Frequently Asked Questions about ADU Design and Construction

We understand that there are many considerations during the process of planning an Accessory Dwelling Unit. Below are some frequently asked questions about designing and building an ADU.

Question 1: How much does it cost to build an ADU?

This is difficult to answer without the specifics of a project but we can at least give you some insight into typical costs of a new construction, detached ADU in Portland, Oregon.

  • Construction $250,000 to $400,000+

  • Design $18,000 to $30,000+

  • Permits $7,000 to $23,000+

    The range in permit cost is largely dependent on two things:

    • Is the ADU being built initially as a short term rental?

    • Do the additional plumbing fixtures for the ADU necessitate a new water supply branch installation by Portland Water?

  • TOTAL PROJECT COST - $275,000 to $453,000+

    This is a rough breakdown and the specifics of each site, the building conditions, the final design, the availability of contractors and materials, among many other factors can affect the final costs of the project. Our design fees vary by project based on site, complexity, historic design review, permitting requirements, etc. We usually work for a lump-sum fee to allow our clients to have cost certainty while breaking the fee into monthly payments based on work performed.

 

Question 2: How long does it take to design and build an Accessory Dwelling Unit?

  • 2 to 3 months to design

  • 2 to 3 months for permit approval

  • 6 to 9 months to build depending on weather & contractor

  • TOTAL DURATION - 10 to15 Months

 

Question 3: What services do architects provide?

Our role as the architect is to see the big picture when it comes to your project, and following that concept through to the details, resulting in a thoughtful and beautiful project. We will help you explore what appeals to you aesthetically and what you require functionally. We work to coordinate the team of design, engineering and construction professionals towards this common goal. In short, we follow your project from early concept design through completed construction working with your best interests at heart.

 

Question 4: What's my role in the design process?

We will depend on you to communicate your design preferences, functional requirements, and budget. Your input to questions and our design deliverables during the process will help keep the project on track.

For more information about our experience and process as architect on ADU design, please visit this page.