The rafter system of a gable roof of a one-story house. Rafter system: types and installation for different forms of pitched roofs

The roof of the building protects it from cold weather, rain and wind. It is as important as the exterior walls and foundations. The rafter system is the supporting structure of the roof. She takes over all the loads: from structures, from snow and wind. In order to avoid problems during operation, the structure of the roof of the house must be strong and reliable. Do-it-yourself installation of the rafter system should be done only after careful preparation and study of all the necessary information.

Roof and roof

Before you start building the roof of a private house, you need to distinguish between two concepts. Non-professionals are often confused, but builders clearly separate the definitions of roof and roofing. The roof is the entire structure that separates the building from the street from above. The roof structure of a private house includes rafters, all other load-bearing elements, thermal insulation material, roofing.

Rafters - roof supporting structures

The roof is the top of the roof. She is also a roof covering... Roofing device requires careful selection of material. After all, the reliability of waterproofing and the comfort of living will depend on it.

System Requirements

To properly mount the rafter system with your own hands, you must take into account a certain set of rules. Without taking them into account, the structure will not be able to effectively resist negative impacts from the outside.

First of all, it is worth considering the strength. All elements must withstand the load without destruction... The device of the roof rafter system involves a preliminary calculation of the supporting structures for the first limiting state. It is he who checks the elements of the rafter system for strength.

The rafter system must be strong and rigid

The second requirement is rigidity... The maximum deflection is taken into account here. Roof structure wooden house or any other should not sag too much. Permissible deformations in the middle of the span are equal to the length of this span, divided by 200. Before starting construction, the structure of the rafter system must be calculated according to the second group of limiting states - for rigidity.

Do-it-yourself roof rafters are made taking into account that the structure has a low weight. Otherwise, the load on the walls and foundations increases greatly. It is for this reason that wood has become widespread as the main material. The wooden rafter system has sufficient strength, but weighs relatively little. Attention should be paid not only to the roof structure, but also to choose the roofing material correctly. It shouldn't be too heavy. Ceramic tiles have lost their popularity not only because of the cost, but also because the roof of the house, its walls and foundations must be reinforced under it.

The weight of the roofing material for a wooden truss structure should not be too large

Special requirements are placed on the quality of the material. The manufacture of wooden elements should only be carried out from good raw materials. Consider the following recommendations:

For the main elements, wood of 1 or 2 grade is used. Grade 3 can only be used for lathing and other small parts.
The rafter structures of pitched roofs are recommended to be made of conifers. They are more resistant to decay and other troubles because they contain resin. With the same cross-section, the allowable span for hardwood will be less.
Before starting work, all elements must be treated with an antiseptic. This stage of preparation allows you to prevent many troubles in the future. Also, if you wish, you can treat the wood with fire retardants. This will increase the fire resistance.
It is better to buy wood from the northern regions, which is harvested in winter period... It is this material that has the highest quality.

Parts of the structure

The rafter system diagram includes many elements. To understand the drawings and correctly perceive the information, you need to know at least the main ones. So what does a roof consist of?

Ridge, cornice and ramps - the main part of the roof

First of all, these are the ridge, the cornice and the slopes. These items are the main parts... The ridge is the uppermost part of the structure. The cornice or overhang is the lower one. Slopes are inclined surfaces that are located between the ridge and the cornice.

The construction of a rafter system requires knowledge of the supporting elements. These include:

Mauerlat - a timber that is laid along the edge of the walls of the building... Mauerlat is needed to evenly transfer the load from rafter legs that are point-based. Usually, for its manufacture, a beam with dimensions of 150x150 mm or 200x200 mm (for large buildings) is used.
Rafter legs are inclined beams that transfer the load from the roof's own weight, snow and wind to the Mauerlat... Such beams are usually installed from ridge to eaves. But upon erection hip roof items appear that have only one of the specified points. They are supported on a ridge or cornice. Such details are called worms. They usually have the same cross-section as the rafters. In fact, the rafters are rafter legs cut off on one side.
Run - a beam on which the roof elements rest... The purlin can be installed under the posts. Another option is a ridge girder (crossbar). The rafters rest on it at the top point. The cross-section of the run depends on its span, usually 200x200 mm is taken.
Slant legs are only needed for hip roofs... They are diagonal rafters supported by the Mauerlat at the corners. The section is taken to be enlarged, usually 150x200 or 100x200 mm.
The construction of a wooden roof assumes the presence of puffs, struts and struts... They are designed to reduce stress on the main components. When building a house with your own hands, it is important to remember that the racks cannot be supported on the floor span. Installation is only possible on underlying walls or on purlins thrown between walls. It is possible to mount such elements on the floor only if it is designed for such a load and is reinforced in the desired area.
The lathing is needed in order to make the base under the cover... For metal tiles and standing seam roofing, the sheathing can be thinned from boards with a thickness of 32-40 mm. For bituminous shingles, you need a solid base of boards 25-32 mm thick or moisture-resistant plywood.
In order to make the overhang of the cornice, filly are installed... They become an extension of the rafters. The filly is fastened to the rafters for a length of at least 1 m. The section of the element is usually taken 50x100 mm.

Bearing elements of the hip roof

Another element of the rafter system is the truss. It is a one-piece structure, which consists of rafters, braces, struts and struts, rigidly connected to each other. The truss has a triangular shape, and inside it is divided into several smaller triangles, which provides it with good stability.

Roof shapes

Pitched roofs come in a variety of shapes. It is worth highlighting here:

Types of rafters

There are two designs:

with layered rafters;
with hanging rafters.

The device of the roof of a wooden house is possible only with the use of the former. This is due to two rules:

hanging rafters must be rigidly attached to the Mauerlat;
in a wooden house, the rafters must be hinged to the Mauerlat.

These two statements contradict each other, therefore, the truss system of a wooden house can contain only layered elements.

Only layered rafters are mounted in a wooden house.

Inclined beams are elements that rest on the Mauerlat at the bottom point and on the ridge girder at the top... This allows you to reduce the horizontal spacing that acts on the walls when the rafters try to part and take a horizontal position. Elements can be reinforced with uprights or struts. Contractions in this case can be placed through one pair of legs.

Hanging tanks rest only at the lowest point on the Mauerlat... At the top, they just bump into each other. To ensure that the system of wooden elements does not disperse, it is imperative that puffs are made. Better to install them on each pair of legs. This option is characterized by a strong expansion effect on the outer walls, but it allows you to get more free space inside the attic.

Connections

Before you make a rafter system with your own hands, you need to carefully study the nodes. It is not worth saving time or money to build your home. Only in this case, the result will delight for many years.

The main joints of the rafters

The attachment points for the roof truss system, which deserve special attention, are represented by the following:

fastening the Mauerlat to the wall;
fastening the rafters to the Mauerlat;
fastening the rafters at the top point;
splicing rafters along the length.

Mauerlat to the wall

This knot can be done in several ways. The choice largely depends on the material of the wall. Building a building from brick, block or concrete allows the following methods to be used:

on the wire;
on staples;
on hairpins;
on anchor with device monolithic belt along the edge of the wall.

Mauerlat connection to the wall during construction brick buildings performed with anchors

Rafters to Mauerlat

Fasteners are carried out in two ways:

rigid for brick, concrete or concrete block buildings;
articulated for wooden houses.

Rigid mount can be with or without a cut. The cut is recommended to be done on the rafters, and not on the Mauerlat, as this weakens it. In both cases, the leg is rigidly fixed with nails, screws, staples or metal corners.

With rigid fastening, the cut is best done on the rafters and fixing the structure with fasteners

For a hinged mount, a special part is used - a slide... They allow the beam to mix without obstacles during the shrinkage of the building walls.

The articulated connection allows the beam to be displaced

Additionally, the rafter legs are attached to the wall. This is necessary so that the roof is not blown off by the wind. For fastening, a twist of two wires with a diameter of 4 mm is used, fixed to the wall on an anchor or a ruff. In a wooden house, twisting can be replaced with staples. Fastening is carried out on each beam or through one.

At skate level

Inserted elements rest on a ridge girder with a cut... Additionally, an overlay is made from a board on both sides. An overlay is also needed for hanging elements. It can be wooden or metal with holes for self-tapping screws.

The ridge girder and rafters are connected using a cut

Splicing rafters

There are several methods for splicing roof rafters with your own hands. The choice between them largely depends on the experience of the master. The splice is located at a distance of 0.15 of the span length from the support... In this case, not only the ridge girder and the Mauerlat, but also the struts and racks are considered as supports.

Splice rafters lengthwise

There are five ways:

butt joint;
oblique cut;
overlap;
compound legs;
paired legs.

To build a high-quality roof, you need to carefully study the technology, choose the right type of rafters and methods of connecting elements in important nodes. This is especially important when a do-it-yourself rafter system is being built.

The rafter system of any object is equivalent to the value of the load-bearing structural elements of the house. The roof plays the role of a node under which the building's stiffeners are assembled. Accordingly, when installing the roof with your own hands, you need to give the maximum value to all units of the structure, even when using simple option- gable.

Advantages of gable roofs

There are a lot of options for pitched rafter systems. Among them, the simple symmetrical one is especially popular. Why? Here are its advantages:

On the base gable roof Variations are created to reflect the specific architecture of the building.
Simple calculations that are easy to understand.
The one-piece design creates favorable conditions for dryness of the interior space and unhindered water flow, snow melting, ice formation.
The maintainability, strength and durability of the gable roof is much higher than other options.

Depending on the size, homeowners always have the opportunity to equip an under-roof space, make a full-fledged floor or an attic out of it. In a word, the gable roof is correct and profitable solution for any object, be it a residential building, a summer residence or a bathhouse.

Elements of the rafter system

Depending on the type of roof, the structural elements differ. Without knowledge of the purpose of each, it is impossible to arrange reliable coverage at home. Let's analyze in detail:

Mauerlat

The basis of the rafter system. It is a bar with a cross section of at least 150 mm, or an I-channel if the roof structure is metal. It is located on the load-bearing walls of the object. Its purpose is to distribute the load of the system evenly throughout the entire structure of the house.

Rafter leg

Constructive basic unit of the system. Together with others, it forms a truss system - strengthening the strength of the entire roof. It is made of a wooden beam, which is not inferior in cross-section to a Mauerlat or profile pipes.

Rack rafter

Vertical bar or pipes. Depending on the version of the gable roof, the struts can be located in the center and / or on the sides. They take part of the weight of the entire rafter system, which is why the cross-sectional size is 150 mm.

Truss girders

Horizontal beams placed on the racks and under the ridge to support the rafter legs. Provide structural rigidity and relieve truss stresses.

Tightens and braces

Connecting bar for rafters. The action is similar - removing the stress of the timber or metal and imparting rigidity to the structure.

Beds

Mounting support for uprights and struts. To reliably connect these two elements, a large cross-section beam is required - 150 mm or a thick-walled pipe of an impressive diameter.

Lathing beams

Elements laid perpendicular to the rafters. They are used to install the selected roof covering and create a multi-layer protective cake. The section is small - 40-50 mm.

If the planned roof structure is made of wooden beams, you should carefully consider the quality of the wood when purchasing - the beam should not have interspersed knots, be made of soft wood.

Also, the wood must have natural moisture, otherwise it will begin to dry directly in the structure of the system, cracking, deforming the roof model, depriving it of its reliability and safety.

Calculation of the rafter system

Gable roof - complex construction... The project takes into account many factors - natural nuances, wind, constant and variable loads. It is extremely difficult to independently make calculations, without special knowledge about the climate of the area, the features of the material for the manufacture of the system, the nuances of pressure distribution.

Ideally, the calculations are left to the mercy of professionals, you can independently choose only the material for the coating - the following parameter depends on its type:

Tilt angle

The minimum angle of inclination of the roof relative to the parallel to the ground is 5 degrees. However, its dependence comes from the selected roofing material. In this capacity, traditional slate, profiled sheet, flexible and metal tiles are used.

They are guided by the following rule: the steeper the slope, the more textured the roof can be.
From 5 degrees for the flooring of the roll protective insulation of the roof. The number of layers matters - up to 15 degrees three-layer coatings, above - two- and single-layer.

From 6 - ondulin.
From 11 - slate.
From 12 - corrugated board.
From 14 to 20 - metal tiles.
From 15 to 45 - soft roof.

Thus, the formed precipitation - snow, water - will not linger on the surface, although complete cleaning requires your own efforts or the involvement of specialists for the installation of the Antiled system.

Determination of rafter parameters - step, length, section

The less often the step, the more impressive the cross-section of the timber or the diameter of the pipes should be. As a rule, for load-bearing structures, this parameter is at least 150 mm, 100 mm - for country houses and accompanying construction- gazebos, baths, outbuildings.

Next, you need to set the number of rafters per slope: its length is divided by the installation step, which is from 60 to 100 cm + 1 extreme leg. By multiplying the result by 2, you get the total. Depending on the section of the timber, the amount of rafter legs and the installation pitch vary.

The length of the rafters is calculated simply if school knowledge about right triangle remained in the luggage. The rafter leg is equal to the hypotenuse of the formed figure. The calculation is as follows: A² + B² = C², where - A is the height of the roof, B is half the length of the pediment, C is the length of the rafter leg. The resulting value is always added from 30 to 70 cm on the eaves.

Types of truss systems

Before getting to work, it is important to choose the version of the rafter system for the gable roof. There are few of them, each has its own advantages and disadvantages:

Hanging

Suitable only for a standard roof width of 6 m, respectively, this is the length of the rafter leg. Fastening takes place by fixing the ends to the ridge girder and the load-bearing wall. A tightening is required to level the stress and pressure of the structure.

In addition, they will play the role of load-bearing beams. Without them, the structure will corrode under the weight. The advantages of the option are the absolute dryness of the roof surface during the off-season, and less deformation at the time of shrinkage.

Fortified

The variant is suitable for any roof width. Reliability and stability is ensured by fixing the bed to the Mauerlat. Thus, the pressure is leveled by the stand, which reduces the tension in the rafter legs. The advantage of the system is its simplicity, but the design requires large investments - additional lumber is required to equip the beds.

Hybrid

These systems are typical for multi-pitched roofs, where transitions are accompanied by numerous reinforcements, beams, uprights, slopes, slopes and other elements for the stability of the entire structure. The device is expensive and complicated, so only a professional should be involved in the project and construction. At least supervise it.

DIY gable roof installation

So, when the option of the rafter system is selected, lumber is purchased, a roof project is drawn up, you can start working. You cannot deviate from the sequence of steps. This threatens with delayed installation and loss of structural reliability.

Mauerlat mount

If the length of the bar for installing the Mauerlat is not enough, build-up is done. The ends are connected by the method of cutting in half a tree. Anchor bolts act as additional fasteners. You cannot use screws, pins or nails - they are unreliable. Wall mounting is as follows:

An indent from the edge of at least 5 cm is observed.
Holes are drilled along the wall for inserting fasteners. Similar actions are carried out with a bar.
The Mauerlat is attached to the edge with steel studs. The fastening step is more often 2 times than the distance between the rafter legs. Subsequently, before installing the main units, they are guided by metal marks.

It is important - before laying the Mauerlat, the edge of the wall is protected with waterproofing. Spread one layer even if the house is made of wood.

Manufacturing and fastening of rafters

Roof trusses are convenient because they can be assembled on the ground into a finished structure and moved to the roof. This will shorten the installation time, however, the model is heavy and lifting equipment will be required, which, of course, will increase the cost of the project.

For budget construction another way is suitable:

At the bottom and top of the rafter legs, a gash is made to attach to the Mauerlat and ridge girder. This must be done separately with each unit, after lifting the wood up.
Places for fixation are marked on the Mauerlat and a ridge girder is installed: racks are installed along the gables, on which the timber is placed. If the length is not enough, it is increased, but in a different way, unlike the Mauerlat - a board is screwed onto the joint on both sides.
Depending on the selected model of the rafter system - layered, hanging - they make cuts in the ridge beam, Mauerlat or drill holes in them for fasteners.
Next, they begin to install the rafter legs from opposite ends of the roof, gradually moving towards the middle. Between the corners of the extreme trusses, it is not bad to pull the cord to exactly match the entire horizontal part.
The rafter legs are tied together with puffs and struts. Under the ridge part, at the angle formed by the rafters, wooden lining is stuffed, and the ends themselves are tightened with bolts.

More recently, professional builders have started using sliding fasteners for roof installations. The metal plates securely hold the supporting elements and at the same time move due to shrinkage. This negates its consequences.

The work of fixing the rafters is hard and time-consuming. The time should be calculated in advance - the roof must not be left unfinished during the rainy season, otherwise the rigidity of the structure will be lost in the future due to the absorbed moisture.

Gables and lathing

The side parts of the roof - gables, are made in the form of ready-made boards from boards and are completely installed at the top. Difficulties should not arise - it is only important to carefully saw them at the required angle. It is necessary to fasten the crate only after it is known final view roofing. For example:

Under the corrugated board, the pitch of the batten will be 440 mm.
The metal tile is fixed on the lathing with a pitch of 350 mm.
A soft roof needs a continuous plywood covering.

It is important to note the places for the passage of the chimney - the crate should not come into contact with a brick or metal surface. The distance to the hot unit is at least 15 cm. Before installing the lathing, the finished roof is covered with waterproofing with allowances extending beyond the edges of the walls. Then the timber is mounted.

If it is decided to make a cake of insulation from above, then first strengthen the vapor barrier with inside, then put the selected material into the boxes formed by the rafter legs. Further, waterproofing and wind protection.

Then it is required to re-designate the contours of the rafter legs with a 20 * 20 bar and then fill in a new layer of lathing, along which the roofing material will be laid - the formation of ventilation ducts. This method will preserve the capacity of the under-roof space if the owners are going to use it for a specific purpose.

Decking of roofing material

Regardless of the type of roofing raw materials, the installation starts from the edges of the roof and leads it up, superimposing one unit on top of another. Thus, rain moisture will not get under the material.

The method of fastening depends on the type of material - soft tiles or tiles with a bituminous or polymer base - are fused. Solid profiled sheets - ondulin, metal tiles - are fixed in pre-drilled holes to the crate, using rubber pads to seal and preserve the anti-corrosion layer.

As a result: the description of the installation of the rafter system and the roof is easy only on a screen or paper. In reality, the process is complex and multifaceted. Therefore, if knowledge is not enough, it is better to invite professionals to work - their work is always covered by a guarantee.

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 various roof options, 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 already, rather, can be classified as combined.

Fragment "d" - hanging rafters are interconnected with a coupler at the Mauerlat level 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 required 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 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 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 color- 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 high 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.

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 constructed 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, a welding machine and welder skills are not required to make nodal connections.

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 frame. 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 spacer, in the second it is non-spaced.
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 the 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 racks.

For the device of the supports for the top of the layered rafters, the beds 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.

The rafters of the roof frame of 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, its 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 pitch of the rafters according to the design features of the building, banally 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 a support can be played by a girder - a wooden beam resting on racks or on the inner wall of a 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 girders and racks where the rafter legs require additional support points due to the large size of the roof.

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 chips under the Mauerlat, vertical blemishes 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 bars of the Mauerlat 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 cross-section of the purlin 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. V 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 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 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 the 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. The 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, because 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 sawn timber, 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 block 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 hems.

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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