In line with other cities in the kingdom, Jeddah is planning to develop several high-rise towers (see Feature, page 29). However, the schemes are proving more difficult to build than in other cities.

“The sub-surface, which is composed of coral, is not strong,” says a Riyadh-based geo-technical specialist. “It is challenging to construct from an engineering point of view.”

This is having an impact on the height of towers that developers are willing to construct.

“It needs a very cautious judgement as it is a challenging condition regardless of the foundations you choose,” he adds.

The difficulties are causing changes to some developments. The Headquarters Business Park, being developed by Aldar al-Khasa, is being re-designed.

“The old design had the load in a single area,” says Raed al-Shaksheer, special projects manager at Aldar al-Khasa. “So we modified the design to avoid settlement. The nature of the soil gives you a sense of extra caution.”

The 310-metre-high Lamar Towers, being developed by the UAE-Cayan Investment Company has had to deal with cavities in the sub-structure, which need to be filled to ensure stability.

“They have had to modify their equipment to do deeper piles,” says a source close to the project.

“These cavities get filled with silt or sand which is unstable.”