BIM Technical Standards: File Structure and Organization

Data Structure

When creating new BIM data, how this data is divided and structured is important in ensuring project collaboration and in establishing the foundation for the building information life-cycle. How the data is divided will vary with the specifics of the individual project. Software platform, contractual obligations, and team member's BIM capabilities must all be factored into the data structure.

Standard

• Data structure must be agreed upon and documented by the team as part of the BEP.
• At a minimum, the data structure must be addressed twice on a project - once at the inception of the design phase and once at the kick-off of the construction phase.
• Each object or data set must exist in one file only. Data duplication is not permitted.
• Only one major structure will be created within a single file. For this standard, a major structure is one larger than 3,000 sq. ft.
• Data must be structured in a logical manner which is consistent across a site. For example, if a building is to be divided by floor, then the entire site must be divided by floor.
• Data will be separated to ensure that model files remain workable on industry standard hardware.

Guidelines

• Phasing and 4D planning should be contained within single files, where possible.
• When working on a site which has existing BIM data, the structure developed by previous teams should be used. Modifications to the existing data structure should only be made in cases where not doing so would adversely affect the project.
• Data structure should be established using some logical breakdown of the project data. This should take into account both immediate project needs and future use as part of the building information life-cycle. Some examples of data separations are:
  • Floor by floor or logical groups of floors
  • Trades (e.g. cladding, steelwork, plumbing, electrical)
  • Construction Joints
  • East Wing / West Wing
  • MEP Systems

Origin point, northing, and elevation

One of the simplest yet most critical aspects of good project coordination is the establishment of a common or shared base point for all BIM data to follow. It is also essential to have a common site base point as the data is used through the life-cycle of the building.

Standard

• A common project or site base point is to be agreed upon by all team members as part of the BEP.
  • Where possible, this point should be a real-world location which is measurable, such as a corner of a building.
• All BIM data that has an origin point must use this common point.
• The selection of the origin point must take into account the numerous software platforms used and also be compatible with as many as possible.
  • If any BIM data exists for the site, its origin point will be used for all future work. This means that if one building exists on a three building site, its origin point will be used for all subsequent BIMs.
• If there are conflicting existing origin points, the building with the largest square footage shall be used to establish the origin point.
• True North and Project North will be defined within the BEP and will be implemented consistently across all BIM data.
• Elevation of BIM data will be kept consistent across all BIMs. In cases where an authoring platform is not able to work with a consistent elevation, it must be documented within the BEP.

Folder Structure

The final data submittal is to have all data organized into a folder structure, as outlined below. The list provided is not intended to be all inclusive and only serves as an outline. For example, you may add sub-folders as needed. Additional folders must adhere to the General Naming Standard. All individual shop drawing and product data is to follow a file naming standard which starts with CSI numbering system, followed by description of the CSI Section, followed by description of the file.

Each included file should be linked to its respective element in the BIM model using the parameters for URLs, as outlined in the Minimum Attributes Standard. For example, if the user clicks on a building element in the BIM model, it should link with the proper documentation such as shop drawings or product information.

For the final submittal, a model builder is required to run all models in an independent computer to ensure that linking is done correctly and properly. It is unacceptable to use an arbitrary "letter", for example E: - F: - G:, for a directory system that GSA server cannot identify. All files should run smoothly within the same directory environment and linking should be properly established in this setting. Submit documentation with a diagram and a brief explanation of how linking has been established between elements in the BIM and these files. See Referencing and Linking for additional requirements of linking data within your BIM.

Globally Unique IDentifier (GUID)

Globally Unique IDentifier or GUID is a universally unique number assigned by the BIM authoring software to every element within the BIM. The GUID is preserved when data is exported to exchange formats such as IFC and COBie. Because of this preservation of the GUID, is important on projects which have implemented BIM life-cycle workflows. The standards below only apply to projects which have existing BIM data actively being used to support a building data life-cycle program.

Standard

• Objects may never be deleted from within the BIM until the end of the project. If an object is to be removed it must be flagged as demolished within the BIM.
• At the conclusion of the project, a list of all demolished objects which includes the GUID must be provided to the GSA Region 5, BIM Champion, Project Manager, and Facility Manager.
• If for any reason BIM objects must be erased, such as data corruption, they must be recorded with their GUID. This list must include both the erased object's GUID as well as the replacement object's GUID. This list must be provided with the final submittal of the BIM to GSA.

Rooms, Spaces, and Zones

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While almost all geometry within your model will directly represent real-world objects, rooms, spaces, and zones don't exist in the real world. Rooms, spaces, and zones are spatial abstractions used to carry data, for a number of purposes, during all phases of a building life-cycle.

• Room - Bound to a single physical room within a building. Used to hold architectural information for the room. Typical properties of a room are name, number, and finishes.
• Space - Bound to a single, physical room within a building. Used to hold MEP requirements of the room. Typical properties of a space may include lighting calculations, electrical loads, and air flow requirements.
• Zone - A collection of spaces which share common MEP requirements.

GSA Spaces

GSA has very specific requirements for spatial data management (SDM). These requirements have been implemented on a national level through the GSA BIM Guide Series 2. Adherence to these requirements involves using rooms, areas, spaces, and zones in specific ways. For recommendations on Revit implementation of the SDM requirements, see the Revit Spatial Data Management tutorial.

Standard

• Rooms, areas, spaces, and zones will adhere to requirements defined within the GSA BIM Guide Series 2.
• All Revit architectural models will be created using the SDM Architectural template.
• All Revit architectural models will be created using the SDM Architectural template.
  • Final approval of spaces will come from GSA SDM group.
• BIMs will not contain duplicate or overlapping rooms, areas, spaces, or zones. For example, two rooms may not overlap, however areas, spaces, and zones may contain multiple rooms.
• Where appropriate, rooms, areas, spaces, and zones will possess correct composition relationships to model geometry. For example, rooms will be bound to wall objects.
• When supported by the authoring application, rooms, areas, spaces, and zones will properly constrained in all three axis.