Detailed plan of a complex pitched roof. Gable roof truss system project

When designing any residential building, architects pay special attention to the roof, since it performs not one, but several functions at once, depending on its design features. It must be said that not all future homeowners are satisfied with the usual gable roof, although it can be called the most reliable, since it has only two pitched planes and one joint between them. Many are attracted by more complex structures, which add special appeal and originality to the structure. Other, more practical homeowners prefer skylights that can serve as both a roof and a second floor at the same time.

The basis of any roof is an individual rafter system, which has its own design features. It will be much easier to make the choice of the desired roof frame if you figure out in advance which types and diagrams of rafter systems used in construction practice. After receiving such information, it will become more clear how complex such structures are in installation. This is especially important to know if the roof frame is supposed to be erected independently.

The main functional tasks of roof systems

When arranging pitched roof structures, the rafter system is a frame for covering and for holding the materials of the "roofing pie". With proper installation of the frame structure, the necessary conditions for correct and non-insulated types of roofs that protect walls and the interior of the house from various atmospheric influences.

The roof structure is also always the final architectural element exterior design of the building, supporting its stylistic direction with its appearance. Nevertheless, the design features of the rafter systems must first of all meet the strength and reliability requirements that the roof must meet, and only then - the aesthetic criteria.

The frame of the rafter system forms the configuration and angle of inclination of the roof. These parameters largely depend on natural factors specific to a particular region, as well as on the desire and capabilities of the homeowner:

The amount of precipitation in different periods of the year.
The direction and average speed of the wind in the area where the building will be erected.
Plans for the use of the space under the roof - the arrangement of residential or non-residential premises, or using it only as an air gap for thermal insulation of the rooms below.
A type of planned roofing material.
The financial capabilities of the homeowner.

Atmospheric precipitation and the strength of wind flows give a very sensitive load on the roof structure. For example, in regions with heavy snowfalls, you should not choose a rafter system with a small angle of inclination of the slopes, since the snow masses will linger on their surface, which can lead to deformation of the frame or roofing or to leaks.

If the area where the construction will be carried out is famous for its winds, then it is better to choose a structure with a slight slope of the slope so that the sudden gusts that occur do not tear off individual elements of the roof and roof.

Basic elements of the roof structure

Details and assemblies of rafter systems

Depending on the type of truss system chosen, the structural elements used can vary significantly, however, there are details that are present in both simple and complex roof systems.

The main elements of the rafter system of a pitched roof include:

Rafter legs that form the roof slopes.
- wooden beam, fixed on the walls of the house and serves to fix the lower part on it rafter legs.

The ridge is the joint of the frames of the two slopes. It is usually the highest horizontal line of the roof and serves as the support on which the rafters are anchored. The ridge can be formed by rafters, fastened together at a certain angle, or fixed on the ridge board (run).
The lathing is slats or beams mounted on rafters with a certain pitch and serving as the basis for the flooring of the selected roofing material.
Retaining elements, which include benches, girders, struts, struts, ties and other parts, serve to increase the rigidity of the rafter legs, support the ridge, and tie individual parts into a common structure.

In addition to the above-mentioned structural details, other elements can be included in it, the functions of which are aimed at strengthening the system and optimal distribution of the roof loads on the walls of the building.

The rafter system is divided into several categories, depending on the different features of its design.

Attic space

Before proceeding to review different types roofs, it is worth figuring out what the attic space can be, since many owners successfully use it as utility and full-fledged living quarters.

Design pitched roofs can be divided into attic and attic. The first option is called this way because the space under the roof has low height and is used only as a warming air gap from the top of the building. Such systems usually include or has several slopes, but located at a very slight angle.

The attic structure, which has a sufficiently large ridge height, can be used in different ways, be insulated and not insulated. These options include the attic or gable version. If a roof with a high ridge is chosen, then it is imperative to take into account wind loads in the region where the house is built.

Slope of ramps

To determine the optimal slope of the roof slopes of a future residential building, first of all, you need to take a closer look at the already built low-rise neighboring houses. If they have been standing for more than one year and can withstand wind loads, then their design can be safely taken as a basis. In the same case, when the owners set the goal of creating an exclusive original project, unlike the buildings standing nearby, it is necessary to familiarize yourself with the design and operational features of various rafter systems and make the appropriate calculations.

It should be borne in mind that the change in tangential and normal values of the wind force depends on how large the slope of the roof slopes is - the steeper the angle of inclination, the more important are the normal forces and the less tangential. If the roof is sloping, then the shear wind load affects the structure more, since the lifting force increases from the leeward side and decreases from the windward side.

Winter snow load must also be taken into account when designing the roof. Usually this factor is considered in conjunction with the wind load, since the snow load on the windward side will be much lower than on the leeward slope. In addition, there are places on the slopes where snow will necessarily collect, giving a large load on this area, so it should be strengthened with additional rafters.

The slope of the roof slopes can vary from 10 to 60 degrees and should be selected not only taking into account the consolidated external load, but also depending on the roofing to be used. This factor is taken into account because roofing materials differ in their weight, their fixing requires a different number of elements of the rafter system, which means that the load on the walls of the house will also differ, and how large it will also depend on the angle of the roof slope. Of no small importance are the features of each coating in terms of resistance to moisture penetration - in any case, many roofing materials need one or another slope to ensure the free flow of storm water or melting snow. In addition, when choosing the slope of the roof, you need to think in advance about how the cleaning process will be carried out and renovation works on the roof.

When planning this or that angle of the roof slopes, you need to know that the fewer joints between the covering sheets, and the more airtight they are, the less you can make the slope of the slope, of course, if it is not supposed to arrange a residential or utility room in the attic space.

If a material consisting of small elements is used to cover the roof, for example, ceramic tiles, then the slope of the slopes must be made steep enough so that water never lingers on the surface.

Given the weight of the roofing material, you need to know - the heavier the coating, the greater the angle of the slopes, since in this case the load will be correctly distributed to the rafter system and load-bearing walls.

The following materials can be used to cover the roof: either profile sheet, galvanized steel, corrugated asbestos concrete and bitumen-fibrous sheets, cement and ceramic tiles, roofing material, soft roofing and other roofing materials. The illustration below shows the permissible slope angles for different types roofing.

Basic constructions of truss systems

First of all, it is worth considering the basic types of rafter systems in relation to the location of the walls of the house, which are used in all roof structures. Basic options are divided into layered, hanging, and also combined, that is, including elements of both the first and second types of systems in its design.

rafters

Nasal system

In buildings where internal load-bearing walls are provided, a layered rafter system is often installed. It is much easier to mount it than a hanging one, since the internal load-bearing walls provide reliable support for its elements, and in addition, this structure will require fewer materials.

For rafters in this system, the defining reference point is the ridge board, on which they are fixed. The non-thrust type of the layered system can be equipped in three options:

In the first version, the upper side of the rafters is fixed on a ridge support, called sliding, and their lower side is fixed by cutting to the Mauerlat. Additionally, the rafters in the lower part are fixed to the wall using wire or staples.

In the second case, the rafters in the upper part are cut at a certain angle and connected to each other using special metal plates.

The lower edge of the rafter legs is attached to the Mauerlat with movable fasteners.

In the third version, the rafters are rigidly fastened in the upper part with bars or treated boards, located horizontally, parallel to each other on both sides of the rafters connected at an angle, and the ridge girder is pinched between them.

In the lower part, sliding fasteners are used to secure the rafters, as in the previous case.

It is necessary to explain why sliding fasteners are often used to fix the rafters on the Mauerlat. The fact is that they are able to relieve the load-bearing walls from excessive stress, since the rafters are not rigidly fixed, and when the structure shrinks, they have the ability to move without deforming overall design roofing system.

This type of fastening is used only in layered systems, which also distinguishes them from the hanging version.

However, in some cases, a spacer system is used for layered rafters, in which the lower end of the rafters is rigidly fixed to the Mauerlat, and in order to remove the load from the walls, puffs and struts are built into the structure. This option is called complex, since it includes elements of a layered and hanging system.

Roof construction is one of the most critical stages of construction. The durability of the building itself and the level of comfort of living in it directly depend on the reliability of the "umbrella" from above, on its resistance to precipitation and any external influences.

Of all the variety of roof structures, the gable can be attributed to the most popular, simply due to the relative simplicity of its construction. However, behind this "simplicity" lies a lot of different nuances, the need for certain calculations and adherence to technological rules. However, this publication has a primary purpose: to show that the installation of rafters gable roof do it yourself - the task is quite feasible, even for a novice builder.

Let's go through all the stages of the process of installing rafters for such a roof together, from the basics of preliminary design to an example of practical implementation.

General structure of a gable roof

Basic concepts

Structural elements of the gable roof truss system

Let's make a reservation right away that this diagram, of course, cannot reflect the entire possible variety of designs, but the main details and nodes on it are shown quite clearly.

1 - Mauerlat. This is a board or timber that is rigidly attached to the upper end of the external load-bearing walls of the building. Its purpose is to evenly distribute the load from the entire roof system to the walls of the house, to create conditions for reliable fastening of the rafter legs at their lowest point of support.

2 - rafter legs installed in pairs. They become the main bearing parts of the entire roof system - it is the rafters that set the steepness of the slopes, will be the basis for fastening the battens, roofing, and if the roof is planned to be insulated, then also the entire thermal insulation "pie".

For the manufacture of rafter legs, high-quality boards or timber are used, you can also use round timber. About the cross-section of lumber, which will be sufficient to guarantee withstanding all possible loads, will be described below.

The rafters can end on the Mauerlat, but more often they go beyond the perimeter of the walls of the house, forming a cornice overhang. However, for this, lighter parts can also be used - the so-called "filly", with which the rafter legs are extended to the required overhang width.

To form the eaves overhang, the rafters are extended with "filly"

3 - ridge run. It can be a bar, a board, or even a composite structure. The run runs along the entire line of the ridge and serves to reliably connect the upper points of the paired rafter legs, link all the rafter pairs in order to impart overall rigidity to the entire roof structure. IN different options roofs, this girder can be rigidly supported on the racks, or tied only to the junction of the rafter legs.

4 - tightening (contractions, crossbars). Horizontal details of the reinforcement of the system, additionally connecting the paired rafter legs to each other. Several puffs at different heights can be used.

5 - floor beams, which will serve as the basis for the installation of the floor in the attic and the ceiling from the side of the room.

6 - and this beam at the same time serves as a bed. This is a beam that runs along the entire length of the roof, which is a support for the installation of additional reinforcement parts for the rafter system. The bed can be installed as shown in the figure (by the type of floor beams), or rigidly laid on the main partition inside the building.

7 - racks (headstock) - additional vertical supports of the rafter legs, preventing their deflection under the influence of external loads. The racks at the top can abut against the rafters themselves, or into an additional girder that longitudinally connects the rafter legs at a certain height.

8 - struts. Often, with a large length of rafter legs, their bearing capacity is not enough, and reinforcement only by racks does not provide the necessary strength. In these cases, diagonal reinforcing elements are used, resting on the bottom from the bottom, creating an additional point of support for the rafters. The number of struts and the location of their installation can vary in roofs of varying degrees of complexity.

Some differences between the hanging and layered gable roof system

Gable roofs can be divided into two types of structures - with layered and hanging rafters. In addition, combined systems are widely used, in which both construction principles are combined. What is the fundamental difference?

Rafter roof system

This structure of the truss system is characterized by the presence of support on the internal capital partition in the building. On the upper end of this partition, a bed is mounted, on which the drains support the ridge run. Thus, the rafter legs are "leaned" on the vertical support, which makes the entire system as strong as possible.

This scheme is the most popular because of its reliability and relative simplicity in implementation. If it is possible to create an additional pivot point in the center, then why not take advantage of this? True, if it is planned to place a dwelling in the attic, then vertical racks can sometimes become an obstacle. However, their presence is also sometimes "played up", using, for example, for the installation of an internal lightweight partition.

Depending on the number and placement of internal partitions, the design of the layered rafter system may vary. Some examples are shown in the illustration below:

Fragment "a" shows the simplest version, which, by the way, on small rafter lengths (up to 5 meters) may not even have the braces shown - a row of central posts under the ridge run is enough

With an increase in the width of the building, the system naturally becomes more complicated, and additional reinforcing elements appear - puffs and struts (fragment "b").

Fragment "c" clearly demonstrates that the internal capital wall does not have to be located exactly in the center, under the ridge. It is quite possible and such an option, as shown in the illustration, but with the condition that the displacement of the bed relative to the ridge does not exceed one meter.

Finally, fragment "d" shows how the rafter system in a building can be supported. big size, but with two main partitions inside. The distance between such parallel planks can be up to a third of the building's width.

Hanging rafter system

Graphically, this roof scheme can be depicted something like this:

It is immediately striking that the rafters rest only on the lower part, and then are connected to each other on the ridge. There is no additional support in the center, that is, the rafter legs seem to "hang", which predetermines the name of such a system. This feature imposes certain restrictions on the use of hanging rafters - usually such a scheme is practiced when the distance between the bearing walls, on which the Mauerlat is fixed, is no more than 7 meters. Installed tightenings only partially relieve the load from the external walls.

The illustration below shows several options for a hanging system. However, some of them, rather, can be classified as combined.

Fragment "d" - hanging rafters are interconnected with a coupler at the level of the Mauerlat or fixed on a powerful floor beam, forming a triangle with it. There are no other reinforcing parts. A similar scheme is permissible with a distance between the walls up to 6 meters.

Option "w" - for a house of the same size (up to 6 meters). The tightening (crossbar) in this case is shifted upward, and is often used to hem the ceiling of the attic.

Options "e" and "z" are designed for a span between walls up to 9 meters. Multiple ties can be applied (or the top tie in combination with the bottom joist). Another approach is to install racks under the ridge run, similar to the layered system. Only as the lowest point of support is not a lie on the main partition, but the racks are supported by a tightening or a floor beam. Calling this option purely "hanging" is already difficult, since here is clearly a combination of parts from both designs.

To an even greater extent, such a combination of the two schemes is expressed in the “i” version, which is designed for large spans, from 9 to 14 meters. Here, in addition to the headstock rack, diagonal struts are also involved. Often, such trusses are generally assembled on the ground, and only then they are raised and installed in place, connected to each other, thereby forming the entire roof frame.

So, in preparation for the construction of a gable roof, it is necessary to study the principles of a particular system, evaluate their advantages and disadvantages, choose the optimal one for your conditions and draw up a graphical working diagram. You will need it when purchasing necessary material, and for the production of themselves installation works... However, drawing up a drawing should still be preceded by some calculations.

Calculation of the basic parameters of the gable roof truss system

Let's take another look at schematic diagram gable roof devices to highlight those parameters that need to be calculated.

So, in the calculation process, we need to decide on the following values.

The initial data is the length of the side of the house along the pediment part (highlighted in blue - F), and the length of the house along the ridge (purple - D). It is assumed that the owners have already decided in advance on the type of roofing - since there will be certain restrictions on the steepness of the roof slopes. (angle a).

The height of the ridge above the Mauerlat plane (H - green color), or, conversely, determine the angle of the slope, starting from the planned height of the ridge.
The length of the rafter leg ( Blue colour- L), and, if necessary, lengthening the rafters to form a cornice overhang of the required width (l).
Calculate the total loads that fall on the rafter system in order to determine the optimal cross-section of lumber for the manufacture of rafters, the pitch of their installation (red - S) and the permissible length of spans between the support points. All these parameters are closely interconnected.
When these calculated values are on hand, it is already easy to draw up a graphical diagram, determine the need and optimal location of the amplification elements, and calculate the amount of material for their manufacture.

Chainsaw prices

chainsaw

We calculate the steepness of the slope and the height of the ridge

The steepness angle of the slopes can be determined by the owners according to various evaluation criteria:

For purely aesthetic reasons - when "at the forefront" becomes appearance buildings. Many people like roofs with a high ridge, but at the same time we must not forget that the wind load on such a roof sharply increases. And the materials for the manufacture of a high roof will go immeasurably more. At the same time, on steep slopes, the snow load is reduced to almost zero - it is possible that for “snowy” regions this parameter of assessment may become decisive.
For reasons useful use attic space. With a gable roof scheme, in order to achieve the maximum attic area, it is necessary to erect ramps with a very large steepness, that is, with the same consequences as mentioned above.

Finally, there may be a completely opposite approach - for reasons of economy, to make a roof structure with a minimum height in the ridge. But in this case, you will have to focus on the minimum permissible slope angles for a specific type of roofing. Reducing the slope below the manufacturer's recommended indicators is to "plant a bomb" in your roof, both for reasons of its strength and durability, and from the standpoint of the waterproofing qualities of the coating.

It is not difficult to calculate the height of the ridge above the floor plane (Mauerlat). The overwhelming majority of nodes of any roofing system is based on a triangle, which, in turn, obeys strict geometric (more precisely, trigonometric) laws.

So, in our case, the width of the roof along the pediment line is known. If the roof is symmetrical, then the ridge will be placed exactly in the middle, and for calculations, you can simply divide the width F by two (the base of the triangle f =F / 2). With asymmetric slopes, you will have to project the top of the ridge onto line F, and measure the distances f1 and f2 from it to the edge of the triangle (to the Mauerlat) on each side. Naturally, in this case, the slope of the slopes will be different.

H =f × tga

In order not to force the reader to look for the values of the tangents and carry out calculations manually, a calculator is placed below, in which the necessary tabular values have already been entered.

1) Apply the coordination axes of the building.

2) Draw the outline of the walls.

3) Lay the Mauerlat on the outer walls along the perimeter of the building.

4) In the corners of the building, lay a support rail to support the diagonal rafter legs.

5) Draw diagonal rafter legs at an angle of 45 ° from the corners of the building.

6) Lay the bench along the inner wall of the building and show the upper girder.

7) Lay the rafter legs, starting from the support node, at a certain distance.

8) On the diagonal rafter legs, lay short rafter legs in a checkerboard pattern.

9) Install the racks every 3000 - 6000 mm, starting from the support unit.

10) If the width of the building is more than 12 m, place the crossbar to the rafter legs.

11) To form a cornice, a filly is nailed to each rafter leg, and filly, called shorties, are nailed to the diagonal rafter legs from both sides.

An effective solution to the roof is the use of layered rafters to bridge spans up to 14 m with one internal support in the building and up to 16 m with two internal supports.

The rafter mates are performed using fastening bolts, staples, silt and nails.

In the case when the distance between the supports (external or internal) is more than 7500 mm, in civil buildings, the load-bearing base of the roof is roof trusses, representing a flat geometrically unchangeable lattice system, consisting of separate, interconnected elements (rods). Roof trusses can be wooden, metal-wood, steel and reinforced concrete. Wooden farms are called hanging rafters.

The pitch of the trusses with spans up to 9 m is 3 - 4 m, with spans of more than 10 m - 1.5 - 2 m.

Hanging rafter patterns

Dormer windows arrange in pitched roofs for lighting, airing the attic, exit through them to the roof. They can be semicircular, triangular, rectangular. Lighting - through a glazed sash with a size of at least 0.6 × 0.8 m. Wooden louvered grilles located adjacent to the glazed sash of the dormer are used for ventilation. Dormer windows must be placed so that through ventilation is provided. It is recommended to place the bottom of the window no higher than 0.8 - 1.0 m from the top of the attic.

Types of dormers

a - triangular; b - semicircular; в - rectangular; r - polygonal

1 - glazed parapet; 2 - louvered grille

When designing a house, attention should be paid to the rafter system. A so-called rafter plan must be drawn up, which includes all the features of the structure of the structure, the step of the rafter legs and other points necessary to build a reliable and durable roof that can withstand the design loads.

Types of truss systems.

Rafter System Design

Planning the rafters for hipped roof, gable or for another design - a complex and responsible process at the same time. That is why a special program is used to draw up a drawing; it is required to take into account the calculations of snow and wind loads, the weight of the roofing material, and the dimensions of the house itself. The plan is drawn up by a specialist who has the necessary experience in performing such work. When drawing up a plan of rafters, such parameters are taken into account as:

material for the construction of the roof (it can be wood or metal);
type of roof, its features;
angle of inclination of the roof;
section of rafter legs;
if the listed data are available, you can proceed with the implementation of the rafter system plan.

The design of the rafter legs depends on:

Attachment of the rafters to the Mauerlat.

the shape of the future roof;
the length of the slabs and the space that needs to be covered;
the presence of internal supports.

The rafter plan should be drawn up taking into account all the parameters. For the construction of the roof, layered and hanging rafters are used. The leg can be designed in a triangle shape for maximum rigidity and strength. If complex farms will be used, then you will additionally have to purchase:

struts;
crossbars;
tightening;
additional racks;
roof beams.

Reinforced rafters are used for houses where the middle is taken as the load-bearing wall. The rafter structure includes 2 rafter legs, a Mauerlat on which they rest from below, and a ridge girder for support from above, as well as racks. The racks are mounted on a bed, it is placed on the inside load-bearing wall, which makes it possible to correctly distribute all the loads. If there are no internal walls, then the support falls on pillars or columns, the step between which is 6.5 m.

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Hanging rafters are used when internal supports or walls are completely absent. In this case, the rafter legs will only rest on the outer walls.

Diagram of the rafter system of the broken roof of the attic.

The structure includes the rafter legs themselves, a horizontal bar in the form of a stretch. The lower ends of the beams rest on a special Mauerlat on top of the wall, it allows you to distribute the loads evenly. Such rafters can provide an overlap of a space of 7-12 m. Crossbars are used for reinforcement.

The production of hanging rafters is more complicated than layered ones, which is why the latter are used much more often. The cost of hanging rafters is higher, but in some cases only they can be used. Combined systems can be used to reduce costs. This makes it possible to make construction easier and more economical.

The drawing is drawn up using a special program. When drawing up a drawing, the following actions are performed:

Modular coordination networks are applied first, they allow you to link all the data on the structure of the rafter system to the main walls of the future house.
All channels of the ventilation and smoke system, pipelines that will go out through the rafter system during construction are drawn on the plan.
A plan for the future selected roof shape is being developed. When drawing up a sketch, you need to take into account the location of the walls.

The diagram must indicate the elements that the roof has: the edges of the roof, valleys, ridge, and so on. It is imperative to take into account what shape the slopes will take, the direction and angle of the slope. The drawing indicates the location of gables, dormers, if any.

Using the roof system plan, builders will erect a solid and reliable design... The plan must indicate the parameters:

The construction of a single-pitched roof rafter system.

rafter beams;
mauerlat;
rafter legs;
puffs and filly for fastening legs;
racks with longitudinal struts, guaranteeing the spatial rigidity of the entire rafter system (in the drawing, such elements must be displayed as a dashed line).

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If you plan to build a roof truss system made of metal, i.e. special galvanized beams, it is necessary to use completely different programs intended for the design. This can only be done by a specialist, otherwise, if the calculations are incorrect, the roof will not withstand the loads. The step of the rafter legs is calculated taking into account building material, loads from insulation. For example, for a hipped roof, which is built of wood, the rafter pitch can be:

When making rafter legs from beams, the step is 150-180 cm.
When making rafter legs from edged boards the step is 100-120 cm.

It is important that the ventilation outlets of the pipes are shown on the plan, as reinforcement of the structure may be required.

In some, for the passage of the pipe, it is necessary to cut the rafter leg, and install the remaining ends on special wooden jumpers, which will be located between the legs located next to them. For fasteners, in this case, a gash is used. Roof system diagram.

Technological rules

Scheme of rafters with a sliding support.

For a hipped roof or other configuration, small skylights are provided in the gables to provide proper ventilation attic rooms, especially in the warm season. For example, for a hipped roof, it is necessary to display the diagonal rafter legs on the rafter plan, the beaters resting on them. It is important not to forget about the dormers, which will be located on the hips.

If the construction of an attic dwelling is planned, then the upper beams for tying the walls should be displayed on the plan. They will serve as a support for the rafter legs of the entire structure, providing the necessary strength and reliability of the roof. The design scheme is always carried out simultaneously with the development of plans for all structural sections of the building. This allows you to link them together, to ensure correct and accurate design. As a result, each node will be clearly connected with the rest, the structure will be stable and reliable.

Rafters perform a number of significant roofing functions. They set the configuration of the future roof, perceive atmospheric loads, and hold the material. Among the rafter duties, the formation of flat planes for laying the coating and providing space for the components of the roofing pie.

In order for such a valuable part of the roof to flawlessly cope with the listed tasks, information is needed about the rules and principles of its construction. The information is useful both for those who construct the gable roof rafter system with their own hands, and for those who decide to resort to the services of a hired team of builders.

In the device of the rafter frame for pitched roofs, wooden and metal beams are used. The starting material for the first option is a board, a log, a bar.

The second is built from rolled metal: a channel, shaped pipe, I-beam, corner. There are combined structures with the most loaded steel parts and timber elements in less critical areas.

In addition to the "iron" strength, the metal has a lot of disadvantages. These include heat engineering qualities that do not satisfy the owners of residential buildings. The need for welded joints is disappointing. Most often, industrial buildings are equipped with steel rafters, less often private cabins assembled from metal modules.

In the case of independent construction of truss structures for private houses, wood is a priority. It is not difficult to work with it, it is lighter, "warmer", more attractive in terms of environmental criteria. In addition, to make nodal connections, you do not need a welding machine and welder skills.

Rafters - a fundamental element

The main "player" of the frame for the construction of the roof is the rafter, among the roofers called the rafter leg. Beds, braces, headstock, purlins, tightenings, even a Mauerlat may or may not be used depending on the architectural complexity and dimensions of the roof.

The rafters used in the construction of the frame of gable roofs, according to technical characteristics and the method of laying, are divided into:

Fortified rafter legs, both heels of which have reliable structural supports. The lower edge of the layered rafter rests against the Mauerlat or the ceiling crown of the log house. The support for the upper edge can be a mirror analogue of the adjacent rafters or a girder, which is a beam horizontally laid under the ridge. In the first case, the rafter system is called a spacer, in the second it is non-spacer.
Hanging rafters, the top of which rests against each other, and the bottom is based on an additional beam - a tightening. The latter connects the two lower heels of adjacent rafter legs, resulting in a triangular module called a rafter truss. The tightening dampens the stretching processes, due to which only a vertically directed load acts on the walls. The structure with hanging rafters, although it is a spacer, does not transfer the spacer itself to the walls.

In accordance with the technological specifics of rafter legs, structures constructed from them are divided into layered and hanging ones. For the stability of the structure, they are equipped with struts and additional struts.

For the device of the supports for the top of the layered rafters, beams and girders are mounted. In reality, the rafter structure is much more complex than the described elementary templates.

Note that the formation of a gable roof frame can generally be performed without a rafter structure. In such situations, the supposed planes of the slopes are formed by slugs - beams laid directly on the bearing gables.

However, we are now specifically interested in the device of the rafter system gable roof, and it can involve both hanging or layered rafters, or a combination of both types.

The subtleties of attaching the rafter legs

The rafter system is fastened to brick, foam concrete, aerated concrete walls through the Mauerlat, which in turn is fixed with anchors.

Between the Mauerlat, which is a wooden frame, and the walls made of these materials, a waterproofing layer of roofing material, waterproofing, etc. is necessarily laid.

The top of the brick walls is sometimes specially laid out so that something like a low parapet is obtained along the outer perimeter. So it is necessary that the Mauerlat placed inside the parapet and the walls do not burst the rafter legs.

Roof frame rafters wooden houses rest on the upper crown or on ceiling beams... The connection in all cases is made by cuts and duplicated with nails, bolts, metal or wooden plates.

How to do without furious calculations?

It is highly desirable that the cross-section and linear dimensions of wooden beams are determined by the project. The designer will give clear design justifications for the geometric parameters of the board or timber, taking into account the entire spectrum of loads and weather conditions. If available home master there is no design development, his path lies on the construction site of a house with a similar roofing structure.

You can ignore the number of storeys of the building being erected. It is easier and more correct to find out the required dimensions from the foreman than to learn them from the owners of shaky unauthorized construction. Indeed, in the hands of the foreman, the documentation with a clear calculation of the loads on 1m² of the roof in a particular region.

The step of installing the rafters determines the type and weight of the roofing. The heavier it is, the less the distance between the rafter legs should be. For laying clay tiles, for example, the optimal distance between the rafters will be 0.6-0.7 m, and for the profiled sheet, 1.5-2.0 m is permissible.

However, even if the step required for the correct installation of the roof is exceeded, there is a way out. This is a reinforcing counter-grid device. True, it will increase both the weight of the roof and the construction budget. Therefore, it is better to understand the step of the rafters before the construction of the rafter system.

Craftsmen calculate the step of the rafters according to design features buildings, corny dividing the length of the ramp into equal distances. For insulated roofs, the step between the rafters is selected based on the width of the insulation plates.

On our website you can find, which may also help you a lot during construction.

Roof structures of layered type

The rafter structures of the layered type are much simpler in execution than their hanging counterparts. A reasonable plus of the layered scheme is to provide full ventilation, which is directly related to the long-term service.

Distinctive design features:

Mandatory support under the ridge heel of the rafter leg. The role of support can be played by a run - wooden beam resting on racks or on inner wall structures, or the upper end of the adjacent rafters.
The use of Mauerlat for the construction of a truss structure on walls made of brick or artificial stone.
The use of additional girders and racks where the rafter legs, due to the large size of the roof, require additional support points.

The disadvantage of the scheme is the presence of structural elements that affect the layout of the internal space of the operated attic.

If the attic is cold and it is not supposed to organize useful premises in it, then the layered structure of the rafter system for the device of a gable roof should be preferred.

Typical work sequence for the construction of a layered rafter structure:

First of all, we measure the height of the building, the diagonals and the horizontality of the upper cut of the frame. When detecting vertical deviations of brick and concrete walls, we eliminate them cement-sand screed... We reduce the excess of the heights of the log house. By placing wood chips under the Mauerlat, vertical flaws can be dealt with if their size is insignificant.
The overlap surface for laying the bed must also be leveled. He, the Mauerlat and the girder should be clearly horizontal, but the location of the listed elements in the same plane is not necessary.
We process all wooden parts of the structure before installation with fire retardants and antiseptic preparations.
On concrete and brick walls we lay waterproofing for the installation of the Mauerlat.
We lay the Mauerlat timber on the walls, measure out its diagonals. If necessary, slightly move the bars and turn the corners, trying to achieve the perfect geometry. Align the frame horizontally if necessary.
We mount the Mauerlat frame. The splicing of the beams into a single frame is carried out by means of oblique cuts, the joints are duplicated with bolts.
We fix the position of the Mauerlat. Fastening is made either with staples to the wooden plugs laid in the wall ahead of time, or with anchor bolts.
We mark the position of the bed. Its axis should recede from the Mauerlat bars at equal distances on each side. If the girder rests only on racks without a bed, the marking procedure is carried out only for these posts.
We install the bed on a two-layer waterproofing. We fasten it to the base with anchor bolts, with inner wall we connect with wire twists or staples.
We mark the installation points of the rafter legs.
We cut out the racks to the same size, because The bed is on the horizon. The height of the racks should take into account the dimensions of the purlin section and the bed.
We install racks. If provided by the project, we fasten them with spacers.
We put the run on the racks. Check the geometry again, then install the brackets, metal plates, wooden fixing plates.
We install a test rafter board, mark the cutting points on it. If the Mauerlat is set strictly to the horizon, there is no need to adjust the roof rafters in fact. The first board can be used as a template for making the rest.
We mark the installation points of the rafters. For marking, folk craftsmen usually prepare a pair of rails, the length of which is equal to the gap between the rafters.
According to the markings, we install the rafter legs and fasten them first at the bottom to the Mauerlat, then at the top to the girder to each other. Every second rafter is screwed to the Mauerlat with a wire bundle. IN wooden houses The rafters are screwed to the second crown from the top row.

If the rafter system is made flawlessly, the planks are mounted in random order.

If there is no confidence in the ideal structure, then the extreme pairs of rafters are first installed. A control twine or fishing line is pulled between them, according to which the position of the newly installed rafters is adjusted.

The installation of the rafter structure is completed by the installation of fillies, if the length of the rafter legs does not allow the formation of an overhang of the required length. By the way, for wooden buildings, the overhang should "go out" beyond the building outline by 50 cm. If the organization of the visor is planned, separate mini-rafters are installed under it.

Another useful video about building a gable rafter base with your own hands:

Hanging truss systems

The hanging type of rafter systems is a triangle. The two upper sides of the triangle are folded by a pair of rafters, and the tightening that connects the lower heels serves as the base.

The use of a tightening allows you to neutralize the action of the thrust, therefore, only the weight of the sheathing, the roof, plus the weight of precipitation, depending on the season, acts on walls with hanging rafter structures.

The specifics of hanging truss systems

Characteristic features of hanging rafter structures:

Mandatory presence of a puff, made most often from wood, less often from metal.
Ability to refuse to use Mauerlat. A timber frame will be successfully replaced by a board laid on a two-layer waterproofing board.
Installation on the walls of ready-made closed triangles - roof trusses.

The advantages of the hanging scheme include the space under the roof free of racks, which allows you to organize an attic without pillars and partitions. There are disadvantages.

The first of them is restrictions on the steepness of the slopes: the angle of their slope can be at least 1/6 of the span of a triangular truss, steeper roofs are strongly recommended. The second disadvantage is the need for thorough calculations for the competent device of the cornice nodes.

Among other things, the corner of the truss will have to be set with pinpoint accuracy, since the axes of the connected components of the hanging rafter system must intersect at a point, the projection of which must fall on the central axis of the Mauerlat or the lining board replacing it.

Subtleties of large-span hanging systems

The brace is the longest element of the hanging truss structure. Over time, as is typical for all lumber, it deforms and sags under the influence of its own weight.

The owners of houses with spans of 3-5 m are not too worried about this, but owners of buildings with spans of 6 or more meters should think about installing additional parts that exclude geometric changes in tightening.

There is a very significant component to prevent sagging in the rafter system installation scheme for a large-span gable roof. This is a pendant called a headstock.

Most often, it is a bar attached with wooden beads to the top of a truss. The headstock should not be confused with the racks, because its lower part should not come into contact with the puff at all. And the installation of racks as supports in hanging systems is not used.

The bottom line is that the headstock seems to hang on the ridge knot, and a tightening is already attached to it with the help of bolts or nailed wooden linings. Threaded or collet type clamps are used to correct slack.

Adjustment of the tightening position can be arranged in the area of the ridge assembly, and the headstock is rigidly connected to it with a cut. Instead of a bar in non-residential attics, reinforcement can be used to manufacture the described tightening element. It is recommended to arrange a headstock or suspension also where the tightening is assembled from two bars to support the connection section.

In an improved hanging system of this type, the headstock is supplemented by strut beams. The stress forces in the resulting rhombus are extinguished spontaneously due to the competent arrangement of the vector loads acting on the system.

As a result, the rafter system pleases with stability with minor and not too expensive modernization.

Hanging type for attics

In order to increase the usable space, the tightening of the truss triangles for the attic is moved closer to the ridge. A perfectly reasonable move has additional pluses: it allows you to use the puffs as a basis for ceiling stitching.

It joins the rafters by cutting with a semi-rotary screw with a duplicating bolt. It is protected from sagging by installing a short headstock.

A tangible disadvantage of the attic hanging structure is the need for accurate calculations. It is too difficult to calculate it yourself, it is better to use a ready-made project.

Which design is more cost effective?

Cost is an important argument for an independent builder. Naturally, the price of a structure for both types of rafter systems cannot be the same, because:

In the construction of a layered structure for the manufacture of rafter legs, a board or a beam of a small section is used. Because layered rafters have two reliable supports under them, the requirements for their power are lower than in the hanging version.
In the construction of a hanging structure, rafters are made of thick timber. For the manufacture of a puff, a material similar in cross-section is required. Even taking into account the abandonment of the Mauerlat, the consumption will be noticeably higher.

It will not work to save on the grade of the material. For the supporting elements of both systems: rafters, girders, bedsteads, Mauerlat, attendants, racks, 2nd grade sawn timber is needed.

For crossbars and tension rods, grade 1 is required. In the manufacture of less critical wooden linings, the 3rd grade can be used. Without counting, we can say that expensive material is used to a greater extent in the construction of hanging systems.

Hanging trusses are assembled in an open area next to the object, then transported assembled upstairs. To lift weighty triangular arches from a bar, you will need equipment, which you will have to pay for rent. And the project for complex nodes of the hanging version is also worth something.

Video instruction on the construction of the truss structure of the hanging category:

There are actually much more methods for constructing truss systems for roofs with two slopes.

We have described only the basic varieties, which in reality are applicable for small country houses and buildings without architectural undertakings. However, the information provided is sufficient to cope with the construction of a simple truss structure.

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