Substandard work and poor maintenance have caused 500 incidents of tiles falling off walls at 11 public housing estates in Tin Shui Wai since February, a district representative said yesterday. At the worst hit estate, Tin Heng, which opened only four years ago, there were 300 such cases. Democratic Alliance for Betterment of Hong Kong legislator Cheung Hok-ming said the tiles had also fallen off in lift lobbies and corridors. The problem had been exacerbated by the moist weather, and repairs by the Housing Department had been slow, he said. Mr Cheung said it was lucky that no one had been hurt. In one extreme case at Tin Wah Estate, an entire sheet of tiles fell off a wall. 'There have been cases where whole sheets of tiles came off the wall. 'Fortunately, no residents were walking past at the time they fell down, so no casualty was caused,' said Mr Cheung, whose constituency is New Territories West. 'People moved into [Tin Wah] only in 1999, but the estate is suffering badly from the problem. We find this a bit hard to accept.' Tin Yat Estate, which opened in 2001 and has nine blocks with about 3,300 residents, has had about 100 tile-falling reports. The oldest estates opened in 1992 and 1993, while the most recent was Tin Yuet, where residents only moved in around 2002. Other affected estates include: Tin Chak, Tin Yiu, Tin Tsze, Tin Chung, Tin Oi, Tin Yau and Tin Shing. Mr Cheung said the problem was caused by walls not being properly prepared to attach the tiles. 'The base concrete walls should have been made rough before the tiles were pasted onto them so that they could be mounted more firmly,' he said. 'There should also be thorough checking of the tiles of the buildings in the estates in Tin Shui Wai. If bricks or tiles appear loose and about to fall, the department should be aware of the need to change them early.' The Housing Department last night promised to repair any fallen tiles as soon as possible. A department spokesman said some tiles were laid in certain patterns due to the design aesthetic of the building which may have contributed to the problem. Also, replacement tiles might be hard to find and may need to be specially ordered if they are not available on the market.