What is the best size for an ADU?

Accessory Dwelling Units (ADUs) have become increasingly popular among homeowners in recent years. These versatile living spaces offer various benefits, from providing additional rental income to creating a cozy guest house or home office. But what is the best size for an ADU? The answer depends on several factors, including available space, local regulations, and intended use. In this comprehensive guide, we'll explore these considerations to help you determine the optimal size for your ADU.

Defining the Best Size for an ADU

Choosing the right size for your ADU involves considering several key factors:

1. Available Space

The first thing to consider is the space you have available on your property. If you have a large backyard, a detached ADU might be a perfect fit. For those with limited space, an attached or internal ADU may be more suitable.

2. Local Regulations

California State code allows for a detached ADU to be built up to 1,200 square feet. However, local cities and counties can impose their own restrictions. For instance, about 391 cities and counties follow the state code, but others may have stricter size limits. Approximately 150 cities and counties limit your detached ADU size based on your design plans. Typically, detached ADUs with two or more bedrooms are limited to 1,000 square feet, while those with one or fewer rooms are limited to 800 square feet.

Keep in mind that these are general guidelines, and your specific city may have different regulations. Always check with your local government or planning office for the most accurate information.

3. Intended Use

The intended use of your ADU plays a significant role in determining its size. Here are some common uses:

• Guest House: A smaller ADU, around 400-600 square feet, is often sufficient.
• Home Office: Depending on your needs, a compact 150-300 square feet space may be ideal.
• Rental Unit: For a rental, you might want a larger unit, up to 1,200 square feet, to attract tenants looking for more living space.

4. Types of ADUs

There are four main types of ADUs:

• Detached ADUs: Separate from the main house and offering more privacy.
• Attached ADUs: Connected to the main house but with a separate entrance.
• Conversion ADUs: Created by converting existing structures like garages.
• Internal ADUs: Built within the existing floor plan of the primary residence.

5. Regulations for Specific ADU Types

• Detached ADUs: Generally, they can be up to 1,200 square feet, but local rules apply.
• Attached ADUs: Usually cannot exceed 50% of the primary home's square footage and must not be taller than the existing home.
• Conversion ADUs: Often have no maximum size limits as they are based on existing structures. However, Junior Accessory Dwelling Units (JADUs) must be under 500 square feet.
• Internal ADUs: Constructed within the existing home, with fewer regulations.

6. Minimum Size Requirements

According to California State code, all ADUs must be at least 150 square feet, regardless of type. Exceptions do exist, so it's important to verify specific local regulations.

• ‍Contact our ADU experts 

Determining the Optimal ADU Size

Understanding Local Regulations

The California Department of Housing and Community Development (HCD) states that local governments can apply development and design standards, including maximum size limits. This means local regulations can either loosen or tighten the state's general ADU size limits.

To find out your specific area's ADU laws, contact your local government or planning office. Many cities also have websites with detailed information about their ADU regulations.

Loopholes to ADU Size Regulations

While local governments can impose their own rules, there are certain state-mandated exemptions. For example, the maximum square footage should not be below 800 square feet. Additionally, even if local ordinances are stricter, they must allow ADUs up to 800 square feet and less than 16 feet high, provided there are 4-foot rear and side yard setbacks.

Best ADU Size in California

If you're planning to build an ADU in California, consider keeping it under 750 square feet. ADUs of this size are exempt from bulk and massing development limits, such as lot coverage restrictions.

Economic and Lifestyle Benefits of ADUs

ADUs offer numerous economic and lifestyle benefits:

1. Additional Income

Renting out your ADU can provide a steady income stream, helping offset mortgage payments or other expenses.

2. Multigenerational Living

ADUs are perfect for multigenerational families, offering a private living space for elderly parents, adult children, or other relatives.

3. Increased Property Value

A well-designed ADU can significantly increase your property’s value, making it a smart long-term investment.

4. Flexible Living Spaces

Whether you need a home office, a guest suite, or a rental unit, ADUs offer flexible solutions to meet your needs.

Conclusion

ADUs offer incredible flexibility and value for homeowners. By considering factors like available space, local regulations, and intended use, you can determine the best size for your ADU. Don't forget to check with your local government to understand specific regulations and take advantage of any loopholes.

Ready to explore your ADU options? Consider what size will best suit your needs and start planning your project today. And if you need expert advice, feel free to ‍contact our ADU experts .

‍