Friday, 17 May 2013

LOD Specification is Here!

After two years of dedication and hard work, the first draft of the BIM Level of Development (LOD) Specification is finally available for public comment. The work group responsible for this important document is a joint task force consisting of members of the AIA and the AGC of America’s BIMForum.

Cam_LOD200-100 Cam_LOD200 Cam_LOD300

You might be asking, ‘what is an LOD Specification and why do I need one?’ The AIA’s digital practice documents defines 5 fundamental levels of model development, but offers only general definitions of what each level means. I offered some explanation of these in an older blog post.

This new document offers more detailed definitions of how model authors must create virtual components in order to satisfy the requisite reliability. Building upon the AIA’s original LOD definitions, the LOD Specification can be seen as a companion document – much the same way as a dictionary can be a companion to both an author and a reader.

The public comment period will be completed by early June 2013, but the work group will continue to revise the LOD Specification and publish it on an annual basis. Go to to download your free copy today. You can also read a very detailed article about it by work group chair Jim Bedrick on the AECBytes website (“Level of Development Specification for BIM Processes”).

Wednesday, 1 May 2013

Gross Floor Area of a Mass

We had a good Revit question come in from our Dubai office this morning concerning the calculation of gross floor area in a mass. What could cause a mass object to not list any gross floor area in the Properties palette?


First, you must ensure that at least one Mass Floor is selected. You can access this setting by selecting a mass element and then clicking on Mass Floors in the contextual tab of the ribbon.

In this case, one level was selected – but the level was NOT intersecting the actual mass element.


This is a bit of a limitation if you are using Revit for urban design or master planning on a hilly site. You will need to create at least one level for each plateau of buildings in order to utilize the Gross Floor Area property.