With the implementation of BIM into the construction industry changing the way buildings are designed and built, Quantity surveyors are also starting to review traditional methods and further streamline their roles in the construction process. These are indeed exciting times ahead for the Quantity surveyor as many new functions and abilities of a QS are being discovered.
When BIM was first played around by Architects and Engineers, many other buildings professionals such as quantity surveyors and construction managers did not know where BIM would fit into a project life cycle. Initially, quantity surveyors were not able to exploit what BIM had to offer because the designers had not even been able to accurately model a building, hence there was no value in taking quantities off an imprecise model. It was not until half a decade down the track when the methodology in practicing BIM had been perfected by designers, did quantity surveyors see a spark of innovation in terms of what they could offer.
The possibility of Quantity surveyors being able to use BIM to accurately take off quantities hinged on one factor; the precision of the building model. In a way according to Caitlin, “traditionally, there were no prototypes with buildings. Buildings being built on-site are effectively their own prototypes as it’s being built for the first time. However, BIM allows the building to be built again, and again……and again in the virtual environment scanning for clashes, inefficiencies, design errors and plans of execution.”
This level of precision achieved has allowed quantity surveyors to perform quantity take-offs straight from the model instead of 2D drawings. This is vital as buildings are only going to get more complicated in design. Previously for example, having two different quantity surveyors take off a set of 2D drawings will yield two completely different numbers due to difference in measuring methods and drawing interpretations. By performing the take off in 3D, there is no room for differences in interpretation as what one quantity surveyor sees is exactly the same as the next.
One of few quantity surveying firms in Australia to embrace BIM, Mitchell Brandtman has refined the 5D quantity surveying process providing a unprecedented level of control over project costs and value for the client. 3D take offs allows quantity surveyors accurately measure materials as numerical values as well as provide visual representations of that take off. This visual representation is then used to collaborate between clients and designers as a means of cost.
Mitchell Brandtman has refined 5D quantity surveying into 4 distinct stages. LOD100 – LOD500. LOD meaning Level of development. As the LOD level increases, so does the level of precision of quantity take off.
For example, LOD100 represents quantity takeoff during the concept stage including only the elemental estimates using only data such as unit areas, common areas, parking spaces etc. However, from this conceptual stage, 5D quantity surveying is able to compare estimates with similar projects in the past as a baseline for what the new project can achieve. A comparison of development prices will allow quantity surveyors to show clients where costs can be reduced.
Following on, LOD200 represents a higher level of detail such as light walls, general roofing etc. LOD300 represents an even higher level of detail in that the walls aren’t just walls but are defined as for example, stud wall with plasterboard on both sides and insulation in the centre. Note that at each LOD, quantity take-offs become more and more precise and is used to compare again with the same elements in similar projects. The comparison allows for a more detailed decision to be made in terms of material substitution or other design adjustments. It is important that design changes are implemented early on before heading on-site as they can become quite costly. These LOD’s allows for that opportunity to alter the design at all detail levels.
The amount of cost control on a project through BIM is amazing. The benefits of BIM are clear. It’s been proven on their south bank project where BIM models were given to the steel manufacturers. The result? out of the 231 variations on the entire project, only 4 variations were attributed to steelworks. The future is heading towards a direction where all the players in the construction process (Architects, engineers, consultants, builders, subcontractors, qs) will all use the same 3D model for their own purposes but collaborating at unprecedented levels at the same time.
I want to keep posting about this area but I feel i’m just rambling on, so that is all for now.