The roof is the uppermost structural element of buildings, which serves to protect them from atmospheric precipitation. Another main function of roofs is the thermal insulation of the structure, i.e. heat retention and overheating protection.
General concepts
For industrial facilities or non-attic structures (also called combined), that is, elements that are at the same time overlapping, the term "covering" is often used.
More generally speaking, the main types of coatings include large-span flat, non-attic, as well as spatial structures.
The roof must first be calculated for the perception of loads arising during its operation.Permanent - from its own mass, as well as temporary - the weight of the snow cover and wind pressure.
Roof cladding that is exposed to the external environment is called roofing. It should have the properties of water resistance and moisture resistance, not be afraid of chemically aggressive substances, ultraviolet radiation from the sun and temperature changes.
The main desired advantages of the roof are durability, lightness, aesthetic appearance, cost-effectiveness during installation and operation.
The design of the roof and the selection of material for the roof are determined during the design, and depend on the design of the building and the roofing technology.
flat covers
Such a design usually has a slight slope so that rain and melt water flows freely from the roof, which does not exceed 5º. Such coatings, as a rule, do not have an attic.
A flat roof can be terraced (operated) and non-exploited.
The first type is used to create summer cafes, playgrounds, outdoor pools and cinemas, sports and helipads, etc.
Also, the free space of such coatings can be planted with vegetation, winter gardens and greenhouses can be laid out on them. Such structures are called "green roofs".
Unlike roofs with slopes, on flat counterparts, sheet and piece materials are almost never used as cladding. They need rolled panels that form a continuous carpet: bitumen, polymer-bitumen and polymer finish coatings, as well as various mastics.
Note! Such a carpet should have elasticity to such an extent that it can easily perceive mechanical and thermal deformations of the base.As such, load-bearing boards, solid wood flooring, screed, thermal insulation surface can be used.
Attic (pitched) structures
The most common in domestic construction are various types of inclined, i.e. pitched roofs.
Their design consists of inclined planes, which are called slopes, their basis is support rafters and a crate. The bottom of the rafter legs usually rests on Mauerlat bars, which redistribute the load from the entire system.
Mauerlat is mounted on the upper inner edge of the outer walls. The intersection of the ramps creates slanted vertical and horizontal ribs. The upper horizontal rib, to which the upper parts of the rafters are attached, is called the ridge.
The intersections of the slopes, creating incoming corners, form grooves and valleys. The ends of the roof, protruding horizontally beyond the outer walls of buildings, are called cornice overhangs. Obliquely located - gable overhangs. The roof also has cornices, gables and dormer windows.
Modern pitched roofs are complex structures consisting of many elements: a wind barrier, vapor and waterproofing films, thermal insulation, and external cladding.
It should be borne in mind that a properly equipped roof should also provide good ventilation between the rafter system and the finish coating.
Forms of attic roofs
Inclined roofs differ in configuration and number of slopes.
In shed roofs, their supporting structure, consisting of a rafter system, rests on external load-bearing walls that have different heights. They are most often used in the construction of terraces, verandas, warehouses and outbuildings.
A gable (gable) roof is the most traditional and common design.Its basis can be either a hanging truss truss or layered rafters.
Variations of this type include systems that have a uniform or uneven slope of the slopes or the size of the cornice overhangs.
For hipped roofs, all four slopes look like isosceles triangles and converge at the top at one point. The defining moment in this case is their symmetry. Used for buildings that have the shape of a square or an equilateral polygon.
The hip hipped roof has two slopes, which are trapeziums, the other two, at the ends are triangular (these are the hips). Varieties of this design are half-hip, as well as Danish, a mixture of gable and hip roofs.
In half-hip roofs, the end slopes are cut off and have a shorter length along the slope than the facade slopes. They are usually used in regions where there are strong wind loads and gables need to be protected from them.
Multi-gable structures are installed on buildings that have a complex polygonal configuration in terms of plan. They have a greater number of internal corners (valleys), as well as ribs (protruding corners formed by the intersection of slopes).
A conical or domed roof is used for buildings that have a circular shape in plan.
truss system
Rafters are the supporting system of pitched roofs. They consist of rafter legs, located obliquely, vertically placed racks and obliquely mounted struts. As necessary, they can be connected from below with horizontal rafters. Rafter systems are divided into hanging and layered.
When the roof is being built, the layered structure rests with its ends on the walls and partitions of the building, and in the middle, if the span is more than 4.5 m, on additional supports.
The arrangement of the intermediate beam makes it possible to increase the width that the rafters cover up to 12m, and the two supports - up to 15m.
Hanging rafters rest with their ends only on the walls. This system is selected if the distance between the outer walls is no more than 6.5m.
The rafters are attached:
- In wooden log and block structures on their upper crowns;
- In frame buildings - on the upper trim;
- In brick, block, stone buildings - on the Mauerlat, which has a thickness of 14 / 16 cm.
The support beam can be mounted along the entire length of the house or placed only under the rafter leg.
Note! When the legs in the section have a small width, they sag over time. To prevent this, you need to make a special lattice, which includes a rack, struts and a crossbar. For this, boards with a cross section of 15 × 2.5 cm are used.
To fix the rafter legs, a puff is used that connects their lower sides. If the end of the rafter slides along the puff, he is able to destroy it.
To prevent this from happening, when the roof is being made, it is necessary to cut the leg into the puff with a spike, a tooth, or both of them at the same time. In addition, it is recommended to place the rafters at a distance of about 30/40 cm from the edge.
Russian building codes
The norms and rules regarding the construction of roof structures are spelled out in a variety of documents. Some of them are morally obsolete, however, have not yet been canceled.
Design should be carried out taking into account the instructions and restrictions of the current standards:
- SP No. 17.13330.2011: "Roofs";
- SNiP No. 2.08.02-89: "Public buildings and structures";
- SNiP No. 2.09.04-87 "Administrative and amenity buildings";
- SNiP No. 31-03-2001: "Industrial buildings";
- SNiP No. II-3-79: "Construction heat engineering";
- SNiP No. 3.04.01-87: "Insulating and finishing coatings";
- SNiP No. 21-01-97: "Fire safety of buildings and structures";
- SP No. 31-116-2006 "Design and arrangement of sheet metal roofs"
And, finally, one of the main documents according to which the roof should be designed: SNiP No. 2.08.01-89: “Residential buildings”.
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