Accessory Dwelling Unit Design/Build Services from Neil Kelly.

Make the most of your home by adding an ADU!

Every year, more Northwest homeowners are enhancing the value and livability of their properties by adding ADUs. Accessory dwelling units — also known as backyard cottages, in-law apartments or even granny flats — are separate residential living spaces built on the property of a single-family home. Whether you’re interested in having more room for guests, sharing your home with family or generating rental income, an ADU is a great way to leverage available space on your property.

While the term ADU typically brings to mind a backyard cottage behind the main home, there are several types of accessory dwelling unit to consider, depending upon existing property configuration and intended use:

  • New construction of freestanding or detached ADU
  • Conversion or expansion of an existing secondary structure, such as a garage, into an ADU
  • Conversion of a space within the main home, such as a basement or attic, into an ADU
  • Addition of an attached ADU to the main home

While building a small backyard cottage may seem relatively straightforward, local regulations can be complex, and careful planning and efficient design are essential to ensuring comfort and livability in a compact space. Our design/build experts have the knowledge and experience to help you navigate all of the requirements, options and possibilities, and build the ADU that’s just right for your property, your budget and your intended use.

Begin exploring the possibilities today by scheduling a complimentary design consultation.



If you’re considering an attached or converted ADU, or wanting to create a one-of-a-kind freestanding cottage, we can help. The expertise, craftsmanship and environmental awareness we bring to remodeling and custom homebuilding are a great fit for custom ADU development. Achieve the perfect balance between your dreams and your budget, your design ideas and functionality, technology and nature. All with uncompromising construction quality and unmatched service.





This tiny home ADU combines contemporary NW design with industrial elements, creating a light, spacious feel inside a small envelope.

With this particular unit bound for the short-term rental market, the Neil Kelly team — led by Design Consultant Chad Ruhoff — chose materials and finishes that would be long-lasting and easy to clean. The team also wanted the building to be energy efficient and solar powered.


Tips & FAQ

Add Value to Your Home With an ADU

Creating a custom Accessory Dwelling Unit (ADU) with Neil Kelly is an experience that blends innovation and craftsmanship. From the initial consultation to the final touches, our team works closely with you to design and build a unique ADU that exceeds expectations. If you have an ADU project in mind you can connect with one of our consultants in the following areas:

Portland, Oregon Eugene, Oregon
Bend, Oregon Seattle, Washington


ADU Tips & FAQ

Looking to create your own ADU but don’t know where to begin? Take a look at a few of our frequently asked questions about building an ADU space at your home.

What types of accessory dwelling units do you build?

Neil Kelly constructs a variety of ADUs, the most common include:

  • Attached to the main house
  • Detached, or a separate freestanding structure from the main house
  • Garage conversion
  • Basement conversion
  • Attic conversion
  • Home addition

What must my ADU include?

Depending on where you live, the requirements for an ADU include but are not limited to:

  • Sleeping, kitchen, and bathroom facilities
  • At least one operable window or exterior door approved for emergency escape and rescue openings
  • You must be able to open the window or door from the inside
  • Heating controls separate from the primary dwelling unit
  • Connection to water and sewer services

To ensure your ADU complies with your local laws and regulations talk to our team.

How much do accessory dwelling units cost?

It depends on the type of ADU you want to build, the type of property you have, the building regulations in your local area, and other factors.

The best way to find out specifics about cost is to speak with one of our design consultants.

Do accessory dwelling units have to be designed, or can you use off-the-shelf plans?

In general, ADUs designed to suit an existing property or structure are going to be more functional for residents and create more resale value for homeowners. However, some municipalities in Oregon are offering plans that are pre-approved to streamline the permitting process, and plan sets are available from various sources. Your Neil Kelly Design Consultant can help you choose a starting point that meets your project vision and goals.v

What are the legal requirements for building accessory dwelling units in my location?

In many states, a building permit is required to build a new structure or convert attics, garages, or other spaces into a  living space like an ADU.

Depending on your project, you may also need electrical, plumbing, or mechanical permits.

The best way to find out specifics about ADU construction in your area is to speak with one of our designers.