With all the essentials of your roof garden design dealt with – ie. ensuring the surface of the roof is stable and strong, water supply, lighting, etc, you can concentrate on the trimmings.
Walls can be trellised or painted in jolly or sophisticated colors, while those of you handy with a brush can let your fancy rip. You could turn a chimney stack into a Gothick folly or a ruined Doric column; paint a romantic landscape, a luscious jungle or, if you are not so talented, you could surely manage a naïve simplicity. Even the most cack-handed could probably draw and paint a couple of lollypop trees in tubs, an unashamedly-unlikely flower, and a smiling sun in a blue sky, which could cheer things up no end.
The smallest rooftop garden or balcony can be apparently doubled in size by a mirror or two, artfully placed and disguised. Quite small pieces of the mirror can be fitted like window panes into a false door or window frame, which would appear to open on to yet another garden beyond, whilst larger pieces, from wardrobe doors or stripped-out bathrooms, shops, and restaurants, can be used to back an archway or a wrought-iron gate. The glazier will cut them to shape if you wish, but you could just cut out your arch from plywood off-cuts and fit these over the glass, along with any ‘glazing bars’ of wooden molding stuck on with strong glue.
Simple roof garden design ideas are often the most effective, and you can paint your arch, door, window, grille, or whatever, directly onto the glass. As always, the mirrors must be set at a very slight angle so that they reflect, not the onlooker but another part of the roof garden or another mirror, in which case, the illusion of space will be, appropriately enough, limitless. The glass should be backed with foil-covered hardboard and then should be stuck to a piece of plywood with a suitable glue that your glazier will supply. It is a good idea to run around the bare edges of the glass with bath sealant which comes in a plastic tube. Any form of coping, porch, or pediment will help to protect the glass. I know that the whole idea seems a bit ‘twee’, but when well done it can look marvelous, and the artifice is acceptable on the roof.
Water is just as desirable on a rooftop garden as elsewhere in a ground-level garden. Bearing in mind its weight, position it carefully, deciding as usual between still water with fish and plants, or moving water, whether a small jet fountain or something bubbling and trickling gently. With a jet fountain, remember that the winds up on the roof are capable of carrying the plume of water over a considerable area, which could cause annoyance to your neighbors or actual damage to their property, so make sure that any jet of water is small enough to be contained within your boundaries, no matter how sportive the wind.
The same care will have to be exercised when watering the rooftop garden by hose or sprinkler. As the roof is strongest at its edges, it may well be that a wall fountain will be the answer for you, but your rooftop garden pool can also be made in most garden containers, and it is important to choose the lightest ones whenever possible unless you have a very strong roof.
Because extreme heat can be as much a problem as the wind, some kind of shade would be a welcome addition to the amenities.
A cheap beach umbrella will do well enough if you stick to the plainest colors or stripes, rather than some overblown floral print which will make you feel dizzy – the last thing you want in this airy oasis. Sun blinds of canvas or split-cane can also be used, propped up and out on some upright posts.
Roof Garden Design Ideas
A simple pergola of timber would be easy enough to make, and if you are really hopeless at carpentry, unable to screw or nail two bits of wood together, there are some useful little metal joints that you can buy, made by the same people who make metal fence posts. Into these, you can just push the ends of the timber. The joints come in various kinds so that you should be able to find some to suit your design.
Make sure that you measure up carefully and cut your timber (or get the timber merchant to do it for you if you are buying new wood) inappropriate lengths; what could be simpler? If there is no suitable surface on which to secure the uprights, treat the bottom of the posts with an extra coat or two of preservative and sink each post into a container of soil, into which you can also pop a climber plant which will grow up and round the post, and over the pergola in a great way.
Alternatively, you could fix two horizontal bars between adjoining walls or chimney stacks; to these, you fix cross-bars of timber thus forming your pergola, which is an even easier solution: If high-tech is your sort of thing, you could use lengths of scaffold poles or old iron piping to form your uprights, to which you would fix lengths of planking, more piping or rope.