Portland, OR Building Safety: Anti-Mansionization (2026)

Floor area ratios (FAR) work with height, setback, and building coverage requirements to control the overall bulk and placement of buildings. The maximum FAR allowances have been calibrated by zone to:

• Define the character of each zone by establishing greater FAR allowances in the higher intensity zones;

• Encourage the provision of additional dwelling units within existing neighborhoods by relating the allowed amount of FAR to the total number of units on a site; and

• Ensure that the bulk of buildings on one lot does not overwhelm development on adjacent lots.

B. Maximum FAR. Maximum floor area ratios are stated in Table 110-4. Maximum FAR applies to all buildings on the lot, however the maximum allowed is based on the total number of dwelling units on the lot and whether a bonus option is chosen. In the R10 and R20 zones, the maximum FAR only applies to lots that are less than 10,000 square feet in area. The maximum FAR for a lot with a congregate housing facility is the same as shown in Table 110-4 for a lot with 1 total dwelling unit. The maximum FAR for institutional uses is stated in 33.110.270. Adjustments to the maximum FAR ratios, including bonus ratios, are prohibited.

C. Exceptions.

1. Maximum FAR does not apply to one alteration or addition of up to 250 square feet when the alteration or addition is to a primary structure that received final inspection at least 5 years ago. This exception is allowed once every 5 years.