How Much Does It Cost to Build an ADU (Accessory Dwelling Unit)

When you step into the magical world of Accessory Dwelling Units (ADUs), you’re met with an exhilarating whirlwind of possibilities. You might envisage a rustic, cozy retreat tucked into the backyard of your main house, or perhaps a sleek, modern loft perched above your garage. But amidst the imaginative daydreams, a rather pragmatic question nudges at your thoughts: “How much does it cost to build an accessory dwelling unit?”

The truth, dear reader, is that the answer to this question is as unique as your ADU dreams themselves. It can be a symphony of various factors playing together, each instrument adding a unique note to the ADU construction costs.

How Much is a Prefab ADU

Prefab ADUs are the harmonious meeting of convenience and cost-effectiveness, a pre-packaged solution to the construction puzzle. The typical prefabricated ADU cost varies, largely hinging on square foot requirements and design preferences. A basic prefab ADU could start at around $100,000, but as the melody of design, finishes, and size grows richer, the actual cost to build can soar to around $150,000 or more – read more about here –

It’s worth noting that prefabricated ADUs offer a fixed cost advantage – you know the tune before you start the dance.

Garage Conversion 

An existing structure like a garage, waiting for the magic touch to transform it into a thriving living space, is often music to a property owner’s ears. Garage conversions present an enticing proposition when contemplating an ADU project. Depending on the complexity of the job, garage conversions can range from $50,000 to $150,000. 

The total cost of such a project would include many factors such as the state of the existing structure, design costs, square footage, and permit fees.

Building ADU from Scratch

The melody of constructing an ADU from the ground up – a detached ADU, or an attached ADU – can be a beautiful but complex composition. The cost per square foot here can range from $200 to $600, contributing to a total project cost of around $100,000 to $300,000. The variable costs in this scenario include site and foundation preparation, design, permits, and the actual ADU building, making it more of an improvised jazz performance than a scripted classical recital.

  • ADU Blueprints

How to draw ADU blueprints? That’s a question many homeowners ponder, as it can greatly influence the construction costs. Professional ADU designs can vary depending on many factors, including complexity, local regulations, and the design professionals’ rates. The cost can range from a few thousand dollars to $20,000 or more. However, it’s a critical step in ensuring a stable foundation for your future attached or detached ADU.

  • Additional Costs

But dear reader, our symphony is not yet complete without acknowledging the extra costs that may subtly creep into your ADU project, apart from fixed costs. A glossy hardwood floor and more expensive HVAC systems here, an artisanal light fixtures and crown molding there, and suddenly, your final cost per square foot is singing a different tune. 

Overall, your total cost might greatly depend on things like ADU design, property taxes, a construction loan, or a home equity line, depending on your financial arrangements.

Is Building an ADU a Good Investment?

Despite the significant ADU cost per square foot, the rewards can be harmonious. The additional space can serve as affordable housing for aging parents, or provide rental income. Moreover, the boost in property value can make the ADU an awesome investment, potentially offering future value when you decide to sell your property. And let’s not forget about the possibility to rent out the accessory dwelling unit (ADU) after the site work that can generate additional income and, eventually, compensate ADUs cost.

Cutting costs on building an ADU

Yes, overall it costs less to build an ADU than a regular house, but here you can also reduce the price a bit. First, choose the right ADU type. Remember that attached ADUs cost less, so maybe choosing another type is a better decision. Second, materials and the process. Stick-built homes in combination with concrete slab for the foundation can significantly decrease the total cost.

Final Thoughts on the Accessory Dwelling Unit’s Cost

So, as we wrap up our review on ADU costs, it’s clear that the tune varies with every project. Just as every ADU is a unique blend of vision, function, and creativity, so too is the cost to bring it to life. 

And while the costs may be significant, the harmony of additional space, rental income, and increased property value can create a melody that’s worth every note.

Frequently Asked Questions — FAQ

How do I determine if an ADU is registered?

Determining if an ADU is registered generally involves contacting your local municipality or county office, which will have a record of permits and registrations. Don’t forget about the ADU permit cost that you will have to pay.

Is there a cheaper alternative to building an ADU?

A garage conversion or basement ADUs can often be more cost-effective than building an ADU from scratch. The cheapest way to build an ADU could be a tiny house, which is mobile, has better resale value, and often costs less to construct.

Does the size of an ADU affect the cost?

Yes, the size, or footage, of an accessory dwelling unit significantly affects the construction costs of the entire structure. Larger ADUs typically have higher costs due to increased material and labor requirements.

How can I finance the construction of an ADU?

Many property owners use their savings, while others might borrow money, such as through a home equity line or a construction loan.

Do ADUs increase property taxes?

Yes, building an ADU can increase your property’s assessed value, which may lead to higher taxes.

How long does it take to build an ADU?

The building process greatly depends on the complexity of the project and the permitting process. However, it can range from a few months to over a year.