Recently, the hip roof truss system has become increasingly common in the construction of country houses. In this article, this system is considered in more detail, as well as examples of its calculation and arrangement.
If a truss system is chosen when designing a house, the hip roof consists of two parts:
- Gable roof, partially covering the house along its entire length;
- A hip covering the space that is not covered by a gable roof.
The hip roof device consists of two types of slopes interconnected.The first type is the trapezoidal slopes that make up the gable roof, and the second is the slopes in the form of triangles that make up the hips.
Professional builders sometimes also use the expression "Danish roof", meaning a hip roof variant that is quite popular at the present time, where the hip does not fit to its full height, which creates a unique appearance for the whole structure.
In addition to the Danish, there are other varieties of hip roofs, for example, a hipped roof, which is used for square buildings around the perimeter.
Or a broken hip roof - the truss system in this case is a rather complex design of load trusses.
Broken roofs are not widely used, one of their main drawbacks is the long construction period due to the laboriousness of creating the structure.
Hip roofs are by far the most attractive both in terms of aesthetics and in terms of saving building materials, in difference from a shed roof with your own hands, but at the same time they require the greatest expenditure of labor resources, the procedure for laying roofing material at the final stage of construction is especially time-consuming.
Quite often, developers decide on the independent construction of a hip roof.
The greatest difficulty in the construction of hipped roofs lies in their correct and accurate marking, with the slightest mistake in which all the work can be in vain, which leads to additional financial costs.
Therefore, even with the independent construction of a hip roof, you should either invite a specialist who will carry out all the calculations and perform competent markup, or, in extreme cases, use a special hip roof calculator program to prevent errors.
Hip roof device
In order to have an idea of how to make a hip roof, you should first of all understand for yourself that the rafters, with the installation of which the process of installing the rafter system begins, are divided into two types:
- Diagonal, directed towards the outer corners of the walls;
- Oblique, directed to the inner corners.
The diagonal legs of the rafters are longer, therefore, if they are made from a board of insufficient length, it is necessary to pair the boards with each other to achieve the required rafter length, as, indeed, shed roof rafters.
When building a roof on your own, you should not only calculate the hip rafters of a 4-pitched roof, but also all other elements used in the construction of the roof.
In this case, the Pythagorean theorem, familiar to everyone from the school geometry course, will come to the rescue.
It is also mandatory to prepare a marking rail, on which all distances used should be marked in advance, so as not to repeat measurements each time, in which the risk of error increases significantly.
The truss system of a semi-hip roof is most often made of boards, the size of which is 150x50 millimeters. From the same boards, the slats used in the crate are subsequently also cut.
Installation of the rafter system begins with the installation of two types of load-bearing beams:
- Beams installed around the perimeter of the building, which are also called "Mauerlat".
- Beams placed across the building, on which racks are installed, on the basis of which a ridge span is created from the same material as the rafters.
With the help of a rail and a plumb line, it is necessary to accurately mark the location and verticality of the ridge, while the most important task is to accurately comply with the height dimensions determined by the building project. To fix the ridge racks, jibs are used.
The next stage in the construction of the hip roof is the laying of diagonal rafters, in which a prerequisite, as already mentioned, is to accurately measure their length, calculated so that the lower part of the rafter protrudes beyond the edge of the wall, creating something like a cornice measuring 40-50 cm , preventing the ingress of precipitation and water flowing from the roof onto the walls.
Next, the intermediate type rafters are installed. It should be clarified that the intermediate hip roof rafters are divided into two categories:
- Central, laid on top of the ridge beam and having a longer length than the beam. The number of these rafters is selected according to the length of the building.
- Corner, the upper part of which rests on diagonal rafters. The size of this type of rafter decreases as they approach the corner of the building.
Important: the number of central rafters on each side of the span of the ridge should not be less than three, regardless of the length of the building.
Laying the central rafters
In order to correctly lay all the rafters, that is, so that the frame of the hip roof has minimal errors, it is imperative to carry out accurate marking and designate all the places where the fastening will be carried out.
This is done by defining two points, one of which is located on the Mauerlat (the lower trim of the building) exactly in the middle of the length of the wall, and the other is in the center of the ridge beam. Between these two points, an intermediate central rafter is laid.
If the design provides for only three rafters, then the location of the remaining two two is calculated very simply: on both sides of the previously laid central rafter, half the distance to the ridge beam is measured, after which the rafters are laid on the marked points parallel to the central one.
If the number of central rafters exceeds three, then they should be evenly distributed along the span of the ridge.
This distribution is achieved by dividing the length of the ridge beam by a number exceeding the number of rafters by one, the resulting number is the required distance between them.
The required length of the central rafters can be measured by several methods.
One of the simplest of them is the method when the rafters are laid in the place where they will be attached, the necessary contours of the cuts are outlined on them, taking into account the margin left under the eaves, after which the extra (outlined) parts of the boards are simply sawn off.
A more convenient method is to measure the height of the span of the ridge and the projection of the rafters onto the plane of the roof base, after which, using the aforementioned Pythagorean theorem, the length of the rafter is calculated, to which the size of the cornice is added.
The measurement of the board and sawing off its excess is done on the ground, after which the board rises to the roof, already prepared for installation and fastening.
Even simpler is the method in which all the coefficients of the lengths of the rafters and their dependencies on the height of the span of the ridge and the dimensions of the house are in a specialized reference book for builders.
In this case, it is enough just to clarify all the dimensions of the structure in the drawing of the hip roof, which is part of the house project.
The calculation of the length of the diagonal type rafters is carried out in the same ways, with the obligatory observance of the correct measurements of the lengths used later in the calculations.
Rafter connection
One of the most important points when installing the rafter system is the connection of several of its elements at the intersection of two central and two diagonal rafters, as well as one central hip rafter on the ridge beam, on which a special incision is made with a double bevel.
At the central hip rafter and at the diagonal rafters, the same double bevel should also be sawn.
The calculation of the corner rafters is performed a little differently, since the fact that the connection of the corner rafters of the hip and the gable system occurs in pairs is very important.
Quite often, qualified builders measure the length of the corner rafters by eye, which makes it possible not to measure it. The boards from which the corner rafters will be made are laid in the place where they will be attached, adjusted to the required length.
Next, mark the necessary places of cuts, cut off the excess and make fastening. This method is used quite often, but its disadvantages include the appearance of waste and significant time costs.
A much more accurate method, which also does not generate waste, is to mark the lengths of the corner rafters using a template specially made from a plywood sheet in the form of a right triangle.
In any house project, the angle of inclination of the hip roof must be taken into account, which must match the slope made on the template.
For example, with the required roof slope of 5:10, the lengths of the legs of the template should be 40 and 80 cm. When marking the rafters and trimming it, this template will be simply indispensable.
To determine the distance at which the intermediate corner rafters will be mounted, you should choose one of the rafters, which is the starting point, usually this point is located on the Mauerlat.
The distance from it to the corner of the building should coincide with the length of the rafter without taking into account the eaves, while the projection of the rafter and the distance to the place where it is fixed on the Mauerlat form a square with each other.
The remaining intermediate corner rafters should be installed evenly, fixing their lower ends to the Mauerlat, and the upper ends to the diagonal rafter. The hip rafters are mounted end-to-end with the corner rafters that make up the gable part of the roof.
When building a hip roof, one should also remember about various nuances, for example, that the dimensions of the roof itself are affected by the dimensions of the building on which it is installed, as well as the material for the roof.
Eg, do-it-yourself slate roofing will cost you less. than tiles.
Considering that the width of country houses is usually a rather serious value, the indicator of their sagging should be used in the calculation of the rafter system, which is primarily relevant for the central diagonal and intermediate rafters.
In modern suburban construction, the hip roof truss system is becoming increasingly popular. This is facilitated by its characteristics such as reliability, durability and aesthetics, which, of course, are the most important in the construction of a cottage or a country house.
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