Essential repair work to keep Norfolk County Council's headquarters in use will start next year - after officials today announced a �14m deal for the first phase.

A study investigating the long-term future of County Hall, in Martineau Lane, Norwich, revealed it will cost �22.2m over the next 25 years to repair the building's structure.

Areas flagged-up in need of attention included leaks in the roof drainage system, wall insulation, a more efficient heating system, asbestos removal and improved lighting and fire alarms.

Canopies have also been used since 2011 at the office's entrance to protect the 1,200 or so staff and visitors from any threat of falling masonry. A move to a new HQ was ruled out for being too costly.

Now, it has been announced building firm RG Carter, based in Norfolk and across East Anglia, will work with the authority for the rest of this year to plan the County Hall repairs.

Work is expected to start in spring 2013 and last until 2015. The deal is for the first of three phases required for the building.

Council officials say they hope it will create a 'leaner and greener' building, with the aim for all Norwich-based staff to use County Hall instead of other offices.

It is hoped this will save �2m a year and make better use of County Hall, which was built in 1968.

RG Carter's repair work is expected to start at the top of the tower on the roof, rooftop plant and eighth floor.

Mike Britch, managing director of NPS Property Consultants, said: 'The most obvious sign that County Hall needs major maintenance is the scaffolding protecting staff and visitors from falling facing tiles, but in fact there are other less visible problems that have to be put right.

'Things such as leaks in the roof drainage system, hidden inside the walls, and problems with the sewers, drains, water and heating systems that are reaching the end of their lives. Movement in the building, although not an immediate risk, requires further investigation so that remedial action can be taken.'

Cliff Jordan, the council's cabinet member for efficiency, said: 'We looked at a number of options, but even with an overall maintenance cost of over �22m, retaining County Hall is the most practical and affordable solution.

'The costs will be offset by savings of up to �2m as staff vacate other buildings and move to County Hall. This is already under way - for example, moving staff out of Sapphire House (Roundtree Way) will save over �300,000 a year.'