Roof in section. Do-it-yourself gable roof truss system: an overview of hanging and layered structures
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When building private households, the projects of houses with a gable roof are considered the most popular, they can be seen in the photo. The design of such roofs is simple compared to hip roofs (they are also called hip roofs). To create a gable roof frame, wooden beams and boards are used, not big weight which allows you to build a truss system with your own hands.
Elements of gable roofs
The design of a gable roof includes the following elements:
- rafters . They consist of inclined struts and vertically arranged racks;
- rafter leg . For its manufacture, boards with a section of 100x150 or 50x150 millimeters are needed. With the help of rafter legs, a triangular contour of a gable roof is formed. The loads resulting from weather conditions and the weight of the roofing are transferred by the rafter legs to the Mauerlat, and that one to bearing walls buildings. When installing a gable roof at home, the installation step of the rafter legs should be at least 60 centimeters, and a maximum of 120 centimeters. The heavier the roofing, the more often they should be installed;
- struts . Such an element from trimming the board is mounted at a certain angle and thereby transfers the load to the load-bearing elements down from the rafter legs. Rafters, several struts and tightening together are the components of the truss truss, which withstands loads and transfers them in the presence of wide spans to the walls;
- racks
. They are vertical rafter elements that transfer the load from the roof ridge to the load-bearing internal walls of buildings. They are made from a bar with a section of 150x150 or 100x100 millimeters;
- Mauerlat . That's what they call wooden beam, which is installed and fixed on load-bearing walls on threaded rods or on anchors built into the surface. necessary to transfer loads from rafter legs to load-bearing walls. As a manufacturing material, a bar made of coniferous lumber and having a square section measuring 150x150 or 100x100 millimeters is used. Mauerlat beams located on opposite walls should be parallel so that the dimensions of the rafter legs are the same length;
- skate . This horizontally located element is necessary for connecting the slopes in their upper part. It is formed by connecting the rafter legs at the top point when a gable roof is being installed;
- filly . They are used if the length of the rafter legs is not enough to create an overhang on the roof. they are part of a board that has a smaller section than the boards used in the manufacture of rafter legs. The installation of a gable roof can be greatly facilitated if this element is used, since then legs of a shorter length are made for the rafter structure;
- sill . It is a horizontally fixed beam with a section of 150x150 or 100x100 millimeters. It is located on the inner load-bearing wall and its functions include the distribution of loads from the roof racks after;
- puff. This is one of the elements of the hanging truss structure, which with rafter legs forms geometric figure- a triangle - and thus helps them stay in place, and not disperse to the sides;
- eaves
. It is necessary to protect the walls from getting wet as a result of rainfall, its outer edge must protrude at least 40 centimeters;
- crate . The device of a gable roof involves the installation of roofing material, for its installation it is necessary to make a crate. To do this, bars or slats are attached to the rafter legs perpendicular to their direction. Due to the presence of the crate, the load from natural phenomena and the own weight of the roof is evenly distributed on the rafter legs. Also, the crate, which can be solid or sparse, fastens the legs of the rafters into a single one. For a soft roof, for example, from bituminous tiles, this element is made from sheets of moisture-resistant plywood.
The roof of the house is created using lumber from coniferous wood, and so that they do not become unusable due to decay during operation, before building a gable roof, they are first treated with antiseptic compounds.
Rafter systems: their types and differences
Rafter systems are of two types: hanging and layered.
Hanging rafters, together with floor beams, are used as puffs to construct an attic when a gable roof of a house is being built with your own hands (read: ""). In addition to the lower puff, an upper puff is also required at a distance of at least 50 centimeters from the ridge. Hanging truss systems are created when the distance between two outer walls is no more than 10 meters, and there is no internal load-bearing wall dividing into two halves inner space building.
Laminated rafters are installed when there is a support beam that transfers the weight of the roof from the ridge to the load-bearing wall located in the middle between the outer walls of the house. If instead of a bearing inner wall there are columns, different types of rafters alternate. Layered rafters will rest on the columns, and they will be mounted between the columns.
Installation of gable roof rafters, detailed video:
Features of creating a gable roof
For competent construction, drawings of a gable roof are used and project documentation, which indicates all its dimensions (more details: "").
When the walls of the house are built of logs or timber, the upper timber performs the function of the Mauerlat. But, if the walls of the building are made of brick, for attaching the Mauerlat to the supporting base before the gable or hipped roof, at least 10 mm metal threaded rods are mounted in the masonry and bolts with washers are used. When performing, an interval of 1-1.5 meters is observed between adjacent fasteners. To avoid wetting the walls, waterproofing is laid from two layers of roofing material.
Kinds of two pitched roofs varied, but in any case, the slope of the slopes on them should be 15-20 degrees in areas with strong winds, and where there is a lot of precipitation, 35-40 degrees, then snow and water will quickly roll off the roof surface. These nuances must be taken into account even before.
When layered rafters are used, first of all, a bed is installed, and supports are mounted on it, on which a ridge beam is placed. To fix the structure, jibs are used. Then, the rafter legs are mounted on the ridge beam, while their length should be slightly longer than necessary, so that after twisting the two rafters together, the protruding ends can be cut off. The use of this technology can significantly speed up the construction of a gable roof.
After the installation of the rafter system is completed, the gables and the overhang are sewn up and the installation of the roofing begins. To purchase material, you need to know how to calculate the area of \u200b\u200ba gable roof and thus not be mistaken with its quantity. To do this, determine the area of \u200b\u200beach of the two slopes by multiplying its length (height) by the width (length of the ridge). Note that it is very important to initially correctly calculate .
truss system gable roof considered one of the simplest in purely constructive terms. It consists of only a few elements, the number of which decreases or increases due to the size of the roof itself. But with seeming simplicity, the process of erecting a gable roof itself requires knowledge of some of the nuances that affect the quality of the final result.
Rafter system for a gable roof Source tues.ru
What is a gable roof
From the name it becomes clear that the roof structure is two slopes that have a rectangular shape in the plane. More often, the slopes have the same dimensions, but there are so-called asymmetric designs in which the slopes differ in size from each other.
In this case, the slopes are set to each other at a certain angle, which is called the slope. The line of contact is the ridge beam, which is part of the truss system. In a simple way, it is called a skate, and it is highest point roofs.
The side planes formed by the slopes are called gables. They have triangular shape. After the construction of the roof, the sidewalls are lined with sheet or panel materials: plywood, OSB, even boards and more.
What is a gable roof truss system
The basis of the structures of the slopes are rafter legs, they are also rafters. They are made either from lumber (beams, boards), or from a steel profile (corner, channel). In private housing construction, wood is used. It is easier to work with, plus lumber is cheaper.
The device of the gable roof truss system is not only rafters. In addition to them, there are several other mandatory elements. All items in the photo below. gable roof shown. Let's designate them.
Each of the elements of the roof has its own purpose. Source lestorg32.ru
Elements of the gable roof truss system
Mauerlat. In fact, this is a beam on which the rafters rest. Its purpose is to evenly distribute the load from the rafters on the walls of the house. If the Mauerlat is not used, then the rafters will put pressure on the walls pointwise, that is, large stresses will arise at the installation sites, which will lead to cracking of the walls.
rafters installed at an angle.
Skate, he is a ridge beam or run. Its task is to form a place for joining the rafter legs. A ridge beam is an optional element of a gable roof. There are designs in which it is not installed. But more on that below.
Puffs. Not always used, but only for hanging rafters ah or if the truss system is installed on a wide house.
floor beams that form the ceiling in the room and the floor in the attic.
One of the floor beams, which is called lying down. It additionally functions as a base for the support posts that support the rafters. Not always used.
Support legs, they are grandmas supporting the rafter legs. They are installed only if the span of the house is at least 6 m.
Struts, they are also diagonal props. They are used only if the support posts cannot ensure the overall reliability of the truss system.
There is another element that is clearly visible in the photo below. These are support posts for the ridge run. They are installed if the design of the truss system is heavy. That is, the entire structure is assembled under heavy roofing material, for example, under ceramic tiles.
Sloped rafters with support posts under the ridge run Source seaside-home.ru
You might be interested! A warm roof is an important detail in the construction of an energy-efficient home. From the article at the following link you can find out.
Types of rafters
The roof truss system (gable) can be assembled from layered or hanging rafters.
Layered
They got their name because the lower ends rest on the walls of the house, the upper ends on the ridge run. In this case, the truss elements are subjected to loads that bend them. The design is reliable, durable, with a large bearing capacity.
The photo above just shows the rafter system of a layered view. It is clearly seen that the legs rest in the upper part on the skate. In this case, there are two types of fastening of the rafters themselves in the upper part:
fastening is made to the ridge:
fastening is made between each other with an emphasis on the ridge (photo above).
hanging
It must be immediately noted that this species The rafter system can be used if the distance between the walls of the house does not exceed 12 m. Because the rafters abut the lower ends against the walls, and the upper ends only between themselves (there is no ridge run in the structure). Hence the low bearing capacity with a large expansion.
Hanging rafters for the roof have one purely design flaw - a large support load on the walls of the house. To reduce it, puffs are installed between the legs to form a rigid triangle. Often, the functions of the puffs are performed by the load-bearing floor beams.
If necessary, strengthen the hanging rafters, install racks and struts under them.
Hanging rafters of a gable roof Source postila.ru
Installation of a gable roof truss system
Two types of truss system determine two types of their assembly technology. Let's consider each separately.
Installation of layered rafters
There is a certain sequence for assembling layered rafters.
Two extreme support posts are installed under the ridge beam. They will not only support the beam, but also be the elements that form the gables of the building. Attach them at the bottom to the Mauerlat. At the same time, they are strictly set vertically, and the upper ends are in the same horizontal plane. To do this, a strong thread is pulled between the racks, the level is checked for horizontalness. If there are deviations, then one of the supports (low) is raised using wooden supports.
Intermediate support posts are mounted along a horizontally stretched thread in increments of 2-2.5 m. To prevent the beams of the racks from moving, they are supported with temporary fasteners: props or puffs.
A ridge beam is laid on the racks, which is attached to them.
Produced in pairs installation of gable roof rafters. Installation can be started from either side. Fastening is immediately carried out to the Mauerlat and to the ridge. The main thing is to maintain the distance between the legs, which is determined depending on the severity and bearing capacity of the roofing material. Usually this parameter is indicated in the project of the house.
If necessary, intermediate support posts and struts are mounted.
Installing rafters on a ridge along a stretched thread Source kbumb.ru
Installation of hanging rafters
The technology for installing hanging rafters is different. To do this, the entire structure, assembled from two rafters and puffs, is assembled on the ground. That is, roof trusses are prepared in the required quantity, which then rise to the roof. Sometimes craftsmen assemble trusses on the roof. Collected one - installed, collect the next.
It should be noted that such farms have a significant mass. Lifting them manually is difficult and dangerous, so they use the services of a crane. And this increases the cost of construction.
Hanging trusses assembled on the ground Source moydom-irk.ru
The most difficult thing is to set farms. All of them are installed at the installation site with a planned step, where they are temporarily fixed with jibs and props. Then a thread is pulled between the extreme farms. It must be set so that, firstly, it is stretched strictly along the horizon, and secondly, according to a design that is higher than the rest.
It remains only to raise the truss structures, which turned out to be below the stretched level. And the last - the installation of the crate, which will secure all the trusses into one truss system. Please note that at the bottom of the rafters will be fixed to the Mauerlat.
You may be interested! When the installation of the truss system is completed, the turn of roofing comes. From the article at the following link you can find out.
Rafter calculation
length of rafter legs;
the step of their installation;
section of the lumber used.
Everything is simple with the length, for this you will have to use the Pythagorean theorem, which is based on the formula: c 2 \u003d a 2 + b 2, where c is the hypotenuse of the triangle (this is the rafters), a and b are the legs. The latter are the height of the roof and half the width of the house. All parameters can be easily measured.
The length of the rafter is l 2 + H 2 Source remontik.org
It is more difficult with the installation step, because a lot will depend on the mass of the roofing material and the loads from natural precipitation. The larger both loads, the smaller the installation step. But, as practice shows, this parameter varies from 60 cm to 2 m. The latter indicator is used if corrugated board with large corrugation parameters, for example, H75, is used as a roofing material.
As for the section of the rafter legs, here, as in the case of the installation step, loads are taken into account, as well as the length of the legs and their installation step. Here the dependence is as follows: the greater the load, step and length, the larger the cross section.
Video description
In the video, the installation process of the truss system:
And one moment. Rafters for a gable roof are laid at a certain angle (indicated by the letter “a” in the photo). The slope is selected with the calculation of the choice of roofing material. That is, some coatings cannot be laid on roofs if the angle of inclination is less than required. Here are some ratios:
the minimum angle of inclination of the truss system for slate is 22 °;
for corrugated board - 12 °;
for metal tiles - 14 °;
soft tiles– 15°.
The ratio of the roof slope to the type of roofing material Source arhplan.ru
On our website you can find contacts of construction companies that offer a turnkey roof design and repair service. You can directly communicate with representatives by visiting the exhibition of houses "Low-Rise Country".
Generalization on the topic
Gable roofs are traditional designs. But from the article it becomes clear that there are two truss systems that form the basis of the construction of roofs. The one that fits the size of the house is selected. As a selection criterion, the loads that put pressure on them are also taken into account. Therefore, it is important to correlate everything correctly, taking into account the nuances of construction processes.
Rafter system - strong roof frame for holding roofing and other elements.
How well the roof frame is arranged depends on the strength of the roof as a whole.
Otherwise, its functionality, the ability to protect the building from external influences and provide heat in the house may deteriorate.
Therefore, you need to correctly approach the choice of truss systems and correctly draw up a rafter plan.
And you can read how to calculate the truss system.
Depending on the purpose of the room, the dimensions of the gable roof, the device of the truss system is classified as follows: hanging system and layered.
Hanging system
Hanging rafter gable roof system is supported only by load-bearing external walls building.
Depending on the width of the span, the roof project, the installation of hanging systems has features.
For small houses
It is advisable to erect a hanging structure for buildings where the distance from one wall to the opposite does not exceed 6 meters. The frame looks like a triangle.
To strengthen bearing capacity faces of a wireframe triangle, several methods are used:
- The bases of the rafter legs at the top are fixed with overlays;
- Use bars of a larger section on the side parts;
- The bars are fixed by cutting them into the ridge element;
- The slopes for the canopy equipment are built up by cutting an opening for the frame beam in the extended boards so that they converge behind the line passing from the edge of the inner wall to the slope of the rafter.
Using these methods, it is possible to distribute the load throughout the structure.
Strengthening the frame triangle
For mansard roofs
When arranging the frame under, you should pay attention to some points:
- Mandatory installation of the Mauerlat, on which the frame beam is installed by cutting;
- Installation of a crossbar - the basis for a ceiling canopy of a floor. The most effective mounting option is to cut the crossbar into the rafter with a semi-swing;
- The length of the bevel board should be longer than the wall line;
- The cross section of the frame bars should be maximum;
- The puff should be secured with a suspension. With a long tightening, it is required to strengthen it in the center with the help of nailed boards from above and below.
CAREFULLY!
Particular attention should be paid to the fastening of the elements, since the attic is under load from the outside and inside.
In addition, the truss system of a gable roof with an attic is equipped with heaters, which increases the load.
Rafter frame for mansard roofs
For big houses
With a span of more than 6.5 meters, the installation of a hanging system requires the installation of more fasteners in order to prevent slack in the tightening, which causes its own weight.
Points to consider:
- It is advisable to make a puff from two bars by cutting, secure with metal plates;
- In the central part of the frame, a headstock should be installed;
- For a confident distribution of gravity to the headstock and rafters, it is better to attach struts, as well as other holding elements.
When installing a suspension-type system, it can sometimes do without mounting a Mauerlat and limit itself to installing boards on a film. In addition, the hanging system is distinguished by the absence of complex nodes, which facilitates the work on arranging the roof frame.
Hanging system
Layered system
The difference between a layered type structure and a hanging one is that the structure has additional support points inside the room. A prerequisite for installing a layered system is the installation of a Mauerlat.
The design of the system provides for the installation of both expansion and non-expansion frame.
Strutless frame
A non-expanding frame should be installed in houses with log walls. When installing rafters, their bases must be attached to the Mauerlat.
Options for attaching the base of the system to the Mauerlat:
- By beveling the sole of the rafter leg in such a way that its area with the Mauerlat is the same, and the cut does not exceed 0.25 cm of the height of the beam. At the same time, the rafters, without connecting to each other, are attached to the ridge element on both sides;
- By connecting with one nail the rafters at the ridge - at the top, and swivel with a flexible metal plate to the Mauerlat - at the bottom.
When attaching rafter legs without connecting them in the ridge part special attention should be paid to the accuracy of calculations.
Even with minor discrepancies in the scheme, the expansion pressure will act on the walls of the building, which can lead to the collapse of the walls.
Strutless frame
With contractions
To strengthen the structure and give it stability, fights are mounted to the racks of the structure. You should use a beam of the same section as for the rafters. To increase the strength of the fight, they are nailed on both sides of the timber.
The same mounting option is effective for firmly fixing the ridge element, which prevents the roof from moving in a horizontal direction.
Frame with contractions
with braces
Struts enhance the bearing capacity wooden frame and provide the strength of the rafter board.
An important requirement when installing the strut is a correctly measured cut angle, which makes it possible to fit the strut tightly to the connected elements.
ATTENTION!
If, with a layered system, the supporting part is located in the center of the frame base, then the brace is attached at an angle of 45 ° to the horizontal line, if the support is closer to one of the load-bearing walls, then the attachment angle may be different: from 45 ° to 53 °.
It is advisable to erect a frame with struts in places where there is a possibility of planting a foundation, or in wooden buildings where slight wall shrinkage is acceptable.
Frame with braces
With two supports indoors
When there are two supports in the form of internal walls, then when arranging the rafter legs, beams are placed under them. If the beams are not installed, then a rack resting on an internal support is nailed to the base of the rafters.
The rafter beams are installed on load-bearing supports. On the supports inside the room, beds are installed, on which the load from the rafter beams from the racks falls. The rafters are cut so that they fit snugly against each other, and fixed.
With this design, the ridge run is not installed.
To ensure the rigidity of the structure, puffs are attached.
The stability of the structure is ensured by means of racks, which are installed horizontally from the inner base to the rafter leg, and jointing - wooden beams that connect the bases of the racks obliquely.
If the structure is spacer, then a beam is attached above the girder, connecting the frame legs - a crossbar.
Layered system
Types of truss systems
Mansard roof rafters
Before installing the truss system under the attic, it is necessary to correctly calculate the load of the roof and take into account other factors, which may affect its functionality. All wooden elements must be treated with antiseptics.
Installation of the truss system is carried out in stages:
- Install the Mauerlat on the waterproofing layer. They fasten the board to the walls with staples or nails and tie it with metal wire to hooks prepared in advance in the wall;
- Frame elements are cut;
- The main rectangle is made from puffs and racks;
- Two middle runs are mounted, to which the lower rafters are attached;
- The structure can be raised to the roof, where the upper rafters are already installed, connecting them at the upper base, securing the ridge beam and the side run;
- Reinforce the structure with the necessary elements: puffs, racks, struts, additional stops.
After installing the frame, it is laid on it vapor barrier film, install , elements and cover material.
Mansard roof device
The device of rafters for the attic
The gable roof attic has the simplest hanging system.
For attic floor it is advisable to make ready-made trusses on the ground, and then raise them to the roof, after installing the Mauerlat.
The trusses consist of rafter legs, firmly fixed by tightening at the lower base. You can additionally use struts or headstock.
Of great importance is the fastening of puffs on the rafters. It is recommended to install puffs so that their bars are located half a meter behind the wall line, then there is no need to additionally install an overhang.
You can read how to make rafters yourself.
Farms are fixed with the help of upper and lower runs.
Rafter system for the attic
Gable roof truss system: elements
When arranging the frame of a gable roof, elements are used:
- Mauerlat. An element that is attached to a load-bearing wall. The entire structure of the truss frame is mounted to it;
- Run. A beam connecting the rafter legs on the sides and in the ridge element;
- Puff. A beam attached to the rafter legs, preventing their divergence;
- Grandmother. A beam located vertically and fixed at the ridge and puff;
- Strut. Plank connecting at an angle the bed and the rafter;
- Rack. Vertically rests on the bed and rafters;
- . Beam connecting the upper bases of the rafters;
- filly. The built-up part of the rafter for the overhang;
- Overhang. Additional design, serves to protect the outer wall from rain;
- Crate. Lattice installed on the truss frame for attaching the top layer.
The combination of several elements (rafters, racks, braces) in one plane is called a truss.
Gable roof truss system, drawings and photos below:
Drawing of the elements of the truss system
Knots of the truss system of a gable roof
Reliable fastening of structural units provides strength and endurance of the structure, increases its service life.
The strength of the base of a gable roof depends not only on proper fastening.
It also consists of the correct calculation of all elements of the frame, from the verified definition of the type of structure at the design stage.
Rafters for a gable roof are connected to different structural elements.
The main components of the design:
- With beam: fasten either with a spiked tooth or a tooth with an emphasis. Additionally, corners are used. They are mounted to the beam by cutting out an emphasis for the spike in the beam with a socket. A single tooth is attached with a spike and an emphasis. If a cut is made, then the distance from the edge of the bar should be 0.2 - 0.4 m;
- With Mauerlat: with rigid fastening, corners are used or washed down, which is fixed with nails or staples, when hinged - moving metal fasteners, when washed down - a nail or staple;
- With skate: cutting off the edge at an angle, fasten end-to-end with nails, fastening with a bracket or patch board. Overlapped boards are fastened with a bolt or studs.
Depending on the span, the elements are fixed:
- grandmother. Top - with brackets and a collar, bottom - with a collar;
- Strut. The top is attached to the rafter, the bottom - to the headstock;
When designing any residential building, architects pay special attention to the roof, as 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 the usual gable roof, although it can be called the most reliable, since it has only two pitched planes and one joint between them. Many are attracted to more complex designs that add a special appeal and originality to the structure. Other, more practical homeowners prefer attic structures that can simultaneously serve as a roof and a second floor.
The basis of any roof is an individual truss system, which has its own design features. Make a choice desired frame roofs will be much easier if you figure out in advance which types and schemes of truss systems used in building practice. After receiving such information, it will become more clear how complex such structures are in installation. This is especially important to know if the roof frame is supposed to be built independently.
The main functional tasks of truss systems
When arranging pitched roof structures, the truss system is a frame for covering and for holding materials of the "roofing pie". With proper installation of the frame structure will be created the necessary conditions for correct and non-insulated types of roofs that protect the walls and interior of the house from various atmospheric influences.
The roof structure is also always the final architectural element of the exterior design of the building, supporting its stylistic direction with its appearance. Nevertheless, the design features of the truss systems must first of all meet the requirements of strength and reliability that the roof must meet, and only then - aesthetic criteria.
The frame of the truss system forms the configuration and angle of inclination of the roof. These parameters largely depend on natural factors, characteristic for a particular region, as well as on the desire and capabilities of the homeowner:
- The amount of precipitation in different periods of the year.
- Direction and average wind speed in the area where the building will be erected.
- Plans for the use of the space under the roof - arranging residential or non-residential premises in it, or using it only as an air gap for thermal insulation of the premises below.
- Variety of planned roofing material.
- Financial capacity of the homeowner.
Atmospheric precipitation and the strength of wind currents give a very sensitive load on the structure of the roof. For example, in regions with heavy snowfalls, you should not choose a truss system with a small angle of inclination of the slopes, as snow masses will linger on their surface, which can lead to deformation of the frame or roofing or leaks.
If the area where the construction will be carried out is famous for its winds, then it is better to choose a structure with a slight slope of the slope so that the sharp gusts that occur do not rip off individual elements of the roof and roof.
The main elements of the roof structure
Details and nodes of truss systems
Depending on the chosen type of truss system, the structural elements used can vary significantly, however, there are details that are present in both simple and complex roof systems.
The main elements of the pitched roof truss system include:
- Rafter legs forming roof slopes.
- - a wooden bar fixed on the walls of the house and serving to fix the lower part of the rafter legs on it.
- The ridge is the junction of the frames of two slopes. It is usually the highest horizontal roof line and serves as a support on which the rafters are fixed. The ridge can be formed by rafters fastened together at a certain angle or fixed on a ridge board (run).
- Lathing - these are slats or beams mounted on rafters with a certain step and serving as the basis for the flooring of the selected roofing material.
- Retaining elements, where you can take beds, girders, racks, struts, ties and other parts, serve to increase the rigidity of the rafter legs, support the ridge, link individual parts into a common structure.
In addition to the structural details mentioned above, other elements can be included in it, the functions of which are aimed at strengthening the system and optimal distribution of roof loads on the walls of the building.
The truss system is divided into several categories depending on different features of its design.
attic space
Before proceeding to consider different types roofs, it is worth figuring out what an attic space can be, as many owners successfully use it as utility and full-fledged living quarters.
The design of pitched roofs can be divided into non-attic and attic. The first option is called just that because the space under the roof has a small height and is used only as an air layer that insulates the building from above. Such systems usually include or have several slopes, but located at a very slight angle.
The attic structure, which has a sufficiently large ridge height, can be used in different ways, be insulated and not insulated. These options include attic or gable version. If a roof with a high ridge is chosen, then it is imperative to take into account wind loads in the region where the house is built.
Slope slope
To determine the optimal slope of the roof slopes of the future residential building, first of all, you need to look at the already built low-rise neighboring houses. If they have been standing for more than one year and steadfastly withstand wind loads, then their design can be safely taken as a basis. In the same case, when the owners set a goal to create an exclusive original project, unlike standing side by side buildings, it is necessary to familiarize yourself with the constructive and operational features various truss systems and make the appropriate calculations.
It should be borne in mind 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 value have normal forces and smaller tangents. If the roof is sloping, 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 combination with the wind load, since the snow load on the windward side will be much lower than on the leeward slope. In addition, there are places on the slopes where snow will definitely collect, giving a big load on this area, so it should be strengthened with additional rafters.
Roof slopes can vary from 10 to 60 degrees and must be selected not only with regard to 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 mass, their fixing requires a different number of elements of the truss system, 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 slope. Equally important are the features of each coating in terms of resistance to moisture penetration - in any case, many roofing materials need one or another slope to ensure the free flow of storm water or melting snow. In addition, when choosing a roof slope, you need to think in advance how the cleaning process will be carried out and repair work on the roof.
When planning this or that angle of the roof slopes, you need to know that the fewer joints between the sheets of the coating, and the tighter they are, the less you can make the slope of the slope, of course, if it is not supposed to arrange a residential or utility room in the attic space.
If, however, 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.
Given the weight of the roofing material, you need to know - the heavier the coating, the greater the angle of the slopes should be, since in this case the load will be correctly distributed to the rafter system and load-bearing walls.
The following materials can be used to cover the roof: either a profile sheet, galvanized steel, corrugated asbestos-concrete and bitumen-fiber sheets, cement and ceramic tiles, roofing material, soft roof and other roofing materials. The illustration below shows the permissible slope angles for slopes for various types roof coverings.
Basic structures of truss systems
First of all, it is worth considering basic types truss systems relative to the location of the walls of the house, which are used in all roof structures. The basic options are divided into layered, hanging, and also combined, that is, including elements of both the first and second types of systems in their design.
fasteners for rafters
Layered system
In buildings where internal load-bearing walls are provided, a layered truss 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, fewer materials will be required for this design.
For rafters in this system, the defining reference point is the ridge board, on which they are fixed. The non-thrust type of the layered system can be equipped in three versions:
- In the first version, 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 with wire or staples.
- In the second case, the rafters in the upper part are cut at a certain angle and interconnected using special metal plates.
The lower edge of the rafter legs is attached to the Mauerlat with movable fasteners.
- In the third version, the rafters are rigidly fastened in the upper part with bars or processed boards located horizontally, parallel to each other on both sides of the rafters connected at an angle, and a ridge run is pinched between them.
In the lower part, sliding fasteners are used to fix the rafters, just as in the previous case.
It is necessary to explain why sliding fasteners are often used to fix the rafters on the Mauerlat. The fact is that they are able to save the load-bearing walls from excessive stress, since the rafters are not rigidly fixed, and when the structure shrinks, they have the ability to move without deforming general design roofing system.
This type of fastening is used only in layered systems, which also distinguishes them from the hanging version.
However, in some cases, a spacer system is used for layered rafters, in which the lower end of the rafters is rigidly fixed to the Mauerlat, and in order to remove the load from the walls, puffs and struts are built into the structure. This option is called complex, as it includes elements of a layered and hanging system.
