China is promoting prefabricated buildings as a way to save energy and help resolve the problem of excessive industrial capacity, the Ministry of Housing and Urban-Rural Development announced on Friday.
Prefabricated buildings are built using manufactured components that are assembled at the construction site. Based on a guide from the ministry, 30 percent of new buildings are to be prefab structures.
"Currently, we have a foundation to promote it, but progress is slow," said Su Yunshan, head of the Department of Energy Conservation, Science & Technology, which is part of the ministry. "Rough data shows that the current (prefab) rate is about 5 percent, but by our calculations, the goal is achievable."
Building prefab houses reduces construction waste as well as dust and noise, compared with the traditional cast-in-place technique, in which concrete is poured at its permanent location, according to Chen Yiming, the ministry's chief engineer. It also shortens the time needed for construction.
"Although situations vary due to types of buildings, the level of management and so on, statistics provided by enterprises showed that construction time can be cut up to a third in some projects," Chen said. "Use of construction materials such as cement, water and wood can be reduced by at least 15 percent."
Prefabricated construction is actually a mature architectural technology abroad, Chen said. Canada, for example, has been building an 18-story wooden prefab building.
The use of steel in prefab buildings also will help ease excessive steel capacity, though public acceptance may not be immediate.
"Like the transition from brick to concrete, it will take some time for people to accept steel-structure prefab buildings for their houses," Chen said. "Therefore we have to take things step by step."
The technique has already been used in China. News reports said it took only 19 days to assemble a 57-story prefab building in Changsha, in Hunan province. The builders explained, however, that while the assembly took 19 days, preparing the components took much longer.
The change is not expected to be an easy one. "We are still at an early age in terms of prefab buildings. The supporting policies aren't clear enough and the technology is still weak in some enterprises, which leads to a limited scale," said Liu Haiqun, deputy manager of the Central China zone for the China Construction Steel Structure Corp. Liu spoke in an interview with China Construction News.
Limited use in China means the cost is still higher than traditional techniques, which is one reason for a reluctance to try prefab, Su said.
"But our model projects have shown that with larger scale, the cost of prefab buildings will be the same or even lower than traditional ones," Su said.
