Installation of rafters is one of the key stages of roof construction. To ensure that the rafter system does not deform or collapse under high loads during operation, the rafters must be properly secured.

Calculation of rafter pitch

When designing rafter system This issue is given special attention. The strength characteristics depend on the cross-section of the rafters and the pitch of their installation. roofing system.

The rafter pitch is the distance between adjacent rafter legs. The minimum pitch of the rafters is 60 cm, the maximum is more than 1 meter. A simplified version of calculating rafter pitch involves using the table:

The length of the eaves slope must be divided by the rafter pitch selected in the table, then add one to the resulting value and round up to a whole number. The resulting result indicates the required amount rafter legs on one slope. Then the length of the slope along the eaves should be divided by the calculated number of rafter legs - the final number corresponds to the value of the center distance between the rafters.

This calculation method is general, it does not take into account the specifics of roofing coverings and the type of insulation used. If you intend to lay a roll or slab insulator, it is recommended to adjust the pitch of the rafters to the size of the material. It should be taken into account that the width of the cotton insulation should be 1-1.5 cm greater than the span between the rafters.

When determining at what distance to install the rafters, you should also pay attention to the recommendations for installing the selected roofing covering.

Preparation of material

Installing rafters with your own hands requires not only knowledge of the process technology, but also proper preparation wooden elements of the system for installation. The rafters are made from edged boards or timber; the cross-section of the lumber is selected at the roof design stage. The tree should not have cracks, wormholes or other damage.

Rafter legs should be made of well-dried coniferous wood to prevent their deformation.

Wooden elements must be treated with fire retardant and bioprotective compounds. Before you begin installation, you need to decide on the method of attaching the rafters to the mauerlat or beams, and the type of ridge connection. In accordance with the project, metal and wooden fasteners are selected, including:

• plates (made of metal or wood);
• bolts or studs with nuts and wide washers;
• nails, screws, staples, etc.;
• wire rod.

Types of rafters and features of their installation

When constructing the roof of a house, hanging or layered rafters are used. In some cases, a combination of both may be used. Hanging ones rest only on the walls of the building, and layered ones require the installation of additional supporting structures, so this option is primarily used if there is a medium load-bearing wall or support pillars inside the building box.

The lower part of the layered rafters rests against the mauerlat; accordingly, the walls of the structure must have sufficient width for the installation of a special supporting structure made of timber with a cross-section of 150×150 mm. The upper part of the layered rafters rests on the ridge girder. Thus, installation requires the installation of a purlin, for which racks should be mounted on the middle wall or pillars.

Hanging rafters rest only on the walls. This design can be mounted both on the Mauerlat and on thin walls without laying the Mauerlat. In this case, the support for the lower part of the legs is provided by floor beams protruding beyond the plane of the wall on both sides of the building. Hanging rafters are connected by a jumper (tightening, crossbar) which relieves the pushing forces. When covering large purlins, the trusses are reinforced with additional elements to enhance the rigidity of the structure. When installing hanging rafters on a mauerlat, a low-lying tie can serve as a floor beam.

Before installing the rafters, it is necessary to mount the scaffolding. This makes it possible to ensure the necessary safety and convenience of work.

Installation of the upper ends of the rafters

When choosing how to install rafters, it is important to evaluate the complexity of the work and the weight of the rafter structures. If the assembled truss has a relatively light weight, or it is possible to use lifting equipment, then it is easier to assemble the structures on the ground, and then lift and install them on the roof. If the elements of the system are heavy and have to be lifted manually, then the trusses are assembled on the roof. The technology for installing roof trusses is described in the video instructions.

The connection of the upper ends of the rafters can be done different ways. First of all, this is a butt mount. On the opposing rafter legs, cuts are made at the desired angle. Then the rafters are joined with the resulting ends and attached to two nails. The connection is further reinforced with a wooden or metal overlay.

Attaching the rafter legs with an overlap is done using bolts or studs with wide washers and nuts. In this case, the rafters are in contact with the planes.

If the rafter system is mounted on wooden house with gables made of timber or logs, it is necessary to install rafters on the walls using sliding fasteners to avoid deformation of the roof during shrinkage of the structure. Accordingly, in the ridge part, the rafters must be connected in a special way: the rafter legs must be positioned with a gap, and they are fastened together using a special movable metal connecting element.

If there is a ridge beam, installation of rafter trusses on the ground is not required - the rafter legs are installed one at a time and attached to the ridge girder.

The ridge run must be positioned strictly horizontally so that the rafter system evenly distributes the load experienced by the roof.

Methods for installing rafters on walls

The lower ends of the rafters are attached to beams or mauerlats. The hanging rafter trusses, assembled according to a template, rise to the roof. The outer trusses are installed first. It is necessary to make two or three holes in the tightening to attach the rafters to the beams laid on the upper crown of the frame.

If hanging rafters are mounted on a stone building, it is necessary to use special fasteners - the so-called “ruff”, made of durable steel. This fastener is driven into every fourth row brickwork. Using the loops extending from the ruff, you can secure the beams. It is recommended to use a strong beam as a mauerlat - in this case the load will be evenly transferred to the walls.

On buildings made of brick or other material that is not prone to shrinkage, the rafters should be firmly secured. To do this, a cutout is made in the rafter leg, the lower part of which should lie firmly on the Mauerlat. The rafter is fixed with three nails (two are driven in on both sides at an angle, and the third vertically from above) and tied with wire. A connection using corners and a support bar can also be used to prevent the rafters from shifting.

Proper installation of rafters involves making a fire break in the place where the chimney passes through the roof. If its arrangement involves the installation of a special rafter system, this should be taken into account when installing a shortened rafter leg (from the Mauerlat to the chimney structure). The distance between the structural elements and the pipe must be at least 130 mm.

+9

The roof gives any building architectural completeness, fulfilling its main function - protection from bad weather. Depending on the climatic conditions in which the house is being built, the roof structure is chosen. So, in places where precipitation occurs regularly, it is best to build houses with a high roof. In places where there are constant strong winds, it is better to install roofs with a gentle slope. In our article we will talk about how to install rafters on different types of roofs.

The design can be: single-pitch, gable, hipped, spire-shaped, .

However, regardless of the design of roofs and roofing materials, roofing roofs have the same elements: pediment, ribs, ridge, dormer window, and pediment, hip and valley.

A design feature of a roof with one slope is that its basis for the slope is load-bearing walls, and their heights are different. This design is practically not used for residential buildings.

It has found its application for outbuildings, country houses, bath During construction country house often erected.

Its design feature is that the roof rests on load-bearing walls of the same height.

Thus, a space called a pediment is formed inside the slopes. It is not difficult to build a roof with such a design yourself, without the involvement of specialists.

Mansard and hip roofs are more difficult to construct. The design of hip roofs is even more complex (they have four slopes).

Multi-gable roofs are usually used on houses with more complex layouts. Their arrangement will require the construction of a valley, which will further complicate the roofing work.

General roof structure

None of the above types of roofs can do without such an element as rafters. They are also called farms. This wooden beams, which are the load-bearing elements of the roof structure.

Between the rafter belts (lower and upper) there are battens, their basis is bevels and struts.

The components of the roof are also:

• roof;
• roofing base;
• layer of thermal and waterproofing.

The further arrangement of all load-bearing elements of the roof: the mauerlat and sheathing depends on how to install the rafters. Such parts are made only from wood (beams, boards, logs).

Depending on the material, the method of connecting all load-bearing elements is also selected. The following fasteners are used:

• spacers;
• racks;
• struts;
• crossbars.

The main purpose of fasteners is to provide rigidity to the entire system.

It is important to know: the larger the span, the more fasteners will be required.

Rafter truss - roof parts connected to each other using fasteners. Its basis is one or more triangles.

Mauerlat is laid along the outer edge of the walls - wooden beam. Its main purpose: support for load-bearing rafters.

Types of rafters

The reliability of the roof's supporting structure depends on how to install the rafters correctly.

Important to know: you need to use wood for rafters High Quality, without cracks, knots and wormholes.

There are two types of rafters:

1. Hanging rafters.
2. The rafters are layered.

Advice: it is better to install layered rafters in a house where there are supporting middle walls. If the span is more than 5 meters, then we place the rafters on the slopes. The layered rafters rest against the mauerlat, so the load on the walls increases several times. Therefore, the walls must be quite massive.

How to install layered rafters correctly? In this type of rafters, each rafter leg is equipped with two supports.

One support rests on the mauerlat, and the second is a purlin that runs along the ridge. On racks that are installed on interior wall, the purlin is laid.

Hanging rafters require more careful preparation and practical skills. They need to be installed in houses with thin walls.

Since they rest only on the walls of the house and do not have intermediate support.

Very often, before placing the rafters on the house, the rafter legs are connected with a special tie. It can also be used as a floor beam.

Hanging rafters with a simple design are a pair of rafters, they need to be connected at the top into a ridge. To do this, you need to cut the rafters halfway through the tree, and at the bottom they will rest against a beam located horizontally.

A little advice: in order to prevent the rafters from sagging, fasten them with staples; to do this, first cut in the crossbar. In cases where the width of the spans is 7 meters or more, we recommend using a beam; it must be secured in a tie and in the ridge. Fasten the beam to the rafters, braces and transom using a notch (it should resemble a straight tooth). This design of the rafter system is suitable for spans with a pitch of no more than 10 meters.

When installing hanging rafters with a simple design on a masonry structure, it is important to know how to align the rafters. Here you will need special fasteners - a metal brush.

Such fasteners must be driven into the brickwork, into every fourth row. Two loops extend from the ruff, with the help of which the beams can be attached.

Consider one more at least important feature: strong timber must be placed along the entire length of the building. The ends of the rafters will rest on it, thus distributing the load on the walls.

We invite you to view practical guide: video on how to install rafters.

Let's consider no less important points during the construction of the rafter system. So, in the place where the chimney exits, do not forget to make a fire break.

It is important to know here that the distance between structural elements should not exceed 130 mm.

In order to correctly install the roof overhang, we recommend that you watch our video tutorial again: how to install rafters video. You will realize that special fillies will be required. You can make them yourself from a board with a section of 5x10 cm.

The length of the board should be half a meter longer than the overhang, since when connecting to the rafter leg, a joint will need to be made. Nail the fillets to the board so that the rafter leg does not extend beyond the roof.

Rafter structure of mansard roofs

The attic structure is more complex, but it is also possible to do it yourself. It is advisable to choose a simpler version of this type of roof with triangular, clear, straight slopes.

The further equipment of the attic room depends on how to correctly align the rafters, since the lower part will act as the floor roof truss.

We recommend that the attic-type structure be built from parallel beams, which should have a cross-section large enough to withstand subsequent operational loads. Other structural parts can be made from thinner lumber or even planks.

Rafter structure of hip roofs

A design feature of hip roofs is additional slopes. They need to be formed with hip rafters, which should form a joint with the ridge of the gable roof.

From the outside it should look like two separate parts. The first part is a gable roof; its length is not enough to cover the area of ​​the entire house. It turns out open areas- they need to be covered with two hips.

It is very important to know at what distance to place the rafters, since the main load will be on the outer rafter beams, they must be further strengthened.

But we must not forget about the clear ratio of the sizes of the gable and hip parts of the roof. If we slightly violate the proportions, we will ruin the appearance of the entire house forever.

In fact, this is a complex single structure, the installation of which is best left to professionals.

For a good roof, it is very important that every step in its creation goes perfectly. The basis of the entire roof structure is the rafter system, the configuration of which determines the type of upper part of the building. Exist different types such systems, among which you need to choose the most suitable one for yourself, because the functionality and quality of the entire roof depends on the correctness of your choice.

Types of rafter system

The construction of the roof during the construction of a building is of significant importance. And in order for the roof to be strong enough, special attention is paid to load-bearing systems, which are divided into:

• combined;
• hanging;
• layered.

The roof is a rather complex structure consisting of various parts. The main requirement for a roof is - This is the ability to protect a structure from all kinds of weather conditions and withstand different loads.

The main loads of the roof fall on the rafter system, so it is very important to choose necessary materials, calculate everything correctly and install it in accordance with the technology.

Installation of hanging rafters

Hanging rafters are intended for buildings in which there are no permanent partitions inside, and the distance between the common load-bearing and side walls is no more than 10 meters. The roof structure in this option rests on the main walls of the building, but because of this it is subject to high loads. To make the tension a little weaker, additional parts (tightenings or crossbars) are used that fasten the truss in a horizontal position.

Depending on the span length, various reinforcing elements are used in the construction of hanging rafters

The lower ties are connected at the base of the rafters and can be used as beams for the attic floor, but they must be laid on the mauerlat. To make hanging rafters, a board with a cross-section of 50x200 mm is usually taken, but each individual building needs its own specific calculations.

Sequence of actions for installing hanging rafters:

Installation of layered rafters

Layered rafters are mainly installed in those buildings where there are load-bearing partitions. They are much easier to install than a hanging system, since strong load-bearing walls located inside the house provide reliable support for the rafters. In addition, this system requires a minimum amount of building materials.

The ridge board in this case serves as a reference point. This roofing system is installed in one of three options:

To secure the rafters at the bottom of the roof, it is necessary to use sliding fasteners, which relieve the load-bearing partitions from additional stress. In this case, the rafters are not fixed very tightly, so that when the building shrinks, they can move without overloading the roof structure.

But in some cases, you can use a spacer system that is tightly attached to the Mauerlat below. Struts and ties are installed in the structure to reduce the load on the walls. This method is called complex because it combines elements of two systems.

This roofing system is used mainly for the construction of private buildings, so it is worth mentioning installation work, which are produced in the following sequence:

Installation work to install the layered system should begin with laying the boards on the floor beams. This device will help you carry out work comfortably and safely.

Combined roofing system

Combined rafters have in their design elements made of layered and hanging systems. They are used in the manufacture mansard roof. The walls of the rooms on the second floor are made up of vertical posts, which act as a fulcrum for the rafter beams.

The horizontal beams that were installed on top of the racks perform two functions: for the upper slopes they are a mauerlat, and for the side slopes they are a ridge beam. Some part of the rafter system, which is connected at the top of the ends of the racks, simultaneously becomes a tightening for the upper elements and a crossbar for the slopes located on the sides.

The combined roof uses fragments of layered and hanging rafter systems

To increase the strength of the structure, it is necessary to install struts that secure the rafters and vertical racks roofs. Making combined rafters is a little more difficult than other systems, but the labor intensity of the work is offset by an increase in the load-bearing characteristics of the roof and the presence of a full-fledged room under the roof.

Photo gallery: options for rafter systems

In design hip roof layered rafters are used. For the envelope roof, a rafter system similar to the attic is erected. In structures broken roofs at the joints there are special rafters that support the valleys. Multi-gable roofs consist of several different rafter systems combined into one. In the rafter system of an attic roof, the same element can be both a mauerlat and a ridge

Installation of roof truss system

The rafter system is made of coniferous wood. You can use boards or timber that are treated with antiseptic substances before installation. Fasteners can be as follows:

• wooden scarves;
• metal plates;
• various cuts;
• nails.

When starting to install the rafters, the level of the floors and load-bearing walls is raised, after which waterproofing is laid. The rafter structure is necessary to prevent deformation of the rafters. The supporting elements that give the rafter system stability can be:

• sunbeds;
• struts;
• runs;
• racks.

Insulation of the roof is necessary, but for this you should choose a material for hydro-, heat- and vapor barrier. Installation is carried out layer by layer and only in the sequence in which it is necessary: ​​initially steam-, then heat- and finally moisture-proofing material.

Before laying the roof covering, the necessary protective materials are installed in compliance with the established ventilation gaps

To ensure long-term operation of the rafter system, the necessary air circulation is arranged by installing ventilation holes. To prevent leaks, “collars” are made near the holes to prevent water from penetrating under the roof.

Video: DIY rafter system installation

How is the Mauerlat attached?

The Mauerlat is the foundation of the roof, so you should treat it responsibly. Otherwise, roof repairs will be inevitable in the future. Sequence of work:

Methods of fastening roofing Mauerlat and splicing rafters

The Mauerlat is attached to the walls of the building along the entire perimeter, and the fastenings must be located in close proximity to the inside of the wall. Outside the house, the wooden part is protected by a slight projection of the wall. The mounting location is also initially determined.

How to fix the Mauerlat to the wall

The Mauerlat can be attached to the wall in the following ways:

How to attach rafters to the Mauerlat

All options for attaching the roof rafter system to the Mauerlat can be divided into the following types:

How the rafters are attached at the ridge level

The most common option for attaching rafters to the ridge is a butt connection:

Rafter splicing options

In the construction industry, various options for rafter splicing are used everywhere, and when choosing a specific technology, you need to pay attention to the design characteristics of the rafter system, which are influenced by:

• purchased materials;
• technical data of the construction site;
• rafter installation step.

Rafters can be spliced ​​as follows:

Each type of rafter system has its own characteristics and is only suitable for a certain type of roof structure. Exactly from correct installation rafters depend not only on the reliability, but also on the strength of the roof, so this stage of work must be approached with maximum responsibility.

Designing a country house includes not only calculating the type and strength of the foundation, the area, height and number of floors of the building, but also the roof structure. When developing a project, all factors are taken into account, and best option rafter systems that can decorate a building and protect it from cold and precipitation.

If you decide to start building a house yourself, you need to know what the rafter system consists of and how to install the rafters on the roof in order to get the desired result. In our article we will talk about the rafter system, the rules for its installation and the types of rafters.

Whatever roof shape you choose for your home, the roof structure will always be based on a rafter system. To cover the roof with roofing material, sheathing and a layer of waterproofing are laid on the rafter system.

For the manufacture of the structure, coniferous wood is used with special treatment with protective agents and a humidity of no more than 2%.

Note! Grade 1 wood is needed for tie-downs and hanging rafters. Material of grades 1 and 2 is purchased for rafter legs. Grade 3 wood can only be used for making racks and struts.

The durability and strength of the rafter system depends on the quality of the material, the reliability of the connections and the correct design of the structure. Special attention pay attention to the rafters. Let's look at what the rafter consists of to make it easier to assemble and install the entire system on the roof.

The rafter consists of elements:

• rafter legs;
• struts resting on the upper part of the wall of the building (they are also called struts);
• racks supporting the rafter legs and located vertically;
• support beams (crossbars) that act as the basis for all load-bearing elements of the roof and are laid parallel to the base of the building between the rafters;
• in hanging type rafters there are racks that work in vertical tension and are called headstocks;
• Ties are installed to resist thrust forces.

These are the main elements of the rafters, but for complex structures rafter systems use additional parts. To install rafters on the roof with your own hands, you need to prepare the following materials and tools:

• waterproofing material;
• rafters;
• boards;
• fasteners;
• hammer and axe;
• nail puller, tape measure;
• electric drill with a set of drills;
• chainsaw;
• level and pencil.

When everything is prepared, it’s time to start installing the roof, and therefore installing the rafters on the house.

Installation

Stage No. 1. Make a template of the designed roof truss from the boards. Lift two boards onto the ceiling and connect their edges at one end with nails. Place the boards to the side and place the free edges on the laid support beam. To fix the angle formed between the boards, nail a transverse jumper.

Lower the template from the boards onto the support beam and use a pencil to mark the angle of the rafter trim for a strong attachment. This method makes it quicker and easier to choose correct angle cutting and installing rafters.

Note! At this stage of work you cannot rush. The better the template is made, the more reliable and durable the entire structure will be.

Stage No. 2. Lower the template to the ground and begin making rafters. The template must be well fastened so that the angle of connection of the rafter legs is not disturbed. When the first rafter (truss) is ready, it is lifted onto the building and placed on the base.

Stage No. 3. Mark the cut location on the rafters and mauerlat. Use a chainsaw to make a cut for correct installation. Proceed with the assembly of the next roof truss.

Stage No. 4. Install the first two ready-made trusses of the rafter system on the mauerlat along the edges of the house. To determine the required level, pull the cord between them.

Note! The rafters installed along the edge of the mauerlat are secured with supports on both sides. The installation of trusses must be strictly perpendicular to the base of the floor.

Stage No. 5. The level has been set, all fastenings have been carefully checked and it’s time to start assembling the remaining rafters. The number of trusses is determined based on the total length of the system and the step between the trusses of no more than 0.8 m. It is easier to assemble the structure on beams.

Note! To avoid the rafters moving, it is best to hammer two boards between them.

Stage No. 6. The time has come to start installing and fastening the supports and cross bars. In addition, it is advisable to resolve issues with waterproofing, vapor barrier and thermal insulation of the entire roofing system. For installation roofing material the sheathing is installed. The frequency of fastening the sheathing elements depends on the selected roofing material.

The type of roof depends on the chosen angle of the roof slope. For flat roof the slope angle does not exceed 10%, and for a pitched structure the slope angle is always greater than 10%. Pitched roofs come in different designs:

1. Roofs supported on two sides at different levels are called lean-to roofs.
2. Supported on sides of the same level, structures are called gable.
3. Hip roofs are distinguished by triangular-shaped slopes. When the slope does not reach the eaves, the roof is called half-hip.
4. The tops of four triangular slopes converging at one point form a hip roof.
5. The attic rafter system, also called a broken gable system, is distinguished by the fact that it consists of rectangular slopes connected at an obtuse angle.

To assemble rafter systems, hanging and layered rafters are used. It's time to talk about systems consisting of hanging or layered rafters.

Hanging

To decide how to install rafters, you need to know what type will be used to create the rafter system. The choice of fastening methods and type of rafters is influenced by many factors - the type used roof covering, the angle of inclination of the roof slopes, the expected loads from gusts of wind and fallen snow.

Hanging rafters are distinguished by the fact that they rest only on the mauerlat and during their installation no intermediate supports are used. This rafter system creates strong pushing forces horizontal type, acting on the walls of the building. To reduce these forces, puffs are installed, which simultaneously act as fasteners for the rafter legs.

The puffs can be placed near the Mauerlat or higher. With a high installation, a stronger connection between the rafters and tie rods is necessary.

Note! Installation of hanging rafters is possible only when the roof span is no more than 12 meters.

Layered

If during the construction of the house it was planned to build an internal load-bearing wall, the roof of the house is made of layered rafters. Installation of layered rafters is no different from installation of a frame system.

Fastening the rafters can be done in different ways and depends on the material used to construct the walls of the building. On a wooden log house, a connection is made between the rafters and the upper crown. For a frame building, fastening with top harness. For a building made of stone, the rafters are attached to the support beam.

To prevent rafters of small cross-section from sagging, racks, crossbars and struts are installed according to a lattice pattern. For the manufacture of rafter leg tie-downs, only wood is used good quality. For large spans, from 2 to three logs 650 cm long are used to make screeds. They are aligned in one plane and fastened together along the length.

To make racks and struts, use scraps of logs with pre-shaved ends and template markings from metal sheets. Having made preliminary markings, the places where the rafters are cut into the mauerlat are cut out.

When constructing the upper part of the truss and walls, composite type beams with plate dowels are used. Composite beams are made from bars, fastening them with wooden dowels along the entire length.

Now you know the design of rafter systems and how to install rafters correctly different types on the roof of buildings. To supplement the information obtained from the article a clear example, we recommend watching a video about installing rafters.

If you have already installed rafters yourself and have your own installation secrets, share with us and our readers by leaving a comment on the article.

Video

Installation of rafters can be done by one person without assistants:

In the following video you will see mistakes often made during rafter installation:

A gable roof or gable roof is a roof with two slopes, i.e. having 2 inclined surfaces (slopes) of a rectangular shape.

Frame gable roof by virtue of design features ideally combines simplicity of design and maintenance with reliability and durability. These and many other parameters make the construction of a gable roof practical and rational decision for private and commercial housing construction.

In this article, we will look at how to make a rafter system for a gable roof with your own hands. For effective perception of the material, it is presented in the form of step-by-step instructions from A to Z, from selection and calculations, to installation of the Mauerlat and sheathing under the roof. Each stage is accompanied by tables, diagrams, drawings, drawings and photos.

The popularity of the house roof is due to a number of advantages:

• design variability;
• simplicity in calculations;
• naturalness of water flow;
• integrity of the structure reduces the likelihood of leaks;
• efficiency;
• preserving the usable area of ​​the attic or the possibility of arranging an attic;
• high maintainability;
• strength and wear resistance.

Types of gable roof

The installation of a gable roof truss system depends, first of all, on its design.

There are several options for gable roofs (types, types):

The most common roof installation option due to its simplicity and reliability. Thanks to symmetry, a uniform distribution of loads on the load-bearing walls and mauerlat is achieved. The type and thickness of the insulation does not affect the choice of material.

The cross-section of the beam makes it possible to provide a reserve of bearing capacity. There is no possibility of rafters bending. Supports and struts can be placed almost anywhere.

An obvious drawback is the impossibility of arranging a full attic floor. Due to sharp corners, “dead” zones appear that are unsuitable for use.

The arrangement of one angle of more than 45° leads to a reduction in the amount of unused area. There is an opportunity to make living rooms under the roof. At the same time, the requirements for calculations increase, because the load on the walls and foundation will be distributed unevenly.

This roof design allows you to equip full second roof floor.

Naturally, a simple gable rafter roof differs from a broken line, not only visually. The main difficulty lies in the complexity of the calculations.

Design of a gable roof truss system

Building a roof of any complexity with your own hands requires knowledge of the purpose of the main structural elements.

The locations of the elements are shown in the photo.

• Mauerlat. Designed to distribute the load from the rafter system onto the load-bearing walls of the building. To arrange the Mauerlat, a timber made of durable wood is selected. Preferably larch, pine, oak. The cross-section of the timber depends on its type - solid or glued, as well as on the expected age of the structure. The most popular sizes are 100x100, 150x150 mm.

  Advice. For a metal rafter system, the Mauerlat must also be metal. For example, a channel or an I-profile.

• Rafter leg. The main element of the system. To make rafter legs, a strong beam or log is used. The legs connected at the top form a truss.

The silhouette of the roof truss defines appearance buildings. Examples of farms in the photo.

The parameters of the rafters are important. They will be discussed below.

• Puff- connects the rafter legs and gives them rigidity.

• Run:

• Ridge run, is mounted at the junction of one rafter to another. In the future, the roof ridge will be installed on it.

• Side purlins, they provide the truss with additional rigidity. Their number and size depend on the load on the system.

• Rafter stand- vertically located beam. It also takes on part of the load from the weight of the roof. In a simple gable roof it is usually located in the center. With a significant span width - in the center and on the sides. In an asymmetrical gable roof, the installation location depends on the length of the rafters. If there is a broken roof and one room is arranged in the attic, the racks are located on the sides, leaving free space for movement. If there are supposed to be two rooms, the racks are located in the center and on the sides.

The location of the rack depending on the length of the roof is shown in the figure.

• Strut. Serves as a support for the stand.

Advice. Installing the brace at an angle of 45° significantly reduces the risk of deformation from wind and snow loads.

In regions with significant wind and snow loads, not only longitudinal struts are installed (located in the same plane as the rafter pair), but also diagonal ones.

• Sill. Its purpose is to serve as a support for the rack and a place for attaching the strut.

• Lathing. Designed for movement during construction work and fixing roofing material. Installed perpendicular to the rafter legs.

Advice. An important purpose of the sheathing is to redistribute the load from the roofing material to the rafter system.

Having a drawing and diagram indicating the location of all the listed structural elements will help in the work.

Advice. Be sure to add information about the passage of the ventilation shaft and chimney to the gable roof rafter system diagram.

The technology of their installation is determined by the type of roof.

Selection of material for rafters

When calculating the material for a gable roof, you need to choose high-quality wood without damage or wormholes. The presence of knots for beams, mauerlat and rafters is not allowed.

For sheathing boards, there should be a minimum of knots, and they should not fall out. The wood must be durable and treated with the necessary preparations that will increase its properties.

Advice. The length of the knot should not exceed 1/3 of the thickness of the timber.

Calculation of the rafter system of a gable roof

Calculation of material parameters important stage, so we present the calculation algorithm step by step.

It is important to know: the entire rafter system consists of many triangles, as the most rigid element. In turn, if the slopes have different shapes, i.e. are an irregular rectangle, then you need to divide it into separate components and calculate the load and amount of materials for each. After calculations, summarize the data.

1. Calculation of the load on the rafter system

The load on the rafters can be of three types:

• Constant loads. Their action will always be felt by the rafter system. Such loads include the weight of the roof, sheathing, insulation, films, additional roofing elements, finishing materials For . The weight of the roof is the sum of the weight of all its constituent elements; such a load is easier to take into account. On average, the constant load on the rafters is 40-45 kg/sq.m.

Advice. To make a safety margin for the rafter system, it is better to add 10% to the calculation.

For reference: The weight of some roofing materials per 1 sq.m. presented in the table

Advice. It is desirable that the weight of roofing material per 1 sq.m. roof area did not exceed 50 kg.

• Variable loads. They act at different times and with different strengths. Such loads include: wind load and its strength, snow load, precipitation intensity.

In essence, the roof slope is like a sail and, if you take into account the wind load, the entire roof structure can be destroyed.

The calculation is carried out according to the formula: wind load is equal to the regional indicator multiplied by correction factor. These indicators are contained in SNiP “Loads and Impacts” and are determined not only by the region, but also by the location of the house. For example, on a private house, surrounded multi-storey buildings, there is less load. Standing separately Vacation home or the cottage experiences increased wind loads.

2. Calculation of snow load on the roof

The roof calculation for snow load is carried out according to the formula:

Full snow load equal to the weight of the snow multiplied by the correction factor. The coefficient takes into account wind pressure and aerodynamic influence.

The weight of snow that falls on 1 square meter. roof area (according to SNiP 2.01.07-85) is in the range of 80-320 kg/sq.m.

Coefficients showing the dependence on the slope angle are shown in the photo.

Nuance. When the slope angle is over 60 ° the snow load does not affect the calculation. Because the snow will quickly slide down and will not affect the strength of the beam.

• Special loads. Accounting for such loads is carried out in places with high seismic activity, tornadoes, and storm winds. For our latitudes, it is enough to make a safety margin.

Nuance. The simultaneous action of many factors causes a synergy effect. This is worth considering (see photo).

Assessment of the condition and load-bearing capacity of walls and foundations

It should be borne in mind that the roof has significant weight, which can cause damage to the rest of the building.

Determining the roof configuration:

• simple symmetrical;
• simple asymmetrical;
• broken line

The more complex the shape of the roof, the greater the number of trusses and rafter elements needed to create the necessary safety margin.

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The angle of inclination of a gable roof is determined primarily by the roofing material. After all, each of them puts forward their own demands.

• soft roof - 5-20°;
• metal tiles, slate, corrugated sheets, ondulin - 20-45°.

It should be noted that increasing the angle increases the area of ​​space under the roof, but also the amount of material. What affects the total cost of work.

Nuance. The minimum angle of inclination of a gable roof must be at least 5°.

5. Calculation of rafter pitch

The pitch of the gable roof rafters for residential buildings can be from 60 to 100 cm. The choice depends on the roofing material and the weight of the roof structure. Then the number of rafter legs is calculated by dividing the length of the slope by the distance between the rafter pairs plus 1. The resulting number determines the number of legs per slope. For the second, the number must be multiplied by 2.

The length of the rafters for the attic roof is calculated using the Pythagorean theorem.

Parameter "a"(roof height) is set independently. Its value determines the possibility of arranging a living space under the roof, the convenience of being in the attic, and the consumption of material for the construction of the roof.

Parameter "b" equal to half the width of the building.

Parameter "c" represents the hypotenuse of the triangle.

Advice. To the obtained value you need to add 60-70 cm for cutting and moving the rafter leg beyond the wall.

It is worth noting that the maximum length of the timber is 6 m.p. Therefore, if necessary, the timber for the rafters can be spliced ​​(extension, joining, joining).

The method of splicing rafters along the length is shown in the photo.

The width of the roof rafters depends on the distance between opposite load-bearing walls.

7. Calculation of the rafter cross-section

The cross-section of the rafters of a gable roof depends on several factors:

• loads, we have already written about it;

• type of material used. For example, a log can withstand one load, timber - another, laminated timber - a third;

• rafter leg lengths;

• the type of wood used in construction;

• distances between rafters (rafter pitch).

You can determine the cross-section of the beam for the rafters, knowing the distance between the rafters and the length of the rafters using the data below.

Rafter cross-section - table

Advice. The larger the installation pitch of the rafters, the greater the load on one rafter pair. This means that the cross-section of the rafters needs to be increased.

Dimensions of lumber (timbers and boards) for a gable rafter system:

• thickness (section) of the Mauerlat - 10x10 or 15x15 cm;

• the thickness of the rafter leg and tie is 10x15 or 10x20 cm. Sometimes a beam of 5x15 or 5x20 cm is used;

• run and strut - 5x15 or 5x20. Depending on the width of the foot;

• stand - 10x10 or 10x15;

• bench - 5x10 or 5x15 (depending on the width of the rack);

• thickness (section) of the roof sheathing - 2x10, 2.5x15 (depending on the roofing material).

Types of gable roof rafter system

For the roof structure under consideration, there are 2 options: layered and hanging rafters.

Let's consider each type in detail in order to make an informed choice.

Hanging rafters

They are used for roof widths of no more than 6 lm. Installation of hanging rafters is carried out by attaching the legs to the load-bearing wall and the ridge girder. The design of hanging rafters is special in that the rafter legs are under the influence of a bursting force. Hanging rafters with a tie installed between the legs reduce its impact. The tie in the rafter system can be wooden or metal. Often the ties are placed at the bottom, then they play the role of load-bearing beams. It is important to ensure reliable fastening tightening on the rafter leg. Because a bursting force is also transmitted to it.

Advice.
The higher the tightening is located, the greater strength it should have.
If the tightening is not installed, the load-bearing walls may simply “move apart” from the pressure created by the rafter system.

Layered rafters

They are used for arranging roofs of any size. The design of layered rafters provides for the presence of a beam and a stand. The bench lying parallel to the Mauerlat takes on part of the load. Thus, the rafter legs are, as it were, inclined towards each other and supported by a stand. The rafter legs of the layered system work only in bending. And the ease of installation also tips the scales in their favor. The only drawback is the presence of a stand.

Combined

Due to the fact that modern roofs are distinguished by a wide variety of shapes and complexity of configurations, used combined view rafter system.

After choosing the type of rafter system, you can accurately calculate the amount of materials. Write down the calculation results. At the same time, professionals recommend drawing up drawings for each roof element.

Installation of a gable roof rafter system

After the gable roof rafters have been calculated, installation can begin. We will divide the process into stages and give a description of each of them. It will turn out to be unique step-by-step instruction, containing additional information for each stage.

1. Attaching the Mauerlat to the wall

The beam is installed along the length of the wall on which the rafters will rest.

In log houses, the role of the mauerlat is played by the upper crown. In buildings built from porous material (aerated concrete, foam concrete) or brick, the Mauerlat is installed along the entire length of the load-bearing wall. In other cases, it can be installed between the rafter legs.

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Since the length of the Mauerlat exceeds standard sizes lumber, it has to be spliced.

The connection of the Mauerlat to each other is done as shown in the figure.

How to connect the Mauerlat?

The beams are cut only at an angle of 90°. Connections are made using bolts. Nails, wire, and wooden dowels are not used.

How to attach the Mauerlat?

The Mauerlat is installed at the top of the wall. The installation technology provides several ways to attach the Mauerlat:

• strictly in the center of the load-bearing wall;
• with a shift to one side.

Advice.
The Mauerlat cannot be placed closer than 5 cm to the outer edge of the wall.

To protect the timber for the mauerlat from damage, it is laid on a layer waterproofing material, which most often is ordinary roofing felt.

Reliability of Mauerlat fastening important aspect construction. This is due to the fact that the roof slope is like a sail. That is, it experiences strong wind load. Therefore, the Mauerlat must be firmly fixed to the wall.

Methods for attaching the Mauerlat to the wall and rafters

Anchor bolts. Ideal for monolithic structures.

Wooden dowels. Used for log houses and beams. But, they are always used with additional fasteners.

Staples.

Stud or fittings. It is used if the cottage is built from porous materials (aerated concrete, foam concrete).

Sliding mount (hinge). Tying in this way allows for the displacement of the rafter legs when the house shrinks.

Annealed wire (knitting, steel). Used as an additional mount in most cases.

2. Manufacturing of trusses or pairs

Installation is carried out in two ways:

• installation of beams directly on the roof. It is not used often, since it is problematic to carry out all the work, measurements, and trimming at height. But it allows you to completely do the installation yourself;

• assembly on the ground. That is, individual elements (triangles or pairs) for the rafter system can be assembled below and then raised to the roof. The advantage of such a system is faster performance of high-altitude work. The disadvantage is that the weight of the assembled truss structure can be significant. To lift it you will need special equipment.

Advice. Before assembling the rafter legs, you need to apply markings. It is very convenient to use templates for these purposes. The rafter pairs assembled according to the template will be absolutely identical. To make a template, you need to take two boards, the length of each of which is equal to the length of one rafter, and connect them together.

3. Installation of rafter legs

The assembled pairs rise to the top and are installed on the Mauerlat. To do this, you need to make a gash at the bottom of the rafter legs.

Advice. Since the slots on the Mauerlat will weaken it, you can only make cuts on the rafter leg. To ensure that the cut is uniform and fits tightly to the base, you need to use a template. It is cut out of plywood.

Methods of fastening the rafter leg are shown in the figure.

You need to start installing rafter pairs from opposite ends of the roof.

Advice. To correctly install the rafter legs, it is better to use temporary struts and spacers.

A string is stretched between the fixed pairs. It will simplify the installation of subsequent rafter pairs. It will also indicate the level of the ridge.

If the rafter system is mounted directly on the roof of the house, then after installing the two outer rafter legs, the ridge support is installed. Next, the halves of the rafter pair are attached to it.

It is worth noting that the opinions of professionals differ on this issue. Some advise using a staggered fastening pattern, which will allow the increasing load to be distributed more evenly on the walls and foundation. This order involves installing one rafter in a checkerboard pattern. After part of the rafter legs is installed, the missing parts of the pair are mounted. Others insist that it is necessary to mount each pair in a sequential manner. Depending on the size of the structure and the configuration of the truss, the rafter legs are reinforced with supports and racks.

Nuance. Connect additional elements structures using cutting. It is preferable to fix them with construction staples.

If necessary, you can lengthen the rafter leg.

Methods for splicing rafter legs are shown in the photo.

Advice. The method by which the Mauerlat is extended (cut at 90°) in in this case cannot be used. This will weaken the rafter.

4. Installing the ridge of a gable roof

The roof ridge unit is made by connecting the rafter legs at the top.

Roof ridge structure:

• Method without using a support beam (see figure).

• Method using rafter beams. Timber is needed for large roofs. In the future, it can become a support for the rack.

• Method of laying on timber.

• More modern variety The method shown in the photo can be considered for making a ridge assembly.

• Cutting method.

After the rafter system is installed, we perform major fastening of all structural elements.

5. Installation of roof sheathing

The sheathing is installed in any case, and is designed for more convenient movement along the roof during work, as well as for fastening roofing material.

The sheathing pitch depends on the type of roofing material, for example:

• for metal tiles - 350 mm (the distance between the two lower boards of the sheathing should be 300 mm).
• for corrugated sheets and slate - 440 mm.
• under soft roof We lay a continuous sheathing.

Rafter system of a gable roof with an attic - video:

Conclusion

As you can see, despite its apparent simplicity, the installation of a gable roof rafter system contains many pitfalls. But, based on the recommendations given, you can build without any problems reliable design with your own hands.