People who expect all old buildings to be torn down for redevelopment are being unrealistic, says Urban Renewal Authority managing director Billy Lam Chung-Lun. On RTHK's Hong Kong Letter radio programme, Mr Lam said: 'This is unrealistic under the current economic environment. 'We have to ask ourselves - is it a must to demolish many old buildings which can be maintained? Is demolition of flats for redevelopment the only way to improve the living environment?' The administration estimated that 9,300 buildings were more than 30 years old and the figure would double in 10 years, he said. 'If we were to demolish all 9,300 buildings for redevelopment, it would cost an astronomical figure,' he said. Mr Lam said it was one of two 'ideological mountains' the community should unite to get rid of. The public also should not think it was the sole responsibility of the authority and the government to improve people's living environment, he said. He said the second 'ideological mountain' was residents thinking that the authority should 'give away money to buy flats'.