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What BIM is, and what it isn't

Many of you will have heard about BIM, which is an acronym for building information modelling. It means different things to different people, as your perception of it depends on your position in the construction industry’s supply chain.

Let’s start with what BIM isn’t before we try to say what it is. BIM is not a product, a piece of technology, a single piece of software or even a procedure on how to do something. It is a concept of how to building something in complete collaboration with everyone involved, which then allows it to be built flawlessly on site. It is potentially a sea change moment in how the industry operates, fundamentally changing the traditional professional appointments, procurement routes and processes commonly used today.

The government is driving the BIM process by mandating that all central government projects by 2016 must be procured using Level 2, 3D collaborative BIM appointments. It has published figures stating that it believes a BIM-procured project will save up to 30% of the costs of a traditionally built project. If this proves to be the case, it will not be long before all developers will want to see the same level of savings on their projects.

The BIM concept is pretty simple when you distil it down to its basic elements. Before any works start on a site, the building is completely designed and virtually built within a 3D digital environment. Everything is modelled in the finest detail – every brick, piece of timber, wall tile, pipe, valve, conduit, light fitting, ceiling grid and so on. All the coordination, clashes and construction sequences are solved while the building is being designed and finalised in its virtual state. Once the virtual building has been proved to be constructable, the contractor can then build it on the site without any of the usual problems. Construction programmes will be reduced and abortive costs for delays and on-site redesign works will have been eliminated.

The 3D modelling of the virtual building not only incorporates the “physical” elements and their coordination together with their environment, but each element also contains data about its costs, weight, how long it takes to install, its sequence in the overall construction of the building, its maintenance requirements, product details such as model or serial references, colour finishes and so on.

With all of this additional information embedded within each individual element, the entire model can be interrogated to give detailed analysis on costs, construction programme and sequencing. Changes and options during the design process can be immediately evaluated as the cost plan, construction programme and labour requirements are modified in real time alongside the model.

Operation and maintenance manuals also become part of the BIM model, as once the building is in operation they will contain all of the manufacturers’ data for all the. If a light fitting requires replacement, the operator simply needs to find it in the 3D model and click on it, and he immediately knows the make, model, serial number, manufacturer’s contact details and maybe even a link to order a replacement without having to leave the model.

In order for BIM to become a reality, everyone involved in the process of constructing buildings needs to collaborate prior to the building starting on site. This is where the present appointment and procurement strategies of today’s industry will need to be reconsidered.

The traditional procurement processes are disjointed and commercially focused, which leads to adversarial contracting. More often than not, contractors set out to disrupt the construction process, highlight mistakes in the design and poor coordination, creating delays and claims simply to allow them to break even as the tender value of their appointment was below the actual cost needed to construct the building.

Prior to the contractor’s appointment design teams are often appointed on reduced fees, working to pre-tender programmes that are too short, leading to incomplete and un-coordinated designs.

The works on site need to be accurate and precise in accordance with the model. Mistakes such as steel work being installed 200mm off centre could result in hundreds of thousands of pounds invested in the BIM model being wasted.

For a true BIM experience, all those who would be involved throughout the contract should be appointed at day one to bring their skills and knowledge to the generation of the BIM model during the pre-construction period. This period needs to be generous enough to allow the model to be developed properly and accurately so it can serve its purpose.

Remember that BIM isn’t just 3D drawing; we have been doing that for years. It’s about the designers, builders and operators working together through something that just so happens to be a 3D drawing that is embedded with time, cost and maintenance data.

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