Key Steps to Building an Accessory Dwelling Unit (ADU) in Lake Oswego

Accessory dwelling units can increase property value, generate income, and enhance your property. Learn the basics about building an ADU in Lake Oswego with Refresh.

Accessory dwelling unit

What is an Accessory Dwelling Unit (ADU)?

An Accessory Dwelling Unit, or ADU, is exactly what it sounds like – a smaller, accessory home to a main property where someone can comfortably live, commonly referred to as a granny flat, in-law suite, or studio apartment. ADUs can be built as a home extension, a garage, basement, or attic conversion, or as a completely detached structure. 

Lake Oswego ADU Requirements and Regulations

  • Self-contained, built on a foundation
  • Allow enough room for one off-street parking space
  • Permanent utility connections (water, gas, electricity, etc.)
  • Size must be 800 ft2 or less
  • One ADU per property
Blue panelled home

Getting started: steps to build an ADU in Lake Oswego, Portland

  1. Find the right professionals

ADUs have their own rules and regulations that differ from a typical renovation, so it’s helpful to get professional guidance from the get go. Start by arranging consultations with different teams and ADU builders in Lake Oswego – recommendations are ideal. When you find someone you want to work with that aligns with your vision, goals, and budget, they can help you review local regulations. 

  1. Design your ADU

Whether you want to convert some of your existing space or build something new entirely, a detailed design is essential. And since ADUs require permanent utilities, it’s smart to engage a professional to design the structure who also has connections to qualified plumbers and electricians to bring the plans to life when it’s time. Detailed plans help the permitting process run more smoothly, too. 

  1. Pre-application conference (if required)

Pre-application conferences are required if you’re adding livable square footage to your lot; for example, an addition or detached dwelling. If you’re converting existing space within the primary home like a basement, garage, or attic, you can skip this step. 

  1. Get building!

If you’ve been diligent in the preliminary steps before building your ADU, the execution should go off without a hitch! When it’s all done, make sure you have all the appropriate documentation and paperwork in order, like a certificate of occupancy, land use compliance, or a new property tax assessment. 

Mini grey house with timber accents

Cost-effective approaches to building an ADU

Building an ADU can cost anywhere from $60,000* to over $200,000* depending on which route you take. Without the need for a new foundation or utilities, conversions are no doubt less expensive to execute if you have the space to spare. Prefab models, as opposed to custom designs, are another great option to save money.

ADUs are an investment; if you’re building it to house friends and family, you probably won’t see much of a financial return. However, turning your ADU into an income-generating rental unit helps the project become cost-effective after the fact. In fact, overtime, you’ll likely end up with a decent profit, especially if you end up selling your home as ADUs can potentially increase your property value by up to 30%.

Interior of small unit, bunk beds

Build an accessory dwelling unit with help from the professionals at Refresh

At Refresh, we’re more than contractors. Beyond the typical scope of project management, our Remodeling Consultants will guide you through the entire process from the very first meeting through to final project completion, helping you define the big picture as well as small details. To arrange your free consultation, simply get in touch with the Lake Oswego team.  

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