In order for the constructed building to serve for more than one year, it needs both a reliable foundation and a strong roof system that resists the vicissitudes of the weather. The roof must withstand heavy loads with dignity: heavy snowfalls, sharp gusts of wind, torrential downpours. The roof truss system is best suited for this.
Roof trusses and its types
The truss 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;
- the size of the building;
- dimensions of the house;
- building material for rafters;
- individual preferences of the customer;
- roof loads relevant for a particular region.
The rafter system has:
- crate - bars, in a perpendicular direction, laid on rafter legs;
- screeds that perceive tensile forces;
- wooden racks, located in a vertical position;
- mauerlat - a bar, the installation of which is carried out along the wall, the rafters focus on it;
- rafter legs are a kind of wooden beams that take on the main load of the roof.
Each of these factors is very important, because it is necessary to understand what type of truss system will be best suited for a particular situation.
When it comes to low-rise buildings, the most common are wooden structures. In many cases, three types of truss trusses are used: hanging rafters, layered rafters and a mixed rafter system.
Characteristics of hanging rafters
Hanging rafters are the most elementary type of truss systems, their characteristics:
If the roof of the house is of complex construction, the types of rafters can be alternated. For example, in the presence of supports or the middle main wall, they install layered rafters, and in the absence of such elements, hanging rafters.
Features of layered rafters
For a layered rafter system, the house must be additionally equipped bearing wall located in the middle. There are layered rafters according to the following features:
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 roofing. The walls of the rooms, which are located on the second floor, form vertical supports, these supports are also intermediate racks for rafters.
Part of the rafters that connect one end of the uprights functions as a crossbar for the slopes located on the side, and for the upper part of the structure they are a puff.
At the same time, the horizontal bars perform the following functions: for the upper slopes - Mauerlat, for the side ones - ridge beam. To increase the strength of the roof, struts are mounted that connect the side slopes and vertical racks.
The combined sling system is the most complex and time-consuming to manufacture, but these shortcomings are fully compensated by an increase in the bearing qualities of the roof in the absence of extra supports, especially when there is a need to cover significant spans in the building.
You can increase the bearing qualities of the roof using a mixed truss system Rafter trusses for various types of roofs
During the construction of a certain building, truss systems of one kind or another are necessarily used, and the type of roof will completely depend on the design of the future structure.
Rafter truss for a gable roof
A gable roof is a common roof construction for residential buildings that have no more than three floors. Preference is given to just such a design because of the technical characteristics of the inclined shape of the truss system, and also due to the fact that installation work carried out easily and simply.
As part of the truss system gable roof includes two rectangular inclined planes. The upper part of the building from the front side resembles a triangle. The main components of the two pitched roof- this is a Mauerlat and rafter legs. In order to properly distribute the load along the rafters and walls, struts, crossbars and racks are mounted, thanks to which you can create a durable, rigid, elementary and easy installation scheme for a gable roof structure.
A gable roof is considered the simplest roof system; it is used for residential buildings no more than three floors. On top of the rafters, you can mount a sparse crate or a solid one, and then attach a bituminous coating, tiles or some other type of material to it. The rafters and sheathing itself are usually made of beams or boards, which are fastened with nails, bolts or metal fittings. metal profiles can be used as rafters, due to which significant spans overlap. There is no need to use extra racks and struts.
The device of the truss system for a gable roof allows you to evenly distribute all the existing load along the perimeter of the building. The lower ends of the system focus on the Mauerlat. They are fixed with metal fasteners or staples. By the angle of inclination of the bars for the rafters, you can determine at what angle the roof slopes will be inclined.
The truss system for a gable roof allows you to evenly distribute the load from the roof along the perimeter of the building Rafter system for a hip roof
When arranging a system for a hip roof, you will need to install different types of rafters:
- conjurers (shortened);
- side;
- hip main;
- sloping (diagonal elements that form a slope in the shape of a triangle).
The rafter legs located on the side are made of board, and they are mounted identically to the details of a traditional pitched roof with a layered or hanging structure. Hip main rafters are layered parts. For sprigs, boards or bars are used, which are attached not only to the Mauerlat, but also to the diagonal beams.
To install this type of construction, the angle of inclination is accurately calculated, as well as the cross section of the sloping beams. The dimensions of the parts also depend on the length of the span.
To hip roof not deformed from heavy load, you should accurately calculate the angle of inclination of the diagonal beams for the rafters Observe symmetry when installing diagonal beams for rafters, otherwise the roof is deformed from a significant load.
Rafter system for sloping roofs
A broken roof is a structure with rafters, which consist of several individual elements. Moreover, they should be located at different angles relative to the horizon. And since the lower rafter part is almost vertical, the attic of the building receives additional space, so that it can be used as a living space. The device of this type of roof is carried out during the construction of a four- or gable rafter structure.
count four-slope system rafters are needed by professionals, but a gable broken roof can be made independently, since its installation is very simple. To do this, it is necessary to install a support frame, which should consist of runs, as well as racks. Horizontal parts are fixed with hanging rafters. But to the Mauerlat, the supports of the sloping roof are fixed with shortened legs of the rafters.
The assembly of rafters for a broken gable roof can also be performed by non-professionals, since the installation of such a roof is very simple. "Cuckoo" in the roof truss
The so-called cuckoo on the roof is a small ledge 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 controlling the parameters of the entire structure: the depth of the cut, the angle of inclination and other factors. However, before that, the necessary measurements are made.
The first stage of work begins with the installation of a power plate (a beam with a section of 10x10 cm, which is needed to support the lines). The rafter system acts as a skeleton for roofing material. To stiffen the structure, spacers are used, which are mounted between the two legs of the rafters.
After the installation of the truss truss is completed, a sheathing is laid, the type of which depends on the roof covering purchased. The installation of the crate 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 in installing such a rafter system is the location of the internal corners. In these places, snow can accumulate, which means that the load will increase, which is why a continuous crate is made.
"Cuckoo" on the roof is called a small ledge on the attic floor, under which there is an additional window Chalet roof truss truss
A feature of a device of this design is the removal of visors, as well as overhangs outside the house. In addition, there must be rafters and beams for the roof, which extend up to three meters on the sides of the building. Each of these elements is fixed 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 creating large overhangs, it is necessary to carry out installation reinforced belt in parallel with the installation of studs for Mauerlat. It is necessary to make anchors that help fix the consoles. In this case, the rafters will be perfectly fixed with anchors and, in addition, tie-ins.
To carry out the side cornices, a ridge beam is made, after which beams are taken out at the Mauerlat level, which must be identical to the length of the ridge. The truss is based on these structural details, and in the future - building material for the roof.
When designing a building, the angle of the roof-chalet 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 sloping roof will withstand the load from the snow, but it is necessary to install a reinforced roof truss. Before installing the roof-chalet, a building project is prepared, because the originality of the roof itself, as well as long cornices and its overhangs, oblige this.
The roof in the style of a chalet is characterized by visors, taken out several meters outside the house. Roof truss designed for soft roofing
Soft roof is being done different ways, but exist in technological methods its buildings General characteristics. Initially, you need to prepare. When equipping a roof for a house made of foam concrete or other material, a Mauerlat is first installed, then a cut is made under the ceiling beams in increments of up to one meter in the upper crowns of the building. The distance between the boards is calculated based on the type of rafter structure.
- Mount individual parts of the rafter system. To completely eliminate the risk, the boards of the rafter legs on the ground are attached with screws. After creating a truss truss, it is raised to the top of the building.
- Fix all elements of the rafters with ceiling overlap, internal boards, jibs, as well as crossbars. Further, this basis for the roof will become a single whole structure.
- The next stage is the crate, which is under soft roof installed with little or no gaps. Gaps of no more than 1 cm are allowed. Quite often, leveling plywood is installed on top of the boards. Her sheets are laid according to the method brickwork. The resulting joints do not align with the gaps between the plywood and the board.
If the length of the boards of the crates is not enough, then the joints of the parts must be located in different places. In this way, areas that have been weakened can be correctly distributed.
Self-manufacturing of the truss system
Before the installation of the truss system begins, the Mauerlat must be fixed to the longitudinal walls with anchors. Next, you need to decide on the desired section of the legs 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.
Using various insulation you need to choose the ideal distance between the elements of the rafters in order to reduce the number of scraps of thermal insulation.
Installation of the truss system must be carried out in the following order:
- A template is made according to which the farm is assembled. 2 boards are taken, corresponding to the length of the rafters, and connected to each other from only one edge with a nail.
A template for rafters called "scissors" will help you quickly assemble all truss system roofing - You get a design called "scissors". Its free edges are placed on supports at the points of contact of the rafter legs. The result should be the final angle, that is, the angle at which the roof slope will be tilted. It is fixed by several long nails and cross boards.
- A second template is made, thanks to which the cuts on the rafters are installed. It is made from plywood.
- Special mounting cuts are cut out on the rafters (a prepared template is used for this purpose) and connected at an angle of inclination of the slope. You should get a triangle that rises to the roof along the stairs. Next, it must be attached to the Mauerlat.
- Initially, two side gable rafters are mounted. Their correct installation in the vertical and horizontal plane occurs due to temporary struts attached to the rafters.
For the correct installation of the entire rafter system, the first pair of rafters is installed on the roof - A cord is stretched between these tops of the rafters. It will indicate the future skate and the level of other rafters located in the gap.
- Raise and mount the remaining rafters at the initially calculated distance, which should be at least 60 cm from each other.
- If a bulky construction of rafters is provided, then it is additionally strengthened with struts, supports, and so on.
The bulky construction of the rafters is additionally reinforced with struts and supports. - On special supports, a ridge beam is installed, 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 nodes of a standard truss system
The structural strength of the rafters depends on the ideally selected section of the boards, as well as on High Quality truss knots. The connection of parts for the roof structure is done in accordance with established rules.
The main typical nodes in the truss system:
- supporting knot of rafters on the Mauerlat;
- ridge;
- a node for combining the upper puffs and the entire truss system;
- fixing 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 select all the nodes. In each design, they are made in different ways, since it depends on different nuances: the type of roof, its size, and the angle of inclination.
Rafter from profile pipe- this is a metal structure that is assembled using lattice rods. The very production of such farms is a very time-consuming process, but also more economical. Paired material is used for the manufacture of rafters, and scarves are connecting elements. The construction of rafters from profile pipes is assembled on the ground, while riveting or welding is used.
Thanks to such systems, any spans are blocked, but it is necessary to make the correct calculation. Provided that all welding work will be done with high quality, in the future it remains only to transfer the structural elements to the top of the building and assemble them. Bearing rafters from a profile pipe have many advantages, such as:
Crossbar in the truss system
Rigel is a fairly broad concept, but in the case of roofs it has a certain meaning. The crossbar is a horizontal bar that connects the rafters. Such an element does not allow the roof to "burst". 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 truss system.
It can be fixed in various places between the legs of the lines. 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 truss system:
- bolts;
- nuts;
- studs with washers;
- special fasteners;
- nails;
- mixed fasteners, when different types of fasteners are used in parallel.
Mounting exists with a tie-in or overhead. In general, the crossbar is a design unit, as, indeed, the entire roof sling system.
The crossbar in the truss system is designed to reinforce the roof structure Rafter system fastening
To ensure the reliability of the rafter system, it is necessary to initially find out how they are fastened to the supporting roof and the ridge. If fastening is done to prevent deformation of the roof during shrinkage of the house, then the rafters are fixed on top with a hinged plate or a nut with a bolt, and from below - with a sliding support.
Hanging rafters need tighter and reliable fastening in the skate, so in this case you can apply:
- overhead metal or wooden plates;
- cutting method;
- connection with long nails.
In the layered system, the rafter legs are not connected to each other, since they are attached to the ridge run.
The rafters are fastened to the Mauerlat by cutting down, which is done in the rafter leg. Thanks to this method of fastening, the support of the roof will not be weakened. Cutting is also done when installing rafters on floor beams. In this case, the incision is made in support beam.
Video: how to make rafters with your own hands
Thus, a perfectly matched system of rafters and their structural characteristics will help create the basis for a reliable roof for your home.
Roof structure
Any low-rise residential building is built so that when minimal cost materials to get a long service life and maximum usable space. From this point of view, of particular interest are attic space, allowing you to double the usable area without any additional changes. On the other hand, the design of roofs, the truss systems of which are designed to create a residential attic, will be more complex.
Today during construction country houses several types of roofs are used:
- Shed. This is the easiest option, since here you can often do without a ridge beam and even without a number of other elements that are required in other cases. Typically, such solutions are used in the construction of utility rooms, outbuildings and garages, but they are also suitable for residential buildings with a small area.
Roofs of this type are among the most economical. They require a minimum amount of roofing material and wood, which is used for roof structures.
- Gable. This is the second most difficult type of roof to create, since only two slopes are required here, and the truss system, as a rule, is no different. Roofs of this type are one of the most popular in modern suburban construction, because, despite their simplicity, they do an excellent job with wind and snow load, and also suitable for creating an attic.
- Four-slope. This category includes hip, hipped and broken roofs. In the latter case, it is worth mentioning that we are talking about a type of gable roof, which received four slopes due to a break. Such structures are more complicated than the two previous options, however, the aesthetics of the building along with them are higher.
- Gable and multi-slope. Complicated rafter attachment points, special technology devices and the need for careful calculation are the reasons why only professionals build such roofs. Of course, you can try to build something like this on your own, but only if you are an expert in this field.
The choice of roof type depends on the climate in the region and the wind load. The second point is the angle of inclination of the slopes, which depends on the location of the building, the presence of nearby arrays of buildings or trees, and the climate.
Slope angle
An ideal option for any roof is a design that will require minimal attention from the owner. Generally, self-cleaning roofs are attractive as they allow you not to worry about what builds up. a large number of snow.
The accumulation of snow cannot be neglected, since its mass after an intense snowfall can be up to 200 kg per m2, which means that only very strong rafters can withstand such a weight.
An alternative is the construction of the original roof of the type of alpine houses, which have a very large slope of the slopes, often descending almost to the ground. It should be noted that to obtain the effect of snow removal, an angle of 45 degrees is required. In this case, precipitation will roll down the pavement under its own weight.
On the other hand, an increase in the slope of the slopes leads to an increased consumption of roofing and building materials. Moreover, if it is planned to build an attic, then the insulation will be expensive, because the greater the height of the ridge, the higher the consumption of this material. In addition to the cost of a pitched roof, its type also affects the choice of slope. For non-exploited roofs, it is not necessary to use a large amount of insulation, however, increasing the angle of inclination does not always justify itself.
The main sign of an unused roof is a different scheme of the truss system and the absence of a gap between the ceiling and the external protective structure. Usually this flat roofs or those that have a very slight slope. Their main drawback is that during heavy snowfalls, snowdrifts can form, which will not only create a load on the ceiling, but also arrange a “flood” during the thaw.
The type of roofing material will need to be determined in advance, since it must be taken into account when calculating the angle of inclination of the rafters. Typically, flexible materials and bituminous coatings are selected for multi-gable designs. For example, metal tiles, corrugated board or galvanized iron. Other options, such as slate or shingles, are better for roofs that have a simple configuration.
Classical tiles are rarely used today, since they require a fairly large slope angle, ranging from 30 to 60 degrees.
Bituminous materials can be used even at small angles of inclination (from 8 degrees), and the limit value for them is 18 degrees. Metal tiles and asbestos-cement sheets are used at angles from 14 to 60 degrees. We will not dwell on the consideration of roofing materials, since this issue has already been covered on our website.
Spacer and non-spacer layered rafters
These are two types of rafters, one of which is chosen taking into account the shape of the house, roof and dimensions. future design. Rafter rafters are an option suitable for single or double pitched roofs. Their main feature is that two points of support are used. On the one hand, the rafter leg rests on the roof ridge, and on the other, on the wall of the house.
Non-expanding layered rafters are mounted in such a way as to avoid bursting pressure on the wall of the house. Usually roof structures Roofs are created using one of the following options:
- The rafter leg rests on the Mauerlat. It is hemmed with a bar and fixed by cutting with a tooth. In addition, additional wire insurance is performed. The upper part of the beam is mounted on a ridge run. Fastening is carried out using the sliding support principle.
- The bottom of the rafter is attached through the use of a movable joint. As a mounting point, not only Mauerlat, but also piece bars can be used. The upper part is fixed with a bolt, nails or in another way after it is laid on the ridge run.
- The third option involves the installation of layered rafters with rigid attachment to the run. Nails, studs or other fasteners can be used here.
If the thickness of the rafters, which was originally chosen, turns out to be insufficient, then in the process of work, supports can be used that are mounted under too long elements in those places where maximum deflection is expected.
Spacer rafters Laminated rafters are spacer. In this case, it is planned to create such a structure, where a bursting force will be transmitted to the walls of the house. The installation method in this case is the same as in the previous one, however, the fastening of the rafter legs is fixed, so the entire system will receive internal stress. It is worth saying that such an option is a transitional scheme that separates non-thrust layered rafters and hanging ones.
hanging rafters
This design of the truss system will be ideal when it is necessary to overlap large spans, the length of which exceeds 7 m. In such a situation, there is only one point of support for the rafter leg - the wall. The upper part of the beam is connected to the counter element located on another slope. There are several options for joints: half a tree, a slotted spike, metal plates.
In order for the rafter legs to be securely fixed, it is necessary to connect them with a puff. Usually it is a strong beam that is attached to the bottom of these elements. Of course, it can be placed higher, but in this case the load will increase, which means that the weight of the beam will also need to be increased. In such a situation, one of the following mounting options for rafter legs can be used:
- The rafter leg is connected to the Mauerlat with the help of an additional gash and is securely held with nails. The second option involves using metal corners. Then the upper parts of the rafters are joined end-to-end, and the lower ones are held by a puff. In this case, the top of the rafter legs can also be pressed against the ridge run, which will rest on the headstock.
- The puffs are set so that the heels of the rafter legs rest with a cut-out tooth on the edges of the puffs, which, in turn, are attached to the Mauerlat. The tops of the rafters are held up with wooden braces.
- Floor beams can be selected for the role of puffs. In this case, their ends should extend beyond the walls by at least 55 cm. The cutting of the socket for the tooth is carried out no closer than 25-40 cm from the edge of the wall.
- In log houses, the rafter leg is fastened to the upper crown through a spike-nest connection. You can also use special metal mounts, such as sliders, sleds, etc. The latter option will allow the structural elements to move and avoid the occurrence of additional stresses.
The puffs themselves can be solid beams or constituent elements. The splicing of the bars is done by any convenient way, such as oblique tooth, overlap, etc. Installation of puffs can be performed not only at the level of the heels of the rafters, but also in any other place.
If roof rafters are used, the dimensions of which are more than eight meters, then we recommend creating a structure from a headstock and struts, as well as using racks and crossbars, which help to increase the reliability of the rafter system.
Rafters for different types of roofs
The simplest option is to construct shed roof, the rafters of which rest against the walls of the building. The length of these elements cannot exceed 4.5 meters, but there is also a solution for covering large areas. In this case, it is recommended to use props or racks that will hold the extended structure.
Most gable roofs look like twins, but they internal structure can be very different. Today there are four options:
- A ridge run is used, on which the legs of the rafters rest. The slopes are reinforced by the use of rafter legs, and the run is held by racks. The racks themselves are installed on the bed. The width of this type of roof can reach 10 m.
- The second option involves the use of rafter legs, the lower parts of which rest against the rack of the ridge run, and the upper parts against the fight (puff) connecting the rafter legs closer to the ridge. In this case, the width of the roof increases to 14 m.
- There is no ridge run. It is replaced by a beam located under one of the slopes. In addition, a puff, rafter legs and a stand resting on a bed are used. The angles of inclination of the rafter legs vary from 45 to 53 degrees. This option compared to the previous one, it does not give much gain in the width of the roof, however, it is suitable when the supporting wall is not located in the center of the building, but is shifted to the side.
- In the case when it is required to cover wide buildings, symmetrical structures can be used using two runs located in parallel under the rafter legs of the slopes. Such gable roofs involve the use of two puffs, the upper of which connects the rafters, and the lower one connects the racks and rafter legs. The width of the structure in this case can reach 16 m.
The distance between the rafters is selected taking into account their length and cross section. For example, for a section of 40x150 mm, a step of 60 cm is required, for 50x150 - 90 cm, and for 100x150 - 215 cm.
The hip roof is another option that is common today, which has proven itself well for country houses. It differs in that it does not have pediments, the place of which is occupied by additional slopes - hips. In the general case, the design assumes the presence of a run, and ordinary rafters on the main slopes and hip rafters on the side ones. Hip rafters rest on long diagonal elements, where they meet with upper parts conventional rafter legs. For such roofs, it is recommended to use reinforced strapping.
The sloping roof completes the list, as it has a rather complex design. Here, a method is used that involves the creation of a frame for rafter legs, consisting of a horizontal bar and vertical racks, after which the remaining elements are installed. The upper crossbar of the U-shaped frame acts as an attic floor, but the ridge stand also rests on it.
The distance between the rafters of the truss system in this case should be chosen taking into account the load acting on the roof, the thickness of the beam used and the angle of inclination of the slopes.
The main issues regarding the construction of the truss system for various types of roofs were discussed above, therefore given material can be used as a short guide to help you quickly understand the issues of roof construction.
Roof installation is a complex multi-stage process. In order to independently assemble and install the truss system, it is necessary to carefully study the methods of connecting the elements, calculate the length of the rafters and the slope angle, and select the appropriate materials. If you do not have the necessary experience, you should not take on complex designs. The best option for a small residential building - do-it-yourself gable roof.
A standard roof of this type consists of the following elements:
Mauerlat is a beam laid on top of the walls along the perimeter of the building. It is fixed with threaded steel rods immured into the wall or anchor bolts. The beam must be made from softwood and have a square section of 100x100 mm or 150x150 mm. Mauerlat takes on the load from the rafters and transfers it to the outer walls.
rafter legs- these are long boards with a section of 50x150 mm or 100x150 mm. They are attached to each other at an angle and give the roof triangular shape. The design of their two rafter legs is called a truss. The number of farms depends on the length of the house and the type roofing. The minimum distance between them is 60 cm, the maximum is 120 cm. When calculating the pitch of the rafter legs, one should take into account not only the weight of the coating, but also the wind load, as well as the amount of snow in the winter.
It is located at the highest point of the roof and most often represents a longitudinal beam connecting both slopes. From below, the timber is supported by vertical racks, and the ends of the rafters are attached to the sides. Sometimes the ridge consists of two boards, which are nailed to the top of the rafters on both sides and connected at a certain angle.
Racks - vertical bars with a section of 100x100 mm, located inside each truss and serving to transfer the load from the ridge run to the load-bearing walls inside the house.
The struts are made from timber scraps and set at an angle between the uprights and the rafters. Struts strengthen the side faces of the farm, increases load bearing capacity designs.
Puff - a beam connecting the lower parts of the rafters, the base of the truss triangle. Together with struts, such a beam serves to strengthen the truss, increases its resistance to loads.
Lying is a long beam with a section of 100x100 mm, laid along the central bearing wall on which the vertical posts rest. Lying is used when installing layered rafters, when the run between the outer walls is more than 10 m.
The crate is a board or timber stuffed on the rafters. The crate is solid and with gaps, depending on the type of roof. It is always attached perpendicular to the direction of the rafters, most often horizontally.
If there is no more than 10 m between the outer walls and there is no load-bearing wall in the middle, arrange hanging rafter system. With such a system, the upper ends of adjacent rafters are sawn at an angle and connected to each other with nails, excluding the installation of racks and ridge timber. The lower ends of the rafter legs rest on the outer walls. Due to the lack of racks, the attic space can be used to equip the attic. Very often, floor beams perform the function of puffs. To strengthen the structure, it is recommended to install the upper puff at a distance of 50 cm from the ridge.
In the presence of a central supporting wall, the arrangement is more justified layered truss system. A bed is laid on the wall, support posts are attached to it, and a ridge beam is nailed to the posts. This installation method is quite economical and easier to perform. If the ceilings in the interior are designed at different levels, the racks are replaced with a brick wall dividing the attic into two halves.
The installation process of the roof includes several stages: fastening the Mauerlat to the walls, assembling the truss trusses, installing the rafters on the floors, installing the ridge, fastening the batten. All wooden elements before assembly are carefully treated with any antiseptic composition and dried in the air.
For work you will need:
- timber 100x10 mm and 150x150 mm;
- boards 50x150 mm;
- boards 30 mm thick for lathing;
- ruberoid;
- metal studs;
- jigsaw and hacksaw;
- hammer;
- nails and screws;
- square and building level.
IN wooden houses Mauerlat functions are performed by logs of the last row, which greatly simplifies the workflow. To install the rafters, it is enough to cut on inside logs grooves of the appropriate size.
IN brick houses or buildings from blocks, the installation of the Mauerlat is as follows:
Mauerlat bars should form a regular rectangle and be in the same horizontal plane. This will facilitate further installation of the roof and provide the structure with the necessary stability. In conclusion, markings are made on the bars for the rafters and grooves are cut along the thickness of the bar.
When choosing a hanging truss system, it is necessary to assemble the trusses on the ground, and then install them above the floors. First you need to draw up a drawing and calculate the length of the rafter legs and the angle of their connection. Typically, the roof slope is 35-40 degrees, but in open, heavily ventilated areas, it is reduced to 15-20 degrees. To find out at what angle to connect the rafters, you should multiply the angle of the roof by 2.
Knowing the length of the run between outer walls and the angle of connection of the rafters, you can calculate the length of the rafter legs. Most often, it is 4-6 m, taking into account the cornice overhang 50-60 cm wide.
The upper ends of the rafters can be fastened in several ways: overlap, butt and "in the paw", that is, with cut grooves. For fixing use metal pads or bolts. Next, the lower and upper puffs are mounted, and then the finished trusses are lifted up and installed above the ceilings.
The extreme trusses are attached first: with the help of a plumb line, the rafters are set vertically, the length of the overhang is adjusted and attached to the Mauerlat with bolts or steel plates. So that during the installation process the farm does not move, it is strengthened with temporary jibs from a bar. After installing the extreme rafters, the rest are exposed, keeping the same distance between them. When all the trusses are fixed, they take a board with a section of 50x150 mm, the length of which is 20-30 cm longer than the length of the eaves, and nail it along the upper edge of the slope. Do the same on the other side of the roof.
The first option: on the rafter leg, at the place of contact with the Mauerlat, a rectangular groove is cut out 1/3 of the beam width. Stepping back from the top of the box 15 cm, a steel crutch is driven into the wall. The rafter is leveled, the grooves are aligned, then a wire clamp is thrown on top and the beam is pulled close to the wall. The ends of the wire are securely fixed on the crutch. The lower edges of the rafters are carefully cut off circular saw leaving an overhang of 50 cm.
The second option: the upper rows of walls are laid out with a stepped brick cornice, and the mauerlat is placed flush with the inner surface of the wall and a groove is cut in it for the rafter. The edge of the rafter leg is cut at the level of the upper corner of the eaves. This method is simpler than the others, but the overhang is too narrow.
Third option: beams ceilings released over the edge outer wall by 40-50 cm, and truss trusses are installed on beams. The ends of the rafter legs are cut at an angle and rest against the beams, fixing with metal plates and bolts. This method allows you to slightly increase the width of the attic.
The device of layered rafters
1 shows the cutting of the struts of the rafters into a bed laid on intermediate supports, and in Fig. 2 - supporting the rafter leg on the Mauerlat
The procedure for installing a layered truss system:
When the main elements are fixed, the surface of the rafters is treated with flame retardants. Now you can start making the crate.
A beam of 50x50 mm is suitable for the crate, as well as boards with a thickness of 3-4 cm and a width of 12 cm or more. Waterproofing material is usually laid under the crate to protect the truss system from getting wet. The waterproofing film is laid in horizontal stripes from the eaves to the roof ridge. The material spreads with an overlap of 10-15 cm, after which the joints are fastened with adhesive tape. The bottom edges of the film must completely cover the ends of the rafters.
Between the boards and the film must be left ventilation gap, therefore, first they fill the film with wooden slats 3-4 cm thick, placing them along the rafters.
The next stage is the sheathing of the truss system with boards; they are stuffed perpendicular to the rails, starting from the roof eaves. The step of the lathing is affected not only by the type of roofing, but also by the angle of inclination of the slopes: the larger the angle, the more distance between boards.
After the installation of the battens is completed, they begin to sheath the gables and overhangs. You can close the gables with boards, plastic panels, clapboard, waterproof plywood or corrugated board - it all depends on financial capabilities and personal preferences. Sheathing is attached to the side of the rafters, nails or self-tapping screws are used as fasteners. Overhangs are also hemmed various materials from wood to siding.
Video - Do-it-yourself gable roof
In previous articles that described the roof structure, we already said that the hanging rafters rest on the Mauerlat with their lower end, and the upper ends of adjacent rafters abut (either directly or through a ridge board) against each other. In the most simplified version, this is shown in Fig. 1:
Picture 1
I think it is obvious to everyone that with such an arrangement, there are bursting loads on the walls. To reduce them, puffs are added to the truss truss. But let's talk about everything in order.
As an example, let's take a house with a semi-attic in the Volgograd region. The sum of snow and wind loads is 155 kg/m 2 . The dimensions of the house box are 8x10 meters. The thickness of the walls is 50 cm. The angle of inclination of the slopes is 40 ° (see Fig. 2):
Figure 2
STEP 1: We install . In this design, in addition to the usual loads, bursting forces will act on it, tending to move it off the wall. For more reliable fastening, you can add more metal mounting plates to the anchor bolts (or studs) (see Fig. 3). The plates can be fixed to the wall, for example, with frame anchors, and to the Mauerlat, you can use nails, self-tapping screws, and capercaillie.
Figure 3
STEP 2: We determine the required section of the rafters. We make the calculation in the "Arch" tab (see Fig. 4):
Figure 4
The cross section of the rafters is taken 50x200 mm in increments of 60 cm.
A question may immediately arise here. Where do we get the distance from the ridge to the puff (crossbar). We have it equal to 2 meters. Earlier on the site, we already said that before proceeding with the construction of the roof, we need to make a drawing of it on paper, be sure to scale (in compliance with all proportions). If you know how, you can draw on the computer. Further, according to this drawing, we determine all the dimensions and angles of interest to us.
Puffs are installed between hanging rafters to reduce bursting loads on the walls. The lower the puff, the more useful it is. Those. the less bursting load falls on the walls. But since in our example, puffs still play the role ceiling beams attic floor, then we determine the height of their location based on the height of the ceilings we need. I took this height of 2.5 meters (see Fig. 5):
Figure 5
STEP 3: We make a template for the lower rafter cut. To do this, we take a piece of board of the section we need about a meter long, apply it to the Mauerlat at our angle of inclination of the slopes of 40 ° (orient yourself along the pediment) and make the markup, as shown in Figure 6:
Figure 6
The vertical and horizontal lines we need (shown in blue) are drawn using a level. Depth washed down 5 cm.
So let's make a template.
STEP 4: We install a ridge board, through which all the rafters will be interconnected. First you need to outline the place of its installation.
We take the template made earlier and apply it to the Mauerlat. We are interested in the size shown in Figure 7 (here it is 18 cm):
Figure 7
Let's call the lower point on the Mauerlat point "A".
We transfer the resulting size to the top of the pediment, make markings in accordance with Figure 8:
Figure 8
Let's designate the lower right corner as point "B". Now we can measure the distance from the attic floor to point B (the length of the temporary posts).
We install strictly vertically temporary racks from a 50x200 board and put a ridge board of the same section on them. Under the racks for their fixation, you can put a board fixed with simple dowel nails to the floor slabs (see Fig. 9). It is not necessary to fasten strongly, then we will remove it. The distance between the racks is not more than 3 meters.
Figure 9
We fasten the ridge board to the gables with metal brackets. The stability of the racks is provided by jibs.
Perhaps you could see somewhere how hanging rafters are installed without a ridge board (see picture on the left). This method is very familiar to me, we used to do this too.
But when we tried the option with a ridge board, we settled on it. Despite the fact that it takes some time to install the racks and the ridge board, the subsequent installation of the rafters is much more convenient and faster. In the end, you win in time. In addition, the design is more stable and more geometrically even.
STEP 5: We manufacture and install rafters.
We do the rafter like this: we take a board of the desired length, apply a template to one end, mark it out and make the bottom washed down. Then we measure the distance between points "A" and "B" with a tape measure (see Fig. 7-8). We transfer this size to our workpiece and make the top washed down. The angle we need for the top notch is on our template (see Fig. 10). We have it equal to 90 ° + 40 ° = 130 °
Figure 10
Thus, we put all the rafters (see Fig. 11)
Figure 11
The connection of the rafters with the Mauerlat here does not look the same as it was, for example, I think you have already understood that this is due to the presence of bursting loads, which were not in that version. However, in future articles you will see that this option is just one of the possible, and not the only correct one. We will use more familiar to us washed down. The main thing is to securely fasten the rafters to the Mauerlat.
At the top, the rafters will protrude beyond the ridge board. You can drive small bars between them, or you can leave it as is. This, in principle, does not play any role (see Fig. 12):
Figure 12
We fasten the rafters to the ridge with nails or self-tapping screws. It is not necessary to install any additional fasteners here. In general, in this design, thanks to the lower gash, the rafters are obtained, as it were, sandwiched between the Mauerlat and the ridge board.
STEP 6: Installing braces.
We make them from boards of the same section as the rafters. There is no need to make any cuts and cuts here. We make puffs superimposed on the rafters. We fasten them with several nails and tighten them with a threaded stud with a diameter of 12-14 mm (see Fig. 13):
Figure 13
Thus, we install all the puffs and remove our temporary racks on which the ridge board was placed:
Figure 14
Now you can guess the purpose of the small windows in the upper part of the pediment. Through them, ventilation of the insulation will be carried out, which will lie on the ceiling of the half-attic floor (between puffs).
STEP 7: We attach the filly of the cornice overhang to the lower ends of the rafters (see Fig. 15). We make them from boards with a section of 50x100 mm. We make the length of the filly such that we get a cornice overhang of the width we need (40-50 cm), and that it overlaps the rafter by at least 50 cm. We fasten the filly with several nails and tighten with 2 threaded studs. In the middle part, for additional emphasis on the wall, you can fasten a small bar to the filly with nails or self-tapping screws.
Figure 15
Please note that at the junction of the filly of the overhang with the Mauerlat, we do not drink on it, because. this will reduce it without large section. Here we first make a small cut in the Mauerlat itself (see Fig. 16):
Figure 16
To make the cornice even, use a lace. First put the extreme fillies, then pull the lace between them and put all the rest. In Figure 17 the shoelace is shown in blue.
Figure 17
Step 8: The following steps are already known to us from previous articles. We put the fillies on the pediment and fasten the wind boards (see Fig. 18):
Figure 18
STEP 9: Now we can leave the cornices in the form in which they are.
Let's see another version of the eaves overhangs (see Fig. 19):
Figure 19
These "earrings" are made from inch boards 10-15 cm wide. We fasten them with self-tapping screws.
Thus, now it remains for us to hem the siding belts to the bottom of the cornices; fastened to the rafters protective film, make a counter-lattice and crate; cover the roof with roofing material. We have covered these steps in previous articles. I think it makes no sense to repeat here and when considering other roof structures in the future.
The gable roof truss system is designed for roofing in the form of two rectangles located at a certain angle to each other in the upper part of the structure. This design is often used in the construction of private low-rise buildings, various buildings household and business purposes. On industrial and trade enterprises a gable roof is installed on buildings for various purposes, having a significant length several times greater than the width. The design contains two slopes of different lengths. On the front side, a short slope with a large angle of inclination is installed, on the back - a long one, with a smaller angle of inclination. This configuration allows the main part of atmospheric precipitation to be directed to the non-working zone of the enterprise territory.
Figure 1. Scheme of fillies.
The construction of a gable roof is one of the low-cost options that does not require significant physical effort.
It is performed relatively simply with little experience working with wood material.
Typical bearing elements of the system, specific terms
Figure 2. Scheme of the crate.
In the manufacture of details of the gable roof truss system, softwood lumber is used. wood hard rock use is undesirable due to specific gravity. Most of the elements have specific names that are understood mainly by specialists:
- Lezhen - a bar with a section of 150x150 mm, 180x180 mm. It is laid on the surface of the internal load-bearing wall. Designed for leveling the surface and distributing loads from racks.
- The rafter leg, or rafter, is a piece of timber or thick board. The main element of the triangular roof structure, bearing the main load from snow, rain, wind and other atmospheric phenomena. The distance between the rafter legs can be from 0.6 to 1.2 m. The step size mainly depends on the plumb line of the roofing material, in some cases, the characteristics of the roofing material should be taken into account.
- Mauerlat is a square beam with a side size of 150-180 cm. It is laid on the surface of external load-bearing walls. When installing, it must be fixed with anchor bolts or in another reliable way. Distributes the load from the rafter legs to the load-bearing walls.
All parts of a gable roof are interconnected in various ways. Previously, structures were assembled mainly using staples, nails, threaded studs. Now manufacturers of building materials offer a wide range of different brackets for assembling roofs of any configuration. Most parts are fastened with self-tapping screws of the required diameter and length, reinforced with special spikes in the brackets.
Back to index
Additional elements of the rafter system
Figure 3. Scheme of an arch with three hinges.
In addition to load-bearing parts, additional reinforcing elements are used in structures:
- Filly (Fig. 1) - used to increase the length of the rafter legs. Are established in the lower part for the device of cornice overhang. The thickness of the fillies is somewhat smaller sizes rafters.
- Roof overhang, or cornice overhang, is a roof element that protrudes beyond the edge of the wall by about 40-50 cm. Designed to protect walls from atmospheric precipitation.
- The ridge is an element that connects all the rafter legs of the system in the upper part. Installed in a horizontal position.
- Sheathing (Fig. 2) - boards or bars installed for fixing the roof. They are located perpendicular to the rafter legs, additionally performing the function of their fastening. They take the main effort from the roofing material, distribute it to the rafters. For the device, it is desirable to use edged lumber. At limited funds you can use unedged, clearing it of bark. If the roof is made of soft material, the crate is made solid. This option can be made from boards or plywood treated with protective materials from high humidity. When corrugated board is used, the crate is performed with a certain step, depending on the weight of the material and its design features.
- Struts - elements of timber or thick boards that reinforce the main structure. Distribute the force from the rafter legs to the bearing parts. Assembled structure from struts and puffs, it was called a farm - an enlarged part with the necessary margin of safety.
- Racks - made from pieces of lumber of rectangular or square section. Are established in vertical position under a descent of slopes. The load from the corner connection of the roof rafters is distributed through the posts to the internal load-bearing wall.
- Puff - a bar or board that fastens the rafters in a hanging system. Creates a rigid triangle shape between rafter legs, compensating for sprawl.
For the manufacture of additional parts, you can use lumber with a section similar to that of load-bearing parts. In order to save money, you can calculate and purchase products of a smaller section.
Back to index
Two typical ways to arrange truss systems
Figure 4. Scheme of connecting the lower ends of the parts.
The gable roof truss system can be arranged in two main ways:
- hanging rafter system;
- layered system.
The suspension system is used for buildings with a distance between the outer walls of less than 10 m, without an internal load-bearing wall in the middle of the building. In a different configuration of the building, a layered rafter structure is used.
If the building has columns located along one of the central axes, it is possible to use combined option. Rafter legs located above the columns are mounted with emphasis on the surface of the columns, hanging rafters are installed between them.
Back to index
Hanging truss system
In structures of this type, the installation of truss beams is carried out on the surface of the outer walls. The disadvantage of this method is the occurrence of force, bursting the walls. To compensate for the load, the beams are pulled together by tightening. The design takes the form of a rigid triangle that retains its shape under the influence of loads. In some cases, floor beams can play the role of puffs. Such a scheme is used when arranging an attic in the attic space.
Hanging rafters can be made in various versions:
- A simple version of the arch with three hinges (Fig. 3) - the design is a rigid triangle, the two sides of which are the rafter legs. The main load creates a bending force on the parts. The force on the third side is aimed at stretching the structure, so a steel tie can be used instead of a wooden part. The connection of the lower ends of the parts can be assembled in various ways (Fig. 4), by inserting beams into a puff, using wooden elements or metal brackets.
- Reinforced structure (Fig. 5) - a gable rafter system used for roofing of large industrial buildings with a distance between walls of more than 6 m. This system is not suitable for use in small residential buildings. A design feature is the distribution of the puff weight on the skate. Since it is almost impossible to find solid lumber of the required length (6 m or more), the puff is made from segments. The connection of all elements is carried out by a straight or oblique inset. The central part is called the headstock. The connection of the headstock with a tightening is performed by a collet twist with the possibility of adjusting the tension.
- The device of an arch with a tightening in the upper part of the rafters (Fig. 6) is used for equipment in the attic space of the attic. At the same time, the tensile force in the rafter beams increases. The lower ends of the beams are attached to the Mauerlat bars. The fastening should limit the movement of the beams to the sides along the beam, but allow sliding across. This ensures uniform load distribution and stability of the entire system. Rafter beams should form an overhang.
Many variants of system design have been developed hanging type. Most are used for relatively small sizes buildings without load-bearing structures inside buildings. For larger buildings, a layered rafter system should be used.
Loading...