walker.t
SAWHORSE
The 2021 IBC commentary on 506.2.2 Mixed-Occupancy Buildings, Example 3 on Page 5-20, works through a four-story building which has different types of mixed occupancy on the different floors. I worked through this example then read the commentary and disagreed with their conclusion that the third floor can be considered nonseparated occupancy. In their analysis they only discuss the allowable areas but don’t discuss allowable number of stories, I think the third floor should be separated occupancy because it has an F-1 occupancy in a 4-story building.
Wanted to see if anyone could confirm if allowable stories should be ignored when determining if this floor is nonseparated or separated occupancy.
Building data:
Type IIB
4 stories.
Sprinklered.
No frontage increase.
Third story has the following:
Group B, 15,000 s.f.
Group S-1, 15,000 s.f.
Group F-1, 15,000 s.f.
Commentary for this story: “The third story qualifies as a nonseparated occupancy since the allowable area per story for the most restrictive occupancy (Group F-1; 46,500 s.f.) is larger than the actual area on any individual story. The ratio of the floor is 0.97 (45,000/46,500.)” They don’t say anything about allowable number of stories.
Seems to me that they are ignoring how F-1 is limited to 3 stories per Table 504.4. Per 508.3.2, allowable building area, height, and number of stories of the “building or portion thereof shall be based on the most restrictive allowances for the occupancy groups under consideration.” Because this is a four story building, I would have thought that the third floor as described would have been considered separated occupancy because the building exceeds the allowable number of stories for the F-1 occupancy.
I don’t have a problem that an F-1 occupancy is in a four-story mixed occupancy building, my understanding is that this is permitted as long at the F-1 occupancy is not higher than the third floor per 508.4.3.
Wanted to see if anyone could confirm if allowable stories should be ignored when determining if this floor is nonseparated or separated occupancy.
Building data:
Type IIB
4 stories.
Sprinklered.
No frontage increase.
Third story has the following:
Group B, 15,000 s.f.
Group S-1, 15,000 s.f.
Group F-1, 15,000 s.f.
Commentary for this story: “The third story qualifies as a nonseparated occupancy since the allowable area per story for the most restrictive occupancy (Group F-1; 46,500 s.f.) is larger than the actual area on any individual story. The ratio of the floor is 0.97 (45,000/46,500.)” They don’t say anything about allowable number of stories.
Seems to me that they are ignoring how F-1 is limited to 3 stories per Table 504.4. Per 508.3.2, allowable building area, height, and number of stories of the “building or portion thereof shall be based on the most restrictive allowances for the occupancy groups under consideration.” Because this is a four story building, I would have thought that the third floor as described would have been considered separated occupancy because the building exceeds the allowable number of stories for the F-1 occupancy.
I don’t have a problem that an F-1 occupancy is in a four-story mixed occupancy building, my understanding is that this is permitted as long at the F-1 occupancy is not higher than the third floor per 508.4.3.