List of commercially available roofing materials
Roofing material is the outermost layer on the roof of a building, sometimes self-supporting, but generally supported by an underlying structure. A building's roofing material provides shelter from the natural elements. The outer layer of a roof shows great variation dependent upon availability of material, and the nature of the supporting structure. Those types of roofing material which are commercially available range from natural products such as thatch and slate to commercially produced products such as tiles and polycarbonate sheeting. Roofing materials may be placed on top of a secondary water-resistant  material called underlayment. Steep Slope Roofing Materials. Steep Roof Materials are roofs that are only recommended where water can freely and openly drain off the edge of the roof without retaining water for too long. The aim is to drain off water completely due to the high water permeability of most of these materials, for instance: the Thatched roofs. In areas where the International Build Code or similar is utilized, the minimum slope required is 2:12, though some countries extend this as high as 4:12 Thatch. Thatch roofing is typically made of plant stalks in overlapping layers. Shingle. 'Shingles" is  the generic term for an individual roofing unit that is applied with other such units in an overlapping fashion. Slate roofs. While slates have high cost, they have a life expectancy of 80 to 400 years. See the article slate industry for an overview including names of quarries. Some of the famous quarries where the highest quality slate comes from that are available in Australia are Bethesda in Wales and areas of Spain. Ceramic tile. Tile roofing traditionally consists of locally available materials such as clay, granite, terracotta or slate, though many modern applications contain concrete. Metal roofing. Metal roofing  is any of a large variety of roof coverings made from metal and is characterized by its high resistance, impermeability, and longevity. While there are an infinite variety of how to produce metal roofing, thicknesses, and types for metal/finishes used, roofing is generally grouped into 2 categories: Exposed Fastener Panels and Hidden Fastener Panels. Exposed Fastener panels are held down by fasteners through the outside of the metal, whereas Hidden Fastener Panels are held by hidden fasteners, clips, and sometimes adhesives. Typical metals include Galvanized Steel, Galvalume, Aluminum, Copper, or Vinyl 9Which while not metal is included in many  cases for its matching profiles). Low Slope Roofing Materials. Low Slope Materials include roofing materials that can be installed at below 2:12 slope, although in the majority of cases low slope materials can also be installed at steeper slopes. Membrane roofing. Membrane roofing consists of large sheets, generally fused in some way at the joints to form a continuous surface. Modified bitumen. Modified Bitumen are long rolls of asphalt-based materials, that can be heat-welded, self-adhering asphalt-adhered, or installed with adhesive. Asphalt is mixed with polymers such as APP or SBS, then applied to fiberglass and/or polyester  mat, seams sealed by locally melting the asphalt with heat, hot mopping of asphalt, or adhesive. Lends itself well to most applications. Built-up roof membrane (BUR). Built-Up Roofs consist of multiple plies of bitumen-coated organic felt, polyester felt, or coated fiberglass felts. Three to five plies of felt are laminated to each other and to the substrate with hot asphalt, coal tar pitch, or made-for-purpose cold adhesive. Although the roof membrane can be left bare, it is typically covered with a thick flood coat of the bituminous adhesive and covered with gravel, mineral granules, or  a reflective coating, each of which protects the BUR from ultraviolet (UV) light degradation (UV causes evaporation of tar and oxidation of asphalt). Gravel not only provides UV protection, it also helps accommodate sudden temperature changes (thermal shock), protects the surface from hail and mechanical damage, and increases the weight of the roof system to resist wind blow-off. Concrete or fibre cement. Concrete roofing is composed of concrete reinforced with fibers of some sort.