14B-5-506  Building area.
The provisions of Section 506 of IBC are adopted by reference with the following modifications:
1.   Revise Section 506.1 and its subsections to read:
506.1 General.
The allowable building 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 a public way or yard.
506.1.1 [Reserved.]
506.1.2 [Reserved.]
506.1.3 Basements.
Basements shall be included in building area where the total area of such basements exceeds the allowable building area for a one-story above grade plane building of the same occupancy and construction type.
506.1.3.1 Maximum area.
Every basement exceeding 40,000 square feet (3716 m2) in area shall be subdivided by fire barriers into areas not exceeding 40,000 square feet (3716 m2), provided where the building is equipped throughout with an automatic sprinkler system, the maximum undivided area may be increased to 80,000 square feet (7432 m2).”
2.   Replace Table 506.2 as shown:
TABLE 506.2
ALLOWABLE AREA FACTOR (At = NS, S1, S13R, S13D or SM, as applicable) IN SQUARE FEETa, b
OCCUPANCY CLASSIFICATION
SEE NOTES
CONSTRUCTION TYPE
TYPE I
TYPE II
TYPE III
TYPE IV
TYPE V
A
B
A
B
A
B
HT
A
B
OCCUPANCY CLASSIFICATION
SEE NOTES
CONSTRUCTION TYPE
TYPE I
TYPE II
TYPE III
TYPE IV
TYPE V
A
B
A
B
A
B
HT
A
B
A-1
NS
UL
UL
16,000
8,500
6,000
NP
6,000
3,000
NP
S1
UL
UL
64,000
34,000
24,000
12,000
24,000
12,000
NP
SM
UL
UL
48,000
25,500
18,000
9,000
18,000
9,000
NP
A-2
NS
UL
UL
16,000
8,500
6,000
5,000
6,000
3,000
NP
S1
UL
UL
64,000
34,000
24,000
20,000
24,000
12,000
NP
SM
UL
UL
48,000
25,500
18,000
15,000
18,000
9,000
NP
A-3
NS
UL
UL
16,000
8,500
6,000
5,000
6,000
3,000
NP
S1
UL
UL
64,000
34,000
24,000
20,000
24,000
12,000
NP
SM
UL
UL
48,000
25,500
18,000
15,000
18,000
9,000
NP
A-4
NS
UL
UL
16,000
8,500
6,000
5,000
6,000
3,000
NP
S1
UL
UL
64,000
34,000
24,000
20,000
24,000
12,000
NP
SM
UL
UL
48,000
25,500
18,000
15,000
18,000
9,000
NP
A-5
NS
UL
UL
UL
UL
UL
UL
UL
UL
UL
S1
UL
SM
UL
B
NS
UL
UL
20,000
6,000
10,000
8,000
10,000
6,000
4,000
S1
UL
UL
UL
UL
UL
32,000
40,000
24,000
16,000
SM
UL
UL
60,000
18,000
30,000
24,000
30,000
18,000
NP
E-1
NS
UL
UL
16,000
5,000
8,000
3,000
10,000
3,000
NP
S1
UL
UL
64,000
20,000
32,000
12,000
40,000
12,000
NP
SM
UL
UL
48,000
15,000
24,000
9,000
30,000
9,000
NP
E-2
NS
UL
UL
16,000
5,000
8,000
3,000
10,000
3,000
NP
S1
UL
UL
64,000
20,000
32,000
12,000
40,000
12,000
NP
SM
UL
UL
48,000
15,000
24,000
9,000
30,000
9,000
NP
F-1
NS
UL
UL
16,000
4,000
8,000
4,000
8,000
5,000
3,000
S1
UL
UL
UL
UL
32,000
16,000
32,000
20,000
12,000
SM
UL
UL
48,000
12,000
24,000
12,000
24,000
15,000
NP
F-2
NS
UL
UL
20,000
10,000
10,000
6,000
10,000
6,000
4,000
S1
UL
UL
UL
UL
40,000
24,000
40,000
24,000
16,000
SM
UL
UL
60,000
30,000
30,000
18,000
30,000
18,000
NP
H-1
NS c, d
21,000
16,500
11,000
6,000
9,500
5,000
10,500
5,000
NP
S1
21,000
16,500
11,000
6,000
9,500
5,000
10,500
5,000
NP
SM
NP
NP
NP
NP
NP
NP
NP
NP
NP
H-2
NS c, d
21,000
16,500
11,000
6,000
9,500
5,000
10,500
NP
NP
S1
21,000
16,500
11,000
6,000
9,500
5,000
10,500
NP
NP
SM
42,000
16,500
11,000
NP
9,500
NP
NP
NP
NP
H-3
NS c, d
UL
60,000
20,000
6,000
10,000
5,000
10,000
NP
NP
S1
UL
60,000
20,000
6,000
10,000
5,000
10,000
NP
NP
SM
UL
60,000
20,000
NP
10,000
5,000
10,000
NP
NP
H-4
NS c, d
UL
UL
20,000
6,000
10,000
8,000
10,000
6,000
NP
S1
UL
UL
80,000
24,000
40,000
32,000
40,000
24,000
NP
SM
UL
UL
60,000
NP
30,000
24,000
30,000
NP
NP
H-5
NS c, d
UL
UL
16,000
4,000
8,000
4,000
8,000
NP
NP
S1
UL
UL
64,000
16,000
32,000
16,000
32,000
NP
NP
SM
UL
UL
48,000
NP
24,000
12,000
24,000
NP
NP
I-1
NS d, e
UL
55,000
16,000
4,000
6,000
4,000
6,000
3,000
NP
S1
UL
220,000
64,000
16,000
24,000
16,000
24,000
12,000
NP
SM
UL
165,000
48,000
12,000
18,000
12,000
18,000
9,000
NP
I-2
NS d, f
UL
UL
12,000
6,000
6,000
NP
6,000
3,000
NP
S1
UL
UL
48,000
24,000
24,000
NP
24,000
12,000
NP
SM
UL
UL
36,000
NP
NP
NP
NP
9,000
NP
I-3
NS d, e
UL
UL
12,000
6,000
6,000
NP
6,000
3,000
NP
S1
UL
UL
48,000
24,000
24,000
NP
24,000
12,000
NP
SM
UL
UL
36,000
NP
NP
NP
NP
9,000
NP
I-4
NS d, g
UL
55,000
16,000
4,000
6,000
4,000
6,000
3,000
NP
S1
UL
220,000
64,000
16,000
24,000
16,000
24,000
12,000
NP
SM
UL
165,000
48,000
12,000
18,000
12,000
18,000
9,000
NP
M
NS
UL
UL
16,000
6,000
8,000
6,000
8,000
5,000
3,000
S1
UL
UL
UL
UL
UL
24,000
32,000
20,000
12,000
SM
UL
UL
48,000
18,000
24,000
18,000
24,000
15,000
NP
R-1 h
NS d
UL
UL
24,000
10,000
10,000
8,000
10,000
5,000
3,000
S13R
UL
UL
48,000
20,000
20,000
16,000
20,000
10,000
6,000
S1
UL
UL
96,000
40,000
40,000
32,000
40,000
20,000
12,000
SM
UL
UL
72,000
30,000
30,000
24,000
30,000
15,000
9,000
R-2
NS
UL
UL
24,000
10,000
10,000
8,000
10,000
5,000
3,000
S13R
UL
UL
48,000
20,000
20,000
16,000
20,000
10,000
6,000
S1
UL
UL
96,000
40,000
40,000
32,000
40,000
20,000
12,000
SM
UL
UL
72,000
30,000
30,000
24,000
30,000
15,000
9,000
R-3 h
NS
UL
UL
24,000
10,000
10,000
8,000
10,000
5,000
3,000
S13D
UL
UL
48,000
20,000
20,000
16,000
20,000
10,000
6,000
S13R
UL
UL
48,000
20,000
20,000
16,000
20,000
10,000
6,000
S1
UL
UL
96,000
40,000
40,000
32,000
40,000
20,000
12,000
SM
UL
UL
72,000
30,000
30,000
24,000
30,000
15,000
9,000
R-4 h
NS d
UL
UL
24,000
10,000
10,000
8,000
10,000
5,000
3,000
S13D
UL
UL
48,000
20,000
20,000
16,000
20,000
10,000
6,000
S13R
UL
UL
48,000
20,000
20,000
16,000
20,000
10,000
6,000
S1
UL
UL
96,000
40,000
40,000
32,000
40,000
20,000
12,000
SM
UL
UL
72,000
30,000
30,000
24,000
30,000
15,000
9,000
R-5
NS
UL
UL
24,000
10,000
10,000
8,000
10,000
5,000
3,000
S13D
UL
UL
48,000
20,000
20,000
16,000
20,000
10,000
6,000
S13R
UL
UL
48,000
20,000
20,000
16,000
20,000
10,000
6,000
S1
UL
UL
96,000
40,000
40,000
32,000
40,000
20,000
12,000
SM
UL
UL
72,000
30,000
30,000
24,000
30,000
15,000
9,000
S-1
NS
UL
35,500
19,000
8,500
14,000
8,000
18,000
5,000
3,000
S1
UL
UL
UL
UL
56,000
32,000
72,000
20,000
12,000
SM
UL
106,500
57,000
25,500
42,000
24,000
54,000
15,000
NP
S-2
NS
UL
79,000
28,500
13,000
21,000
10,000
27,000
6,000
4,000 i
S1
UL
UL
UL
UL
84,000
40,000
108,000
24,000
16,000 i
SM
UL
237,000
85,500
39,000
63,000
30,000
81,000
18,000
NP
U
NS
UL
30,000
16,000
6,000
8,000
6,000
8,000
5,000
1,000
S1
UL
120,000
64,000
24,000
32,000
24,000
32,000
20,000
4,000
SM
UL
90,000
48,000
18,000
24,000
18,000
24,000
15,000
NP
 
For SI: 1 square foot = 0.0929 m 2.
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.
a.   See Chapters 4 and 5 for specific exceptions to the allowable area factor in this table.
b.   See Section 903.2 for the minimum thresholds for protection by an automatic sprinkler system for specific occupancies.
c.   New Group H occupancies are required to be protected by an automatic sprinkler system in accordance with Section 903.2.5.
d.   The NS value is only for use in evaluation of existing buildings in accordance with the Chicago Building Rehabilitation Code.
e.   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.
f.   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 Chicago Fire Prevention Code.
g.   New Group I-4 occupancies see Exceptions 2 and 3 of Section 903.2.6.
h.   New Group R-1, R-3 and R-4 occupancies are required to be protected by an automatic sprinkler system in accordance with Section 903.2.8.
i.   Type VB construction is not allowed for motor-vehicle-related occupancies other than private garages.
3.   Revise Equation 5-2 by deleting the second sentence from the description of Sa.
4.   Revise Section 506.2.4 to read:
506.2.4 Mixed-occupancy, multistory buildings.
Each story of a mixed-occupancy building with more than one story above grade plane shall individually comply with the applicable requirements of Section 508.1. For buildings with more than three stories above grade plane, the building area shall be such that the aggregate sum of the ratios of the actual floor area of each story divided by the allowable area of such stories, determined in accordance with Equation 5-3 based on the applicable provisions of Section 508.1, shall not exceed three.”
5.   Delete the exception to Section 506.2.4.
6.   Revise Section 506.3 to replace “public way” with “public way.”
7.   Revise Section 506.3.1 to read:
506.3.1 Minimum percentage of perimeter.
To qualify for an area factor increase based on frontage, a building shall have not less than 25 percent of its perimeter abut a public way, court or yard. Such court or yard shall be either on the same lot or dedicated for public use and shall have direct access, not less than 20 feet (6096 mm) wide, from a public way."
8.   Revise Section 506.3.2 to read:
506.3.2 Minimum frontage distance.
To qualify for an area factor increase based on frontage, the public way, court or yard adjacent to the building perimeter shall have a minimum distance (W) of 20 feet (6096 mm) measured at right angles from the building face to any of the following:
1.   The closest abutting property line.
2.   The far side of a public way.
3.   The exterior face of an adjacent building on the same lot.
4.   The opposite side of a court.
Where the value of W is greater than 30 feet (9144 mm), a value of 30 feet (9144 mm) shall be used in calculating the area factor increase based on frontage, regardless of the actual width of the public way, court or yard. Where the value of W varies along the perimeter of the building, the calculation performed in accordance with Equation 5-5 shall be based on the weighted average calculated in accordance with Equation 5-4.”
9.   Revise the definitions of values for Equation 5-4 by replacing "public way or open space" with "public way, court or yard" and inserting "but not greater than 30 feet (9144 mm)" at the end of the definition of Wn .
10.   Delete the exception to Section 506.3.2.
11.   Revise Equation 5-5 to read:
If = (F/P)(W/30)(S)      (Equation 5-5)
where:
If   =   Area factor increase due to frontage.
F   =   Building perimeter that fronts on a public way or yard having a minimum width of 20 feet (6096 mm) (feet).
P   =   Perimeter of entire building (feet).
W   =   Width of public way or yard (feet) in accordance with Section 506.3.2.
S   =   Where building is equipped throughout with an automatic sprinkler system in accordance with Section 903.3.1.1, S = 2; where building is not equipped throughout with an automatic sprinkler system in accordance with Section 903.3.1.1 or 903.3.1.2, S = 1.
(Amend Coun. J. 7-24-19, p. 3646, § 30; Amend Coun. J. 10-7-20, p. 21791, Art. II, § 7; Amend Coun. J. 6-25-21, p. 32180, Art. II, § 6)