Question from one of the PPD practice exam:
An architect is designing a two-story condominium building. There will be a 14’ floor-to-floor height between the main level and the second floor. When designing the stair section, the architect wants to maximize the riser heights in order to save space.
What is the maximum riser height possible?
The answer is 7" but I really think it should be 7.75". What am I doing wrong here?
@hanpingsh Great question!
To answer this question you should refer to IBC section 1011.5.2 Riser height and tread depth. This section states that stair riser heights shall be 7 inches maximum.
There are a few exceptions, however. In this case the relevant exception is exception 3, which states “In Group R-3 occupancies; with in dwelling units in Group R-2 occupancies; and in Group U occupancies… the maximum riser height shall be 7.75inches”
To know whether or not this exception applies we need to check our use group. Section 310 specifies what uses fall into the residential use group. Residential group R-2 is for “occupancies containing sleeping units or more than two dwelling units where the occupants are primarily permanent in nature”. A condominium building would fall into that use.
At first glance it seems that the exception applies, however, there is a key phrase “with in dwelling units in Group R-2 occupancies”. And because the question does not specify that the stair is within an individual unit, the 7inch maximum still governs.