Building Height and Area Compliance with the California Building Code Presented by: Ara Sargsyan, PE, CBO, LEED AP Oakland, CA. January 29, 2013
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Learning Objectives •Understand California Building Code regulations related to building area and height limitations. •Analyze mixed occupancy buildings for different construction types. •Learn new techniques for calculating front increases and grade plane for complex building shapes and/or topography •Determine the most effective way to design buildings with optimal floor area, number of stories, height and construction type
Building Height and Area Limitations • • • • • • • •
Definitions (502) General Limitations (Table 503) Height (504) Mezzanines (505) Area Modifications (506) Unlimited Area Buildings (507) Mixed Use and Occupancy (508) Special Provisions (509)
Definitions • Grade Plane • Basement • Story Above Grade Plane • Building Height • Mezzanine
Grade Plane Definition A reference plane representing the average of finished ground level adjoining the building at exterior walls. Where the finished ground level slopes away from the exterior walls, the reference plane shall be established by the lowest points within the area between the building and the lot line or, where the lot line is more than 6 feet from the building, between the building and a point 6 feet from the building.
Methods of Determining the Grade Plane Elev. 12'
Elev. 12'
Weighted Average
1
3 15'-0"
10'-0"
Elev. 2'
Elev. 2'
2
4 5'-0"
30'-0"
GPE =
15’ 15’x12’ x12’ + 10’ 10’x(12’ x(12’+2’ +2’)/2 + 5’ 5’x2’ x2’ 30’ 30’
= 8.67’ 8.67’
Mezzanines (505) 2001 CBC Sec. 504.4 (UBC) – Unless considered as a separate story, the floor area of all mezzanines shall be included in calculating the allowable floor area of the stories in which the mezzanines are located.
2010 CBC Sec. 505.1(IBC) – mezzanines … shall be considered a portion of the story in which it is contained. Such mezzanines shall not contribute to either the building area or number of stories as regulated by Section 503.1
Table503
Height (504) Automatic sprinkler system Increase Installation of automatic sprinkler system with accordance to Section 903.3.1.1 (NFPA 13) allows a max. increase of: 20’ height increase to allowable height, and 1 additional story to allowable story
For Group R2 buildings of Type VA construction, max allowable increase: Restricted to total building height no more than 60’ Restricted to total building story height no more than 4 stories Height increase are allowed in addition to floor area increase in accordance to Section 506.3.
Height (504) Automatic sprinkler system Increase In other than Group A, E,H, I, L and R occupancies, high rise buildings, and other applications listed in Section 1.11 regulated by the Office of the State Fire Marshal (SMF), these increases are permitted in addition to area increase in accordance with Section 506.3.
Height Increase Not Allowed (504.2) Buildings with an Occupancy Group I 2 of Type IIB, III, IV or V construction. Buildings with an Occupancy Group H 1, H 2, H 3 or H 5. Fire resistance rating substitution in accordance with Table 601, Note d. Buildings with an Occupancy Group L. Buildings with licensed Group R 2.1 or R 4
55’+20’=75’
Table503
ax M
2+1=3
t gh i He 2 9,500
Sp r in kle rs
H IR EL A? Y
#
s ie r o St f o
No
ar ea In cr e as e
fo rF ire
es
Automatic Sprinkler System – Height Increase
Table503 50’+20’=70’ t gh i He #
s ie r to S of
H IR E
L NO A?
ax M
3+1=4
3 21,000
klers Sprin e r i F e for creas n I a e r OK A
Automatic Sprinkler System – Height Increase
Area Modification (506) Aa = {At + [At x If] +[At x Is]} (Equation 5 1) Equation for determining allowable area per story Aa (sq. ft) Tabular area per story as per Table 503 (At) Area increase due to frontage (If) Area increase due to installation of sprinkler system (Is)
Single basement need not be included in total allowable area basement does not exceed the permitted area for a building with no more than one story above grade plane No more than one basement level may be considered as not contributing to the total building area. All area in the other basement levels must be included in total building area count.
Area Increase Due to Frontage (506.2) Applicable to buildings with more than 25% of perimeter fronting on a public way or open space with minimum 20’ in width.
If = [F/P – 0.25]W/30
– I f = Area increase due to frontage. – F = Building perimeter that fronts on a public way or open space having 20 feet (6096 mm) open minimum width (feet). – P = Perimeter of entire building (feet). – W = Width of public way or open space (feet) in accordance with Section 506.2.1.
P. L
Area Increase Due to Frontage (506.2)
20'
30' 60' 40'
60'
30'
60'
10'
40'
30'
Ex i st
20'
20'
20'
ing
Bu
ild i
P.L.
50'
New Building
10' 10'
Approved Fire Line
120'
West St (60')
Open space shall be either on the same lot or dedicated for public use and shall be accessed from a street or approved fire line (506.2.2)
10'
P.L.
70'
If = [F/P – 0.25]W/30
.
ng
N P.L. South Ave (60')
Area Increase Due to Frontage (Building does not comply with 506.2.1 Exception)
70'
= 28.22’ P.L.
F = 295’
10'
P = 340’
If
20'
80'
20'
30'
New Building 60'
Ex is
tin g
P.L.
20'
60'
20'
20'
20'
30'
50' 10' 5' 5'
West St (60')
If = 0.58
20'
120'
If = [F/P – 0.25]W/30 = = [295/340 – 0.25] 28.22/30
30'
295
20'
8325
20'
W=
. P.L
20+80+30+60+20+20+5+10+50
30' 20' 10'
W=
20x(20+30)/2+80x30+30x20+60x30+20x30+20x(20+30)/2+5x(20+30)/2+10x30+50x30 20x(20+30)/2+80x30+30x20+60x30+20x30+20x(20+30)/2+5x(20+30)/2+10x30+50x30
Bu ild ing
0.75
N P.L. South Ave (60')
Area Increase Due to Frontage (Building complies with 506.2.1 Exception) 80x(20+60)/2+20x60+30x20+40x60+20x(60+50)/2+20x60+20x(30+20)/2+5x(20+30)/2+10x60+50x60 80x(20+60)/2+20x60+30x20+40x60+20x(60+50)/2+20x60+20x(30+20)/2+5x(20+30)/2+10x60+50x60 P.L
80+20+30+60+20+20+5+10+50
10'
P.L.
60'
F = 295’ P = 340’
80'
20'
20'
30'
New Building 60' 40'
20'
Ex i st ing
P.L.
20' 60'
60'
20'
20'
20'
50' 10' 5' 5'
West St (60')
If = 0.97 If < 1.5
20'
120'
If = [F/P – 0.25]W/30 = = [295/340 – 0.25] 47.20/30
70'
= 47.20’
30'
295
20'
13925
.
20'
W=
30' 20' 10'
W=
Bu ild ing
N P.L. South Ave (60')
Area Increase Due to Automatic Sprinklers (506.3) When a building is equipped with automatic sprinkler system as per Section 903.3.1.1 (NFPA 13), the area limitation per Table 503 is permitted to be increased as followed: Increase by 200%, Is = 2 for multi story buildings Increase by 300%, Is= 3 for single story buildings
In other than high rise buildings, Group A, E,H, I, L and R occupancies or other applications listed in Section 1.11 regulated by SFM Area increase allowed in addition to height and story increases For Group R2 buildings of Type VA construction, the area increase allowed in addition to height and story increases
Exceptions to Area Increase (506.3) Sprinklers system shall not be used to increase the area for the following conditions: Buildings with an occupancy in Use Group H 1. The floor area of an occupancy in Use Group H 2 or H 3. For mixed use buildings containing such occupancies, the allowable area shall be calculated as separated occupancy per Section 508.3.3.2, with the sprinkler increase applicable only to the portions of the building not classified as Use Group H 2 or H 3.
Fire resistance rating substitution as per Table 601, Note d. [SFM] Buildings in Group L occupancies.
Area Determination (506.4) Total Building Allowable Area (for single occupancy group) For Group A, E,H, I, L and R occupancies, high rise buildings, or other applications listed in Section 1.11 regulated by SFM For building >1 story above grade plane, multiply Aa by 2. No story shall exceed Aa for the occupancies on that story
For other than Group A, E,H, I, L and R occupancies, high rise buildings, or other applications listed in Section 1.11 regulated by SFM For building 2 stories above grade plane, multiply Aa by 2 For building >2 stories above grade plane, multiply by Aa by 3. No story shall exceed Aa for the occupancies on that story.
Area Determination Mixed Occupancies (506.4.1)
Nonseparated … Aa shall be based on most restrictive provision for each occupancy when the mixed occupancies are treated as nonseparated occupancy (508.3.2)
“Most Restrictive”
Table503
“Most Restrictive”
Area Limitations Mixed Occupancies Separated… Each story… (508.4.2) In each story, the building area shall be such that the sum of the ratios of the actual floor area of each occupancy divided by the allowable area of each occupancy shall not exceed one. (508.3.3) Actual area
+
Allowable area (Aa)
Actual area
+ Allowable area (Aa)
…
1 for each floor
Area Limitations Mixed Occupancies Separated… Entire Building… (506.5) For other than Group A, E,H, I, L and R occupancies, high rise buildings, or other applications listed in Section 1.11 regulated by SFM, the sum shall not exceed 2 for 2 stories building and 3 for buildings 3 stories or higher Actual area
+
Allowable area (Aa) Actual area Allowable area (Aa)
+
Actual area
+ Allowable area (Aa) Actual area
+ Allowable area (Aa)
…
…
2 for 2-stories building
3 for 3-stories building or higher
Area Limitations Mixed Occupancies Separated… Entire Building… (506.5) For Group A, E,H, I, L and R occupancies, high rise buildings, or other applications listed in Section 1.11 regulated by SFM, the sum shall not exceed 2 for buildings 2 stories or higher. Actual area Allowable area (Aa)
+
Actual area
+ Allowable area (Aa)
…
2 for 2-stories building or higher
Mixed Use and Occupancy (508) Accessory Occupancies (508.2) • Area limitations. Aggregate accessory occupancies shall not occupy more than 10 percent of the building area of the story in which they are located and shall not exceed the tabular values in Table 503, without building area increases in accordance with Section 506 for such accessory occupancies. • Occupancy classification. Accessory occupancies shall be individually classified in accordance with Section 302.1. The requirements of this code shall apply to each portion of the building based on the occupancy classification of that space. • Allowable building area and height. The allowable building area and height of the building shall be based on the allowable building area and height for the main occupancy in accordance with Section 503.1. The height of each accessory occupancy shall not exceed the tabular values in Table 503, without increases in accordance with Section 504 for such accessory occupancies.
Incidental Accessory Occupancies (508.2.5)
Nonseparated Occupancies (508.3) • Occupancy classification. Nonseparated occupancies shall be individually classified in accordance with Section 302.1. The requirements of this code shall apply to each portion of the building based on the occupancy classification of that space except that the most restrictive applicable provisions of Section 403 and Chapter 9 shall apply to the building or portion thereof in which the nonseparated occupancies are located. • Allowable building area and height. The allowable building area and height of the building or portion thereof shall be based on the most restrictive allowances for the occupancy groups under consideration for the type of construction of the building in accordance with Section 503.1. • Separation. No separation is required between nonseparated occupancies. Exceptions: – Group H 2, H 3, H 4, H 5, I 2, I 2.1, I 3 and L occupancies – Group R 1, R 2, R 2.1 and R 3 dwelling units and sleeping units
Separated Occupancies (508.4) • Each separated occupancy shall comply with the building height limitations based on the type of construction of the building in accordance with Section 503.1. • Exception: Special provisions permitted by Section 509.
• Individual occupancies shall be separated from adjacent occupancies as per Table 508.4 • Required separations shall be fire barriers constructed as per Section 707 or horizontal assemblies constructed as per Section 712, or both, so as to completely separate adjacent occupancies.
Table 508.4
Unlimited Area Buildings (507) Buildings surrounded and adjoined by public ways or yards not less than 60 feet: • • • • • • • • •
Nonsprinklered, 1 story, Group F 2 or S 2 buildings (507.2) Sprinklered, 1 or 2 story, Group B, F, M or S buildings (507.3,4) Mixed occupancy buildings with Groups A 1 and A 2. (507.3.1) Group A 3 buildings (507.6,7) Group H 2, H 3 and H 4 occupancies (507.8) H 2 Aircraft paint hangars (507.9) Group E buildings (507.10) Motion picture theaters (507.11) Covered mall buildings and anchor stores (507.12)
Unlimited Area Buildings (507) Reduced Open Space (507.5) • The public ways or yards of 60 feet in width shall be permitted to be reduced to not less than 40 feet in width provided all of the following requirements are met: – The reduced width shall not be allowed for more than 75 percent of the perimeter of the building. – The exterior walls facing the reduced width shall have a minimum fire resistance rating of 3 hours. – Openings in the exterior walls facing the reduced width shall have opening protectives with a minimum fire protection rating of 3 hours.
Special Provisions (509) • Horizontal building separation allowance (509.2) • 509.3 Group S 2 enclosed parking garage with Group S 2 open parking garage above (509.3) • Open parking garage beneath Groups A, I, B, M and R (509.7) • Group B or M with Group S 2 open parking garage (509.8) • Multiple buildings above Group S 2 parking garages (509.9)
Questions? This concludes The American Institute of Architects Continuing Education Systems Course Ara Sargsyan, PE, CBO, LEED AP www.ara4help.com
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