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Opinion: BAM R2 U Code Opinion

To:

Ms. Pamela Perri Weaver
Builders Association Minnesota
570 Asbury Street,  Suite 301
St. Paul,  MN  55104

From:

Thomas R. Joachim
State Building Official

Subject:

BAM R2 U Code Opinion

Date:

May 29, 2003

 

Dear Ms. Perri Weaver:

This letter is in response to your request for an opinion on the application of the 2003 Minnesota State Building Code (MSBC) and the 2000 International Building Code (IBC) with regards to the provisions for separating multiple private garages within an R-2 occupancy.

To qualify our opinion, I would like to point out the specifics referenced in your letter. Questions relate to a type V-B, two-story, 10-unit, R-2 occupancy that has been designed with multiple attached 2-car private garages, each of which serves one of the individual dwelling units within the building. Each dwelling (and its respective garage) is defined by a 1-hour fire-partition tenant separation wall around its perimeter. Dwelling units are not stacked, but are designed side-by-side and back to back. Dwellings share no common space within the building.

As I understand it, your question relates to the "separated" or "non-separated" use design concept new to the Minnesota code. The gist of your question is: for the purposes of determining proper/required occupancy separations, should the private garages be considered a complete and separate occupancy based on their cumulative area within the building, or should they be considered multiple (minor/accessory) group U occupancies within the larger and major use, which is the R-2.

In the design referenced, the Division contends that the building should be classified as a "separated" group R-2 occupancy that contains numerous, yet minor, group U uses within the building. We believe, for the purposes of applying mixed occupancy provisions of the code, that the proper occupancy separation would be that as mandated by IBC Table 302.3.3, which requires a 1-hour occupancy (fire-barrier) separation. The dwellings and their garages, in-turn, must be separated from each other by a 1-hour fire-resistive tenant separation wall (fire-partition) per IBC Section 310.3.

For the purposes of determining allowable area in a building containing mixed occupancies, under general provisions of the code, one is normally required to add the cumulative area of each occupancy together to run through the allowable area computations. In this instance however, IBC Section 406.1.1 supersedes the general requirement by providing for specific conditions which are applicable only to group U private garages. IBC Section 406.1.1 implies that group U occupancies can be analyzed as individual buildings, or as "parts" of larger mixed occupancy buildings. The garages referenced herein seem to meet those provisions. We support this interpretation due in part to the fact that each garage is privately accessed and that the actual size of each garage is limited to a very small area within each dwelling unit. With additional requirements mandating 1-hour dwelling unit separations, which further define the boundary of each dwelling and respective private garage, there is simply a greater degree of safety provided, and as such, recognized. In our opinion, item 1 of IBC Section 406.1.2 should be applied. This section indicates that the primary or major occupancy use group should be used for determination of allowable area. In this case, we are talking about the R-2 occupancy. The R-2 type V-B construction, along with area increases permitted by Chapter 5, would dictate actual/maximum building size. The number and/or area of the individual private garages would have nothing to do with the building's allowable area in this case.

The question of applying exception 2 (and possibly 3) of section 302.3.3, which allows for a 1/2" gypsum separation between the garage and the dwelling is unfortunately, inappropriate. This is supported by footnote "g" found in Table 302.3.3. Footnote "g," in this case, references one back to the exceptions in question. However, footnote "g" is only applicable to S-2, R-3 and R-4 occupancies - not R-2. This also supports our theory that the exceptions found under section 302.3.3 are erroneously placed there and that they are not exceptions to "section" 302.3.3, but language placed there for reference from the footnotes to "Table" 302.3.3.

In summary, for this application, the building should be considered a "separated" use design containing a group R-2 and a group U occupancy. The private garages must be separated from individual dwelling units by a 1-hour fire-barrier (occupancy separation) and each dwelling must be separated from each other by 1-hour fire-partitions at common party walls. The private garages may be located next to each other and be constructed up to 1000 square feet in area (individually), provided they are accessed by only one dwelling unit/tenant and are separated by 1-hour fire-partition separations at common tenant demising wall locations within the building. The basic allowable area of the building (type V-B) is 7000 square feet plus the increases allowed for frontage increases pursuant to IBC section 506.

In conclusion, I would like to point out that there are many versions of this type of multi-family building design. With that understanding, it should be noted that a design deviation for something seemingly as simple as adding property lines between the units, stacking dwelling units, or changing the U occupancy to a common or shared use area within the building, etc., would each have a major impact on the application of the code. One of those same variables could change our opinion/position on this very same matter.

I hope this information helps you settle this issue. If you have any questions, please feel free to call me at 651-296-9928.

Sincerely, BUILDING CODES AND STANDARDS DIVISION

Thomas R. Joachim State Building Official

TRJ/prh Enc.

cc: Steve Hernick, Assistant Director Tom Anderson, Assistant Director Scott McLellan, Supervisor, Plan review and Regional Services Mike Godfrey, Supervisor, Education and Certification

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