THE proliferation of potentially dangerous illegal structures could be stemmed if the Government cut the cost of approving building plans, engineers and architects said. There are about one million unauthorised building works in the territory ranging from rooftop houses to flower racks, canopies and metal cages. But the industry says many could be built more securely if the Buildings Department reduced the price and speeded up the process of approving plans. The department charges building and flat owners $10,300 to pass each design. This is expected to rise by 10 per cent in September after a government review. For most minor work, this is more than the cost of the construction materials, especially if two or three drawings are needed for a rooftop structure, such as a sun lounge or terrace. 'If the structure is simple the architect or engineer could probably get it all on one drawing, but something more substantial would require two or three drawings,' said leading consultant, Mouchel Asia director, Nigel Mattravers. Instead, he said that the department should exempt minor work from charges introduced three years ago to cover the cost of checking and approving the drawings submitted. The Hong Kong Institution of Engineers agreed with Mr Mattravers. 'Nobody is going to spend money if they do not have to,' said secretary John Boyd.