See Article History Roof, covering of the top of a building, serving to protect against rainsnowsunlightwindand extremes of temperature. Roofs have been constructed in a wide variety of forms—flat, pitched, vaulted, domed, or in combinations—as dictated by technical, economic, or aesthetic considerations. Conical thatched roofs are a good example of this type and are still widely used in the rural areas of Africa and elsewhere.
Excavations at a number of sites in Europe dated to before 12, bce show circular rings of stones that are believed to have formed part of such shelters.
They may have braced crude huts made of wooden poles or have weighted down the walls of tents made of animal skins, presumably supported by central poles. A tent illustrates the basic elements of environmental control that are the concern of building construction. The tent creates a membrane to shed rain and snow; cold water on the human skin absorbs body heat.
The membrane reduces wind speed as well; air over the human skin also promotes heat loss. It controls heat transfer by keeping out the hot rays of the sun and confining heated air in cold weather.
It also blocks out light and provides visual privacy. The membrane must be supported against the forces of gravity and wind; a structure is necessary.
Membranes of hides are strong in tension stresses imposed by stretching forcesbut poles must be added to take compression stresses imposed by compacting forces. Indeed, much of the history of building construction is the search for more sophisticated solutions to the same basic problems that the tent was set out to solve.
The tent has continued in use to the present. The agricultural revolutiondated to about 10, bce, gave a major impetus to building construction. People no longer traveled in search of game or followed their herds but stayed in one place to tend their fields.
Dwellings began to be more permanent. Archaeological records are scanty, but in the Middle East are found the remains of whole villages of round dwellings called tholoiwhose walls are made of packed clay ; all traces of roofs have disappeared.
In Europe tholoi were built of dry-laid stone with domed roofs; there are still surviving examples of more recent construction of these beehive structures in the Alps. In later Middle Eastern tholoi a rectangular antechamber or entrance hall appeared, attached to the main circular chamber—the first examples of the rectangular plan form in building.
Still later the circular form was dropped in favour of the rectangle as dwellings were divided into more rooms and more dwellings were placed together in settlements.
The tholoi marked an important step in the search for durability; they were the beginning of masonry construction. Evidence of composite building construction of clay and woodthe so-called wattle-and-daub method, is also found in Europe and the Middle East.
The walls were made of small saplings or reeds, which were easy to cut with stone tools. They were driven into the ground, tied together laterally with vegetable fibres, and then plastered over with wet clay to give added rigidity and weatherproofing.
The roofs have not survived, but the structures were probably covered with crude thatch or bundled reeds. Both round and rectangular forms are found, usually with central hearths. Heavier timber buildings also appeared in Neolithic New Stone Age culturesalthough the difficulties of cutting large trees with stone tools limited the use of sizable timbers to frames.
These frames were usually rectangular in plan, with a central row of columns to support a ridgepole and matching rows of columns along the long walls; rafters were run from the ridgepole to the wall beams.
The lateral stability of the frame was achieved by burying the columns deep in the ground; the ridgepole and rafters were then tied to the columns with vegetable fibres.Jul 11, · The pitch of a roof is the rise—the vertical angle of the roof—over the run (the horizontal measurement).
Pitch ratios range from to A low-pitched roof would be , and it means that over the space of 12 inches, the roof only rises two inches%(37). May 29, · How to Frame a Roof. In this Article: Article Summary Designing the Roof Cutting the Rafters Raising the Rafters Community Q&A Framing a roof is the last step in framing new construction.
While most home builders will outsource the construction of roofing trusses–the rafter supports of the roof itself–learning to frame a roof yourself is one of the true arts of carpentry, and a basic %(8). The type and pitch of the roof is important, some roofs will hold a greater amount of snow therefore resulting in greater loads acting upon the roof.
BS state that kN/m2 extra weighting for a building with a ≤30⁰ roof pitch and kN/m2 extra weighting for a building with a > rood pitch/5(1). Oct 15, · He remarks on some of these variations, before returning to the project house site, where the roof framing is underway. Bryan Readling (from the APA) joins to review the products being used on the roof, including Peel & Seal tape, a joint sealer, and LP TechShield, a reflective sheathing product.
The type and pitch of the roof is important, some roofs will hold a greater amount of snow therefore resulting in greater loads acting upon the roof. BS state that kN/m2 extra weighting for a building with a ≤30⁰ roof pitch and kN/m2 extra weighting for a building with a > rood pitch/5(1).
from Robin T. roof pitch. There are several constraints. a) must be >20 degrees b) should be.