Building a terrace: promising or utopian?

With climate change, urban agriculture is increasingly mentioned, in particular by using the roofs of large urban complexes which offer an interesting surface to engage in agriculture in the city or even livestock farming. So, regarding urban vegetable gardens and other initiatives, are these plans for the future or unrealistic ambitions?

Urban agriculture: no improvisation

The period of confinement has reinforced the need for nature in the city, short circuits, solidarity, local production or even on your balcony. Being seduced by urban agriculture is not limited to projecting yourself into the development of a roof terrace quickly done – well (badly) done! On the contrary, there is nothing simple about this form of agriculture since it has to bear more constraints linked to the extraordinary conditions that are specific to it, not to mention the regulations, substantial installation costs as well as issues that are not always as clear as they were imagined. As each roof is different in its shape, design, structure, location, accessibility (physical but also in terms of water and electricity in particular).

The different techniques of urban agriculture

By nature, the roof of a building is not covered with earth, which is why we speak of "above ground" crops as opposed to "open field" crops. The substrate provided may be organic (topsoil or potting soil) for growing in containers or beds, but it may also not be organic if it is clay balls, pozzolan, vermiculite, water enriched with nutrients for including crops in hydroponics, aeroponics or bioponics.

Whether it's urban micro-farms, edible restaurant terraces, collective gardens (shared, corporate, educational-therapeutic) or productive urban farms, the techniques will be different.

The benefits of a flat roof

Whatever the type of technique chosen for an urban agriculture project, cooperation between the city and its inhabitants is created and positioned at the heart of social and economic issues.

Among the benefits observed following the creation of a flat roof, we must not neglect the environmental advantages which concern the retention of rainwater making it possible to fight against the risks of flooding linked to the increasing waterproofing of soils in the city, the multiplication of biodiversity refuges to accommodate pollinating species in particular, or the thermal insulation of the building on which crops are planted.

Urban agriculture, by definition, finds its place in cities, but these are sources of pollution that should not be overlooked, whether water, air due to road traffic and industrial activities and the substrate provided, which is sometimes of mediocre quality.

We can therefore clearly see the importance of tending towards a circular economy operation with the recovery of rainwater, the filtration of gray water, or the recycling of organic waste from the inhabitants via compost (or even urine) to improve the soil the roof terrace rather than increasing the external waste treatment load. Photovoltaic panels can also be installed to heat a greenhouse or provide electricity.

You can also use so called artificial stones, widely known as faux rocks. Read more on https://gartendek.lt