How to make rafters for a house options. Roof truss system and features of its structure. Rafter legs - ribs of the roof skeleton

Roofing structures are one of the most difficult components to design and install in a residential structure. The roof is the first to take the “blow”, protecting the house from precipitation, wind and cold, therefore the comfort of all household members depends on its tightness, durability, and quality. The basis of a reliable roof is the rafter system, which gives the structure its shape, defines optimal slope, and also serves for fastening waterproofing material. The composition and relative position of the frame elements depend on the roof configuration. In this article we will tell you what types of rafter systems there are, as well as how they differ from each other.

Rafter system - a set of supporting elements that support the geometry of the roof, frame roofing structure, giving it rigidity and the desired slope. The composition, section thickness, and location of the parts of the “backbone” of the roof are determined using calculations that take into account permanent and temporary loads. The rafter frame performs the following functions that determine the functionality of the roof:

1. Sets the geometry, slope. Rafter legs the frame gives the roof the required angle of inclination and shape, facilitating the easier removal of snow or precipitation from the surface. It is the frame that determines how many gables or slopes the roof will have, which means it is this structural element that determines its appearance.
2. Serves as a basis for attaching waterproofing material. The rafter frame sheathing is used to secure the finishing roof covering.
3. Evenly distributes the weight of the roof. The interconnected elements of the rafter system evenly distribute and then redirect the load from the finishing coating and the weight of the snow mass between the load-bearing walls of the structure, preventing distortion or deformation of the structure.
4. Ensures the functioning of the roof. The structure of the frame, taking into account the characteristics of the roof and roof covering, provides support, aeration and protection from condensation.

Please note that a well-designed rafter system is the key to the durability, reliability and mechanical strength of the roof, so its design and installation is trusted to professional architects. Experienced craftsmen believe that a high-quality frame is much more important than the final roofing covering, so you should not skimp on it.

Criterias of choice

The design of the rafter system is characterized by a large number of auxiliary elements and increased complexity. It is compiled according to the calculation of permanent and temporary loads acting on the structure, a project that takes into account the selected roofing material, as well as environmental factors. When choosing the type of rafter frame, the following criteria are taken into account:

• Climatic conditions in the region where construction is taking place. In order for the roof to withstand the weight of snow and water during heavy rainfalls, the average annual precipitation in winter and summer is determined.
• Wind load. To select the optimal roof structure, the prevailing wind pattern in the construction area is determined, and the average speed of air gusts is also taken into account.
• The nature of the use of space under the roof. At this stage, it is determined whether a residential attic will be equipped in the under-roof space or an unheated attic.
• Type of finishing coating. For each material, the optimal angle of inclination of the slopes is calculated, taking into account its shape and method of fastening.
• Developer's budget. The rafter system is one of the most expensive parts of the roof structure in terms of material and work, so the type is determined by the financial capabilities of the developer.

Experienced craftsmen believe that it is useless to fight nature, you will still be a loser, therefore, when choosing the type of rafter frame, the climatic conditions in the area where construction is taking place are at the forefront. If the region is windy, then the angle of inclination of the slopes is made flat, and if it is snowy, it is steeper.

Materials

Rafter system – required element pitched roofs of any shape and configuration, consisting of vertical supports, horizontal ties and rafter legs, providing support and reliable fastening to the roofing material. The material used to make the frame must be light in weight, high strength, load-bearing capacity, and also resistant to moisture. The most suitable options are:

1. Wood. Wood – natural, environmentally friendly safe material, which is lightweight and durable. For the manufacture of the frame, square bars of 100x100 mm or 150x150 mm, and hardwood boards with a section of 50x150 mm are used. Significant disadvantage wooden elements frame is that they bend under their own weight when they are long, and also have poor resistance to moisture.
2. Metal. Metal rafter systems are more expensive than wooden ones; they are mainly used for large area slopes and large weight of roofing material. The high load-bearing capacity of a metal profile or corner allows you to increase the pitch between frame elements without losing the strength of the structure. To reduce the likelihood of rust spreading, corrosion-resistant types of metal are used.

Note! Wood is considered the most suitable material for the manufacture of roof truss frames for residential buildings, since it has 3 important qualities: Light weight, durable, breathable. To increase the resistance of wood to moisture, it is necessary to treat the elements of the rafter system with a deeply penetrating antiseptic.

Device

The structure of the roof truss system consists of many interconnected elements that, supporting each other, give the structure rigidity and the necessary strength, and also distribute the weight of the roofing material evenly between the load-bearing supports. The composition of the frame, the cross-sectional size of individual elements and their placement depend on the type of finishing coating, the slope of the slope and the method of using the under-roof space. Typically the frame consists of:

• Mauerlat. Mauerlat is the name given to the rafter beam, which is attached on top of the upper crown or a number of load-bearing walls of the house. It is made from durable, solid softwood. The Mauerlat is secured using long metal pins or anchor bolts.
• Lezhenya. A wall is called a mauerlat beam located not on external load-bearing walls, but on internal partitions. Placed on the bench B-pillars, supporting the roof ridge.
• Stoeck. Racks are the vertical supporting elements that support the ridge girder or the central part of the rafter legs of the frame.
• Rafters. The rafter legs rest on the mauerlat and ridge girder, located at an angle to the base of the roof.
• Bolt and tightening. These terms refer to the horizontal frame elements that connect the rafter legs together in pairs. The crossbar is located at the top of the rafters, directly under the ridge; it is thicker and stronger than the tie, which is located much lower.
• Podkosov. The brace is installed at an angle to the rafters to prevent them from bending under their own weight. One end of them rests against the leg, and the other - against a stand or puff.

Important! The simplest rafter system consists only of a mauerlat, rafters and a ridge girder. As the complexity of the roof increases, the number of additional elements, strengthening the structure, as well as compensating for deflection and expansion loads.

Kinds

The configuration of the roof frame depends on the architectural features of the structure being covered. The roof must take into account the number of load-bearing supports inside or outside the house in order to evenly distribute the load placed on them. The following types of rafters are distinguished:

Please note that the final appearance of the rafter frame is made of wooden or metal elements depends on the number of slopes and type of roof. Most simple options They consider single-pitched and double-pitched roofs, and hip, half-hip, and hip roofs are considered complex.

Video instruction

Rafters perform a number of significant roofing functions. They set the configuration of the future roof, absorb atmospheric loads, and hold the material. Among the rafter's duties are the formation of smooth planes for laying the covering 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 design. The information is useful both for those who construct 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.

Wooden and metal beams are used to construct the rafter frame for pitched roofs. Source material For the first option, use a board, log, timber.

The second is constructed from rolled metal: channel, profile pipe, I-beam, angle. Eat combined designs with the most heavily loaded steel parts and wood elements in less critical areas.

In addition to its “iron” strength, metal has many disadvantages. These include thermal qualities that are unsatisfactory to the owners of residential buildings. The need to use welded joints is disappointing. Most often, industrial buildings are equipped with steel rafters, and less often, private cabins assembled from metal modules.

In the matter of independent construction of rafter structures for private houses, wood is a priority. It is not difficult to work with, it is lighter, “warmer”, and more attractive in terms of environmental criteria. In addition, to perform nodal connections you will not need welding machine and welding skills.

Rafters - a fundamental element

The main “player” of the frame for constructing a roof is the rafter, which among roofers is called a rafter leg. Beams, braces, headstocks, purlins, ties, even a Mauerlat may or may not be used depending on the architectural complexity and dimensions of the roof.

Rafters used in the construction of gable roof frames are divided into:

• Layered rafter legs, both heels of which have reliable structural supports under them. The lower edge of the layered rafter rests against the mauerlat or the ceiling crown of the log house. The support for the upper edge can be a mirror analogue of the adjacent rafter or a purlin, which is a beam laid horizontally under the ridge. In the first case, the rafter 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 - a tie. The latter connects the two lower heels of adjacent rafter legs, resulting in a triangular module called a rafter truss. Tightening dampens the tensile processes, so that only vertically directed load acts on the walls. Although a structure with hanging rafters is braced, the bracing itself does not transmit to the walls.

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

To support the top of the layered rafters, planks and purlins are installed. In reality, the rafter structure is much more complex than the elementary templates described.

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

However, what interests us now is specifically the structure of the rafter system of a gable roof, 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 a Mauerlat, which in turn is fixed with anchors.

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

The top of brick walls is sometimes specially laid out so that along the outer perimeter there is something like a low parapet. This is so that the mauerlat placed inside the parapet and the walls do not push apart the rafter legs.

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

How to do without mind-boggling calculations?

It is highly desirable that the section and linear dimensions wooden beams were determined by the project. The designer will provide clear calculation justification for the geometric parameters of the board or beam, taking into account the entire range of loads and weather conditions. If available home handyman there is no design development, its path lies on the construction site of a house with a similar roofing structure.

You don’t have to pay attention to the number of floors of the building being constructed. It is easier and more correct to find out the required dimensions from the foreman than to find out them from the owners of a shaky self-built building. After all, in the hands of the foreman is documentation with a clear calculation of the loads per 1 m² of roof in a specific region.

The installation pitch 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 corrugated sheets 1.5-2.0 m is acceptable.

However, even if the pitch required for proper 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 understand the pitch of the rafters before constructing the rafter system.

Craftsmen calculate the pitch of the rafters according to the design features of the building, simply dividing the length of the slope into equal distances. For insulated roofs, the pitch between the rafters is selected based on the width of the insulation slabs.

You can find it on our website, which may also help you a lot during construction.

Rafter structures of layered type

Layered rafter structures are much simpler to construct than their hanging counterparts. A reasonable advantage of the layered scheme is to ensure adequate ventilation, which is directly related to long-term service.

Distinctive design features:

• It is mandatory to have support under the ridge heel of the rafter leg. The role of support can be played by a purlin - a wooden beam resting on posts or on the internal wall of the building, or the upper end of an adjacent rafter.
• Using a Mauerlat for erecting a truss structure on walls made of brick or artificial stone.
• The use of additional purlins and racks where the rafter legs, due to the large size of the roof, require additional support points.

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

If the attic is cold and it is not intended to organize useful rooms, then the layered structure of the rafter system for installing a gable roof should be given preference.

Typical sequence work on the construction of a layered truss structure:

• First of all, we measure the heights of the building, the diagonals and horizontality of the upper cut of the frame. If we identify vertical deviations in brick and concrete walls, we eliminate them with a cement-sand screed. Exceeding the heights of the log house is cut off. By placing wood chips under the mauerlat, vertical flaws can be combated if their size is insignificant.
• The floor surface for laying the bed must also be leveled. It, the Mauerlat and the girder must be clearly horizontal, but the location of the listed elements in the same plane is not necessary.
• We treat all wooden parts of the structure with fire retardants and antiseptics before installation.
• We lay waterproofing on concrete and brick walls for installation of the Mauerlat.
• We lay the mauerlat beam on the walls and measure its diagonals. If necessary, we slightly move the bars and turn the corners, trying to achieve the ideal geometry. Align the frame horizontally if necessary.
• We mount the Mauerlat frame. The beams are joined into a single frame using oblique notches; the joints are duplicated with bolts.
• We fix the position of the Mauerlat. Fastening is done either with staples to wooden plugs installed in advance in the wall, or with anchor bolts.
• Mark the position of the prone position. Its axis should recede from the mauerlat bars at equal distances on each side. If the run will rest only on posts without supports, we carry out the marking procedure only for these posts.
• We install the bed on a two-layer waterproofing. We fasten it to the base with anchor bolts, with internal wall we connect with wire twists or staples.
• We mark the installation points of the rafter legs.
• We cut out the racks according to one size, because Our bench is pointed at the horizon. The height of the racks should take into account the cross-sectional dimensions of the purlin and beam.
• We install racks. If provided by the design, we secure them with spacers.
• We lay the purlin on the racks. We check the geometry again, then install brackets, metal plates, and wooden mounting plates.
• We install a test rafter board and mark the cutting areas on it. If the Mauerlat is set strictly to the horizon, there is no need to adjust the rafters on the roof after the 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 slats, the length of which is equal to the clearance 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 purlin to each other. Every second rafter is screwed to the Mauerlat with a wire bundle. IN wooden houses The rafters are screwed to the second crown from the top row.

If the rafter system is made flawlessly, the layer boards are installed in any order.

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

The installation of the rafter structure is completed by installing fillets, if the length of the rafter legs does not allow forming an overhang of the required length. By the way, for wooden buildings the overhang should “extend” the contour of the building by 50 cm. If you plan to organize a canopy, separate mini-rafters are installed under it.

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

Hanging rafter systems

The hanging variety of rafter systems is a triangle. The two upper sides of the triangle are folded by a pair of rafters, and the base is the tie connecting the lower heels.

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

Specifics of hanging rafter systems

Characteristic features of hanging type rafter structures:

• The obligatory presence of a tie, most often made of wood, less often of metal.
• Possibility to refuse to use the Mauerlat. A timber frame can be successfully replaced by a board laid on double-layer waterproofing.
• Installation of ready-made closed triangles – trusses – on the walls.

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 them is restrictions 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 detailed calculations for the proper installation of cornice units.

Among other things, the angle roof truss You will have to install it with pinpoint precision, 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 backing board replacing it.

Subtleties of long-span hanging systems

The tie is the longest element of a hanging rafter structure. Over time, as is typical for all lumber, it becomes deformed and sags under the influence of its own weight.

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

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

Most often it is a block attached with wooden pegs 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 installation of racks as supports in hanging systems ah does not apply.

The bottom line is that the headstock hangs, as it were, on the ridge assembly, and a tightening is attached to it using bolts or nailed wooden plates. To correct sagging tightening, threaded or collet-type clamps are used.

The tightening position can be adjusted in the area of ​​the ridge assembly, and the headstock can be rigidly connected to it by a notch. Instead of a block on non-residential attics For the manufacture of the described tension element, reinforcement can be used. It is also recommended to install a headstock or hanger where the tie is assembled from two beams 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 proper placement of vector loads acting on the system.

As a result, the rafter system is stable with minor and not too expensive modernization.

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 completely reasonable move has additional advantages: it allows you to use the puffs as a basis for lining the ceiling.

It is connected to the rafters by cutting with a half-pan and duplicating with a bolt. It is protected from sagging by installing a short headstock.

A noticeable disadvantage of the hanging attic 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 construction for both types of rafter systems cannot be the same, because:

• In the construction of a layered structure, a board or beam of small cross-section is used to make rafter legs. Because layered rafters have two reliable supports underneath 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. To make a tightening, a material with a similar cross-section is required. Even taking into account the abandonment of the Mauerlat, the consumption will be significantly higher.

It will not be possible to save on the grade of material. For the load-bearing elements of both systems: rafters, purlins, beams, mauerlat, headstocks, racks, 2nd grade lumber is needed.

For crossbars and tensile ties, grade 1 will be required. In the manufacture of less critical wooden overlays, grade 3 can be used. Without counting, we can say that in the construction of hanging systems, expensive material is used in greater quantities.

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

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

There are actually many more methods for constructing rafter 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 tricks. However, the information presented is enough to cope with the construction of a simple truss structure.

They say that the roof of a house is the fifth facade. Any owner of a country cottage knows well that the overall perception of the building depends on how well the roofing is chosen.

We have already told users of our site about the features of choosing a roofing covering.

But the roof is only the visible part of a complex system called the roof. The basis of any roof is a reliable and properly designed rafter system.

In this material, FORUMHOUSE experts will talk about the main nuances of constructing a rafter system for a wooden and stone house.

From this article you will learn:

• Where does the construction of a rafter system begin?
• What nuances need to be taken into account when installing the rafter system of a stone and wooden structure;
• Which structural elements rafter system compensates for the shrinkage of a wooden house;
• What features does the rafter system of a log house have?
• What is a Mauerlat and why is it needed in a stone structure?
• What are the requirements for the materials of a wooden rafter system?
• What is a rafter system built according to LSTK technologies.

General principles for choosing a rafter system for a stone and wooden cottage

Often, novice developers believe that the choice of rafter system design can be left “for later,” when the walls have already been erected. Practice shows that this is fundamentally wrong. The roof even country house is a complex system consisting of many elements. The design of rafters must begin at the design stage of the house.

Company Manager "DDM-Stroy" Vera Vavilova, Moscow:

– The rafter system is the basis (skeleton) of the roof of the house. The quality and durability of the roof directly depends on how well it is done. The manufacture of this structure, especially complex ones, must begin with its design. This is the only way that will allow you to take into account all the nuances and install it efficiently.

The service life of the roof largely depends on how well this structure is chosen and installed. It is also necessary to maintain a balance between functionality and design delights.

Director of company " Smart-Stroy" Pavel Orlov:

– Designing a rafter system begins with choosing the type of roof - mansard or cold attic. For mansard roofs, the angle of the rafters is 35 degrees and above. For a cold attic, the base angle of the rafters is 25 degrees.

The simpler the roof shape, the simpler design, the faster it is to manufacture, and the less likely builders are to make a mistake. Therefore, it is cheaper to build and easier to operate a roof that has a simple shape. Big square roofs, the presence of bay windows, and the complex polygonal shape of the building significantly complicate and increase the cost of the design of the rafter system - it requires competent design and calculation.

The most cost-effective rafter system is for a simple gable roof with a slope angle of at least 25 - 30 degrees.

The main factors that influence the complexity of manufacturing and the final price of the design:

• Type of finishing roof covering. The choice of one or another coating determines the composition of the roofing pie, the type of sheathing and the load on the rafter system. The most popular roofs are metal tiles, soft roofing, CPC (cement-sand tiles), ceramic or seam roofing;

• Roof inclination angle. It determines the loads, which is a major factor in structural design;

• Will the structural elements (decorative element) be visible or will it be completely hidden behind the ceiling cladding;

• Large overhangs on the roof significantly increase the cost of the rafter system.
  If the design of the last floor of the house provides for large unsupported spans, this entails an increase in cost and complexity of the structure. In this case, depending on the distances, the rafter system is performed using trusses.

• The presence of large fireplace chimneys, skylights and other passage elements in the project significantly affects both the complexity of manufacturing the structure and its price.

The design of a rafter system (especially a complex one) should be carried out by a person with relevant experience. This design is always calculated for a specific building. The common approach – “I’ll make a rafter like my neighbor’s” – leads to disastrous construction results. The rafter cannot withstand the loads, which ultimately leads to expensive alterations.

Design begins with collecting the expected roof loads.

1. Constant values, including the total weight of the roofing covering, thermal insulation material and fastening elements;

2. Temporary quantities. These are the loads that climatic conditions, especially snow and wind, have on the roof.

Designers set the design pitch of the rafters in accordance with the expected load. Let's see how true this is.

Pavel Orlov:

– In my opinion, it is better to choose the pitch of the rafters for attic, well-insulated roofs based on the size of the insulation - so that the distance between the rafters is 1 cm less than the width of the insulation. This will make it easier to install.

The main load for which the rafter system is calculated is snow. Usually all such structures are designed with a margin, but if there is any doubt (it is intended to install a heavy roofing covering - natural tiles etc.), you can slightly reduce the pitch of the rafters.

Although the snow load is variable, the rafter must be calculated taking into account the totality of all loads acting on it. The calculation must be carried out not “back to back”, but with some reserve in case of heavy precipitation (prolonged snowfall) or increased wind load.

The “work” of the rafter system is significantly influenced by the choice of material for the walls of the house.

Features of the rafter system in a wooden and stone house

The main difference between the rafters of a stone house and a wooden one is that stone walls have a structure that is not subject to shrinkage and deformation.

Pavel Orlov:

– The rafters of a stone house do not need deformation elements, since stone house practically does not shrink. main feature rafter system of a stone house is the need to securely fasten the Mauerlat. In wooden houses, the role of the mauerlat is played by the wall.

Mauerlat is a roofing element (paired boards 50x150, timber sized 100x150 or 150x150), which is laid along the entire perimeter of the upper wall of the house. The lower part of the rafters rests on the mauerlat. Thus, the Mauerlat redistributes the point load transmitted from the rafters to the entire area of ​​the upper part of the wall.

Also, when designing the truss system of a stone house, it is necessary to take into account the thickness of the walls.

Pavel Orlov:

– The design requires calculation of the permissible lateral load of the rafters on the wall with a fixed Mauerlat.

A thin and tall wall can withstand less lateral load. This requires the use of additional elements for the supporting structure of the rafters - supporting posts and purlins.

Wooden houses also have their own nuances that must be taken into account when manufacturing the rafter system.

Vera Vavilova:

– The main feature is that the walls, which are the basis for the rafters, shrink and change their geometry as the weather, temperature and humidity change outside and inside the house.

The main element that compensates for the shrinkage of the walls relative to the rafters is a sliding support (also called a sliding support). Sliding support necessary in order to compensate for distortions of the rafter structure resulting from wood shrinkage natural humidity.

A sliding support is a composite fastener that includes a bent plate and an angle with a guide.

When the house shrinks, the rafter slides along the guide, thus compensating for all distortions general design rafter system of the house. The sliding part of the support is attached to the rafter beam so that there is a gap between it and the rafter. And the corner with the guide is screwed to the beam.

The slide must be installed strictly perpendicular to the rafters, with a notch in the timber for installation of its base. In order to ensure that during shrinkage wooden structures to ensure maximum travel of the slide; when installing it, it is installed in the most extreme position.

The degree of shrinkage of a wooden house (and therefore the amount of movement acting on the rafters) depends on the material used in the construction of the walls. Timber with natural moisture shrinks more, dry profiled timber shrinks less, and laminated veneer lumber gives minimal shrinkage, etc.

The walls of a house made of dry timber can shrink by 6% of their total height. If we are talking about the walls of a house made of timber with natural moisture, then the shrinkage can be even greater. Our article explains in detail what are the pros and cons .

Construction of a roof on a log house

In addition to timber, wooden houses are built from so-called logs manual cutting. Practice shows that the rafter system of such a house has its own characteristics.

Dmitry Filippov, company specialist "Traditional carpentry technologies":

- IN log houses Based on the log house, a male-slat roofing system is used plus a “sliding” one rafter part.

Roofing in a house made of logs, installation.

Roof for log house has its own design features. Sledges - horizontal logs cut into a log gable (the top of them is the ridge) - are seated together with the log house. Afterwards, a board lining (aka ceiling) is laid on the logs (lay down). Next, the rafters are mounted (in gable roofs they are attached to each other on the ridge using sliding fasteners). Then a roofing pie is formed - vapor barrier, insulation, waterproofing, counter batten, sheathing, roofing material is laid on top.

Dmitry Filippov:

– Thus, the rafter part with the roofing pie is not tied to the log house, but, as it were, “lies” on it, which allows the roof to retain its shape and integrity when the log house shrinks.

From our article you will learn about the types of structure and roof shapes of log houses.

Materials going to the rafters

In addition to taking into account the characteristics of wooden and stone houses, when designing a rafter system, it is necessary to understand the requirements for lumber.

Vera Vavilova:

- Pine and spruce will do. These are inexpensive wood types that meet the basic strength characteristics of rafters.

It is important to ensure that the lumber meets grade 0-2 according to GOST 8486. The rafter elements should not contain large falling knots, rot, wane and cracks. These vices weaken bearing capacity rafter system.

Pavel Orlov:

– Edged coniferous wood with a moisture content of up to 20% is used for the rafter system. All lumber used must be treated with certified fire-retardant impregnations.

If you place freshly sawn, raw wood on the rafters, then during the drying process the already installed rafters will move. This will cause deformation of the roof and roof covering.

To avoid this, it is better to make rafters from chamber-dried calibrated lumber.

Another option for materials used to make rafters can be trusses and glued beams.

The use of these materials is determined by the project, based on the size of the spans and the expected load on the structure.

Vera Vavilova:

In this case, the elements of the rafter system are manufactured at the factory and delivered to the site in the form of parts ready for assembly.

This eliminates the so-called “human factor”. It also saves time, because such a structure is assembled faster than one made on site with inevitable sawing and fitting of parts on site.

Factory rafter systems are manufactured strictly according to the design and technical specifications. Thanks to this, a high quality of the base of the future roof is achieved, because the wood has already been treated with antiseptic agents, and the entire rafter system is assembled according to the principle of a designer.

Another material used in the construction of rafter systems for a stone or wooden house can be light steel thin-walled structures (LSTS). Such rafters do not need to be treated with antiseptic agents; they are light in weight, have a long service life and are highly fire resistant. Let's consider the main features of the rafter system built using this technology.

Deputy Commercial Director of the company "Polymetal-M" Andrey Usachev:

– The roof truss system, made using LSTK technology, includes galvanized rack and guide profiles. If necessary, devices warm roof a thermal profile is used (a profile with perforations along the entire length), which will remove the cold bridge and avoid heat loss.

The thickness and cross-section of the profile used in the design depends on the load expected on the rafter system.

Each element of the system has strictly specified dimensions according to the project.

This significantly reduces assembly time and also avoids waste on the construction site.

Each profile is marked in accordance with the drawings and assembly instructions.

Andrey Usachev:

– Markings make assembly easier. Each profile is marked with a punch (extrusion). Because the metal frame is fastened together with self-tapping screws, then thanks to the extrusion it is clear where the connection should be. The dowel increases the rigidity of the assembled assembly, reducing the shear force on the self-tapping screw.

In the FORUMHOUSE topic you can find out what begins. Also here you will find all the information about. Read on to learn how to build it yourself.

Watch our video about roofing in Russian wooden architecture.

In order for a constructed building to last for more than one year, it needs both a reliable foundation and strong system roofs that can withstand the vicissitudes of the weather. The roof must withstand heavy loads with dignity: heavy snowfalls, sharp gusts of wind, heavy downpours. The roof truss system is best suited for this.

Roof trusses and its types

The rafter system is the basis of the roof, which focuses on the load-bearing elements of the structure and also serves as a frame for various types of roofing materials: insulation, waterproofing, various coatings.

The dimensions and design of the rafters depend on:

• purchased material;
• size of the building;
• house dimensions;
• building materials for rafters;
• individual customer preferences;
• roof loads relevant for a particular region.

The rafter system has:

• sheathing - beams laid perpendicularly on the rafter legs;
• ties that absorb tensile forces;
• wooden racks located in a vertical position;
• mauerlat - a beam, the installation of which is carried out along the wall, the rafters rest on it;
• rafter legs are a kind of wooden beams that bear the main load of the roof.

Each of the above factors is very important, since it is necessary to understand what type of rafter system will be optimally suited for a particular situation.

When it comes to low-rise buildings, wood structures are the most common. In many cases, three types of rafter trusses are used: hanging rafters, layered rafters and a mixed rafter system.

Characteristics of hanging rafters

Hanging rafters are the most elementary type of rafter systems, their characteristics:

If the roof of the house has a complex structure, the types of rafters can be alternated. For example, if there are supports or a middle main wall, layered rafters are installed, and if there are no such elements, hanging rafters are installed.

Features of layered rafters

For a layered rafter system, the house must be additionally equipped with a load-bearing wall located in the middle. Layered rafters are distinguished according to the following characteristics:

The design of the combined system is the most complex, since it includes parts of two other types of rafters - hanging and layered. It is used for mansard roof. The walls of the rooms, which are located on the second floor, are formed by vertical supports; these supports are also intermediate racks for rafter beams.

The part of the rafters that connect one end of the racks functions as a crossbar for the slopes located on the side, and for the upper part of the structure they are a tie.

At the same time, the horizontal beams perform the following functions: for the upper slopes - the Mauerlat, for the side slopes - the ridge beam. To increase the strength of the roof, struts are installed that connect the side slopes and vertical posts.

Combined system the sling is the most complex and time-consuming to manufacture, but these shortcomings are fully compensated by the increase in the load-bearing qualities of the roof in the absence of unnecessary supports, especially when there is a need to cover significant spans in the building.

Roof trusses for various roof types

When constructing a certain building, rafter systems of one type or another are necessarily used, and the type of roof will completely depend on the design of the future structure.

Rafter truss for gable roof

Gable roofing is a common roof construction for residential buildings that have no more than three floors. Preference is given to this particular design due to the technical characteristics of the inclined shape of the rafter system, and also due to the fact that installation work carried out easily and simply.

The rafter system of a gable roof includes two rectangular inclined planes. The upper part of the building from the end side resembles a triangle. Main components gable roof- this is the mauerlat and rafter legs. In order to properly distribute the load across the rafters and walls, struts, crossbars and racks are installed, thanks to which you can create a durable, rigid, elementary and lightweight structure for installing a structure for a gable roof.

On top of the rafters you can install sparse or solid sheathing, and then attach it to it bitumen coating, shingles or some other type of material. The rafters and the sheathing itself are usually made of beams or boards, which are fastened with nails, bolts or metal fasteners. Metal profiles can be used as rafters, thereby covering significant spans. There is no need to use extra racks and struts.

The installation of a rafter system for a gable roof allows you to evenly distribute the entire existing load along the perimeter of the building. The lower ends of the system place emphasis on the Mauerlat. They are fixed with fasteners or metal brackets. By the angle of inclination of the rafter bars, you can determine at what angle the roof slopes will be inclined.

Rafter system for hip roof

When arranging a system for a hip roof, installation will be required different types rafters:

• narozhniki (short);
• lateral;
• hip main;
• obliques (diagonal elements that form a slope in the shape of a triangle).

The rafter legs, located on the side, are made of boards, and they are mounted identically to the parts of a traditional pitched roof with a pitched or hanging structure. Hip main rafters are layered parts. For sprigs, boards or bars are used, attached not only to the Mauerlat, but also to the diagonal beams.

To install this type of structure, the angle of inclination, as well as the cross-section of the slanting beams, are accurately calculated. The dimensions of the parts also depend on the span length.

Maintain symmetry when installing diagonal beams for rafters, otherwise the roof will deform under significant load.

Rafter system for a sloping roof

A broken roof is a structure with rafters that consist of several individual elements. However, they should be located under different angles relative to the horizon. And since the lower rafter part is almost vertical, the attic space of the building receives additional area, thanks to which it can be used as residential. The installation of this type of roof is carried out during the construction of four- or gable construction rafters

Calculate four-slope system rafters are needed by professionals, but you can make a gable sloping roof yourself, since its installation is very simple. To do this, it is necessary to install a support frame, which should consist of purlins and racks. Horizontal parts are fixed with hanging rafters. But the supports of the sloping roof are secured to the mauerlat with the shortened legs of the rafters.

"Cuckoo" in a roof truss

The so-called cuckoo on the roof is a small protrusion that is located on the attic floor. Here is a window for better lighting attic room. The installation of the “cuckoo” is carried out carefully, while monitoring the parameters of the entire structure: depth of cut, angle of inclination and other factors. However, before this they produce necessary measurements.

The first stage of work begins with the installation of the Mauerlat (beam with a cross-section of 10x10 cm, which is needed to support the slings). The rafter system acts as a skeleton for the roofing material. To impart rigidity to the structure, spacers are used, which are mounted between the two legs of the rafters.

After the installation of the roof truss is completed, sheathing is laid, the type of which depends on the roof covering purchased. Installation of the sheathing is done continuously or with a certain step. Boards, OSB and plywood sheets are usually used for it. In addition, the installation of roofing material must be identical throughout the entire roof.

The main difficulty when installing such a rafter system is the location of the internal corners. Snow can accumulate in these places, which means the load will increase, which is why a continuous sheathing is made.

Chalet roof rafter truss

The peculiarity of this design is that the canopies and overhangs are moved outside the house. In addition, there must be rafters and roof beams extending up to three meters on the sides of the building. Each of these elements is secured with a bracket to the wall of the building in the lower part. Next, tie the edges of the beams. They serve as a support for covering the roof of the building.

But when creating large overhangs, it is necessary to install the reinforced belt in parallel with the installation of studs for the Mauerlat. It is necessary to make anchors that help secure the consoles. In this case, the rafters will be perfectly fixed with anchors and, in addition, with mortises.

To carry out the side cornices, a ridge beam is made, after which beams are placed at the level of the mauerlat, which must be identical to the length of the ridge. The truss, and subsequently the building materials for the roof, rest on these structural details.

When designing a building, the angle of the chalet roof is calculated based on the characteristics of the local climate and other factors. With a slope angle of about 45°, the load from snow is not taken into account, since with this option it will not linger on the roof. At the same time, the flat roof will withstand the load from snow, but it is necessary to install a reinforced roof truss. Before installing the chalet roof, a building design is prepared, because the originality of the roof itself, as well as the long eaves and overhangs, oblige this.

Rafter truss designed for soft roofing

Soft roofing is made in various ways, but there are technological methods its buildings General characteristics. Initially, you need to prepare. When arranging a roof for a house made of foam concrete or other material, a mauerlat is first installed, then in the upper crowns of the building a cut is made for the ceiling beams in increments of up to one meter. The distance between the boards is calculated based on the type of rafter structure.

1. Install individual parts of the rafter system. To completely eliminate the risk, the rafter boards are attached to the ground with screws. After the roof truss is created, it is raised to the top of the building.
2. All elements of the rafters are secured to the ceiling, internal boards, jibs, and crossbars. Further, this base for the roof will become a single whole structure.
3. The next stage is the sheathing, which is under soft roof installed with small or no gaps. Gaps of no more than 1 cm are allowed. Quite often, leveling plywood is installed on top of the boards. Its sheets are laid using the bricklaying method. The resulting joints are not aligned with the gaps between the plywood and the board.

If the length of the sheathing boards is not enough, then the joints of the parts must be located in different places. In this way, you can correctly distribute areas that have been weakened.

Self-production of the rafter system

Before the installation of the rafter system begins, the mauerlat must be secured to the longitudinal walls with anchors. Next you need to decide on the required leg section for the rafters, depending on the distance and their length. If there is a need to increase the length of the rafters, then connect them with various fasteners.

When using different insulation, you need to choose the ideal distance between rafter elements in order to reduce the number of thermal insulation scraps.

Installation of the rafter system must be done in the following order:

1. A template is made according to which the truss is assembled. Take 2 boards corresponding to the length of the rafters and connect them together at just one edge with a nail.

   
   A template for rafters called “scissors” will help you quickly assemble the entire roof rafter system

2. The result is a design called “scissors”. Its free edges are placed on supports at the points of contact between the rafter legs. The result should be the final angle, that is, the angle at which the roof slope will be inclined. It is fixed with several long nails and transverse boards.
3. A second template is made, thanks to which the cuts are installed on the rafters. It is made from plywood.
4. Special mounting cuts are cut on the rafters (a prepared template is used for these purposes) and connected at an angle of inclination of the slope. You should end up with a triangle going up the stairs to the roof. Next, it must be attached to the Mauerlat.
5. Initially, two side gable rafters are installed. Their correct installation in vertical and horizontal plane occurs due to temporary struts attached to the rafters.

   
   For correct installation of the entire rafter system, the first pair of rafters is installed on the roof

6. A cord is stretched between these tops of the rafters. It will indicate the future ridge and the level of other rafters located in the gap.
7. Raise and install the remaining rafters at the initially calculated distance, which should be at least 60 cm from each other.
8. If a bulky rafter structure is envisaged, then it is additionally strengthened with struts, supports, and so on.

   
   The bulky structure of the rafters is additionally strengthened with struts and supports

9. A ridge beam is installed on special supports, to which not only short, but also diagonal and intermediate elements of the rafters are attached.

   
   Proper fastening of the ridge beam ensures the reliability of the entire rafter system

Typical components of a standard rafter system

The strength of the rafter structure depends on the ideally selected section of the boards, as well as on high quality rafter nodes. The connection of parts for the roof structure is done according to established rules.

The main typical units in the rafter system:

• rafter support assembly on the mauerlat;
• ridge;
• unit for combining the top ties and the entire rafter system;
• securing the strut, rack, as well as rafters and beams.

After the design of the rafter system has been chosen, it is necessary to draw up a plan in which to highlight all the nodes. In each design they are made differently, since it depends on various nuances: the type of roof, its size, angle of inclination.

Rafters made from a profile pipe are a metal structure that is assembled using lattice rods. The production of such farms itself is a very labor-intensive process, but also more economical. For the manufacture of rafters, paired material is used, and gussets are connecting elements. The structure of the rafters from profile pipes is assembled on the ground, using riveting or welding.

Thanks to such systems, any spans are blocked, but the correct calculation must be made. Provided that all welding work is done efficiently, in the future all that remains is to transfer the structural elements to the top of the building and assemble them. Load-bearing rafters made from profile pipes have many advantages, such as:

Crossbar in the rafter system

Crossbar is a fairly broad concept, but in the case of roofs it has a certain meaning. The crossbar is a horizontal beam that connects the rafters. This element prevents the roof from “expanding.” It is made of wood, reinforced concrete, and also metal - it all depends on the type of structure. And the crossbar serves to distribute the load exerted by the rafter system.

It can be fixed in various places between the legs of the slings. There is a direct pattern here - if the crossbar is fixed higher, then the timber for its installation must be selected with a large cross-section.

There are many ways to fix the crossbar to the rafter system:

• bolts;
• nuts;
• studs with washers;
• special fasteners;
• nails;
• mixed fastenings when used in parallel different types fasteners

The fastening is available with a mortise or overhead. In general, the crossbar is a design unit, as is the entire system of roof slings.

Fastening the rafter system

To ensure the reliability of the rafter system, you must first find out how they are attached to the supporting roof and ridge. If a fastening is made to prevent deformation of the roof when the house shrinks, then the rafters are secured on top with a hinge plate or a nut and bolt, and below with a sliding support.

Hanging rafters need a tighter and more reliable fastening in the ridge, so in this case can be applied:

• overhead metal or wooden plates;
• cutting method;
• connection using long nails.

In the layered system, the rafter legs are not connected to each other, since they are attached to the ridge girder.

The rafters are attached to the mauerlat using the cutting method, which is made in the rafter leg. Thanks to this fastening method, the roof support will not weaken. Cutting is also done when installing rafters on floor beams. In this case, a cut is also made in the support beam.

Video: how to make rafters with your own hands

Thus, an ideally selected rafter system and its design characteristics will help create the basis for reliable roof for your home.