The stair shop drawing shows a commercial egress stair with wood treads. What minimum tread depth does the IBC generally require?
Correct Answer
B) 11 in.
IBC 1011.5.2 generally requires stair tread depth to be at least 11 in. before listed exceptions. Other choices use residential or nonmatching dimensions.
Why This Is the Correct Answer
IBC 1011.5.2 generally requires stair tread depth to be at least 11 in. before listed exceptions. Other choices use residential or nonmatching dimensions.
Why the Other Options Are Wrong
Option A: 9 in.
Choice A gives 9 in. Its specific error: 9 in. is an IBC dimensional value for a different stair, door, or egress condition.
Option C: 10 in.
In wood framing, 10 in. is the wrong selection for Egress stair treads: 10 in. is an IBC dimensional value for a different stair, door, or egress condition.
Option D: 12 in.
The trap in D is 12 in. That selection is wrong because 12 in. is an IBC dimensional value for a different stair, door, or egress condition.
Memory Technique
Use a stormwater map memory cue for egress stair treads: the stem's condition unlocks 11 in.
Reference Hint
Open International Building Code 2021 or 2024; use IBC 2021/2024 Section 1011.5.2 tread depth to confirm that IBC 1011.5.2 generally requires stair tread depth to be at least 11 in.
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