‘As built’ models? I think not…

Let me just begin by stating that this blog post is based entirely upon the current state of the AEC industry and I hope things will adapt quite soon…

As people begin to read more and more into our BIM geometry files, the phrase ‘as built’ becomes more and more of an ‘issue’. Historically, hard copy drawings were ‘physically’ stamped with the phrase to denote that the particular building element was constructed in that way.

What happens next is nothing new, but between the static form of an architect / engineer / designer’s drawing we introduce ‘humans’ again. There is (and never has been) any guarantee that what was contained within the drawing actually translated to site during construction.

Forgive me for simplifying things, but in past years this wasn’t critical to anyone’s future use; now however, we face the prospect of our models being actively used and evolving through the life of the building (quite how, we don’t know yet, but more on that in a later post). Even through the design process, we use the model for analytical design and feedback – the translation onto site becomes more pertinent.

We have an opportunity now, to set a process whereby our design and construction information is more closely aligned with what is constructed. BIM enables us to easily (yes, I said that) transfer much more (quantity), accurate (quality) information to describe our design intent. This can then be used by a contractor as a basis for construction; in BIM utopia, this would then be gradually replaced with sub-contractor designed elements, manufacturer components and take on board last minute client changes – we all know they happen!


We still cannot guarantee (yet) that what is modelled, will be constructed or installed in accordance with the model, so where do we go?

The answer lies in technology and point cloud survey deliverables… or does it?

The relatively recent affordability and flexibility of laser surveys has allowed their use throughout the construction process rather than just a large initial investment in an existing building survey. We should promote their use at key stages for recording ‘actual’ as built locations of building elements. These scans can then be overlaid (or loaded as required) into a master model, giving an ‘as built’ record of what’s lies behind walls, within risers, below ground etc.

All done then? Well no, I’m afraid not. All this does is provide a snapshot in time and relies upon a fastidious contractor to scan, scan and re-scan when changes are made during construction. Even if that succeeds, it’s still only a snapshot of what was ‘built’ on a set date and at handover.

So I’ve come full circle… we’re still only able to issue ‘Last Construction Issue’ models which will be supplemented by recorded data of what was built.

The only other way I see this developing is through the use of X-ray type scanning… Does anyone know if at even exists commercially yet?



4 responses to “‘As built’ models? I think not…

  1. Yep there is such a beast. X-Ray but for forensic uses only. eg determining steels encased in concrete for old buildings where you can take thing apart. At a cool $7K/day. However, X-Rays are difficult to use. The “as built” is bridged by two techniques. GDM and GME. Again the techniques come from other industries and enforce the construction to letter. Fairly easy to implement and control too.

  2. You make a good point. Could it be that the components themselves (from the steel beams to ductwork runs to electrical conduit) become ‘smarter’ over time, with embedded sensors, such that they can report their installed position and possibly functional performance? In essense, this would mean that the building itself could report its ‘as-built’ condition?

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