The Kingdom Tower's foundation design is also simpler than the burj's. There is no bedrock at the site along the Red Sea, which contains a form of limestone made from decomposed coral. The foundation design calls for 270 augured piles that reach 50 to 70 m below grade, topped by a mat.

Once the piles are in, there is no excavation. The 4-m-deep mat is one level above grade. That means no digging down into the water table—which is close to the surface because of the proximity to the Red Sea—and no dewatering. "We couldn't get big enough pumps to dewater the site. It would have been like trying to dewater the sea," said Peter Weismantle.

The designers also learned that a simpler skin would be beneficial.  "It's not anywhere near as complex as the burj," said Smith.

The design of the Kingdom Tower may be paying heed to issues of constructibility, but that in no way means the project is easy.

For example, during the time-out period, the developer made a decision to make every unit bigger and increase their number. The design team then went back to the drawing board and added one meter to the slabs around the perimeter and 20 more floors to the occupied space. "That reversed a lot of what we had done to make things more compact," said Smith.

As of last fall, the plan was for a building topped by a structural concrete spire. No one has ever pumped concrete up one kilometer. "The issue will be the mix design and labor at the top," said Weismantle. "To have a mix that can be pumped and placed at these heights [is a big challenge]," he added.

Wind loads also required attention. Early on, there was concern because the tower's edges were so sharp. But wind-tunnel tests showed no need to round the corners. "It's a well-behaved building," said Sinn. "The experience of Adrian and his team paid off," he added.

Peter A. Irwin, RWDI's chairman, agrees. For the burj, RWDI tested many iterations on the shape and "a lot was learned," said Irwin. "On Kingdom Tower, we started with a good shape and didn't do as many iterations."

John Galsworthy, RWDI's project director, agreed, saying, "In tests, the tapering form helped to mitigate cross-wind excitation, known as vortex shedding."

In terms of the building's technology, everything is pushed a step rather than being a radical departure—except for the elevator technology, said Weismantle.