A well designed, and maintained pergola, can be a feature in itself as well as the ideal way to provide some shade in your garden during the hot summer months. It can provide seclusion, and create the ideal place to relax, for kids play, or for you to entertain. Shade is important in the garden both for plants and people. Even the family pets need and appreciate a little shade in the hot Australian summer. With the prevalence of skin cancer in Australia, shade is particularly important to provide protection from this serious disease.
A pergola is a series of beams, slats or roofing supported by poles (a building without any walls just the roof). A pergola may be attached to the house to extend cover over an outdoor area, or be free standing, perhaps as a garden feature or to provide cover along a walkway. Pergolas can be used on the south side of a house to provide cool air in summer. The pergola should be treated with a preservative paint at regular intervals.
Plants may be grown on the overhead beams or slats for decoration, or to increase shade. Deciduous climbers such as grape (Vitis vinifera) or wisteria are often used to increase shade in summer, but allow the light through in winter (when the leaves fall). Hanging baskets can also be hung on the cross beams to give an extra dimension to the garden. Remember that a pergola which supports the weight of a growing plant must be stronger than one which does not. Wooden pergolas may eventually rot and metal pergolas can rust. Be careful if they are covered by plants, such deterioration can go unnoticed, and there is always the danger of the pergola collapsing on someone.
Pergolas are generally very easy to construct. Most home handyman can readily do this. How to build pergola leaflets are generally readily available from major hardware stores. These stores are also an excellent source of advice on what tools and materials are required. Be sure to check with your local council to see if there are any relevant regulations covering the siting or size of such structures in your area, or any regulations covering what materials can or can't be used.
The most common materials used in constructing pergolas are galvanised metal pipe, oregon (e.g. F7 grade), or treated pine (e.g. H4 grade) posts as uprights, and oregon (F7) and treated pine (F7) for the support beams, rafters, battens and braces. Metal and treated pine posts can be concreted directly into the ground, while oregon posts (and treated pine if desired) should be placed on galvanised post supports (or saddles) that have been concreted into the ground. This is to prevent the base of the posts from rotting. Wooden posts generally look better, and are easier to nail into or attach things to. Metal posts are important in areas where white ants are a significant pest.
Covering A Pergola
There are several materials that are commonly used to cover a pergola to provide shade, or protection against the elements. These include the following:
Plastic Sheeting
Materials such as Polycarbonate, PVC, and Acrylics are used extensively on pergola rooves. They can be easily cut to shape, and be attached by the handyperson without requiring expensive tools, and can be lifted safely by two people to the position required, or by one strong person. These sheets come in a variety of styles, shapes and colour. They are more flexible than glass, and can often be bent to shape depending on their thickness. Some have a high block out factor for ultra violet light making them excellent protection for reducing skin cancers, and eye damage. These types of sheeting will trap the heat to some extent, so good ventilation through the pergola is important to keep temperatures down.
Fibreglass Sheeting
This is a fairly popular as a cladding or roofing material. The quality of the fibreglass has the most effect on it's usefulness. Poor quality fibreglass deteriorates quickly and dust and dirt accumulates in the fibres therefore reducing the level of light shining through. Moulds and algae readily grow on this material as it breaks down. UV treated fibreglass will last much longer. PVC and other plastics have to a large degree replaced fibreglass as a cladding material.
Timber
Thin slats of timber placed side by side, with thin gaps between them, will reduce the full impact of the sun. The gaps between the slats provide good ventilation reducing temperature build up, however the gaps also allow the passage of rainfall through, unlike the solid roofing sheets. Also the sunlight passing through the gaps will not have had it's UV component blocked out. The gaps will also provide passage space (and support) for climbing plants, but regular checks should be made to ensure that the slats are not being lifted or damaged.
Shadecloth
This is a woven, durable material, with a life expectancy of around 5-6 years. It is available in a number of colours, with green being the most popular. Shadecloth is available in different strengths, with 50 and 70% shade being common. Shadecloth provides excellent protection against the sun, and good ventilation, but allows the passage of rainfall. Shade cloth can also be used on the sides of pergolas to provide extra protection against sunlight, or to provide protection against prevailing winds. A pergola covered with shade cloth is ideal for growing ferns, azaleas and orchids. It can also be used to grow rainforest plants like gingers, monstera, philodendrons and costus.
Other Materials
These include woven brush (e.g. tea-tree), woven bamboo, wire mesh (unsightly until covered by plants), and canvas (either temporarily during hot weather, or permanently).
Plants
Climbing plants are an ideal way to provide cover on a pergola. Plants release moisture into the atmosphere creating a cooling effect on hot days. Colourful, or scented, flowers and foliage are an added advantage, and may attract birds close by where you can easily watch them. Deciduous climbers can be used to provide summer shade and winter light. Some climbers cause less damage than others, but no matter what you use, you should check for damage every few years, and trim back the climber if need be. Most climbers need something to climb on. You can use materials such as trellis, wire mesh, single wires or nylon strings (not jute that will rot). These can be readily attached to the supports or roof of a pergola.
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