Scott555 wrote:Thanks....although I am getting a lot of resistance because of section 509.2. Doesn't this section require type 1 construction making the ceiling/floor construction require steel or concrete only? Or am I missing something?
Or unless I am missing something (like everyone, I miss things too), so let's go through 509.2 and seem then continue with other sections to find out what, if anything, I am missing. (bold and underlining are mine)
- 509.2 Group S-2 enclosed or open parking garage with Group A, B, M, R or S above. A basement and/or the first story above grade plane of a building
shall be considered as a separate and distinct building for the purpose of determining area limitations, continuity of fire walls, limitation of number of stories and type of construction
when all of the following conditions are met: (
Jerry's note: Unless I am missing something, you are not considering this a separate and distinct building, right? Or did I miss that in the first information you provided? If I did not miss that in the first information you provided, this entire section does not apply.)
- - 1. The basement and/or the first story above grade plane is of Type IA construction and is separated from the building above with a horizontal assembly having a minimum 3-hour fire-resistance rating.
- - 2. Shaft, stairway, ramp or escalator enclosures through the horizontal assembly shall have not less than a 2-hour fire-resistance rating with opening protectives in accordance with Table 715.4.
- - - Exception: Where the enclosure walls belowthe horizontal assembly have not less than a 3-hour fire-resistance rating with opening protectives in accordance with Table 715.4, the enclosure walls extending above the horizontal assembly shall be permitted to have a 1-hour fire-resistance rating, provided:
- - - - 1. The building above the horizontal assembly is not required to be of Type I construction;
- - - - 2. The enclosure connects less than four stories;
- - - - and
- - - - 3. The enclosure opening protectives above the horizontal assembly have a minimum 1-hour fire protection rating.
- - - 3. The building above the horizontal assembly shall be permitted to have multiple GroupAuses, each with an occupant load of less than 300, or Group B, M, R or S uses.
- - - 4. The building below the horizontal assembly is a Group S-2 enclosed or open parking garage, used for the parking and storage of private motor vehicles.
- - - - Exceptions:
- - - - - 1. Entry lobbies, mechanical rooms and similar uses incidental to the operation of the building shall be permitted.
- - - - - 2. Multiple Group A uses, each with an occupant load of less than 300, or Group B or M uses shall be permitted, in addition to those uses incidental to the operation of the building (including storage areas), provided that the entire structure below the horizontal assembly is protected throughout by an approved automatic sprinkler system.
- - - 5. The maximum building height in feet shall not exceed the limits set forth in Section 503 for the building having the smaller allowable height as measured from the grade plane.
The above section is used when a choice is made to consider the area (basement or first story above grade) as a separate and distinct structure, did I miss that in your first information?
Table 503, for Type VA type of construction to be used for Group R2 use, allows 3 stories and 12,000 square feet per story.
Section 504.2, for Group R2 which is fully sprinklered with an automatic sprinkler system which meets 903.3.1.2, allows an increase in height of 20 feet and the maximum number of stories is increased by 1 story, i.e., Table 503 allows 3 stories, 1 additional story is allowed for the sprinkler system, which makes 4 stories.
- TABLE 503
- - ALLOWABLE HEIGHT AND BUILDING AREASa
- - -
Height limitations shown as stories and feet above grade plane.
- - - Area limitations as determined by the definition of “Area, building,” per story
- STORY ABOVE GRADE PLANE. Any story having its finished floor surface entirely above grade plane, except that a basement shall be considered as a story above grade plane where the finished surface of the floor above the basement is:
- - 1. More than 6 feet (1829 mm) above grade plane; or
- - 2. More than 12 feet (3658 mm) above the finished ground level at any point
As I understand your description, you plan on having 4 stories "above grade plane", right? Table 503, with the increase allowed by 504.2, allows 3+1=4 stories "above grade plane" for Type VA and R2 use. As such, at this point there is no need to consider the S2 occupancy as a "separate and distinct structure" and thus no reason, to this point, to apply section 509.2.
Section 506 addresses area modifications, with 506.3 addressing the automatic sprinkler system increase. The automatic sprinkler system allows the area per story to be increased by and
additional 200 percent with more than one story above grade, i.e., 12,000 sf + 24,000 sf 200% additional = 36,000 sf per story. Again, no fire-resistance rating substitution in accordance with Table 601, Note e is allowed.
Section 506.4 has a limiting affect on the maximum area of a building with more than one story above grade: two stories above grade and the maximum area per story is multiplied by 2, i.e., a two story above grade building would have 36,000 sf x 2 = 72,000 sf maximum for the building; three or more stories about grade and the maximum area per story is multiplied by 3, i.e., a 4 four story above grade building would have 36,000 sf x 3 = 108,000 sf (not the 144,000 sf one might expect). There are some exceptions to this section, such for unlimited area building and those with the appropriate automatic sprinkler system, which means such a sprinklered building would be allowed the 144,000 sf (36,000 sf x 4 stories = 144,000 sf).
Section 506.4.1 addresses mixed occupancies, this further modifies and limits the above in accordance with sections 508.3.2 and 508.3.3.
Section 508 addresses mixed use and occupancy, which you have, the most restrictive of the occupancies control, and the R2 numbers used above are more restrictive than the S2 numbers would have been, thus no need to recalculate the numbers using the S2 occupancy.
Unless I missed something going through the above, I see no need to consider the two occupancies as distinct and separate buildings, thus 509.2 would not be applicable.
Where you able to follow through the above, if so, what was your outcome?