Maximum Stair Tread Slope
This particular building code relates more to exterior
stairs and interior ones. As you can see here the concrete
stairway in the picture above is accumulating water and
creating a safety hazard. All you would need to do, to
eliminate this problem would be to put a little slope in the
stair treads.
Stair treads shall not have more than a 1 unit vertical in
48 unit horizontal slope. This would represent about a 2
percent slope or 1 inch vertical drop in every 48 inches of a
perfectly straight horizontal line. It is often referred to as
a quarter-inch per foot drop.
Reference: 2012 International Building Code - 1009.9.1 page
255
The illustration above provides us with a relatively level stairway and without any slope, something like this could prevent water from draining off of it safely.
The dotted or dashed line is level and I have lowered the
front edge of the step a little less than a quarter of an
inch, to provide you with an example of what this particular
building code is referring to.
Example 1: If you have a 12 inch wide stair tread, then you
would be allowed to drop it at least a quarter of an inch, but
no more than a quarter of an inch. This would provide you with
a quarter of an inch per foot drop ratio.
Attention: Don't forget to check with
your local building department to verify any building codes on this
website. This information could be incorrect or outdated. Building codes
are updated regularly and to some building departments have different
interpretations for certain building codes.