Building Official Determination 19-08: Dryer Vent Screening

Building Code Guides (BCGs) and Building Official Determinations (BODs) provide answers about the application of building codes and outline optional alternates. BODs are typically smaller in scope and address simpler questions. Code Guides provide a comprehensive alternative to a complicated set of code requirements.

BOD 19-08: Dryer Vent Screening  

QUESTION: The Oregon Mechanical Specialty Code (OMSC) Section 504 states that screens shall not be allowed at the duct termination of clothes dryer exhaust vents. Is there an alternative to a fully clear opening at the duct termination?

RESPONSE:Portland Permitting & Development (PP&D) has determined that louvers shall be allowed at the exterior duct termination of a clothes dryer exhaust vent under the following conditions:

1. Placement. Louvers shall be in the same plane as the exterior face of the building. The space between the end of the vent(s) and the louver at the exterior wall shall be minimum 6” and maximum 18”.
2. Configuration. Louvers shall have minimum 1.5-inch spacing. Louver fins shall not be more than 45 degrees from horizontal. 
3. Backdraft Damper. Duct terminations shall be equipped with a backdraft damper.
4. Vent Separation. Where there are multiple vents, (of any type), adjacent to one another, the vents shall be separated from each other from the point of the end of the vents to the louver at the exterior wall. This separation shall be of the same material and same gauge as the vents.
5. Cleanout. The duct termination shall be accessible for cleaning. Plans shall identify where cleanout access is located and how the cleanout will function.
6. Perforated Screening. Other types of screening, such as perforated screening, shall not be allowed.
7. Other Code Requirements. All other requirements of the OMSC shall be met.

It is recommended that the exterior clothes dryer vents shall be cleaned at least once annually.

Other alternatives that do not meet the conditions of this code guide will be reviewed and considered on a case-by-case basis through the administrative appeals process.

HISTORY: Implemented March 22, 2019. Revised May 30, 2024.

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