A Changsha developer dazzled the world when it built a 30-storey hotel within 15 days. Now as it aims to construct the world's tallest building in a mere nine months, experts are raising questions about safety and wondering whether the project is part of a technological revolution or a public relations campaign. On Saturday, a ground-breaking ceremony marked the start of construction of an 838-metre, 208-storey skyscraper on the outskirts of Hunan’s capital city, which its developer Broad Group estimated would be completed by April next year. If all goes to plan, the building will be crowned the world’s tallest building and be 10 metres taller than the Burj Khalifa in Dubai, which currently holds the title. Some construction experts, however, have expressed doubts over the developer’s projections, questioning whether the astoundingly short construction period would be possible and whether the timeframe would compromise safety. “The techniques Broad Group are using are unprecedented in the world,” said Yin Zhi, director of Tsinghua University’s School of Urban Planning and Design. “It either has achieved a stunning breakthrough in architectural technologies, or it is a fraud,” Yin told cnr.cn, the website of state-run CCTV. Even if the project does signal a major breakthrough, Yin added, the technology could be put to better use in more economic and pragmatic areas, not to compete for the tallest-building title. Using a novel modular construction method, Broad Group pre-manufactures most parts of the building in factories, and then assembles them once construction starts – like building with giant Lego pieces. In 2011, a time-lapse video shocked the world, showing Broad Group building a Changsha building at a rate of two days per floor. Senior architect Lu Yin also found the Broad's projected construction period beyond belief, the CCTV website reported. He noted that what worked in the past for low-level buildings might not work on skyscrapers that are well over 100 floors. Super high-rise buildings usually take about five to 10 years to construct when using conventional techniques. Burj Khalifa in Dubai, for example, took Arabs 47 months to build. Zhang Yue, founder and chairman of the Broad Group, said the concerns were unnecessary. “The overall structure is extremely steady. It adopts that of a the pyramid shape and does not differ much from that of the Great Wall,” he told China News agency. With an all-steel frame and fire-proof boards, the building will survive earthquakes up to magnitude 9 and potential fires, Zhang added. Experts also raised doubts about potential safety hazards in the building last year when the building was still undergoing an assessment process. The director of Hunan University’s School of Architecture, Wei Chunyu, who was a member of the assessment panel, was concerned the building could have safety hazards. He was especially worried that if a fire erupted on higher levels, it would be hard to contain and lead to disasters. Accoding to the developer, the skycraper will have 1.05 million square metres floor space and cost a whopping 9 billion yuan (HK$11.3 billion) to build. Named “Sky City”, the mega building is designed to house various public facilities so the “building can serve as a city”, the developer boasted. It would house schools, an elderly care centre, hospital, offices in lower levels.