The BIMForum recently released the 2013 Level of Development (LOD) Specification, which includes a new LOD level – LOD 350. Prior to this development, the AIA G202 LOD definitions left a lot of room for interpretation by designers and engineers, thus creating uncertainty about model integrity by downstream users. General contractors often recreate models from scratch because they can’t rely on the quality of models coming from other project team members. The new 2013 Level of Development Specification changes all this.
Today, it is common to see LOD 300 models used to create construction documents for the building permit process. General contractors rely on these permit drawings for full trade coordination. LOD 300 specifies that building elements are located correctly with accurate slopes (such as sloped structural beams and gravity plumbing lines); however it does not include the level of model detail needed for full coordination. Information required for LOD 400 may not exist until later in the shop drawing phase, thus creating a gap in information for general contractors to perform pre-construction coordination.
LOD 350 closes this gap by requiring more model detail and model elements showing how building elements interface with other building elements or systems, with written definitions and graphics. The image below tells the story well – LOD 350 adds a base plate and anchor bolts to a steel column to show how it connects with the concrete footing.
Model based construction layout gets much easier for contractors when the building structure and systems such as MEP are developed to the LOD 350 specification. For MEP layout, this means that the model will include accurately placed hangers that contain layout points or allow these points to be added to Revit families very quickly. The layout points can then be replicated onsite using total stations or multistations for fast and accurate field execution. For building structures such as concrete slabs and footings, sleeve and anchor bolt locations are accurately modeled and ready for field layout without additional drawing or modeling.
BIMForum’s new LOD specification adds a new level of clarity for each LOD per discipline (structures, exterior skin, interior construction and building services). This is an important BIM development that provides a vehicle for clarifying BIM scopes, increasing the reliabilty of models and laying the groundwork for BIM permitting deliverables.
LOD 350 for Domestic Water Piping – D2014.40
LOD 350 for Floor Structural Frame – B1010.10
What do you think? How will LOD 350 affect your business? Share your thoughts below.
For more information about BIM for building construction, visit http://www.leica-geosystems.us/BIM.
Cathi Hayes is a BIM business manager at Leica Geosystems.