Guangzhou has carried out the green roof policy for more than one decade, but the implementation has encountered challenges. A report released by the Guangzhou Institute of Landscape Gardening showed that the green roof area of Guangzhou accounted for an estimated total area of only 0.5%, which is far less than Beijing, Shanghai and Shenzhen. Many residents encounter water seepage in buildings that have green roofs, and it also increases the management cost of building owners.

The city introduced the "Guangzhou Urban Greening Regulations" in 1997, which required all the new large-scale public buildings to have rooftop gardens when the conditions satisfied the public safety requirements. This provision was once considered the country's first green roof regulation. After this, the implementation of green roof work kicked off in Guangzhou. In 2007, the city started to carry out the "Green Roof Technical Specifications," which were compiled by the Guangzhou Research Institute of Landscape. The Technical Specifications include guidelines on green roof design, construction, and management. It requires new buildings to have rooftop gardens, and it also mandates old buildings to have safety testing before building the gardens. The regulation specifies ninety kinds of commonly used plants suitable for roof greening.

However, after being implemented for ten years, the effect of the green roof policy is not desirable. Liu Haitao, professor of the College of Horticulture in South China Agricultural University told reporters that he had conducted a survey about the roof greening in Guangzhou District, which showed that when not being required to contribute money, only 49% of the tenants, 47% of of property owners and 49% of households who live on the top floor agree to have rooftop greening on their buildings." If the top floor households are asked to contribute funding, the percentage of agreement will drop to ten," says Liu.

The Jinying Residential Community was among one of the first residential communities that implemented green roof policy eight years ago. The building has more than 1,500 square meters of public rooftop space. The policy was embraced by the tenants at the beginning, and they started to grow vegetables on the roof. The rooftop garden brought many benefits to the tenants, including cooling the building's temperature and providing public open space for leisure.

However, starting two years ago, cracks started to appear on the roofs, and in July of this year, dozens of households had varying degrees of water seepage. Testing agencies told residents that growing a large amount of plants for a long time caused uneven weight bearing and moisture, which resulted in cracks. The dead plant parts clogged the sewer and caused water damage. In order to fix the cracks, the Residential Community Committee paid high costs – including the maintenance cost and damage compensation for the tenants. Recently the Residential Community Committee decided to ban rooftop gardens in the community, and the decision was supported by most of the tenants.

What can the residents do to prevent potential property damage caused by the rooftop garden? What policies can Guangzhou carry out to increase the rooftop garden coverage?

Credits: Images and data linked to sources.

The original article, published in Chinese, can be found here.