The stair railing balusters must not allow a 4 inch ball to pass through.
Concrete spiral staircase plans.
Winding its way up the building s four.
Each tread must be at least 7 1 2 inches deep at a point 12 inches from its narrow end.
There must be a minimum of 6 feet 6 inches of headroom at each step.
The handrail must be 34 to 36 inches above each tread nose.
Your spiral staircase may need to be a certain minimum width if it s to serve as the main stairway for your home.
A spiral staircase made of concrete rises through the centre of an open plan office designed by architects hildebrand in steinhausen switzerland.