A lot has changed since accessory dwelling units (ADUs) first began gaining popularity back in 2017, and cost seems to be one of the biggest changes. Searching online you’ll find a lot of conflicting information, with costs ranging from $30,000 to $400,000. A lot of this discrepancy comes from outdated information, especially following the pandemic.

Let’s set the record straight in 2024.

Thinking about adding an Accessory Dwelling Unit (ADU) to your property? Whether you’re dreaming of a cozy home for family, a home office retreat, or a rental unit to bring in some extra cash, understanding the costs involved is your first step to making that dream a reality.

Overview of ADU Cost in 2024

There are three main costs that make up the final total of an ADU project:

  1. Design
  2. Permitting
  3. Construction

Design Costs

Design costs include everything from initial consultations with architects or ADU designers to creating your full permit set that gets sent to your local planning department. This category can also cover consulting and engineering reports, and any other preparatory work necessary to get your ADU project off the ground.

Permitting Costs

Before you can start building, you’ll need to secure the necessary permits from your local government. Permitting costs can vary widely depending on your location and the specific requirements of your ADU project. These costs might include zoning fees, environmental impact assessments, and inspections.

Construction Costs

This is where the bulk of your budget will go. Construction costs cover everything from site preparation and foundation work to building materials, labor, and utilities. This category also includes finishing touches like flooring, fixtures, and landscaping.

Understanding these three main cost categories will give you a clearer picture of the financial commitment required for your ADU project.

Cost Breakdown by ADU Types in 2024

Now that we’ve covered the main cost categories, let’s dive deeper into the specifics. Not all ADUs are created equal, and the type of ADU you choose will significantly impact your overall expenses. Whether you’re considering a garage conversion, a basement ADU, or a standalone unit, each option comes with its own set of costs and considerations.

Before we dive in, we should mentioned that rather than using cost per square foot, we will be using starting costs. Cost per square foot can be unreliable as two identical projects can yield wildly different figures depending on a variety of factors. For this reason, we provide starting costs so that you can have a base number to build off of. Without further ado, let’s get into it!

Detached ADUs

Detached ADUs in 2024 will start at about $200,000. This includes all design fees, site preparation, and construction.

Detached units are the second most expensive type of ADU due to the need for a new foundation, additional utilities, and standalone structure. However, they offer the most privacy and flexibility for both the homeowner and potential tenants, making them an ideal choice for homeowners looking to make passive rental income.

The overall cost can vary depending on factors such as the size of the unit, the quality of materials chosen, and any additional features or customizations. For instance, high-end finishes, custom cabinetry, or advanced energy-efficient systems can push the total higher.

While the initial investment may seem steep, detached ADUs often offer a higher return on investment through rental income or increased property value. They are a great choice for those looking to maximize their property’s potential while providing a comfortable and independent living space.

Attached ADUs

Attached ADUs in 2024 will start at about $200,000, about the same as a detached ADUs. Many homeowners think that they’ll save money by attaching to the main house (one less wall to build!), but the savings are usually minimal.

Still, attached ADUs are extremely popular for homeowners looking to build an ADU for a family member that needs care as they’ll be just steps away.

Garage Conversion ADUs

Garage conversion ADUs in 2024 will start at about $140,000.

Conversion ADUs are by far the most cost-effective option for ADUs, but the cost will depend on the overall condition of the garage. If your garage is deemed too damaged, it may need to be torn down and rebuilt. Still, you can salvage some of the materials of the garage to use towards the ADU like this clever homeowner in San Diego did with her 600 sq ft ADU.

Above Garage ADU

Above garage ADUs in 2024 will start at about $300,000. Quite a price tag! But, this ADU type is popular amongst homeowners that want to keep their garage and backyard in tact. Plus, above garage ADUs offer the most privacy of all the ADU types.

Most garages are not built to hold a second floor, so some hefty reinforcement work needs to be done on the garage before the ADU construction can begin.

But remember, these are just starting costs. Depending on certain details of your lot, project needs, and timeline, your final cost will likely be higher.

Factors that increase ADU costs

From design choices to site conditions, several elements can significantly impact your budget. Knowing these factors ahead of time can help you plan more effectively and avoid unexpected expenses. Here are the most common factors we’ve come across.

Sloping on lot

Building on a sloped lot can present unique challenges and often requires additional engineering and construction work to ensure stability. This can include grading, retaining walls, and specialized foundations, all of which add to the overall cost.

If you have an area of your property that is more level than others, it might be best to place your ADU there to avoid this cost.

High-End Finishes

Opting for premium materials and finishes can significantly increase your ADU’s price. While these choices can enhance the aesthetic appeal and durability of your unit, they come at a higher cost compared to standard options.

That doesn’t mean you have to completely give up your vision. It’s all about finding the right balance between affordability and luxury and learning where you can splurge vs save.

Utility Connections

Every ADU is required to have water, sewage, and electricity so there’s no way around this cost. However, the placement of your ADU plays a huge part in the difficulty of installing the utilities. For example, the farther back you decide to place your ADU on your lot the more trenching will need to be done to connect your unit to the main sewage line.

Time of Year

Believe it or not, but the time of year also impacts the final cost of your project. Spring and summer are the busiest times for general contractors, so quotes for construction are going to be higher during this time. The earlier you can get on a general contractors books, the better.

Get in the books with Maxable

Understanding the costs associated with building an ADU in 2024 is crucial for effective planning and budgeting. By being aware of these potential expenses and planning accordingly, you can ensure a smoother construction process and avoid unexpected financial surprises.

Investing in an ADU is a significant decision, but with the right information and expert guidance, it can be a rewarding addition to your property.

If you’re ready to take the next step in your ADU journey, Maxable is here to help. Book a call with us today to get connected with top general contractors in your area. Our experts will guide you through the process and ensure you’re on the right track to make your ADU dream a reality.