The rafter system of a gable roof, the calculation of the rafter system, the installation of the rafter system, useful tips
The structural element of the structure, designed to protect the entire structure from the effects of rain, wind, heat and frost, is called the roof. In addition, the roof of the original form is one of the most attractive architectural elements, a real decoration of any home. During construction, most owners prefer to put into practice proven, uncomplicated designs that withstand harsh weather conditions. One of these is a gable roof, or gable.
Content:
- Gable roof of the house
- Calculation of the rafter system of a gable roof video
- Gable roof truss calculator video
- Installation of a rafter system of a gable roof video
- Rafters for a gable roof - mounting options
- Installation of the lathing over the old roof video
Gable roof of the house - reliable option
The gable roof is extremely simple in design, it is essentially two planes rigidly fixed at a certain slope to the walls of the structure, it is this position of the slopes that ensures the convergence of wastewater during rainfall, as well as melt water during snow melting.
Traditionally, the angles of the ramps are designed the same, this solution allows the full use of the attic as a utility room or a residential attic. The base of such a roof is an isosceles triangle.
Sometimes, in order to emphasize the originality of architecture, a variant with different slope angles is developed, the skate in this case is shifted towards one of the walls of the structure, the eaves in this case can have different lengths.
If in the future it is planned to equip the attic as a mansard room, they design a broken gable roof, it can significantly increase the volume of the room, this is very important, because some space will be required to install insulation and waterproofing systems.
So that no further questions arise, we immediately specify the meaning of special terms that builders use.
Mauerlat
These are beams made of coniferous material, the cross-section is square, mounted along load-bearing walls, using anchors, threaded rods.
Rafters
They are also a beam, the recommended section size is 15x10 cm, designed to create a triangular roof contour, which should have a solid margin of safety and be able to withstand the loads created by wind, storm flows and snow. The recommended installation frequency of rafters is from 0.6 m to 1.2 m. It is easy to assume. that the distance should decrease as the weight of the roofing material used increases.
Sill
Represents a wooden beam of square section, for example, 10x10 (15x15) cm. It is designed to distribute the loads created by the roof racks, lay the rest along the supporting internal wall.
Puff
Used in the installation of the hanging rafter system, serves to fix the triangle created by the rafter legs.
Racks
A beam of the same cross section is used for them, the racks are installed in an upright position, by means of the racks the load created by the ridge is transferred to the supporting internal wall of the structure.
Struts
They play the role of an auxiliary link, serve to create a strong blood element, which is called a farm and which is obtained by connecting puffs and struts. Properly assembled trusses provide strength even in the event of large spans.
Crate
It is a dock or beam installed perpendicular to the rafter legs. Designed to give extra strength to structures. For the crate, you can use a trimmed or unedged board or timber, a prerequisite is the removal of bark. If soft roofing material is used, the lathing is made continuous, for example, from plywood sheets.
Horse
This is the name of the top line created by the connecting ramps, located horizontally.
Overhang
Usually it is about 0.4 m, this is the distance from the bearing wall of the house to the overhanging edge of the roof. Designed to protect walls from rainfall.
Mares
Used if the rafters have a length that does not allow to properly organize the overhangs. Mares serve to lengthen the hind legs. A board is used to make fillies.
Calculation of the rafter system of a gable roof
Since a rather serious load will be created on the roof structure from the side of the roofing material itself, as well as rain water during heavy rains or snow lingering on the roof, its reliability can be ensured only by competent calculation.
If the gable roof will have a complex broken shape, then it is advisable to entrust the calculations to professionals, you can make an independent calculation in the case of a small area.
Consider what formulas you need to use, and also find out what additional information will be required for calculations.
The first step is to determine at what angle the ramps will be inclined. It should be noted that universal, i.e. suitable for any of the roofing materials, is an angle of inclination exceeding 45 degrees. Naturally, the area of \u200b\u200bslopes in this case increases, the cost of materials - increase.
When choosing a smaller angle, it is possible to use exclusively materials that meet certain requirements. For regions subject to frequent heavy precipitation, roofs with a steeper slope are usually chosen; in areas where strong winds are observed, roofs with gentle slopes are recommended.
An obligatory parameter to be taken into account is temporary loads created by wind and snow. They can reach from 80 to 320 kg per square meter. m., depending on the climatic conditions of the area in which the structure is being built.
In the calculation, the transition coefficient from the snow cover should be used:
- if the angle of the roof is less than 25% - 1
- if the angle of inclination is from 25% to 60% - 0.7.
When calculating the wind load, the coefficient of aerodynamic influence and changes in wind pressure are used.
Installation of a gable roof will also require calculating the weight of the roofing cake, this value is constant, it takes into account the weight of all structural elements, including roofing material, if the house is with an attic, the weight of the ceiling trim is added. The average value of the constant load is about 40-50 kg per square meter. m
To calculate the total load, it will be necessary to add together the indicators of temporary and constant loads exerted per 1 sq. m of the roof. Based on the result obtained, the correct section of the rafter leg is determined. For greater clarity, in accordance with the results obtained, a drawing of a gable roof is performed.
Regarding the verification of the correctness of the calculations, it is recommended to contact the specialists of the design organization. When conducting independent calculations, you can use the more accurate information provided by the directories, which are easy to find on the Internet, and also use the online calculator.
Gable roof truss calculator
Using a calculator will determine:
- ramp angles
- rafter dimensions
- optimal materials for the construction of the lathing
- the volume of each of the materials
The calculation base of the online calculator contains the parameters of commonly used roofing materials. When making calculations, the norms of SNiPs are also used.
When filling out the fields of the calculator, you should not miss the opportunity to take advantage of additional explanations for each of the items marked with the additional information icon. Regarding the results, you can also get additional information.
Using the online calculator you can calculate:
- the angle of the roof, taking into account that the roof will be symmetrical gable, the required amount of roofing materials, also - make sure that the roof can be mounted with such an angle from the selected material
- total slope area (including overhangs)
- the amount of insulation, waterproofing and roofing materials, how many rolls will be needed and their approximate weight
- loads on the rafter system, the maximum possible load, taking into account the loads exerted by snow and winds
- rafter lengths and their number, minimum cross-section,
- the number of rows of the crate and the recommended distance between the fragments
- the number and volume of boards for the crate, as well as their total weight.
Installation of a rafter system of a gable roof
At the beginning of the work, the Mauerlat is mounted to the longitudinal walls. Installation is carried out with anchor bolts, on the top wall edge, preferably - along the axis of the wall, if this is not possible - offset to one or the other edge is allowed, but the distance from the edge of the wall should not be less than 50 mm. It is customary to lay waterproofing under the Mauerlat, it is possible to use roofing material. Mauerlat links are connected using direct locks, its design must have high strength.
In wooden log houses, roof elements are attached directly to the upper rim.
In accordance with the previously defined parameters, rafter legs are made, if the dimensions of the material do not allow making them whole - the necessary length is obtained by building.
Depending on the insulation used, the distance between the rafters is calculated - it is important to take into account the width of the insulating material, otherwise it will need to be cut.
For the assembly of rafters, special templates are made:
- for assembling the farms themselves
- for making cuts on rafters
The first template is constructed from ordinary boards equal in length to the rafter legs. One edge of the boards is joined with 1 nail. It looks like scissors. The loose edges of the board are installed on the supports at the points where the rafters will be located.
An important point - the angle that turned out will determine the slope of the ramp, it is fixed with a pair of nails or even a crossbar is constructed from the trimmed board and fixed.
The second template is made of plywood, it is used to make mounting cuts, prepared truss parts are connected at a given angle. Next, the already assembled farms are raised to the roof and mounted on a Mauerlat.
First of all, the installation of pediment farms is carried out, in order to produce their correct fastening, temporary struts are used. Then the tops of the installed pediment trusses are connected with a cord. It will indicate the location of the future ridge and determine the installation level of the remaining farms. The recommended distance between the rafters is 0.6 m, but depending on the roofing material used, it can be adjusted.
For fastening heavy bulky fragments of the structure, supports, struts, crossbars are used.
To install the ridge beam, special supports are used. Then the rafters are attached to it short, diagonal and intermediate.
There is also another option for installing rafters - when trusses are not collected on the ground, but directly at the installation site.
Rafters for a gable roof - mounting options
Attaching rafters to the Mauerlat can be done in two ways. Using corners or support bars create a rigid version, eliminating the possibility of rotation, shear, bending. Using this method also cuts, staples, drive in nails. An anchor or wire may be used to impart particular strength to the wall.
The second method is to create an articulated or sliding mount. Apply it in the construction of houses made of wood. In this design, the immovable fragment is the Mauerlat, the movable fragment is the rafters. Provides mobility in a specially made gash.
To fix the adhesion point, a metal plate with holes for nails is usually used, but if there is none, then two nails are hammered at a certain angle.
Installation of the lathing over the old roof
Since the issue of repairing a roof arises not infrequently, you should consider replacing the old roof with a new one. Sometimes circumstances are such that it is very difficult to dismantle.
There are two options here:
- complete dismantling of the old roof, preparation of materials and installation of a new roof
- installation of a new roofing material over the old
The second option is possible if the old rafter system is in good condition and its strength margin is sufficient to withstand the load created by new roofing materials.
It is recommended to carefully check the old rafter system and crate for defects, sagging areas, cracked bars, fungal lesions. All deficiencies found should be eliminated, areas severely affected by the fungus should be replaced with new fragments.
Next, you can proceed with the installation of the new crate. The board that will be used for it (coniferous wood, grade III at least) is initially treated with antiseptics and dried.
The roof itself is carefully cleaned of debris, moss, chipped fragments of the roofing material (slate), the deformed sections are straightened.
The step of installation of the bars of the counter-lattice is about 60 cm, if climatic loads are assumed to be increased, the step is reduced to 45 cm. The counter-lattice is fastened with wood screws or rough nails (125 mm).
The beam for creating a counter-lattice uses the following sections:
- for metal tiles and profiled sheets - 50 mm x50 mm
- for slate - 50 mm x75 mm
- for onduvilla - board 25 mm x100 mm
On top of the old roof, it is recommended to lay roofing strips at the points of contact with the new crate.
Installation begins with the extreme bars, then a cord is stretched between them, the rest of the elements are aligned along it. To align the bars, plywood of the required thickness is laid under them.
It should not be forgotten that asbestos roofing or roofing from natural tiles in any case are subject to complete dismantling.
