Safety checks on high rise apartment blocks following this June’s horrific Grenfell Tower fire (ENR 6/26-7/3 p. 10) have revealed that essential reinforcing work ordered nearly 50 years ago on four 15-floor buildings may never have been done.

London’s Southwark Borough Council, the owner, has ordered gas supplies to be shut off from the Ledbury estate buildings to prevent a similar progressive collapse that caused four deaths at the Ronan Point block in May 1968.

The system-built, 22-floor Ronan Point had a primary structure of large precast slabs, assembled like a house of cards. And like a house of cards, an entire corner collapsed when an internal gas explosion on the 18th floor blew out a wall panel. An inquiry later that year led to calls for such buildings more than six floors tall to be reinforced and gas supplies to be cut off meanwhile.

Among the numerous U.K buildings identified for such retrofitting were the Ledbury blocks, then not in the hands of the current council. “All the reports we found suggested the blocks were strengthened following the Ronan Point incident,” claims the council’s deputy leader, Stephanie Cryan.

However, structural surveys by London-based Arup Group Ltd, ordered after the Grenfell fire, “suggest this strengthening may not have occurred, and we have therefore turned off the gas, until further investigations can be done.” The council has also written to government officials alerting them to the possibility that other high rises could be in the same potentially dangerous position.