When new to building information modelling (BIM), it’s easy to mix-up definitions when it comes to dimension modelling and maturity levels. Some will claim execution at BIM level 3, when in fact they mean 3D modelling, which is mostly an indication of BIM level 1 maturity.
BIM dimension modelling
BIM dimensions are the specific parameters that are added to the existing information, creating models for the entire project lifecycle. The dimensions added are according to project stage requirements, complexity, and purpose. This provides a greater understanding of the project. These BIM dimensions include;
· 3D: this dimension is widely understood in the construction industry; it is the geometrical dimension. 3D BIM therefore stores all data in one central location, typically a common data environment (CDE). This is ideal for structural elements, providing enhanced visualisation, easy collaboration, and reduced reworks due to transparency.
· 4D: this is time. This is the duration to complete the project, the sequencing of various components, and the time needed to make the project operational. 4D is useful in obtaining accurate programme of works and visualising how projects will develop sequentially.
· 5D: this is cost estimation, budget analysis and tracking. This dimension analyses the cost that will be incurred overtime in project activities. Additionally, it allows cost managers to extrapolate quantities, see costs in 3D form, and get changes notifications as cost is linked to project components. This also helps in predicting budgetary requirements.
· 6D: this is the sustainability and energy efficiency aspect of BIM. It analyses the energy consumption of a building against the estimates at the initial design stage. This increases the understanding of the asset and where money can be spent to make it sustainable and cost-efficient.
· 7D: this is all about operations and management by the owner, aka Facilities Management (FM). This tracks important asset data to be used at later stages such as; warranty information, technical information, maintenance manuals etc. It is arguably the most important dimension of BIM modelling as during the operations and maintenance phase is when most BIM benefits are recognised.
*Note: There’s currently no universal agreement as to what 6D and 7D modelling entails, however, experts lean towards sustainability and facilities management as it Includes lifespan and decommissioning data modelling.
BIM levels
There are currently four levels to BIM execution, each requiring a level of collaboration and dimension modelling to achieve.
· Level 0: means there is no collaboration, where only 2D CAD drafting is utilised, mainly for production information output and distribution is via paper or electronic prints, or a mixture of both.
· Level 1: comprises a mixture of 3D CAD for concept work, and 2D for drafting of statutory approval documentation and production information, with a collaboration tool providing a Common Data Environment (CDE). CAD standards in this level are governed by the international BIM standards ISO EN 19650. Collaboration at this level is still low between different stakeholders, as each manages their own data.
· Level 2: collaborative working requires an information exchange process which is specific to that project, and is coordinated between various project participants and systems. Additionally, all design software in the project must be capable of exporting to one of the common file formats such as IFC (Industry Foundation Class) or COBie (Construction Operations Building Information Exchange). Lastly, all federated model information is shared within a Common Data Environment (CDE).
· Level 3: this is also known as ‘Open BIM’ and has not yet been fully defined. However, the vision promises collaboration between all stakeholders through a shared model, stored in a central repository. It allows all professionals work on the same model simultaneously, which eliminates the chance of conflicting information.
There are different guidelines that need to be met to achieve different levels of BIM. Transitioning from one BIM level needs expert and specialist consultation, to optimise the level’s benefits. One step at a time, after all, it is a numbers game!
