| The first thing you
need to clarify about spiral stairway building codes is that most of
them are different from most of the other stair building codes. The
maximum stair riser is 9 1/2 inches and the minimum tread width is 7 -
1/2 inches, but to obtain this measurement, we need to measure 12 inches
from the inside of the stair tread.
Spiral
Stairway Tread Minimum
Now here's the biggest problem with spiral stairways. Most building
codes only allow them to be used on accessible areas less than 250
square feet. This code has recently changed and used to be 400 square
feet, so make sure that you check with your local building department to
verify this information.
2000 International Building Code Book says that spiral
stairs can only be used for access areas 250 square feet and less, with
no more than five occupants.
Circular stairways are difficult for most people to walk up and down and
you might think twice before using these stairs to move any large
furniture. It wouldn't be a bad idea to move large furniture to these
areas, during construction and working around them. This could save you
a lot of frustration, after this area is completed and more difficult to
access.
The 2010 California Building Code Book does not
require spiral stairways to have closed risers.
How
to Figure Square Footage
Spiral
Stairway Access Areas
Spiral
Stairway Minimum Headroom Clearance
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