In simple terms, a 'Pergola' is a series of cross-beams placed over columns. It is an aesthetic feature, as well as provides a certain amount of shade below it. In Modern Kerala House Design, we see many balconies and porches covered with a pergola over it as an interesting elevational feature.
'Pergola' is an Italian word that means- 'extended roof'. In olden days, they were used as garden shades and covered with climbing plants, espectially over walkways in parks. Here is a picture of a Park walkway covered with Bougainvillea-
Kerala homes use Pergolas mainly in the balconies and also over internal courtyards. Unlike roofs, Pergolas do not offer protection from rain. Hence, when they are used above interiors, a tempered glass or polycarbonate sheet is provided over it to prevent water from entering inside.
Although they do not offer rain-protection, Pergolas can be used to provide varying degrees of shade below it. 90% of the sun's rays pass through at noon-time, but when the sun is at an angle, the series of beams create shade patterns that block the sun. Pergolas are an excellent feature for roof gardens. Potted plants and lamps can be hooked over it; and garden vines can be grown over it. It offers the much needed sunlight for the garden.