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.
BCG 24-11: Transient Use
QUESTION 1: How is transient use, or short-term rental, regulated in the building codes?
RESPONSE 1: Where Portland zoning offers the option of an Accessory Short-Term Rental (ASTR) in a structure built as a one- or two-family dwelling, the structure can be used for short-term rental under an ASTR permit and remain regulated as a one- or two-family dwelling under the Oregon Residential Specialty Code (ORSC). This rests on the fact that an ASTR has a permanent resident in part of the house for most of the year. It aligns with the option in ORSC Chapter 1 for “detached owner-occupied lodging houses containing not more than five guestrooms” (e.g. “bed & breakfasts”) to stay within the scope of the residential building code. City of Portland Title 33.207 specifies the permanent resident must occupy the dwelling unit for at least 270 days during the calendar year. This keeps the short-term rental use as accessory to the primary use of non-transient housing.
In order to remain under the scoping of the ORSC, the permanent residency requirement must be met with use of space in the same structure as the ASTR. For example, a caretaker in a separate building on the property does not open up the option for another building on the site to be used for full time transient use without complying with the Oregon Structural Specialty Code (OSSC) as a transient use structure.
- Exception: However, where the zoning regulations allow a Type A accessory short-term rental in a detached accessory dwelling unit (ADU), the reduced size of the structure, limited number of transient use bedrooms and guests, and accessory nature of the use will be allowed in the detached ADU without a permanent resident and may remain regulated under the ORSC.
Where a structure built as a one- or two-family dwelling is used for short-term rental and chooses to be a “hotel” (Retail Sales and Service under the City of Portland Title 33 Zoning Code) and consequently has no permanent resident, it will be regulated under the commercial building code, which is the OSSC. Where the structure contains only one or two transient use dwelling units and each unit has a maximum of 10 occupants as calculated by Chapter 10, the City of Portland will allow the structure to be considered a Group R-3 transient use congregate living facility instead of a Group R-1 Hotel.
QUESTION 2: Are any alternatives to the requirements of the OSSC allowed when a structure built as a one- or two-family dwelling is converted to transient use?
RESPONSE 2: Yes. This code guide establishes minimum standards for conversions to Group R-3 transient use.
Scope. In order to use any of the options in this code guide, the building and scope of work must meet the following criteria:
- The building must be a legally permitted, detached one- or two-family residence. Townhouses are not included in the scope of this code guide.
- The structure must be limited to one or two dwelling units, each having a maximum of 10 occupants as calculated by Chapter 10. Typically, this means each dwelling unit is 2,000 sf maximum. Structures with three or more dwelling units to be rented on a short-term basis are not included in the scope of this code guide.
Structures with previously permitted converted space using the reduced standards in the Habitable Space Code Guide or Accessory Dwelling Unit Code Guide will be required to make the following improvements:
- Occupiable spaces shall have a ceiling height, including projections such as beams and mechanical ducts, of not less than 6'-8."
- Required fire rated separations shall be determined based on one of the methods in OSSC 703.2.
Previously permitted habitable spaces will not be required to further upgrade existing elements of the building's thermal envelope, existing sound separation measures, or existing stairs with at least a 6'-4" clear headroom.
- Additions to the existing structure shall conform to the requirements of OSSC Chapter 34.
The following list of requirements is not intended as an exhaustive list of OSSC compliance for R-3 transient use. Each section below outlines a straight code requirement, and one or more alternative options that will be accepted as providing equivalency.
Fire sprinkler system: OSSC requires NFPA 13D fire sprinklers to be installed throughout the building when a one- or two-family dwelling is converted to R-3 transient use. Options 1 and 2 may be used for a detached dwelling unit, occupied by a single group at any one time. A one-family dwelling unit with an attached Accessory Dwelling Unit (ADU) converted to two units of R-3 transient use is not included in these fire sprinkler equivalency options.
Equivalent option 1: A one-family dwelling unit may be converted to R-3 transient use without installing a fire sprinkler system where all the following conditions are met:
- The fire separation distance is at least 5’ on all sides.
- The structure is a single story above grade. A basement level is also allowed, as long as it fits within the maximum gross building area.
- The maximum exit access travel distance does not exceed 75’.
- There are a minimum of two exits from the structure.
- The structure is less than 2000 sf gross building area.
Equivalent option 2: A one-family dwelling unit may be converted to R-3 transient use without installing a fire sprinkler system where all the following conditions are met:
- The fire separation distance is at least 10’ on all sides.
- The maximum exit access travel distance does not exceed 75’.
- There are a minimum of two exits from the structure.
- The structure is less than 2000 sf gross building area.
- Exterior wall and opening protection: OSSC requires fire protection for exterior walls, openings, and projections based on fire separation distance (FSD).
- FSD 5’ or more: Exterior walls are allowed to be unrated with unlimited unprotected openings.
- FSD 3' to 5’:
- Exterior walls are required to be one-hour fire-resistance rated and up to 25% of the wall area of each story may be unprotected openings.
Combustible eaves with less than 5' FSD are required to be one-hour fire-rated, heavy timber construction, or fire-retardant treated wood.
Equivalent options:
a. Existing interior and exterior finishes in areas previously permitted as "habitable space" may remain, instead of upgrading to a one-hour fire-resistance rated wall tested from both sides.
b. Existing eaves with more than 3' FSD may remain unprotected.
- FSD less than 3':
- Exterior walls are required to be one-hour fire-resistance rated.
- No unprotected openings are allowed.
Combustible eaves are required to be one-hour fire-rated, heavy timber construction, or fire-retardant treated wood. Projections, including eaves, are not permitted less than 2' from the line used to determine FSD.
Equivalent options:
a. Exterior walls may add one layer of 5/8" Type X fire rated gypsum board to the interior side of the exterior walls, instead of upgrading to a one-hour fire-resistance rated wall tested from both sides.
b. Up to 25% openings per story will be allowed if the openings have fixed glazing in non-operable windows with an additional sprinkler head at each opening.
c. Existing eaves with at least 6" FSD may remain provided they are fire rated and an NFPA 13D sprinkler system is installed throughout the full structure.
- Fire and Sound Separations: If the congregate living facility is rented as a whole unit and the bedrooms are not rented independently, sound and fire rated separations are not required for the bedrooms as sleeping units.
HISTORY: Implemented August 14, 2024.
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