Garage Live Load - 2010 CBC

What should the live load be for an accessible attic in a detached garage? This is a 24’ square 2 car residential garage. The building official is claiming it should be 125 #/SF, based on this justification:

In section 406 “Motor-Vehicle-Related Occupancies” “U” occupancy classification is limited to single story buildings less than 1000 sq. ft. (increases up to 3000sq. ft. are allowed for conditions listed). Since there is no listing in the 1607.1 table for Parking Garage it is the determination of the Building Official that the use most similar would be warehouse because in chapter 3 “Use and Occupancy Classification” the code includes Parking Garages open and enclosed in the S-2 occupancy use group along with the rest of the low-hazard storage uses. “Storage warehouses” has two loading criteria. We have chosen to accept the lesser of those two loading criteria. To try to use 1607.1.27 is a misinterpretation of the Table as that loading is for areas within the Residential use. Even in previous codes (Table 16 A of the Uniform building Codes) there were separate loading criteria for the residential uses (private residences, apartment and hotel guest rooms).

The official has said that if the garage was attached to the house, the live load would fall under Table 1607.1.27 Residential, but with a detached garage, the attic suddenly becomes an S-2 Parking Garage. Is there a clear and reasonable guideline for the live load in this situation?

~Posted on behalf of MA

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The deciding factor is whether the area above the garage shown on your section as "attic" will be used for general storage or not.
Clearly the building is a group U occupancy if the detached garage is on a residential lot and is accessory to a residential home. As a prior Building Official, I feel the B.O. in this case has gone overboard. Now the question is whether any live load is adequate for the intended use. I would highly recommend that the floor be designed for 100psf live load if it will be used for general storage, the abuses or ignorance in the general population is an issue for garage ceiling storage and some heavy damages after collapse. (I have seen dozens over the years and it is a real issue).

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