Postsecondary Education

NCES 2006-160
May 2006

3.3 Proration and Phantom Walls

When a room serves several purposes or users, the institution may choose to prorate and allocate the square footage between two or more space uses, functions, or organizational units. For institutions with major sponsored research activities, proration of multiple functions is often necessary to identify accurately how each space is used. Other cases may require the recognition of two or more distinctly different architectural uses within a space (e.g., a departmental conference room housing a substantial reference library) or the sharing of an office by two or more departments. Proration can be done either on the basis of the relative time expended on each activity or on the basis of the proportion of the room area dedicated to each activity.

There are two basic approaches to proration. One method is to prorate from floor plans by the insertion of “phantom walls,” indicated by dashed lines or other artificial boundaries on floor plans to separate adjacent uses or assignments. The use of phantom walls requires that each space (i.e., each part) of the room be given a unique space identifier, which can be accomplished by adding an additional digit or character to the existing room identifier. For example, Room 210, which is used as a storage room by both Biology and Chemistry, could be identified as Space 210A and Space 210B, and the pro rata organizational assignment and share of space can be identified with each. The other method is to apply percentage figures to each assignment, use, or function being prorated. Whatever method is used, the resulting information should be capable of being summarized into standard space use codes and related categories for external reports, utilization studies, and institutional planning.