My interpretation of the IRC is that an outside staircase to a basement, such as a bulkhead does not have to conform to the rise/tread and headroom restrictions because it is not a normal means of egres to living space. I believe this is the same exception that permits pull down attic stairs.
Am I correct?
I have a situation where, I goofed and forgot to tell the engineer about a bulkhead which would have stuck out 6 feet from my house. The ZBA approved the plans as is, and now I can't scribe in the bulkhead without going back to the ZBA for an additional variance. I'd have to pay the engineer again to modify the site plan, ZBA fees, and wait 60 days.
So instead of a normal "poured" cement bulkhead, I'm just going to put a door on the back of the house and frame up a staircase to the basement. It's an unfinished basement for storage, and containment of heating system/etc.
I know the bulkheads normally don't conform to the 6'8" minimum height from the tread to header, and often the treads are also smaller than the 9-10" or whatever it says in the IRC. I imagine I can frame the staircase in this fashion as well, correct?
The decent is going to be between 5-6 feet to the basement floor from grade, so if I were to meet code it would cut 5+ feet of living space out of the house for the headroom in the stair well.