The legislation allows a 30% height increase for buildings in the Denny Triangle, parts of Belltown, the financial district and around the Pike Place Market. Several condominium developers are poised to take advantage.

In exchange, the so-called Downtown Livability Plan requires that residential developers pay a per-sf fee that increases along with the height of their building. Of that fee, which averages $19 per sf for the upper floors of a building, 75% goes directly to an affordable housing fund. A similar fee is already charged on office towers.

The changes are being touted as a way to address transportation and sprawl issues and step in-line with the state's growth plan, which calls for existing urban areas to take on more residents in an effort to concentrate people near their jobs. With incomes increasing along with traffic, land supplies dwindling and empty-nesters seeking greater proximity to cultural amenities, the idea is gaining momentum.

The legislation repeals height limits voters set on downtown buildings in the 1989 CAP Initiative, which was approved four years after completion of the city's tallest skyscraper, the 76-story Bank of American Tower, known as Columbia Center. The change is unlikely to spawn 80-story office towers, but it is expected to spark more 50-story condominium towers on the outskirts of the Downtown core, such as Belltown, the Denny Triangle and SoDo, where heights limits have been in the 30-story range.

Other rule changes include a requirement that taller buildings in the more residential areas of Downtown have a certain separation from one another. In such areas, the new spacing requirement ranges from 60- to 80-feet feet. However, the council has directed city planner to study how the change affects property owners in the areas, leaving the door open for a revision.

Additional rules require developers to build more energy-efficient high-rises, include awnings to keep people dry during Seattle's rainy season, and build more parking underground. The largest office towers also would have to install showers for bicycle commuters. Previously, developers received height bonuses for providing such amenities.