How big can I build? LA floor area limits for single-family lots

Los Angeles limits house size with a number called Residential Floor Area. The limits come from the Baseline Mansionization Ordinance, as updated in 2017, and apply to single-family lots under the City's original zoning code, which still covers most of the city. It is the first number we work out before we sketch a new home or an addition.

Floor area limits by zone

The limit is a percentage of the lot area, and it depends on the zone shown for your lot. These figures apply to lots outside a Hillside Area and the Coastal Zone.

RA, RE, and RS lots can earn one 20 percent bonus per property when the design follows one of the massing methods the code lists, such as keeping each upper story to 75 percent or less of the ground floor.

What counts toward floor area

Residential Floor Area is the area inside the exterior walls of every building on the lot, not just the house. A detached garage, studio, or pool house counts unless it falls under one of the exclusions below. Two rules surprise many owners:

• Any floor area with a ceiling higher than 14 feet counts twice. A double-height living room uses its footprint two times over.
• Attic space with a ceiling height over 7 feet counts.

Stairways and elevator shafts are counted once, no matter how tall they are.

What does not count

• Required covered parking: up to 200 square feet per required space, and up to 400 square feet per lot, but only when the parking sits in the rear half of the lot or at least 55 feet from the front lot line. Otherwise only 200 square feet is excluded.
• Small detached accessory buildings: each one of 200 square feet or less, up to 400 square feet in total per lot.
• Lattice-roof porches, patios, and breezeways. A solid roof over the same patio counts.
• Basements on lots outside a Hillside Area and the Coastal Zone, when the floor or roof above sits no more than 2 feet above the lower of finished or natural grade at any point.

Floor area is not the only limit

The floor area cap sets how much house you can build. Other rules set its shape. On an R1 lot, an encroachment plane starts 20 feet up at the required front and side yards and angles inward, so upper floors often step back from the edges. Outside Hillside Areas and the Coastal Zone, R1 height in Height District 1 is 33 feet with a roof slope of 25 percent or more, or 28 feet with a flatter roof. The yards still apply: a front yard of up to 20 feet, a 15 foot rear yard, and 5 foot side yards, with wider side yards for a new house taller than 18 feet.

Some neighborhoods are mapped into R1 variation zones, such as R1V2, which set their own floor area ratios, heights, and building envelopes.

Lots that follow different rules

Hillside lots. Lots in a mapped Hillside Area follow the Baseline Hillside Ordinance, where allowed floor area is figured slope band by slope band and drops as the ground gets steeper. We cover those rules on our hillside home builder page.

Coastal Zone lots. The percentages above do not apply; the code points these lots to a different floor area rule.

Specific plans and historic districts. A specific plan or HPOZ can add its own limits or review. In the Mulholland Scenic Parkway Specific Plan, for example, adding more than 900 square feet since 1992 sends the project to a Design Review Board.

The new zoning code. Lots in the Downtown and Boyle Heights community plan areas have moved to the City's new zoning code, Chapter 1A, which has its own standards.

Where an ADU fits

If your floor area is used up, you may still be able to add a unit. State law says floor area limits cannot be used to block an 800 square foot ADU with 4 foot side and rear setbacks, as long as it meets the other local standards. We explain how that guarantee works in State ADU vs. LA Ordinance ADU and ADU rules in Los Angeles. For a new home or major addition, see how we approach custom home design and construction.

Common questions