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ADU Garage Conversion Costs: Expert Insights by ADU Alliance

Navigate ADU Garage Conversion Costs with ADU Alliance

Are you looking for the cost of converting an ADU garage? Then you should read the next article. However, before we get into it, let’s start by pointing out that there isn’t a single standard for garages everywhere. They are all different sizes, ages, placements, architectural styles, and even the engineering and integrity of their structures.

  • A primary residence may have a garage that is adjacent to it, whereas other garages may be detached and placed at a significant distance from the primary residence. Each of these factors will influence the final cost of converting an ADU into a garage. Keeping all of this in mind, shall we get started?
ADU Garage Conversion Costs in orange county

At ADU Alliance, we understand that the decision to convert your garage into an Accessory Dwelling Unit (ADU) is a significant one. However, understanding the costs involved in an ADU garage conversion can be challenging. This guide aims to provide a detailed breakdown of the costs you can expect when undertaking an ADU garage conversion.

Key Takeaways

  • The cost of an ADU garage conversion varies based on factors such as size, age, location, architecture, and structural integrity of the garage.
  • Key cost components include plans and design, engineering, permits, and construction.
  • Plans and designs can range from $2,500 to $40,000, while engineering costs can vary from $350 to $4,000 or more.
  • The city determines permit costs, which can range from $1,500 to $5,000 or more.
  • Construction costs depend on the size of the garage, materials used, and whether separate utilities for the ADU are desired, ranging from $150 to $250 per square foot or more.
  • As an example, converting a 400-square-foot garage into an ADU could cost around $65,000 on the lower end and closer to $100,000 on average.
  • For an accurate cost estimate for your specific garage conversion, contact ADU Alliance at (714) 409-6123. We offer comprehensive services, including plans, engineering, design, permitting, construction, and project management.

Factors Influencing ADU Garage Conversion Costs

Not all garages are the same. They differ in size, age, location, architecture, and structural integrity. Some garages are attached to the main residence, while others are detached. All these factors will influence the overall cost of your ADU garage conversion.

ADU Garage Conversion Costs in orange county

Breakdown of ADU Garage Conversion Costs

The cost of converting a garage into an ADU involves several components:

Plans & Design

  • This involves drafting and completing plans for the conversion, which can be done by an architect, draftsman, or designer. The cost for this can range from as low as $2,500 to as high as $40,000.


  • If you’re making structural changes or adding windows and doors, you’ll need to factor in engineering costs. These can vary from $350 to $4,000 or more, depending on the extent of the structural work.


  • The cost of permits issued by your city can range from $1,500 to $5,000 or more.
ADU Garage Conversion Costs in california


  • The cost of construction will depend on factors such as the size of the garage, the materials used, and whether you want separate utilities for the ADU. Construction costs can range from $150 per square foot to $250 per square foot or more.

Additional costs may include utility fees and project management and coordination fees.

If you’re interested in exploring innovative design ideas for your ADU, the American Institute of Architects is a great resource.

An Example of ADU Garage Conversion Cost

Let’s consider a 400-square-foot garage. If you’re on the lower end of all cost categories, you might be able to convert the garage into an ADU for around $65,000. However, this is a best-case scenario and does not factor in new utilities for the ADU.

The average ADU garage conversion cost usually ends up somewhere in the middle of the range of these four categories, which is closer to $100,000. The cost can increase if you want extra features installed, such as patio doors or laundry facilities.

  • Please note that these are approximations based on current building costs and are intended for learning purposes only. The actual cost could be lower or higher, depending on your specific circumstances.

For more insights into construction costs and trends, check out the National Association of Home Builders.

ADU Garage Conversion Costs orange county

Getting an Accurate ADU Garage Conversion Cost

The best way to get an accurate cost for your specific garage conversion is to connect with an ADU company like ADU Alliance. We offer comprehensive services, including plans, engineering, design, permitting, construction, and project management. Our team will assess your property and provide you with an accurate ADU garage conversion cost specific to you and your garage.

Ready to transform your garage into a valuable living space? Don’t let the process overwhelm you. At ADU Alliance, we’re here to guide you every step of the way. Dial (949) 303-7676 now, and let’s start turning your ADU dreams into reality! Your future self will thank you.

Disclaimer: Please be aware that all of the numbers and estimates that are provided on this page are merely estimates based on the current building expenses in our region of Orange County, California, and are only meant for the sake of learning.

It is usually preferable to consult with an ADU builder in your region, have them see and analyze your property and project requirements, and then offer you an accurate estimate, which could be lower or higher than the samples that were presented. Consultation with an ADU builder in your area is always the best course of action.