All About ADUs with Garages

Adding an accessory dwelling unit (ADU) with a garage can take several forms, from an above-garage ADU (also called a carriage house) to an ADU with an attached garage next to it, or a garage conversion that transforms an existing structure into livable space. Whether you’re looking to build new construction or repurpose your existing garage, these ADU options offer flexibility for rental income, multigenerational living, or additional storage and workspace.

Types of ADUs with Garages

Above-Garage ADU (Carriage House): An above-garage ADU maximizes space by stacking a living unit on top of a garage. This is a great solution for homeowners looking to preserve yard space while adding rental or guest housing.

ADU with an Attached Garage: An ADU with an attached garage is a single-story or two-story unit built next to a garage. The garage may be connected directly to the ADU or separated by a breezeway. This layout is ideal for homeowners who want additional storage, workshop space, or parking alongside their ADU.

Garage Conversion ADU: A garage conversion repurposes an existing garage into a fully functional ADU. This option is often the most cost-effective since the structure already exists.

Above Garage ADU (Carriage House)

An above garage ADU, also known as a carriage house, is an accessory dwelling unit built above an existing or new garage. These units feature all the essentials of a home, including a kitchen and bathroom. Homeowners build ADUs above garages for rental income, guest accommodations, or multi-generational living, making them a versatile and valuable property upgrade.

Carriage House Meaning and Origin

The term “carriage house” dates back to the 18th and 19th centuries, referring to outbuildings designed to store horse-drawn carriages. Over time, as automobiles replaced carriages, these spaces evolved into living quarters for staff or rental housing. In modern real estate, carriage houses have become synonymous with above garage ADUs, particularly in urban and suburban settings where homeowners seek efficient ways to add livable space while retaining valuable storage and parking space.

Benefits of Building an Above Garage ADU

An above garage ADU allows homeowners to add livable square footage without expanding the footprint of their home when there is an existing garage. This is especially useful in areas where lot sizes are small or the homeowner values retaining backyard space.

Rental Income. Building a carriage house can generate passive income by renting it out as a long term or short term rental. Homeowners in cities with high rental demand like San Diego can see significant returns by utilizing this extra space. Read more about renting your ADU.

Multigenerational Living. ADUs above garages are a great solution for housing aging parents, adult children, or guests while maintaining privacy. They offer a separate, self contained space with close proximity to the main home while retaining valuable parking. Read more about multigenerational living with ADUs.

Property Value. A well designed above garage ADU increases property resale value. Buyers recognize the benefits of extra living space and rental potential, making these units a smart long-term investment. Read more about investing in an ADU.

Requirements for an Above Garage ADU

Zoning and Permitting Regulations

Before building an above garage ADU, it is essential to look into local zoning laws and ADU regulations. Many cities have specific regulations such as the following:

• Height restrictions (typically 16 to 25 feet max, but will depend on specific property zoning).
• Setback requirements from property lines. Required setbacks are often greater for two story structures.
• Parking regulations (most cities waive parking if near public transit).

This is an area where SnapADU stands out. To learn more about whether you are able to build an ADU above your garage, start with our summary below, and reach out to our expert team with questions about your property.

TABLE: ADU Over Garage Regulations By City

Source: SnapADU & local regulations

Cost of Building an ADU Above a Garage

Factors That Affect Costs

Building a new construction garage with an ADU above typically costs between $350K and $500K+ all-in. The all-in ADU cost depends on several key factors. The size and design complexity play a significant role, as larger or more intricate layouts require more materials and labor. Custom features such as upgraded finishes or high-end appliances can further increase expenses. Since prefab construction is not an option for above garage ADUs, all builds require traditional, stick-built construction, making careful budgeting essential.

Structural Considerations (especially for conversions)

If the homeowner is looking to utilize the existing structure, a structural engineer must assess the garage’s foundation and load capacity. Reinforcements may be required to meet safety codes. In many cases, it makes more sense to demolish the existing garage and start from scratch, which is what SnapADU specializes in. We recommend taking a read through our blog post on garage conversions vs. demolition.

Financing Options

Several ADU financing options are available to help homeowners fund their ADU projects. Home equity loans allow homeowners to leverage the value of their existing property, making them a popular choice for ADU financing. Construction loans are another option, providing funding specifically for building projects and allowing for phased payments as the work progresses. Exploring these financing options early in the planning process can make budgeting for an above garage ADU more manageable. SnapADU can help connect you to reputable lenders.

Popular Above Garage ADU Floor Plans

Studio & One Bedroom Layouts

Studio and 1 bedroom above garage ADUs typically range from 400 to 600 square feet, making them an efficient use of space while still providing a fully functional living area. These units are most commonly built above a standard two car garage, offering a compact yet comfortable design. A well planned 500 sqft one bedroom carriage house can include an open concept living area, a full kitchen, a private bedroom, and a bathroom.

Two & Three Bedroom Layouts

For homeowners looking for additional space, two and three bedroom layouts typically range from 700 to 1,000 square feet. These larger units are often built above a 3 car garage or a 2 car garage with extra storage space. For example, our 750 sqft two bedroom carriage house plan features an open living and kitchen area, two well-sized bedrooms, and a shared bathroom, making it a great option for small families or tenants who need more space.

Alternative Layouts

Not all above garage ADUs are designed with a full garage underneath. Some homeowners opt to use the first floor for storage instead of parking, creating a two story ADU with flexible usage. An example is our modern two-story ADU in Pacific Beach, where the ground level serves as storage while the living space is located upstairs. Other designs incorporate a hybrid approach where part of the first floor is a garage and the rest is used as living space with additional living space upstairs. An example of this is this custom two-story ADU in Oceanside where there is one bedroom and a garage downstairs and living space with a deck upstairs. Because carriage houses are stick-built, there is significant flexibility in design, allowing homeowners to create layouts that best suit their needs.

ADU with an Attached Garage

For homeowners who need extra storage, parking, or workspace, an ADU with a garage offers a practical solution. Unlike an above-garage ADU, this design keeps both structures at ground level, making it a more accessible option. The garage can be used for vehicle parking, additional storage, or even as a workshop while the ADU remains a separate, fully functional living space. An attached garage can later be converted into extra living space or a home office if parking is no longer needed for the ADU. See ADU projects with garages.

Key watchout: Setbacks for garages attached to ADUs may not be reduced

Keep in mind that garages may be subject to different setbacks than an ADU. Typically, garages will be subject to underlying setbacks for the property, even though the ADU may enjoy reduced setbacks. However, there are additional details to be aware of. For example, in San Diego, when it comes to alleyways — with 15′ alleyways being quite common — garages need to maintain a setback of 6′ from the rear property line:

“Where access for parking is taken from the alley and the parking spaces are not parallel to the alley, a minimum distance of 21 feet shall be provided between the edge of the alley public right-of-way opposite the lot and the outside edge of the parking garage or parking stall closest to the alley (San Diego Municipal Code, Article 1: Base Zones, Division 4: Residential Base Zones, §131.0443 Setback Requirements in Residential Zones).”

ADUs with Detached Garages

We have also taken on projects in which the homeowner chooses to build an ADU and a detached garage such as this 1,200 sqft ADU with a large two car garage in Rancho Santa Fe. This is another option to consider when the property has extra space and the homeowner prefers separation between the ADU and garage. It is important to note that like for attached garages, detached garages will also follow setbacks and lot coverage per underlying zoning.

Does the garage square footage count towards the ADU total?

No, the square footage of the garage does not count toward the total allowable square footage of the ADU. Under California ADU regulations, the livable space of the ADU is what determines its size limit, while the garage is considered an accessory structure.

However, if you later decide to convert the garage into living space, it would then count toward the total ADU square footage and need to comply with local size restrictions. Additionally, attached garages must meet fire separation requirements and follow standard setback rules that may differ from those for the ADU itself.

ADU Garage Conversions

Garage conversions provide an efficient way to create an ADU without the cost of constructing a brand-new structure. Since the foundation, walls, and roof already exist, a conversion can reduce overall construction time and expenses. However, conversion projects can be more unpredictable. Any time you are working with an existing structure, you are opening up potential pre-existing issues that may need to be brought up to code.

For instance, existing garages may require reinforcements, particularly if they were not originally built to residential standards. Garages typically lack plumbing, insulation, and electrical systems suitable for living spaces. Upgrading these systems is necessary.

Choosing the Right Builder

Selecting the right contractor is crucial when building an above-garage ADU. Working with a knowledgeable designer and builder who has extensive experience with ADU projects ensures that your carriage house meets local zoning laws, structural requirements, and quality standards. Not all ADU builders specialize in above garage construction, so it’s essential to choose a contractor familiar with the unique challenges these projects present. Other important factors to consider include transparent pricing, clear project timelines, and a strong portfolio of completed ADUs. Checking client reviews and past projects can also provide insight into a builder’s reliability and craftsmanship. Read more about what to look for in a reliable ADU company.

At SnapADU, we specialize in designing and building ADUs with garages throughout San Diego County, making us a top choice for homeowners looking to add a carriage house to their property. With extensive experience in constructing this type of ADU, we understand the complexities involved and offer comprehensive services, including custom design, permitting, and ADU construction. Our expertise ensures that each project is completed smoothly, on time, and in compliance with all local regulations. Whether you’re building for rental income, multigenerational living, or additional workspace, SnapADU delivers high quality, well designed carriage houses that maximize your property’s potential.