The 123-story Lotte World Tower currently under construction in Seoul’s Jamsil needs immediate reinforcement as 98 cracks were found on the surface of the mega columns which form the building’s framework.

“Rain can seep into the widening cracks in the mega columns and lead to corrosion of the steel frames inside,” said Shin Sung-woo, chief of the diagnostic team jointly organized by the Architectural Institute of Korea and the Korea Infrastructure Safety Corporation.

“Immediate repairs and reinforcement are necessary.”

There is no need to worry about the building collapsing, but the steel frames could expand as they rust with rainwater and cause more cracks, Shin said.

“Small cracks can be filled in with high-strength mortar, a mixture of cement and sand, and cracks of more than 0.3 millimeters in width require use of a plastic adhesive called epoxy,” he said.

Lotte Group spokesman Park Sang-sup said the reinforcement work would begin soon and be completed within a week.

The 98 cracks, caused by welding heat, were found in 24 mega columns in seven floors from the fourth to 10th floor of Lotte World Tower, according to the diagnostic team.

“The cracks do not affect the safety of the building, so construction can be continued, but the same thing could happen again on the 72nd floor which requires a lot of welding,” Shin said.

“We plan to present a plan to prevent cracks to Lotte Engineering and Construction.”

Shin noted that Lotte did not comply with the construction inspector’s instructions last October to refrain from additional welding operations before reinforcement.

“The builder should have done the reinforcement work in consultation with the construction inspector. But it didn’t, and that is the reality of the Korean construction industry,” he said.

Shin’s team began the diagnosis upon a request from Seoul City and Lotte E&C.

Lotte World Tower is scheduled to be completed by the end of 2015.

By Kim So-hyun (sophie@heraldcorp.com)