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Earlier editions: 20222019

Chapter 5 — GENERAL BUILDING HEIGHTS AND AREAS

506 Building Area — 2025 California Building Code

California Building Code (Title 24, Part 2) · 2025 edition · updated 2026-09-25 · California

CBSC: official editions, supplements and errata

Italicized text is a California amendment to the model code, as printed in the official publication.

Can I exclude my basement from allowable floor area?

Not included if the total basement area is no more than the area permitted for a one-story above-grade building; otherwise count it.

Cite as: 2025 California Building Code (Title 24, Part 2) § 506 · Effective January 1, 2026 · Official source: Building Standards Commission

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.

Exceptions & meaning →

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 (A = NS, S1, S13R, S13D or SM, as applicable) IN SQUARE FEETa, b, j
t

OCCUPANCY
CLASSIFICATION		 SEE FOOTNOTES TYPE OF CONSTRUCTION TYPE OF CONSTRUCTION TYPE OF CONSTRUCTION TYPE OF CONSTRUCTION TYPE OF CONSTRUCTION TYPE OF CONSTRUCTION TYPE OF CONSTRUCTION TYPE OF CONSTRUCTION TYPE OF CONSTRUCTION TYPE OF CONSTRUCTION TYPE OF CONSTRUCTION TYPE OF CONSTRUCTION
OCCUPANCY
CLASSIFICATION		 SEE FOOTNOTES Type I Type I Type II Type II Type III Type III Type IV Type IV Type IV Type IV Type V Type V
OCCUPANCY
CLASSIFICATION		 SEE FOOTNOTES 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
A-1 S1 UL UL 62,000 34,000 56,000 34,000 180,000 120,000 75,000 60,000 46,000 22,000
A-1 SM_ (without height increase)_ UL UL 46,500 25,500 42,000 25,500 135,000 90,000 56,250 45,000 34,500 16,500
A-1 SM (with height increase) UL UL 15,500 8,500 14,000 8,500 45,000 30,000 18,750 15,000 11,500 5,500
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
A-2 S1 UL UL 62,000 38,000 56,000 38,000 180,000 120,000 75,000 60,000 46,000 24,000
A-2 SM_ (without height increase)_ UL UL 46,500 28,500 42,000 28,500 135,000 90,000 56,250 45,000 34,500 18,000
A-2 SM (with height increase) UL UL 15,500 9,500 14,000 9,500 45,000 30,000 18,750 15,000 11,500 6,000
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
A-3 S1 UL UL 62,000 38,000 56,000 38,000 180,000 120,000 75,000 60,000 46,000 24,000
A-3 SM_ (without height increase)_ UL UL 46,500 28,500 42,000 28,500 135,000 90,000 56,250 45,000 34,500 18,000
A-3 SM (with height increase) UL UL 15,500 9,500 14,000 9,500 45,000 30,000 18,750 15,000 11,500 6,000
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
A-4 S1 UL UL 62,000 38,000 56,000 38,000 180,000 120,000 75,000 60,000 46,000 24,000
A-4 SM_ (without height increase)_ UL UL 46,500 28,500 42,000 28,500 135,000 90,000 56,250 45,000 34,500 18,000
A-4 SM (with height increase) UL UL 15,500 9,500 14,000 9,500 45,000 30,000 18,750 15,000 11,500 6,000
A-5 NS UL UL UL UL UL UL UL UL UL UL UL UL
A-5 S1 S1 S1 S1 S1 S1 S1 S1 S1 S1 S1 S1 S1
A-5 SM SM SM SM SM SM SM SM SM SM SM SM 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
B S1 UL UL 150,000 92,000 114,000 76,000 432,000 288,000 180,000 144,000 72,000 36,000
B 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
E S1 UL UL 106,000 58,000 94,000 58,000 306,000 204,000 127,500 102,000 74,000 38,000
E SM_ (without height increase)_ UL UL 79,500 43,500 70,500 43,500 229,500 153,000 95,625 76,500 55,500 28,500
E SM (with height increase) UL UL 26,500 14,500 23,500 14,500 76,500 51,000 31,875 25,500 18,500 9.500
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
F-1 S1 UL UL 100,000 62,000 76,000 48,000 402,000 268,000 167,500 134,000 56,000 34,000
F-1 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
F-2 S1 UL UL 150,000 92,000 114,000 72,000 606,000 404,000 252,500 202,000 84,000 52,000
F-2 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
H-1 S1 S1 S1 S1 S1 S1 S1 S1 S1 S1 S1 S1 S1

GENERAL BUILDING HEIGHTS AND AREAS

TABLE T5A0B6.L2E— 5A0L6L.2O—WAALBLLOEW AARBELAE F AARCETAO FRA (CAT =O NRS (A, S =1,N SS1,3 SR1,, SS1133DR,o Sr 1S3MD, oars SaMpp, laics aabplpel)i cINa bSlQe)U IANR SEQ FUEAERTEa, bF, E j—ETcoa, nb,t jinued
t t

OCCUPANCY
CLASSIFICATION		 SEE FOOTNOTES TYPE OF CONSTRUCTION TYPE OF CONSTRUCTION TYPE OF CONSTRUCTION TYPE OF CONSTRUCTION TYPE OF CONSTRUCTION TYPE OF CONSTRUCTION TYPE OF CONSTRUCTION TYPE OF CONSTRUCTION TYPE OF CONSTRUCTION TYPE OF CONSTRUCTION TYPE OF CONSTRUCTION TYPE OF CONSTRUCTION
OCCUPANCY
CLASSIFICATION		 SEE FOOTNOTES Type I Type I Type II Type II Type III Type III Type IV Type IV Type IV Type IV Type V Type V
OCCUPANCY
CLASSIFICATION		 SEE FOOTNOTES A B A B A B A B C HT A B
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
H-2 S1 S1 S1 S1 S1 S1 S1 S1 S1 S1 S1 S1 S1
H-2 SM SM SM SM SM SM SM SM SM SM SM SM 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
H-3 S1 S1 S1 S1 S1 S1 S1 S1 S1 S1 S1 S1 S1
H-3 SM SM SM SM SM SM SM SM SM SM SM SM 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
H-4 S1 UL UL 150,000 70,000 114,000 70,000 288,000 216,000 162,000 144,000 72,000 26,000
H-4 SM_ (without height increase)_ UL UL 112,500 52,500 85,500 52,500 216,000 162,000 121,500 108,000 54,000 19,500
H-4 SM (with height increase) UL UL 37,500 17,500 28,500 17,500 72,000 54,000 40,500 36,000 18,000 6,500
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
H-5 S1 UL UL 150,000 92,000 114,000 76,000 288,000 216,000 162,000 144,000 72,000 36,000
H-5 SM_ (without height increase)_ UL UL 112,500 69,000 85,500 57,000 216,000 162,000 121,500 108000 54,000 27,000
H-5 SM (with height increase) UL UL 37,500 23,000 28,500 19,000 72,000 54,000 40,500 36,000 18,000 9,000
I-2 NSd, f UL UL 15,000 11,000 12,000 NP NP NP NP 12,000 9,500 NP
I-2 S1 UL UL 60,000 44,000 48,000 NP NP NP NP 48,000 38,000 NP
I-2 SM_ (without height increase)_ UL UL 45,000 33,000 36,000 NP NP NP NP 36,000 28,500 NP
I-2 SM (with height increase) UL UL 15,000 11,000 12,000 NP NP NP NP 12,000 9,500 NP
I-3 NSd, e UL 15,100 NP NP NP NP NP NP NP NP NP NP
I-3 S1 UL 45,300 NP NP NP NP NP NP NP NP NP NP
I-3 SM_ (without height increase)_ UL 30,200 NP NP NP NP NP NP NP NP NP NP
I-3 SM (with height increase) UL 15,100 NP NP NP NP NP NP NP NP NP NP
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
I-4 S1 UL 121,000 106,000 52,000 94,000 52,000 306,000 204,000 102,000 102,000 74,000 36,000
I-4 SM_ (without height increase)_ UL 181,500 79,500 39,000 70,500 39,000 229,500 153,000 76,500 76,500 55,500 27,000
I-4 SM (with height increase) UL 60,500 26,500 13,000 23,500 13,000 76,500 51,000 25,500 25,500 18,500 9,000
L NS UL 60,000 37,500 17,500 28,500 17,500 60,000 37,500 36,000 36,000 18,000 6,500
L S1 S1 S1 S1 S1 S1 S1 S1 S1 S1 S1 S1 S1
L SM SM SM SM SM SM SM SM SM SM SM SM SM
M NS UL UL 21,500 12,500 18,500 12,500 61,500 41,000 26,625 20,500 14,000 9,000
M S1 UL UL 86,000 50,000 74,000 50,000 246,000 164,000 102,500 82,000 56,000 36,000
M 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
R-1h S13R S13R S13R S13R S13R S13R S13R S13R S13R S13R S13R S13R S13R
R-1h S1 UL UL 96,000 64,000 96,000 64,000 246,000 164,000 102,500 82,000 48,000 28,000
R-1h SM_ (without height increase)_ UL UL 72,000 48,000 72,000 48,000 184,500 123,000 76,875 61,500 36,000 21,000
R-1h SM (with height increase) UL UL 24,000 16,000 24,000 16,000 61,500 41,000 25,625 20,500 12,000 7,000
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
R-2h S13R S13R S13R S13R S13R S13R S13R S13R S13R S13R S13R S13R S13R
R-2h S1 UL UL 96,000 64,000 96,000 64,000 246,000 164,000 102,500 82,000 48,000 28,000
R-2h SM_ (without height increase)_ UL UL 72,000 48,000 72,000 48,000 184,500 123,000 76,875 61,500 36,000 21,000
R-2h SM (with height increase) UL UL 24,000 16,000 24,000 16,000 61,500 41,000 25,625 20,500 12,000 7,000
R-2 Type VA
constructionk		 NSd NP NP NP NP NP NP NP NP NP NP 12,000 NP
R-2 Type VA
constructionk		 S13R NP NP NP NP NP NP NP NP NP NP 12,000 NP
R-2 Type VA
constructionk		 S1 NP NP NP NP NP NP NP NP NP NP 48,000 NP
R-2 Type VA
constructionk		 SM_ (without height increase)_ NP NP NP NP NP NP NP NP NP NP 36,000 NP
R-2 Type VA
constructionk		 SM (with height increase) NP NP NP NP NP NP NP NP NP NP 36,000 j NP

5-10 2025 CALIFORNIA BUILDING CODE

GENERAL BUILDING HEIGHTS AND AREAS

TABLET 5A0B6L.2E— 5A0L6L.2O—WAALBLLOEW AARBELAE F AARCETAO FRA (CAT =O RN S(A, S =1 N, SS1, 3SR1, S13DR,o Sr1 S3MD, oars SaMpp, alisc aabplpel)i cINab SlQe)U IANR SEQ FUEAERTEa, bF, E j—ETcao, nb, tjinued
t t

OCCUPANCY
CLASSIFICATION		 SEE FOOTNOTES TYPE OF CONSTRUCTION TYPE OF CONSTRUCTION TYPE OF CONSTRUCTION TYPE OF CONSTRUCTION TYPE OF CONSTRUCTION TYPE OF CONSTRUCTION TYPE OF CONSTRUCTION TYPE OF CONSTRUCTION TYPE OF CONSTRUCTION TYPE OF CONSTRUCTION TYPE OF CONSTRUCTION TYPE OF CONSTRUCTION
OCCUPANCY
CLASSIFICATION		 SEE FOOTNOTES Type I Type I Type II Type II Type III Type III Type IV Type IV Type IV Type IV Type V Type V
OCCUPANCY
CLASSIFICATION		 SEE FOOTNOTES A B A B A B A B C HT A B
R-2.1h NSd UL 55,000 19,000 NP 16,500 NP 54,000 NP NP NP 10,500 NP
R-2.1h S13R UL 55,000 19,000 NP 16,500 NP NP NP NP NP 10,500 NP
R-2.1h S1 UL 220,000 76,000 NP 66,000 NP 216,000 NP NP NP 42,000 NP
R-2.1h SM_ (without height increase)_ UL 165,000 57,000 NP 49,500 NP 162,000 NP NP NP 31,500 NP
R-2.1h SM (with height increase) UL 55,000 19,000 NP 16,500 NP 41,000 25,625 20,500 41,000 10,500 NP
R-2.2h NSl UL UL 24,000 NP 24,000 NP 61,500 41,000 25,625 20,500 12,000 NP
R-2.2h S1 UL UL 96,000 NP 96,000 NP 246,000 _ 164,000_ 102,500 82,000 48,000 NP
R-2.2h SM_ (without height increase)_ UL UL 72,000 NP 72,000 NP 184,500 _ 123,000_ 76,875 61,500 36,000 NP
R-2.2h SM (with height increase) UL UL 24,000 NP 24,000 NP 61,500 41,000 25,625 20,500 12,000 NP
R-3_, R-3-1_h NSd UL UL UL UL UL UL UL UL UL UL UL UL
R-3_, R-3-1_h S13D S13D S13D S13D S13D S13D S13D S13D S13D S13D S13D S13D S13D
R-3_, R-3-1_h S13R S13R S13R S13R S13R S13R S13R S13R S13R S13R S13R S13R S13R
R-3_, R-3-1_h S1 S1 S1 S1 S1 S1 S1 S1 S1 S1 S1 S1 S1
R-3_, R-3-1_h SM SM SM SM SM SM SM SM SM SM SM SM 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
R-4h S13D S13D S13D S13D S13D S13D S13D S13D S13D S13D S13D S13D S13D
R-4h S13R S13R S13R S13R S13R S13R S13R S13R S13R S13R S13R S13R S13R
R-4h S1 UL UL 96,000 64,000 96,000 64,000 246,000 164,000 102,500 82,000 48,000 28,000
R-4h SM_ (without height increase)_ UL UL 72,000 48,000 72,000 48,000 184,500 123,000 76,875 61,500 36,000 21,000
R-4h SM (with height increase) UL UL 24,000 16,000 24,000 16,000 61,500 41,000 25,625 20,500 12,000 7,000
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
S-1 S1 UL 192,000 104,000 70,000 104,000 70,000 306,000 204,000 127,500 102,000 56,000 36,000
S-1 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
S-2 S1 UL 316,000 156,000 104,000 156,000 104,000 462,000 308,000 192,500 154,000 84,000 54,000
S-2 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
U S1 UL 142,000 76,000 34,000 56,000 34,000 216,000 144,000 90,000 72,000 36,000 22,000
U 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.
a. See Chapters 4 and 5 for specific exceptions to the allowable area in this chapter.
b. See Section 903.2 for the minimum thresholds for protection by an automatic sprinkler system for specific occupancies.
c. New Group H_and all Group L_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 building area in accordance with the_California Existing Building Code_.
e. New Group I-3 occupancies are required to be protected by an automatic sprinkler system in accordance with 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 with Section 1103.5 of the_Cali-_
fornia Fire Code.
g. New Group I-4 occupancies see Exceptions 2 and 3 of Section 903.2.6.
h. New Group R occupancies are required to be protected by an automatic sprinkler system in accordance with Section 903.2.8.
i. 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.
j. 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, the S increases
for height and stories in Tables 504.3 and 504.4 are permitted in addition to the S area increase in accordance with Table 506.2.
k. For Group R-2 buildings of Type VA construction equipped throughout with an approved automatic sprinkler system in accordance with Section 903.3.1.1, S area increase is permit-
ted in addition to the height and story increase provided the height shall not exceed 60 feet and 4 stories.
l. The NS value is only for use in evaluation of single-occupancy, multistory buildings per the formula in Section 506.2.3.

Exceptions & meaning →

506.2.1 Single-occupancy buildings.

The allowable area of each story of a single-occupancy building shall be determined in accordance with Equation 5-1:

Equation 5-1 A a = A t + ( NS × I f )

where:

A a = Allowable area (square feet).

GENERAL BUILDING HEIGHTS AND AREAS

A t = Tabular allowable area factor (NS, S1, S13R or S13D 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 factor increase due to frontage (percent) as calculated in accordance with Section 506.3.

The allowable area per story of a single-occupancy building with a maximum of two stories above grade plane shall be determined by Equation 5-1. The total allowable area of a single-occupancy building more than two stories above grade plane shall be determined in accordance with Equation 5-2:

Equation 5-2 A a = [ A t + ( NS × I f )] × S a

where:

A a = Allowable area (square feet). A t = Tabular allowable area factor (NS, S13R, S13D 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 = 3 for 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, where the actual number of stories above grade plane exceeds three.

S a = 2 for 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, actual number of building stories above grade plane, not to exceed two.

The actual area of any individual floor shall not exceed the allowable area per Equation 5-1.

Exceptions & meaning →

506.2.2 Mixed-occupancy buildings.

The allowable area of each story of a mixed-occupancy building shall be determined in accordance with the applicable provisions of Section 508.3.2 for nonseparated occupancies and Section 508.4.2 for separated occupancies.

For buildings with more than two 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, provided the aggregate sum of the ratios for portions of mixed-occupancy, multistory buildings containing 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, including any other associated non-separated occupancies, shall not exceed two.

Equation 5-3 A a = [ A t + ( NS × I f )]

where:

A a = Allowable area (square feet). A t = Tabular allowable area factor (NS, S13R, S13D 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.

Exceptions & meaning →

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 automatic sprinkler system increase applicable only to the portions of the building not classified as Group H-2 or H-3.

Exceptions & meaning →

506.3 Frontage increase.

Every building shall adjoin or have access to a public way to receive an area factor increase based on frontage. 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 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 of 20 feet (6096 mm) measured at right angles from the building face to any of the following:

  1. The closest interior lot line.

  2. The entire width of a street, alley or public way.

  3. The exterior face of an adjacent building on the same property.

The frontage increase shall be based on the smallest public way or open space that is 20 feet (6096 mm) or greater, and the percentage of building perimeter having a minimum 20 feet (6096 mm) public way or open space.

506.3.3 Amount of increase. The area factor increase based on frontage shall be determined in accordance with Table 506.3.3.

5-12 2025 CALIFORNIA BUILDING CODE

GENERAL BUILDING HEIGHTS AND AREAS

TABLE 506.3.3—FRONTAGE INCREASE FACTORa

PERCENTAGE OF BUILDING PERIMETER OPEN SPACE (feet) OPEN SPACE (feet) OPEN SPACE (feet)
PERCENTAGE OF BUILDING PERIMETER 20 to less than 25 25 to less than 30 30 or greater
0 to less than 25 0 0 0
25 to less than 50 0.17 0.21 0.25
50 to less than 75 0.33 0.42 0.50
75 to 100 0.50 0.63 0.75
For SI: 1 foot = 304.8 mm.
a. Interpolation is permitted.

506.3.3.1 Section 507 buildings. 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, the area factor increase based on frontage shall be determined in accordance with Table 506.3.3.1. The frontage increase shall be based on the smallest public way or open space that is 30 feet (9144 mm) or greater, and the percentage of building perimeter having a minimum 30 feet (9144 mm) public way or open space.

TABLE 506.3.3.1—SECTION 507 BUILDINGSa

PERCENTAGE OF
BUILDING
PERIMETER		 OPEN SPACE (feet) OPEN SPACE (feet) OPEN SPACE (feet) OPEN SPACE (feet) OPEN SPACE (feet) OPEN SPACE (feet)
PERCENTAGE OF
BUILDING
PERIMETER		 30 to less than 35 35 to less than 40 40 to less than 45 45 to less than 50 50 to less than 55 55 or greater
0 to less than 25 0 0 0 0 0 0
25 to less than 50 0.29 0.33 0.38 0.42 0.46 0.50
50 to less than 75 0.58 0.67 0.75 0.83 0.92 1.00
75 to 100 0.88 1.00 1.13 1.25 1.38 1.50
For SI: 1 foot = 304.8 mm.
a. Interpolation is permitted.
Exceptions & meaning →

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▸Contents — California Building Code (Title 24, Part 2)
California Building Code (Title 24, Part 2)

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