New city rules allowing 75-foot tall buildings in downtown San Luis Obispo will go into effect Oct. 18, following approval by a City Council majority on Sept. 18.

Councilmember Christine Mulholland was the lone "no" vote, based upon her assertion that the majority of city residents don't want taller buildings downtown.

The council's action approves amendments to the zoning regulations, spelling out the conditions for taller buildings between 60 and 75 feet high. A Planning Commission use permit is required, and the commission must find that public benefits "significantly outweigh" any detrimental effects from the additional height.

Considered "especially important" public benefits under the ordinance are affordable and workforce housing, economic vitality, historic preservation, and open space preservation.

During consideration of the new building height rules, the city's Planning Commission decided after three public hearings to require developers to preserve or reuse any historic buildings on the property. The City Council's action eliminates that requirement, paving the way for destruction of more than 80 historic buildings downtown if the property is redeveloped with taller buildings.

Councilmembers also decided to eliminate the Planning Commission's requirement for upper floors to be set back in a tiered, "wedding cake" fashion, which would have allowed more sunlight to reach sidewalks.

The new ordinance spells out a variety of "policy objectives" to be met for buildings between 60 and 75 feet tall, with developers allowed to choose two from the list. The objectives include affordable housing, mid-block pedestrian connections between major downtown streets, incorporating a public plaza with public art, incorporating a public viewing deck for views of Cerro San Luis and other peaks, energy efficiency, protection of historic resources or open space in the city's greenbelt, and "other" with Planning Commission approval.

The new rules also specify that downtown residences don't include a guarantee of parking onsite or offsite.

Retail stores in new downtown buildings can be up to 140,000 square feet the size of Costco on Los Osos Valley Road with Planning Commission approval.