When you equip a hipped roof with your own hands, it must have not only stability, strength, fire resistance and provide reliable protection from environmental influences. Its respectable appearance, individuality and expressiveness are also important, in other words, the design of the roof.
A roof of this type during its installation requires good skills and work experience, because its truss system is quite complex.
About the varieties of hipped roofs
Four-pitched roofs are divided into several main varieties.
Hip roof structure By the very sight they emphasize their protective functions. They are formed by two trapezoidal facade planes - a slope and two triangular end planes.
Such roofs do not have gables; attic windows are made right in their slopes. Triangular planes are called hips.
Since there are no gables, such a roof is more economical than a gable roof in terms of the cost of wall building materials. However, the inclined ribs at the junction of the hips and frontal slopes require the installation of complex rafters, as well as additional fitting of roofing materials.
In other words hip roof truss system - one of the hardest.
The slopes, having different levels of inclination, create a hipped sloping roof.
The mansard hip roof has broken slopes, which can be supplemented above the facades with triangular small hips.
The semi-hip (Danish) roof has a pediment, like a gable roof, which is crowned with a small hip on top. It is protected by a gable roof ridge from increased wind loads. Therefore, most often, such a four-pitched roof device is used in regions in which strong winds constantly blow.
Constructions do-it-yourself hipped roof essentially pyramidal: their four slopes of a triangular shape converge with their tops in one place. Such roofs also do not have gables and are used for small buildings that have the shape of an equilateral polygon or square. The disadvantage of the design is the complexity of installing the truss system.
Design and calculations
Before starting work on the arrangement of the roof, it is necessary to design it and carry out the calculation of the future structure, as well as make a drawing of a hipped roof.
The slope of the slopes of such a roof can vary from 5º to 60º and depends on atmospheric loads, the purpose of the attic and the type of roofing material.
Note! In areas where strong winds are frequent, or the climate suggests a small amount of precipitation, the slope of the roof is made small. With significant snow loads and frequent rains, the slope of the slopes should be significant - from 45º to 60º.
The angle of inclination also affects the choice of material for the roof. If it is 5/18º, then a roll coating is recommended, asbestos-cement sheets, roofing metal dictate a slope of 14/60 °, if the roof is tiled, it should be 30/60 °.
The height of the roof ridge with the slope of the slopes you have chosen can be calculated by the trigonometric expression for right triangles.
They begin to draw up projects for houses with a hipped roof with the calculation of rafters. Their cross section is determined, depending on the totality of the expected loads (weight of the truss structure, roof pie, wind and snow loads), as well as the degree of roof slope.
In this case, the margin of safety of the rafters should be at least 1.4. Calculations also determine the step between the rafters, help to check their bearing capacity.
During the design, it is decided which roof rafters to use - layered or hanging.It turns out whether there is a need for additional elements: braces, which make it possible to reduce the load on the rafters, or puffs that prevent loosening of the structure.
If it turns out that the standard dimensions of lumber are not suitable for your future roof, then its project determines the measures for changing them. For example, you can increase the length of the rafters, or double the beams and thereby strengthen them. There is the possibility of using glued (type-setting) rafter legs - they are both more powerful and longer than usual.
Loads on the truss system
The rafters are affected by both permanent and temporary loads. The first of these is the mass of the roof, counter-battens, battens, rafters and girders. The second are wind, snow, and payloads.
The design parameter of snow loads for the Central Strip of the Russian Federation according to SNiP 2.01.07-85 is 180 kg / m² (horizontal projection of the roof). The accumulated snow bag is able to increase this value up to 400/450kg/m².
If the roof slope exceeds 60°, then the snow load is not taken into account in the calculations.
The calculated value of wind loads for the same central strip of Russia is 35 kg / m². When a four-pitched roof with a slope of less than 30º is designed, the drawing does not take into account its correction for the wind.
The parameters of the loads described can be adjusted by means of correction factors, taking into account local climate conditions. The total mass of the roof is calculated based on the materials used and the area of \u200b\u200bthe structure.
The payload on the rafter system is included in the calculations if ceilings are suspended from the trusses, hot water tanks, ventilation chambers, etc. are installed.
Note! When designing a truss system, two calculations are made. The first one is its strength. He must ensure that the rafters do not break. The second finds out the degree of their deformation at the chosen parameters. For example, for mansard roofs, the deflection of the rafters should not be more than 1/250 of their length.
Now, as rafters, most developers use either a rectangular beam, which has a section corresponding to the calculated loads, or boards with a section of 5 × 15, 5 × 20 cm, rallying them as necessary.
Coniferous lumber is mainly used - spruce, pine, larch, which do not have defects, with moisture indicators not exceeding 18/22%.
To increase the rigidity and invariance of the geometry of the truss system, when a multi-pitched roof is made, steel elements are introduced in its individual sections.
For example - as supports for the most loaded skate runs. The spans between metal parts are filled with wooden elements. Such combined structures are not only more durable than fully wooden ones, but also enable the rafters to function using non-thrust-layer technology.
Installation of the truss system
The rafter system of hipped roofs consists of rafters, support bars, braces, and other elements necessary to stiffen the structure.
The rafters must have a cross section of 5 × 15 cm, this will give the reliability of the assembled structure. When purchasing lumber for rafters, do not take wet, twisted and seriously flawed.
The roof is installed from the bottom up. First, the support beams (Mauerlat) are laid on which the rafters will be installed.
Thus, you will get the bottom frame.Be sure to check the correct installation of the beams with a building level. The lower frame should extend beyond the plane of the walls of the building by 40/50 cm.
If the building has wooden walls, then there is no need for support beams, because, as the role of the Mauerlat, the upper of the crowns of the log house (beam or log) will play.
Then, from each corner, the main frame rafter legs are placed, they are called oblique or diagonal. The upper sides of the rafter legs, if necessary, can be supported by a system of braces and racks.
Their task, when multi-pitched roofs are being built, is to unload the rafters by redistributing the loads on the internal walls or supporting pillars, and in addition, to stiffen the structure.
In places where there are no load-bearing walls, the heels of the rafters can be supported on longitudinal beams, called side girders, their length is limited by the load acting on them.
In addition, the beam is mounted in the center, it is placed on three supports: in the middle and on both sides.
It is the height of the rafters, as well as the horizontal upper beam (ridge run) that determine the height parameters and the degree of slope of the roof.
After the guide rafters are installed, you can start building the main frame. Inclined rafters, called outdoor rafters, are attached to the support beams and to the ridge run.
Install them in increments of 40 / 50 cm, it is no longer desirable, because the gaps will be too large and the rafter system may one day not withstand the loads from the precipitation that has fallen in the winter.
When a hipped roof is made, it should be about one meter from the upper rafter to fasten the inclined rafters together.
You can do this with the help of boards with a section of at least 4 × 12 cm. This operation is necessary to give the structure additional rigidity so that the roof can easily withstand wind loads and unwanted vibrations are not created.
It is not necessary to select outdoor rafters along the length, they will still be cut off, the main thing is that they are not shorter.
When you make a hipped roof with your own hands, do not save nails, remember that the structure is constantly subjected to one or another load, therefore it must be extremely reliable.
When the frame is assembled, you can start building the roof pie.
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