About once a week, someone will give me a call with questions about adding an ADU to their home. Writing a blog post has been long over due, so I thought TODAY was the perfect day to get started. I’m glad you’re here to read this.

What is an ADU?

An ADU is an Accessory Dwelling Unit. Most neighborhoods are zoned for single family homes. For example, an R-1 Zone means 1 home per property. An R-2 Zone means you can build up to 2 single family homes or a duplex, with a maximum of 2 dwellings on site. An R-3 zone allows a triplex or even a small apartment, depending on density & parking restrictions. An R-4 Zone has less restrictive density requirements, so an R-4 zone is where most large apartments are built.

If your home is located on an R-1 zone, this means ONLY 1 home maximum can be built on your property. There is the exception though. An approved ADU allows you to add a 2nd dwelling unit to your property which can be used for family or can be rented out for extra income.

Under the previous code, a “granny flat” was limited to a maximum of 640 Sq. Ft. Here in Los Angeles, you can build an ADU up to a maximum of 1,200 Sq. Ft. There are a few restrictions, like the ADU should be located behind the main home and should not exceed the size of the main home on site.

The ADU can be attached to the main dwelling, or it can be detached. The ADU can be built from the ground up, or it can be converted from an existing accessory structure on site, like a garage, recreation room or pool room.

If you add square footage to an existing structure like a garage, you can maintain the existing rear and side yards which were approved for the original permitted structure, but all new additions must conform to the new code.

If you have an existing garage which is 2′-6″ from the rear property line and 1′-0″ from the side property line, the new ADU can maintain the same rear and side yard, but any new additions would need to be a minimum of 5′-0″ from the rear property line and 5′-0″ from the side property line(s). Also, no openings, such as windows, are permitted on walls with less than 3′-0″ from the property line.

Can I build an ADU above an existing garage?

Yes, the ADU can be 1 or 2 stories, but is limited to 1,200 Sq. Ft. maximum. If the existing garage sits a minimum of 5′-0″ from the rear and 5′-0″ from the side property lines, then the new ADU can be built on top of the existing garage. Any new additions must also meet the required read and side yard requirements.

If the existing garage is 4′-0″ from the rear and 3-0″ from the side property line, then the 2nd story ADU would need to be offset from the property lines to meet the minimum requirements of 5′-0″ rear & 5′-0″ side yards.

Some neighborhoods might have a maximum lot coverage, so that will need to be taken into account. For the most part though, if you have an R-1 lot and are within half a mile of public transportation and can meet the 5′-0″ side and rear minimum distances, then it’s most probable that you can add an ADU to your property.

What are the benefits of an ADU?

If you have a growing family, you can build an ADU for your parents, children, siblings, in-laws, cousins, uncles, aunts, grandchildren, etc. In the past, the “granny flat” was specifically for a family member.

By today’s code, the ADU can be rented out to family and/or non-family members for additional income to offset your mortgage payment or provide cash-flow. An ADU can help you monetarily as well as relive pressure on the local rental market.

My 3 favorite homes were actually ADUs. I had one in Alhambra and 2 in Pasadena. I had the comfort of a place of my own and I knew I was financially helping out a family who also lived on the same property with me.

If you’re thinking of adding an ADU to your R-1 zoned property, there are many benefits to doing so. If you would like, I can assist you with the design and permitting of your new ADU. If you have an existing non-permitted structure, I can help legalize that unit for you too.

House-hacking is one of my favorite strategies for getting ahead financially. An ADU is a great tool for adding rental income to offset your monthly expenses. If you have any additional questions about ADUs, please reach out to me.


Alan Pinel – Alpine Design