What is Floor Area Ratio (FAR)?

Understanding Floor Area Ratio (FAR)

FAR is a zoning regulation that limits the total floor space of buildings on a property relative to its lot size. It is expressed as a ratio, providing a straightforward way to control the overall building mass within a given area.

Calculation

FAR is calculated by dividing the total floor area of all buildings on a lot by the lot's total area. This includes all building levels, basements, mezzanine levels, and attic spaces. The lot area encompasses all land within property lines, including setbacks and easements.

Ratio Interpretation

A FAR of 1.0 means the total floor area of buildings on the lot can equal the lot's area. A FAR of 2.0 means the total floor area can be twice the lot's area. Lower FAR values indicate lower density, while higher values indicate higher density.

Local Government Control

Local governments use FAR to regulate development density within their jurisdictions. FAR values vary significantly depending on zoning districts, reflecting the desired density for different areas.

FAR's Impact on ADU Development in California

FAR regulations can significantly influence the size and feasibility of ADUs, particularly in areas with strict zoning codes.

Size Limitations

FAR regulations can limit the maximum size of ADUs, especially in smaller lots. Although state law allows for a certain ADU size, FAR restrictions may impose stricter limitations.

Lot Size Considerations

Under FAR regulations, larger lots generally allow larger ADUs. Smaller lots may face significant FAR restrictions, limiting the size of the ADU.

Existing Structures

A property's existing structures can impact the allowable ADU size under FAR regulations. The total floor area of all buildings, including the primary dwelling unit, must be considered.

Local Variations

FAR regulations vary significantly between cities and counties in California. Homeowners must consult local zoning ordinances to determine the specific FAR requirements for their property.

ADU Type

Depending on the local jurisdiction, the type of ADU built (detached, attached, conversion) might affect how the FAR is calculated.

California's ADU Legislation and FAR

While California's ADU legislation aims to streamline ADU development, it does not entirely override local FAR regulations.

Statewide Mandates

State laws have established minimum standards for ADU development but do not eliminate local control over FAR. Local governments can still impose FAR restrictions that do not directly conflict with state mandates.

Balancing Density and Local Control

The state aims to balance the need for increased housing density with local control over land use. This results in a complex interplay between state and local regulations.

Navigating FAR Regulations for ADU Projects

• Consult Local Zoning Ordinances: Homeowners must thoroughly research local zoning ordinances to understand FAR requirements. Contact the local planning department for detailed information.
• Professional Guidance: Architects, engineers, and permit expeditors can assist in navigating FAR regulations. They can help determine the allowable ADU size and design a project that is compliant with local ordinances.
• Feasibility Studies: Conduct a feasibility study to assess the impact of FAR regulations on the ADU project. This study can help determine the maximum allowable ADU size and identify potential challenges.
• Variance Applications: If the ADU project does not comply with FAR regulations, homeowners may need to apply for variances. Variances are exceptions to zoning rules granted under specific circumstances.
• Design Considerations: Design the ADU to maximize floor space within FAR limitations. Consider vertical design elements, such as multi-level ADUs, to increase floor area within lot size constraints.