GroundRules
N.Y.C. Admin. Code § BC 506: Section BC 506: Building Area Modifications
Where this section sits in the code
- New York City Administrative Code
- Title 28
- Chapter 7: New York City Building Code
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 Basement and cellar.
A single basement or cellar need not be included in the total allowable building area, provided such basement or cellar does not exceed the area permitted for a building with no more than one story above grade plane.
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 through 506.2.4, and Section 506.3.
Table 506.2
a
Allowable Area Factor (
A
t
= NS, S1, S13D, S13R, or SM, as applicable) in Square Feet
Occupancy Classification
See Footnotes
Type of Construction
Type I
Type II
Type III
Type IV
i
Type V
A
B
A
B
A
B
HT
A
B
A-1
NS
b, c
UL
UL
17,500
10,500
14,700
5,600
15,000
8,400
5,500
S1
UL
UL
52,500
31,500
44,100
16,800
45,000
25,200
16,500
SM
UL
UL
35,000
21,000
29,400
11,200
30,000
16,800
11,000
A-2
NS
b, c
UL
UL
17,500
9,500
14,000
5,600
15,000
8,400
5,500
S1
UL
UL
52,500
28,500
42,000
16,800
45,000
25,200
16,500
SM
UL
UL
35,000
19,000
28,000
11,200
30,000
16,800
11,000
A-3
NS
b, c
UL
UL
17,500
9,500
14,000
5,600
15,000
8,400
5,500
S1
UL
UL
52,500
28,500
42,000
16,800
45,000
25,200
16,500
SM
UL
UL
35,000
19,000
28,000
11,200
30,000
16,800
11,000
A-4
NS
b, c
UL
UL
17,500
9,500
14,000
5,600
15,000
8,400
5,500
S1
UL
UL
52,500
28,500
42,000
16,800
45000
25,200
16,500
SM
UL
UL
35,000
19,000
28,000
11,200
30,000
16,800
11,000
A-5
NS
b, c
UL
UL
UL
UL
UL
UL
UL
UL
UL
S1
SM
B
NS
b, c
UL
UL
37,500
10,500
28,500
5,600
36,000
8,400
5,500
S1
UL
UL
112,500
31,500
85,500
16,800
108,000
25,200
16,500
SM
UL
UL
75,000
21,000
57,000
11,200
72,000
16,800
11,000
E
NS
b, c
UL
UL
26,000
10,500
23,500
5,600
25,500
8,400
5,500
S1
UL
UL
78,000
31,500
70,500
16,800
76,500
25,200
16,500
SM
UL
UL
52,000
21,000
47,000
11,200
51,000
16,800
11,000
F-1
NS
b, c
UL
UL
12,500
7,500
7,500
3,000
10,000
3,000
1,000
S1
UL
UL
37,500
22,500
22,500
9,000
30,000
9,000
3,000
SM
UL
UL
25,000
15,000
15,000
6,000
20,000
6,000
2,000
F-2
NS
b, c
UL
UL
37,500
10,500
28,500
5,600
30,000
8,400
5,500
S1
UL
UL
112,500
31,500
85,500
16,800
90,000
25,200
16,500
SM
UL
UL
75,000
21,000
57,000
11,200
60,000
16,800
11,000
H-1
NS
b, c
21,000
16,500
11,000
7,500
9,500
7,000
10,500
7,500
NP
S1
H-2
f
NS
b, c
21,000
16,500
11,000
7,500
9,500
7,000
10,500
7,500
3,000
S1
SM
H-3
f
NS
b, c
UL
60,000
26,500
14,000
17,500
13,000
25,000
10,000
5,000
S1
SM
H-4
NS
b, c
UL
UL
37,500
17,500
28,500
17,500
36,000
18,000
6,500
S1
UL
UL
112,500
52,500
85,500
52,500
108,000
54,000
19,500
SM
UL
UL
75,000
35,000
57,000
35,000
72,000
36,000
13,000
H-5
NS
b, c
UL
UL
37,500
23,000
28,500
19,000
36,000
18,000
9,000
S1
UL
UL
112,500
69,000
85,500
57,000
108,000
54,000
27,000
SM
UL
UL
75,000
46,000
57,000
38,000
72,000
36,000
18,000
I-1
NS
b, c
UL
UL
19,000
NP
16,500
5,600
18,000
NP
NP
S13D
UL
UL
19,000
NP
16,500
5,600
18,000
NP
NP
S1
UL
UL
57,000
49,500
16,800
54,000
NP
NP
SM
UL
UL
38,000
NP
33,000
11,200
36,000
NP
NP
I-2
NS
b, c
UL
UL
7,000
3,500
5,000
1,200
6,500
2,000
NP
S1
UL
UL
21,000
10,500
15,000
3,600
19,500
6,000
NP
SM
UL
UL
14,000
7,000
10,000
2,400
13,000
4,000
NP
I-3
NS
b, c
UL
UL
7,000
3,500
5,000
1,200
6,500
2,000
NP
S1
UL
UL
21,000
10,500
15,000
3,600
19,500
6,000
NP
SM
UL
UL
14,000
7,000
10,000
2,400
13,000
4,000
NP
I-4
NS
b, c
UL
UL
26,500
9,500
23,500
5,600
25,500
8,400
5,500
S1
UL
UL
79,500
28,500
70,500
16,800
76,500
25,200
16,500
SM
UL
UL
53,000
19,000
47,000
11,200
51,000
16,800
11,000
M
NS
b, c
UL
UL
21,500
7,500
18,500
5,600
14,000
8,400
5,500
S1
UL
UL
64,500
22,500
55,500
16,800
42,000
25,200
16,500
SM
UL
UL
43,000
15,000
37,000
11,200
28,000
16,800
11,000
R-1
NS
b, c
UL
UL
UL
NP
24,000
NP
20,500
NP
NP
S13R
S1
UL
UL
UL
NP
72,000
NP
61,500
NP
NP
SM
UL
UL
UL
NP
48,000
NP
41,000
NP
NP
R-2
NS
b, c
UL
UL
UL
NP
24,000
5,600
20,500
NP
NP
S13R
S1
UL
UL
UL
NP
72,000
16,800
61,500
NP
NP
SM
UL
UL
UL
NP
48,000
11,200
41,000
NP
NP
R-3
NS
b, c
UL
UL
17,500
10,500
14,700
5,600
30,000
8,400
g, h
5,500
g
S13D
5,600
S13R
S1
UL
UL
52,500
31,500
44,100
16,800
90,000
8,400
g, h
5,500
g
SM
UL
UL
35,000
21,000
29,400
11,200
60,000
S-1
NS
b, c
UL
48,000
12,000
7,500
7,500
7,500
7,500
5,000
1,000
S1
UL
144,000
36,000
22,500
22,500
22,500
22,500
15,000
3,000
SM
UL
96,000
24,000
15,000
15,000
15,000
15,000
10,000
2,000
S-2
d, e
NS
b, c
UL
UL
15,000
10,000
10,000
8,500
10,000
8,400
5,500
S1
UL
UL
45,000
30,000
30,000
25,500
30,000
25,200
16,500
SM
UL
UL
30,000
20,000
20,000
17,000
20,000
16,800
11,000
U
e
NS
b, c
UL
35,000
19,000
8,500
14,000
8,500
18,000
9,000
5,500
S1
UL
105,000
57,000
25,500
42,000
25,500
54,000
27,000
16,500
SM
UL
70,000
38,000
17,000
28,000
17,000
36,000
18,000
11,000
= Not permitted in Fire District
= Not permitted in Fire District without sprinklers
Note: UL = Unlimited; NP = Not permitted.
For SI: 1 square foot = 0.0929 m
2
.
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 the following sections for general exceptions to Table 506.2.
1. See Chapters 4 and 5 for specific exceptions to the allowable height in this chapter.
2. Section 506.3, Allowable area increase due to frontage.
3. Section 507, Unlimited area building.
b. See Section 903.2 for the minimum thresholds for protection by an automatic sprinkler system for specific occupancies.
c. The NS value is only for use in buildings not required by this code to be equipped throughout with an automatic sprinkler system.
d. For open parking structures, see Section 406.5.
e. For private garages, see Section 406.3.
f. See Section 415.8 for limitations.
g. See Exception 9 of Section D105.1 for allowances of Type VA and VB construction for R-3 occupancies.
h. See Exception 12 of Section D105.1 for allowances of Type VA construction for R-3 occupancies in Lower Density Growth Management Areas.
i. Type IV construction utilizing cross-laminated timber or structural composite lumber shall be sprinklered where required by Section 903.2.13.
506.2.1 Single-occupancy, one-story buildings.
The allowable area of a single-occupancy building with no more than one story above grade plane shall be determined in accordance with Equation 5-1:
A
a
= A
t
+ (NS × I
f
)
(Equation 5-1)
where:
A
a
= Allowable area (square feet).
A
t
= Tabular allowable area factor (NS, S1, S13D or S13R value, as applicable) in accordance with Table 506.2.
NS
= Tabular allowable area factor in accordance with Table 506.2 for nonsprinklered building (regardless of whether the building is sprinklered).
I
f
= Area increase factor due to frontage (percent) as calculated in accordance with Section 506.3.
506.2.2 Mixed-occupancy, one-story buildings.
The allowable area of a mixed-occupancy building with no more than one story above grade plane shall be determined in accordance with the applicable provisions of Section 508.1 based on Equation 5-1 for each applicable occupancy.
506.2.2.1 Group H-2 or H-3 mixed occupancies.
For a building containing Group H-2 or H-3 occupancies, the allowable area shall be determined in accordance with Section 508.4.2, with the sprinkler system increase applicable only to the portions of the building not classified as Group H-2 or H-3.
506.2.3 Single-occupancy, multistory buildings.
The allowable area of a single-occupancy building with more than one story above grade plane shall be determined in accordance with Equation 5-2:
A
a
= [A
t
+ (NS × I
f
)] × S
a
(Equation 5-2)
where:
A
a
= Allowable area (square feet).
A
t
= Tabular allowable area factor (NS, S13D, S13R or SM value, as applicable) in accordance with Table 506.2.
NS
= Tabular allowable area factor in accordance with Table 506.2 for a nonsprinklered building (regardless of whether the building is sprinklered).
I
f
Area factor increase due to frontage (percent) as calculated in accordance with Section 506.3.
S
a
Actual number of building stories above grade plane, not to exceed three. For buildings equipped throughout with an automatic sprinkler system installed in accordance with Section 903.3.1.2, use the actual number of building stories above grade plane, not to exceed four.
No individual story shall exceed the allowable area (Aa) as determined by Equation 5-2 using the value of S
a
= 1.
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 total building area shall be such that the aggregate sum of the ratios of the actual 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.
A
a
= [A
t
+ (NS × I
f
)]
(Equation 5-3)
where:
A
a
= Allowable area (square feet).
A
t
= Tabular allowable area factor (NS, S13D, S13R or SM value, as applicable) in accordance with Table 506.2.
NS
= Tabular allowable area factor in accordance with Table 506.2 for a nonsprinklered building (regardless of whether the building is sprinklered).
I
f
= Area factor increase due to frontage (percent) as calculated in accordance with Section 506.3.
Exception: For buildings designed as separated occupancies under Section 508.4 and equipped throughout with an automatic sprinkler system installed in accordance with Section 903.3.1.2, the total building area shall be such that the aggregate sum of the ratios of the actual 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 four.
506.2.4.1 Group H-2 or H-3 mixed occupancies.
For a building containing Group H-2 or H-3 occupancies, the allowable area shall be determined in accordance with Section 508.4.2, with the sprinkler system increase applicable only to the portions of the building not classified as Group H-2 or H-3.
506.3 Frontage increase.
Area factor increase shall be determined in accordance with Sections 506.3.1 through 506.3.3.
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 on a public way or open space. Such open space shall be either on the same zoning lot or dedicated for public use and shall be accessed from a street or approved fire lane.
506.3.2 Minimum frontage distance.
To qualify for an area factor increase based on frontage, the public way or open space 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 interior tax lot line.
2. The entire width of a street, alley or public way.
3. The exterior face of an adjacent building on the same tax lot.
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 building area increase based on frontage, regardless of the actual width of the public way or open space. 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.
W = (L
1
× w
1
+ L
2
× w
2
+ L
3
× w
3
…)/F
(Equation 5-4)
where:
W
= (Width: weighted average) = Calculated width of public way or open space (feet).
L
n
= Length of a portion of the exterior perimeter wall.
w
n
= Width (³ 20 feet) of a public way or open space associated with that portion of the exterior perimeter wall.
F
= Building perimeter that fronts on a public way or open space having a width of 20 feet (6096 mm) or more.
Exception: Where a building meets the requirements of Section 507, as applicable, except for compliance with the minimum 60-foot (18 288 mm) public way or yard requirement, and the value of W is greater than 30 feet (9144 mm), the value of W shall not exceed 60 feet (18 288 mm).
506.3.3 Amount of increase.
The area factor increase based on frontage shall be determined in accordance with Equation 5-5:
I
f
= (F/P - 0.25) W/30
(Equation 5-5)
where:
I
f
= Area increase factor due to frontage.
F
= Building perimeter that fronts on a public way or open space having minimum distance of 20 feet (6096 mm).
P
= Perimeter of entire building (feet).
W
= Width of public way or open space (feet) in accordance with Section 506.3.2.
Collected 2026-09-06T02:48:57Z. Source file · JSON