The roofing structure must ensure that the upper portion of the building is watertight, while it must also, within safety conditions, take over the vertical and horizontal weight loads it is subjected to and transfer them onto the support beams. The structure of the cover includes hydro-insulation materials which protect the construction against harsh weather conditions, as the cover is directly exposed to the latter. In the case of covers, one of the most commonly used materials is metal, the roof elements coming in different shapes and compositions.
The framework constitutes the skeletal support structure of the roof. Via its support elements, the framework takes over and transfers the weight load to other construction elements that in turn support it. This framework can be built from wood or metal materials, as well as reinforced concrete.
Metal roofs also serve a different aesthetic purpose in comparison with other types of roofing. Nevertheless, it should fit in harmoniously with the architectural design of the building, as well as the complex it is housed in, be it residential, cultural or industrial.
The metal roof system must also have an adequate shape, so that it easily ensures the removal of water resulting from rain or snow, which must quickly drain from the cover, moving towards its outer extremities, most commonly in eaves, where from it is later carried away from the building through drainpipes or other drainage systems. In order to achieve this purpose, roofs include flat or curved surfaces which present with a certain gradient compared to the horizontal plane. This slope bears the name of roof pitch.
The pitch of the roof is decided according to architectural, economic and climate aspects and the nature of the material from which it is made. From an architectural perspective, a pitch is determined so as to best suit the style of the building. From an economic standpoint, a gentler pitch is recommended so as to minimize the surface of the covering system as much as possible. Generally, the roof pitch is proportionally steeper when the outer layer is more water-permeable. Furthermore, the pitch also depends on the number of joints and construction execution. The pitch of a roof is measured in centimeters per meter.
The roof of a building consists of a series of geometric elements and main parts, such as: the ridge, eave, drip edge, edges, valleys, dormers and skylights.
Let us make a brief description of each main element. As such, the ridge or roof-tree is a horizontal line resulting from the intersection of the upper section of two joining slopes of the roof. The eave is the section overhanging the walls of the building, which allows for the drainage of water from the roof. The drip edge is a strip on the edge of the eave, situated on the lowermost section of the roof.
Roof edges and valleys are sloped strips resulting from the intersection of two roof sides. The latter differ from edges as it is in valleys that water collected from the two adjacent sides gathers and drains away.
The dormer is a structural element that protrudes from the plane of a sloping roof surface and has an opening to allow for air to come in. A skylight is a small window situated in the roof, which allows for light and air to circulate in an attic or loft. At times, it can also ease access from the inside of the building onto the roof.