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
Detached
New freestanding structure separate from the main home, like a backyard cottage.
Attached
New structure (may include some converted space) sharing at least one wall with the main home.
Conversion
Converted existing space in the main home or on the property (bedroom, basement, detached garage).
JADU
Multi-family
Not an adu
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.
The best place is to think about what you want, understand your goals and concerns, and look at other ADUs for inspiration. Once you have some ideas in mind, consider your budget and move on to Learn the Rules.
Building an ADU is an investment of time as well as money. Most projects take one to two years to complete. Typically, it takes homeowners one to three months to get started and assemble their team, then one to six months to develop plans, meet with the city, and submit the application. Depending on what permits are required, how many rounds of review are required and how quickly a homeowner and their project team can respond to comments, it will take one to six months to get permits. Construction usually takes six to twelve months.
Accessory Dwelling Units (ADUs) 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 typically range from studios under 500 square feet to large homes with multiple bedrooms.
Junior Accessory Dwelling Units (JADUs) are within the footprint of your home (or attached garage) and less than 500 square feet. They can share a bathroom with the main home and/or have an efficiency kitchen (sink, cooking appliance, fridge, and small counter). Construction costs for JADUs are typically much lower. In most cases, the property owner must live on site in either the main home or the JADU.
State law now allows homeowners to have both a JADU and a regular ADU on their property.
Site-built/Traditional: A traditionally constructed ADU is designed and built specifically to your preferences and property and built on site (“stick-built”). This option allows for a lot of customization and smaller changes to be made throughout the construction process.
Prefabricated/panelized/modular: These ADUs are partially or mostly built in a factory, then shipped to your site to be put together. Sometimes the company will include all services in their fee (“turn-key”), including help with permitting and all on-site construction tasks (e.g., laying the foundation, utility hookups, etc.). Other times you’ll need to hire additional professionals to help.
Are you ready to ADU?
We have resources to help you at every step of the way, from initial thoughts through move-in.
