How Much Does it Cost to Hire an Architect to Design an ADU?

How Much Does it Cost to Hire an Architect to Design an ADU?

Maybe you have considered adding an ADU (accessory dwelling unit) to your home. Like most things in life, there are several different ways to achieve an end goal. If you do not have a background in construction or a natural knack for design, deciding to hire an architect to design your ADU for you is an excellent option.

A good rule of thumb is to budget between 8% and 15% of the total project cost. However, the cost to hire an architect can vary greatly based on several factors:

  • Local economy
  • Architect’s experience level
  • Size of desired ADU
  • Percentage of total project cost vs. hourly rate
  • Complexity of project

Understanding how much the design portion of your project will cost is critical and will help you determine your overall budget for your ADU. The last thing you want to do is start a project and end up with a much larger bill than you expected. This article is here to help you understand the cost of hiring an architect for your ADU!

How Do You Estimate How Much An Architect Will Cost?

Most architects will provide a free estimate to you. Typically during an estimate, the architect will meet you at your home, evaluate the overall complexity of the project and determine a rough estimate of how much the project will cost you.

The cost to hire an architect can vary greatly depending on various factors including the local economy, scale, and complexity of the project, and the experience and reputation of the architect. Architects may charge a percentage of the overall cost of the project, charge by the hour, or also a combination of the two.

To provide a more accurate estimate of how much an architect will charge to design an ADU, we have to understand two things. We have to know the size of the desired ADU and the cost per square foot to build.

How Does Size Affect the Cost of Hiring an Architect?

An ADU is between 300 and 1,200 square feet on average. Again, the price per square foot can range based on the local economy.

However, on average, you can budget for $200-$250 per square foot and up for a well designed and quality ADU. So an ADU that is 700 square feet may start at $140,000-$175,000 to build which would result in an architect fee starting around $11,200-$14,000 based on the assumptions above. There are also some architects that charge by the hour.

Of course, there are other factors as well that affect the overall cost and those include fit and finish of your ADU. An architect can play a significant role in helping you pick those finishes and ensuring the flow of the ADU fits the overall look and feel of your existing home. This is a key reason why some people choose to hire an architect.

Is the Cost Worth It?

An architect can help bring your dream ADU to life. Using state-of-the-art programs to drawings on a sketch pad, an architect will help you to conceptualize your plans.

However, they also handle the million other details that go into building an ADU that most people would not think is necessary. Architects can also help to keep general contractors on target to meet deadlines and complete the job on time.

Legal Help

Not only does working with an architect help you dream up the best ADU you could imagine and ensure the work will be done correctly, but working with an architect can also help with all the additional leg work required to permit the ADU.

Zoning requirements must be met. Every county has different requirements and limitations for what one can build, this may include size, appearance, your total FAR (floor area ratio), setbacks, and more.

Researching the different laws for permitting can be exhausting, and interpreting the information can be overwhelming. An architect makes this part of the process much easier. They know the laws and will ensure you are building your ADU legally and complying with all the proper permits.

Most general contractors are not informed on this and will often ask you, the homeowner, to research to know what is allowed and what is not.

Management and Advice

Architects also routinely work with the general contractors to ensure builders are executing plans. Architects help manage the project from start to finish and are a touchpoint for the contractors to ask questions as opposed to inundating the homeowner with questions you may not be able to answer.

Architects also can help you to determine what is structurally possible within your space. You may think that you have a great plan for the ADU layout but without knowing the structural capabilities of a small home, your plans may not work.

Architects generally work with engineers who can tell you exactly what is possible to build and what is not. This can prevent you from wasting valuable time and money, which certainly makes up for the cost of the architect.

Can You Save Money By Designing Your ADU Yourself?

Maybe the cost of the design portion of your budget to build an ADU has you wondering if you can build an ADU without the need for an architect. Many people often choose to build ADUs without the help of an architect.

Depending on your skill level and ability to conceptualize spaces, you may be able to work directly with a construction company to design your ADU, particularly if you are converting a space like a detached or attached garage that already has a foundation and some structure laid.

Some construction companies have in-house designers that you may work with to design your ADU. Sometimes this comes at an additional fee but other times, general contractors will include the design portion in their jobs if the scope is not very complex.

If you are closely watching your budget for your new ADU build, then avoiding the cost of hiring an architect may be your desired option. Deciding not to hire an architect can free up more money to be spent elsewhere such as on upgrading finishes.

What Other Budget Items Must Come Before You Hire an Architect?

In deciding whether you have room in your budget for an architect, you need to make sure you have fully accounted for all the other required aspects of the budget. Anyone who has decided to make additions or improvements to their home soon realizes that the costs can add up quickly, so budgeting for all steps in the process is important.

Additional areas to research include the cost of permits, the average price per square foot construction cost is in your local area, and what level of finish is desired. Calculate these cost estimates before adding an architect to the budget.

Of course, when building any construction, including an ADU, it is important to budget for the inevitable. Whether it be unexpected plumbing or electric issues, it is always safe to retain a contingency budget of around 5-10% of construction costs to cover these unexpected issues.


In summary, the cost to hire an architect to design your ADU is not a requirement but if your budget allows for it, it can be a great asset. After all, you are spending good money to build the ADU, you want it to be the best that money can buy.

It is possible to build an ADU without hiring an architect or to work directly with a general contractor. However, if your ADU is a more complex project, it may be beneficial to hire an architect to help you create a space to maximize functionality, visual appeal, and ensure you are making a secure investment of your money and time.

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