Openings and spacing for open parking garage

[MrOrange]

The Existing: An urban open garage with perpendicular open sides. Openings run the length of the sides. Brick veneer projects 4'6" from deck, with open space to above.The Proposed: Infill development with 2 hour wall that abuts existing open garage wall. 4 stories, retail with 2 apartment floors above. Top apartment has 2 stories, so exit access is at 3 floor. (Basically a liner building retrofit.) Basic scheme approved by AHJ. As per 2009 IBC 406.3.3.3.1, openings must be 20% per tier, aggregate length must be 40% evenly spaced.The Question: Where do I find required clear space in front of said openings? Can I do lightwells with L shaped buildings? Any reason code does not allow me to use the openings as covered but open stairs to apartments? Any reason the 4'-6" between the brick veneer and the deck, which is open to above, wouldn't count as part of the opening?Me: First post to forum, newly minted architect with 10 years experience, none of which involved parking structures.

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[steveray]

Basically I think you are saying you would like to use an open stair on "new" building as ventilation for open garage per 406.3.3.3.1? Any lot lines involved? I have a gut issue with venting a garage into a stair, as far as a code section I can't think of anything hard and fast unless the stair is an actual exit, and even then it is a little gray....

And welcome to the forum!

SECTION 1020 EXITS

1020.1 General. Exits shall comply with Sections 1020 through 1026 and the applicable requirements of Sections 1003 through 1013. An exit shall not be used for any purpose that interferes with its function as a means of egress.

 

[jdfruit]

MrOrange: if there are lot lines there are difficulties. Building proximity to property line will severely impact both structures for fire rating and the "open" garage most likely will not qualify as "open" when new building constructed adjacent. If both buildings on same lot then still need fire walls based on occupancy separation. Open stairs to apartments are typically only allowed if there is adequate separation to property line or adjacent building. Light wells (or vent wells) may be the only viable solution. Good luck, let us know how things work through.

 

[MrOrange]

Steveray and jdfruit: Thanks for your replies. You are both on the right track. I realize my question(s) were not that clear. The AHJ has approved the general scheme where the new structures abut the existing with two hour walls. There are no lot lines, and it's in the CBD. AHJ referred me to 406.3.3.1 I've since realized I will need enclosed stairs, but I still don't understand how far they need to be from the openings. The code makes it sound like a very narrow "vent well" would be OK, but my gut says it's not that simple. As shown in my sketch, there already is a 4'-6" open air space between the building face and the actual deck.

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[jdfruit]

Here is a possible approach:

See "fire separation distance" definition in 702

Then wind through tables 601 & 602 with considering applicable code sections in 602.

Based on your sketch it appears you will need to establish a fire wall on the existing open parking garage as it is impacted by the new adjacent building

Fire wall on open parking garage impacts open area at adjacent building, wind through 406.3 to determine what may be required to get enough open area or revise to comply with mechanical vent ratios

The new building stairs will require wall fire rating based on distance in table