BEFORE YOU BEGIN It is helpful to have a clear sense of what you want early in the process. An architect or designer can help you brainstorm, but they cannot start designing until you’ve made fundamental decisions like the type of ADU you want (see Getting Started) and how many bedrooms it will have, etc. If you join us for a 1:1 ADU feasibility consult , we will make customized recommendations for you based on your budget, property, goals, and local rules.

Consider Our Pre-Reviewed or Standard Plans

In 2022, we launched the Napa Sonoma ADU Standard Plans Program – a comprehensive gallery of “standard” ADU plans that have already been developed, saving you time and money and connecting you with an architect, designer, or prefab company. Some of these plans have also been “pre-reviewed” for code compliance, bringing you one step closer to building permits.

Visit the Plans Program website to browse the plans and learn more.

KEY RESOURCES

Hire Your Team

You can build an ADU as an owner builder, but bringing on a professional early in the process is often key to getting your ADU approved quickly, managed efficiently, and built cost-effectively. Relevant experience and fit are critical, and it’s important to look at their past work and check references.

Your team may include one or more of the following:

• Licensed architect or designer to design your ADU and potentially see you through permitting and construction

• Contractor to build your ADU

• Design/build company that designs and builds your ADU

• Modular/prefab company who sells preset designs for modular/prefab homes

Our ADU Workbook and Exercises include guidance on hiring professionals, contracts and costs, and a list of questions to consider when hiring a team, and our Vendor Registry includes a list of potential design professionals,

KEY RESOURCES

Create Initial Design

Once you have your team in place, you will work with them to design your ADU. Together you will consider size, use, layout, specific project needs (storage, laundry room, etc.), architectural style, and privacy. If you decide to go with one of the plans in the Standard Plans Program, you will work with the necessary professionals to customize the plan for your property. 

The design portion of an ADU project is driven by budget and choice. One of the first choices is size – the square footage of your ADU has ramifications on permit costs, total project costs, and of course, available living space and features. Size and features (such as a second bedroom, or washer/dryer combo) can often make a slightly larger ADU more valuable both to property values and potential rental income, but can also incur additional fees (500 square feet and 750 square feet are common cutoffs for certain fees).

You may also think about "Universal Design," the idea of making a space usable for the greatest number of people regardless of age, ability, or stature. This includes such things as putting light switches lower than standard to allow easier use from a wheelchair, lever handles for doors instead of knobs, and clearance in hallways and doorways to allow for ease of wheelchair or walker usage. If you plan to use your ADU for aging-in-place or senior family members, these decisions are crucial. 

It can be a good idea to involve a general contractor during this stage, since they can bring in up-to-date expertise in controlling construction costs. For example, a general contractor may suggest a simpler roof design to ensure that factory-built trusses can be used instead of a design plan that requires hand-framing the roof on site.

Once you have an initial design, it’s a good idea to discuss it with local Planning staff so they can point out any issues before submitting your permit application. Your design team can attend this meeting to clarify drawings and help you understand requirements. 

If you haven’t already, this is also a good time to reach out to utility service providers (water, sewer, gas, etc.) to confirm your design meets their requirements.

KEY RESOURCES

Finalize Your Design

Based on your meeting with staff, your team will work through any required changes and prepare the permit application (see Permitting).