From time to time, buildings made of bricks, building blocks or other materials can be seen on the sites. At the same time, it is important not only how high-quality the base and erected walls turned out to be, a lot also depends on the installation of the roof structure. Knowing how to fasten rafters allows you to get a solid roof 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
This definition can be considered the roof frame of any house, which 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/m2!
The reliability of the entire roof is directly dependent on three main factors:
- Calculation accuracy - it is important for the correct selectionnumber and section of supporting elements.
- Material of manufacture.
- Compliance with installation technology.
Knowing and understanding how to fix the rafters allows you to improve the load-bearing qualities of the entire frame and provide the necessary strength and reliability. Mistakes made in the rafter fastening system lead to significant losses in the properties of the roof structure. It is also impossible to exclude the possibility of deformation of the roof. Probably, it’s not worth mentioning what all this can lead to in the end …
The roof frame is not just called a truss system, since 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 load-bearing walls of the house is achieved.
Components of the roof structure
But what exactly are the elements of this whole system? It is based on many components, each of which serves to fulfill its own 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 precisely the Mauerlat. This is a massive bar 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 (bath, summer kitchen, etc.). Often the fastening of wooden rafters is made to it. Thanks tosuch a base, the load is distributed evenly, and the structure itself is protected from tipping over.
Due to the presence of rafter legs, the weight of the entire roof structure is supported. The entire space between them is usually filled with heat-insulating material, and a crate is laid on top.
But what are runs? These are horizontally oriented bars that are located along the roof. They serve as a reliable support in the fastening system of the gable roof rafters. 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 the side run, which is attached to the center of the rafter legs.
Racks are additional supporting elements for supporting the ridge and rafters, which partially perceive the load of the entire roof structure.
As for the struts, in this case we are talking about inclined beams that support the rafters and thereby increase the strength and 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 rafters. And without these elements it is impossible to complete 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 ensure the protection of all its inhabitants from various kinds of weather conditions. BasedRussian 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 the household and the life of the building will depend on how well and reliably the roof is made. At the same time, the aesthetic component should not be discounted, because the roof is the decoration of any house, 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 how to fasten rafters, but the crate plays an important role in this. After the frame, consisting of rafters, is delivered, it's time to take up another, no less important stage - the creation of the mentioned structure. The crate can be of two types:
- sparse;
- solid.
Sparse crate is characterized by a rare spacing of elements. This design is ideal for slate, ceramic or metal roofing.
Solid construction is formed from boards with a pitch of no 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 rolled material. In addition, this is a prerequisite for difficult places - the output of the chimney, the intersection of the slopes, along the roof eaves.
Rigel
This is a rather voluminous term as this element has many functions. It is even made from different materials, depending onthe nature of the application. But with regard to the roof, he has a certain task. And in fastening for rafters, this element also plays an important role. A crossbar is a horizontal beam that connects the rafters to each other, 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 truss frame, where different fasteners are used:
- bolts with nuts;
- studs with washers;
- special fasteners;
- nails;
- combined option, when several types of fasteners are preferred at the same time.
In addition, the mount itself can be with a tie-in or overhead.
Special overlays
In the process of creating a roof frame, it is sometimes 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 elongating the rafters.
There are three scenarios for this, depending on the material used:
- Beams or logs - building up takes place using an oblique cut at the junction. To avoid rotation of both fastened elements, both parts are fixed with a bolt.
- Pair splicing of boards - in this case, the boards are pre-folded with an overlap, after which they are fixed with nails.
- Single bar - here the frontal emphasis is mainly used. I.ethe end parts of the boards are joined together using metal or wooden linings.
In the latter case, the fastening of the gable roof rafters sometimes includes an oblique cut due to insufficient material thickness. As for the number of overlays, you can use one or two on both sides, depending on the specific situation.
Rafter material
With the main elements of the roof, everything is now more or less clear, but what are the rafter legs (rafters) made of? After all, it is the most important part of any roof. And you can't do without them. Usually softwood is used for their manufacture:
- spruce;
- larch;
- pine.
In this case, the material is pre-dried well to a moisture level of not more than 25%. However, the design of natural wood has one significant drawback - over time, the rafters are deformed. To avoid this, metal elements are provided in the system for attaching rafters to beams (for example).
But even 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 mentioned drawback, care should be taken that the wood does not touch the metal. This can be done using waterprooffunds 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 rolled metal is used:
- I-beam;
- brand;
- corner for attaching rafters;
- channel.
Unlike a wooden structure, such a structure is more compact in size. However, there is also a drawback here - heat is retained worse, and therefore the use of high-quality insulation is required, or even in large quantities.
Varieties of rafters
Before we move on to analyzing the methods of attaching rafters, let's get acquainted with these basic elements of the entire roof structure. They can be of three types:
- layered;
- hanging;
- sliding.
Laminated rafters are elements that have two points of support. One of them falls on the ridge run, and the other is the Mauerlat. This option for attaching rafters is relevant in the case when there is one load-bearing wall or several of them inside the house. And you can “lean” rafter legs to them. 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 impact on bending and expansion, and for this reason there isthe need to strengthen this structure. This is achieved through the use of horizontal elements (crossbars, puffs, contractions). The hanging system for attaching rafters to the wall of the house is relevant in cases where an attic is created or the span is 8-12 meters long, and the project does not provide for additional supports.
Sliding 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 they are assembled. At the same time, during the first 12 months of operation, the house loses up to 15% of its height. In this regard, if such houses are equipped with a rigid mount, the roof will warp over time and will have to be redone. The sliding system provides for fastening by the type of slider, respectively, you can avoid deformation of the roof - it will adapt to the shrinkage of the building.
Shed roof
Everything that was described above mainly refers to gable roofs, but in private housing construction there is another option - a shed roof structure. However, this option is not widely used, since in most cases the preference is in favor of a triangular roof. Nevertheless, for buildings for household purposes, this is the best option in terms of investment.
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 shed roof, since the same elements mainly appear here:
- Mauerlat - as we remember, this is a kind of"foundation", which is fixed on top of the external load-bearing walls and takes on 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. For buildings constructed from brick or gas silicate, a concrete screed is formed along the upper edge, which requires the creation of formwork.
- Rafter legs are flat bars with a section of 50 × 150 mm or 100 × 150 mm, which rest on the walls, forming a slope. The step between them is usually from 600 to 1200 mm. It is too rare or often undesirable to position the legs: in the first case, the structure may not withstand the weight of the roof, while in the second it will turn out to be heavy.
- Brace - an additional frame element that serves as a support for 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 section of 50×150 mm.
- Rack - another additional vertical support element for fastening for rafters, in which one side falls on the load-bearing 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 larger distance will not provide the necessary level of support.
- Lying down 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.
- The scrum is a board placed horizontally and connecting two racks, which prevents them from bursting.
- Filly - in them arisesa necessity in the case when the length of the rafter legs is not enough to equip the roof overhang. Usually these are boards with a smaller section than the legs themselves. At the same time, there should be at least 400 mm from the wall to the end of the filly.
Unlike a gable roof, fixing a shed truss system is a simplified variety that has its own advantages. And above all, it is light weight, for which it is not necessary to strengthen the foundation.
Secondly, this is the availability of the material - mainly wood is used, which is not so expensive. And finally, the installation itself does not require much effort - it is not difficult to do it yourself, there would be a desire.
Connecting knots
With their lower part, the rafter legs rest on the load-bearing walls. And this can be done in different ways:
- through Mauerlat;
- connection to floor beams;
- mount to the ridge;
- connection of rafters to each other.
In the case of installation of hanging rafters, an important point should be taken into account - with a rigid connection of the upper parts of the legs, there is a horizontal expansion load not on the walls of the house. To extinguish this pressure, puffs from a bar or board are used. In this case, the connection of the building wall occurs with a non-thrust triangle.
But instead of puffs, other options are also acceptable - floor beams laid in a perpendicular direction to the walls act as a good alternative. Such a rafter attachment point (in the absence of a Mauerlat) is relevant in the case ofconstruction of light attics. But only if the walls are able to withstand the point load.
For example, connecting rafter legs to a brick wall necessarily implies the installation of a Mauerlat. This is due to the fact that the walls laid with piece building material are not designed for point loads.
To create a roof overhang, it is necessary for the beams to go beyond the plane of the walls by 500 mm (at least!). The rafter legs themselves, which are fixed at the edges of the beam, should also protrude beyond the boundaries of the walls.
Fixing the rafters on the Mauerlat
This method of attaching rafter legs is used in most cases. After all, it is he who allows you to evenly distribute the weight of the roof structure on the walls and foundation of the building. In turn, the rafters themselves can be attached to the "foundation" in different ways of fastening:
- hard;
- sliding.
In the case of a rigid connection, the possibility of shifts, bends, and also turns between the connected elements of the entire structure is completely excluded. This is achieved using the following fixation methods:
- use of metal corners for attaching rafters;
- formation washed down on the rafter leg.
In the first case, a support beam is required. The leg itself rests on the line of pressure, after which it is fixed with a metal fastener to prevent lateral displacement.
The second option is given more preference. Provided herethe use of nails that enter at an angle towards each other (they cross inside the Mauerlat). The third nail is driven into the bottom of the rafter leg vertically. Both options require additional fastening with wire, wire rods, anchors.
Sliding or hinged fastening of the rafters to the beam provides the rafter legs with a slight displacement relative to the Mauerlat in acceptable values. Here, too, several fixation methods are used:
- Washed down the legs using a staple to secure them.
- A vertically driven nail or two side nail at an angle.
- Using the skid mount.
And as we now know, sliding fixation of rafters is a mandatory component in relation to wooden buildings. And as a result of shrinkage of the house, deformation of the roof structure is excluded. As for the remaining elements of the roof, their installation is carried out according to standard technology.
Fixing rafters to beams
Here you can also consider several options that can be used alone or in combination:
- tooth with emphasis;
- spiked tooth;
- emphasis on the end of the beam.
The amount of tooth formation is determined by the angle of the rafters. In this case, the entire load is effectively transferred from one element of the system to another.
The fastening of rafters to beams with cutting 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 leg, and anotch with a socket for a spike. In this case, 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 to the beam can be done using a bolted connection or a bolt with a clamp.
Attaching the rafters to the ridge
This method of connecting the rafter legs also has its own characteristics. Most common mounting methods:
- butt joint;
- fastening through the run (ridge beam);
- lap method;
- mount to the ridge.
Connecting the legs together end to end is the easiest and most reliable method of installation. In this case, the upper edge of each of the rafters is cut off at a certain angle, depending on the slope of the slope. After that, the opposite boards are connected by cut points using 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 lining. 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 the rafters to the wall with an overlap is even easier to implement, since there is no need to cut anything. The rafter boards are connected to each other by overlapping the side surfaces. The fixation itself is carried out with studs with washers or with bolts.
In execution, the connection through the skate itself resembles the butt method, but there is a slight difference. The upper part of the rafters is also cut 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 on sale, with which you can create a roof frame. Moreover, almost all of them are made of the same material - metal.
The following varieties can be considered the most popular fasteners for attaching rafters to a house:
- Brackets. These elements are made of galvanized metal (2 mm). They are fastened with anchor bolts, nails, screws.
- Corners. They allow to strengthen the fastening of the rafters, make the connection strong and help to increase 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 ragged nails or screws.
- Perforated tape. Another option with which the structure is given the necessary strength and rigidity.
- LK mounts. Reminds me of 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.
- "Sled" is an ideal way to attach rafters fora wooden house that shrinks. Thanks to this solution, deformation of the roof can be avoided.
- Perforated metal plates. This is the simplest option among the others. 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.
