5D BIM – the need for elementcusters

Bouwdata

Dec 4, 2024

5D BIM – the need for elementcusters

It happens more than once that the building owner discovers when tendering that his/her budget is insufficient for the dream design that his/her eager architectural firm has worked out. To put a stop to these frustrations on both sides of the drawing board, there is 5D BIM. But how do you do this in practice?

First, we must avoid putting the current information and cost management chaos solely in the hands of computer geeks to solve. Accountancy also had a calculation system first before various software developers got to work. In the construction industry, for a few years now, all the ingredients – read standards and norms – have stabilised enough to create a comprehensive classification scheme.

Its capstone is the ISO 12006-2:2015 Building construction – Organisation of information about construction works – Part 2: Framework for classification. In fact, every information and cost manager in the construction industry should know this ISO standard inside and out!

There are various interpretations of this: SfB, CCS, Uniclass, Omniclass. But this is not enough. Hereafter, we throw in a few other standards that are at least as necessary.

On Construction Process, in my opinion, RIBA1 plan of work 2020 from the UK is the most appropriate. It starts with a table where each column is a ‘Stage’.

Stage 1 0 Strategic Definition is the ‘sniffing round’, so to speak. The real work starts in Stage 1 Preparation & Brief.

In this Stage, it is best to first create a mass model, which, via an estimate, is going to be tested against the available financial resources.

The standard to be consulted is NEN 2699 Investment and operating costs of property – Terminology and classification. This standard has explanatory notes and a table in Excel format that expands down to 6 levels. At level 3 you will find the element clusters.

Such an estimate is based using unit costs2 of element clusters determined from previous projects. Note that the projects do not have to be similar, but the element clusters do.

E.g. for element cluster B1A Foundation, there could be a ‘punch list’:

  • general foundation slab
  • watertight pit with 1 /2 /3 underground levels
  • foundation trenches and/or plinths and floor slab at ground level
  • false sumps
  • gravel cores
  • pile foundation with soil displacement
  • pile foundation with soil evacuation
  • pile walls
  • diaphragm walls
  • earth anchors
  • shoring
  • groundwater lowering
1 I very explicitly retain here the English term from the standard in contrast to the project-specific Phases [P] or subprojects that are to be realised chronologically.

2 Unit costs (KKG) are characteristic costs per unit of cost carrier for the entire structure, a spatial part thereof, an element cluster, an element or per functional unit (component) Nice theory, but what about in practice?

I am lucky to have early adopters. With the building project of the new hospital AZ St Maarten in Mechelen, a design by VK Architects & Engineers, we collected these unit costs after completion. Bimplan visualised them and they were presented to the public at a symposium in spring 2019.

Throughout budget control, including the processing of work supplements or reductions, care was taken to link all costs to the correct element cluster. We therefore had, in addition to the as built model, the total amounts of:

  • B1A Foundation
  • B1B Skeleton
  • B1C Roof construction /roof finishing
  • B1D Facade construction / facade finishing
  • Etc.

Bimplan derived a mass model from the as-built model and extracted the necessary quantities from it in accordance with NBN EN 15221-6 Facility Management – Part 6: Area and Space Measurement in Facility Management.

If you now look at this mass model from underneath, all visible surfaces will constitue the Building Footprint
In other words, the total price of element cluster B1A Foundation divided by this surface yields a concrete unit cost that can be used in subsequent projects. Add a brief explanation – i.e. a watertight single-storey pit on a pile foundation with soil displacement and groundwater lowering – and a reference date, and using AI you can build trend lines for each element cluster that will allow you  in subsequent projects to test this first mass study against the available financial resources in no time. Thanks to the AZ St Maarten project, a complete dataset at element cluster level is now available. The health care sector  is showing solidarity and sharing knowledge. At UZ Gent, with also VK Architects & Engineers as design team and Bimplan as consultant on 3D modelling and PB calc & consult as budget controller, this is now being gratefully used.

VK designs with all the necessary tools to convey its ideas to the client BUT at the same time also makes a mass study in accordance with the shell method whereby we have a set of unit costs available for each zone and each element cluster derived from namely AZ St Maarten, allowing to calculate decisions quickly. Glenn De Hondt of VK puts it as follows: At first it seemed quite complex, and very far-reaching, but once I really delved into the systematics and the way everything is structured, I had to admit that Peggy’s system was damn well thought out. […] For us as designers, it is a huge advantage to be held up to a mirror by Peggy with the budgetary impact from the very beginning of the design, from the moment the first broad outlines are drawn. Thanks to the BouwData method, you get an initial, already quite correct estimate from the very first gross design, and you can move quickly by making alternative design choices.

It may seem like a hindrance to the design process, but nothing is more annoying to have to revise your work after days, weeks, or months because it then turns out that you were not completely on track towards the budget you had drawn up, and your client had presented the wrong picture.

Because Peggy uses data from a BIM model, she can also quickly show the budgetary impact of certain changes or design choices.” To date, AI has been limited to the excellent cooperation between all the brains of the above team but as support for professional cost control and willingness to work to standards and norms grows, we can envisage developing real AI as well.

In the meantime, there is an A3 poster with an overview of all the standards and norms that can together form a chart of accounts for the construction industry. This is available free of charge by simply emailing info@bouwdata.net


1) Royal Institute of British Architects
2) Ik behoud hier zeer uitdrukkelijk de Engelse term uit de standaard in contrast met het projectgebonden Phases [P] of deelprojecten die chronologisch gerealiseerd gaan worden
3)
Kostenkengetallen (KKG) zijn kenmerkende kosten per eenheid van kostendrager voor het gehele bouwwerk, een ruimtelijk deel daarvan, een elementcluster, een element of per functionele eenheid (component)

 

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