Getting Started
Phase One
- Clarify what you want
- Find inspiration
- Estimate project cost
Project Timeline
Step-by-Step
Think About What You Want
Getting Started Step 1
Start by thinking about your short- and long-term goals and concerns for your ADU project and what kind of ADU is best for your needs. Our ADU Exercises have a checklist to get you started.
Good sources for inspiration:
- Floorplans inspiration gallery
- Local and statewide ADU stories
- Casita Coalition website
- Talk to friends and neighbors who have built ADUs – ask them what they like and what they wish they’d done differently.
Think about what it means to share space with tenants and if that impacts your design and layout. Keep in mind that your plans may change once you hire a professional. Be flexible and open to the possibilities!
Key Resources
Consider different types of plans
Getting Started Step 2
There are multiple kinds of ADU plans for you to consider:
Site-built plans Site-built is a traditionally constructed ADU built from scratch on your property (AKA “stick-built”). This option allows for a lot of customization and smaller changes throughout the construction process.
Prefabricated, modular, panelized plans Prefab, modular, and panelized are partially or mostly built in a factory, then shipped to your site and assembled or placed on a foundation. Some companies provide a “turnkey” service that helps with permitting and all on-site construction, from laying the foundation to utility hookups. If not, you’ll need to hire additional professionals to help.
Using a prefab design can save time and make clearer what your completed project will look and feel like, but they also typically offer less customization, can be difficult to permit and finance, and often cost the same as site-built ADUs. People are often surprised at the cost, but transportation, crane, foundation, and sales tax can end up being 20-40% of the total cost. Some companies do offer a smaller price point.
To explore prefab or modular ADU options, you will want to get in touch with companies directly. They will visit, evaluate your property, and make recommendations. You can find prefab contractors by researching online.
Make an informal sketch
Getting Started Step 3
A major part of pre-work is figuring out where an ADU would make the most sense on your property. Start with making a rough sketch of your property, including the existing home, any other structures, and space for a possible ADU. Our ADU Workbook includes more details to help you with this step. (Note: You can update this sketch or make new versions as you continue to learn about your property and what’s possible.)
For some properties, doing this sketch and deciding where your ADU will go is fairly easy because there is limited space and only one option works for their desired size. For those who are trying to choose between different areas, or different types of ADUs, such as a detached ADU vs one built above your garage, you may want to get early consultation from tradespeople and other experts who can spot opportunities or challenges. For instance, plumbers can help identify where the sewer line might run.
Key Resources
Estimate project cost
Getting Started Step 4
It’s never too early to start thinking about and planning for your project budget. A very rough placeholder for you to use is $400-500 per square foot, including construction and other costs (design, fees, etc.). The real number can vary widely and depends on many factors. Our ADU Calculator is a great place to start when developing a budget. It provides a rough estimate of costs and income and will help you understand how choices can impact your budget over time, all customized to real local numbers.
See Budgeting & Finance for more information. Our Workbook also contains details regarding the cost of ADU design, permitting, and construction. Plus, watch our candid conversation with ADU finance experts about whether or not ADU costs pencil out in your favor in the current economy.
Related Blog posts
FAQs
Find answers to the most frequently asked questions about getting started.
What is the difference between an ADU and a JADU?
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.
What do I have to do to build an ADU?
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.
What do I do first?
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).
Do I need to tell my neighbors?
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.
I’m looking to put an ADU on new property – what should I be looking for?
This is a great thing to be thinking about before you purchase! We’ve written a guide to what you should be thinking about and looking for.
How long does it take to build an 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.
When do I need to think about utility connection?
Utility connections can have significant design and scheduling impacts, so it’s good to think about them early on.
In general, it is less expensive to hook the ADU utilities to the main house, as opposed to building new water and sewer laterals to the mains in the street, or a second set of electrical lines from the pole. In some cases, particularly if your ADU is larger, over 750 sf, you may be required to construct new connections. It is best to discuss this issue with your jurisdiction early in the design process.
Most homes will need to upgrade the main electrical panel and possibly electrical service to the property. This will involve both an electrician as well as coordinating with PG&E. Due to the demands on PG&E services, the upgrade process can take significant time and homeowners are often charged a $1,500 engineering fee for PG&E to begin the process. Additional fees may be charged depending on the condition and size of the electrical components running to the property.
Typical utility upgrades for an ADU include a main electrical panel of at least 200 Amps and a sewer lateral of 4″ for the whole property. If the existing lateral is 3″ you may have to replace it with a 4″ lateral to the street to handle the additional demand created by the ADU. Please consult with your building department for more information.
Water service may need to be upgraded as well, particularly when sprinklers are required such as when an ADU is built above a garage. The scale and cost of this work depends greatly on the age of the main house and the infrastructure provided by jurisdiction. It is important to determine if sprinklers will need to be planned for and get information on the water supply to your property early in the design and bidding process. This information is typically available from your Public Works or Engineering Department.
At what stage of the ADU process should I get an ADU Feasibility Consult?
As early as possible! The goal of the consult is to make sure you have a deep understanding of the best ADU options for you given your goals and budget objectives. Doing so will save you time and resources in the long term. If you’re already far along in the process with a designer or architect, you may no longer need an ADU Feasibility Consult – instead, just reach out to us if you have questions along your ADU journey.
