Plan of rafters in a complex roof. Types and schemes of truss systems: an overview and recommendations for the installation of a roof truss system. Prices for building boards

Calculation truss system should be done not after the construction of the box at home, 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 slopes rectangular shape. 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 posted 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 commonly used during construction attic rooms, allows you to significantly increase the volume of attic space. 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 efforts from 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.

Boards are calculated by bending resistance, taking into account the data obtained, species and types of wood are selected, the distance between the legs, additional elements increase sustainability. 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, rest against several load-bearing walls or interior partitions. Purpose - simplification of the manufacture of a complex truss system, the creation of new points of transfer of loads from various types 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 crate is selected taking into account technical parameters 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 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.

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 specifications. Easiest metal roofs, the heaviest of all natural slate materials, ceramic or cement-sand piece tiles.
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 varies 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: the 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.
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.

1) Apply the coordination axes of the building.

2) Draw the outline of the walls.

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

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

5) At an angle of 45 °, draw diagonal rafter legs from the corners of the building.

6) Lay a bed along the inner wall of the building and show the upper run.

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

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

9) Install the racks at intervals of 3000 - 6000 mm, starting from the support node.

10) With a building width of more than 12 m, lay a crossbar to the rafter legs.

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

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

The rafters are connected using fixing bolts, staples or nails.

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

The step of roof trusses with spans up to 9 m is 3-4 m, with spans over 10 m - 1.5-2 m.

Hanging rafter schemes

Dormer windows suit in pitched roofs oh for lighting, ventilation of the attic, exit through them to the roof. They can be semicircular, triangular, rectangular. Lighting - through the glazed sash of the binding with a size of at least 0.6 × 0.8 m. For ventilation, wooden louvered grilles are used, located adjacent to the glazed sash of the dormer window. Dormer windows must be placed so that through ventilation is ensured. 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 dormer windows

a - triangular; b - semicircular; c - rectangular; d - polygonal

1 - glazed parapet; 2 - louvre

The erection of the roof is one of the most important 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, gable can be attributed to the most popular, simply because of the relative simplicity of its construction. However, behind this "simplicity" lies a lot of different nuances, the need to carry out certain calculations and follow technological rules. However, this publication has the main task: to show that installing the rafters of a gable roof with your own hands is a completely doable task, even for a novice builder.

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

General arrangement of a gable roof

Basic concepts

Structural elements of the gable roof truss system

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

1 - Mauerlat. This is a board or beam 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, creating conditions for reliable fastening of the rafter legs at their lower fulcrum.

2 - rafter legs installed in pairs. They become the main load-bearing parts of the entire roof system - it is the rafters that set the steepness of the slopes, will be the basis for attaching the batten, 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, and round timber can also be used. About the section of lumber, which will be sufficient to ensure that all possible loads can be guaranteed, will be discussed below.

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

To form a cornice overhang, the rafters are extended with “fillies”

3 - skating run. It can be a beam, a board or even a composite structure. The run runs along the entire line of the ridge and serves to securely connect the upper points of the paired rafter legs, connect all rafter pairs in order to impart overall rigidity to the entire roof structure. IN various options roofs, this run can be rigidly supported by racks, or tied only to the connection node of the rafter legs.

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

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

6 - and this beam simultaneously performs the role of a bed. This is a beam that runs along the entire length of the roof, which is a support for installing additional reinforcement parts for the truss system. The bed can be installed as shown in the figure (like a floor beam), or it can be rigidly laid on a capital partition inside the building.

7 - racks (headstock) - additional vertical supports of the rafter legs, preventing their deflection under the influence of external loads. Racks at the top can rest against the rafters themselves, or against an additional run, longitudinally connecting the rafter legs at a certain height.

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

Some differences between hanging and sloping gable roof systems

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 principles of construction are combined. What is the fundamental difference?

Laminated rafter system

This design 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 drains are supported, supporting the ridge run. Thus, the rafter legs are "leaned" on vertical support which makes the whole system as strong as possible.

This scheme is the most popular because of its reliability and relative ease of implementation. If it is possible to create an additional point of support in the center, then why not take advantage of this? True, if it is planned to place a living space in the attic, then vertical racks can sometimes become a hindrance. However, their presence is also sometimes “beaten up”, using, for example, an internal light partition for mounting.

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

Fragment “a” shows the simplest option, which, by the way, on short rafter lengths (up to 5 meters) may not even have struts shown - a row is enough B-pillars under the ridge

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 main wall does not have to be located exactly in the center, under the ridge. It is also possible 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 can be supported in a large building, but with two main partitions inside. The distance between such parallel beds can reach up to a third of the width of the building.

Hanging rafter system

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

It immediately catches the eye 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 with a distance between the bearing walls on which the Mauerlat is fixed, no more than 7 meters. Installed puffs only partially relieve the load from the external walls.

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

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

Option "g" - for the same size house (up to 6 meters). The puff (bolt) in this case is shifted upwards, and is often used for filing the ceiling of the attic.

Options "e" and "h" are designed for a span between walls up to 9 meters. Multiple puffs may be used (or top puff in combination with bottom floor beam). Another approach is to install racks under the ridge run, by analogy with a layered system. Only as a lower point of support, it is not a bed on the main partition that is used, but the racks are supported by a puff or a floor beam. To call such an 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 two schemes is expressed in the "and" variant, which is designed for large spans, from 9 to 14 meters. Here, in addition to the headstock, diagonal struts are also involved. Often, such trusses are generally assembled on the ground, and only then they are lifted and set in place, connected to each other, thereby forming the entire roof frame.

So, in preparation for the construction gable roof it is necessary to study the principles of the device of a particular system, evaluate their advantages and disadvantages, choose the best one for your conditions and draw up a graphic working scheme. It will also be needed when purchasing. required material, and for the production themselves installation work. 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 circuit diagram gable roof devices to highlight those parameters that need to be calculated.

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

The initial data is the length of the side of the house along the gable 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 on the type of roofing in advance - 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 - and elongation of the rafters to form a cornice overhang of the required width (l).
Calculate the total loads that fall on the truss system in order to determine the optimal cross-section of lumber for the manufacture of rafters, their installation step (red color - S) and the allowable span length between the support points. All these parameters are closely interconnected.
When these calculated values \u200b\u200bare on hand, it is already easy to draw up a graphic diagram, determine the need and optimal arrangement of reinforcement 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 slope angle of the slopes can be determined by the owners according to various evaluation criteria:

For purely aesthetic reasons - when the appearance of the building becomes "at the forefront". Many people like roofs with a high ridge, but at the same time we must not forget that such a roof increases dramatically wind load. Yes, and 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 assessment parameter may become decisive.
For reasons of useful use of the attic space. With a gable roof scheme, in order to achieve the maximum attic area, it is necessary to build slopes with a very steep slope, that is, with the same consequences as mentioned above.

Finally, there may be a completely opposite approach - for reasons of economy, make a roof structure with a minimum height in the ridge. But in this case, you will have to focus on the minimum allowable slope angles for a particular type of roofing. To reduce the steepness below the indicators recommended by the manufacturer 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). At the heart of the vast majority of nodes of any roofing system is a triangle, which, in turn, obeys strict geometric (more precisely, trigonometric) laws.

So, in our case, the width of the roof along the gable line is known. If the roof is symmetrical, then the ridge will be located 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 asymmetrical 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 tangents and carry out calculations manually, a calculator is placed below, in which the necessary tabular values \u200b\u200bare already entered.

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

Rafter system design

Drawing up a rafter plan for a hipped roof, a gable roof or for another structure is a complex and responsible process at the same time. That is why a special program is used to draw up the drawing, it is required to take into account the calculations of snow, wind loads, weight roofing material, 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 rafter plan, parameters such as:

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

The design scheme of the rafter legs depends on:

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

The plan of the rafters should be drawn up taking into account all the parameters. For the construction of the roof, layered and are used. Leg design can be triangular to provide maximum rigidity and strength. If the farms will be used complex, then you will additionally have to purchase:

struts;
crossbars;
puffs;
additional racks;
truss beams.

Laminated rafters are used for houses where the middle one is taken as a load-bearing wall. includes 2 rafter legs, a power plate on which they rest from below, and a ridge run for support from above, as well as racks. Racks are attached to the bed, it is placed on the inside 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.

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

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

The production of hanging rafters is more complex 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.

What does a truss system plan include?

The drawing is made 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 design of the truss system to the main walls of the future house.
The plan draws all the channels of the ventilation and smoke systems, pipelines, which during the construction process will go through the truss system.
A plan is being developed for the future chosen form of the roof. When drawing up a sketch, it is required to take into account the location of the walls.

The diagram must indicate such elements that the roof has: roof ribs, valleys, skates, and so on. Be sure to take into account what shape the slopes will take, the direction and angle of the slope. The drawing indicates the location of gables, dormer windows, if any.

Using the plan of the roofing system, the builders will build a solid and reliable structure. The following parameters must be indicated on the plan:

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

If it is planned to build a metal roof truss system, i.e. special galvanized beams, it is necessary to use completely different programs designed for design. Only a specialist can do this, 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 the heater. For example, for a four-slope roof, which is constructed from wood, the rafter pitch can be:

In the manufacture of rafter legs from beams, the step is 150-180 cm.
In the manufacture of rafter legs from edged boards, the step is 100-120 cm.

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

In some, in order to pass 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 adjacent legs. For fasteners in this case, washed down. Scheme of the truss system.

Technology rules

For a hipped roof or other configuration, small dormer windows are provided in the gables to provide proper ventilation attic space, especially in the warm season. For example, for a four-pitched roof, it is necessary to display diagonal slanted rafter legs on the rafter plan, and the sprigs resting on them. It is important not to forget about the dormers, which will be located on the hips.

If it is planned to build an attic living space, 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 connect them together, to ensure correct and clear design. As a result, each node will be clearly connected with the rest, the design will be stable and reliable.

The project must have the affixed values of the axes of all elements of the building and the structure of the truss system. Wall thickness data is attached to the axial parameters, dimension lines are applied to the project, which are performed to determine the step for the beam. Inside, the distances between the individual racks are indicated, chimneys. Value must be entered cross sections for each element.

Drawing up a plan for a hipped roof or any other is a prerequisite during the design of a house. The truss system is one of essential elements Houses. It depends on how correctly the drawing is drawn up and the calculations are carried out, whether the structure will be strong and reliable. Therefore, it is best to entrust the preparation of such a plan to specialists, and not rely on one's own strength in the absence of proper experience.

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 are the formation of even 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 about the rules and principles of its construction is needed. The information is useful both for those who are building a gable roof truss system with their own hands, and for those who decide to resort to the services of a hired team of builders.

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

The second is constructed from rolled metal: channel, profile pipe, I-beam, corner. There are combined structures with steel most loaded parts and wood 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. Disappointing need for the use of welded joints. Most often, industrial buildings are equipped with steel rafters, less often private change houses assembled from metal modules.

In the case of self-construction of truss structures for private houses, wood is a priority. It is easy to work with it, it is lighter, “warmer”, more attractive in terms of environmental criteria. In addition, nodal connections do not require 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, headstocks, girders, puffs, even 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 gable roof frame are divided into:

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

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

For the arrangement of supports for the top of the layered rafters, beds and girders are mounted. In reality, the truss structure is much more complicated than the elementary patterns described.

Note that the formation of a gable roof frame can generally be carried out without a truss structure. In such situations, the alleged planes of the slopes are formed by slegs - beams laid directly on the bearing gables.

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

Subtleties of fastening 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 wooden frame, and with walls made of these materials, a waterproofing layer of roofing material, waterproofing, etc. is mandatory 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 cutting 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 the wooden beams be determined by the project. The designer will give clear calculation justifications for the geometric parameters of the board or beam, taking into account the entire range 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 roof structure.

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

The installation step of the rafters determines the type and weight of the roofing. The heavier it is, the smaller 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 a profiled sheet, 1.5-2.0 m is acceptable.

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-lattice device. True, it will increase both the weight of the roof and the construction budget. Therefore, it is better to deal with the step of the rafters before the construction of the rafter system.

Craftsmen calculate the pitch of the rafters according to design features buildings, tritely dividing the length of the slope into equal distances. For insulated roofs, the step between the rafters is selected based on the width of the thermal insulation boards.

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

Rafter structures of layered type

Rafter structures of the layered type are much simpler in execution than their hanging counterparts. A justified plus of the layered scheme is to provide full ventilation, which is directly related to the longevity of the service.

Distinctive design features:

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

The minus 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 the organization of useful premises is not supposed to be in it, then the layered construction of the truss system for the installation of a gable roof should be preferred.

A typical sequence of work on the construction of a layered truss structure:

First of all, we measure the height of the building, the diagonals and the horizontalness of the upper cut of the skeleton. When detecting vertical deviations of brick and concrete walls, we eliminate them with a cement-sand screed. Exceeding the heights of the log house we squeeze. By placing chips under the Mauerlat, vertical flaws can be dealt with if their magnitude is insignificant.
The floor surface for laying the bed must also be leveled. He, the Mauerlat and the run must be clearly horizontal, but the location of the listed elements in the same plane is not necessary.
We process everything wooden details structures before installation with flame retardants and antiseptics.
on concrete and brick walls we lay waterproofing for the installation of a Mauerlat.
We lay the Mauerlat beam on the walls, measure its diagonals. If necessary, we 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. Fasteners are made either with brackets to 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 run will be based only on racks without lying down, the marking procedure is carried out only for these columns.
We install the bed on a two-layer waterproofing. We fasten it to the base with anchor bolts, with inner wall connect with wire twists or staples.
We mark the installation points of the rafter legs.
We cut out racks according to uniform sizes, because our bed is set to the horizon. The height of the racks must take into account the dimensions of the section of the run and the bed.
Installing racks. If provided by the project, we fix them with spacers.
We lay the run on the racks. We check the geometry again, then install the brackets, metal plates, wooden mounting plates.
We install a trial rafter board, mark the places of trimming 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. Folk craftsmen for marking usually prepare a pair of slats, the length of which is equal to the gap between the rafters.
According to the markup, we install the rafter legs and fasten them first at the bottom to the Mauerlat, then at the top to the run 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 done flawlessly, the layered boards are mounted in random order.

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

The installation of the truss structure is completed by installing the filly, 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 beyond” the contour of the building by 50 cm. If the organization of the visor is planned, separate mini-rafters are installed under it.

Another useful video about the construction of a gable truss base with your own hands:

Hanging truss systems

The hanging type of truss systems is a triangle. The two upper sides of the triangle are folded by a pair of rafters, and the puff connecting the lower heels serves as the base.

The use of tightening allows you to neutralize the effect of the thrust, therefore, only the weight of the crate, the roof, plus, depending on the season, the weight of precipitation, acts on walls with hanging truss structures.

The specifics of hanging truss systems

Characteristic features of hanging type truss structures:

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

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

The first of these is the limitation on the steepness of the slopes: their slope angle 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 cornice nodes.

Among other things, the angle of the truss truss will have to be set with jewelry accuracy, because. the axes of the connected components of the hanging truss 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 long-span hanging systems

Puff - the longest element of the hanging rafter structure. Over time, it, as is typical of all lumber, deforms and sags under the influence of its own weight.

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

To prevent sagging in the installation scheme of the truss system for a large-span gable roof, there is a very significant component. This is a pendant called a grandmother.

Most often, it is a bar attached with wooden surfs to the top of the truss truss. You should not confuse the headstock 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 ah does not apply.

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

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

In an improved hanging system of this type, the headstock is complemented 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 truss system pleases with stability with a slight and not too expensive upgrade.

Hanging type for attics

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

It is attached to the rafters by cutting with a semi-frying pan with a duplication of a bolt. It is protected from sagging by installing a short headstock.

A noticeable drawback of the attic hanging structure is the need for accurate calculations. It is too difficult to calculate it on your own, 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 construction for both types of truss systems cannot be the same, because:

In the construction of a layered structure for the manufacture of rafter legs, a board or beam of 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, the rafters are made of thick timber. For the manufacture of puffs, a material similar in cross section is required. Even taking into account the rejection of the Mauerlat, the consumption will be significantly higher.

Saving on the grade of material will not work. For the bearing elements of both systems: rafters, purlins, beds, Mauerlat, attendants, racks, lumber of the 2nd grade is needed.

For crossbars and puffs working in tension, you will need the 1st grade. In the manufacture of less responsible wooden slips, the 3rd grade can be used. Without counting, we can say that in the construction of hanging systems, expensive material is used to a greater extent.

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, for which you will have to pay rent. And the project for complex nodes of the hanging version is also worth something.

Video instruction on the installation of a truss structure of a hanging category:

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

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