Building an ADU Above a Garage in Orange County

ADUs (Accessory Dwelling Units or Additional Dwelling Units) are now allowed to be constructed in Orange County and the rest of Southern California, as the state has loosened limitations on their construction. On just about any residential lot, you now have the option of building a secondary dwelling unit on your property.

Here at GreatBuildz, a free service that connects homeowners in Orange County, Ventura and San Diego with reliable ADU contractors, we speak to homeowners every day about planning their desired ADU project and budgeting for ADU construction costs – here are some ideas & tips to get you started.

An ADU is a second dwelling unit on the property. Building an ADU above a garage can be a great way to add room while leaving the garage for parking and storing automobiles.

Before you meet with builders, there are a few things you should know about installing an ADU above a garage.

Advantages of an ADU Over the Garage

ADUs are extremely popular because of their flexibility with regard to the functionality of the space. One of the biggest advantages of an ADU is its investment value.

There are two methods to profit from an ADU:

1. Rental Property to Generate Passive Income

You can create an ADU with an entrance, kitchen, bathroom, and bedroom, then rent the ADU to either short-term or long-term tenants.

2. Enhanced Property Value

Forbes reports that more homeowners are willing to pay for properties with accessory dwelling units (ADUs) because they recognize the benefits of using them for accommodation or investment purposes.

In general, constructing an accessory dwelling unit (ADU) on top of the garage may incur an increase in cost, but the return on investment (ROI) should make this expenditure worthwhile.

Cost Estimate for Constructing an ADU Over a Garage

According to Kol Peterson of, the typical cost to construct an ADU above a garage is approximately $200,000.

This estimate comes from homeowners in Orange County and Southern California who constructed an ADU recently. The cost of building the same structure might vary significantly based on the contractor and the current labor and material costs in a specific region.

As with any construction project, the quality and experience of the builders have a significant impact on costs.

Here’s the (Second) Story on Building an ADU Above a Garage

ADU above a garage Orange County

Garages’ structural foundations differ. Therefore, the costs of constructing an ADU on top of a garage vary. Some structures demand more labor or materials, and the complexity and quantity of work required vary by garage.

These factors could cause the project to cost more than anticipated:

  • Refinishing the entire exterior of the building.
  • The attached garage must be aligned with the upper level.
  • It is more expensive to install utilities.
  • The construction of new steps and a roof.
  • Frequently, older garages need more expense.
  • Reinforcing aging foundations to support the second floor

The age of the property has a considerable impact on the final cost. In the future, if you rent out the unit or sell your home, the return on investment (ROI) may be worthwhile.

Consider a basic layout for your second-story ADU above a garage to reduce building expenses. If you build your ADU exactly on top of the four corners of your existing garage, you will likely save money on framing, structural parts, and other costs. If your locality permits it, if you design for an exterior staircase rather than an interior staircase, you will save money because you won’t need to build inside space to the first/garage level floor.

Can I Rent Out My ADU?

Yes! One of the wonderful things about ADUs is that you can legally rent them out separately from your main residence.

There are a few rules that must be followed when renting out an ADU, but in general, it functions similarly to a standard rental unit. You must determine the lease terms and the monthly rent. Here you can learn more about the ADU renting legislation in Orange County.

What To Do With an Accessory Dwelling Unit Over a Garage

Build an ADU over a garage Orange County

Photo Credit: Bau10 & Paul Vu

Increasing your living area is another reason to consider constructing an ADU. Here are some applications of an ADU above a garage:

1. A Room for Seniors and Guests

The construction of an accessory dwelling unit (ADU) for grandparents or other senior relatives enables the family to care for them closer to home while also allowing them to live independently. A secondary dwelling unit can also serve as a guest room during the holidays.

2. The Ultimate Home Office or Fitness Area

Many individuals work from home, and an ADU can serve as an ideal home office. Away from the commotion of the main house, this is an ideal location for a study room or exercise area.

3. A Space for Adult-Children

In light of rising rental costs, it may be prudent to add an ADU for adult children. They can remain in the additional room while maintaining a high level of freedom.

Ideas & Advice Regarding an ADU Over My Garage

Now that you are aware of the advantages of creating a second-story ADU, here are some considerations to bear in mind:

1. Increase the amount of natural light by installing large windows and layered lighting

ADU above a garage, second story ADU Los Angeles

Second Story ADU

Natural light makes a small room feel larger and improves one’s mood. Glass panels and skylights are both wonderful options for doing this, and high clerestory windows bring sunshine in while preserving privacy, which is ideal for bedrooms and baths.

Additionally, layered lighting can assist create a bright and airy area. Consider all the light sources you could incorporate in addition to natural light. Pendant fixtures can be added to areas that require more illumination, such as the dining room or bedroom. recessed can lighting offers a beautiful design that illuminates huge areas.

2. Select Colors That Make the Area Appear Larger

Because it complements nearly every color on the color wheel and works well with the majority of color schemes, white is frequently used to paint ADUs with a second floor. Considering you’re likely to get more sunlight in an ADU above a garage, you should know that white reflects light, making the room appear brighter and larger. However, other brighter color schemes will also make the space appear larger.

3. Optimize Storage in order to free up Living Space

Whenever possible, incorporate built-in shelving and cupboards into your accessory home design. The use of stowable and convertible furniture, such as ottomans with storage and foldable beds, will also assist conserve room.

How to Construct an ADU Over Your Garage

Four phases are outlined below for constructing a second-story ADU.

1. Develop ADU plans

adu above your garage planning

Employ a qualified architect. An architect will assist you in determining your needs and collaborate with you to design your second-story ADU.

2. Obtain Loan Approval

After completing your ADU plans, submit an application with your bank or other financial institution for pre-approved financing.

Related: ADU Financing Guide

3. Obtain approval for the design from your Building Department

Apply to the building department for approval of your plans. If your blueprint complies with the rules, it will be accepted. After that, you can begin the application process for a building permit. Beware that building an ADU above a garage is a significant project, so it may take some time for the city/county to complete their plan check review process.

4. Identify a dependable ADU Contractor

You will need to consult with your contractor regarding the ADU project’s duration and required progress payments. Six to nine months are required for the processing of the project application, loan, and construction. Here are some suggestions for locating an ADU contractor.

When it comes to adding an ADU above a garage in Orange County, you shouldn’t have to go it alone – GreatBuildz can help simplify your renovation experience.



GreatBuildz is a free service that connects homeowners in Orange County, Ventura and San Diego with reliable, thoroughly screened general contractors and provides project support from start to finish. Call now (818.317.3567) to chat with a real person about your next project or visit our website for more information:

Hi, we're Paul and Jon - Co-Founders of GreatBuildz. We believe everyone deserves to find a great contractor, have a stress-free renovation, and enjoy their beautiful new space. There are so many contractors out there and it's often hard to tell the good from the bad... until it's too late. We started our company to help simplify your contractor search and help you have a stress-free renovation experience. We're always available to help, no matter where you are in the process. Click here to learn more about our story.

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