Openings in lieu of mechanical ventilation for enclosed parking garages

[RLGA]

2012 IBC is applicable.

Has anyone ever submitted for approval (alternate method) or approved the use of openings per Section 406.5.2 for open parking garages in lieu of the mechanical ventilation per Section 406.6.2 for enclosed parking garages?

I have an apartment building with a small single-story parking garage that is below and adjacent to the dwelling units. The building is Type VB nonseparated occupancies, but the parking garage is unprotected steel. Section 510.7 could possibly be used with the dwelling units classified as Type VB and the parking garage considered an open parking garage and classified as Type IIB. However, Section 510.7.1 appears to require fire barriers and horizontal assemblies for occupancy separations per Table 508.4, which would require the supporting construction of the horizontal assembly to have an equal rating. Since the designer does not want the steel protected, the IBC only requires dwelling unit separation per Section 420, which does not require supporting construction to have an equal rating (Section 711.4, Exception, Item #2).

Thus, leading to my question. If the special provision of Section 510.7 cannot be used and the parking garage is of Type VB construction per the rest of the structure, then it cannot be considered an open parking garage (required to be of Type I, II, or IV construction per Section 406.5.1) and must be considered an enclosed parking garage. Enclosed parking garages are required to have mechanical ventilation per Section 406.6.2. But if open parking garages, with their required minimum openings are not required to have mechanical ventilation, why couldn't enclosed parking garages use the opening requirements of Section 405.5.2 in lieu of the mechanical ventilation?

 

[mtlogcabin]

Will 406.3 work for your project?

 

[RLGA]

mtlogcabin: Not really, the garage is larger than 3,000 sq. ft. and, because of the design, cannot be divided into individual 3,000 sq. ft. areas by fire walls.

 

[mtlogcabin]

Bummer.

How about in-tumescent paint for the rating of the steel structure

 

[zigmark]

Ron-

I think I get what you're trying to ask but it brings up a question I can't get around... Is the structure an enclosed or an open parking garage? You seem to say it is enclosed but want to create openings as if it were an open parking garage. You have to pick which requirements you want to play by they all work only in conjunction with each other as they apply. I realize I'm preaching to the choir here as I have read many of your posts. If open it is protected if enclosed it is mechanically ventilated. Maybe someone could provide the discussion from "way back" about how they settled on these provisions. Could you provide enough opening to accomplish natural ventilation but not enough for the building to be considered open as an alternate method? May want to talk to the AHJ about that one. What are the owners hang-ups about protecting the structure since that's what it takes to get a code compliant structure? Or was this something caught after the design was finished?

ZIG

 

[RLGA]

The requirement limiting construction types to I, II, or IV seems somewhat nonsensical if the area and height are limited to the requirements of Chapter 5, but enclosed parking garages can be of ANY construction type and are limited to the same height and area requirements of Chapter 5. The only difference is that one has openings and the other doesn't, but is provided with mechanical ventilation. If either of those two garage types would require more protection it seems like the enclosed parking garage would because it is more hazardous being enclosed. The only reason that an open parking garage should be limited to the construction types indicated would be because of the single use application per Section 406.5.4.1 (which allows much greater area and height).

 

[Paul Sweet]

Could you use heavy timber (type IV) construction for the garage, as allowed by 510.4? Table 508.4 requires only 1-hour separation if the building is sprinklered. The heavy timber members could be oversized if necessary to achieve the fire rating.

A firm I used to work for sometimes had to do this for McMansions at the beach. FEMA required the first floor to be raised 10' or more and be open for floods. With 3 stories on top of that they exceeded the height limit for IRC so we had to use the IBC.

 

[RLGA]

It would work theoretically, but this is in Phoenix, Arizona, where exposed wood does not hold up very well and requires a lot of maintenance.