What to Look for While Building an ADU in California? 12 Expert ADU Tips 

ADU tips

Considering expanding your home? Building an accessory dwelling unit (ADU) is a great solution. This addition provides extra living space without the need for a major relocation. If you are a homeowner seeking to establish a separate space for guests, a workspace, or a rental opportunity, an ADU might be the ideal choice. It is important to understand the laws and processes due to varying zoning restrictions, HOA regulations, and building laws in each city to build an ADU. 

12 Expert ADU Tips 

While ADUs offer an excellent income opportunity, several challenges need careful consideration before starting the construction process. Here are 10 crucial factors to consider before entering your ADU project: 

1. Property Development Standards & Regulations 

Living in a rural area or an HOA-restricted community brings its own set of regulations for building an Accessory Dwelling Unit (ADU). In California, homeowners enjoy considerable flexibility, as obtaining a permit for an ADU is generally allowed, except under specific conditions. The state actively promotes ADUs as a solution to its housing crisis, providing an affordable housing option.  

Recent changes in California law have reduced the waiting period for the ADU approval process from 120 days (about 4 months) to 60 days (about 2 months). However, exceptions may apply.  

It is essential to consult local government officials to understand and comply with the specific standards in your area. 

2. Privacy Concerns 

When considering the construction of Accessory Dwelling Units (ADUs), it’s essential to understand that these residences are connected to a primary dwelling with foundations, plumbing, and utility connections. Privacy considerations for ADUs can vary based on the occupants. For family members, a communal living arrangement might be acceptable. However, when leasing to tenants, privacy becomes paramount. Using window blinds, landscaping, and fencing ensures both aesthetic appeal and privacy. 

Formal or legal agreements outlining property usage can also prevent potential conflicts, fostering a comfortable living environment for all.  

3. Design Guidelines 

Consider aligning your new ADU’s design with your existing home’s layout and architectural style. If your residence is made of brick, opt for materials like concrete, wood, or cut stone to maintain cohesion. Straying from your home’s style can reduce property value, complicating future sales.  

Moreover, ADU design varies between counties and cities, subject to local codes and regulations. Compliance is key, with most units necessitating bathrooms, kitchens, and proper heating systems. Consulting Structural and MEP design experts or local building departments ensure compliance and is crucial in building an ADU. 

4. Access to the ADU 

Ensuring accessibility is crucial when building an ADU. The unit must be easily reachable and safe for its occupants, requiring a designated walkway. It is essential to keep the passage between your home and the property line clutter-free.  

Creating separate entrances, even for attached ADUs, such as installing a unique backdoor for ADU residents, enhances privacy. Moreover, addressing the needs of older family members is important. For instance, if an elderly family member resides in the ADU, installing wheelchair ramps and handrails will help enhance mobility. 

5. Fire Regulations 

While building an Accessory Dwelling Unit (ADU), considering and implementing fire regulations ensures the safety of occupants. It is essential to be aware of specific requirements for fire safety. Consulting local fire and building officials is essential to understanding and meeting these regulations, including the potential mandatory installation of sprinkler systems. Even if not required, installing a sprinkler system can enhance safety and potentially reduce insurance costs, making it a wise investment. 

6. Site’s Condition 

Understanding your site conditions is crucial when planning an Accessory Dwelling Unit (ADU) project. Whether your backyard is sloped or flat, and if there is rainwater pooling, knowing these details can help you cut costs and prevent future complications. An ADU built on disturbed soil may damage the foundation over time, necessitating replacements. If your yard has drainage issues, addressing them before construction is vital to avoid water pooling around the new structure.  

7. Utility Connections 

When considering utilities for your new ADU, planning for electricity, water, and sewage is crucial. Generally, tapping into your primary residence’s water source and gas lines is convenient, saving the need for new installations. However, your current setup might be unable to manage the increased sewage load. So, upgrading or installing a new system is necessary. 

Additionally, if you plan to rent out the ADU, decide in advance how to handle utility costs—whether included in rent or billed separately.  

8. Type of ADU 

An ADU is like a versatile extra space for your home. It’s not the same for everyone—it comes in different types. Explore these various styles of ADUs to find the one that is right for your home: 

a) Detached ADU 

A detached ADU is not connected to the main house. People usually build these small homes in the backyard, but they can also put them next to the main house.  

A detached ADU is ideal if a homeowner wants to rent the space to someone they don’t know well. It offers privacy and clarifies boundaries between the main house and the additional unit. 

b) Attached ADU 

An attached ADU is like a new part of your existing house. This extra part connects to a room in your main house, like a back bedroom. Usually, the attached ADU has a separate entrance. But sometimes, the people living in it might need to go through a part of the main house or a shared area for both homes. 

c) Attached (Above Garage) AADU 

Some homeowners choose to add a new space on the top of their garage instead of expanding their house outward. It is a smart way to save space, but this kind of project can be complicated also. The builder needs to put in a new roof and a vapor barrier to keep car exhaust out. 

d) Interior (Converted Garage) ADU 

Is your primary home’s garage gathering dust and cobwebs without much use? If yes, consider transforming it into ADU. Your contractor can put up walls to create smaller rooms, turning your garage into a cozy apartment space. 

e) Interior (Basement) ADU 

Your basement might be overlooked, but it is a valuable space you can turn into an investment. If you don’t use it much, think about converting the basement into a living space. It is a way to make your home more enjoyable, adding value to it. 

f) Interior (Upper Floor) ADU 

Imagine your kids have moved out, leaving their old bedrooms and playrooms empty. Instead of leaving that space unused, you can transform it into an Accessory Dwelling Unit (ADU). 

9. Purpose of ADU 

Why do you want to make an ADU? If you’re not sure why, you might end up spending a lot of money and resources on a space you won’t use. Here are some reasons you might consider for building an ADU. 

a) Gym 

If you struggle to complete workouts at home, consider creating a dedicated gym space. Equip it with essential workout gear, including an elliptical, treadmill, and dumbbells. This allows you to exercise without any interruptions, developing a focused workout environment. 

b) Home Office 

Attempting to work in shared areas like bedroom or kitchen can be challenging due to distractions. For those seeking a dedicated work environment, the option of constructing an ADU office is worth exploring. Complete this space with all necessary work essentials.   

Moreover, having the convenience of a nearby kitchen and bathroom ensures you can stay in the work zone without the need to leave for meals or restroom breaks. 

c) Guest Room 

If you enjoy having guests over but want to keep your personal space, consider building an ADU. This separate space can be for any family or friends visiting, giving everyone their own area. 

d) Family Member’s Home 

An ADU, also known as a granny flat, is an ideal solution for additional family members. It offers a separate living space for one person or a small family, complete with their own kitchen, bathroom, and bedroom(s). They won’t have to visit the main house, but you can still be close to each other. Also, you can spend time together and assist them with household tasks. 

e) Renting Space 

Ever thought of generating passive income? Becoming a landlord is a way to do that. Many people make passive income by renting out their extra space, like an Accessory Dwelling Unit (ADU). Renting out your ADU can be a great way to generate income. Your new space can start paying for itself in a few years, giving you extra cash. 

10. Hire Professional Help 

Starting to build an ADU might seem challenging, but it’s best to get help from local experts. If you are confused about how to build an ADU or how to build an ADU cheaply, look for professionals who are familiar with your area. Specifically, look for a local contractor experienced in building ADUs.  

11. Saving Space 

It is crucial to consider storage, appliances, and furniture size when dealing with a small space. Choose items that can fit well in an ADU while still leaving enough space for the occupant. Utilize wall-mounted storage, avoid bulky furniture, and consider tables and chairs that can be folded away. Incorporating space-saving features into your home design will enhance your overall living experience. 

12. Parking 

In certain places, you might need to arrange a parking spot for your ADU. However, if your unit is near public transportation or in an important historical area, parking may not be a concern. Since the rules vary, it’s best to contact local officials to find out if you need to provide parking for your new unit.  


Building an ADU home can be an ideal investment, but it’s important to consider the above-discussed things before initiating. First, check if it’s suitable for your property. Talk to experts about design and construction. Once you have a good-to-go plan, you can start building the ADU structure. 

Contact us at BFPM for any queries about ADU building or property management. Our expert team of professionals is here to help! 

Trevor Henson

Trevor Henson is an experienced entrepreneur (10+ highly-successful start-ups) and property investor with a demonstrated history of building and leading teams in investment property management environments, maximizing returns for property owners, and optimizing properties through construction management and re-positioning. He…
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Frequently Asked Questions(FAQs)

Here are some tips to maximize space in an ADU:

  • Multi-functional furniture
  • Vertical storage
  • Foldable furniture
  • Light colors and mirrors
  • Compact appliances and much more

Absolutely, it proves to be a dependable long-term investment. It not only enhances your property's value, but you can generate passive income by renting out your ADU.

The increase in property value due to an ADU varies but often ranges between 20% to 30%. Factors influencing the impact include location, size, and the quality of the ADU construction.