As the city grows vertically, concepts such as vertical farming and rooftop gardens are becoming more and more familiar.

Interestingly, while the custodians of Lahore’s development, especially the Lahore Development Authority (LDA), have made it mandatory for all high-rise buildings to convert 50 percent of their rooftops into green spaces — and for this the authority has also issued notices to buildings over noncompliance — they are yet to devise bylaws and rules related to roof top gardening.

Also, it has been observed that what is being done in the name of rooftop gardening is in some cases merely ornamental or decorative.

Rauf Aslam, an urban planner, says a green roof or rooftop garden is a vegetative layer grown on a rooftop. “Green roof systems include several layers, including structural support, vapour barrier, thermal insulation, root barrier, drainage layer, filter membrane, growing medium and vegetation.”

Aslam defines rooftop garden as a type of farming atop a building, or a home, or some residential infrastructure. It can range from raised beds and pots, rolled-out green carpets, shaded roofs containing planting cells that are filled with soil or compost and planted up with low-growing perennials and grasses.

In response to a question, he says that apart from the decorative value, a rooftop garden serves to provide architectural enhancement, temperature control, recreational opportunities and habitats for wildlife.

LDA’s chief town planner Shakeel Anjum Minhas admits that there may be no clear definition of rooftop garden in the authority’s books. He says rules and regulations are being worked out to that effect and should soon be up for approval.

Minhas also agrees that currently most high-rise buildings have only decorated their rooftops by placing planters and laying artificial grass. “At least, the builders and contractors are becoming inclined towards going green,” he adds. “Hopefully, this will lead to an easy adoption of rooftop vegetation in the future.”

It may be mentioned here that the Lahore High Court (LHC) recently constituted a committee to find solutions for air pollution and smog in the provincial metropolis.

The former head of TEPA, Abdul Razzaq Chauhan, says rooftop gardens not only have aesthetic appeal but also contribute to lowering the temperature in the surroundings. “[Green roofs] can be used as a weapon against climate change. These help in reducing energy use by bringing down the demand for air-conditioners,” he says. “They also absorb various poisonous gases in the air and help lower ozone levels.

Salman Ahmed, a private town planner, seconds Chauhan by saying that rooftop vegetation provides “great insulation by retaining heat in winters and keeping the temperatures on the cooler side in summers.”

Ahmed quotes a study according to which Copenhagen made rooftop gardens mandatory in 2010 for all new commercial buildings with a roof slope of less than 30 degrees. In 2016, the city of Córdoba in Argentina issued a bylaw that mandated all buildings with rooftops of more than 1,300 square feet to be turned into green roofs. The same year, San Francisco decreed that 15 to 30 percent of roof space on new buildings should incorporate solar panels or green roofs, or both. More recently, the New York City Council passed a law to reduce greenhouse gases; it includes a requirement for green roofs or solar panels, or a combination of the two, on newly constructed buildings. Washington DC’s storm water regulations and Philadelphia’s tax credit, too, encourage green roofs.

A town planner in LDA tells TNS on condition of anonymity that the strength of a building’s structure must be considered before launching into rooftop gardening, as the weight of a garden can be too much to bear for many a roof.

Secondly, a system of waterproofing must be installed on top of the buildings with a complete drainage system and roof protection mats. In the absence of these precautions, the goal cannot be achieved, he says.

For Minhas, bylaws with respect to technical requirements for rooftop plantation are under consideration by the LDA and would soon be reviewed by the authority for implementation.

The writer is a senior reporter at The News