Appeal 33634

2023 ORSC R302.1; OAR 918-020-0390; and ORSC/3/#5

R302.1 Exterior walls. Construction projections, openings and penetration of exterior walls of dwellings and accessory structures shall comply with R302.1. Where multiple detached dwellings are located on a single lot, each detached dwelling shall comply independently with Table R302.1. Considering the ADU and house are provided with fire separations greater than or equal to 2 feet, but less than 3 feet, the R302.1 requirements include:

• Exterior walls 1-hour fire-resistance rated;
• Projections 1-hour fire-resistance rated on the underside;
• Openings not allowed;
• Penetrations comply with Section R302.4.

OAR 918-020-0390 –

(1) A municipality may grant approval for conversion to no more than four dwelling units through alternate methods, modifications, and waivers to:
(a) means of egress requirements;
(b) smoke/carbon monoxide alarms;
(c) fire separation, fire resistance ratings, dwelling unit penetrations and compartmentalization; and (d) automatic fire sprinkler systems.

(2) A building official may consider whether an automatic sprinkler system is technically feasible and consider alternate methods and materials, provided that adequate safeguards exist to address the items listed in section (1) and other appropriate measures are in place to ensure public safety, fire and smoke control, and safe egress.

(3) A building official may accept an alternate method, modification, or waiver of other code items pertaining to the conversion of existing single-family dwellings into no more than four dwelling units; a building official may not approve a condition that would create an imminent threat to public health and safety.

(4) Applicable standards for the conversion of a single-family dwelling into two dwelling units follows the construction standards of the ORSC, and a conversion into three or four dwelling units follows the construction standards of the OSSC.

Allow an existing ADU on the second floor of an existing garage to be used for family members with the addition of a kitchen in the existing unit. The concern is the wall rating due to a total separation distance of 5’-0”.

The existing single-family residence and detached garage with guest room were built and permitted in 2013. The garage and guest room above the garage were permitted by Permit # 2011-203006-000-00-RS. The accessory structure is a legally permitted habitable unit. The proposal adds domestic cooking and a sink to the existing garage which already included a permitted guest room with full bathroom. The garage/ADU is located within 5 feet of the primary dwelling.

The proposed design is to provide 1 hour rated walls in the ADU as rated from the interior side by having at least 5/8” Type X gypsum board. In the ADU, this will be applied over the existing 1/2” gypsum board along the wall facing the house. The eaves which project into the fire separation distance are closed on the bottom side of the eaves, providing protection from migration of fire between house and ADU. The man door facing the garage is to be replaced with a 20-min. rated door with smoke seals. The existing window over the man door is proposed to remain as-is. The primary residence is proposed to remain as-is.

City of Portland Permitting & Development has provided ORSC/3/#5 to allow alternative standards for ADUs subject to the requirements of the ORSC. As confirmed with the City plan reviewer, the requirements of R302.1 must be addressed based on the location of the imaginary property line between the primary residential building and detached ADU. ORSC R302.1 Exception 2 for “… individual dwelling units and their accessory structures,” does not apply to habitable dwellings. The primary residence and the ADU are existing, and it is not possible for both structures to be greater than 3 feet from the imaginary lot line.

To address the limited availability of affordable housing, the State published ADU guidance within Oregon Senate Bill 1051, updated to include HB 2001 (2019), urging local officials to make it easier to build ADUs when that reduces the pressure on affordable housing in the state. SB 1051 was supported by OAR 918-020-0390, adopted in 2018 and amended in 2021, for the purpose of an alternative approval process for single-family dwelling conversions into 2 to 4 dwelling units. This rule authorizes the building official to waive fire separation requirements when it does not pose “or create an imminent threat to public health and safety”.

The intent of adding a proposed kitchen and sink to the permitted garage with guest room above is the same as originally permitted, to provide space for extended family to live. The proposed change creates very little threat to public health and safety. The existing ADU faces the primary residence and not the public or any other adjacent dwelling.

The proposed design will provide additional protection measures to what was permitted as a guest room. The protection measures are as follows:

• Add one layer of 5/8” Type X gypsum board (GWB) to the interior of the existing wall in the upstairs dwelling unit. The garage already has 5/8” Type X gypsum board on the interior. Provides 1-hour rated wall for protection from one-side.
• The siding of the house and the garage/ADU is cementitious siding, providing protection from fire migration.
• The existing non-rated eaves are proposed is to remain as-is, with soffit board enclosing the eaves.
• The personnel door into the garage is proposed to be 20-min. rated with smoke seals.
• The existing double-hung window above the personnel door is proposed to remain as-is, with required insulation.
• The existing penetrations for the electrical panel will be fire caulked in compliance with R302.4.
• Smoke detection in the garage will be connected with the ADU smoke alarms.

Providing an existing building to have rated walls, eaves and removing a window is infeasible. Improving the existing fire separation to provide the required 1-hour fire-resistance rating and 20-minute opening protection for the existing door will minimize the risk of fire exposure from the primary dwelling. As described in the Proposed Design section, the ADU kitchenette improvements meet the intent of SB 1051, OAR 918-020-0390, in improving an existing garage/guest room, providing an affordable, habitable accessory dwelling unit.