Roof Gardening, Roof Garden Design and Balcony Gardening
Balcony Gardening / Roof Gardening
The basic principles are the same for both balcony gardening and roof gardening. It will be essential to find out if the existing structures are sound and strong enough to take the weight of whatever you plan to install thereon. So, do not be tempted to take chances over this, but get professional advice from an architect, surveyor or competent builder.
No matter how light your compost and your container may be initially, once the compost is wet it can become very heavy indeed. Remember that 4.5 litres (1 gallon) of water weigh about 4.5kg (10lbs), and that a container large enough to take a small tree or a large shrub may take at least 9 litres (2 gallons) of water a day, so you can see how quickly the weight can mount up.
Spreading the Load on Your Roof Garden Design
If you move into your house when it is being ripped apart or renovated, it will not be too difficult to have the roof strengthened at this stage. Later on there are still ways of beefing things up a bit, but this is not for the amateur. However, remember that the roof will be strongest at its edges and over any joists, so concentrate your planting, etc., there. Spreading the load on a roof garden helps a bit, too, so some form of decking would be effective, either over the entire roof or under groups of containers.
The surface of the roof garden is important. If it is concrete or tiled, you are in luck as it will take a lot of traffic and provide a good surface for whatever you put up there, but frequently the flat roof is lead, or asphalt, and this is often scattered with gravel chippings which look sturdy enough, like a gravel path, but in hot weather, when the asphalt softens, any sharp or weighty object placed on it, or heavy traffic across it, will push the gravel down through the asphalt making holes which will leak, causing endless problems with damp.
Unless you can remove the gravel, and tile the roof instead, it would be wise to cover the whole area with decking which you can make simply enough from timber or wooden battens, which will have to be treated with a preservative. This is not too expensive a solution and gives the roof garden design the added advantage of potentially having the decks made at various levels to give more interest to what is usually rather a boring flatness.
A roof garden is one of the few places in which I would consider using Astro-turf. Because a sky-high garden is, in itself, an artificial conceit, such outright imitation is acceptable, I think. It is also a remarkably comfortable solution to the extremes of hot and cold found in such situations. On sunny days, the roof can become unbearably hot, whilst in damp or icy weather, it can be chilly or dangerously slippery.
Astro-turf insulates you from either of these excesses, is very easy to maintain and pleasant to the touch, ideal for sunbathers, in fact – but also makes roof gardening a whole lot easier.
If your roof is strong enough and you are prepared for hours of roof gardening maintenance , there is nothing to stop you having a real lawn up there, but I personally advise against it. The turf, being of necessity on a thin layer of, will dry out at an alarming rate in fine weather, and the thought of trotting up and down with a lawn mower with the pigeons is distinctly unnerving.
Whatever surface you choose, it is essential to make efficient provision for . Of necessity, the roof will already have, one hopes, its own adequate drainage system, so your main concern will be not to obstruct, overload or choke this in any way. It is a good idea to fit some kind of protection, such as a sediment trap, or a cover of perforated zinc or crumpled chicken-wire, over all drainage outlets, so that they do not become clogged by dead leaves and other garden gunge.
It is also worth installing something which will help to prevent the compost from being washed out of the containers on the roof, for not only would the seepage cause staining to the roof surfaces but it could lead to the formation of mosses and algal growth which would make the roof a dangerous place for the unwary or unsteady on their feet.
The subject ofleads me to the water supply. I know however, that it should, logically, be the other way round. On the roof, above all, install an outdoor tap and a wall-mounted hose, if you are contemplating anything more than one geranium and a pot of basil. The initial outlay will be amply repaid by the survival rate of the plants. Balcony gardening, whilst it obviously will require a water supply also, it generally is much easier to ferry cans of water to and from the kitchen tap.
Good intentions are one thing, but actions are another. At the end of a long, hot and tiring day, even the most dedicated may flop guiltily into the nearest chair rather than face the prospect of trailing round the roof with can after can of water. If you cannot get an outside tap fitted for your roof gardening requirements, you can always fix up a primitive irrigation system by perforating an old length of hose which can be connected easily to the nearest tap. It will lead, inevitably, to a messy puddle at the tap end, as I have yet to find a really waterproof connection, but your plants may survive.
Should the roof be up to it, a water-butt or cistern would be a help. It could be filled by the winter rains and topped up by an occasional session with the hose. It might even be possible to channel water from surrounding roofs into your personal reservoir. A barrel would be pleasant-looking, but an old water tank of galvanised metal or plastic would be quite serviceable, and the latter could be given a ‘hide’. From these tanks you can fill your cans in a comparatively painless fashion and the plants will appreciate the tepid water. You will often find water tanks on skips and your plumber would probably be able to obtain one for you. Failing this, any watertight container, the larger the better, that you can get up onto the roof will do.
Talking of which, if access to your lofty plot is limited, it is usually possible to fix up a Jenny-wheel, which is a sort of rope and pulley on a scaffolding-pole, with which you can haul up all that you need. These can be hired quite easily and cheaply, or a friendly builder might lend you one. Really ambitious roof gardening fans have hired cranes to swing a container-load of mature trees and exotic ‘features’ up on to their eyries, but I cannot pretend that this is an economical proposition unless you are on extremely intimate terms with the crane-driver.
But back to the water tank. Give them a disguise of some kind; perhaps a screen of light timber with a generously proportioned evergreen plant, strategically placed in front of it. Anything you can do to make watering easy and enjoyable will be time and money well spent. All container-grown plants need full and regular watering, but those on a roof will need even more attention as they are particularly exposed to both sun and wind which can be equally desiccating, a point which this will,be, overlooked.
Lighting for Roof Gardening
Lighting is an important addition to roof gardening life; it will both prolong and enhance the time you spend up there and be an additional safety factor. Any electrical fittings will need to be installed by a competent electrician, using special cables and connections. One or two spot-lights, whether uppers or downers, will have the most dramatic effect. However, all sorts of oil lamps and candle lanterns can provide perfectly adequate and absolutely charming effects. A string of candle lanterns, strung across the roof, above the heads of its inhabitants, and some artfully placed jam-jars containing night lights or more candles, can all be used to add some mystery and magic.