Building a gable roof with your own hands is a relatively straightforward process. By understanding the design and technology of working with the standard parameters of a classic gable roof, and building upon that knowledge as well as the information contained in this article, you can, with just a little effort, adorn your home with a beautiful roof built by yourself.
Features of Gable Roofs
The structural basis of a gable roof is the most simplified of all possible multi-pitched roof designs. The concept of a gable roof involves the formation of two inclined planes (slopes) and gables on opposite sides.
Moreover, equal slopes are not at all mandatory. This allows for less strict adherence to the equality of the lengths of these slopes, so the length parameters can also be completely different. Incidentally, it is precisely this feature that has enabled the construction of roofs with non-identical slopes in terms of parameters and has opened up more possibilities in house design, leading to the great popularity of these roofs.
Typically, the intersection of the slopes is located at the ridge, which runs parallel to the long side of the building. The simplicity of this design determines the traditional form of the building.
A significant advantage of gable roofs lies in their excellent protective functions. The building will not be threatened by damage caused by bad weather conditions, as the absence of sharp breaks in the slopes allows rainwater to drain freely from the roof surface, and the absence of concave corners (also called valleys), which are formed where slopes intersect, solves the problem of snow accumulation in these areas.
Symmetrical gable roof parameters form an isosceles triangle at the top. However, for those who do not wish to adopt a standard and common approach to roofing their home, more interesting and complex variations of gable roofs should be considered.
The broken-line design of a gable roof with unequal slopes offers residents of the future building advantages in increasing the living space inside the house. This can involve creating additional space for a large attic or constructing a mansard.
Another approach is the absence of symmetry in gable roof design. From the outside, such a solution has a rather unusual and original appearance, but the space created in the attic is much smaller.
Furthermore, there are other types of roofs with two slopes. A multi-level arrangement of slopes, ending at different heights, does not meet at the ridge. This results in a broken-line roof structure. Undoubtedly, such an option is only within the capabilities of a specialist in this field, but the investment in such a construction is fully justified by the excellent result.
How to Determine the Pitch (Angle of Slope)
The range of pitches for gable roofs spans from 11° to 45° and even more.
If your goal is to construct a multi-level roof with two slopes, keep in mind that the pitch depends on many factors:
- The type and quality of materials to be used for the roofing;
- Climatic conditions;
- The architectural design of the building itself.
Warmer and drier climatic data of a region do not require very steep angles for roof structures, so the surface can be made less steep. If, on the contrary, climatic conditions imply a large amount of precipitation, the pitch should be steeper to prevent snow accumulation and reduce its load on the roof surface.
There is also a pitch at which snow cover exerts practically no pressure. This is an angle of 45°, and using it in design significantly reduces the possibility of miscalculation.
Roofing process planning should also include data on the load exerted by wind force. An increased slope enhances the wind pressure on the surface, so it would be wise to reinforce the sheathing and rafters. For instance, an increase in pitch from 11 to 45 degrees increases wind pressure fivefold. Therefore, if your building is located in an area with strong winds, the roof you design should have a shallower slope.
The design of a gable roof with unequal slopes opens up possibilities for arranging a veranda under the roof or creating a canopy covering a terrace.
Installation of Rafters for a Roof with Two Different Slopes
The rafter system is the basic foundation on which the entire structure will rest. When undertaking a project for a gable roof with unequal slopes, it is essential to understand how a symmetrical rafter system differs from the one you will be constructing for a roof where the slopes have different parameters.
At the core of slope symmetry are triangles with equal sides, which ensures the equivalence of opposing slopes in all geometric parameters and angles of inclination.
As for designing a roof with different slope parameters, each side must be thought out individually. Consequently, the triangle will have unequal legs.
This will take a bit more time during project development and implementation. But in return, such a structure is more attractive and unusual, looking much more impressive from the outside.
Rafter systems can be either sloped (layered) or hanging. The outermost supports of buildings typically have hanging rafters, because the legs of these rafters are designed for bending and compression functions.
Such a structural solution has a spreading (thrust) action that extends horizontally, transferring to the walls. To reduce this, it is recommended to use a wooden or metal tie beam, placed at the very bottom of the rafter base.
The beam will serve as a floor joist. This option is good for roofs with mansards. To make the rafter fastening stronger and increase its durability, the tie beam must be placed sufficiently high.
The use of a layered (sloping) rafter system is advantageous when roofing structures with a central load-bearing wall or with intermediate columnar supports.
The ends of the rafters transfer their weight by resting on the building’s walls. Partially, they also bear on internal walls and supports, thus it is possible to use their elements as bending beams. Such a roof ultimately has a lighter construction.
The construction is erected by alternating hanging and layered (sloping) rafter trusses, located above several spans:
- Hanging rafters are best installed where there are no intermediate supports. If layered (sloping) rafters are present, installation is only possible if the span between supports does not exceed 6.5 meters.
- To increase the width of the rafters, an additional support is added. It must be covered with layered (sloping) rafters, the size of which does not exceed 12 meters, and with two supports – 15 meters.
- In structures built using timber as a material, the rafters rest on the top courses. Greater fastening strength can be achieved by securing the rafter legs with dowels, bolts, or brackets.
To assemble all component parts, bolts, tooth joints, and metal plates are used. As protection from the detrimental effects of climatic weather conditions, the use of an eave overhang, at least 5.5 cm long, is recommended; it is used as the top strapping.
Calculation is a responsible matter. Incorrect cross-section can lead to rafter failure. Such a problem is seen in violations of joint placement, and in such a case, roof operation simply becomes impossible. Therefore, even when performing all stages of work yourself, it is still safer to entrust the calculation to a professional.
Mauerlat Fastening
A timber beam with cross-section parameters of 15×15 cm is the mauerlat. It performs a supporting function for the sloped rafters, evenly distributing the overall load, and also acts as a foundation. The mauerlat serves as a base under the rafter foot, extending along the entire length of the structure. If the cross-section width is too small, sagging may occur after some time.
To prevent such sagging, a lattice composed of posts, crossbeams, and struts is used. Boards with dimensions of 25×150 mm are used, and in addition, plates obtained from logs with a diameter of 13 cm can be laid.
Calculating the Roof Area
To avoid confusion and correctly calculate the roof area:
- There is no need to calculate small details such as chimney pipes, dormer or roof windows, or ventilation openings;
- The size of the installed slope must be extremely precise; the calculation should be taken from the edge line of the eaves directly to the very bottom of the ridge;
- Firewalls, overhangs, and parapets must also be accounted for;
- Much depends on the roofing material; this aspect also needs attention.
An important point: when using rolled materials or tiles, it is necessary to reduce the length of the slopes by 70 centimeters.