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How Many Bedrooms can an ADU have?

July 14, 2023

An Accessory Dwelling Unit (ADU), a granny flat or in-law suite, is a secondary residential unit located on the same lot as the original (primary) dwelling. Many property owners are drawn to the prospect of being able to build an ADU in their existing structures or lots due to their numerous benefits. 

Understanding the regulations surrounding ADUs, particularly with regard to the number of bedrooms, lot size requirements, and floor area ratio, is crucial to successfully planning and constructing an ADU.

What is an ADU?

An Accessory Dwelling Unit (ADU) is an additional residential structure that can be constructed on a lot already housing a standalone single-family home. ADUs can be detached, attached to the existing structure, or even formed through the conversion of a garage. Each type of ADU, whether it’s a detached ADU or a junior accessory dwelling unit, has its own unique set of guidelines, particularly when it comes to size limit and square footage.

Regulations Governing ADUs

The planning and construction of an ADU require a deep understanding of various regulations, which often vary by state and locality. Rules concerning the number of bedrooms, square footage, the height of the ADU, and the required setbacks from property lines are all aspects to consider.

Lot Size

Some jurisdictions stipulate that your lot must be of a certain size before you can build an ADU. In addition to this, there could be rules about the maximum size of the ADU relative to the primary dwelling, often expressed as a floor area ratio. This ratio is a measure of the ADU’s size compared to the total lot size, and it’s a critical parameter in ADU construction.

Bedroom Count

A key consideration for potential ADU builders is the number of bedrooms allowed. Local ordinances and state laws may limit this aspect, depending on the lot size and ADU size. For instance, in some places, a lot must be at least 7,500 square feet to host an ADU with two bedrooms. Understanding these rules is vital in the early planning stages.

Parking Requirements

Parking requirements are another crucial consideration when planning an ADU. Some jurisdictions require off-street parking spaces for each bedroom in the ADU, which could limit the number of bedrooms you can add if space is at a premium. However, other areas might have more relaxed rules, particularly if the property is within a certain distance from public transit options.

These are just a few examples of the regulations you’ll need to navigate when planning to build an ADU. Each city and county will have its own specific requirements and procedures for obtaining the necessary permits. While these rules may seem daunting, they are there to ensure that the construction of ADUs is carried out in a way that is safe, equitable, and respectful of the local community’s character.

How Many Bedrooms Can You Have?

The number of bedrooms in an ADU can have depends largely on the unit’s total allowable size, which is influenced by the floor area ratio and local ordinances. 

Some jurisdictions may have a size limit of 500 square feet for ADUs, allowing only for a one-bedroom unit, while others may allow for larger ADUs up to 1200 square feet, permitting two or more bedrooms. Side and rear setback requirements, as well as lot coverage requirements, can also dictate the number of bedrooms you can include in your ADU.

Benefits of Adding Bedrooms

Adding bedrooms to an ADU of up to 16 feet high could provide various benefits. Multiple bedrooms can yield a higher rental income if the ADU is rented out, increase your property value, and provide additional living space for family members or guests. However, be mindful of the regulations that might limit the size of your ADU to a maximum of 150 square feet per room for certain types of ADUs.

Things to Consider When Adding Bedrooms to an ADU

Adding bedrooms to your ADU certainly extends its functionality and potential usage. However, it also necessitates careful consideration of several factors, including space management, cost, and the intended use of the ADU. Your goal should be to maximize space without compromising the comfort and functionality of each room. Thoughtful design can ensure that even compact ADUs don’t feel cramped but instead offer cozy and efficient living quarters.

Space Management

While it might be tempting to squeeze in as many rooms as possible, it’s important to consider the implications of living comfort. Each room should be adequately sized and functional, conforming to local regulations regarding minimum room size. Overcrowding your ADU can lead to a claustrophobic atmosphere and may detract from the overall appeal of the dwelling.


Each additional bedroom adds to the construction costs, including materials, labor, and potentially, the cost of permits. Understanding your budget constraints will help guide decisions on the number of bedrooms to add. Moreover, keep in mind that while more bedrooms could potentially increase rental income, they also increase the upfront investment required.

Intended Use

If you plan to use the ADU for rental purposes, more bedrooms could make it more attractive to potential tenants. Conversely, fewer but larger rooms might be more appropriate if the ADU is intended for a single family member or a home office.

State Laws & Local Ordinance 

These laws may limit the maximum ADU size, the number of bedrooms allowed, and the requirements for amenities such as parking. Ensuring your project is compliant not only avoids potential legal issues but also ensures your ADU will be a valuable addition to your property.

Adding bedrooms to your ADU is not a decision to be taken lightly. By considering these factors and working with experienced professionals, you can create a space that serves your needs and enhances the value and functionality of your property.

About Los Angeles ADU Builder

With a wealth of experience in constructing ADUs, Los Angeles ADU Builder can guide you through the process of determining how many bedrooms your ADU can have while ensuring compliance with local regulations. They specialize in creating ADUs that maximize the potential of your property while meeting all state laws and local ordinances. 

If you’re looking to add bedrooms to your ADU, trust the experts at Los Angeles ADU Builder. Reach out to them today to transform your ADU plans into a reality.

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