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Floor Area Ratio, Lot Coverage, Large Dwelling, Accessory Structure and ADU Calculations

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Summary

This handout explains how to calculate: floor area ratio (FAR), lot coverage and floor areas of structures for compliance with size limits.

Architectural Feature Gross Floor Area or just “Floor Area”

Use to calculate area of structures (except for ADUs / JADUs) for compliance with max size and other Zoning limitations.

See: 13.10.510(E);
Definition 13.10.700-F,
“Floor Area, Gross”		 Net Floor Area

Use to calculate:
1) Floor Area Ratio. Apply to ADUs only for FAR calculation purposes.
2) Large Dwellings

FAR calc is based on gross lot area, excluding coastal bluffs and beaches. See: 13.10.510(E);13.10.700-F, “Floor Area, Net,” “Floor Area Ratio,” 13.10.324(C)		 ADUs

See definition:
“Floor Area, Habitable”		 Lot Coverage

Based on gross lot area, excluding coastal bluffs and beaches

See: 13.10.510(E);
Definition 13.10.700-L, “Lot Coverage”
Building area – covered and enclosed (roof and four walls). Include all covered and enclosed habitable and non-habitable floor areas with ceiling at least 7’ high. Measure to exterior walls. For open-beam ceilings, measure to undersides of beams/rafter. Include all covered and enclosed habitable and non-habitable floor areas with ceiling at least 7’ high. Measure to exterior walls. For open-beam ceilings, measure to undersides of beams or rafters. Include the gross floor area used for living, sleeping, bathing, eating or cooking. Exclude garages, carports, attics, utility rms, other areas not used for habitation. Building footprint counts 1x


Inch    Feet
1 = .08
2 = .17
3 = .25
4 = .33
5 = .416
6 = .5
7 = .58
8 = .66
9 = .75
10 = .83
11 = .916
Attic (see definition, 13.10.700-A) Count only areas with at least 7’ of headroom. Measure to underside of open beam ceiling, excluding collar ties. Do not count. Do not count. (Attics cannot be habitable, by definition.)
Basement (see definition, 13.10.700-B) Count only areas with at least 7’ of headroom. Do not count. Count if habitable.
Do not count if nonhabitable.
Underfloor (See 13.10.700-U: the space between the underside of the floor framing and the grade below.) Do not count. Underfloor shall have no interior stairs, heating, insulation or finished floors, but may have windows, outlets, equipment and storage. Do not count. Do not count.
Mezzanine/ loft if less than 1/3 area of room below Count areas with headroom at least 7’. Do not count. Count areas with headroom at least 7’
High ceilings Floor area under ceiling >18' counts 2x; under ceiling >27' counts 3x. Measure to underside of open beam ceilings. Floor area under ceiling >18' counts 2x; under ceiling >24' counts 3x. Measure to undersides of open beams / rafters. Count once.
Enclosed or interior stairs and landings, elevator shafts Count on each story. Count on each story. Count on each story unless nonhabitable.
Exterior, unenclosed stairs and landings (may be covered) Do not count. Do not count. Do not count. Count once, even if deck not counted.
Deck or porch, covered and enclosed Count. Count, except up to 140 sq.ft. of covered and enclosed front porch. Do not count. Count, except up to 140 sf covered and enclosed front porch.
Deck or porch, covered but unenclosed Do not count. Do not count. Do not count. Count once. In Pleasure Point, up to 140 sf front porch exempt (enclosed or unencl.) unless remaining lot cov nonconforming.
Deck, unenclosed Do not count. Do not count. Do not count. Deck > 18" high counts.
Deck, unenclosed, cantilevered Do not count. Do not count. Do not count. Do not count, even stairs attached. Stairs to ground count.
Deck or porch, covered and unenclosed Do not count. Do not count. Do not count. Count once. In Pleasure Point: up to 140 sf front porch as per above.
Trellis or arbor, cover solid or open Do not count. Do not count. Do not count. Count unless cover cantilevered.
Garage, carport Count. Up to 225 sq.ft. exempt per single-family or multi-family dwelling unit (excluding ADUs and JADUs).
Nonresidential parking (mixed use) not counted.		 Do not count. Up to 225 sq.ft. credit per single-family or multi-family dwelling unit, (excluding ADU / JADU).
Nonresidential parking (mixed use) not counted.
Detached accessory structure or greenhouse Count unless less than 120 square feet and less than 10’ high. Count unless less than 120 square feet and less than 10’ high. Do not count. Count.
Bay windows (See 13.10.700-B.) Do not count. Do not count. Count if in habitable area. Do not count.
Eaves, chimney / chase Do not count. Do not count. Do not count. Do not count.
Awnings, fences and walls Do not count. Do not count. Do not count. Do not count.
Covered, enclosed atrium Count on each story. Count on each story. Don’t count unless habitable. Count once.
Uncovered atrium Do not count. Do not count. Do not count. Count.
Utility room or nonhabitable storage Count areas with ceiling at least 7’ high. Count areas with ceiling at least 7’ high. Don’t count unless habitable. Count.
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