ADU 101

Let's start from the beginning

What is an ADU?

Accessory dwelling units (ADUs), also known as “granny flats,” “in-law units,” or “backyard cottages,” come in many shapes and sizes but are always a self-contained home that is usually smaller than the main house and legally part of the same property. They must have a kitchen, bathroom, and place to sleep, and can range from studios small studios under 500 square feet to larger homes with multiple bedrooms.

Types of ADUs


New freestanding structure separate from the main home, like a backyard cottage.


New structure (may include some converted space) sharing at least one wall with the main home.


Converted existing space in the main home or on the property (bedroom, basement, detached garage).


A type of conversion up to 500 square feet within the main home (existing or proposed).


Any of the above (except JADU) that is part of a multi-family building (existing or proposed).

Not an adu

RVs, tiny homes on wheels, yurts, and storage structures are NOT accessory dwelling units.

ADUs do not always fit neatly into one category – like an attached ADU made from converted space, for instance.

Project Timing

Building an ADU is an investment of time as well as money. Most projects take 12-24 months to complete, with interior conversions being the fastest.

Why Build an ADU?

Building an ADU is an investment in your property, your family, and your community.

ADUs often provide homes for the local workforce and small families who have difficulty finding local housing that meets their needs. For homeowners, there are many reasons to build an ADU — rental income, safe and convenient housing for relatives, flexibility over time, and many others.

Here are some of the reasons why people build ADUs:

Housing Family

Close but independent living for adult children, aging relatives, or loved ones with special needs.

Rental income

A steady source of additional income for retirement or a rainy day. Can come from the ADU or the main home.

A Home As You Age

A nearby home for caregivers or for aging adults who want to rent their main home and live in their ADU.

Extra Hands

An extra set of eyes and hands on your property can be helpful for safety, when you travel, upkeep, and more.

Community Housing

Provide housing to families, workers, and others who might struggle to find something local.

Property Investment

Not only will you receive rental income in the short term, but your sale price and property value can increase too.


Find answers to the most frequently asked questions about ADU basics.

Are you ready to ADU?

We have resources to help you at every step of the way, from initial thoughts through move-in.

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Tell us your thoughts!

Please give us feedback about ADUs in our area. If you leave your contact info, we may be able to get back to you with more information. 

If you’re looking for specific advice or information about your property and ADU, please use the contact information for El Dorado County or the City of Placerville at the bottom of this website. 

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