More than half of China's existing residential structures will be demolished and rebuilt in the coming 20 years, according to a senior researcher from the Ministry of Housing and Urban-Rural Development, a claim that has sparked fresh questions about the short lifespan of Chinese buildings.

Chen Huai, director of the policy research center at the ministry, was quoted on Friday by Southern Metropolis Daily as saying that homes built before 1999 will be dismantled to make way for new development during the next two decades. Chen said some historical relics that deserve protection will be spared the wrecking ball.

He explained that buildings constructed before 1949 have long passed their designed lifespan of 50 years. Many of those built between 1949 and 1979, for historical reasons, were essentially makeshift and met basic needs for housing during a difficult time but were not meant to be used for the long-term.

"Given China's fast economic development and pace of urbanization, houses built between 1979 and 1999 cannot meet the demands of modern living, either because of limited space or a lack of supporting facilities," he said. "Only those homes built after 1999 are likely to be preserved in the longer term."

Chen confirmed the Guangzhou-based newspaper report in an e-mail reply to China Daily later on Friday and said poor-quality houses are not a new problem in China and have been talked about for many years.

China annually sees more construction than any other country. In recent years, the nation has had up to 2 billion square meters of development annually. Each year, China uses 40 percent of the world's cement and steel, the main ingredients of the construction industry.

Around 40 percent of building land is created every year by the demolition of older developments.

But both experts and industry watchers have questioned the rapid speed of demolition and reconstruction, suggesting poor building practices and a lack of consistent urban planning, along with a blind pursuit of economic gain on the part of developers, are the real reasons for the relatively short lifespan of buildings.

In April, Qiu Baoxing, vice-minister of the ministry, said during an industry forum that Chinese buildings can only stand for between 25 and 30 years. In contrast, the average life expectancy of a building in Britain is 132 years and they last around 74 years in the United States.

"Although, before the 1970s, buildings did need to be rebuilt for safety reasons, what we see nowadays is the blind demolition of relatively new buildings, some of which have only been standing for less than 10 years," said Li Dexiang, deputy director of the school of architecture at Tsinghua University.

Yu Hongsheng, director of the Urbanization Research Center under the Shanghai Academy of Social Sciences, agreed.

"Today, there is an impulse from both the government and developers to build newer and higher buildings to gain greater profits, which has accelerated the pace of the demolition of old buildings. But it is actually not in line with the concept of sustainability and has even pushed up real estate prices," he said.

Yu added that ordinary working people end up bearing the brunt of rising house prices.

With China's urbanization rate likely to be close to 50 percent by 2015 and the growing need for more residential buildings, Yu suggested that the government invests more in developing towns in suburban areas where there is more land and less need for demolition before development.

Li also pointed out that the pursuit of profits coupled with a lack in consistency in urban planning had led to a huge waste of construction materials. He said the country should improve the recycling of reclaimed materials.

In China, construction waste comprises 30 to 40 percent of the total volume of urban waste. The erection of a 10,000-square-meter building typically creates 500 to 600 tons of waste and the demolition of a similar sized building creates 7,000 to 12,000 tons, according to industrial data.

Poor building quality is also a major concern for China's construction industry, which has been plagued by scandals in recent years.

In June 2009, a 13-floor newly-constructed building in Shanghai toppled, killing one worker. An investigation revealed its foundations had been undermined by a combination of soil piled 10 meters high on one side and the digging of an underground garage on the other.

The scandal was soon followed by numerous media reports of poor building quality in other parts of China.

"The rush for speed and pursuit of maximum economic interests are to blame," said Yu.