Throughout California, more and more homeowners are exploring the possibility of adding an ADU (accessory dwelling unit) to their property. However, just because lawmakers have removed many of the restrictions that once made it nearly impossible to build an ADU doesn’t mean the process is always easy. There are still potential hurdles that can add unnecessary time and expense to building an ADU, if they don’t stop your plans completely.

Regardless of possible difficulties, building an ADU has significant benefits that have motivated thousands of homeowners to proceed with construction in the last several years. Whether they’re built as a granny flat to house an aging parent in comfort and independence, an affordable space for a college graduate returning home to launch their career, or a rental unit to generate income, ADUs create much-needed housing and boost property values for their owners. Knowing the potential pitfalls before you rush into construction can help you navigate the process more easily and avoid costly mistakes.

Design Constraints

Where and how you can build an ADU are governed by state and local ordinances. If your local jurisdiction has not imposed additional limitations, a detached ADU in California can be up to 1,200 square feet and 16 feet high, with four-foot side and rear yard setbacks. State rules do not impose any requirements based on floor-area-ratios (FAR), lot coverage, open space, or minimum lot size. If you live in an area with its own ADU ordinances, you may be limited to 850 square feet (or 1,000 square feet if the ADU has 2 or more bedrooms), and there may be specific requirements for FAR, lot coverage, open space, and minimum lot size.

Your project may also have site-specific considerations to take into account, such as ensuring that utility services like water, sewer, and electrical services can be connected correctly. While in some cities it is possible to obtain pre-approved plans for an ADU, in general, it is prudent to work with an architect experienced in ADU design in your area to ensure that your plans meet all state and local requirements as well as fitting your needs. Hometelligent has worked with architects throughout the Bay Area on ADU projects and can provide referrals.

Government Approval and Permitting

Obtaining the necessary approval and permits to start construction are one of the most challenging parts of building an ADU. Homeowners are often not prepared for how long and complex it can be to decipher and comply with the requirements of different departments, and they may fail to budget for permitting fees. Unfortunately, mistakes in this area can delay construction, so it pays to do your homework and get it right the first time.

It’s essential to work with a contractor experienced with the ADU permit process in your area to ensure that your building plans fit all the necessary requirements. Review your county’s ADU requirements checklist to be sure that you have all necessary documents for your submittal; incomplete applications will be denied, sending you to the back of the line. Most importantly, don’t file for permits at the last minute.

It can take months for a permit to be approved, so you should leave plenty of time before your planned start date for the permitting process. Keep in mind that the purpose of permitting requirements is to ensure that all new structures meet safety codes, so be polite when you’re dealing with the permitting department, even if you’re frustrated.

For homeowners daunted by the process, Hometelligent has extensive experience in permitting in jurisdictions throughout the Bay Area. We can help determine what you need to get your permit approved on the first try.


Depending on the size and scope of your ADU costs, it can range from tens of thousands to hundreds of thousands of dollars. While sometimes homeowners have saved up over a period of years to pay for an ADU financing, it’s often the case that they need to borrow some or all of the funds needed to finance the project.

Possibilities for obtaining funding include a cash-out refinance, a home equity loan or home equity line of credit (HELOC), a construction loan, or a personal loan. In addition, for low to moderate income homeowners, grants of up to $40,000 may be available through the California Housing Finance Agency to help with predevelopment and non-reoccurring closing costs associated with the construction of an ADU.

The best option for your project will depend on your individual circumstances and if you have equity built up in your primary residence. You should consult your financial advisor well in advance of your planned start date to put any necessary financing in place before you break ground, to ensure that cash flow problems don’t halt your project midway.

Seasoned ADU Construction

While every construction project has its challenges, an experienced, knowledgeable contractor can help ensure that you aren’t held up by avoidable problems. Hometelligent has built numerous ADUs throughout the Bay Area, and we understand the local nuances that can affect the building code and permitting process. If you need a contractor and project manager dedicated to producing top-quality work on time and within budget, we can help. To find out more about how we can make your Bay Area ADU plans a reality.