One of the most characteristic elements of the 19th century Australian worker’s cottage is its roof. Steeply pitched with short spans and therefore low and compact in form, it is perfectly in keeping with the modest volumes it shelters. There are two basic types: either a parallel series of hipped or gabled units, themselves parallel to the street and separated by box gutters; or a U-shaped hipped roof, whose form is not immediately apparent when viewed from the front and sides, but becomes clear when viewed from the back: a box gutter, perpendicular to the street, runs down the middle of the house, separating the two hipped (or occasionally gabled) roofs that form the uprights of the ‘U’.
One explanation given for the emergence of these forms is that the unsophisticated colonial builders had a poor understanding of structural principles: the ceiling joists weren’t tied to the rafters to form a primitive triangulated truss and prevent the rafters from spreading the walls, and so the thrust exerted on the walls by the roof could only be controlled by keeping the span of the roof, and thus its mass, to a minimum. Low roofs with simple rise:run ratios such as 1:1 (45 degrees) or 1:1.3 (a 3-4-5 triangle, 37 degrees) were also easier to construct and required only short rafters.
Aside from these practical and material factors, early builders also no doubt had their aesthetic motivations, and understood very well that low, steep roofs suit these humble cottages perfectly and give them their unique appeal.