Orange County Accessory Dwelling Unit Costs 

As a result of the new ADU legislation in California, more OC homeowners are taking advantage of possibilities to expand the amount of living space on their property. An accessory dwelling unit (ADU) is a secondary living space attached to or located near your primary residence.

ADU construction is a huge undertaking that is not cheap. Before beginning your project, here is what you need to know about accessory dwelling unit costs.

Here at GreatBuildz, a free service that connects homeowners in Orange County, Ventura & San Diego with reliable general contractors, we help people every day to better understand the accessory dwelling unit costs, scope, and details for their prospective projects – below is an overview of what costs to expect when building an ADU.

ADUs can be utilized as guest suites, accommodations for elderly relatives or live-in nannies, home offices, fitness facilities, and even studios for hobbies such as art and music.

An Orange County ADU can also be leased to long-term tenants. Depending on location, a small ADU can generate between $1,800 and $2,200 per month in rent, whereas a larger unit with two or more bedrooms can command between $2,500 and $3,300 per month.

What Are My ADU Options?

Depending on where you reside, the size of the job, who you hire, and the materials you select, you have a pretty wide range of how much your ADU will cost. 

If you are considering adding an ADU to your property, you have 3 main options:

  1. Converting your garage into an ADU
  2. Adding an ADU attached to your home (Either on top of a garage or attached laterally to the side/back of your home)
  3. Adding a detached ADU to your side/back lot

Related: Building an ADU Above Your Garage

Total cost to build an ADU in Orange County

The overall cost of a garage conversion might range between $90,000 and $130,000. Because you are constructing within an existing structure, garage conversions are often the most cost-effective choice.

A detached accessory dwelling unit with one level typically costs between $200,000 and $400,000. The main factors that dictate the cost of your project will be site conditions, the size of the structure, and of course, the finishes you choose inside and out.

Accessory dwelling unit prices for a detached unit are significantly greater than garage conversion costs because you are essentially constructing a new modest-sized home. It will require a new foundation and support structure, in addition to brand-new electrical, plumbing, and HVAC systems, along with everything else a home requires.

Orange County accessory dwelling unit costs

You should also budget for an architect or designer to develop your plans and submit them to your City’s Department of Building and Safety for plan check approval when calculating the cost of this project. Depending on the complexity of your project, you can anticipate paying between $8,000 and $15,000 for a full set of plans.

How much should I anticipate paying for an Orange County ADU?

Budget for a pricing range of $250 to $400 per square foot when planning your ADU costs. This range reflects the fact that some contractors charge greater rates than others and that material costs are rather unpredictable when supply chain problems occur.

To give you a better idea of what you can expect to pay, below is a link to an accessory dwelling unit cost calculator. This calculator requires you to enter the size of the ADU you’re planning to construct, your location, the current value of your home, the type of terrain you’ll be building on, and whether you’ll be adding solar panels.

Related: ADU Cost Calculator

How can I reduce the cost of my Orange County accessory dwelling unit?

Granny Flat ADU in Orange County

Early consultation with a knowledgeable ADU builder is one of the simplest methods to save money when constructing an accessory dwelling unit (ADU). He or she will be able to walk you through all of your options for features and materials, allowing you to create a plan that meets your goals, preferences, and budget.

Also, using all-electric equipment eliminates the need to run a gas line to the new unit. And you could plan the layout of the ADU so that the kitchen and bathroom share a wall, simplifying the plumbing and thereby reducing cost. Finally,  Instead of installing hardwood floors, you might opt for vinyl plank.

How do I pay for my Orange County ADU?

You don’t necessarily need to pay cash for your ADU…many homeowners prefer to finance their ADU projects with a home equity line of credit, a construction loan, or a home improvement loan.

To learn more about the various options when it comes to paying for an ADU, click the blue link above for the various financing options you have.

What do local ADU regulations require?

A multitude of rules and laws will limit where you can build, the size of your structure, and its appearance.

First, you can only construct an ADU in the backyard or side yard of your primary residence. As of mid-2022, you cannot construct in front of your property (but this may change!). In addition, there must be a minimum distance of four feet between the edge of the unit and the property line.

A detached ADU is limited to either 1,200 square feet or 50 percent of the size of the primary residence, whichever is smaller. A detached ADU cannot exceed 1,200 square feet in size. They may be either one or two stories tall, with a maximum height of 16 or 25 feet. More than fifty percent of the roof surface must have a minimum pitch of 2:12 degrees.

Cost to construct an Orange County ADU

ADU construction

The materials used are also important. The usage of laminates, single-piece composites, and interlocking metal sheets is prohibited. Roofing cannot be constructed using wood shingles. Windows must have a minimum of double-pane glass and be labeled for building usage.

The living room/bedroom must be at least 70 square feet in size. The overall area of the kitchen, hallways, and closet must be 70 square feet. In addition, the bathroom must be at least 30 square feet in size and have a toilet, sink, and shower or bathtub.

Local governments may have extra ADU regulations, so it is crucial to be informed of what is required in your city. If your ADU is not fully compliant, you may be required to amend or even demolish your project, which can significantly increase your expenses.

A professional ADU contractor will be well-versed in these and other requirements and will ensure compliance with them.

How do I prepare to obtain ADU contractor bids in Orange County?

ADU Financing

A contractor’s bid is an itemized estimate of the costs associated with completing your project. Without your input, it is unlikely that the quotes you receive from several contractors will contain the same items. When soliciting bids, it is therefore essential to include a scope checklist.

A scope checklist contains all the items you anticipate requiring for the project. This may involve foundation, frame, doors, and windows, installation of new sewer, water, and gas lines, kitchen and bathroom construction and appliances, and site elements such as landscaping, fencing, hardscape, etc.

To ensure that nothing is overlooked, we have designed a scope checklist template. Remember, the more precise you want your bids to be, the more specific your scope checklist needs to be.

Checklist of Accessory Dwelling Unit Costs

Accessory Dwelling Unit costs checklist

Typical Scope Checklist For Building An ADU – Contact Us For an Editable Version!

Email or Call 818.317.3567

We recommend soliciting at least three estimates from separate contractors. This will allow you to choose which contractor offers the best price for the project, and it will also give you some perspective on what it would be like to work with different types of contractors. Choosing the cheapest contractor is not always the right move. When a bid comes in significantly lower than the others, you have to ask yourself whether that contractor is missing something important in their bid. 

Remember, this is a team you’ll be working with for 6+ months, so it’s crucial that you’re working with a trustworthy, reliable contractor.

And getting in touch with great Orange County ADU contractors need not be difficult. GreatBuildz has established an extensive network of licensed general contractors. Call us and tell us about your ADU project, and we’ll put you in touch with three pre-screened professionals in your area who are accepting new clients.

GreatBuildz is a free service that connects homeowners in Los Angeles, Orange County, Ventura & San Diego with reliable, thoroughly screened general contractors and provides project support from start to finish.

Submit your project to be connected with several fully vetted, trustworthy contractors who are experienced with accessory dwelling unit costs and projects. For more info, visit or call 818.317.3567 today.

  • Dana Point ADU Guidelines

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  • La Palma ADU Guidelines

  • Laguna Beach ADU Guidelines

  • Laguna Hills ADU Guidelines

  • Laguna Niguel ADU Guidelines—Accessory-Residental-Unit-Permit 

  • Lake Forest ADU Guidelines 

  • Los Alamitos ADU Guidelines 

  • Mission Viejo ADU Guidelines

  • Newport Beach ADU Guidelines

  • Orange ADU Guidelines 

  • Placentia ADU Guidelines 

  • Rancho Santa Margarita ADU Guidelines 

  • San Clemente ADU Guidelines

  • San Juan Capistrano ADU Guidelines

  • Santa Ana ADU Guidelines

  • Seal Beach ADU Guidelines 

  • Stanton ADU Guidelines 

  • Tustin ADU Guidelines

  • Villa Park ADU Guidelines

  • Westminster ADU Guidelines

  • Yorba Linda ADU Guidelines 

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