Besides the open yard, the only other option to grow greens is on the terrace, which incidentally is not a new idea, if we include the Hanging Gardens of Babylon in the green roof list. A look at terrace gardens by architect Sathya Prakash Varanashi
We build on the ground, so theoretically the ground gets transferred to the top of the building. If the ground could have been green, should not the new ground up above also have the options of going green? Of course, yes. Besides the open yard, the only other option to grow greens is on the terrace, which incidentally is not a new idea, if we include the Hanging Gardens of Babylon in the green roof list!
It is the risks involved with roof-top cultivation and lack of remedial solutions for the common problems that makes us leave the roof largely untouched. It is curious that the major driving force today for re-discovering green roofs is not the urge for growing flowers or vegetables, but ecological concerns.
Roof-top plants reduce both the heat gain into the building and heat reflection into the atmosphere, cooling both the building and the city.
Thanks to the evaporative processes, the relative humidity gets a positive boost, though one would need large areas of green roofs to achieve a noticeable difference. If we could begin in a small way today, someday that large area could be achieved.
Three key approaches
There are three basic approaches to greening the roof — plants directly on soil medium; assemblage of potted plants; and softscapes like ground creepers, vines or lawns. Let us first look at the general garden.
Direct planting reaps the maximum benefits, but requires the maximum attention too. The roof needs to be perfectly water proof and preferably designed to take the extra weight of planting. Even if the roof is guaranteed against cracks and leaks, it is advisable to fix a layer of impervious plastic-based lining on the roof top, before filling the surface. It also ensures smoother flow of extra water at the bottom, following watering of plants or long hours of rain.
There have been cases where people tried gardening on existing roofs, with inadequate roof slopes. In such cases, good slopes need to be created during the plastic lining, before the soil fill. If it is an old house, adding a water-proofed concrete layer could be considered before doing extensive gardening.
The patch where we go green and the leftover terrace have to be edged with appropriate materials such as brick on edge. Often, this edge gets ignored and the whole terrace gets wet due to water seepage from the sides!
Lightweight coconut pith compost, peat moss and such manure soil mix are among the better choices. When we do direct planting, it is easier to keep the soil moist, unlike the case of potted plants. Incidentally, the soil mix should not absorb too much water and retain it too, for this increases the load on the roof.
Plants with only fibrous roots are possible as the top soil mix will be just 4 to 6 inches deep. Of course, there are options in shrubs, herbs, flowering plants, crotons, vegetables, orchids, rose, small palms and such others. For those willing to spare their energies, this is a good enough range!
(The writer is an architect working for eco-friendly designs and can be contacted at email@example.com)