The work on the £20m headquarters of retirement firm Saga, in Folkestone, Kent, is due to start in June. The repairs are likely to be supervised by members of the original project team. This included construction manager Schal, project manager and QS Davis Langdon & Everest and structural engineer Arup.
Saga said in a statement: "Remedial works have been commissioned by Saga Group at The Saga Building in Sandgate, mainly to address problems associated with leaks that have persisted since Saga occupied the site in 1999. Every effort is being made to avoid any disruption to any of these businesses while the work takes place."
One source claimed that the leaks, which are associated with paintwork, were so bad that water was falling on desks in the office.
Another source, close to the client, said: "There will probably be bits of the building that will need to be reclad – it is to do with the fact that the paint has failed. Because it's an existing building, the option of trying to open up the building up and repaint it is bloody difficult. The other option is to overclad the steel."
He said Saga had been unimpressed with the project ever since it was handed over 1999 – even though it was praised by architectural critics.
The source said: "Since the client occupied the building it has forever had leaks. The client thought it was getting the construction industry's A-team on this landmark building. It is not a good advert for the construction industry."
The project team carrying out the repairs is expected to include an expert on leaking buildings as well as specialist contractors. Sir Michael Hopkins' practice, which was unavailable for comment, is being consulted over the fresh work.
Saga thought it was getting the A-team on this building. It is not a good advert for the building industry
Source close to client Saga
Problems first emerged in early 2000, when Saga confirmed that there were a number of faults with the 13,000 m2 headquarters, which includes offices, conference facilities, a crèche, a nursery and a 900-seat dining room.
The firm refused to give details of the difficulties but they were understood to include the cladding system, designed to allow natural ventilation.
This appeared to allow too much air to blow in, leading to draughts and disturbances from rattling window blinds.
This was made worse by the fact that the building faces the English Channel in one of the windiest parts of the UK.
One source underlined how difficult it was likely to be to put things right.
The source said: "It is an extraordinarily complex problem with no easy solution. Most signature buildings have an inherent problem somewhere."