BIM (Building Information Modeling) is a multi-dimensional approach to the life-cycle analysis of buildings. It integrates the various disciplines involved in the design process in a model that is a digital three dimension spatial representation. The whole design is based on this model, from which the typical 2D drawings (plans, elevations, sections) can be obtained. BIM involves representing a design as combinations of "objects" – vague and undefined, generic or product-specific, solid shapes or void-space oriented (like the shape of a room), that carry their geometry, relations and attributes. BIM design tools allow extraction of different views from a building model for drawing production and other uses. These different views are automatically consistent, being based on a single definition of each object instance.
BIM software also defines objects parametrically; that is, the objects are defined as parameters and relations to other objects, so that if a related object is amended, dependent ones will automatically also change. Each model element can carry attributes for selecting and ordering them automatically, providing cost estimates as well as material tracking and ordering. BIM therefore covers more than just geometry. It also covers spatial relationships, light analysis, geographic information, and quantities and properties of building components (for example, manufacturers' details).
A BIM model is therefore dynamic (changes with time), and contains the information attributed to the different objects used (such as cost and technical information). This characteristic justifies the term multi-dimensional when referring to BIM (the three spatial dimensions, time, cost, etc).
For the professionals involved in a project, BIM enables a virtual information model to be handed from the design team (architects, surveyors, civil, structural and building services engineers, etc.) to the main contractor and subcontractors and then on to the owner/operator; each professional adds discipline-specific data to the single shared model. This reduces information losses that traditionally occurred when a new team takes 'ownership' of the project, and provides more extensive information to owners of complex structures.
BIM benefits are numerous. During the conceptual phase of projects, the 3D approach allows for a more direct and versatile method to analyze the design options. During the design phase, the fact that all specialties (architects, engineers) base their design on one model makes the design process much more immune to discrepancies between the different designers; detecting incompatibilities is much easier, with obvious benefits as well in terms of time. In a pre-construction phase, the same characteristics facilitates the process of detecting errors and omissions. This is of great benefit to Owners and Contractors, as potential construction problems can be foreseen early on, and design corrections performed before construction starts. Bills of quantities can be generated automatically, with quantity surveys performed with a much higher degree of reliability. BIM models can further be synchronized with MEP and structural design software. It can also be used in conjunction with BMS (Building Managements Systems).