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Phone: 503-823-7300


1900 SW 4th Ave, Portland, OR 97201

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New Code Guide for Additional Dwelling Units within Townhouses


August 19, 2019

New Code Guide for Additional Dwelling Units within Townhouses
Effective September 16, 2019

BDS has approved a new code guide that will allow additional dwelling units, specifically Accessory Dwelling Units (ADUs), to be constructed within Townhouses if certain requirements are met, and will provide clear requirements for spaces used in common by multiple Townhouses. This code guide will be effective on Monday September 16, 2019.

The Oregon Residential Specialty Code (ORSC) does not explicitly recognize ADUs. Instead, primary dwellings with attached or enclosed ADUs are treated as two-family dwellings under the building code, with specific modifications as expressed in BDS’s ADU Program Guide. However, the ORSC definition of townhouse specifies that a townhouse is a single dwelling. This code guide provides for an alternate definition and equivalent standards for two-family townhouses (i.e. a townhouse with an ADU). The code guide thus provides an avenue for a townhouse with an ADU to be designed to the ORSC instead of requiring full compliance with standards for apartment buildings in the Oregon Structural Specialty Code (OSSC).

Highlights of the new code guide are:

  • The guide requires additional fire and life safety measures to provide equivalency for building two-family townhouses. For example, a 2-hour fire separation between the ADU and the Townhouse is not required; instead, a residential sprinkler system (NFPA 13D) is required.
  • A common trash room or bike storage room serving multiple Townhouses will be allowed provided the common space is separated from each of the Townhouses by 2-hour fire resistance rated construction.

The code guide can be viewed here.

Contact: Terry Whitehill, 503-823-7639.


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