Portland has four National Register historic districts and six local conservation districts that are primarily zoned single-dwelling. These districts range from Ladd’s Addition to Woodlawn, Irvington to Kenton. The Residential Infill Project’s provisions for reducing the scale of houses and increasing the allowed range of housing types in single-dwelling zones will be integrated into the rules affecting these designated historic districts.
Properties listed in the National Register, either individually or as contributors to a historic district, are subject to demolition review, which requires a vote of City Council. Properties and districts listed in the National Register prior to February 2017 are subject to historic resource review for alteration, addition and new construction projects. Properties and districts listed in the National Register after February 2017 may be subject to historic resource review in the future, following a hearing and adoption process.
Because units in historic districts are subject to existing applicable demolition and historic resource review criteria, second Accessory Dwelling Units (ADUs), internal conversions of existing houses and new middle housing units would be allowed if the properties are within the new overlay zone only if they meet the appropriate review requirements. For a historic contributing building in a historic district, alternative housing types might look like one ADU in the basement and one in the backyard. For a noncontributing building, alternative housing types might look like a new duplex or triplex designed to fit the architectural vocabulary of the district.