There are many ways to define architecture, from the most technical to the most poetic. It uses many aspects within its context: space, program, tectonics, and gesture, which refers to the stroke, the drawing, and the design. Perhaps the quick sketch that comes to mind when talking about gesture is that of shelter: a cut or elevation, with human scale, of vertical enclosures and coverings.
The most common shelter idea involves covering: a plan for protecting living beings from inclement weather and danger, and sealing buildings. The covering fulfills the sealing function and responds to local peculiarities. Currently, diverse construction systems for coverings allow exploring forms, combinations, and materials to achieve the project's objective. Different materials frequently used in construction have distinct characteristics, with advantages and disadvantages, and offer multiple possibilities according to each case's demand.
Ceramic Tiles
The most popular covering in Brazil is ceramic tiles, made of clay. They use the same material as masonry bricks and undergo the same manufacturing process. They are part of the Portuguese colonial heritage and representatives of Brazilian historical architecture. However, they are not restricted to Brazil and respond well to tropical climates.
In general, it is an accessible material and easily found in the construction field, and provides good thermal comfort performance. Supported by wooden structures - which also have a long history in colonial architecture - ceramic tiles remain an example of traditional constructive techniques, but can be mixed with more modern proposals. The blend takes the "ordinary" roof and gives it a more contemporary look, while at the same time highlighting its cost-benefit, along with its biodegradability.
However, ceramic tiles have porosity, a high number of joints in the pieces, and displacement caused by strong winds. Therefore, the locking and fitting process must be given extra attention to prevent tiles from moving or leaving gaps open for leaks inside the building.
Metallic Tiles
Metallic coverings are quite common in construction contexts and allow for larger spans with fewer support structures. Resistant and standardized, they can also be used as vertical enclosures. The variety of uses explores other interior finishes, and roof use also requires less slope and support structures.
Regarding metal tiles, one can count on the high reflection rate to lower the internal temperature, despite the high heat transmission of metal. Metal roof tiles can also be sandwich tiles, in which a blanket of insulating material is used between the sheets, to increase thermoacoustic efficiency.
Zinc treatments can mitigate corrosion and oxidation in steel tiles. For aluminum tiles, the advantage is that the material can be recycled and reused. Being made of metal, this type of covering has the construction speed of metallic structures, but the support beams require specific labor.
Fiber Cement Tiles
In Brazil, fiber cement tiles resemble metal ones, with corrugated or trapezoidal sheets. They can span larger gaps and require more widely spaced support structures. They can also be found in panels or flat tiles. They are low-cost and fire-resistant, can be used for vertical sealing, are lighter than ceramic tiles, and save labor costs and installation time. However, their thermal performance is lacking and their composition is controversial.
Fiber cement is a mixture of synthetic fibers and cement. One of its components is asbestos, which is harmful to health. Although some manufacturers claim they use low amounts of asbestos in their fibers, others are replacing them. In recent years, countries in the global South have started to ban its production and use, while wealthier countries have already banned asbestos from domestic consumption products — although they still export it to poorer countries. Part of the demand for global reparations also revolves around these aspects.
Straw
In addition to referencing Brazilian vernacular architecture — which can be described as traditional and imposed by the Portuguese — straw roofs are also common in Asian countries and represent an environmentally clean material for roofs. The raw material is natural and biodegradable, so its disposal impact is almost nil. The lightness of the fibers and leaves requires less supporting structure, and the malleability of the material allows for more organic forms and greater formal exploration in construction.
The roof assembly follows simple principles: tying the leaves and overlapping layers on the structure. However, the process is manual and meticulous, involving longer construction time and specialized labor. In addition, straw requires more care than fire, and as an organic material, maintenance must be more frequent than with industrially produced materials.
For each type of mentioned roof, and many others available and yet to be discovered, there are limitations and possibilities, advantages and disadvantages. The architectural shelter depends on its upper closure, and each project requires its type of roof.
