SWIRE Properties is to meet rising demand for offices by redeveloping part of Taikoo Shing's Cityplaza One shopping complex. A 22-storey office tower with a gross floor area of 617,240 square feet will be created on a site where there is currently 232,102 sq ft of retail space. The tower will also have six shopping floors with a gross floor area of 227,649 sq ft. The project will marginally cut retail space in Cityplaza One from 491,523 sq ft to about 487,000 sq ft. The company would not reveal the investment involved. The retail part of the redevelopment is expected to be completed in 1996, the office tower in 1997. General building plans have been approved and site work is scheduled to start next May. Sixty eight Cityplaza One retail tenants will have to move in April.