One of our earliest decisions in the design process of a project is the general circulation pattern within a building. When deciding on the location of the pattern, there are certain conceptual goals to achieve. The goal entails a complex combination of factors, such as; spacial site orientation, internal program relationships, views and flows.
As the design process continues and we work on laying out the rooms, the final dimension of a corridor is informed primarily by code considerations (capacity) and accessibility issues (ADA). In theory, the 6’0” corridor in our Amherst College project works out well. We have kept our frames very narrow at 1-1/4”. This will allow space for two 34” doors and for the 32” clear opening required when one of the leaves is closed.
Illustrating the theory that 6’0 is adequate space for the two 34″ doors to open 90 degrees
What this theory does not account for is the door hardware which can create a constricting factor to the accessibility of the corridor. An average door handle protrudes about 2-1/2” from the wall. A wall mounted door stop will add almost 1” to each side. In order for a door to swing clear to a 90 degree angle, the real minimum dimension of a double wide corridor should be at least 6’4” to account for some tolerance.
Showing the added restrictions that the door hardware creates
Interestingly, with the help of our code consultant, we discovered that even if the door does not open at a 90 degree angle, it does not hinder the accessibility of the corridor. The minimum dimension at the narrowest point, measured from the edge of closed door to any point of the open door frame, has to provide a clearance of at least 32”.
With a clearance of 32″, the corridor is accessible and the 6ft corridor is successful
Using the design process of the Science Center at Amherst College as a case study, it becomes clear that even at conceptual levels, if we are designing to tight tolerances it is a good idea to account for all built elements prior to determining certain dimensions.