From time to time, you can notice brick structures, building blocks or other materials in the plots. At the same time, it is important not only how high-quality the foundation and the erected walls turned out, a lot also depends on the installation of the roof structure. Knowing the mounting methods for the rafters allows you to get a solid roof outlet that will last a long time. The main thing is to observe the technological features of various roof structures, and then many undesirable nuances and consequences can be avoided.
Rafter system
Under this definition, we can consider the roof frame of any house that takes on the weight of the entire roofing material, evenly distributing it over its entire surface. But it can reach a value of 500 kg / m 2 !
The reliability of the entire roof is directly dependent on three main factors:
- Accuracy of calculation - it is important for the correct selection of the number and cross-section of the supporting elements.
- The material of manufacture.
- Compliance with installation technology.
Knowing and understanding how to fix the rafters, allows you to increase the load-bearing qualities of the entire frame and provide the necessary strength and reliability. Errors in the system of fastening the rafters lead to significant losses in the properties of the roof structure. The likelihood of roof deformation cannot be ruled out either. Probably, it’s not worth mentioning what in the end it can all lead to ...
The roof frame is not just called the rafter system, because here the elements are interconnected by means of fasteners. As a result, it gives the entire roof structure the necessary slope. Actually, thanks to this, a uniform distribution of the entire load on the bearing walls of the house is achieved.
Roofing components
But actually, what exactly are the elements of this whole system? It is based on many components, each of which serves to fulfill its purely purpose:
- Mauerlat;
- rafter legs;
- runs;
- racks;
- struts.
The construction of any residential building or structure begins with the construction of the foundation. The roof also has its own "foundation", which is exactly Mauerlat. This is a massive beam or beam with a section of 150 × 150 mm or 200 × 200 mm, which are laid along the supporting structures of a house or building (baths, summer kitchens, etc.). Often the fastening of wooden rafters is made to him. Thanks to this base, the load is distributed evenly, and the structure itself is protected from tipping over.
Due to the presence of rafters, the weight of the entire roof structure is maintained. The entire space between them is usually filled with insulating material, and the crate is placed on top.
But what are the runs? These are horizontally oriented bars that are located along the roof. They serve as a reliable support in the system of fastening the rafters of a gable roof. There are two types in total. One of them is ridge (its localization falls on the very top of the roof to hold the rafters). Another variety is a lateral run, which is attached to the center of the rafter legs.
Racks are additional supporting elements for supporting the ridge and rafters, which partially absorb the load of the entire roof structure.
As for struts, then in this case we are talking about inclined bars that support the rafters and thereby contribute to an increase in strength, as well as rigidity of the entire structure.
However, the design of the entire roof structure will be incomplete in the absence of some additional and at the same time mandatory components. This can be understood from the photo of the rafter mounts. And without these elements it is impossible to finish the construction of the roof, because each of them fulfills its purpose.
Crate
What is the main task of the roof of any house? That's right - to protect all its inhabitants from various kinds of weather conditions. Based on the Russian climate, the roof perceives the load of the following nature:
- rain;
- wind;
- exposure to the burning sun;
- weight of snow and ice.
The comfort of households and the life of the building will depend on how well and reliably the roof is made. At the same time, you should not discount the aesthetic component, because the roof is the decoration of any home, and any owner wants it to look beautiful. And not to the envy of the neighbors, but for their own pleasure.
It is important to know the fixing methods for the rafters, but the crate plays not the last role in this. After the frame, consisting of rafters, is delivered, it's time to do another, no less important step - the creation of the mentioned structure. The crate can be of two types:
A sparse crate is characterized by a rare step in the arrangement of elements. This design is ideal for forming roofs made of slate, ceramic or metal tiles.
The solid structure is formed from boards with a pitch of not more than 10 mm or plywood. This is the best choice in cases where the roof is planned to be covered with soft tiles, flat slate or roll material. In addition, this is a prerequisite for difficult places - the conclusion of the chimney, the intersection of the slopes, along the eaves of the roof.
Crossbar
This is a fairly voluminous term, since this element has many functions. It is even made of different materials, depending on the nature of the application. But with regard to the roof, he has a definite task. And in the mount for rafters, this element also plays an important role. The crossbar is a horizontal bar connecting the rafters, which helps prevent the roof from bursting. Its role is to evenly distribute the load from the rafter system.
There are several options for attaching the crossbar to the rafter frame, where different fasteners are used:
- bolts with nuts;
- studs with washers;
- special fasteners;
- nails
- a combined option, when at the same time preference is given to several varieties of fasteners.
In addition, the mount itself can be with a box or patch.
Special linings
In the process of creating a roof frame, sometimes it becomes necessary to lengthen the rafter legs. And in addition to understanding how the attachment points of the roof frame rafters are connected, it is worth knowing the features of the rafter extension.
There are three possible scenarios for this, depending on the material used:
- Bars or logs - building takes place using an oblique cut at the junction. To avoid turning both fastened elements, both parts are fixed with a bolt.
- Pairing the boards together - in this case, the boards are pre-overlapped, after which they are fixed with nails.
- Single bar - the frontal emphasis is mainly used here. That is, the end parts of the boards are joined together using metal or wooden plates.
In the latter case, the fastening of rafters of a gable roof sometimes includes an oblique cut due to insufficient thickness of the material. As for the number of pads, you can use one or two on both sides, depending on the specific situation.
Material for rafters
With the basic elements of the roof, now everything is more or less clear, but what are rafters (rafters) made of? After all, this is the most important part of any roof. And to do without them will not work. Typically, softwood is used for their manufacture:
In this case, the material is pre-dried well to a moisture level of not more than 25%. However, the construction of natural wood has one significant drawback - over time, the rafters are deformed. To avoid this, in the system of fastening the rafters to the beams (for example), metal elements are provided.
But in this case, not everything is so simple. Yes, metal provides the entire roof structure with the desired rigidity. However, on the other hand, the service life of wooden elements is reduced. Condensation appears on metal surfaces and supports, due to which the wood begins to rot and deteriorate.
For this reason, the roof structure is completely made of wood. To eliminate the aforementioned drawback, care should be taken that the tree does not touch the metal. This is feasible when using moisture protective agents or, alternatively, film insulation.
On an industrial scale, in the construction of buildings and structures, preference is given to metal rafters, for the manufacture of which metal rolling is used:
- I-beam;
- brands;
- corner for attaching rafters;
- channel.
Unlike a wooden structure, such a structure is more compact in size. However, there is a drawback here - the heat is retained worse, and therefore requires the use of high-quality insulation, or even in large quantities.
Varieties of rafters
Before proceeding to a discussion of the methods of fastening the rafters, we will get acquainted with these basic elements of the entire roof structure. They can be of three types:
- in sternum;
- hanging;
- sliding.
Rafter rafters are elements that have two points of support. One of them falls on the ridge run, and the other is Mauerlat. This option for attaching rafters is relevant in the case when there is one supporting wall or several of them inside the house. And to them you can “lay down” the rafters. Also in this case, additional vertical supports (racks) are placed, which allows you to remove part of the load from the rafters.
Hanging rafters are called elements with only one fulcrum, which is located in the place where they are attached to the Mauerlat or wall. This frame perceives the effect on bending and bursting, and for this reason there is a need to strengthen this design. This is achieved by using horizontal elements (crossbars, puffs, contractions). The hanging system for attaching rafters to the wall of the house is relevant in those cases when an attic is created or the span length is 8-12 meters, and there are no additional supports in the project.
Moving rafters are widely used in the construction of houses from timber or logs. According to experienced builders, wooden buildings shrink over the next 5-6 years after their assembly. At the same time, during the first 12 months of operation, the house loses up to 15% of its height. In this regard, if you equip such houses with a rigid mount, the roof will warp over time and it will have to be redone. The sliding system provides for fastening like a slider; accordingly, roof deformation can be avoided - it will adjust to the shrinkage of the building.
Pent roof
Everything that has been described above mainly applies to gable roofs, but in private housing construction there is another option - a gable roof construction. However, this option does not find wide application, since in most cases the preference is in favor of a triangular roof. Nevertheless, for commercial buildings, this is the best option in terms of investments.
For those who are already familiar with the features of a gable roof, it will not be difficult to understand the essence of fastening the rafters of a gable roof, since basically the same elements appear here:
- Mauerlat - as we recall, this is a kind of "foundation", which is fixed on the upper part of the external load-bearing walls and assumes the load from the roof. In houses made of timber or logs, there is simply no such element, since its role is assigned to the upper crowns of the log house. In buildings constructed of brick or gas silicate, a concrete screed is formed along the upper edge, which requires the creation of formwork.
- Rafter legs are straight bars with a section of 50 × 150 mm or 100 × 150 mm, which rest on the walls, forming a slope. The pitch between them is usually from 600 to 1200 mm. To place the legs is too rare or often undesirable: in the first case, the construction may not support the weight of the roof, while in the second it will turn out to be heavy.
- The strut is an additional element of the frame that serves as a support to the rafter legs. It is attached to them at an angle and helps prevent their deflection. They are also made of wood and have a cross section of 50 × 150 mm.
- A stand is another additional vertical supporting element for fastening for rafters, in which one side falls on the supporting partition and the other supports the rafters. Thus, the weight of the entire roof structure is transferred to the foundation of the building. The step between them is usually 1.2-1.5 m. A greater distance will not allow to provide the necessary level of support.
- The lounger is essentially the same Mauerlat (from the same material), but with the difference that it is fixed on the internal supporting partitions of the house.
- Scrum - a board located horizontally and connecting two racks, which prevents them from bursting.
- Mares - they are necessary in the case when the length of the rafters is not enough to equip the roof overhang. Usually these are boards with a smaller cross section than the legs themselves. In this case, from the wall to the end of the filly should be at least 400 mm.
Unlike a gable roof, fastening a single-girder rafter system is a simplified version, which has its own advantages. And above all, it is light weight, for which there is no need to strengthen the foundation.
Secondly, this is the accessibility of the material - mainly wood is used, which is not so expensive. And finally, the installation itself does not require much effort - it is easy to do it yourself, it would be a desire.
Connecting nodes
With its lower part, the rafters rest on supporting walls. And this can be done in different ways:
- through Mauerlat;
- connection with floor beams;
- fastening to the ridge;
- connection of rafters among themselves.
In the case of installation of hanging rafters, it is worth considering an important point - with a rigid connection of the upper parts of the legs, a horizontal spacer load of not the wall of the house appears. To quench this pressure, use puffs from a bar or board. In this case, the connection of the wall of the building occurs with an indisputable triangle.
But instead of puffs, other options are also acceptable - floor beams laid in the perpendicular direction to the walls act as a good alternative. Such a rafter mount (in the absence of a Mauerlat) is relevant in the case of the construction of light attics. But only on condition that the walls are able to withstand a point load.
For example, the connection of rafters with a brick wall without fail involves the installation of a Mauerlat. This is due to the fact that walls laid with piece building material are not designed for point loads.
To create a roof overhang, a beam exit of 500 mm beyond the plane of the walls is required (no less!). The rafters themselves, which are fixed on the edges of the beam, should also protrude beyond the boundaries of the walls.
Fixing rafters on a Mauerlat
This method of attaching rafters is used in most cases. After all, it is he who allows you to evenly distribute the weight of the roof structure to the walls and the foundation of the building. In turn, the rafters themselves can be attached to the "foundation" in various ways of fastening:
In the case of a rigid connection, the probability of shifts, bends, and also rotations between the connected elements of the entire structure is completely eliminated. This is achieved using the following fixation methods:
- use of metal corners for fastening rafters;
- formation washed down on the rafter leg.
In the first case, a support beam is required. The leg itself abuts against the pressure line, after which it is fixed with a metal fastener to avoid lateral displacement.
The second option is given more preference. It provides for the use of nails that enter at an angle towards each other (inside the Mauerlat they cross). The third nail is driven vertically into the lower part of the rafter leg. Both the one and the other option require additional fastening with wire, wire rods, anchors.
The sliding or hinged fastening of the rafters to the beam provides the rafters with a slight displacement relative to the Mauerlat in acceptable values. Several fixation methods are also used here:
- He washed down his legs using staples to attach them.
- A nail driven in vertically or two laterally at an angle.
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The fastening of rafters to beams with a felling and a single tooth is used at a slope angle of 35 °. At the same time, a tooth with a spike is made in the landing heel of the rafter's leg, and a notch with a spike socket is cut out in the beam. Its depth should not exceed a third of the thickness of the beam. As for the cutting itself, it should be done at a distance of 250-350 mm from the edge of the beam, which extends beyond the walls of the house. Due to the presence of a spike, lateral shift of the rafter legs is excluded.
In addition, the connection of the rafter legs with the beam can be performed using a bolted connection or a bolt with a clamp.
Mounting rafters to the ridge
This method of connecting rafters also has its own characteristics. The most common mounting methods:
- butt joint;
- fastening through the run (ridge beam);
- lap method;
- fastening to the ridge.
Butt joint between the legs is the easiest and most reliable installation method. In this case, the upper edge of each of the rafters is cut off at a certain angle, depending on the size of the slope. After that, the opposite boards are connected in places by means of nails (at least 2 pieces each with a size of 150 mm or more).
In addition, such a connection can be further strengthened with metal or wooden plates. Wood products are fixed with nails on both sides of the rafters along the formed "seam". For metal plates, it is better to use bolts.
The method of attaching rafters to the overlap wall is even easier to implement, since there is no need to cut anything. Rafters are connected to each other, placing the lateral surfaces with an overlap. The fixation itself is performed with studs with washers or with bolts.
In execution, the connection through the skate itself resembles a butt-butt method, but there is a slight difference. The upper part of the rafters is also cut off at a certain angle, but they are not connected to each other, but are attached to the ridge beam.
Fixing accessories for connecting rafters
A lot of fasteners are sold, with which you can create a roofing frame. Moreover, almost all of them are made of one material - metal.
The following varieties can be considered the most popular fasteners for attaching rafters to the house:
- Brackets. These elements are made of galvanized metal (2 mm). They are fastened with anchor bolts, nails, screws.
- Corners. They make it possible to strengthen the fastening of rafters, make the connection strong and contribute to increasing the bearing capacity of the entire roof structure. Another advantage of the corners is that there is no need to violate the integrity of the frame elements. The metal products themselves are fastened with rugged nails or screws.
- Perforated tape. Another option with which the design is given the necessary strength and rigidity.
- LK mounts. Remind brackets. In total, several types are produced, depending on the dimension. This allows you to pick them up to any thickness of the bar or board. Fastening is carried out with nails or screws.
- "Sleigh" is an ideal way to fasten rafters for a wooden house, which shrinks. Thanks to this solution, roof deformation can be avoided.
- Perforated metal plates. This is the easiest option among other existing ones. This fastener has a lot of advantages, due to which it is simply very popular not only in private housing construction, but also in other areas of construction.
In addition, other varieties are widely used - bolts with nuts, self-tapping screws, wire ties.