Roof truss system. How to install a gable roof truss system - a step-by-step guide Roof without purlins

A roof with two slopes is the most common option for completing the box of a private house. In its manufacture, it is important to correctly select the cross-sections of the supporting elements, securely fasten the nodes and choose the right type of construction. The truss system of a gable roof does not have great difficulties and may well be made by hand.

Classification of truss systems according to the method of support

The structure can be classified in two ways. The first of them is the method of supporting the load-bearing elements. The gable roof truss system of the house in this case includes the following types:

• with layered rafters;
• with hanging rafters.

Roofing with the use of layered rafters involves their support at two points. The design in this case avoids the occurrence of a serious spacer. To do the installation yourself, you will need the following basic elements:

• rafter legs;
• Mauerlat;
• crossbar;
• intermediate racks and struts with a large span of load-bearing beams;
• crate and counter-crate;
• overlays persistent bars.

At the top point, the installation provides for leaning on the crossbar. The installation also provides support at the lowest point - Mauerlat. You can assemble such a structure for a house with your own hands only in two cases:

1. A layered system is possible if the distance between the gables is not large. That is, such an installation is suitable for a small house with your own hands. The greatest length of the structure, which allows the construction of a wooden crossbar without additional reinforcements, is 6 m. For large spans, it will be necessary to install metal beams as a crossbar. When using a wooden beam, it will be necessary to provide intermediate racks, which are located on average every 2 meters. This can be avoided only when using glued laminated timber of a sufficiently large cross section as a crossbar. In this case, a free layout of the space becomes impossible - the racks in the middle of the room cannot be removed.
2. The second option, when it is possible to install a layered gable roof system with your own hands, is the presence of a wall in the middle of the house. The device in this case provides that the beam, on which the rafters will rest at the top point, will transfer the load to the inner wall. In this case, the supporting structure should not be confused with the partition. The partition rests on the floors, and installing the wall of the house with your own hands involves resting it directly on the foundations. Such a device is suitable for buildings with sufficient width, where it makes sense to install a wall fence in the middle.

The second option is hanging rafters. They are more complex in calculation, but they allow the installation in the under-roof space of a free-plan house. The design assumes the absence of a supporting wooden or metal bar in the upper part. Installation involves supporting the rafters only at the lowest point. In the upper part, the bearing beams are securely connected to each other. Installing such a system is like a farm. The design works on thrust, so it is important to prevent excessive horizontal load on the walls of the house. You can do this by doing the following:

• the device of a monolithic belt along the edge of the walls;
• it is necessary to make a reliable fastening of the Mauerlat of a gable roof to the wall of the house with your own hands;
• to eliminate the spacer, a contraction is established.

The fight or screed becomes one of the significant elements of the gable roof of the house. It prevents the expansion of the walls under the action of thrust. The following types of fights can be distinguished:

• located at the attic floor level;
• located at the level of the attic ceiling.

It is worth noting that the second option provides less reliability, since the higher the element is mounted, the stronger the rafters have an effect on it. If the fight turns out to be too long, you need to make it stronger with your own hands. For this, additional elements of the gable roof of the house are installed - suspensions. They connect the skate to the middle of the puff, which prevents it from sagging.

The gable roof truss system with hanging rafters allows installation with pre-assembly of trusses on the ground, then raise them to the roof and fix them.

This option is only suitable if you have lifting equipment, since the finished gable roofs of the house will become too large and heavy to lift with your own hands.

Classification by type of slope

The second division can be made depending on how the ramp line is designed. The views here suggest the presence of two options:

1. With straight slopes. The easiest way to do. Allows you to get the job done without any hassle. The disadvantage of this do-it-yourself roofing option is the reduction in attic space.
2. With broken slopes. Such types of roofing are more difficult to perform. It is assumed that there is a line along which the angle of inclination changes. The angle of inclination of the lower part of the slope must be made greater than that of the upper. Thus, it turns out to raise the ceiling of the attic and increase the free space. The installation of the roof is carried out with the installation of an additional crossbar at the fracture site.

These types involve a choice between them, depending on the wishes of the future owner of the building.

The main elements of the roof

The rafter system of the gable final part of the building consists of many elements. Installation should begin with a detailed study of each of them and the choice of their sections.

Mauerlat

When installing elements under a metal tile or other coating, it implies the use of a bar with a section of 150x150 or 200x200 mm. It is this size that allows you to most optimally distribute the load. then you need to choose a method of fixing it depends on the material of the walls. There are several options:

1. Frame, timber or log walls do not require the installation of a Mauerlat. In the case of a frame building, the top framing of the walls serves as a support for the rafter legs. during the construction of fences from timber or logs, the upper crown becomes the Mauerlat. It is important to correctly fix these elements in the wall structure.
2. When used for the construction of lightweight concrete, additional reinforcement will be required. Lightweight concretes include materials such as foam concrete, cinder concrete, expanded clay concrete. They can collapse if the roof is not supported centrally on them. To evenly distribute the load, a monolithic reinforced concrete belt is poured along the edge of the walls. During work, a special wire, studs or bolts are laid in it, on which the Mauerlat will be fastened.
3. For brick means, it is possible not to provide a reinforced concrete belt. In this case, to connect with the strapping beam, a wire is inserted into the masonry, which is then wrapped around the Mauerlat and twisted. The second option - one row before the walls are cut, wooden blocks impregnated with an antiseptic are brought into the masonry from the outside. Such plugs and Mauerlat are fastened with staples. It is also possible to use studs and bolts, for fixing which will require pouring a monolithic belt.

An important point is waterproofing.

When installing, it is important to provide roofing material, linokrom or waterproofing at the junction of concrete or brick with wood. This is required to prevent the wood from rotting on contact with material of a different moisture content.

rafters

After fixing the Mauerlat, rafter legs are installed. Their cross section is selected depending on the pitch of the supporting beams, their span, snow load and type of coating. When installing a frame under a metal tile with a step of 60 cm, it is recommended to follow the following recommendations, depending on the span:

• 3 m - 4x15 cm;
• 4 m - 5 \u003d 15 cm;
• 5 m - 5x17.5 cm;
• 6 m - 5x20 cm.

Table of average values ​​of rafter legs

These are average values, in order to perform a more accurate calculation, it is better to contact a specialist or study additional literature.

There are two ways to fasten the rafter legs to the Mauerlat:

• with a notch;
• without her.

Fastening rafter legs to the Mauerlat with and without a notch

In the first case, they washed down on the strapping beam, in the second, a special plank is nailed to the rafters, which becomes a persistent bar. Further, for both methods, the work is performed in the same way. With the help of metal corners, the inclined beam is fixed so that it does not move relative to the design position along the Mauerlat. Additionally, nails are driven in at an angle.

Scheme of fastening rafters with wire and brackets

In addition, you will need to fasten the rafter to the wall. The implementation of this measure is provided for in the regulatory documents. You can do this in two ways:

• on brackets (suitable for wooden buildings);
• using wire twisting (a more time-consuming option, but the only one possible for stone houses).

You can perform fastening according to the norms through one leg. This is necessary for a more secure attachment of the roof to the box of the house.

If you do the work correctly, you can not worry about its condition even in the strongest winds.

Racks, ties, struts

Such elements are most often made of boards. The optimal thickness is in the range of 32-50 mm. Racks are an exception. Here you can use boards with a thickness of 50-100mm. Fastening is carried out on studs or using support bars.

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The calculation of the truss system should be done not after the construction of the box of the house, but even at the stage of manufacturing the building project. It must be remembered that for very responsible and prestigious buildings, it is recommended to order such work from professional architects, only they will be able to perform the correct calculations and guarantee the duration and safety of the operation of the structure.

Although this is one of the simplest types of systems for residential buildings, there are several types of construction. Diversity allows you to increase the options for using roofs in the construction of houses according to standard or individual exclusive projects.

Type of gable roof truss system	Architectural features and brief description
	The most commonly used option has two completely identical rectangular slopes. The loads between the individual elements are distributed evenly, regardless of their location. The number of additional stops is not limited, a specific decision is made depending on the plans for the use of attic space. Calculations can be done using free programs hosted on construction sites.
	The skate is shifted to one of the sides of the house or slopes with different angles of inclination. The roof truss system is more complex for calculations. If in a simplified version one slope can be calculated and the data obtained automatically applied to the second, then this option cannot be used for an asymmetric truss system. Advantages - original appearance. Disadvantages - the complexity of calculations and installation and a decrease in the used attic space.
	Most often used during the construction of attic spaces, it allows you to significantly increase the volume of attic spaces. Calculations on complexity belong to the middle category. Rafter system with an external break. Rarely there are systems with an internal break, except for the original appearance, they have no advantages.

Structural elements of the truss system

We will give a list of all the elements that need to be calculated for each specific case.

The simplest element of the truss system can be made from timber 150 × 150 mm, 200 × 200 mm or boards 50 × 150 mm and 50 × 200 mm. On small houses, it is allowed to use paired boards with a thickness of 25 mm or more. Mauerlat is considered an irresponsible element, its task is only to evenly distribute point forces from the rafter legs along the perimeter of the facade walls of the building. It is fixed to the wall on a reinforcing belt using anchors or large dowels. Some truss systems have large bursting forces, in these cases the element is calculated for stability. Accordingly, the optimal methods for fixing the Mauerlat to the walls are selected, taking into account the material of their masonry.

Bar prices

They form the silhouette of the truss system and perceive all the existing loads: from wind and snow, dynamic and static, permanent and temporary.

They are made from boards 50x100mm or 50x150mm, they can be solid or extended.

The boards are calculated according to the resistance to bending, taking into account the data obtained, the species and types of wood, the distance between the legs, and additional elements to increase stability are selected. Two connected legs are called a truss, in the upper part they may have puffs.

Puffs are calculated for stretching.

Runs

One of the most important elements of the gable roof truss system. They are calculated for maximum bending forces, they are made of boards or timber of the section corresponding to the loads. A ridge run is installed at the highest point, side rails can be mounted on the sides. Run calculations are quite complex and must take into account a large number of factors.

They can be vertical and inclined. Inclined work in compression, attached at right angles to the rafters. The lower part rests against floor beams or concrete slabs, options for resting on horizontal beds are acceptable. Due to the stops, it is possible to use thinner lumber for the manufacture of rafter legs. Vertical stops work in compression, horizontal stops in bending.

lying down

They are laid along the attic space, rest against several load-bearing walls or interior partitions. The purpose is to simplify the manufacture of a complex truss system, the creation of new points for transferring loads from various types of stops. For beds, beams or thick boards can be used, the calculation is made according to the maximum bending moment between the support points.

crate

The type of lathing is selected taking into account the technical parameters of the roofing and does not affect the performance of the truss system.

What crate is needed for corrugated board? When to mount wooden, and when metal? How to choose the right step of the crate and what factors should be taken into account?

Prices for building boards

Building boards

Stages of calculating a gable roof

All works consist of several stages, each of which has a great influence on the stability and durability of the structure.

Calculation of the parameters of the rafter legs

Based on the data obtained, the linear parameters of lumber and the truss pitch are determined. If the loads on the rafters are very large, then vertical or angular stops are installed to evenly distribute them, the calculations are repeated taking into account new data. The direction of the impact of forces, the magnitude of torque and bending moments change. During the calculations, three types of loads should be taken into account.

1. Permanent. These loads include the weight of roofing materials, lathing, insulation layers. If the attic is in use, then the mass of all finishing materials of the inner surfaces of the walls should be taken into account. Data on roofing materials are taken from their technical characteristics. The lightest of all metal roofs, the heaviest of all are natural slate materials, ceramic or cement-sand piece tiles.

   

2. Variable loads. The most difficult to calculate efforts, especially at the present time, when the climate is changing dramatically. For calculations, data are still taken from reference books of SNiP of an outdated model. For his tables, information was used fifty years ago, since then the height of the snow cover, the strength and the prevailing direction of the wind have changed significantly. Snow loads can be several times higher than those in the tables, which has a significant impact on the reliability of calculations.

   

   Moreover, the height of the snow changes not only taking into account the climatic zone, but also depending on the location of the house on the cardinal points, the terrain, the specific location of the building, etc. Data on the strength and direction of the wind are just as unreliable. Architects have found a way out of this difficult situation: data is taken from outdated tables, but a safety factor is used in each formula to ensure reliability and stability. For critical roof systems on residential buildings, the standard is 1.4. This means that all linear parameters of the system elements increase by 1.4 times, and this increases the reliability and safety of the structure operation.

   

   The actual wind load is equal to the figure in the region where the building is located, multiplied by the correction factor. The correction factor characterizes the features of the location of the building. The same formula is used to determine the maximum snow load.

   

3. individual loads. This category includes specific efforts that affect the gable roof truss system during an earthquake, tornado and other natural disasters.

The final values ​​are determined taking into account the probability of the simultaneous action of all the above loads. The dimensions of each element of the truss system are calculated using a safety factor. According to the same algorithm, not only rafter legs are designed, but also lintels, stops, stretch marks, girders and other roof elements.

The frame format stands out among a number of types of roofing. It can be done in quite different ways, but in any case, you will need to calculate the rafters and install them according to all the rules. With proper knowledge of the problem, you can solve it on your own without resorting to specialists.

Features and forms of the roof

The frame roof can only be installed with spans no longer than 1220 cm, while the gap from one truss to another is a maximum of 0.6 m. The dimensions of the frame fragments are determined by the span distances and the calculated snow load. Rafters can be either freely installed or accepting loads from attic elements. In the case of a broken roof, it is possible to provide a ceiling height sufficient for a residential attic, and it will look best on a square building.

The multi-gable roof is considered the most complex and hardly accessible variation for amateur builders. A balanced truss system effectively withstands even very high loads, while having an excellent "appearance". Since the slope is steep, the risk of snow retention will be minimal. But at the same time, all structural elements will have to be calculated very carefully, and a lot of waste will appear in the process. In addition, the valley will have to survive exposure to a significant amount of snow.

Purpose and types of systems

Mauerlat can be used in a variety of rafter systems. The mass of the roof of the house varies depending on the area occupied by the slopes and the materials used. But in any case, the load created is very solid. When there is a ridge on the structures, a truss frame must be provided, with legs resting against the walls. Force is applied along several vectors at once, and in the cold season, the accumulation of snow only exacerbates the problem.

Mauerlat is designed to eliminate this shortcoming and prevent the destruction of the walls. This word means a beam of significant section, which can be both wooden and steel. In most cases, they take the same material that was used to form the rafters, but be sure to achieve the continuity of the strapping or create strong and especially stable joints. The use of Mauerlat is abandoned only in log houses or in buildings built using frame technology - and even there there are parts that perform a similar task. When it is not possible to make a non-breaking block, all fragments must be exactly the same length.

A T-shaped roof is characterized by a tie-in of two wings at a certain angle. Because of this, it is necessary to form a valley. The outer rafters will rest against the support boards. In addition to them, there will also be basic parts that are directly fixed to the wall. In order for everything in the valley to correspond to the task being solved, wooden elements 3.8 cm thick are used. The crate is supposed to be made monolithic, the coating is attached to it with clamps every 50 cm. steel, you can slightly reduce this figure.

A reinforcing belt is often equipped under the Mauerlat. This is especially important if you plan to insulate the roof and provide reliable waterproofing. Such a belt is formed from the same mixture that is used to build the foundation. Completely the entire formwork is poured with concrete in one step, the slightest individual layers are unacceptable. In the aerated concrete wall, intermediate jumpers are cut down at the top line of blocks - and a practical gutter immediately appears. The Mauerlat is attached either with the help of a knitting wire, or with reinforcing bolts (but they will not help in any way without a reinforcing belt), or with building studs.

Having dealt with the support for the rafters, you need to find out what they can be, and what is more correct to use to support the roof. Hanging rafters are used if there is no main wall inside the building, their support points are located exclusively on the outer contours.

Such supports were in demand during the construction of:

• residential buildings with one span;
• production facilities;
• various pavilions;
• attic.

This option should not be underestimated, thanks to engineering developments, suspended rafters are able not to bend, covering spans of 15–17 m. But it is important to understand that they gain all their capabilities only in close interaction with other details. You will have to use puffs, and grandmas, and crossbars. The simplest truss is made of two beams connected in the upper position; in configuration, such a device is close to a triangle. The horizontal connection of the frame parts is provided by a tightening (a beam made of wood or a metal profile).

Due to the tightening, the transfer of thrust to the walls is excluded, while the force applied in the horizontal plane is suppressed. The outer walls experience the action of only those forces whose vector is oriented vertically. Builders do not always place a puff at the very bottom, often it is set at the very ridge. In preparation for the construction of the attic, this element is most often placed higher than the base of the rafter legs. Then it will be possible to make a floor, on the ceiling of which you will not have to beat your head with any careless movement.

Hanging rafters for spans longer than 6 m must be reinforced with hangers and braces. In this case, the monolithic puff is replaced by one assembled from a pair of connected beams. In the classical scheme (triangular hinged), the grassroots bases abut against horizontal parts. For the normal functioning of the system, it is required that the height of the ridge is at least 15% of the span of the trusses. The rafters act on the bend, but tightening does not allow them to move to the sides. In order for the beams to bend less, the ridge knots are cut in with the expectation of eccentricity (the occurrence of a bending force opposite in vector).

Mansard attics are built for the most part with the help of triangular arches on three hinges, and the puffs are assigned the function of floor beams. The components of the tightening are bolted by means of an oblique or direct cut. Raised tightening can also be used in the construction of rafters under the attic. The higher it rises, the more the ceiling can be raised. But it is important to remember that at the same time, the loads on all elements also increase. The transfer of forces is carried out on the Mauerlat with the help of a movable mount, which dampens dimensional changes due to changes in humidity and temperature.

The rafters can be subjected to uneven loading, since it is higher on one side. This leads to a shift in the same direction of the entire system. You can eliminate such an unpleasant effect if you take out the rafters beyond the contour of the walls. The tightening with such a decision ceases to be a support, it transfers either tensile effects (if an attic is being arranged), or stretched-bending ones (when an attic is being built). Hinged arches with the inclusion of a crossbar differ from the previous version by replacing the sliding support with an identical one in function - rigid. Due to the change in the type of supports, the type of stresses generated also becomes different, the rafter system turns into a spacer.

The puff is formed in the upper lobe of the arch. Its purpose is to endure no longer a stretch, but a compressive effect. Additional tightening, reinforcing the crossbar, is needed with a significant load. Arches with suspensions and struts complement the arch systems with headstocks. Such a system is needed for significant spans (from 6 to 14 m). The struts that correct the resulting bend must rest against the headstock. Regardless of the specific type of truss system, it is necessary to carry out all the details and their connections with each other as clearly as possible.

Not always hinged rafters can perform the task. Then the slanting elements come to the rescue. This type of rafters is used under hip roofs and under roofs equipped with a valley. Their length is longer than in the usual case. In addition, they become supports for the shortened rafters of the slopes. That is why the load on the rafters is about 50% more than in other structures.

Thanks to the increased length, it is possible to:

• resist significant impacts;
• form beams without cuts;
• bring the parts to a single size by pairing the boards.

To build a hip roof with many spans, the diagonal legs are provided with supports. Such supports are made in the form of standard struts or racks of timber, or a pair of connected boards. Support through a lining made of wood and a waterproofing layer is made directly on the reinforced concrete floor. The struts are placed at an angle of not less than 45 and not more than 53 degrees, at the bottom such a detail rests on the beds. The angle of installation is less important than the ability to fix parts of the rafters at the point experiencing the strongest load.

Sloping rafters placed in openings up to 750 cm should be held by struts only in the upper lobe. With a length of 750 to 900 cm, a truss truss or rack is additionally mounted below. And if the total span length exceeds 9 m, then for maximum reliability in the middle you need to put a rack, no other support will do. If the selected floor is unable to withstand the load, it will have to be reinforced with a beam. The type of support in the ridge is determined by how many intermediate supports are used, what they are, how the key layered rafters are made.

In addition to the type of rafters, you need to clearly understand their material. Both wooden and metal structures can be good, but only each in its place. Even the high strength of the metal does not allow to push the usual wood. The tree has proven its benefits for thousands of years, and now it is even gaining popularity due to its excellent ecological characteristics. Boards and timber can be bought at an affordable price, and if something has not been taken into account, it is always easy to saw off the desired fragment or build up a part right on the construction site.

Sometimes there are problems associated with the operation of the created structures. Wooden rafters will have to be carefully treated with antiseptics, as well as means that block the development of mold colonies and insects. The combustibility of wood is suppressed due to regular processing, and in addition, it is too difficult to find the necessary components for slopes longer than 7 m. Before installation, the walls are laid with a mauerlat, made from a log frame or based on a block of timber. The thickness of the structures is at least 180 mm, this is the only condition for a uniform distribution of loads.

Metal rafters are inevitably heavier than wood rafters for the same section. Therefore, the walls need to be strengthened, the work on their construction becomes more expensive and longer. It will not be possible to mount metal blocks manually; cranes will be required. It is impossible or very difficult to adjust the dimensions, the geometry of the rafters, so you will immediately have to build the walls as accurately as possible and eliminate errors during their construction. The slightest mistake can make an expensive block almost useless in practice.

Metal rafters are connected by welding, and welded joints are inevitably weakened, as corrosion develops rapidly there. The cost of the work is very high, and when performing them, it is necessary to comply with the requirements of fire and electrical safety. But there is such an indisputable advantage as the ability to support a roof slope from 700 cm and longer. If you use a special anti-corrosion paint, the durability of metal structures is fully guaranteed. All these advantages allow you to quickly and comfortably build industrial buildings with a significant height and length of spans.

How to choose: what to consider?

The truss system should be chosen as correctly and clearly as possible.

When looking for a suitable solution, you need to pay attention to the following points:

• strength;
• the ability to support the slopes and the roof as a whole of a certain size and geometry;
• creating a positive aesthetic image of the building as a whole.

Technical parameters take precedence. Even the most beautiful structures that follow the principles of design will not show their positive qualities if they last too little. Experienced builders always analyze the average annual and seasonal temperatures, the financial capabilities of developers, the maximum possible wind speed and the severity of the overlying roof. The future use of the under-roof space and the scale required for it are also taken into account. Wind, snow and rain should not be underestimated, since these factors can have a very strong effect on the roof, and through it on the rafters.

If it is reliably known that a particular area is characterized by heavy snowfalls, the minimum slope angle is impractical. This point is even more relevant when using flat roofs. Under the pressure of accumulating precipitation, the frame can rapidly deform or water will pour inside. Another thing is when a certain region is often subject to the arrival of cyclones and the strong winds they bring. Here the slope should already be made smaller, then the situation with the disruption of individual structural elements will be practically excluded.

Mistakes can be avoided if you look at houses already built nearby and operated for a long time. By accurately reproducing their roof structure and the rafter system interconnected with it, one can best take into account local specifics. But not everyone follows this path, sometimes the task is to develop an exclusively original project. Then you will have to carefully collect the initial data, carry out scrupulous calculations. In the absence of special knowledge, it is better to attract qualified performers to help.

After analyzing the total load created by wind and snow, it can sometimes be found that certain parts of the truss complex need selective reinforcement. When assessing the required angle of inclination of the roof, attention is also paid to the type of coating used. A heavy metal tile or corrugated board with a very large slope can spontaneously slide down, you have to additionally fasten them, complicating your work and increasing the cost of installation. In addition, certain materials have a tendency to retain water or become soaked with it, which can only be combated by making the slope steeper. Creating a good roof and truss system that meets such conflicting requirements is not always accessible to non-specialists.

What does it consist of?

The structure of the truss system, as you can see, is quite complex and even contradictory. Each part of this design has a strictly defined role. So, Mauerlat is a long bars of coniferous wood, and strictly resinous wood is used for work. Such elements are laid out along the external load-bearing walls, attached to the base with anchors or rods of a special design (threaded). This part transfers the load from the roof to the wall.

Next comes such a device as a rafter leg. Under this name appears a wooden beam used to build the contour of the slopes. The shape of the structure is always triangular, because it is the best way to help the roof withstand the destructive effects of winds, snow and other atmospheric processes. Rafter legs are placed at uniform distances along the entire roof, the step cannot exceed 120 cm.

The bed is also of some importance for supporting the roof - this is a wooden block that replaces the Mauerlat in some cases. Beds are placed on the internal supporting walls. They turn into the basis of the roofing triangle. Thanks to them, the slopes do not crawl under their own weight. And it is also worth mentioning about the racks - these are bars with a square section placed vertically. They perceive the pressure exerted downward by the ridge assembly and transmit it mechanically to the inner bearing plane. Sometimes the racks are under the rafters.

Struts are designed to strengthen the entire structure of the roof, they connect the legs and beds into one whole. This detail is shaped like a rhombus. The community formed by the puff and struts is called the farm. In addition to them, you also need a crate, which is thin boards stuffed at right angles to the legs of the rafters. It helps to keep the rafter legs as a single system. Absolutely any roof covering is attached to the crate.

Under soft materials, the crate should be made inseparable, and plywood is considered the best tool. At the very top is a ridge, which logically and physically completes the roofing triangle. The connection of a pair of opposing legs of the rafters is provided by a square piece of wood which prevents the entire roof from collapsing. And at the very bottom of the pitched roof there is an overhang, which extends approximately 0.5 m from the perimeter. Thanks to him, the streams of rain leaving the roof do not flood the outer bearing planes and do not harm them.

Fillies are used only in the situation when the rafter legs cannot be made along the length that would allow organizing the overhang. Connecting with boards of reduced section effectively solves this problem. For fastening the wooden elements of the rafters, it is most often recommended to use clamps, staples. It is undesirable to use nails, because the tree pierced by them becomes weak and fragile after a few years. Therefore, if professionals use connections made directly on the construction site, they use bolts.

But even a bolted connection weakens building structures, albeit relatively slightly. The strongest are the connections with the help of clamps or staples made of metal. Only their industrial production can maximize the quality of products, since deviations from the norms and deterioration in quality are excluded only under strictly standardized and fully controlled conditions. You can assemble a truss structure from completely finished trusses very quickly, there is no risk in using it. Another thing is that it is required to collect information about the necessary characteristics as accurately as possible and transfer it to the manufacturer without distortion.

In addition to these elements, the truss system borders on the valley. This is the name given to a special connection of a geometrically complex roof at points where its trajectory changes. The difference from the ridge is that in such places the roofing parts form a negative angle. The technical essence of the product lies in the fact that the gutter helps to divert liquid to the side. The more complex the configuration, the greater the number of such gutters should be.

The cornice beam serves to abut a strut against it, the other end of which rests against the frontal board, while the dropper is not deformed and its configuration is not distorted. Wind connections are those elements of the truss system that transfer the load created by the wind from the roof to the foundation. They not only increase the overall stability of the structure, but also help to avoid tipping over in case of instability of individual parts. The roof will retain spatial rigidity even with very strong winds.

Horizontal wind connections are such elements as:

• braces;
• parabolic puffs;
• complexes of conventional puffs;
• trusses, complemented by a cross-shaped lattice.

Vertically, the preservation of characteristics under strong air pressure is ensured by wind supports and beams. Sometimes a monolithic reinforcing core is used. Engineers have come up with many other options for designing a wind connection. It is provided with frames and semi-frames, pinched props. In small buildings, rigid (resisting compression) or stretched diagonals are used, some covering two spans at once. The location of each of the elements is accurately reflected in the project documentation.

It is not so difficult to understand the qualitative characteristics of truss systems and their composition, if you show care and diligence. But it is equally important to calculate the quantitative parameters of these systems. If you do not do this or make the calculations incorrectly, you can either spend too much money, or encounter leaks, even with the destruction of individual elements.

• roof bends;
• average annual snow mass;
• unevenness in its distribution along the slopes, depending on the steepness of the slope and the wind rose;
• wind transfer of already fallen snow;

• descent of snow and ice masses, runoff of liquid water down;
• aerodynamic characteristics and windage of the structure;
• differences in the strength of the impact on individual points.

It is not so easy to calculate everything necessary, moreover, by simulating realistic situations and including a reasonable margin of safety in the project. Moreover, it is necessary to pay attention to the addition of various loads, to their cumulative effect. But still, any customer is quite capable of evaluating the quality of the work of designers. The loads applied to the truss systems are divided into three key groups: main, additional and extreme.

The main category includes:

• stable factors - the severity of the roof and roof structures, additional elements installed on top of them;
• long-term effects - snow, temperature;
• periodically changing factors - full calculations of snow and temperature effects, taking into account all the subtleties.

An additional group is the pressure exerted by the wind, builders and repairmen, ice and rain. The extreme category includes all natural and man-made emergencies that may occur in a particular place. Their level is predicted with a margin to ensure the exclusion of unpleasant consequences. When calculating the frame roof and the structures under it, the ultimate load is taken into account, if applied, the entire structure crumbles. Additionally, an indicator or a group of indicators is given, upon reaching which various deformations inevitably appear.

The snow drift coefficient reflects how much more snow will be deposited on the lee side and in front of objects (parts) that block the air flow. In problem areas, you will have to bring the rafters as close as possible and thoroughly calculate the required thickness of the front material. The most accurate assessment of all parameters can only be given by multiplying any received figures by the reliability factors. As for the wind, the force developed by it is aimed at dropping steep roofs and lifting from the leeward section of a flat roof. We must not forget that the air flow acts simultaneously on the facades and on the roof slopes.

When hitting the facade, the air breaks up into two waves: one goes down and is no longer of interest, and the other tangentially presses the roof overhang, trying to raise it. The action on the slope occurs at a right angle, this area is pressed inward. At the same time, a vortex is formed, which tangentially affects the windward sector of the ramp. This vortex bypasses the ridge and begins to create lift already applied to the leeward segment. For your information: when calculating the mass of the roof, you need to take into account the severity of the rafters, insulation, waterproofing and vapor barrier.

The standard load per 1 square meter of the roof is up to 50 kg, regardless of its size and other significant circumstances. By changing the distance from one rafter leg to another, you can set the actual distribution of loads on them. According to most experts, indicators from 60 to 120 cm will be acceptable values. But on an insulated roof, it is worth choosing such distances that are equal to one sheet or roll of insulation materials. At the same time, it should be borne in mind that among several suitable options for arranging rafters, the one that gives the best effect with the minimum consumption of materials used is preferable.

When calculating the loads carried by the rafters, they always look at the fact that they do not exceed the ultimate endurance of the roofing material. After all, there is no point in such an excess. If, under the planned impact, the roof will still begin to sag, it is impossible to talk about a solid result. In calculations, the payload from structures connected to truss trusses is calculated according to the contact area that is plotted on the drawing. Such structures include ventilation chambers, attic and ground floor ceilings, and water tanks placed on the roofs. In addition to the amount of pressure on the rafter system, the sharpness of the roof slope is also calculated.

Tilt angle: value

On forums with consultations of specialists and in professional literature, one can find references to three units of measurement of inclination at once. In addition to the usual and expected degrees, there will be percentages and ratios between the parties. Often they get along together even within the same publication or instruction from the manufacturer of roofing materials. But in fact, there is nothing mysterious in this, any consumer can understand the essence. Under the angle of inclination of the roof, experts understand the angle that occurs at the intersection of the horizontal with the roof slope.

In this case, there can be no obtuse angles in principle. Moreover, you can meet a slope steeper than 50 degrees only in decorative elements, all kinds of turrets. The only exceptions to the general rule are the slopes on the lower rows of the rafters of the attic roof. In all other cases, the angles range from 0 to 45 degrees. The relative proportions of the sides are calculated as the ratio between the height of the slope and its projection on the horizontal. This indicator is equal to half the span for a uniformly constructed roof with a pair of slopes.

On a shed roof, the proportion is equal to one, but in more complex configurations, you still have to carry out all the calculations and estimates yourself, without starting from ready-made values. The slope angle is usually expressed as a fraction, with the numerator and denominator separated by a colon. But when the resulting numbers cannot be rounded to whole numbers, it is recommended to use percentages: they simply divide one by the other and increase it a hundred times. Flat roofs are those that have a slope of no more than 5 degrees; a slope of 6–30 degrees is recognized as small, and all other roofs are considered to be steep. The flat design drastically increases the usable area and is quite wind resistant, but it will need to be manually cleared of snow and strengthen the waterproofing to the limit. The slope is necessarily consistent with the specific material, and the required values ​​\u200b\u200bcan be found in the instructions from the manufacturer. In order to calculate even the most complex and bizarre roof configurations, they are mentally divided into triangles and the angle is calculated separately in each.

Step, length and section of rafters

When it became clear how long the slopes are, what angles formed by these slopes with a horizontal plane, it was time to do the actual calculation of the rafters. If the roof frame is made of a 5x15 cm timber under a metal tile, the mounting pitch sways from 0.6 to 0.8 m. As the slope grows, the gap also increases. If the roof slopes at 45 degrees, you need to put rafters every 800 mm, and for slopes of 75 degrees, you can add another 200 mm.

The next important parameter is the length of the rafters. It is closely related to the step: if the blocks are made long, they are brought together as much as possible, and when a single part is shortened, they are moved apart. When calculating the step of the crate, they proceed from the type of tiles laid on top and from the fact that an integer number of rows should be laid out on each slope. If you get a fraction, it is better to round, reduce or increase the indicator a little. The rafter legs under the metal tile, the cross section of which is 15x5 cm, range from 65 to 95 cm. You cannot increase the step when the cross section of the crate is 3x5 cm.

In order for the insulation to be better ventilated, rows of holes with a diameter of 1–1.2 cm are prepared in the region of the upper edge of the rafters. Ordinary rafters under the corrugated board go every 0.6–0.9 m. with significant cross section. The crate under the corrugated board is assembled from boards with dimensions of 3x10 cm, which are placed at intervals of 0.5 m. The interval must be calculated according to the height and thickness of the materials.

With all the revealed shortcomings of slate, it remains widely in demand. Under the slate roof, rafters with a section of 5x10–15 cm are mounted, 60–80 cm apart from each other. Most often, an average distance of 0.7 m is recommended. Pauses between parts of the crate are calculated according to the steepness of the material. On relatively flat areas, the support of 4 pieces of wood justifies itself. If the roof is made steeper, put 3 bars, separated by 63–65 cm.

We must not forget that due to the responsibility of the truss system, it is better to leave a margin of safety than to make an unreasonably weak type of rafters. For their manufacture, timber is used, dried to a maximum of 15%. A non-edged board of the same dryness can serve as a replacement for a beam. Under the ceramic tiles, a 5x5 cm timber crate is used. In the places marked according to the calculated distance, slate nails or simple self-tapping screws are used.

Installation: technology

The construction of the roof involves the use of a standard range of carpentry tools and an electric drill. If metal structures are used, a grinder will be required for precise cutting. Remember that it is impossible to process metal tiles or corrugated board with it, this can damage the material. A hipped roof without racks is made using puffs that reinforce the structure.

In the hip version, it is necessary to strengthen the runs running diagonally. Paired boards and a particularly strong timber are assigned to them. Connection points always have a support (stand), and the main support is placed about a quarter of the length separating the large rafters from the ridge. Under the gables on a gable roof, rafters of a shorter length are always made. But under the main part of the four-slope structure, extremely long parts can be placed, even more than 7 m. To keep them securely, either a rack is used that transfers stress to the ceiling or a sprengel.

The first step in creating rafters under a broken roof is the formation of a support complex in the form of the letter P. It rests on the floor beams and is held by rafter legs. Next, they put three or more runs, two of them are brought to the corners of the frame, and the rest are placed in the middle of the overlap. The final step in raftering is fixing the legs. It is desirable to make truss systems according to a pattern - to connect two boards that are the same length as the rafters, and pin them to each other with a nail. The template is placed with its edges at the points of attachment of the rafter legs and fixed with a cross member.

An additional template (this time plywood) will help to make a mounting saw. Farms are attached to the Mauerlat, starting from the extreme ones. In order not to confuse with the attachment point of the ridge, the tops of these trusses are tied with a straight rope. The massiveness of the puffs increases as you approach the ridge. If the truss elements are bolted, washers or plates should be used. This will keep the nuts from digging into the wood.

How to install the rafters with your own hands, see the video below.

Housing construction today is so diverse that sometimes the structures being built take on a completely bizarre fantastic look. In particular, architects like to experiment with a roof that is made transparent, and in the form of tree foliage or a flower, and a skateboard area - in general, their imagination is completely limitless. But we are somehow closer to simpler options, for example, a gable roof. We will talk about what it is and what the gable roof truss system consists of in this article.

It is this type of construction that is most popular in the construction of residential buildings, since with its help a sufficient attic space is created that does not require additional insulation. In addition, a gable roof is not as difficult to install as, for example, a four-slope one, and also does not require huge investments for its installation.

A gable roof is a structure consisting of two rectangular planes connected in the upper part with each other, and in the lower parts with the walls of the house. The end part of such a building is usually built from the same materials as the walls of the building, sometimes the entrance to the attic is also built here.

Recently, it has become very popular to build an additional room in the attic space, often used as a summer guest room. The installation of a gable roof truss system and the subsequent insulation of the resulting room allow you to create a full-fledged room in which you can live both in summer and in winter.

All the advantages of gable structures

The main components of a rafter roof are the Mauerlat and rafter legs, in addition, various struts, racks, crossbars, stops and battens help to make the structure durable and reliable. The gable roof drawing also includes a layer of insulation, vapor barrier, waterproofing and the roof itself. Thanks to all these elements, a gable roof has several advantages:

• simplicity of technical execution;
• low probability of leaks, as the design is one-piece;
• high profitability, because a relatively small amount of materials is spent on its construction;
• the possibility of arranging a full-fledged residential area in the attic;
• ease of repair in case of defects;
• high strength and wear resistance.

The angle of inclination is an important component of a solid roof

The value of the angle of inclination is determined depending on the weather conditions of the region of residence, on the characteristics of building materials and on architectural requirements.

For example, in areas where heavy rainfall is normal, the roof is always made at a high angle. This is necessary so that snow masses accumulate on its surface as little as possible, which can lead to the collapse of the building. In regions with the strongest winds, sloping roofs are most often built, since the wind pressure on such structures is significantly reduced.

In whatever climate zone the dwelling is located, the gable roof truss system cannot be built at an angle of less than 5 degrees!

Recommendations for calculating the area of ​​\u200b\u200ba gable roof

Roof area calculation - picture

Calculating is not as difficult as it might seem at first glance, but this painstaking process requires perseverance - all data must be double-checked at least three times. Agree, no one wants to spend money on building materials that are completely unnecessary to him.

In some cases, measuring the roof area can be complicated by some "obstacles", for example, the presence of an attic or an unusual shape of the roof - here it is unlikely to be possible without the help of a specialist. We will consider the calculation of the area on the classic version of the roof with two slopes:

• First, we determine the length of each slope, it is equal to the distance between the lower edge of the ridge and the extreme point of the eaves;
• We take into account all elements of the roof: parapets, overhangs, firewall walls and other structures that create additional volume;
• We determine the type of roofing material for which we will calculate the area;

It should be borne in mind that in the case when the roof is covered with a rolled or tiled type of material, the length of each slope will become less by about 0.7 m.

• Elements such as ventilation shafts, windows and chimneys are not taken into account;
• When, taking into account all the details, the area of ​​\u200b\u200beach slope is calculated, we calculate the slopes: we multiply the elements of the slopes by the cosine of the angle of inclination of the roof, and we calculate the area only by overhangs.

For the greatest convenience of calculation and obtaining correct data, it is best to calculate the area of ​​\u200b\u200beach element separately, and then add the resulting numbers.

The roof area has been calculated, the roof has been decided - it remains only to understand in detail all the structural elements, such as rafters, Mauerlat, side / ridge runs, struts and braces, as well as diagonal connections, after which you can proceed to the calculation of a specific type of truss system.

Hanging and layered rafters

Of course, such a structure as a do-it-yourself gable roof truss system in the minds of many seems to be something very complex and time-consuming. But if you carefully consider the construction of such a structure and study the necessary material in advance, the question will remain only in the “number of hands” that you will need for the construction process.

Let's start with such a component of the roof as hanging rafters. These bars have only two points of support - the walls, so the main loads acting on them are bending and compression. The weight of the roof, as well as the action of snow and wind, is transferred to the walls through the hanging rafters so that this pressure is compensated, the rafters are connected with a puff made of metal or wood. You can place it at any height, but the higher it is, the stronger and stronger it should be.

Laminated rafters are bars that have an intermediate support resting on the inner wall of the house. The main effect on such a structure is bending. The supporting structure of the roof is made only of layered supports, when the distance between them is not more than 6.5 m.

The same roof can consist of layered and hanging rafters at the same time: where there is an intermediate support, layered rafters are erected, and where not, hanging ones.

Mauerlat and runs

The lower part of the rafters in houses built of timber rests on the upper crown, and in buildings made of brick or foam concrete, on a special timber called Mauerlat. For its installation, a waterproofing material is placed on the inside of the load-bearing wall, on which the Mauerlat lies. The length of the beam can be equal to the length of the wall of the building, or it can be adjusted to the size of each rafter leg - this is even more economical.

Ridge run - a bar to which the upper parts of the rafters are fixed. That is, it is the ridge of the roof. Its length depends on the length of the roof, so both a solid array and several logs are used for its construction.

Side runs are needed for additional support of the rafters, their emphasis is also placed on the gables of the building. The ends of such purlins are sometimes released outside the gables, thus, unloading consoles are obtained, as a result, the pressure of the roof on the central part of the purlin is significantly reduced.

If the roof of a building is built from heavy materials, such as natural tiles, then the side girders are made in the form of a rocker, for this the logs are slightly hemmed and bent.

A little more about the important elements of the roof

Diagonal overlap - picture

Additional diagonal ceilings are called braces, with the help of which the gable roof truss system is strengthened, and the gables' wind resistance characteristics are increased. The upper part of the braces rests against the gables, and the lower part rests against the central ceiling.

Struts are necessary to reduce the load on the rafter legs, their installation at an angle of 45 degrees and above can significantly reduce wind loads and snow mass pressure on the roof, therefore, in the northern regions of the country, such roof elements are simply irreplaceable.

If the roof consists of slopes of different areas, then their angle of inclination will not be equal. Therefore, for the greatest strength of such a structure, vertical racks are erected at the “fracture” points, on which the side runs are supported. Most often, such structures are built for attic rooms.

In areas characterized by constant strong winds, truss systems are necessarily reinforced with diagonal ties, which are boards with a thickness of 25 to 50 mm. The lower edge of the board is fixed to the heel of the rafter leg, and the upper edge to the middle of the opposite rafters.

Correct calculation of materials for the gable roof truss system

Do not be afraid to make all the necessary calculations yourself, because the dimensions of a gable roof, especially if it has the shape of an isosceles triangle, anyone can calculate without deep mathematical knowledge.

So, let's consider the calculation of the gable roof truss system using a specific example. The house for which it is required to build a similar structure has a width (W ir) of 4 m, a length of 6 m, and the angle of inclination of the rafters (Y) should be 120 degrees. The roof will be built of metal tiles, the distance between the rafters is planned to be 1 meter.

First, we find the height of the central support (C):

C \u003d 0.5? W ir / tgY / 2 \u003d 0.5? 4 / 1.73 \u003d 1.2 m

The length of the rafter leg (Ds) is calculated by the following formula:

Ds \u003d 0.5? W ir / sinY / 2 + 0.5 \u003d 2.8 m

0.5 in this formula is an allowance for the roof visor, it must be taken into account without fail!

Roof area (Pk) \u003d D? Ds? 2 \u003d 33.6 m 2

It turns out that exactly this number of sheets of metal tiles you will need for the roof.

The distance between each lath of the crate (Rp) is conditionally taken as 35 cm, which means:

Lathing length = Ds / Rp? D? 2 \u003d 96 linear meters

With a house length of 6m and a distance between the rafters of 1m, we need 7 rafter legs, which means that the amount of timber for them and for the Mauerlat is no less than:

Beam length \u003d (2? Ds + W ir + C) \u003d 75.5 p.m.

The required amount of other materials is calculated in the same way. When all the calculations have been made and the required amount of building materials has been purchased, we proceed to the direct construction of a gable roof.

We build a gable roof with our own hands

So, now we have come close to such a moment as installing a gable roof truss system. This process begins with the construction of beam ceilings.

There are only two mounting options:

• If the attic space is not planned to be used as housing, then boards of size 50? 150 mm.
• To equip the attic, you will already need a beam with dimensions of 150? 150 mm, and each of them fits exactly on the load-bearing walls of the building. This is the only way to create a truly reliable and durable attic structure, only the cost of its construction will be an order of magnitude more expensive than the construction of an ordinary attic. But the living area of ​​the house will increase significantly - decide what is more important for you and think through everything to the smallest detail.

Floor beams are laid across the entire width of the building, leaving 500-600 mm per ledge from the bearing walls - this will protect the wall from water flowing from the roof slopes. Along the entire perimeter of the house, a board is laid on the beams, which will become the basis for the racks of the walls of the second floor - the attic.

For the construction of all roof elements, the following fastening materials are used:

• screws,
• nails,
• self-tapping screws,
• dowel,
• wire,
• metal corners.

Once the racks are installed, you can start arranging the rafters.

Such a do-it-yourself gable roof truss system is the simplest in technical execution. Why? Firstly, because it is not necessary to calculate the device of the rafters depending on the material and location of the insulation.

And secondly, we don’t need the dimensions of the section either.

The easiest way is to "tame" a gable roof of a regular triangular shape, because all its components will have identical dimensions.

In addition, this system has several other undeniable advantages:

• the cross section of rafters and beams has a high margin for bearing capacity;
• this form is very reliable, since the load on the structure is distributed evenly, and the risk of deformation of the rafter legs disappears;
• the triangular truss system is an independent structure, therefore, in case of malfunctions in other elements of the building, it remains intact;
• the beam, laid with a small protrusion, also serves as a frame for the entire weight of the roof - and this is an additional reliability of the entire building as a whole.

Attic truss system

It will only be about a single-level attic, since it is quite possible to build it with your own hands. It is recommended to entrust the construction of more complex structures to experienced specialists, since it is easy to make mistakes in the calculations without their help, and the result will be disastrous.

A board is placed on the beam, from which the lower part is sawn off - this is done so that there are no gaps between the beams and the rafters.

On the board (100 mm) you need to lay a beam, draw a line at the place of their joining. Then, along this line, the board must be sawn, as a result of which a beveled board should be obtained, which will fit snugly against all floor beams.

Again, we cut along this line, and so on. Performing these steps will ensure that the upper part of the truss system is firmly and accurately fixed, which can be installed. Using the overlay, fasten each row of rafters at the top (on the ridge), and finally fasten the resulting strapping with a special crossbar, which will act as an overlap for the ceiling.

The rigidity of the constructed structure directly depends on how firmly the rafters are fixed to each other. It is best to use special metal lining - so you can achieve the greatest strength of the roof.

When all rows of rafters are fixed, you can begin to check the correctness of creating gables - they must be located strictly at a right angle. Here a construction plumb line is useful - an indispensable thing for such situations.

When the correctness of the design is beyond doubt, you can begin to fix all the parts together with a major fixing, this will help soft wire, nails or staples.

Now you need to stretch the twine along the top of the gables, so it will be more convenient to install the middle rafters at the same level.

To exclude the possibility of sagging of the rafter system, it is necessary to strengthen the middle rafters with special struts.

The installation of struts usually does not cause any difficulties: their lower part is fixed to the attic rack, and the upper part to the middle of the rafter leg, where you need to cut a groove of the required depth. To fix the structure, you need to choose nails from 200 mm.

That's all - do-it-yourself gable roof truss system is ready! It remains only to build a crate and cover the roof with a roof, but these are completely different technologies, which will be discussed in the next article.

21.02.2017 1 Comment

The truss system of a gable roof is a simple design that is available for a do-it-yourself device even for a novice developer. It is only necessary to make preliminary calculations, familiarize yourself with the details and stages of the construction of the roof, and calculate the materials needed for installation. When calculating, it should be taken into account that the bearing capacity of a gable roof depends on the influence of loads from wind, snow, and the weight of materials on it.

In order to make the process of building a gable roof truss system as easy as possible for you, below is a detailed step-by-step instruction for installing a truss system with your own hands.

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Requirements for building materials

For the installation of a truss system, the best option would be to use sawn timber from coniferous wood - pine, spruce or larch, grades I - III.

The material for the rafters is taken not lower than grade II, the mauerlat is made from boards or timber of grade II, for racks and girders material of grade II is taken, the crate is made from grade II-III lumber, it depends on the roof. Crossbars, puffs are made of Grade I material. On linings, linings, material of grade III can be used.

Note! Lumber must be dry with a moisture content of not more than 20%. Before installation, it should be treated with flame retardants and antiseptics against fungal diseases.

You need to store lumber under a canopy, providing protection from the sun and moisture. Level the storage area, shift the lumber with linings for ventilation.

For installation, fasteners are required: ties, plates, studs, bolts with washers and nuts, self-tapping screws with EPDM gaskets, 2.8 mm thick, mounting tape, galvanized brackets.

Brackets are used when fastening the Mauerlat, they are fastened with nails or self-tapping screws.

KR corners serve to attach the rafters to the Mauerlat, prevent the rafters from moving.

All fixing material must be made of high quality material and protected against corrosion.

Tools for the construction of the truss system

To install the gable roof truss system, you will need the following set of tools:

• tape measure, different lengths 5, 10, 20 meters;
• markers, pencils;
• cord, for stretching;
• hammers, various purposes, nail puller;
• scissors, for cutting;
• roofing knife;
• putty knife;
• Scotch;
• hacksaws, electric saw, electric drill with various drills and nozzles;
• screwdriver with nozzles;
• markings, horizontal and vertical levels;
• rails, rulers;
• mounting foam;
• safety belt and rope - for safe work.

Keep all roofing tools in a tool bag for safety.

Types of truss systems for a gable roof

sent rafters

They rely on the Mauerlat and racks installed on the inner wall, with a step equal to the rafters. To give rigidity during spans of 6 m, struts are additionally placed.

The scheme of the rafters of a gable roof

hanging rafters

If the building is of a small width, it is possible to arrange a truss system when the rafters rest on the mauerlat or walls, without intermediate supports. The maximum span is 9 meters. Such roofs can sometimes be arranged without a Mauerlat. The rafters are installed on the wall, using gaskets, on the rafters in this embodiment, a bending moment acts.

To unload, put wooden or metal lining. They securely reinforce the corner. For hanging rafters of a larger span, a headstock and struts are installed. For hanging systems, the rafters are arranged with a larger section, and the lumber is chosen not lower than grade I II.

Scheme of hanging rafters of a gable roof

Calculation of the truss system

It is possible to determine the cross-section of a gable roof beam required in the truss system by collecting all the loads acting on it: the weight of the coating, lathing, snow, wind pressure, precipitation.

Permanent loads can be determined by the weight of 1 m 2 of roofing, battens. It is important that the weight per 1 m 2 of the roof is in the range of 40-45 kg.

Variable loads from snow, wind are calculated according to the tabular values ​​of SNiP normative documents, depending on the height of the building, temperature zone. The load from snow is equal to its weight multiplied by a coefficient depending on the slope of the slope. All these calculations are carried out during the project.

And if there is no project, and the roof is being erected on a small building? You need to look at the construction of a house in the neighborhood, which is being carried out according to the project, the roof area is the same as your building. The gable roof truss system will serve as a model.

Rafter beam dimensions

At the top point, a ridge is laid that connects the rafters. The height of the ridge depends on the slope of the roof. The slope is influenced by the choice of coating material. The minimum dimensions are:

• for tiled roofs, slate 22 gr.;
• for metal tiles - 14 gr.;
• ondulin - 6 gr.;
• corrugated board - 12 gr.

The optimal angle is 35-45 gr. slope, provides a quick discharge of water and snow. In regions with strong winds, the roofs are made flat and then the angle of inclination is within 20-45 degrees.

You can determine the height by the formula: H \u003d 1 / 2 Lpr * tgA. Where A is the angle of inclination, L is the width of the building.

The task is simplified when using a ready-made table. The coefficient depends on the width of the building and the angle of inclination. Multiply the coefficient by 1⁄2 of the width of the building.

The rafters are made from pine or spruce bars, with a section of 50 × 100 mm, 50 * 150 mm.

The size of the rafters depends on the pitch. The pitch of the rafters is smaller, a larger number is installed, the cross section will decrease. The distance between the rafters at a gable roof is in the range from 600 mm to 1800 mm, it all depends on the design of the roof and the materials used for its construction.

Table of rafter sizes, depending on the step of their installation

Length rafters, mm	Distance between rafters, mm	Rafter beam section size, mm
up to 3000	1200	80×100
up to 3000	1800	90×100
up to 4000	1000	80×160
up to 4000	1400	80×180
up to 4000	1800	90×180
up to 6000	1000	80×200
up to 6000	1400	100×200

The roof does not end at the level of the walls, it is extended 500 mm outwards. The rafter leg can protrude, or a board or bar is built up. In this case, moisture does not fall on the wall, the foundation is not poured.

Step-by-step installation of the design of the gable roof truss system

The gable roof truss system consists of the following elements:

1. Mauerlat.
2. Lie down.
3. Racks.
4. Rafter.
5. Struts.
6. Puffs.
7. Crate.

Mauerlat installation

Mauerlat fasteners to a monolithic reinforced concrete belt

Mauerlat evenly distributes the load on the walls of the building, its installation can be done in several ways:

• fasten to the wall through a reinforced concrete belt with studs;
• studs are inserted into the masonry;
• a simple and common way for simple roofs, fastening with wire rod.

For him, take a bar with a section of 100 × 100 mm, 150 × 150 mm or 200 × 200 mm. Which section to choose depends on the size of the roof and its coverage. The Mauerlat is joined along the length, for this, make a 100 mm cut, 500 mm long, fold the bars and fasten with studs.

In the corners, the Mauerlat is tied with cuts to the floor of the beam, fastened with brackets or bolts. For wooden buildings, Mauerlat is the last crown. On brick walls, make a monolithic reinforced reinforced concrete belt, with a section of 400 × 300 mm. Align the pins with a thread of 12 mm in diameter along the belt, through 120 mm, for fastening.

Drill holes with a diameter of 12 mm in the Mauerlat, lay them so that the pins go into the holes. Tighten with nuts from above. Previously, we lay two layers of roofing material or roofing felt under the bar. On the outside of the wall, lay the Mauerlat with bricks. Laying the Mauerlat on a horizontally and vertically even base. It is necessary to check the horizontal level of the surface. Check diagonals. Align with pads if necessary.

Installation instructions for beds, racks, rafters, struts and puffs

Do-it-yourself do-it-yourself installation of a gable roof truss system is carried out in the following order:

1. To carry out the installation of the bed, with the sent rafters.
2. Mark the installation step of the rafter legs.
3. Prepare according to the size of the rack.
4. Install them, if necessary, unfasten them with spacers.
5. Lay a run. Check geometry. Install fastener.
6. Try on the first rafter leg, mark the cutting points.
7. Mark the points and install the rafters at the beginning and end of the roof, pull a cord between them in order to align the rest of the elements with it.
8. Having installed the rafter leg, we attach it first to the Mauerlat, then to the ridge run, to each other.
9. Screw every second leg with wire to the Mauerlat.

The fastening of the rafters to the Mauerlat is done with the help of notches, thrust corners and a hemmed support bar. Reinforce with nails or staples.

Methods for attaching rafters to the Mauerlat

Install the support posts on the beds or linings and linings. A bed is a beam 50 × 100 mm or 50 × 150 mm, laid on the middle wall along a roofing felt lining. Place brick columns under the lining, 2 bricks high.

The rafter legs are connected to each other on the ridge. Consider the common connection nodes of the truss system:

1. They make cuts at one leg and washed down at the other. Insert one leg into the cut of the other and fasten with a bolt.
2. Install overlays, wooden or metal.
3. With the help of cuts in the run, they are fixed with nails or bolts.

Methods for connecting rafters on a ridge

For the stability of the roof to wind loads, puffs, struts and runs are installed. The tightening is a bar 100 × 150 mm, runs and struts are made from a bar 50 × 150 mm or 100 × 150 mm.

With the installation of contractions, the reliability of the rafter design increases. The sections of the beam are the same as the rafters. They are attached to the legs with bolts or nails. The bracing device adds rigidity to the structure. They are installed tightly, to the surface of the rafters.

Lumber has a standard length of 6 m. Rafters can be longer. Then you need to connect them. There are several connection methods:

1. Fasten by applying bars on both sides at the junction, connect them with nails in a checkerboard pattern.
2. Overlap, one part of the rafter to another, at a distance of 1 meter, fasten with nails in a variable order.
3. Run a cut obliquely, cut out part of the legs of the rafters, connect them, reinforcing them with bolts.

Lathing device

A crate is laid along the roof rafters. It serves to distribute the load from the roofing material, snow on the rafters. It plays the role of an air gap between the roof and the truss system.

The design of the crate depends on the accepted roofing material:

• under the soft tiles, make the crate continuous, an anti-condensate film is laid on the rafters, it is pressed on top with a counter rail, the crate is nailed onto it, then the OSB boards and the lining carpet, we lay the tiles on top.
• under the roof of the corrugated board, the crate should be sparse. The step of the lathing depends on the brand of corrugated board, its thickness and the angle of the roof.
• make a crate for standard slate in increments of 500 mm from a bar 75 × 75 mm or 50 × 50, as well as boards from 30 × 100 mm. It is necessary to take into account the design features of the roof, with the final choice of a suitable option.

The lumber from which the crate is made is pine of the first or second grade. It is advisable to take a width of no more than 14 cm. With a width of more, the boards can warp and damage the roofing. The length of the nails should be three times the thickness of the crate. Lay boards along the ridge. Set the first board of greater thickness to the height of the roofing.

To arrange a continuous crate along the slope of the roof.

With the first layer, lay a board along the ridge from it at a distance of 500-1000 mm next, and so on. With the second layer, lay the crate in the direction along the rafters. Arrange the joint between the boards only on the rafters in a run. The nail is sunk completely with the head into the pulp of the wood.

Cornice overhangs

Arranged to protect against precipitation, play an aesthetic role. Eaves overhangs suit tightly without gaps. The final stage in the construction of the roof.

Scheme of the device of the eaves overhang of a gable roof

Gable

The gable roof has two gables. They have the shape of a triangle, with the apex at the ridge and the sides coincide with the slopes of the roof. Gables support the rafters and enclose the attic space. Protect from wind and precipitation, give stability to the roof.

In wooden buildings, the pediment is made frame. In brick buildings, frame or brick. Gables made of brick or gas block are erected before the roofing device. They require very precise execution.

Frame gables fit into the finished opening when the truss system is already assembled.

The frame is made of bars or boards. The frame elements are connected on spikes or to the floor of a tree, all fastened with nails. They are sheathed by nailing boards, lining or siding, maintaining the color in the decoration of the facade of the building. For the device of a window opening, an additional frame is made under it according to the size of the window. If the attic is insulated, then the pediment also needs to be insulated. Insulation is laid in the middle of the frame. A mineral wool insulation with reduced flammability is used. From the outside, the frame is upholstered with a hydro-windproof film or a windproof membrane, from the inside, a vapor-tight film or a vapor-tight membrane is nailed under the finishing material.

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