initial design and the finished product, giving owners a big picture over all of the changes that have transpired from the first phase, to the last. These can also be converted into 3D information-rich models.
When looking at the more modern, 3D digitized models, these are usually first developed by measuring the existing building, in order to generate the appropriate CAD or BIM documentation. Once that information is accounted for, a model is created, which is then verified via technology such as a Lidar Scanner. The Lidar is a piece of laser-imaging tech that can capture scenes with millimeter accuracy, providing accurate & detailed 3D data at the rate of thousands of points of measurement/second.
The scanner collects information about every construction piece as point clouds, which represent shapes of objects in real space.l. These then get converted into a collection of points, in a 3D digital space.
This form of an as-built model comes with an additional, almost invaluable option that its physical counterpart cannot offer. Through the use of a 3D BIM as-built model, you can also switch off certain elements within the finished 3D design. If you wish to see any pipelines, ducts, cable trays or fixtures that may be behind or under a ceiling or wall, this form of illustration allows it, giving owners unprecedented control over their project.
As we can see, whether we’re interested in 2D physical illustrations or 3D BIM models, as-built drawings represent an almost indispensable feature of today’s construction process.
Whilst a majority of the world still relies on 2D drawings, the reality of the fact is that they become outdated quickly. The world is progressing at a rate at which buildings suffer alterations almost yearly, making such drawings oftentimes redundant and a pain for architects, designers, contractors and owners alike.
Whether you’re interested in pre-emptive clash-detection or future refurbishing, a 3D model will generally enable you to make quicker decisions, since all of the information is shared in a common data environment Furthermore, due to its digital nature, you can navigate models like never before. From turning various elements off and on, to changing shapes, sizes, locations or positions, 3D BIM as-built models offer all of the parties involved a chance at more effective work and fewer bumps at the end of the proverbial road.