I have been building stairs, off and on, for forty years.

There are certain primes that must not be violated.

The total rise is the distance from the finished floor below to the
finished floor above.

The total run is the distance from the first riser to the flat of the
landing.

The unit rise is the division of the total rise by the highest number
that fits to the code.

The unit run is the division of the total run by the number of treads,
making sure that it is code compliant.

There are codes that get involved with this.

Unfortunately, there are too many.

I work to the current UBC and, if I have to go to court, that is my
defense.

The old rule was 7/11. The new rule varies with the jurisdiction.

Why?


There are separate rules for spiral stairs.

Why?


I can run a spiral stair in my jurisdiction that demands a 4" ball
minimum on the rail but that will allow a 6" space on an open riser.

Why?




Regards,

Tom Watson
http://home.comcast.net/~tjwatson1/