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Smart Bylaws Guide – Secondary Suites – Portland

The City of Portland established a comprehensive scheme for regulating the development of secondary suites in a variety of ways (attached, detached, no additional parking required in certain circumstances, not included in density calculations for site).

Title 33, Planning and Zoning Chapter 33.205 City of Portland

7/1/02 Accessory Dwelling Units 205-1

CHAPTER 33.205 - ACCESSORY DWELLING UNITS

(Amended by:  Ord. No. 171879, effective 2/2/98; Ord. No. 174263, effective 4/15/00; Ord. No.175837, effective 9/7/01; Ord. Nos. 175965 and 176333, effective 7/1/02.)

Sections:
33.205.010  Purpose
33.205.020  Where These Regulations Apply
33.205.030  Design Standards
33.205.040  Density

33.205.010  Purpose

Accessory dwelling units are allowed in certain situations to:

• Create new housing units while respecting the look and scale of single-dwelling development;
• Increase the housing stock of existing neighborhoods in a manner that is less intense than alternatives;
• Allow more efficient use of existing housing stock and infrastructure;
• Provide a mix of housing that responds to changing family needs and smaller households;
• Provide a means for residents, particularly seniors, single parents, and families with grown children, to remain in their homes and neighbourhoods, and obtain extra income, security, companionship and services; and
• Provide a broader range of accessible and more affordable housing.

33.205.020  Where These Regulations Apply

An accessory dwelling unit may be added to a house, attached house, or manufactured home in an R zone, except for attached houses in the R20 through R5 zones that were built using the regulations of 33.110.240.F, Duplexes and Attached Houses on Corners.

33.205.030  Design Standards

A. Purpose.  Standards for creating accessory dwelling units address the following purposes:

• Ensure that accessory dwelling units are compatible with the desired character and livability of Portland's residential zones;
• Respect the general building scale and placement of structures to allow sharing of common space on the lot, such as driveways and yards;
• Ensure that accessory dwelling units are smaller in size than houses, attached houses, or manufactured homes; and
• Provide adequate flexibility to site buildings so that they fit the topography of sites.

B. Generally.  The design standards for accessory dwelling units are stated in this section.  If not addressed in this section, the base zone development standards apply.

C. Requirements for all accessory dwelling units.  All accessory dwelling units must meet the following:

1. Creation.  An accessory dwelling unit may only be created through the following methods:

a. Converting existing living area, attic, basement or garage;

b. Adding floor area;

c. Constructing a detached accessory dwelling unit on a site with an existing house, attached house, or manufactured home; or

d. Constructing a new house, attached house, or manufactured home with an internal or detached accessory dwelling unit.

2. Number of residents.  The total number of individuals that reside in both units may not exceed the number that is allowed for a household.

3. Other uses.

a. An accessory dwelling unit is prohibited on a site with a Type B home occupation.

b. An accessory dwelling unit is allowed on a site with an approved Bed and Breakfast facility if the accessory dwelling unit meets the standards of Paragraph 33.815.040.B.1.

4. Location of entrances.  Only one entrance may be located on the facade of the house, attached house, or manufactured home facing the street, unless the house, attached house, or manufactured home contained additional entrances before the accessory dwelling unit was created.  An exception to this regulation is entrances that do not have access from the ground such as entrances from balconies or decks.

5. Parking.

a. Purpose.  The parking requirements balance the need to provide adequate parking while maintaining the character of single-dwelling development and reducing the amount of impervious surface on a site.  More parking is required when a vacant lot is being developed because, generally, the site can more easily be designed to accommodate two parking spaces while minimizing impervious surface.  In situations where an accessory dwelling unit is being added to a site with an existing dwelling unit, it is appropriate to not require additional impervious surface if adequate on-street parking is available.

b. The following parking requirements apply to accessory dwelling units. All parking must meet the requirements of 33.266.120, Development Standards for Houses, Attached Houses, and Duplexes:

(1) No additional parking space required. No additional parking space is required for the accessory dwelling unit if it is created on a site with an existing house, attached house, or manufactured home and the roadway in at least one abutting street is at least 28 feet wide.

(2) One additional parking space required. One additional parking space is required for the accessory dwelling unit as follows:

  When none of the roadways in abutting streets are at least 28 feet wide; or

  When the accessory dwelling unit is created at the same time as the house, attached house, or manufactured home.

6. Maximum size. The size of the accessory dwelling unit may be no more than 33% of the living area of the house, attached house, or manufactured home or 800 square feet, whichever is less.

D. Additional requirements for accessory dwelling units created through the addition of floor area.  Accessory dwelling units created through the addition of floor area must meet the following:

1. Exterior finish materials.  The exterior finish material must be the same or visually match in type, size and placement, the exterior finish material of the house, attached house, or manufactured home.

2. Roof pitch.  The roof pitch must be the same as the predominant roof pitch of the house, attached house, or manufactured home.

3. Trim.  Trim on edges of elements on the addition must be the same in type, size, and location as the trim used on the rest of the house, attached house, or manufactured home.

4. Windows.  Windows must match those in the house, attached house, or manufactured home in proportion (relationship of width to height) and orientation (horizontal or vertical).

5. Eaves.  Eaves must project from the building walls the same distance as the eaves on the rest of the house, attached house, or manufactured home.

E. Additional requirements for detached accessory dwelling units.  Detached accessory dwelling units must meet the following:

1. Setbacks.  The accessory dwelling unit must be at least:

a. 60 feet from the front lot line; or

b. 6 feet behind the house, attached house, or manufactured home.

2. Conversion of existing detached garages.

a. In RF through R2.5 zones, conversion of an existing detached garage that is in a front, rear, or side building setback required by Table 110-3 is not allowed.  This restriction also applies to garages that are allowed to be in side or rear setbacks as provided by Subsection 33.110.250.E, Special Standards for Garages.

b. In R3 through IR zones, conversion of an existing detached garage that is in a front, rear, or side building setback required by Table 120-3 is not allowed.  This restriction also applies to garages that are allowed to be inside or rear setbacks as provided by Subsection 33.120.280.E, Special Standards for Garages.

3. Height.  The maximum height allowed for a detached accessory dwelling unit is 18 feet.

4. Bulk limitation.  The detached accessory dwelling unit may not have a larger footprint than the footprint of the house, attached house, or manufactured home, and, the combined footprint of all detached accessory structures may not exceed 15 percent of the total area of the site.

5. Exterior finish materials.  The exterior finish material must be the same or visually match in type, size and placement, the exterior finish material of the house, attached house, or manufactured home.

6. Roof pitch.  The roof pitch must be the same as the predominant roof pitch of the house, attached house, or manufactured home.

7. Trim.  Trim must be the same in type, size, and location as the trim used on the house, attached house, or manufactured home.

8. Windows.  Windows must match those in the house, attached house, or manufactured home in proportion (relationship of width to height) and orientation (horizontal or vertical).

9. Eaves.  Eaves must project from the building walls the same distance as the eaves on the house, attached house, or manufactured home.

33.205.040  Density

Accessory dwelling units are not included in the minimum or maximum density calculations for a site.