ADU 101

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.

Accessory Dwelling Units (ADUs) come in many shapes and sizes but are always a self-contained home that is 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 efficiency-size studios to 1,000-square-foot homes with multiple bedrooms.

Junior Accessory Dwelling Units (JADUS) are smaller units of up to 500 square feet of space within or attached to a single-family home (including within an attached garage). JADUs must include an efficiency kitchen (sink, cooking appliance, fridge, and small counter). Some JADUs have their own bathroom and some share with the main house. Construction costs for JADUs are typically much lower. In most cases, the property owner must live in the primary unit or the JADU.

State law now allows homeowners to have both a JADU and a regular ADU on their property.

This site walks you through each part of the ADU process, from gathering initial inspiration and learning what you can build through construction and becoming a landlord or moving in.

The best place to start is with a customized ADU Feasibility Consult to understand your specific property and local ADU rules. At the same time, you can work on thinking about what you want and looking at other ADUs to get a sense of what’s possible. Once you have some ideas in mind, you can move on to Learning the Rules to figure out what you can build on your property (the feasibility study will help with this too).

You’re not required to tell your neighbors about your ADU, but it’s always a good idea to communicate with them early in the process. Your project will run more smoothly if they are kept informed, and they may have great ideas for your project!

Some jurisdictions provide a courtesy notice about a project to the surrounding properties.

If you live in a Neighborhood or Homeowners Association, talk with your representative or board early in the process. They can’t prevent you from building or renting an ADU, but they may have guidelines you’ll need to know for design and construction. Depending on where you live, written approval from your HOA may be required before your location will permit your ADU.

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 local staff, 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.