The ceiling joists were sized from the table column for an uninhabitable attic with limited storage at 20 pounds per square foot, and the stair is now framed and finished. How should the inspector judge the framing?
- AAccept it; the stair affects how the attic is reached and not the load the framing has to be designed for
Access is exactly what the table keys on. A fixed stair changes how a space gets used, and the table assigns a higher load for that reason.
- BAccept it; the limited storage column already accounts for occasional foot traffic during maintenance
The limited storage value contemplates occasional light storage in a space reached by a hatch or a pull-down. It is not the value the table assigns once a fixed stair is provided.
- Reject it; an attic served by a fixed stair is designed for 30 pounds per square foot, so the joists must be rechecked
- DReject it; an attic reached by a fixed stair becomes a habitable room and must meet the ceiling height requirements
A fixed stair does not by itself make the attic habitable; habitable space brings ceiling height, light, ventilation and egress requirements that follow from finishing the space, not from the stair. The immediate issue is the design load.
Why C is correct
The live load table gives attics served by fixed stairs 30 pounds per square foot, against 20 for an uninhabitable attic with limited storage. Adding the stair changed the governing load, so the joists must be rechecked against the higher value and reinforced if the span no longer works.
What this question is testing
Whether the candidate can read the live load table by how a space is accessed and used, recognizes that a field change to access can change the governing load, and knows the correct response is to recheck the framing.
On the job
Owners add attic stairs all the time, sometimes under a permit for something else and sometimes with none at all. Inspectors who see a new stair look at what the ceiling joists were sized for, which means going back to the plans. The correction is usually sistering the joists or adding a beam, and it is far easier before the attic is floored and filled.
Memory technique
Give an attic a stair and it fills up.
Exam tip
The live load table treats attics by access. A fixed stair moves it to 30 pounds.
Where to look it up
IRC Chapter 3, design criteria, the live load table with its attic entries.