Accessory Dwelling Unit

An accessory dwelling unit (ADU), sometimes referred to as a granny flat, in-law unit, second unit, backyard cottage, backyard dwelling or basement apartment, is a secondary residential unit added to the same property as a primary home. ADUs come in many forms and sizes and always include a kitchen and a sleeping area. ADUs include efficiency units, as defined in Section 17958.1 of the Health and Safety Code, and manufactured homes, as defined in Section 18007 of the Health and Safety Code.

Assessor’s Parcel Number

An Assessor’s Parcel Number (APN) is the number the City assigns to your parcel or lot. Find your APN by using tools like ZIMAS (City of Los Angeles) or LA County’s GIS Tool. This number is also sometimes referred to as an Assessor’s ID Number (AID), Property Identification Number (PIN), Property Account Number, or Tax Account Number. 


An architect is a design professional who has undergone training in design and construction management and is licensed in California. An architect takes legal responsibility for their work and offers a range of services, such as initial concept design, coordinating with subcontractors and other consultants, and managing the construction process. 

Building Code 

Building code is a series of standards set by the State of California that are adopted by a city or county to ensure safe, accessible, and energy-efficient buildings.  

California ADU Law

In 2017, the state of California’s legislature declared that allowing accessory dwelling units in single-family and multifamily zones are an essential component in addressing California’s housing needs. Many cities are still in the process of releasing their own ADU Ordinances that conform to the State of California’s January 2017 update to the standard for Accessory Dwelling Units, (Section 65852.2). 

A package of five State bills, effective January 1, 2020, further expanded the ability for Californians to build ADUs. Among other changes, these laws eliminate minimum lot size and owner-occupancy requirements; allow homeowners to add two units per lot, where certain access and setback criteria are met. Together, these laws streamline the ADU regulatory and construction process and make ADU development easier for residents.


A designer is a term for someone who does general design work. Like architects, they have the skills to design ADUs and may charge lower rates than architects, but also have less expertise. 


Entitlement is approval from a regulatory body (such as your community's Planning Department) to develop on a piece of land. 

Floor Area Ratio (FAR)

Floor Area Ratio is a ratio comprised of the number of feet of built space divided by the number of feet on a lot. This ratio controls how many square feet are allowed on a lot by establishing maximum FAR or other formulas. For example, a 2,000 square foot house on a 5,000 square foot lot has an FAR of 0.40 (2,000 divided by 5,000).

General Contractor

A general contractor assesses construction projects by working with homeowners to map out a plan from concept to completion. They are experts in project management, understand what materials are needed, can evaluate the required skills and number of subcontractors needed, prepare total construction cost estimates, and help prepare the necessary permits required to finish the project. 


A lien is a claim on a residential property for the homeowner's unpaid bills. When a lien is placed on a home's title, it means that the owner cannot legally sell, refinance or otherwise transfer a clear title of ownership to the home.

Lot Coverage

Lot coverage is expressed as a percentage that indicates how much space buildings are allowed to take up on a lot. 

Ministerial Review

A ministerial review is administered by the city to ensure an application has met all the requirements. There is no need for discretion or public hearing. 


Setbacks are the minimum space required between a structure and the property line. 

Single-family Zone

Single-family zoning is by far the most common zone of any kind in Los Angeles. In single-family zones, you can only build one house on the lot, no matter how big the lot is.

Site Plan

A site plan is drawing of your lot, buildings, and other features. 


A professional examination/drawing of your property boundaries and/or slope. 

Through lot

A through lot is a lot that is accessible to the street from the front and back property lines.

Utility Easement

Utility easements are areas of a property that were defined for use by utility companies when the property was first put on a plot. They are designated for overhead electric, telephone and television lines and underground electric, water, sewer, telephone, and cable lines.

Zoning/Zoning Code

City rules that govern what can and cannot be built on a site. Lots are designated a zone (e.g. R-1) and each zone has its own regulations. Rules about where an ADU can be built on a lot, how tall it can be, or in what zone it can be developed are all examples of zoning code.