Roofing in Australia

Australia's roofs today are dominated by two families of material: sheet steel, descended from the corrugated iron that arrived in the colonial period, and tiles of terracotta or concrete. Behind them lies a much longer history of Aboriginal shelters roofed with bark, branches, grass and, in parts of south-west Victoria, earth or reeds over stone walls. The country's climates range from tropical cyclone regions in the north to temperate southern cities, and heat, bushfire and hail are recurring hazards for any roof.

Climate and hazards

Northern coasts lie in the tropical cyclone belt, so roofs there need tested fixings and continuous tie-down from sheeting to foundations. Across much of the south and east, bushfire is the defining hazard: the February 2009 Victorian bushfires destroyed more than 2,000 houses, and construction in bushfire-prone areas must now follow AS 3959 according to the site's Bushfire Attack Level. The 2019-20 Black Summer fires also burned through heritage landscapes such as Budj Bim. Hail is a major cause of insurance claims in eastern cities, and strong summer heat drives interest in light-coloured and well-ventilated roofs.

Roofing history

Aboriginal shelters. Shelters known by many names, including humpy, gunyah, wurley, mia-mia and wiltija, were built from bark, branches, leaves and grass, often as lean-tos braced against a tree. Researcher Paul Memmott has found that many Aboriginal huts were dome structures, and designs varied with climate and family size; in the rainforest near Cairns, domed villages were occupied for up to a year through the wet season. On the Dampier Archipelago in Western Australia, circular stone house foundations have been dated to about 9,000 years ago.

Budj Bim. In Gunditjmara country in south-west Victoria, Europeans recorded beehive-shaped domed houses with basalt walls in 1840, often in groups of 20 to 30. Remnants of at least 146 stone houses are known at Budj Bim. Accounts differ on the roofing: one source describes reed roofs, another domes of earth or sod over walls more than 1 m (3 ft) high. The surrounding eel aquaculture system, dated to at least 6,500 years, was inscribed on the UNESCO World Heritage List in 2019. See Budj Bim stone houses.

Early colonial roofs (from 1788). Settlers learned from Aboriginal people which trees gave good roofing bark and how to keep it flat by soaking it in salt water or smoking it. Stringybark and box sheets were laid over sapling rafters and tied with kurrajong-bark cord, and bark roofs usually had no gutters because their edges were ragged. Thatch of cumbungi rushes or blady grass was used where available, and straw once crops were grown. For more permanent houses, shingles were split with a froe, most commonly from box, from stringybark in Victoria, and from she-oak (Casuarina) and other species elsewhere. British-sized slates and imported felts were used on better buildings.

Iron and tiles. Corrugated galvanised iron became common from the 1840s, was often laid straight over old shingles, and remains part of the national identity; galvanised iron gutters became common in the 1850s. Marseille-pattern terracotta tiles were imported by 1886, and large-scale local production by the Wunderlich company began in 1916. Terracotta and concrete tiles became the standard roof of 20th-century suburban brick-veneer houses. Asbestos-cement sheet ("fibro") was used extensively, with James Hardie dominating production until the mid-1980s; it is now banned, and some states prohibit pressure-washing old fibro roofs. The first coil of prepainted Colorbond steel came off the line at Port Kembla in 1966.

Traditional and vernacular roofs

• Bark and slab huts of the colonial frontier (about 1790-1920), roofed with bark, thatch or shingles and later with iron.
• The Queenslander, a timber house on stumps with verandahs and a steep corrugated iron roof, developed from the 1840s.
• Aboriginal domed and lean-to shelters (see gunyah), whose forms and names varied across hundreds of language groups.

Roofing today

Coated steel sheet and terracotta or concrete tile remain the main coverings. Australians still say "corrugated iron" although the sheet is steel, now usually with a zinc-aluminium coating sold under names such as Zincalume. Green and cool roofs have been promoted since 2008 in Melbourne, where early examples include Freshwater Place (2002) and Council House 2 (2006).

Codes, standards and regulation

The National Construction Code, published by the Australian Building Codes Board, sets nationwide requirements and calls up Australian Standards such as AS/NZS 1170.2 (wind actions), AS 1562.1 (sheet roof and wall cladding), AS 2050 (installation of roof tiles) and AS 3959 (bushfire-prone areas). Licensing of roofers and roof plumbers is handled by each state and territory. Falls are controlled under harmonised work health and safety laws (see Australian WHS roof work).

Industry

BlueScope makes Colorbond and Zincalume steel, with its paint line at Port Kembla, New South Wales. Wunderlich was the pioneer of local tile manufacture. Master Builders Australia, a federation of eight state and territory associations, represents builders and many roofing contractors.

Notable roofs

• Sydney Opera House (opened 1973; World Heritage 2007): Jørn Utzon's shells are built from 2,194 precast concrete sections and clad with 1,056,006 glossy-white and matte-cream tiles, 120 mm (4.7 in) square, made by Höganäs of Sweden and fixed in prefabricated panels.
• Budj Bim Cultural Landscape (World Heritage 2019), with its stone house remains.

Local roofing terms

• Corro / custom orb: classic corrugated profile.
• Fibro: asbestos-cement (now fibre-cement) sheet.
• Humpy, gunyah, wurley, mia-mia, wiltija: Aboriginal shelter names from different languages.

Sources and gaps

Reliable national statistics on roof-material shares were not found; the ABS census does not appear to publish them.