A-3 occupancy in 4th floor Type VA building

[ElArch]

I am working in a 4 story multifamily project. There is a 850sf roof deck in 4th floor. The occupancy of the roof deck is A-3.
The construction type is VA.
However according to Table 504.4 the allowable number of story for A-3 is 2 or 3 stories. Can I have the roof deck in 4th floor? I did a similar type VA project about 10 years ago with roof deck in 4th floor.
In table 504.4 there is S(without area increase) and S(with area increase). What does "without area increase" and "with area increase" mean?
Thanks!

 

[Jay Smith]

Allowable height for accessory occupancies is in accordance with section 504 for the main occupancy. See 2018 IBC 508.2.

 

[Tim Mailloux]

Allowable height for accessory occupancies is in accordance with section 504 for the main occupancy. See 2018 IBC 508.2.

This only applies to accessory occupancies, without knowing how large the floor is we dont know if this roof deck exceeeds the 10% threshold for an accessory occupancy.

 

[Sifu]

Hmmm. You say "in the 4th floor". Maybe? IBC 503.1.4 allows an occupied roof as long as the occupancy is permitted on the story below. T504.4 allows an A-3 on the 3rd story in a VB, sprinklered building. So if it is an occupied roof, then I think it might fly.

 

[Jay Smith]

Another thought - If the assembly space can be reduced to less than 750 SF it becomes Group B which is allowed on the 4th in Type VA per Table 504.4 or part of the main occupancy per 303.1.2.

 

[Tim Mailloux]

Another thought - If the assembly space can be reduced to less than 750 SF it becomes Group B which is allowed on the 4th in Type VA per Table 504.4 or part of the main occupancy per 303.1.2.

its 750 SF or 50 people.....if the entire roof deck is tables and chairs the 1 per 15 calculation for a space under 750sf gets your there. But if you have any open standing space the AHJ may require you to use the 1 per 7 or 1 per 5 calculation for those portions of the deck getting your occuapnt load well above 50 people.

 

[Tim Mailloux]

An acessory A3 isnt a problem on the 4th floor provided it qualifies and an accessory use and is less than 10% of the floor area. What is the area of your 4th floor?

 

[Jay Smith]

its 750 SF or 50 people.....if the entire roof deck is tables and chairs the 1 per 15 calculation for a space under 750sf gets your there. But if you have any open standing space the AHJ may require you to use the 1 per 7 or 1 per 5 calculation for those portions of the deck getting your occuapnt load well above 50 people.

Agreed on this and your previous reply to me, but I think we can reasonably suggest an answer based on what the amenity deck of a new 4-story apartment building normally looks like. This is a very common project type that usually has stories far larger than 10 times this proposed deck and usually has a common area like this with tables and chairs. Under codes like 2009 IBC it was usually solved by classifying it as Group B. Under more recent codes it is solved either the same way or as an accessory occupancy.

 

[Jay Smith]

Agreed on this and your previous reply to me, but I think we can reasonably suggest an answer based on what the amenity deck of a new 4-story apartment building normally looks like. This is a very common project type that usually has stories far larger than 10 times this proposed deck and usually has a common area like this with tables and chairs. Under codes like 2009 IBC it was usually solved by classifying it as Group B or part of the main occupancy. Under more recent codes it is solved either the same way or as an accessory occupancy.

Correction to my comment.