London’s Imperial War Museum has closed to visitors until July 2014 after ongoing building work unexpectedly revealed major infrastructure issues.

The museum reopened in July after being closed in the first half of 2013 for a full-scale refurbishment, but after work commenced on the infrastructure of the building, it was discovered a number of systems including electrics, air conditioning and media cabling needed a substantial upgrade.

The initial redevelopment costs were budgeted at £35m, but that has now been increased to £40m.

“We continue to actively fundraise and have now secured £36.7m,” said a spokesperson for the museum. “The project is fully affordable and we are confident that we will raise the remaining £3.3m from our sponsors.”

The museum will reopen in July – one month before the official start of the First World War centenary commemorations.