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Section 506 Building Area

Building Code 2021 of Illinois > 5 General Building Heights and Areas > 506 Building Area
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506.1 General
The floor area of a building shall be determined based on the type of construction, occupancy classification, whether there is an automatic sprinkler system installed throughout the building and the amount of building frontage on public way or open space.
506.1.1 Unlimited Area Buildings
Unlimited area buildings shall be designed in accordance with Section 507.
506.1.2 Special Provisions
The special provisions of Section 510 permit the use of special conditions that are exempt from, or modify, the specific requirements of this chapter regarding the allowable areas of buildings based on the occupancy classification and type of construction, provided the special condition complies with the provisions specified in Section 510.
506.1.3 Basements
Basements need not be included in the total allowable floor area of a building provided the total area of such basements does not exceed the area permitted for a one-story above grade plane building.
506.2 Allowable Area Determination
The allowable area of a building shall be determined in accordance with the applicable provisions of Sections 506.2.1, 506.2.2 and 506.3.
TABLE 506.2
ALLOWABLE AREA FACTOR (At = NS, S1, S13R, S13D or SM, as applicable) IN SQUARE FEETa, b
OCCUPANCY CLASSIFICATION SEE FOOTNOTES TYPE OF CONSTRUCTION
Type I Type II Type III Type IV Type V
A B A B A B A B C HT A B
A-1 NS UL UL 15,500 8,500 14,000 8,500 45,000 30,000 18,750 15,000 11,500 5,500
S1 UL UL 62,000 34,000 56,000 34,000 180,000 120,000 75,000 60,000 46,000 22,000
SM UL UL 46,500 25,500 42,000 25,500 135,000 90,000 56,250 45,000 34,500 16,500
A-2 NS UL UL 15,500 9,500 14,000 9,500 45,000 30,000 18,750 15,000 11,500 6,000
S1 UL UL 62,000 38,000 56,000 38,000 180,000 120,000 75,000 60,000 46,000 24,000
SM UL UL 46,500 28,500 42,000 28,500 135,000 90,000 56,250 45,000 34,500 18,000
A-3 NS UL UL 15,500 9,500 14,000 9,500 45,000 30,000 18,750 15,000 11,500 6,000
S1 UL UL 62,000 38,000 56,000 38,000 180,000 120,000 75,000 60,000 46,000 24,000
SM UL UL 46,500 28,500 42,000 28,500 135,000 90,000 56,250 45,000 34,500 18,000
A-4 NS UL UL 15,500 9,500 14,000 9,500 45,000 30,000 18,750 15,000 11,500 6,000
S1 UL UL 62,000 38,000 56,000 38,000 180,000 120,000 75,000 60,000 46,000 24,000
SM UL UL 46,500 28,500 42,000 28,500 135,000 90,000 56,250 45,000 34,500 18,000
A-5 NS UL UL UL UL UL UL UL UL UL UL UL UL
S1
SM
B NS UL UL 37,500 23,000 28,500 19,000 108,000 72,000 45,000 36,000 18,000 9,000
S1 UL UL 150,000 92,000 114,000 76,000 432,000 288,000 180,000 144,000 72,000 36,000
SM UL UL 112,500 69,000 85,500 57,000 324,000 216,000 135,000 108,000 54,000 27,000
E NS UL UL 26,500 14,500 23,500 14,500 76,500 51,000 31,875 25,500 18,500 9,500
S1 UL UL 106,000 58,000 94,000 58,000 306,000 204,000 127,500 102,000 74,000 38,000
SM UL UL 79,500 43,500 70,500 43,500 229,500 153,000 95,625 76,500 55,500 28,500
F-1 NS UL UL 25,000 15,500 19,000 12,000 100,500 67,000 41,875 33,500 14,000 8,500
S1 UL UL 100,000 62,000 76,000 48,000 402,000 268,000 167,500 134,000 56,000 34,000
SM UL UL 75,000 46,500 57,000 36,000 301,500 201,000 125,625 100,500 42,000 25,500
F-2 NS UL UL 37,500 23,000 28,500 18,000 151,500 101,000 63,125 50,500 21,000 13,000
S1 UL UL 150,000 92,000 114,000 72,000 606,000 404,000 252,500 202,000 84,000 52,000
SM UL UL 112,500 69,000 85,500 54,000 454,500 303,000 189,375 151,500 63,000 39,000
H-1 NSc 21,000 16,500 11,000 7,000 9,500 7,000 10,500 10,500 10,500 10,500 7,500 NP
S1
H-2 NSc 21,000 16,500 11,000 7,000 9,500 7,000 10,500 10,500 10,500 10,500 7,500 3,000
S1
SM
H-3 NSc UL 60,000 26,500 14,000 17,500 13,000 25,500 25,500 25,500 25,500 10,000 5,000
S1
SM
H-4 NSc, d UL UL 37,500 17,500 28,500 17,500 72,000 54,000 40,500 36,000 18,000 6,500
S1 UL UL 150,000 70,000 114,000 70,000 288,000 216,000 162,000 144,000 72,000 26,000
SM UL UL 112,500 52,500 85,500 52,500 216,000 162,000 121,500 108,000 54,000 19,500
H-5 NSc, d UL UL 37,500 23,000 28,500 19,000 72,000 54,000 40,500 36,000 18,000 9,000
S1 UL UL 150,000 92,000 114,000 76,000 288,000 216,000 162,000 144,000 72,000 36,000
SM UL UL 112,500 69,000 85,500 57,000 216,000 162,000 121,500 108000 54,000 27,000
I-1 NSd, e UL 55,000 19,000 10,000 16,500 10,000 54,000 36,000 18,000 18,000 10,500 4,500
S1 UL 220,000 76,000 40,000 66,000 40,000 216,000 144,000 72,000 72,000 42,000 18,000
SM UL 165,000 57,000 30,000 49,500 30,000 162,000 108,000 54,000 54,000 31,500 13,500
I-2 NSd, f UL UL 15,000 11,000 12,000 NP 36,000 24,000 12,000 12,000 9,500 NP
S1 UL UL 60,000 44,000 48,000 NP 144,000 96,000 48,000 48,000 38,000 NP
SM UL UL 45,000 33,000 36,000 NP 108,000 72,000 36,000 36,000 28,500 NP
I-3 NSd, e UL UL 15,000 10,000 10,500 7,500 36,000 24,000 12,000 12,000 7,500 5,000
S1 UL UL 60,000 40,000 42,000 30,000 144,000 96,000 48,000 48,000 30,000 20,000
SM UL UL 45,000 30,000 31,500 22,500 108,000 72,000 36,000 36,000 22,500 15,000
I-4 NSd, g UL 60,500 26,500 13,000 23,500 13,000 76,500 51,000 25,500 25,500 18,500 9,000
S1 UL 121,000 106,000 52,000 94,000 52,000 306,000 204,000 102,000 102,000 74,000 36,000
SM UL 181,500 79,500 39,000 70,500 39,000 229,500 153,000 76,500 76,500 55,500 27,000
M NS UL UL 21,500 12,500 18,500 12,500 61,500 41,000 26,625 20,500 14,000 9,000
S1 UL UL 86,000 50,000 74,000 50,000 246,000 164,000 102,500 82,000 56,000 36,000
SM UL UL 64,500 37,500 55,500 37,500 184,500 123,000 76,875 61,500 42,000 27,000
R-1h NSd UL UL 24,000 16,000 24,000 16,000 61,500 41,000 25,625 20,500 12,000 7,000
S13R
S1 UL UL 96,000 64,000 96,000 64,000 246,000 164,000 102,500 82,000 48,000 28,000
SM UL UL 72,000 48,000 72,000 48,000 184,500 123,000 76,875 61,500 36,000 21,000
R-2h NSd UL UL 24,000 16,000 24,000 16,000 61,500 41,000 25,625 20,500 12,000 7,000
S13R
S1 UL UL 96,000 64,000 96,000 64,000 246,000 164,000 102,500 82,000 48,000 28,000
SM UL UL 72,000 48,000 72,000 48,000 184,500 123,000 76,875 61,500 36,000 21,000
R-3h NSd UL UL UL UL UL UL UL UL UL UL UL UL
S13D
S13R
S1
SM
R-4h NSd UL UL 24,000 16,000 24,000 16,000 61,500 41,000 25,625 20,500 12,000 7,000
S13D
S13R
S1 UL UL 96,000 64,000 96,000 64,000 246,000 164,000 102,500 82,000 48,000 28,000
SM UL UL 72,000 48,000 72,000 48,000 184,500 123,000 76,875 61,500 36,000 21,000
S-1 NS UL 48,000 26,000 17,500 26,000 17,500 76,500 51,000 31,875 25,500 14,000 9,000
S1 UL 192,000 104,000 70,000 104,000 70,000 306,000 204,000 127,500 102,000 56,000 36,000
SM UL 144,000 78,000 52,500 78,000 52,500 229,500 153,000 95,625 76,500 42,000 27,000
S-2 NS UL 79,000 39,000 26,000 39,000 26,000 115,500 77,000 48,125 38,500 21,000 13,500
S1 UL 316,000 156,000 104,000 156,000 104,000 462,000 308,000 192,500 154,000 84,000 54,000
SM UL 237,000 117,000 78,000 117,000 78,000 346,500 231,000 144,375 115,500 63,000 40,500
U NSi UL 35,500 19,000 8,500 14,000 8,500 54,000 36,000 22,500 18,000 9,000 5,500
S1 UL 142,000 76,000 34,000 56,000 34,000 216,000 144,000 90,000 72,000 36,000 22,000
SM UL 106,500 57,000 25,500 42,000 25,500 162,000 108,000 67,500 54,000 27,000 16,500
For SI: 1 square foot = 0.0929 m2.
UL = Unlimited; NP = Not Permitted; NS = Buildings not equipped throughout with an automatic sprinkler system; S1 = Buildings a maximum of one story above grade plane equipped throughout with an automatic sprinkler system installed in accordance with Section 903.3.1.1; SM = Buildings two or more stories above grade plane equipped throughout with an automatic sprinkler system installed in accordance with Section 903.3.1.1; S13R = Buildings equipped throughout with an automatic sprinkler system installed in accordance with Section 903.3.1.2; S13D = Buildings equipped throughout with an automatic sprinkler system installed in accordance with Section 903.3.1.3.
  1. See Chapters 4 and 5 for specific exceptions to the allowable area in this chapter.
  2. See Section 903.2 for the minimum thresholds for protection by an automatic sprinkler system for specific occupancies.
  3. New Group H occupancies are required to be protected by an automatic sprinkler system in accordance with Section 903.2.5.
  4. The NS value is only for use in evaluation of existing building area in accordance with the International Existing Building Code.
  5. New Group I-1 and I-3 occupancies are required to be protected by an automatic sprinkler system in accordance with Section 903.2.6. For new Group I-1 occupancies, Condition 1, see Exception 1 of Section 903.2.6.
  6. New and existing Group I-2 occupancies are required to be protected by an automatic sprinkler system in accordance with Section 903.2.6 and Section 1103.5 of the International Fire Code.
  7. New Group I-4 occupancies see Exceptions 2 and 3 of Section 903.2.6.
  8. New Group R occupancies are required to be protected by an automatic sprinkler system in accordance with Section 903.2.8.
  9. The maximum allowable area for a single-story nonsprinklered Group U greenhouse is permitted to be 9,000 square feet, or the allowable area shall be permitted to comply with Table C102.1 of Appendix C.
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