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Accessory Dwelling Units:

From its inception, Tweto Architecture has maintained a strong focus on Accessory Dwelling Units (ADU's) and developed an expertise through the design of a dozen-plus ADU’s, including detached, attached, basement conversions, and garage conversions. 

For the unfamiliar, ADU’s are a legal path to create an additional dwelling unit on most properties in Portland, Vancouver, Bend, and surrounding areas. Rules vary by jurisdiction, but most place limits on size (at around 800 SF), lot location, and appearance; and allow the ADU to share utility connections with the existing home. In most cases an ADU can be considered an independent home or apartment, complete with a kitchen, bathroom, living space, and one or more bedrooms. 

Building an attached or detached ADU can be an attractive way to add flexible living space to a home or property. They can be used for multi-generational living, rental properties, short-term rental (AirBnB, etc), home-offices, art studios, guest houses, pool houses, and many other creative uses which can change over time. Their small size, the lack of property costs, potential development fee waivers, and shared utilities all help to make ADU’s a relatively affordable way to create essential housing in otherwise difficult to develop urban areas. 

Currently, in Portland, Accessory Dwelling Units are allowed in all residential zones, and in most cases, more than one ADU can be added to a property. Recent changes in regulations now allow the demolition of accessory structures (including garages) and, with limitations, the creation of new ADU's within historic districts (including Irvington Historic District) without a historic review. 

Recent zoning code changes now allow even further flexibility in housing options for most properties in Portland and surrounding areas. In addition to allowances for ADU’s, zoning codes now allow for splitting homes into duplexes, creating detached duplexes, and new triplex, duplexes, and fourplexes.

Contact Tweto Architecture to learn more about the best options for your property and your project goals. 


Asmund Tweto 


Portland, Oregon

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