In 2003, we sought the BIM benefits of a coordinated construction document set using a single source Revit model.
As the model changed, the construction document views (plans, elevations, sections, schedules) immediately updated. It was powerful to have design options immediately update both visual and the data views contained in the facility model and building product models. In addition, Level-of-Detail (LOD) was built into each view.
Our first Revit standards started as Level-Of-Detail (graphical). However, the inclusion of data in our Revit model standards began the evolution toward Level-Of-Development (graphics and data). We started integrating room programming data and building product data earlier into the project.
For example, during the project’s conceptual-schematic stage, Revit Area/Room Tags monitored the floor plan square-footage for each department. These totals were established in the programming stage. Area/Room Tags incorporated basic MEP system requirements (lighting, medical gasses, HVAC) with the occupancy loads for each area. All of these data-driven decisions transitioned from schematics and into DD, which produced the final CD model documents.
Early in 2013, I found this LOD-definition image from Australian registered architect and practicalBIM.com blogger Antony McPhee.
He provided a visual description of BIM LOD in his article What Is This Thing Called LOD?
McPhee provided a listing of data and model descriptions with a visual comparison for both BIM Level of Development and Level of Detail.
For example, a BIM Level of Development (LOD) for a chair might go:
- LOD 100 = there is a chair
- LOD 200 = there is a chair that has nominal space requirement of 500×500
- LOD 300 = there is a chair with arm rests and wheels
- LOD 400 = manufacturer and model number
- LOD 500 = manufacturer and model number, supplier, date purchased
His article identified two value points that clearly stood out:
- An LOD table tells others what information they can actually use
- LOD is also a measure of a project’s progress.
LOD is a measure of certainty, or confidence, regarding current information.
It defines risk. It prompts you to ask, “can I or should I use the Level-of-Information in the project for my project work? If I use this information, what is the probability of it changing? What is my risk, and what is the cost and time to revise my model work?"
As LOD helps answer these questions, it becomes a ‘lightweight’ project management tool to define the project’s progress and completion deadlines.
In December 2013, Autodesk University featured a class taught by Mayo Clinic BIM program manager Andy Jizba that reviewed the Mayo Clinic Modeling Development Specification (MDS).
Jizba contemplated the same questions as those McPhee defined in his article. Jizba, representing an owner, shared how they laid out a BIM execution plan that defined the use of Level-of-Development (LOD) for Mayo Clinic projects. They created a contractual deliverable process that defines
- Owners’ usage of BIM to establish LOD deliverables prior to project start. The project team learns how the owner plans to use BIM for their building’s life cycle management, as well as operations and maintenance (O&M).
- Project team members’ usage of BIM that mutually defines LOD for each discipline, by each discipline from the initial, project kick-off meeting with the owner.
- Team members’ LOD roles (lead, support and use) and responsibilities at each phase of the project.
- Model and project management: Members use Revit family LOD shared parameters to communicate, monitor and manage a project’s LOD progress for each discipline and phase. LOD parameters identify the level, risk and status of model development to minimise rework of the model.
- Interoperability for integrating company LOD with project LOD. This process allows each stakeholder to integrate their independent Revit-BIM LOD standards into the projects’ interdependent LOD standards.
I believe the collaborative nature of the Mayo Clinic MDS Guidelines is part of their successful LOD integration. The Mayo Clinic MDS defines the owner’s BIM requirements at the project kick-off meeting, acknowledges the value of each team member's internal LOD standards, and provides model and data guidelines to deliver efficiency for all members.
BIM Level-of-Development continues its evolution as BIM Team members are introduced to new BIM-Driven and BIM-Dependent Processes.
Consider how MEP engineers design and model at a lower LOD in anticipation of handing off their models to MEP prefabricators. This process minimises the engineers’ modeling time while providing models to the MEP prefabricators that can transition to a higher LOD for fabrication.
As BIM software, teams and projects move to the cloud, LOD will be redefined again.
When cheap, large hard drives, installing 16 or 32 gigabytes of RAM (memory) to a desktop, providing one gigabyte network connections and 64-bit OS became the new normal, BIM software usage exploded.
The cloud’s project-processing power is not limited to the traditional desktop and server computers. The cloud will functionally change processes and priorities; that currently limit our BIM project processes.
Personally, I anticipate the cloud will increase both Level-of-Detail and Level-of-Development, drastically decrease or eliminate the concern for model file sizes, reduce or eliminate the linking of consultants’ models; as we see members working in a single model file and increase earlier access for team members (manufacturers, subcontractors, component fabricators, civil engineering consultants) to the project team’s design process.