2D or Not 2D
To some readers, it may come as a surprise to hear that the architect’s BIM (building information model) cannot be used for construction. Like the architect’s hand drawings and CAD (computer-aided design) files that preceded modeling, the opinion that the architect creates documents directly for use by the contractor is not true.
The history of this misunderstanding begins with the architect’s development of 2D documents, which were “issued for construction,” or “100% CDs.” The architect’s BIM deliverables have been similarly misrepresented. The drawing milestones of SD (schematic design), DD (design development), and CD (construction documents) were developed to measure design progress and to identify their purpose for use by the owner. BIM’s use as a design tool followed similar production milestones, which were instead measured through LOD (level of development) progress, identified by numbers—100, 200, 300, roughly representing SD, DD, and CD levels of completion.
Therefore, the ability to directly use an architect’s BIM for construction is incorrect. The architect’s documents and the BIM are not issued for construction, but instead, they are issued to facilitate construction by expressing the architect’s concept. The models and the design documentation contained within the BIM documents do not comprise sufficient information to construct the project.
At LOD 300, the BIM and its component objects and references are released to the contractor for the preparation of construction detailing and documentation. These documents, provided by the construction team, include coordination models, shop drawings and submittals, as well as schedule and installation information. They outline the specific and finite details required for procuring and placing the finished work. By contrast, the 300 LOD BIM merely reflects the finished design concept of the work.
This and future articles will examine the roles and functions of design and construction modeling and the information that is required to design and build a project, and how that information is developed and shared among team members. And the continuing purpose for 2D hard copy design documents.
Dictionaries define “concept” as “an abstract or generic idea.” This use makes it clear that a concept is not a specific or finite solution with tangible parameters.
The limited content of the architect’s design documentation is outlined in Section 3.12.4 of the American Institute of Architects Contract Documents A201-2017, General Conditions of the Contract of Construction, which details the conceptual nature of documents.
This explicitly requires the contractor to first check each submittal and coordinate it with the field conditions and the requirements of the work before submitting it to the design team. Modeling demonstrates an understanding of the design team’s concept.
Similarly, the contractor may manage separate project design services, through the process of delegated design. Delegated design is when the builder completes the design process of identified systems with a separate design team, managed directly by the contractor. The requirements of delegated design are represented to the builder through performance requirements.