Fixing San Francisco's troubled Millennium Tower may come down to understanding exactly how it was built, according to one university professor studying the phenomenon. The tower has sunk 16 inches, well over the 12 inches expected for the building’s lifetime, and homeowners have sued over the situation. The current problems have contributed to a decline in asking prices for the multimillion-dollar condos housed in the tower.

Iowa State University architectural design professor Tom Leslie says the tower was built with a concrete frame and a foundation that rests on 950 friction piles, reports the San Francisco Business Times. Comparatively, most of the city’s other skyscrapers have steel frames. How the engineers placed the piles anchored into the Colma Foundation of dense sand likely contributed to the current rotational balance and leaning of the building, he says.

Tom says the tower’s sinking could be at least slowed by building a larger, heavier structure immediately north of the tower that is connected to the building’s frame to balance out and support the other structure, similar to a fix used for the Fisher Building in 1907.

Millennium Partners previously stated nearby construction of the Transbay Transit Center led to the tower’s troubles.

Lawsuits from homeowners further point the finger at the Transbay Joint Power Authority and other transit agencies. TJPA provided $58M for an underground support system in 2010 before construction even began. [SFBT]