I have mentioned in my "About" page, that many RFI's are repeat RFI's - meaning that they show up again and again on similar projects.  High on the list of repeat RFI's reads an RFI that goes something like this:

In the 2nd floor men's restroom, the finished ceiling is listed as 9'0" above finished floor.  However, the 14" wide flange beam at structural line C and the 16" by 14" supply duct running perpendicular, leave no room for the fire sprinkler line, can lights, or ceiling framing system.  Can we reduce the finished ceiling to 8'6" to accommodate the structure and utilities at this location?

I wish I had a nickel for every time I have written or read an RFI like this one.  

There are a lot of ways to solve this RFI if this issue is discovered early in the design phase, but, most frequently, this issue is not discovered until late in construction when the ceiling framing system is being installed - leaving the project Architect with limited options.

The Cause:  This is a classic case of incomplete coordination of design.  The Architect, Structural Engineer, Mechanical Engineer and Electrical Engineer all have elements of their work that need space above the ceiling, but no one has played "trafffic cop" to make sure it will all fit within the space provided. 

The Best Solution:  So, the trick here is early detection.  This a place where Building Information Modelling (BIM) really shines, but a full BIM model is not really necessary to identify or solve this problem.  All that is required is an overlay of the Structural, Mechanical and Architectural drawings to find out how much above ceiling space is available, and how much is used by structural members, ductwork, etc.  Then, a re-design of those areas that don't fit is required - hopefully well before construction has begun.  The later this issue is discovered and addressed in a project, the more likely it is that lower finished ceilings will result.