§113.0234 Calculating Gross Floor Area
Gross floor area is calculated in relationship to the structure and grade adjacent to the exterior walls of a building. The elements included in the gross floor area calculation differ according to the type of development proposed and are listed in Sections 113.0234(a)-(c). Gross floor area does not include the elements listed in Section 113.0234(d). The total gross floor area for a premises is regulated by the floor area ratio development standard.
(a) Elements Included in Gross Floor Area for Development in All Zones
(1) Gross floor area includes all existing and proposed floors within the horizontal area delineated by the exterior surface of the surrounding exterior walls of the building.
(2) Gross floor area for basements is calculated as follows:
(A) For lots that slope less than 5 percent along each edge of the building footprint, gross floor area includes the area of all portions of a basement where the vertical distance between existing grade or proposed grade, whichever is lower, and the finish-floor elevation above exceeds 3 feet, 6 inches as shown in Diagram 113-02I.
Diagram 113-02I
Basements with Less than 5 Percent Slope
Finish-floor
3' - 6"
Less than 5 % slope
Section View
Area Area not included included in GFA in GFA
Plan View
(B) For lots that slope 5 percent or more along any edge of the building footprint, gross floor area includes the area of all portions of a basement where the vertical distance between existing grade or proposed grade, whichever is lower, and the finish-floor elevation above exceeds 5 feet, as shown in Diagram 113-02J.
Diagram 113-02J
Basements with 5 Percent or More Slope
Finish-floor
5'
More than 5 % slope
Section View
Area Area not included included in GFA in GFA
Plan View
(3) Gross floor area for underground parking structures includes the following, except where the parking structure design meets the exemptions identified in Section 113.0234(d)(3):
(A) All portions of the structure where the vertical distance between the existing or proposed grade, whichever is lower, and the finished floor elevation above, exceeds 5 feet.
(B) The vertical measurement between adjacent grade and the finished floor above shall not include subterranean vehicular access openings (up to a maximum of 25 foot width). Instead, the vertical distance measurement shall be measured from the imaginary plane perpendicular to the driveway access that connects the adjacent grades to the finished floor above. Diagram 113-02K
Underground Parking Structures
Building Outline
Building
Access to Underground Parking 25’ wide Max. Grade 3’6” or 5’ max. (See Section 113.0234(a)(2))
Street Access to Imaginary Plane 25’ Underground Parking Max. 25’ Wide Max. Vehicular Access
Plan Section
(4) Gross floor area includes enclosed exterior stairwells and enclosed exterior elevator shafts.
(5) Gross floor area includes interior shafts such as elevator shafts, ventilation shafts, and other similar vertical shafts, interior stairwells, ramps, and mechanical equipment rooms. Gross floor area includes the area of the horizontal projection into the interior shaft of each floor in plan view that is served by the elevator, shaft, stairwell, or ramp, as shown in Diagram 113-02L.
Diagram 113-02L
Interior Stairwells and Vertical Shafts
Interior elev ator s haft Projec tion of floor inc luded in GFA
Ac tual floor Projec tions of Floors inc luded in GF A Ac tual floor
Ac tual floor
Interior Stairwell Interior Vertic al Shaft
(6) Gross floor area includes on- or above-grade parking structures, garages, and carports that are constructed and maintained with less than two elevations of the element that are 100 percent completely open, measured from the finish-floor to the bottom of the floor or roof elevation immediately above, except for the support columns with maximum dimensions of 18 inches by 18 inches in plan view, as shown in Diagram 113-02M, and except where the parking structure design meets the exemptions identified in Section 113.0234(d)(3).
Diagram 113-02M
Garages/Carports
[image omitted; see the official PDF]
(7) Gross floor area includes penthouses, except in the following instances:
(A) When height of the enclosure above the highest roofline of the building or structure upon which the enclosure is located is no more than 13 feet for an elevator shaft or 9 feet for a stairwell; and
(B) When total plan area of the enclosure or enclosures is not more than 10 percent of the area of the roof plan of the building.
(b) Additional Elements Included in Gross Floor Area in Residential Zones and for Residential Development in Other Zones. Section 113.0234(b) does not apply to commercial development.
(1) Gross floor area includes roofed porches, entrances, exterior balconies, and patios when they project from the primary structure and are constructed and maintained with at least two elevations of the element that are less than 40 percent permanently open, as shown in Diagram 113-02N.
Diagram 113-02N
Projecting Porches and Balconies
3 elevations at least 2 elevations at least 40% open 40% open (not included in GFA) (not included in GFA)
2 elevations 3 elevations 1 elevation open with building more than 40% open more than 40% open area on only 1 side (not included in GFA) (not included in GFA) (included in GFA)
(2) Gross floor area includes roofed porches, entrances, exterior balconies, and patios when the element is recessed or partially recessed in the structure and surrounded or partially surrounded on three sides by the enclosed building. Gross floor area does not include 100 square feet of the recessed portion of the element when the fourth elevation of the element is at least 40 percent permanently open. This is illustrated in Diagram 113-02O.
Diagram 113-02O
Recessed Porches and Balconies
[image omitted; see the official PDF]
(3) Gross floor area includes any projected floor area and other phantom floors within the building’s exterior walls where specified dimensions are met. Phantom floors are located within the space above or below actual floors within a building, and are measured separately above each actual floor or below the lowest actual floor for under floor area, described as follows:
(A) Phantom Floors. When the vertical distance between the finish-floor elevation and the finish-floor or flat roof immediately above does not exceed 15 feet, the area of one floor (the actual floor) is included in gross floor area, as shown in Diagram 113-02Q.
Diagram 113-02Q
One Floor Below Actual Floor and Flat Roof
Actual Floor Max 15 '
Max Actual Floor 15 '
Actual Floor When the vertical distance between the finish-floor elevation and the finish-floor or roof elevation immediately above exceeds 15 feet, gross floor area includes the area of the actual floor plus the area of a phantom floor at 15 feet of height increments, or portion thereof, of height above the 15-foot height, as shown in Diagram 113-02R.
Diagram 113-02R
Multiple Floors below Actual Floor and Flat Roof
3' Phantom floor 4'-6" Phantom floor
Actual floor 7'-6" Phantom floor 27' 15' Phantom floor 27' 18' Actual floor 15' 15' 9' Actual floor Actual floor Actual floor
3 floors for GFA 3 floors for GFA 3 floors for GFA
Gross floor area excludes those portions of actual floors and phantom floors where there is less than 5 feet of vertical distance between the actual or phantom floor and the ceiling immediately above.
Diagram 113-02S
Multiple Floors Below Sloped Roof
Not included 6' in GFA 5'- 0"
Phantom floor
Not included 7' in GFA 15' 5'- 0" 30'
Actual floor Phantom floor 22'
15' 9'
Actual floor Actual floor
2 floors for GFA 3 floors for GFA
(B) Attic Space. Gross floor area includes the attic space as shown in Diagram 113-02T, where there are at least 5 feet of vertical distance between the attic floor and the roof elevation immediately above. The location of any ceilings immediately below the roof does not affect the measurement of phantom floors above the highest finish-floor elevation.
Diagram 113-02T
Attic Space
[image omitted; see the official PDF]
(C) Underfloor Area. Gross floor area includes additional phantom floors within the enclosed space below the lowest finish-floor elevation. In this case, the area of a phantom floor is included in gross floor area at each 15-foot increment, or portion thereof, of height between the lowest finish-floor elevation and grade, measured vertically from the lowest finish-floor elevation, as shown in Diagram 113-02U. Gross floor area excludes any area where there is less than 5 feet of height between grade and the finish-floor or phantom floor elevation immediately above.
Diagram 113-02U
Underfloor Area
Actual Floor (finish-floor)
5' Phantom floo Phantom Floor 15’ Not Included in GFA
5' Less than 15’ Phantom Floor
(D) Interior Balconies, Mezzanines, and Lofts. Gross floor area includes the area within a building adjacent to all interior balconies, mezzanines, and lofts, pursuant to the regulations for phantom floors in Section 113.0234(b)(3)(A) as if such elements did not exist adjacent to the space, as shown in Diagram 113-02V. The location of an adjacent interior balcony, mezzanine, or loft does not affect the location of phantom floors above the finished-floor elevation of the adjacent space.
Diagram 113-02V
Mezzanines
Not included 7'-6” in GFA 5'- 0" Phantom floor Not included in GFA 7'-6" Actual floor 5'- 0" Phantom floor 30
Actual floor
15
Actual floor
(E) Atriums. Gross floor area includes the area of the horizontal projection into the atrium from each adjacent floor in plan view. If no adjacent floors exist, the regulations for phantom floors in Section 113.0234(b)(3)(A) apply to the space within the atrium. This is illustrated in Diagram 113-02W.
Diagram 113-02W
Atriums
5'
Phantom floor
20'
Atrium 15'
Actual floor
11' Atrium
20' Actual floor Actual floor Phantom floor
9'
Actual floor
(4) Roof Decks. Gross floor area includes roof decks when any portion of the deck’s parapet, guardrail, wall, or fence (open or solid) enclosing the area exceeds an average of 42 inches in height, or exceeds 54 inches in height at any point.
(5) If a premises is located within two or more base zones, the maximum gross floor area shall be calculated separately based on the lot area within each base zone. The gross floor area calculation for each portion of the lot area within a base zone shall then be added together to determine the maximum gross floor area on the premises. The distribution of gross floor area on the premises may occur without regard to zone boundaries.
(c) Additional Elements Included in Gross Floor Area in Commercial and Industrial Zones (for other than residential development)
(1) Gross floor area includes atriums, provided, however, that only proposed or existing actual floors are included.
(2) Gross floor area includes porches when completely enclosed on all sides.
(d) Elements Not Included in Gross Floor Area
(1) Interior Courts, as defined in Section 113.0103; and
(2) Interior modifications, including additions of actual floor areas that do not affect the outer limits of the existing structural envelope.
(3) Parking Structures
(A) This exclusion from gross floor area does not apply to:
(i) Garages or carports that serve single dwelling unit development; or
(ii) Garages or carports that serve multiple dwelling unit development where each multiple dwelling unit has access to its own separate garage or carport.
(B) In order to exclude a parking structure from the calculation of gross floor area, a combination of at least two of the following shall be incorporated into project design as follows:
(i) The parking structure includes at least one subterranean floor where the vertical distance between adjacent grade and the finished floor elevation above is 5 feet or less. Elevations that provide vehicular access to a subterranean parking level may still meet this provision where the vertical distance is 5 feet or less as measured in accordance with Section 113.0234(a)(3)(B);
(ii) The parking structure is part of a wrapped design to screen parked vehicles within the structure from the adjacent public right-of-way;
(iii) The parking structure is screened from the adjacent public right-of-way on at least two elevations; or
(iv) The parking structure is at least 40 percent open on at least two elevations.
(4) Bay windows that meet all of the following criteria:
(A) The bay window height is 5 feet or less.
(B) The interior space created by the bay window does not project outward more than 4 feet.
(C) At least a 3 foot clear space is provided between the bottom of the bay window projection and the grade below.
(D) The bay window projection does not require structural support.
(E) The total length of the bay window shall not exceed 15 linear feet.
(Amended 1-9-2001 by O-18910 N.S.; effective 8-8-2001.) (Amended 3-1-2006 by O-19467 N.S.; effective 8-10-2006.) (Amended 11-13-2008 by O-19801 N.S.; effective 12-13-2008.) (Amended 8-4-2011 by O-20081 N.S.; effective 10-6-2011.) (Amended 5-5-2015 by O-20481 N.S.; effective 6-4-2015.) (Amended 4-5-2016 by O-20634 N.S.; effective 5-5-2016.) (Amended 3-22-2018 by O-20917 N.S.; effective 4-21-2018.) (Amended 1-8-2020 by O-21164 N.S.; effective 2-9-2020.) (Amended 2-1-2021 by O-21288 N.S.; effective 3-3-2021.) (Amended 7-22-2024 by O-21836 N.S.; effective 10-5-2024.) (Amended 6-15-2026 by O-22109 N.S.; effective 7-15-2026.)
[Editors Note: Amendments as adopted by O-22109 N.S. will not apply within the Coastal Overlay Zone until the California Coastal Commission certifies it as a Local Coastal Program Amendment. Click the link to view the Strikeout Ordinance highlighting changes to prior language http://docs.sandiego.gov/municode_strikeout_ord/O-22109-SO.pdf ]