It’s important for contractors to understand the various LOD’s for each trade at any point so they can provide related cost and scheduling that is measured by the same design standards being used by the client and the designer. The understanding of how complete a model element is effects not only the Cost Estimates and Schedules, but also Constructability.

 LODs – Levels of Development

Definition (BimForum.org) –  The Level of Development (LOD) Specification is a reference that enables practitioners in the AEC Industry to specify and articulate with a high level of clarity, the content and reliability of Building Information Models (BIMs) at various stages in the design and construction process.

Level of Development vs. Level of Detail

LOD is sometimes interpreted as Level of Detail rather than Level of Development. There are important differences:

• Level of Detail is essentially how much detail is included in the model element.
• Level of Development is the degree to which the element’s geometry and attached information has been thought through – the degree to which project team members may rely on the information when using the model.
• In essence, Level of Detail can be thought of as input to the element, while Level of Development is reliable output.

Does the project contractor utilize the designer’s LODs or Design Phases?

The LODs are not defined by design phases. Rather, design phase completion, as well as any other milestone or deliverable, can be defined through the LOD language. There are several important reasons for this approach:

• There is currently no detailed standard for the design phases.
• Building systems progress from concept to precise at different rates, so at any given time different elements will be at different points along this progression.
• Design Phases are often utilized by the Prime Contractor as “Design Milestones.” These Milestones are utilized by the contractor’s estimators and schedulers. Their subcontractors should use LODs specific to their trade.

• LOD’s – Typically Utilized by Designers

We will continue this 4 part topic on Construction Design Phases vs BIM Levels of Development in our next Article 3.

Ed Wenz

Sage Estimating Consultant

5D BIM Estimating/eTakeoff

Affiliations:

AGC, ASPE, SD Navisworks GC, CM and Specialty Contractor Users Forum