St Petersburg in Russia, like all modern cities, has to cope with mountains of domestic waste. Its six million inhabitants have also experienced food shortages and many hardships over the past decade. But now a scheme to turn rooftops into gardens and waste into compost means that residents can grow their own fresh food.

Economic problems, pollution from heavy industries, lack of funding for environmental improvements and political unrest mean that conditions are poor for the inhabitants of St Petersburg. The life expectancy of men and women is far below European averages and up to 60 per cent of household income is used for food. St Petersburg alone produces 12,000 cubic metres of rubbish, which requires 3000 trucks for removal beyond the city borders. Most of this garbage comes from households.

Driven originally by a desire to improve the city environments, the St Petersburg Urban Gardening Club started to transform rooftops into valuable gardening space in 1993. In Russia most people in larger cities live in buildings with huge sturdy rooftops constructed to withstand heavy falls of snow. They also typically have very limited access to land. The scheme aims to give people access to gardens so that they can produce vegetables for their own consumption or to sell in the local market.

There are approximately 15 rooftop gardens and 100 participants in St Petersburg. The European Union (EU) provides funding, while a local organisation, Centre for Citizens Initiatives (CCI), provides consultations and teaching seminars, and furnishes technical and material assistance to urban residents and institutions that create rooftop gardens. Last but not least, community members build and manage the gardens themselves.

Theoretically, any roof surface can be greened – even sloped or curved roofs can support a layer of sod or wild flowers. It depends on how the garden is to be used, what the gardeners want to grow, and how often they will need to access the roof. A flat roof, approximating level ground conditions, is easy to work with.

One of the apartment blocks where the scheme has been introduced is cooperatively owned. Brick-built, with nine storeys, it houses 267 apartments with 540 residents, 60 per cent of whom are pensioners. It produces 200 kilos of food garbage daily in winter and 300 kilos in summer. The house has a flat roof of 1700 square metres, and 600 square metres of cellar. People living in the apartments compost their household waste in the cellar, recycle all other waste where possible, and then use soil on the roofs to grow vegetables.

While individuals own their apartments, the government owns the stairways and the rooftops. Permission is needed to use the rooftop in case of concerns about damage caused to the waterproofing by footfall. A surface has to be constructed to minimise this.

Technical Guidelines to Rooftops and Gardens
Does the roof garden increase the risk of water leakage or damage to the roof?
No. In fact, planting beds/surfaces can protect and insulate roofing systems. The following guidelines will help to avoid any potential problems.

A protective drainage layer between the soil and the membrane under planting beds, and raised surfacing treatment for non-planted areas, are measures that should avoid damage if the waterproof membrane is not protected from point loading, shovels, shoe heels, and dropped equipment.

Ensure that the roof drains have the proper covers, and that planters are lined with a layer of filter cloth and gravel to keep the soil from draining out with the water. Often a layer of filter cloth or drainage mat is laid over the whole roof, just on top of the waterproofing, to avoid this problem – especially if there is the likelihood of soil being spilled from planters, or sand removed from sandboxes. Otherwise, the roof drainage system may become clogged with sand, soil or vegetation, causing water to sit on the roof for long periods of time, allowing it to either break down the membrane or work its way through the seams. (Some waterproofing systems are designed for holding water, others are not.)

If leachate from plants, fertilisers, and/or composters comes in contact with certain roofing membranes, it may lead to membrane breakdown. If you find that the existing membrane is not compatible with these chemicals and organic compounds, the containers and planters could be lined with a continuous membrane, or placed on overflow trays; composters should never sit directly on the membrane because of their requirements for aeration and turning/working.

It may be difficult to locate and access a leak after the garden is in place. Movable planters/containers, modular walkways/surfacing treatment and compartmentalised planting beds could solve this problem.

How can rainwater falling on a site be used most effectively?
Slow down the flow of water to enhance absorption by texturing, terracing, planting and ensuring permeability of surfaces, especially on slopes (which should be as gradual as possible). Direct the flow of runoff to planted areas and retention areas so that as much water as possible can be retained on the site. Do not direct water to inlet drains unless essential due to weight limitations or inadequate waterproofing. Retain and store rainwater in a covered reservoir/cistern for later distribution to plants (watering by hand or by a ‘leaky pipe’ irrigation system). Ideally, runoff could be directed to a subsurface reservoir to provide water to plants on an ‘as-needed’ basis.

What issues are important in the design and construction of the rooftop garden?

Occupant load (i.e. the number of people occupying the garden) as it relates to and impacts on structural loading requirements exit requirements.

Exit requirements
types of exits allowed and number of exits required
distance between exits and travel distance to exits
sizes of exits and areas defined as ‘access to exits’
fire separations between exits and the rest of the floor area
possible requirements for fire alarms, exit lights, emergency lighting
Access for people with disabilities and barrier free design
Requirements for enclosures, i.e. guards, railings, parapets, walls around rooftops, terraces, and balconies required heights
the placement of elements such as planters adjacent to enclosures which may reduce their effective height climbability of enclosures
loading and structural stability of guards and railings.

Specific requirements for structures/buildings on roofs, relating to
effect on overall building height fire rating of structural parts exit arrangements

Other applicable issues might include
possible modification of window washing anchors on the roof
possible upgrading of washroom and service requirements
possible upgrading of drainage and waterproofing requirements

Structural considerations of rooftop gardens
There is the new loading exerted by the garden (the size and distribution of which can be changed by altering the layout of the garden) and there is the load-carrying capacity of the structure (which can be enhanced by increasing the strength of the building’s existing load-bearing parts or by adding new ones). When designing a roof garden consult a licensed engineer regarding the load-carrying capacity of the building you are working with and ensure that the garden design and the structural capacity are compatible.

The growing season lasts from mid-May to mid-September in Russia and leafy greens, potatoes, tomatoes, etc are predominantly grown in thin beds of 4 to 8 centimetres on the rooftop.

Separate containers for different kind of waste are built and installed. Residents are instructed about the need for and benefits of separate collection of garbage. Food waste is collected separately; up to 100 kilos of rotting vegetables are taken to the basement each week and pulped. The space in the cellar is modified for processing food garbage into compost with the help of red worms. Soil mix is critical because they cannot use organic matter from polluted city lawns and parks. When tested for heavy metals, vegetables from rooftop gardens had lower levels of metal contaminants than vegetables bought from city markets.

A bed is made with moistened newspaper in perforated plastic containers and 500 grams of worms, household vegetable waste and a sprinkling of peat moss and chalk are added to give the correct chemical balance. Finally, ground-up eggshell is used to absorb the moisture and give trace calcium before the container is covered. Once a week, 2 kilos of waste is added to each container and after two or three months the fertiliser is ready. The worms and their eggs are extracted and put to work in a new container.

Compost is used on the plot around the house for growing trees, bushes and flowers and on the roof for the rooftop garden. Excess compost may be used for production of soil for house plants, and this has a potential for becoming a small business.

Looking to the Future
The club has expanded its activities, setting up a vegetable garden in a prison in St Petersburg, providing both food and activities for the inmates. In 1998 a therapy garden was established in an artificial limb institute, providing invalids with a form of rehabilitation and basic knowledge of agriculture. A garden on top of a primary school is acting as a venue for children to integrate lessons with practical learning.

Project participants have taken part in city exhibitions, created an on-line rooftop gardening guide in Russian and published a book on the subject. Plans are in place to continue promoting the scheme and using the project as a model for others to learn from and replicate. CCI is managing a programme for sponsors to make donations and directly support a rooftop garden in St Petersburg. Residents can apply for funding for rooftop gardens and are selected by CCI on the basis of having a solid plan for developing their rooftops into productive gardens.

Green roofs reduce the ‘urban island’ effect whereby cities absorb and produce excess heat. Plants absorb CO2 emissions and improve the air quality, while also absorbing heat and causing a cooling effect. Green roofs insulate buildings and this can reduce energy costs by 10-20 per cent, thereby lowering the production of greenhouse gases.Green roofs can retain rainwater and generally use much less water for irrigation of plants. They may retain 50 per cent of winter precipitation that falls on them, and up to 100 per cent in the summer months.

Pests and diseases may be more easily controlled in urban gardens without the use of chemical pesticides, because they can be more easily and quickly dealt with. The lifespan of the roof may actually be lengthened with vegetative cover, as it protects the roof membrane from ultra-violet rays and temperature fluctuations.

The environmental, economic and social benefits of rooftop gardening are considerable. The scheme promotes community ownership and cooperation. It creates an outdoor green space and provides an opportunity for people to interact and build links between residents, to develop new skills and to take responsibility for managing a cooperative.

Its primary function is to support urban food production, increasing fresh food supply to residents, especially low-income people and pensioners, and reducing household expenditure on food. It can create one or two jobs and a source of income, add value of buildings for owners and tenants alike, and create favourable conditions for potential small businesses. The amount of solid waste is reduced through conscientious consumption and recycling. Costs of transporting food are minimised.

“This co-operative has reduced waste collection expenses by 30,000 roubles per year. That means every month we recycle 500 kilos of household rubbish right here without taking it anywhere. If every building and family in the city did the same imagine how much cleaner the big cities like ours would be.” Invw Alla Sokol, community member.
Research that has been conducted shows that the potential of rooftop gardening is huge. For example, in just one district (St Petersburg has 12) it is possible to grow 2000 tonnes of vegetables. Institutions such as orphanages, hospitals and schools as well as apartment blocks have participated in creating rooftop gardens in Russia to improve nutrition, increase their food security and contribute to the improvement in local environment and quality of life.

2nd picture below;
Natalya Petrova watering some of the plants that she and other residents of her apartment block at 9 Pulkovskaya Ul. grow on the roof of the apartment building.