10 July 2017
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What is BIM? 

Building Information Modelling (BIM) is the process of creating information models containing both graphical and non-graphical information in a Common Data Environment (CDE) (a shared repository for digital project information). The information that is created becomes ever more detailed as a project progresses with the complete dataset then handed to a client at completion to use in the building's In Use phase and potentially on into a decommissioning phase.

When we talk about BIM maturity we are essentially talking about the supply chain's ability to exchange information digitally. The maturity levels from Level 0, through Levels 1, 2, 3 and beyond are often visualised via the maturity 'wedge' diagram conceived by Mark Bew and Mervyn Richards. Our article on BIM Levels Explained is a good place to start if you're looking for more information.

BIM dimensions are different to BIM maturity levels. They refer to the particular way in which particular kinds of data are linked to an information model. By adding additional dimensions of data you can start to get a fuller understanding of your construction project - how it will be delivered, what it will cost and how it should be maintained etc. These dimensions - 4D, 5D and 6D BIM - can all feasibly (but not necessarily) occur within a BIM Level 2 workflow.

In this article we explore what it means to add different dimensions of information to a BIM process and explore what this looks like in practice and what benefits might be expected.

3D (The shared information model)

3D BIM is perhaps the BIM we are most familiar with - the process of creating graphical and non-graphical information and sharing this information in a Common Data Environment (CDE).

As the project lifecycle progresses this information becomes ever more rich in detail until the point at which the project data is handed over to a client at completion. 

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4D (Construction sequencing)

4D BIM adds an extra dimension of information to a project information model in the form of scheduling data. This data is added to components which will build in detail as the project progresses. This information can be used to obtain accurate programme information and visualisations showing how your project will develop sequentially.

Time-related information for a particular element might include information on lead time, how long it takes to install/construct, the time needed to become operational/harden/cure, the sequence in which components should be installed, and dependencies on other areas of the project.

With time information federated in the shared information model planners should be able to develop an accurate project programme. With the data linked to the graphical representation of components/systems it becomes easy to understand and query project information and it is also possible to show how construction will develop, sequentially, over time showing how a structure will visually appear at each stage.

Working in this way is enormously helpful when it comes to planning work to ensure it is safely, logically and efficiently sequenced. Being able to prototype how assets come together before ground is broken on site allows for feedback at an early stage and avoids wasteful and costly on-site design co-ordination and rework. Showing how projects will be constructed visually is also handy when engaging with stakeholders, giving everyone a clear visual understanding of planned works and what the finished construction will look like with no surprises.

Adding sequencing information can be extremely useful, not just in the design phase, but earlier too, allowing for the feasibility of schemes to be assessed from the off. At tender stage this kind of information can allow initial concepts to be explored and communicated to inspire confidence in the team's ability to meet the brief.

It's important to note that working with 4D information doesn't negate the need for planners who remain an integral part of the project team. Rather than creating programmes as proposals develop, as is the case in traditional workflows, in a digital workflow planners can now influence and shape proposals from a much earlier stage in a project. Indeed, by being closer to the wider project team and providing feedback earlier in the process, there is the potential for planners to add significantly more value to a construction project.

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5D (Cost)

Drawing on the components of the information model being able to extract accurate cost information is what's at the heart of 5D BIM.

Considerations might include capital costs (the costs of purchasing and installing a component), its associated running costs and the cost of renewal/replacement down the line. These calculations can be made on the basis of the data and associated information linked to particular components within the graphical model. This information allows cost managers to easily extrapolate the quantities of a given component on a project, applying rates to those quantities, thereby reaching an overall cost for the development.

The benefits of a costing approach linked to a model include the ability to easily see costs in 3D form, get notifications when changes are made, and the automatic counting of components/systems attached to a project. However, it's not just cost managers who stand to benefit from considering cost as part of your BIM process. Assuming the presence of 4D programme data and a clear understanding of the value of a contract, you can easily track predicted and actual spend over the course of a project. This allows for regular cost reporting and budgeting to ensure efficiencies are realised and the project itself stays within budget tolerances.

The accuracy of any cost calculations is, of course, reliant on the data produced by multiple teams and shared within the Common Data Environment. If that information is inaccurate, so too will be any calculations that rely upon it. In this respect using BIM to consider cost is no different to more traditional ways of working. It is for this reason that quantity surveyors and estimators still have an important role to play, not only in checking the accuracy of information but also in helping to interpret and fill information 'gaps'. Many elements of a project will still be modelled in 2D or not at all. There's also likely to be differences between models in how things are classified and the cost manager will need to clarify and understand the commonality between what at first feel like disparate things.

An information model is likely to contain three types of quantity. Quantities based on actual model components (with visible details) which you can explore through the model are the most obvious. Quantities may also be derived from model components (such as mouldings around windows) that aren't always visible. The third kind of quantity is non-modelled quantities (these include temporary works, construction joints etc.). Unless the construction phase is modelled then the design model will show, graphically, design quantities but not the construction quantities. A cost manager is likely to be skilled in picking up the quantities that aren't solely based on model components.

One of the advantages of extrapolating cost from the information model is the fact that the data can be queried at any time during a project and the information that feeds cost reports is regularly updated. This 'living' cost plan helps teams design to budget and because cost managers are engaged from the start of a project this allows for faster, more accurate reporting of costs at the early stages of a project. Compare this to a traditional approach where a cost manager's report may be updated a few times during the early stages of a project with completed designs only fully costed at the end of the project team's design process. 

The cost manager may have to get used to working earlier and more iteratively than in a traditional process but has just as important a role to play in overall project delivery. 

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6D BIM (Project lifecycle information)

The construction industry has traditionally been focussed on the upfront capital costs of construction. Shifting this focus to better understand the whole-life cost of assets, where most money is proportionately spent, should make for better decisions upfront in terms of both cost and sustainability. This is where 6D BIM comes in.

Sometimes referred to as integrated BIM or iBIM, 6D BIM involves the inclusion of information to support facilities management and operation to drive better business outcomes. This data might include information on the manufacturer of a component, its installation date, required maintenance and details of how the item should be configured and operated for optimal performance, energy performance, along with lifespan and decommissioning data.

Adding this kind of detail to your information model allows decisions to be made during the design process - a boiler with a lifespan of 5 years could be substituted with one expected to last 10, for example, if it makes economic or operational sense to do so. In effect, designers can explore a whole range of permutations across the lifecycle of a built assets and quickly get an understanding of impacts including costs. However, it is at handover, that this kind of information really adds value as it is passed on to the end-user.

A model offers an easily-accessible and understood way of extrapolating information. Details that would have been hidden in paper files are now easily interrogated graphically. Where this approach really comes into its own is in allowing facilities managers to pre-plan maintenance activities potentially years in advance and develop spending profiles over the lifetime of a built asset, working out when repairs become uneconomical or existing systems inefficient. This planned and pro-active approach offers significant benefits over a more reactive one - not least in terms of costs.

Ideally the information model should continue to develop during the In Use phase with updates on repairs and replacements added in. Better yet, a myriad of operational data and diagnostics can also be fed in to inform decision making still further.

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What to read next

BIM Levels explained
Definitions for levels of BIM maturity from Level 0, through Level 1, Level 2 and Level 3 and beyond.

Four things Mark Bew told us about the future of BIM and digital construction
Mark Bew MBE, chairman at PCSG and the UK BIM Task Group, shared his thoughts on the UK's Level 2 BIM programme and revealed that a BIM Level 3 mandate will form part of Digital Built Britain plans.