Interpretation #7150
Published February 22, 2013
Original Request
- Code Version
- 2010
- Code
- RESIDENT
- Code Description
- Residential
- Chapter
- 3
- Section
- 311.7.9.3
- Topic
- circular stairs
Question
Is it the intent of FBC Residential to require stairs in midflight (change of direction) becoming circular to meet the minimum tread depth of the Circular stair portion of the code? Also, is the intent of the word "may" used in the Circular stairways code mean the stairs can be designed to be less than the minimum required tread depth?
Answer Published 02/22/2013 at 4:33 PM
Q 1. No.The circular stair provisions
are permissive and are an alternate to
the tread depth and walkline
requirements for winders.
The circular stair provisions are
applicable to stairs that change
direction in a sweeping circular
pattern. While the code does not define
sweeping, synonyms contained in the
dictionary include extensive, broad,
comprehensive. I would not classify a
change of 90 degrees as sweeping. The
circular stair is still required to meet
the tread and walkline provisions of
R311.7 with the modifications provided
in R311.7.9.2.
Q 2. No. The Section is permissive and
establishes the minimum tread depth for
circular stairs at 9 inches. However,
while the code allows a 9 inch tread for
circular stairs, there is also a
requirement for a 1 inch nosing,
effectively providing 10 inches of
walking surface depth for the tread.
Again, this applies to stairs with a
sweeping turn which, in my view, is much
less than a 90 degree turn. The AHJ
would have to agree with the architect
that the turn created a circular stair
are permissive and are an alternate to
the tread depth and walkline
requirements for winders.
The circular stair provisions are
applicable to stairs that change
direction in a sweeping circular
pattern. While the code does not define
sweeping, synonyms contained in the
dictionary include extensive, broad,
comprehensive. I would not classify a
change of 90 degrees as sweeping. The
circular stair is still required to meet
the tread and walkline provisions of
R311.7 with the modifications provided
in R311.7.9.2.
Q 2. No. The Section is permissive and
establishes the minimum tread depth for
circular stairs at 9 inches. However,
while the code allows a 9 inch tread for
circular stairs, there is also a
requirement for a 1 inch nosing,
effectively providing 10 inches of
walking surface depth for the tread.
Again, this applies to stairs with a
sweeping turn which, in my view, is much
less than a 90 degree turn. The AHJ
would have to agree with the architect
that the turn created a circular stair
Commentary
Q 3 in Comment. Yes.