A number of interior styles, including those related to minimalism, allow or even welcome open elements of rafter systems into the attic space. These elements make the ceiling architecture more interesting and decorate the interior.
If the owners decide to leave the rafters and beams open, then at the design stage they must decide how much these elements should protrude towards the room. The fact is that their cross-section, which the designer must indicate in the project, will depend on this.
Dimensions cross section rafters cannot be arbitrary. On the one hand, we are talking about the load-bearing capacity of the elements, and on the other, about the possibility of laying thermal insulation of sufficient thickness between them. If desired, of course, you can increase the rafters with inside, but this approach is, in principle, not the most rational.
The attic roof is a standard building envelope. Building regulations for such a structure impose corresponding requirements for resistance to heat transfer - R of the attic roof must be at least 4.95 m² C/W. In this regard, the thermal insulation layer in the structure roofing pie should be at least 20-22 cm. This is slightly greater than the cross-sectional height of conventional rafters, which is 18-20 cm. That missing part of the thermal insulation is either not provided at all, or is laid between the frame slats, which are installed to fasten the plasterboard sheathing. Both solutions from the point of view of engineering and economic feasibility, as already mentioned, is not rational. It is necessary to look for other solutions.
Wooden rafters
The disadvantage of solid wood rafters, which are intended to be left visible as decoration on the attic ceiling, is that they do not have sufficient cross-sectional height. Standard wooden rafters allow only a few centimeters to be visible, since maximum height The cross-section of finished lumber is limited to 24 cm. Thicker rafters must be specially ordered, which will sharply increase their cost.
If the owners are satisfied with the slightly protruding part of the rafters, then they can choose maximum size solid wood products. Most often, rafters are made of pine or spruce. When used in the interior, such materials are planed on four sides and also sanded. Sanded wood has higher fire resistance. The absence of roughness and notches does not allow the flame to easily “catch.” Wood treated in this way is also less susceptible to insect damage, because it is more difficult for the latter to penetrate through smoothly polished surfaces.
For open ceiling beams You cannot use lumber impregnated with green impregnation. Impregnation penetrates deeply into the wood and planing cannot correct this. It is unlikely that green beams will suit their appearance; therefore, it is better to buy wood of a natural color, treated with colorless bioprotective preparations.
Laminated timber rafters
Glued laminated wood is made from individual lamellas of small cross-section, due to which products made from it can have a large cross-section and unlimited length. Today, glued beams with a cross-sectional height of up to 60 mm are available. However, laminated wood is much more expensive than solid wood. Every additional centimeter of cross-section is reflected in its price.
The lamellas from which the beams are glued can have a thickness from 18 to 45 mm. They are firmly bonded to each other with melamine resin or resorcinol glue. White glue lines indicate the use of melamine resin, and if dark, then resorcinol glue was used. The material of the slats is pine, spruce or larch wood. There are also imported glued products made from exotic species, which have high strength and durability.
The length of the lamellas is increased “by the mustache”, i.e. using a wedge connection. There are tinted and varnished products on sale.
In terms of strength and other performance characteristics, laminated laminated beams are superior to solid wood beams of the same section. In particular, in terms of strength, they are superior to products made from solid coniferous wood 2 times. The undoubted advantage of laminated wood is the unlimited length of the products, which allows you to design a rafter structure without support posts.
I-beam rafters
The I-beam has a cross-section in the form of two oppositely connected letters T. This type of profile gives the product rigidity in two directions, with a minimum cross-sectional area. Became popular today I-beams made of solid or laminated wood with an intermediate support made of OSB. Along with them there are beams made according to the same principle, but entirely from laminated wood.
The advantage of I-beams is their low weight. Such beams are easy to install. But in our case they are not very suitable, since their end part is small in height - 38-48 mm. Accordingly, it is precisely this visible protrusion of the beam that can be counted on, and no more. In addition, I-beams in the rafter structure, due to their load-bearing parameters, are installed in smaller increments than usual - namely, every 50-70 cm.
I-beams for floors have a wider beam at the end (89 mm). This makes them more visible on the ceiling. Due to this, when choosing an I-beam option, such beams are more in demand.
Thermally insulated footrails
You can get a large projection of rafters into the attic space by placing thermal insulation not directly between them, but on top of them. This task can be overcome only with the help of rigid slab insulation with low water absorption, for example, such as extruded polystyrene foam or foam glass. Laying thermal insulation on top of the rafters also significantly increases the resistance of the attic roof structure by creating a continuous thermal insulation layer where the rafters are not cold bridges. In this case, a continuous hard flooring is built on top of the rafters, which is covered with a layer of roofing felt or roofing film.
Insulation boards are laid on top of the flooring prepared in the described manner. They are attached to the rafters using counter slats and long nails that pierce the insulation right through. It is important to carry out the fastening in such a way that the counter battens cannot move down under the weight of the roof. To do this, you can drive the nails at an angle of about 67° relative to the slope; or screw the eaves overhang beam to the rafters, thus insuring the counter-battens.
For insulation over rafters, it is advisable to use slabs with profiled edges, which make the joints tighter.
Imitation of rafters
There are several ways to simulate open rafters, while the real elements of the rafter structure remain completely hidden in the structure of the roofing pie. Imitation can be achieved in several ways. The first involves nailing bars of the required cross-section to the rafters, possibly even exceeding the width of the actual beam. The protruding part can be made of more expensive and noble wood. This solution is primarily suitable for roof structures made of I-beam rafters. The false beams are glued to the rafters, since it is impossible to fasten them with through fasteners - the heads of the screws will be visible. Disguising these caps is quite problematic. If you cover them with wood putty and cover them with stain on top, the attachment points will most likely darken. The rhythmicity and symmetry of such dark dots will in no way make the imitation truthful.
In the second case, polyurethane imitation beams are used, which look almost identical to natural ones. Their only drawback is their high price. Otherwise, polyurethane beams in the form of boxes are very convenient interior solution attic ceiling slopes. These boxes are quite lightweight. They can be attached directly to the attic cladding using pre-nailed wooden blocks, or they can simply be glued. In the latter case, it is necessary to press the polyurethane beams tightly while the glue sets, for which you can use supports. When glued, wooden false beams sit on the tenon, so they do not need support.
Polyurethane imitations with various types of finishes are available on sale today. The standard lengths of polyurethane beams are 3 m and 4.5 m, and the cross-sectional dimensions are 120x60 or 160x100 m.
False beams can also be made in the form wooden boxes U-shaped. However, their price can exceed false beams made of solid wood, so the advisability of hollow wooden boxes is due only to their relatively low weight.
In order for a constructed building to last for more than one year, it needs both reliable foundation, as well as a strong roofing system that can withstand the vicissitudes of the weather. The roof must withstand heavy loads with dignity: heavy snowfalls, sharp gusts of wind, heavy downpours. The roof truss system is best suited for this.
Roof trusses and its types
Rafter system- the base of the roof, which places emphasis on the load-bearing elements of the building and also serves as a frame for various types roofing materials: insulation, waterproofing, various coatings.
The dimensions and design of the rafters depend on:
- purchased material;
- size of the building;
- house dimensions;
- building materials for rafters;
- individual customer preferences;
- roof loads relevant for a particular region.
The rafter system has:
- sheathing - beams laid perpendicularly on the rafter legs;
- ties that absorb tensile forces;
- wooden racks located in a vertical position;
- mauerlat - a beam, the installation of which is carried out along the wall, the rafters rest on it;
- rafter legs are a kind of wooden beams that bear the main load of the roof.
Each of the above factors is very important, since it is necessary to understand what type of rafter system will be optimally suited for a particular situation.
When it comes to low-rise buildings, then wood structures are the most common. In many cases, three types of roof trusses are used: hanging rafters, layered rafters and mixed system rafters
Characteristics of hanging rafters
Hanging rafters- this is the most elementary type of rafter systems, their characteristics:
If the roof of the house has a complex structure, the types of rafters can be alternated. For example, if there are supports or a middle main wall, layered rafters are installed, and if there are no such elements, hanging rafters are installed.
Features of layered rafters
For a layered rafter system, the house must be additionally equipped load-bearing wall, located in the middle. Layered rafters are distinguished according to the following characteristics:
The design of the combined system is the most complex, since it includes parts of two other types of rafters - hanging and layered. It is used for mansard roof. The walls of the rooms located on the second floor are formed by vertical supports; these supports also serve as intermediate supports for the rafter beams.
The part of the rafters that connect one end of the racks functions as a crossbar for the slopes located on the side, and for the upper part of the structure they are a tie.
At the same time, the horizontal beams perform the following functions: for the upper slopes - the Mauerlat, for the side slopes - the ridge beam. To increase the strength of the roof, struts are installed that connect the side slopes and vertical posts.
The combined sling system is the most complex and time-consuming to manufacture, but these shortcomings are fully compensated by the increase in the load-bearing qualities of the roof in the absence of unnecessary supports, especially when there is a need to cover significant spans in the building.
You can increase the load-bearing qualities of the roof using a mixed rafter system Roof trusses for various roof types
When constructing a certain building, rafter systems of one type or another are necessarily used, and the type of roof will completely depend on the design of the future structure.
Rafter truss for gable roof
Gable roofing is a common roof construction for residential buildings that have no more than three floors. Preference is given to this design due to technical characteristics the inclined shape of the rafter system, and also due to the fact that installation work carried out easily and simply.
The rafter system of a gable roof includes two rectangular inclined planes. The upper part of the building from the end side resembles a triangle. The main components of a gable roof are the mauerlat and rafter legs. In order to properly distribute the load across the rafters and walls, struts, crossbars and racks are installed, thanks to which you can create a durable, rigid, elementary and lightweight structure for installing a structure for a gable roof.
A gable roof is considered the simplest roofing system; it is used for residential buildings of no more than three floors You can install sparse or solid sheathing on top of the rafters, and then attach bitumen coating, tiles or some other type of material to it. The rafters and the sheathing itself are usually made of beams or boards, which are fastened with nails, bolts or metal fasteners. Metal profiles can be used as rafters, thereby covering significant spans. There is no need to use extra racks and struts.
The installation of a rafter system for a gable roof allows you to evenly distribute the entire existing load along the perimeter of the building. The lower ends of the system focus on the Mauerlat. They are fixed with fasteners or metal brackets. By the angle of inclination of the rafter bars, you can determine at what angle the roof slopes will be inclined.
The rafter system for a gable roof allows you to evenly distribute the load from the roof along the perimeter of the building Rafter system for hip roof
When arranging a system for a hip roof, you will need to install different types of rafters:
- narozhniki (short);
- lateral;
- hip main;
- obliques (diagonal elements that form a slope in the shape of a triangle).
The rafter legs, located on the side, are made of boards, and they are mounted identically to the parts of a traditional pitched roof with a layered or hanging structure. Hip main rafters are layered parts. For splices, boards or bars are used, attached not only to the Mauerlat, but also to the diagonal beams.
To install this type of structure, the angle of inclination, as well as the cross-section of the slanting beams, are accurately calculated. The dimensions of the parts also depend on the span length.
To prevent the hip roof from deforming from heavy loads, you should accurately calculate the angle of inclination of the diagonal beams for the rafters Maintain symmetry when installing diagonal beams for rafters, otherwise the roof will deform under significant load.
Rafter system for a sloping roof
A broken roof is a structure with rafters that consist of several individual elements. Moreover, they should be located at different angles relative to the horizon. And since the lower rafter part is almost vertical, attic room The building receives additional space, thanks to which it can be used as a residential building. The installation of this type of roof is carried out during the construction of a four- or gable rafter structure.
Calculate four-slope system professionals need rafters, but gable broken roof You can do it yourself, since its installation is very simple. To do this, it is necessary to install a support frame, which should consist of purlins and racks. Horizontal parts are fixed with hanging rafters. But the supports of the sloping roof are secured to the mauerlat with the shortened legs of the rafters.
The assembly of rafters for a sloping gable roof can also be carried out by non-professionals, since the installation of such a roof is very simple "Cuckoo" in a roof truss
The so-called cuckoo on the roof is a small protrusion that is located on attic floor. There is a window here for better illumination of the attic room. The installation of the “cuckoo” is carried out carefully, while monitoring the parameters of the entire structure: depth of cut, angle of inclination and other factors. However, before this, the necessary measurements are made.
The first stage of work begins with the installation of the Mauerlat (beam with a cross-section of 10x10 cm, which is needed to support the slings). The rafter system acts as a skeleton for the roofing material. To impart rigidity to the structure, spacers are used, which are mounted between the two legs of the rafters.
After the installation of the roof truss is completed, sheathing is laid, the type of which depends on the roof covering purchased. Installation of the sheathing is done continuously or with a certain step. For it, boards, OSB and plywood sheets. In addition, the installation of roofing material must be identical throughout the entire roof.
The main difficulty when installing such a rafter system is the location of the internal corners. Snow can accumulate in these places, which means the load will increase, which is why a continuous sheathing is made.
A “cuckoo” on the roof is a small protrusion on the attic floor, under which there is an additional window. Chalet roof rafter truss
The peculiarity of this design is that the canopies and overhangs are moved outside the house. In addition, there must be rafters and roof beams extending up to three meters on the sides of the building. Each of these elements is secured with a bracket to the wall of the building in the lower part. Next, tie the edges of the beams. They serve as a support for covering the roof of the building.
But when creating large overhangs, it is necessary to install reinforced belt in parallel with the installation of studs for the Mauerlat. It is necessary to make anchors that help secure the consoles. In this case, the rafters will be perfectly fixed with anchors and, in addition, with mortises.
To carry out the side cornices, a ridge beam is made, after which beams are placed at the level of the mauerlat, which must be identical to the length of the ridge. The truss, and subsequently the building materials for the roof, rest on these structural details.
When designing a building, the angle of the chalet roof is calculated based on the characteristics of the local climate and other factors. When the slope angle is about 45°, the load from snow is not taken into account, since when this option he won't stay on the roof. At the same time, the flat roof will withstand the load from snow, but it is necessary to install a reinforced roof truss. Before installing the chalet roof, a building design is prepared, because the originality of the roof itself, as well as the long eaves and overhangs, oblige this.
A chalet-style roof is characterized by canopies placed several meters outside the house Rafter truss designed for soft roofing
Soft roofing is done different ways, however, they exist in the technological methods of its construction General characteristics. Initially, you need to prepare. When arranging a roof for a house made of foam concrete or other material, a mauerlat is first installed, then in the upper crowns of the building a cut is made for the ceiling beams in increments of up to one meter. The distance between the boards is calculated based on the type of rafter structure.
- Install individual parts of the rafter system. To completely eliminate the risk, the rafter boards are attached to the ground with screws. After the roof truss is created, it is raised to the top of the building.
- All elements of the rafters are secured to the ceiling, internal boards, jibs, and crossbars. Further, this base for the roof will become a single whole structure.
- The next stage is the sheathing, which is installed under the soft roof with small gaps or no gaps at all. Gaps of no more than 1 cm are allowed. Quite often, leveling plywood is installed on top of the boards. Its sheets are laid according to the method brickwork. The resulting joints are not aligned with the gaps between the plywood and the board.
If the length of the sheathing boards is not enough, then the joints of the parts must be located in different places. In this way, you can correctly distribute areas that have been weakened.
Self-production of the rafter system
Before the installation of the rafter system begins, the mauerlat must be secured to the longitudinal walls with anchors. Next you need to decide on the required leg section for the rafters, depending on the distance and their length. If there is a need to increase the length of the rafters, then connect them with different fasteners.
When using different insulation, you need to choose the ideal distance between rafter elements in order to reduce the number of thermal insulation scraps.
Installation of the rafter system must be done in the following order:
- A template is made according to which the truss is assembled. Take 2 boards corresponding to the length of the rafters and connect them together at just one edge with a nail.
A template for rafters called “scissors” will help you quickly assemble the entire roof rafter system - The result is a design called “scissors”. Its free edges are placed on supports at the points of contact between the rafter legs. The result should be the final angle, that is, the angle at which the roof slope will be inclined. It is fixed with several long nails and transverse boards.
- A second template is made, thanks to which the cuts are installed on the rafters. It is made from plywood.
- Special mounting cuts are cut on the rafters (a prepared template is used for these purposes) and connected at an angle of inclination of the slope. You should end up with a triangle going up the stairs to the roof. Next, it must be attached to the Mauerlat.
- Initially, two side gable rafters are installed. Their correct installation in the vertical and horizontal planes occurs due to temporary struts attached to the rafters.
For proper 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 ridge and the level of other rafters located in the gap.
- Raise and install the remaining rafters at the initially calculated distance, which should be at least 60 cm from each other.
- If a bulky rafter structure is envisaged, then it is additionally strengthened with struts, supports, and so on.
The bulky structure of the rafters is additionally strengthened with struts and supports - A ridge beam is installed on special supports, to which not only short, but also diagonal and intermediate elements of the rafters are attached.
Correct fastening ridge beam ensures the reliability of the entire rafter system
Typical components of a standard rafter system
The strength of the rafter structure depends on the ideally selected section of the boards, as well as on High Quality rafter nodes. The connection of parts for the roof structure is done according to established rules.
Main typical units in the rafter system:
- rafter support assembly on the mauerlat;
- ridge;
- unit for combining the top ties and the entire rafter system;
- securing the strut, rack, as well as rafters and beams.
After the design of the rafter system has been chosen, it is necessary to draw up a plan in which to highlight all the nodes. In each design they are made differently, since it depends on various nuances: the type of roof, its size, angle of inclination.
Rafters made from a profile pipe are a metal structure that is assembled using lattice rods. The production of such farms itself is a very labor-intensive process, but also more economical. For the manufacture of rafters they are used paired material, and the gussets are connecting elements. The structure of the rafters from profile pipes is assembled on the ground, using riveting or welding.
Thanks to such systems, any spans are blocked, but the correct calculation must be made. Provided that all welding work is done efficiently, in the future all that remains is to transfer the structural elements to the top of the building and assemble them. Load-bearing rafters made from profile pipes have many advantages, such as:
Crossbar in the rafter system
Crossbar is a fairly broad concept, but in the case of roofs it has a certain meaning. The crossbar is a horizontal beam that connects the rafters. This element prevents the roof from “expanding.” It is made of wood, reinforced concrete, and also metal - it all depends on the type of structure. And the crossbar serves to distribute the load exerted by the rafter system.
It can be fixed in various places between the legs of the slings. There is a direct pattern here - if the crossbar is fixed higher, then the timber for its installation must be selected with a large cross-section.
There are many ways to fix the crossbar to the rafter system:
- bolts;
- nuts;
- studs with washers;
- special fasteners;
- nails;
- mixed fastenings, when different types of fastenings are used in parallel.
The fastening is available with a mortise or overhead. In general, the crossbar is a design unit, as is the entire system of roof slings.
The crossbar in the rafter system is designed to strengthen the roof structure Fastening the rafter system
To ensure the reliability of the rafter system, you must first find out how they are attached to the supporting roof and ridge. If fastening is made to prevent deformation of the roof during shrinkage of the house, then the rafters are secured on top with a hinge plate or a nut and bolt, and below - sliding support.
Hanging rafters need a tighter and more reliable fastening in the ridge, so in this case you can use:
- overhead metal or wooden plates;
- cutting method;
- connection using long nails.
In the layered system, the rafter legs are not connected to each other, since they are attached to the ridge girder.
The rafters are attached to the mauerlat using the cutting method, which is made in the rafter leg. Thanks to this fastening method, the roof support will not weaken. Cutting is also done when installing rafters on floor beams. In this case, a cut is also made in the support beam.
Video: how to make rafters with your own hands
Thus, a perfectly matched rafter system and their design characteristics will help create the basis for a reliable roof for your home.
When designing any residential building, architects Special attention pay attention to the roof, since it performs not one, but several functions at once, depending on its design features. It must be said that not all future homeowners are satisfied with an ordinary gable roof, although it can be called the most reliable, since it has only two pitched planes and one joint between them. Many people are more attracted to complex designs, which add special attractiveness and originality to the building. Other, more practical homeowners prefer attic structures, which can simultaneously serve as a roof and a second floor.
The basis of any roof is an individual rafter system, which has its own design features. It will be much easier to choose the right roof frame if you figure out which ones in advance. types and diagrams of rafter systems used in construction practice. After receiving such information, it will become more clear how difficult such structures are to install. This is especially important to know if you plan to build the roof frame yourself.
Main functional tasks of rafter systems
When arranging pitched roof structures, the rafter system serves as a frame for covering and for holding the materials of the “roofing pie”. With proper installation frame structure will be created the necessary conditions for correct and non-insulated types of roofs, protecting walls and inner space houses from various atmospheric influences.
The roof structure is also always the final architectural element exterior design of the building, supporting its stylistic direction with its appearance. However, the design features of rafter systems must first of all meet the strength and reliability requirements that the roof must meet, and only then the aesthetic criteria.
The frame of the rafter system forms the configuration and angle of inclination of the roof. These parameters largely depend on natural factors characteristic of a particular region, as well as on the desires and capabilities of the homeowner:
- Precipitation in different periods of the year.
- The direction and average speed of the wind in the area where the building will be erected.
- Plans for the use of space under the roof - arranging residential or non-residential premises, or using it only as an air gap for thermal insulation of the rooms below.
- Type of planned roofing material.
- Financial capabilities of the homeowner.
Atmospheric precipitation and the strength of wind currents place a very sensitive load on the roof structure. For example, in regions with heavy snowfall, you should not choose a rafter system with a small slope angle, since snow masses will linger on their surface, which can lead to deformation of the frame or roofing or to leaks.
If the area where the construction will take place is famous for its winds, then it is better to choose a structure with a slight slope of the slope so that sudden gusts that occur do not tear off individual elements of the roof and roofing.
Main elements of roof structure
Parts and components of rafter systems
Depending on the type of rafter system chosen, the structural elements used can vary significantly, however, there are parts that are present in both simple and complex roof systems.
The main elements of a pitched roof rafter system include:
- Rafter legs that form the roof slopes.
- - a wooden beam fixed to the walls of the house and used to fix the lower part of the rafter legs on it.
- A ridge is the junction of the frames of two slopes. It is usually the highest horizontal line of the roof and serves as the support to which the rafters are anchored. The ridge can be formed by rafters fastened together at a certain angle or fixed on a ridge board (purlin).
- Sheathing is slats or beams mounted on rafters at a certain pitch and serving as the basis for laying the selected roofing material.
- Supporting elements, which include beams, purlins, racks, struts, ties and other parts, serve to increase the rigidity of the rafter legs, support the ridge, and connect individual parts into an overall structure.
In addition to the mentioned design details, it may also include other elements, the functions of which are aimed at strengthening the system and optimally distributing roof loads on the walls of the building.
The rafter system is divided into several categories depending on different features of its design.
Attic space
Before we look at different types roofs, it is worth understanding what the attic space can be, since many owners successfully use it as utility and full-fledged residential premises.
design pitched roofs can be divided into non-attic and attic. The first option is called this way because the space under the roof has a small height and is used only as an air layer insulating the building on top. Such systems usually include or have several slopes, but located at a very slight angle.
An attic structure that has a sufficiently high ridge height can be used in different ways, be insulated and not insulated. Such options include an attic or gable option. If you choose a roof with a high ridge, then it is imperative to take into account the wind loads in the region where the house is built.
Slope slope
To determine the optimal slope of the roof slopes of a future residential building, first of all you need to take a closer look at the low-rise neighboring houses that have already been built. If they have been standing for more than one year and can withstand wind loads, then their design can safely be taken as a basis. In the same case, when the owners set a goal to create an exclusive original project, unlike the neighboring buildings, it is necessary to familiarize yourself with the design and operational features of various rafter systems and make the appropriate calculations.
It should be taken into account that the change in the tangent and normal values of the wind force depends on how large the slope of the roof slopes is - the steeper the angle of inclination, the greater the importance of normal forces and the less tangent forces. If the roof is flat, then the structure is more affected by the tangential wind load, since the lifting force increases on the leeward side and decreases on the windward side.
Winter snow load should also be taken into account when designing the roof. Usually this factor is considered in conjunction with the wind load, since on the windward side the snow load will be much lower than on the leeward slope. In addition, there are places on the slopes where snow will certainly accumulate, putting a large load on this area, so it should be reinforced with additional rafters.
The slope of roof slopes can vary from 10 to 60 degrees, and it should be chosen not only taking into account the consolidated external load, but also depending on the roofing that is planned to be used. This factor is taken into account because roofing materials differ in their weight; to secure them, a different number of elements of the rafter system is required, which means that the load on the walls of the house will also vary, and how large it will be also depends on the angle of the roof. Of no small importance are the characteristics of each coating in terms of resistance to moisture penetration - many roofing materials in any case require one or another slope to ensure the free drainage of storm water or melting snow. In addition, when choosing a roof slope, you need to think in advance about how the cleaning process will be carried out and repair work on the roof.
When planning a particular angle of the roof slopes, you need to know that the fewer joints between the sheets of roofing, and the more airtight they are, the less you can make the slope of the slope, of course, if you are not planning to arrange a residential or utility room in the attic space.
If a material consisting of small elements is used to cover the roof, for example, ceramic tiles, then the slope of the slopes must be made steep enough so that water never lingers on the surface.
Considering the weight of the roofing material, you need to know that the heavier the covering, the larger the angle of the slopes should be, since in this case the load will be correctly distributed over the rafter system and load-bearing walls.
Can be used to cover the roof following materials: or profile sheet, galvanized steel, corrugated asbestos concrete and bitumen-fiber sheets, cement and ceramic tiles, roofing felt, soft roof and other roofing materials. The illustration below shows the permissible slope angles for various types roofing coverings.
Basic designs of rafter systems
First of all, it is worth considering the basic types of rafter systems relative to the location of the walls of the house, which are used in all roof structures. Basic options are divided into layered, hanging, and combined, that is, including elements of both the first and second types of systems in its design.
fastenings for rafters
Layered system
In buildings where internal load-bearing walls are provided, a layered rafter system is often installed. It is much easier to install than a hanging one, since the internal load-bearing walls provide reliable support for its elements, and in addition, this structure will require less materials.
For rafters in this system, the defining reference point is the ridge board, on which they are fixed. The non-thrust type of layered system can be arranged in three options:
- In the first option, the upper side of the rafters is fixed on a ridge support, called a sliding one, and their lower side is fixed by cutting to the mauerlat. Additionally, the rafters in the lower part are fixed to the wall using wire or staples.
- In the second case, the rafters in the upper part are cut at a certain angle and connected to each other using special metal plates.
The lower edge of the rafter legs is attached to the Mauerlat with movable fasteners.
- In the third option, the rafters are rigidly fastened in the upper part with bars or treated boards located horizontally, parallel to each other on both sides of rafters connected at an angle, and a ridge girder is clamped between them.
In the lower part, sliding fasteners are used to secure the rafters, just as in the previous case.
It is necessary to explain why sliding fasteners are often used to secure rafters to the mauerlat. The fact is that they are able to relieve load-bearing walls from excessive stress, since the rafters are not rigidly fixed, and when the structure shrinks, they are able to move without deforming the overall structure of the roofing system.
This type of fastening is used only in layered systems, which also distinguishes them from the hanging version.
However, in some cases, for layered rafters, a spacer system is used, in which the lower end of the rafters is rigidly fixed to the Mauerlat, and to relieve the load from the walls, tie-downs and struts are built into the structure. This option is called complex, as it includes elements of a layered and hanging system.
As a rule, softwood lumber is used.
For various elements and parts of a wooden rafter system, wood of a certain type and grade is used. When using lumber in a rafter-beam system, the following properties and indicators of wood must be taken into account: bending strength, compression, chipping, wood density and moisture content.
Wooden rafter structures must necessarily comply with the special degree of fire resistance of the room. They must be treated with special fire retardants and...
There is a huge variety of options and elements for wooden construction. truss structures. There are the following types of rafter structures: layered or hanging rafters, combined, with a tie, etc. The most popular rafter structures are layered and hanging.
To avoid sagging of the entire structure, a horizontal tie is attached to the lower end of the beam using strip steel clamps to support the beams of the entire attic floor. If the span is up to 12 m, then struts are introduced into the rafter structure, which reduce the estimated length of all rafter legs.
Hanging wooden rafters work in both compression and bending.
Below we consider the types of rafter structures:
- ordinary hanging rafters
- double hanging rafters
It is not uncommon to increase the entire area of the attic space in a system of wooden hanging rafters without using tie-downs, but using struts.
Roof Mauerlat In this case, the rafter legs are cut into the Mauerlat itself. The lower plane should lie on the wall, and in the upper one you need to make certain cuts for correct connection with rafter legs.
All struts rest against the end of the wooden one. In this case, the loads that would be compensated by the tightening are directly transferred to all walls. As a result, this solution for a wooden rafter system is only possible if there is a special massive structure.
Hanging rafters are parts and elements of rafter structures that are located in one vertical plane and are connected to each other using notches, bolts, nails, clamps and staples.
There is a combined rafter system - this is the installation of both a layered and a hanging rafter structure, which alternate in turns. Where there are no intermediate supports, hanging rafter systems are used, and where they are present, layered rafter systems are used.
Rafters with tie
Used for spans up to 15 m. Spans of this length require certain intermediate struts, i.e. in special puffs. They are mounted at the height of the building between two rafters and tied together. And longitudinal struts will prevent lateral bending.
Tightening the roof rafters All structures with retaining wooden beams must be assembled in the form of rafter structures reinforced with special supports, which will rest on transverse beams and all load-bearing walls, as well as in the form of truss systems. The concept of a truss is a structural element similar to an open triangular rod system, which is attached to the main truss load-bearing structures.
The structural rigidity of this roof is provided by a longitudinal strut or strut. The use of struts reduces the overall load on the entire structure. Vertical struts are usually attached to either racks using notches, trunnions, or steel plates.
Truss hanging timber trusses systems
Sprengel The entire load from the rafter legs goes to the racks, which transfer it further to the load-bearing main ones. With this design, the load will be distributed between all load-bearing walls. The racks are mounted at the ends of the main load-bearing walls. The lower ends of all racks are secured using hanging pins.
Truss beams are made from solid solid wood or laminated boards. Usually they small height. Good and high-quality load-bearing capacity of truss beams is achieved using a truss system and wooden beams supporting it.
Shrengel beams can cover huge spans. Sometimes they are equipped with steel belts.
Complex rafter system designs
They are produced according to the type of roof trusses. Lattice trusses are divided into types according to the shape of their openings: triangular, trapezoidal or parallel belts. Typically, lattice trusses are made symmetrical, but other options are possible, for example,. A common lattice truss includes top and bottom chords, posts and braces. 
Reliable and high-quality connection of carriers wooden structures with central supports in one common system called a frame. The racks and beams connected into the frame are necessarily fastened or included in each other. Today there are two main types of frames - double-hinge and three-hinge. Double-hinged frames are equipped with a crossbar that runs across the entire width of the finished frame. These frames are best suited for structures with a small angle of inclination. Tri-hinged frames consist of two equal halves that support each other at the ridge of the roof. Triple-hinged frames are used where more significant angle tilt
Trust the calculations of rafter structures and the final selection of their elements and parts to specialists. Huge loads are applied. In addition to its own weight, it is affected by wind loads, heavy rains, hail, snow and ice. The roof quite often undergoes various
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The roof is of great importance for the integrity of the entire house. Therefore, many are interested in how to properly assemble a rafter system so that it is reliable and does not have to be repaired in the near future. There are many types of roofs, some of them can be seen in the photo, but the most popular are lean-to and gable structures. Let's figure out how to make a rafter system correctly.
Types of roofs
Before moving on to how to make a rafter system, you need to understand what the common types of roofs are.
A pitched roof is the simplest; even a person who does not have much experience in construction can cope with its creation. However, this type of roofing is used mainly in the construction of commercial buildings. For residential buildings Usually they make gable or mansard (broken) roofs. These structures are more complex, but you can easily handle them on your own if you know how to make gable roof rafters and follow all the recommendations of specialists (read: "").
The most reliable roofs are hip roofs; they can withstand even huge loads. They are recommended to be done in regions where there is a lot of snow and strong winds often blow. But their design is very complex, so it is better to entrust their construction to professionals.
A hipped (hipped) roof is used in the construction of square buildings; in its design, it is a type of hip roof.
The most complex roof is a cross roof. During its construction, complex structural elements are used - valleys (grooves). These diagonal auxiliary rafters are installed as additional elements. During construction such complex roof rush is unacceptable. The bulk of the snow accumulates in the area of the valleys, and the reliability of the roof depends on how to make rafters in these places.
Each type of roof consists of rafters and roofing. The rafters are the load-bearing part of the roof, and the roof surface is the enclosing part.
Types of rafters
Before you lay the rafters, you need to know about them design features and decide on the installation option.
There are two types of rafters: layered and hanging .
Hanging rafters - These are inclined beams installed on supports with different heights. The support can be the external walls of the house (in the case of a pitched roof) or both internal and external walls (in the case of a gable roof). The rafter legs do not have to be laid in the same plane opposite to the slopes. They can be mounted alternately on the ridge girder. Alternate laying of rafters in the ridge area makes it possible to create a roof truss. For this purpose, all parts are connected together into a single rigid structure.
Materials for rafters
As for rafters made from boards, they are not heavy and are easy to install. You can easily work with this material yourself, without resorting to outside help. Many experts do not advise making connections with nails - it is better to use self-tapping screws. If the work will be carried out using nails, do not forget about linings and liners.
As for how to build a rafter system, it is better to use notches to connect the racks to the purlin or beam.
Installation of the rafter system with your own hands, details in the video:
Options for connecting the rafter system
The rafter system can be connected in three ways:
- struts;
- stands;
- simultaneously struts and racks.
How to properly make rafters depends on the span between the outer walls. A 10x10 centimeter beam is used to create a ridge girder. The bench and mauerlat can be made from logs by cutting them into two edges, or by taking a 10x10 centimeter beam.
When designing a ridge assembly, it is necessary to nail special clamps made of steel strip to the mauerlat and purlin with large nails, taking into account. You don’t have to use steel clamps, but then you need twists made of thick wire with a diameter of 6 millimeters.
Regarding how to make a brick or stone house, you need to lay a mauerlat on the masonry. To securely fasten it, it is recommended to place it under each rafter leg a piece of log or beam about 50 centimeters. Then they are attached using clamps to metal hooks, which were previously installed 30 centimeters below the Mauerlat.
Many people have a question about how to make rafters for the roof wooden houses. Rafters in wooden buildings are laid on the upper crown of the wall. A plank roof truss can be created using a crossbar or with spans (6-8 centimeters). Its structural elements are arranged as follows. They make a single tightening using boards, the thickness of which is equal to the thickness of the rafters. For double tightening, thinner boards (from 40 millimeters thick) are used. For the crossbar and linings, 30 mm parts are used.
How to determine the cross-section of rafters
Before laying the rafters correctly, you need to decide on their cross-section.
This parameter depends on:
- span dimensions;
- expected load (wind force, weight of snow cover and roofing material);
- pitch and installation angle of the rafters (roof slope).
There is a dependence of the cross-section of the rafters on the length of the rafter leg.
It is expressed as follows:
- with a step of 300 centimeters, beams with a section of 10x12 centimeters or boards with a section of 6x14, 8x14 or 4x18 centimeters are used;
- with a step of 400 centimeters, beams with a section of 10x16 centimeters or boards with a section of 6x20, 8x20 centimeters are used;
- with a step of 500 centimeters, beams with a section of 10x20 centimeters or boards with a section of 8x22 centimeters are used.
").Roof covering must be selected taking into account the roof slope. Also, the choice of roofing material depends on financial capabilities. The greater the roof slope, the more funds will be required to create the roof - this is due to the increased consumption of materials. However, steep roofs drain rainwater and snow better, so they are more reliable and will not require repairs longer. But considering huge selection roofing materials on the market, there will be no difficulties with this.
Creating a rafter system for a bathhouse
As for how to make rafters for a bathhouse, it is better to choose a gable roof - then the building will have attic space, which can be used to store brooms and other bath accessories (read: ""). Thus, it is advisable to create a rafter system for a gable roof, it is simpler and more practical.
