Plan of the rafter system. Types and diagrams of rafter systems: overview and recommendations for installing a roof rafter system. Flat roof plan
Plan and drawings of a gable roof
It is difficult to imagine a building without a reliable roof over it. Any roof is the basis, the main guarantor of the inviolability of things in the house and the safety of property. It is the main protector from rain, snow and wind. After its construction, you can move on to the next stage, which involves interior work. Having made this part unreliable, there is no need to talk about a full-fledged home. A do-it-yourself gable roof is the simplest and most functional option among other types of roofing. Roof parts
There are several roof options, one of which is gable. Construction does not require a lot of talent, since this type of roof is the simplest. The housing element consists of the parts shown in the figure:
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The structure consists of the following parts:
Horse. The upper part that will connect the 2 slopes.
Rack. An installation used to redistribute weight from the top to the bottom of the roof. It must be made from quality materials.
Sill. A beam located horizontally. Connects the rack and the load-bearing wall.
View of the roof from the inside 
Start of the skate
Start of the skate
Struts. These boards are fixed at a slight angle. Serve to redistribute weight from the rafters to the load-bearing elements below.
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Rafter leg. These elements form a visible outline in the shape of a triangle. Serve to hold the roofing covering. The heavier it is, the more often it is necessary to lay the rafters.
Fillies. Boards that extend the rafters. Necessary to create an overhang with two pitched roof, By building regulations which must be at least 0.5 m.
Simple gable roof 
Fillies in schematic form
Difference between rafters
It is quite possible to complete the roof plan for a gable roof and the drawing on your own. All elements can be constructed in several ways. The difference is the rafter system used for construction. There are the following types rafters:
- Layered. Here it is necessary to install additional support beams located in the middle of the load-bearing walls. The rafters will transfer part of the load internal devices to lighten the weight. The type of rafters is used if the roof, built with your own hands, is heavy, with large areas dwellings, significant distances from the walls (more than 10 meters).
Types of rafter systems
The systems are used in many homes, and both are of sufficient quality for comfortable use. During construction mansard roof, are used together. In this case, hanging and inclined types of rafters are combined. It is worth creating rafter drawings that will show the location of each element of the roof, built with your own hands, so that there are no incomprehensible moments. It will help you calculate the amount necessary materials.
Any element of the house must be created, understanding how it will all look as a result. For clarity, a drawing is created, and so that everything fits perfectly, it is calculated in advance. The plan takes into account the length of the roof along the ridge, the length of the slopes, and the length of the plumb lines is shown separately. The angle of inclination of the roof is determined. The angle is determined taking into account the following points:
- In case of strong winds in the construction area, the angle is set to about 10-12° so that the roof is not torn off.
- With significant winter precipitation, the slope is within 30-40o. the snow will easily slide off the surface. There are no difficulties in the calculations, but if the roof is made with a complex shape, this will make it difficult to calculate the required values.
Roof construction
After making calculations and purchasing the necessary parts, the Mauerlat is installed. After this, the sheathing is created. The element is the basis for a do-it-yourself roof, made from pine or other coniferous wood. The material is durable and lightweight, capable of distributing the weight of all elements over the entire plane. Placed along roof slopes, between the rafters, the top of the walls. 
Mauerlat
In order for the element to last longer, an insulating layer is necessary between the wall and it. Roofing material is suitable for this. The Mauerlat can be secured using any fasteners that are convenient.
To erect a roof, you must follow the plan:
- Fastening the rafters. If hanging ones are used, they must be assembled in advance, using fasteners to stiffen this part. First, the outer elements are made, then the inner ones. With a layered system, a bed is first created where the supports will be installed. If the length of the elements is insufficient, you can add it by installing fillies.
Installation of sheathing. You can use any materials for construction, but it is important to get rid of bark from the boards in order to increase the service life of the elements. If you plan to use a soft roof, the sheathing is made continuous. A rigid base is required here so that there is no deformation during operation. 
Continuous sheathing
Lattice. It is done using hard types of coating: slate, metal tiles. 
Lattice system
Roofing. There are many coating materials, each of them involves the use different methods coverings. Do not neglect the recommendations of the material manufacturer. It is important to make a slight overlap between the elements. The structure must not be disturbed to prevent leaks.
Do not forget that a reliable roof, built with your own hands, is a guarantee of the safety of property in the house. You should not neglect its construction, so that later you do not have to make complex repairs.
Construction of a gable roof rafter system - a quick guide
Required tools and materials
There are different types of roofing, they differ in shape and consist of various materials, however, what is common to all is the presence of a foundation. Consider the device rafter system for a gable roof.
Roof truss system design
So, every building has a roof that is supported by something. It is this support, without which installation of the roof simply would not be possible, that is called the rafter system. It consists of many structural elements, these include braces, racks, ridge purlins, battens with counter-battens, etc. In fact, its importance is comparable to the skeleton in the human body.
Wood is mainly used as a building material. However, you should not think that absolutely any wood will do, as long as the dimensions are maintained. For this purpose they take only quality materials, preferably coniferous species. In addition, they must be well dried in natural conditions. Also, before use, all elements must be treated with a special antiseptic to prevent the appearance of fungus, mold, rot and termite damage. Also worry about fire safety, they are also sold for this different kinds special solutions.
A feature of all new buildings will certainly be shrinkage, so many builders advise installing floating rafters. Their design is not fundamentally different from the one you have chosen; modifications are carried out only for attaching the leg and ridge beam. The installation is carried out without rigid fixation, and during the shrinkage process, the rafters can slightly change the location of their elements, without changing or losing strength. Otherwise, parts of the structure may bend or even break.
Gable roof and types of rafter system for it
As the name suggests, the device gable design assumes two wings, i.e. inclined planes, connecting to each other at the very top. What about the bottom, it rests against the walls of the building. The front and rear gables can be brick, cinder block or other building material. In addition, they are often decorated, especially since today there are many ways to give this element unique view.
This design of the roof truss system has many advantages, for example, the ability to arrange attic space, of course, it is not suitable for living, but storing things there is quite possible. Also, the resulting space is often used as an attic. Besides, it's enough economical option, and the probability of leakage is minimal.
Now it’s worth dwelling a little on what options for gable roof rafter systems exist. So, there are hanging and layered types of structures. In the first case, the support is the ridge of the roof, and in the second the walls of the house, as well as an additional intermediate support, for example, the middle load-bearing wall. These rafters also differ in the principle of service.
Beams hanging system They work simultaneously for both compression and bending, but what about layered ones, in this case the emphasis is only on bending.
The best option is a combined structure of a gable roof (alternating sloping and hanging rafters ny elements). Using this method you can not only save construction material, but also to make the structure somewhat stronger, and this is not superfluous. After all, this part of the house is subject to heavy loads, for example, sometimes a person is forced to climb onto it in order to restore it; in addition, one should not underestimate the power of winds, snow, rain, etc. So, regardless of the type of gable roof rafter system chosen, the design is mandatory must be sufficiently reliable and strong.
DIY rafter system for a gable roof
So, having understood the basic concepts, you need to pay attention to the practical part.
How to make a rafter system for a gable roof with your own hands - step-by-step diagram
Step 1: Arrangement of the base for the rafters
Direct installation of the roof truss system can be started only after the pediment, ridge, mauerlat, and floor beams have been installed (for the attic, beams of a larger cross-section are taken). In addition, you should lay boards on the ceiling, which will serve as the floor of the attic or attic, depending on the purpose of the room.
Step 2: Preparing the Material
Of course, prepare workplace necessary first of all, however, how strong the structure of the rafter system of your gable roof will be largely depends on the quality of the material. So we buy only high-quality wood - the most suitable beams for this purpose are with a section size of 50x100 mm. A smaller size is not always able to serve for a long time, and during strong winds or snow melting you will hear the pitiful creaking of wood. Do not forget to treat them with all the necessary means, they have already been discussed above. Next, we cut out the elements for the rafter system. It is much more convenient to do this on the ground and then lift the finished parts. Cuts should be made on the ridge where it will connect to the legs of the rafters.
Step 3: Installation
Having installed the ridge, you should also mark the places where the beams are attached to the Mauerlat and make grooves there. The outer beams are installed first. Then a strong thread is stretched between them (a fishing line will do) to make it easier to position the intermediate legs. The beams are attached to the ridge with long nails, but to fix them to the Mauerlat, you will need anchor bolts. To increase the reliability of the gable structure, additional spacers should be installed; they are also nailed.
House with a gable roof: project + Photo - rafters before price calculation
Often, when building a roof, people have to do quite a bit Difficult choice– which option to prefer.
The fact is that modern technologies provide the opportunity for such a choice, allowing you to install any type of roof in a fairly short time. In Russia, gable rafter roofs have always been more popular.
When thinking about which design is more suitable, the homeowner is guided by many factors: its functionality, reliability and durability, and the ability to prevent precipitation from entering the building.
Perhaps this was facilitated by the features climatic conditions our fatherland.
In winter, a lot of people gather on such roofs. less snow, because it rolls off the surface, reducing the load on the structure.
The number of slopes does not in any way affect the parameters of the house, so the specific choice depends on the preferences of the owners.
The gable roof of the rafter system is quite easy to install, it is durable and reliable in operation. Its structure allows the use of many of the most different materials as roofing materials: from the usual, well-known slate, to fashionable metal tiles.
House with a gable roof: advantages
Such a roof looks like two surfaces inclined towards each other, oriented along the long sides of the house, connecting at the top into a ridge. It goes great with classic house, having the usual rectangular shape.
Among the advantages are:
- sufficient strength and slope height, allowing the use of almost any roofing material;
- light and simple design;
- well ventilated attic;
- the slope of the slopes, preventing the accumulation of sediments.
The roof slope is an important parameter for this type of roof. For arid areas, its optimal value is up to 45 degrees. Where the amount of precipitation is high, it increases to 60. When designing a roof, the prevailing winds in a given area should also be taken into account: after all, with an increase in the angle of inclination, the windage of this part of the structure increases.
The choice of the appropriate type of roofing also depends on its slope.
Tiles and slate, for example, can only be used if the temperature is at least 22 degrees. The final cost of the roof will also depend on the slope of the slopes. The larger it is, the more you will have to spend on coating materials, and the higher the overall price will be.
Gable roof rafters: device diagram
What does any rafter system consist of? These are the rafters themselves, the roof plate, the struts and the sheathing. The rafter legs with their upper ends must be overlapped using special overlays. The lower ends are connected to support beams made of logs, as well as to the mauerlat.
According to the project, a gable roof can be made in two ways: with hanging rafters, or with sloping ones. This or that method is selected based on the size of the structure itself frame house or gazebos.
It is extremely important that the calculation of the gable roof (rafter system structure) is carried out correctly. It's best to deal with it professional worker worth hiring.
Fastening the support beam (aka Mauerlat)
It can be done using various methods:
- The most reliable of them (also the most common) is as follows. When the walls are installed, onto which the support beam is then planned to be attached, a concrete belt (continuous) is created around the perimeter of the building. It can be replaced with a concrete beam.
Thick studs, at least 12 mm in diameter, are inserted into this armored belt. The studs must penetrate the axis of the Mauerlat when attaching it. From its edge to the edge of the armored belt you need to leave about five centimeters. The distance between the studs should be from one and a half to two meters, so that each part of the support beam is securely fastened along the edge.
We should not forget at least about the minimum required roof slope. Otherwise, you may experience leakage or damage from strong winds.
- During laying, the studs are embedded directly into the wall. They will have to be walled up much deeper, so the studs themselves must be much longer. Not like that reliable way fastenings as the previous one, but for a gable roof with an area of less than 250 square meters (with or without an attic) it is quite suitable.
- Most affordable way. A soft but thick wire is laid in advance in the masonry, with the help of which the Mauerlat is then secured. How it's done? Shortly before the end of the laying, when several rows remain, the middle of the wire is placed between the rows so that its ends protrude evenly on both sides.
Mounting diagrams for the Mauerlat
Their length must be sufficient to attach the support plate. To prevent the wire from being too noticeable, its outer end is passed through the mortar joint between the bricks. This method is quite common and very reliable, especially if we are talking about a building of modest size (for example, 10 by 10)
If the walls and beams have undoubted strength, then the rafters can be attached directly to the beams without using a support plate. Plan gable roof rafters may involve the use of the upper crown of the house (chopped) instead of the mauerlat. IN in some cases A separate support beam for the roof is required.
Between the purlins and racks, to enhance the stability of the rafters, struts are made. Required parameters for struts and rafter legs are calculated according to the roof calculation. The usual width of simple rafter boards is approximately five centimeters, but their height is up to 20.
To form an overhang that will become reliable protection external wall from precipitation, puffs or rafters are placed at least half a meter beyond the plane of this very wall. A good layer of waterproofing must be laid under the Mauerlat, otherwise the service life of the structure will be greatly reduced. You can use good old roofing felt or other similar material.
Several layers of insulation are laid between the rafters, always with offset seams. Materials with low thermal conductivity are used as insulation, for example, ordinary mineral wool. In addition to thermal insulation, it is also necessary to install a vapor barrier. To do this with inside The insulation is fixed with a well-stretched polyethylene film.
A special vapor-tight seal is used waterproofing film. This is a diffuse membrane with a special perforated structure. It is capable of releasing incoming interior space steam enters the insulation, but prevents moisture from entering it from the outside.
Lathing: assembly order
After this, you can begin the direct installation of the gable roof according to the drawing. Final (before roofing work) The stage of completing the gable roof structure will be the assembly of the sheathing. Its production usually takes wooden beam 6*6, 5*5 or 4*4 cm. Install it perpendicular to the rafters, as provided by the design. The sheathing serves to transfer and redistribute the weight of the roof to the rafters, which, in turn, direct it to the load-bearing walls of the building. The pitch of the sheathing can be different, and it depends on the type of roofing material chosen.
Some of them generally require the installation of a continuous covering-flooring. These are, for example, flat slate or soft roof. And under soft tiles bitumen requires additional underlay carpet, mounted on top of the deck. It not only levels its surface, but also protects it from unnecessary moisture when laying roofing materials.
To do this, you can use specially treated fiberglass with bitumen impregnation.
DIY gable roof is a great choice for responsible homeowners who aren't afraid to get their hands dirty and are ready to get to work. Simple design, which represents an isosceles triangle in section, is not at all difficult to build yourself. The height of the descent and the angle of the roof can be varied, but certainly within the limits of correctly made calculations.
Construction of a gable roof truss system: assembly and installation
The roof is the structural element of a house that gives it a unique look. Options for constructing such structural element- a great many. But among them there is one, gable, the appearance of which changes remarkably depending on the angle of inclination of the slope.
In order for the structure to be as strong, reliable and durable as possible, the design of the gable roof rafter system must be thought out at the stage of developing the house project. A properly executed structure must be able to cope with permanent loads, say, the weight of the roof, as well as temporary ones presented by nature - snow, wind, rain. The most optimal plan is considered to be a gable roof plan, in which rafter legs their ends rest against a support beam, the so-called Mauerlat, and are fixed in a special way. In this case, the load can be evenly distributed around the perimeter of the house.
Rafter system design
As already noted, the key to the strength of any roof is its rafter system. According to their design, they are divided into layered and hanging.
Hanging
Hanging rafters are beams that have only two points of support, namely the walls of the house. In this case, each leg is subject to mainly two types of loads - bending and compression.
Hanging ones transmit horizontally the load bearing on them (the weight of the roof, snow, wind) to their support points, that is, to the walls, as a spreading force. To reduce its influence, the rafters are connected with a wooden or metal tie. IN rafter device of a broken gable roof, similar ties are floor beams. With a span of 8 m or more, headstocks with struts are additionally installed under each truss.
Layered
Layered rafters are beams that have an intermediate support that rests on additional supports or the internal wall of the house. The main effect of this system on supports is bending. IN load-bearing structure roofs can only be used overlays if intermediate supports are located at a distance of up to 6.5 m from each other.
The layered structure is lighter than the hanging or combined system.
The scheme may also contain elements of a future attic. Vertical racks, reinforced with struts and crossbars, which are installed in this case, can serve as part of the attic in the future. They are supported by floor beams. Read: Installation of a gable roof rafter system.
Installation of the rafter system
Mauerlat installation methods
In houses made of logs or beams, the lower part of the rafters is supported by the upper crown, and in brick or stone houses - a special support beam, Mauerlat. It is laid on a waterproofing pad on the inside of the wall along the attic. 
The Mauerlat is fixed to the wall:
- by means of a reinforcing belt (on concrete with studs), on studs embedded in the masonry of the walls, using wire rod.
A hairpin is a metal rod with a thread. Its length is chosen on the basis that one half of the stud will be embedded in the wall, and the protruding part should be enough by 3–4 cm to tighten the nut on top of the Mauerlat.
Ridge run
The design of the gable roof top part rests on the so-called ridge run. It is a log or timber to which the upper ends of the rafter legs are attached. It is this run that will subsequently serve as the ridge of the roof.
- With a house length of up to 6 m, it is permissible to prepare a ridge run from a single beam or log. At the same time, it can rest on two pediments without additional supports. When the length of the house is more than 6, for the installation of a composite ridge girder, use construction trusses.
Additional items
- The side girders serve as additional support for the system itself. They are supported either by building trusses or by the gables of the house. If the structure is heavy, the purlins are made in the form of a “construction lift” or a rocker. Struts help relieve the rafters in the center. They are installed under all “legs” at an angle of 45° or more. In this way, you can build a gable roof up to 14 m. Braces (diagonal beams) strengthen the rafters and help the gables withstand strong wind loads. The support of their upper part is the corner of the pediment, the lower part is the central floor beam.
Installation procedure
Rafters can be installed in two ways:
- assemble the truss on the ground and lift it up; assemble trusses directly at the installation site.
The choice of installation method, of course, is up to the contractor, however, in any case, when creating trusses of the same type, it is more convenient to use a template according to which the rafters will be cut and connected.
Making a template like this is not at all difficult.
- To do this, take two boards, slightly longer than the rafters, lift them up and install them like the future structure. Align them vertically so that the top of the ridge is installed in accordance with the drawing, the boards are connected with one nail. By lowering or raising the ends of the boards, achieve the required angle of inclination and connect the boards using a transverse strip and thus fix them in the desired position. The finishing version is adjusted to this template and connected.
Technology of fastening to the Mauerlat
Mounting is one of the important points when installing the roof. The rafters are attached to the mauerlat in two ways.
Rigid fastening. The main principle of this technology is the exclusion of any influences on the connection - bends, turns, shifts. Such staticity can be achieved by fastening the rafters using corners or support beams. You can also make cuts on the rafters, use staples, and drive nails. Additionally, they are attached to the wall with wire or anchors.
Sliding (hinged). This type of fastening, which has 2 degrees of freedom, is especially recommended for wooden houses. The moving part in this design is the rafters. It is performed using a special saw, securing the joint with two nails driven at an angle, or a metal plate equipped with holes for nails and others.
Trusses are first installed at the beginning and end of the building, after which a cord is pulled between them. The horizon level should be perfectly level. If a distortion is detected, one of the trusses can be lowered slightly. All other rafters are installed under this cord with the pitch specified in the project. Then they mount additional elements: supporting beams, braces, frames and crossbars.
As an example, watch the video: “Gable roofs: installation of the rafter system.”
1) Draw the coordination axes of the building.
2) Draw the outline of the walls.
3) Lay a mauerlat along the perimeter of the building on the outer walls.
4) Place a support beam in the corners of the building to support the diagonal rafter legs.
5) At an angle of 45°, draw diagonal rafter legs from the corners of the building.
6) By interior wall lay down the building and show the upper run.
7) Lay the rafter legs, starting from the support unit, at a certain distance.
8) Lay short rafter legs (springs) along the diagonal rafter legs in a checkerboard pattern.
9) Install the racks every 3000 - 6000 mm, starting from the support unit.
10) If the building width is more than 12 m, place a crossbar at the rafter legs.
11) To form a cornice, a filly is nailed to each rafter leg, and fillies, called shorties, are nailed to the diagonal rafter legs on both sides.
An effective solution roof design is the use of layered rafters to cover spans of up to 14 m if the building has one internal support and up to 16 m with two internal supports.
The rafters are connected using fastening bolts, staples and nails.
In the case when the distance between supports (external or internal) is more than 7500 mm, in civil buildings the load-bearing basis of the roof is roof trusses, representing a flat geometrically unchangeable lattice system consisting of individual, interconnected elements (rods). Rafter trusses can be wooden, metal-wood, steel and reinforced concrete. Wooden trusses called hanging rafters.
The pitch of trusses for spans up to 9 m is 3–4 m, for spans over 10 m – 1.5–2 m.
Hanging rafter diagrams
Dormer windows arranged in pitched roofs for lighting, ventilation of the attic, and access through them to the roof. They can be semicircular, triangular, rectangular shape. Lighting is provided through a glazed sash measuring at least 0.6×0.8 m. For ventilation, wooden louvered grilles are used, located adjacent to the glazed sash of the dormer window. Dormer windows must be placed in such a way as to ensure through ventilation. It is recommended to place the bottom of the window no higher than 0.8 - 1.0 m from the top of the attic.
Types of dormer windows
a – triangular; b – semicircular; c – rectangular; g – polygonal
1 – glazed parapet; 2 – louvered grille
In this lesson we will look at how to compose and rafter plan in AutoCAD (2010). According to current standards, a roof plan must be drawn up for buildings with internal drainage. If the drainage in the building is external and the building is not complex, then such a drawing is not necessary. Next, let's see how to draw a plan for a pitched roof and flat roof industrial and public buildings.
How to draw a roof plan
General information about the construction of drawings of industrial and roof plans public buildings: to construct a drawing, the plan is divided into rectangles, according to the building plan. Inside the rectangles, lines are drawn that will indicate ridges and valleys - the external and internal junctions of the slopes. These lines are projections of the main elements of the walls, so the roof model will be better represented in volume. Some of the rectangles will be located outside the walls. This required condition to a correctly executed roof plan, since they must have an overhang.
The roof plan of a pitched roof is distinguished by the presence more projection lines of ridges and valleys, since the slopes have a large slope, in addition, such roofs are often made complex shape. The roof plan of a flat roof is often limited to just a few lines.
The construction of front or side views is carried out taking into account the slopes of the roof slopes. The roof slope is set at the stage and is determined by the purpose of the building, its type, the selected roofing material, etc.
3 rules for drawing a pitched (flat) roof plan:
- the intersection of two slopes forms a ridge (endow). Its projection on the plan divides the angle of the rectangle into equal parts;
- if the eaves lines are parallel, then the ridge line will be parallel to them... its projection will be in the middle, unless otherwise determines the type of roof (for example, if the slopes are not equal);
- When two lines of intersection converge at a point, a third one will most likely pass through it.
Suggested procedure for working in drawing programs:
- draw a polyline around the existing house plan;
- copy it, as well as the outlines of the main walls, onto a drawing with a roof plan;
- mark with a line the projection of the upper ridge of the house;
- draw the remaining ridges and valleys using the three rules given above;
- place ventilation and smoke ducts on the roof plan;
- post skylights(if any);
- directions of drains, slopes of slopes, marks;
- indicate dimensions on the plan (along axes and contours).
After reading this lesson, you should not have any questions about how to draw a roof plan - a house plan; you must agree that the whole drawing is just a few lines! However, the question: how to draw a rafter plan has not yet been resolved.
How to draw a rafter plan
The rafter plan is a designation of pitched roof elements that is omitted from the roof drawing. The rafters are positioned taking into account the roofing material, since different materials require different foundations. In the case of metal tiles, it is necessary to leave a space of 450 cm between the rafters. Drawing procedure in AutoCAD:
- copying the roof plan or mirroring half of the roof, if these drawings must be combined;
- assigning roof lines a smaller thickness;
- parallel offset from the ridges and valleys of the lines by half from the rafters (if the rafters are 15 cm, then the offset in the program must be specified as 75 mm);
- after this, the main frame is ready (see more details: the rafter system of the house), then you need to move on to the rafters of the slopes, it is recommended to draw them from the middle of the roof, especially if the building is symmetrical (it is better to place two lines at once on opposite sides of the line of symmetry and move from them) .
- The distance for placing the rafters is selected individually, taking into account the characteristics of the roof of the house; in my work it was up to 800 mm; in places where chimneys pass, the distance was reduced to 600.
Construction country house or cottage always implies the use of a rafter system similar to that used in the construction of residential buildings. The material for such rafters is usually wood.
The rafter system can be made not only in the form of a triangle, but also in the form of other structures. But no matter what material and what form will be used, first of all, you still need to know what a rafter plan is.
What you need to know to develop a rafter plan
In order to save living space, attic rafter systems are chosen, since it is with their help that it becomes possible to equip an additional living room in the attic.
In general, a process such as designing a rafter system can be considered quite complex, since it requires certain skills, knowledge and skills. Therefore, to carry out everyone necessary calculations and competent drawing up of the drawing, it is best to use the services of a specialist who already has some experience in such work.
The most important parameters that must be taken into account, starting from the roof design stage, are:
- Roof slope angle
- Selection of rafter section
- Roof type
- Material to be used for roofing
- Calculation of the rafter system
The level of slope of the slopes must be taken into account when selecting materials and when calculating the strength of the supporting structure necessary for any roofing work.
Most of the materials that can be used for such purposes can have a very noticeable impact on the design of the rafter system as a whole. Therefore, it is necessary to choose the material that will be used to cover the roof very carefully, with all responsibility, and this must be done during the design process.
The drawing of the rafter system must be calculated with special care, since everything possible mistakes and shortcomings that are allowed when assessing loads may well lead not only to damage and deformation of the rafters, but also to complete destruction the roof already during its operation, up to the complete collapse of the roof.
Development of a rafter plan
The process of developing a rafter plan includes procedures such as:
- Construction of modular axes linked to the thickness of the building’s load-bearing walls. In this case, on the plan itself the removal of the crowning cornice is shown on external wall using a contour line.
- Ventilation and pipelines must also be indicated on the plan; their location must certainly be taken into account when arranging elements in the rafter system design.
- Based on the selected roof structure, a plan is developed. In this case, the walls and the fastening of the rafters in the ridge must be taken into account directly on the sketch.
Using such a sketch allows you to draw a plan of the rafter system, with the mauerlats, longitudinal struts and racks, a rafter beam, and rafter legs marked on it.
The selection of a suitable distance between adjacent rafters is carried out based on:
- from the weight of the material chosen for roofing,
- scaffolding that will be used in this case,
- the pitch of the rafters can be changed due to the need to pass through them ventilation pipes or chimney.
Also, ventilation and pipes can be passed through by interrupting the legs of the rafters, for which their ends are supported on special wooden jumpers, which are located between the adjacent rafters, and secured using a special rafter cut.
If we are talking about gable roofs, That dormer windows must be on the gables, which, in turn, are located at the ends, which cannot but increase the efficiency of attic ventilation in the summer.
Features of the design of a roof with four slopes imply the display on the plan of eaves resting on diagonal rafter legs, as well as dormer windows located on the hips.
In cases where the space under the roof is planned to be used for the construction attic floor, this should also be shown in the drawing in the form of upper beams that will serve as support for the rafters.
Also, we should not forget that the rafter layout should be developed simultaneously with the plan various designs sections of the building.
And both of these plans must necessarily be united by the presence of a common connection.
The drawing must take into account the data of all distances between the modular axes of the proposed structure, since all indicators of the thickness of future walls are associated with them.
Directly in the plan itself, the distances between the chimney, ventilation and racks must be indicated. In addition, the plan should display callouts indicating all the necessary values cross sections
and lengths of all available parts. The calculation of the rafter system should be done not after the construction of the house frame, but at the stage of preparing the building project. We must remember that for very important and prestigious buildings, it is recommended to order such work from professional architects, only they will be able to carry out correct calculations
and guarantee the duration and safety of operation of the structure.
| Although this is one of the simplest types of systems for residential buildings, there are several types of design. Diversity allows you to increase the options for using roofs when building houses according to standard or individual exclusive projects. | Type of gable roof truss system |
|---|---|
| Architectural features and brief description The most commonly used option, has two completely identical slopes |
| The ridge is shifted to one side of the house or slopes with different angles of inclination. The roof truss system is more complex to calculate. If in a simplified version it is possible to calculate one slope and automatically apply the obtained data to the second, then this option cannot be used for an asymmetrical rafter system. Advantages: original appearance. Disadvantages are the complexity of calculations and installation and the reduction in usable attic space. |
| Most often used during construction attic premises, allows you to significantly increase the volume of attic space. The calculations are of medium complexity. Rafter system with external bend. It is rare to find systems with an internal fracture other than the original one. appearance, they have no advantages. |
Structural elements of the rafter system
We will give a list of all the elements that need to be calculated for each specific case.
The simplest element of the rafter system can be made from timber 150×150mm, 200×200mm or boards 50×150mm and 50×200mm. On small houses It is allowed to use paired boards with a thickness of 25mm or more. The Mauerlat is considered an unimportant element; its task is only to evenly distribute point forces from the rafter legs around the perimeter façade walls buildings. It is fixed to the wall on a reinforcing belt using anchors or large dowels. Some rafter systems have large expansion forces; in these cases, the element is designed for stability. Accordingly, the optimal methods for fixing the Mauerlat to the walls are selected, taking into account the material of their masonry.
Prices for timber
They form the silhouette of the rafter system and absorb all existing loads: from wind and snow, dynamic and static, permanent and temporary.
They are made from boards 50×100 mm or 50×150 mm, and can be solid or extended.
The boards are calculated based on their bending resistance, and taking into account the data obtained, wood species and types, the distance between the legs, and additional elements to increase stability are selected. The two connected legs are called a truss and may have tie-rods at the top.
Tightenings are calculated for tension.
Runs
Some of the most important elements rafter system of a gable roof. They are designed for maximum bending forces and are made of boards or timber with a section corresponding to the loads. In the very high place a ridge girder is installed, side girders can be mounted on the sides. Run calculations are quite complex and must take into account a large number of factors.
Can be vertical or inclined. Inclined ones work in compression and are attached at right angles to the rafters. The lower part rests against the floor beams or concrete plates, options for resting on horizontal beds are acceptable. Due to the stops, it is possible to use thinner lumber to make rafter legs. Vertical stops work for compression, horizontal stops for bending.
Lezhny
They are laid along the attic, resting against several load-bearing walls or interior partitions. Purpose – to simplify the manufacture of a complex rafter system, to create new points for transferring loads from various types stops For the beds, you can use beams or thick boards; the calculation is made based on the maximum bending moment between the support points.
Lathing
The type of lathing is selected taking into account technical parameters roofing coverings and does not affect the performance of the rafter system.
What type of lathing is needed for corrugated sheeting? When to install wood and when to install metal? How to choose the right lathing pitch and what factors to consider?
Prices for construction boards
Construction boards
Stages of calculating a gable roof
All work consists of several stages, each of which has a great impact on the stability and durability of the structure.
Calculation of parameters of rafter legs
Based on the data obtained, it is determined linear parameters lumber and step trusses. If the loads on the rafters are very large, then vertical or angular stops are installed to distribute them evenly, and the calculations are repeated taking into account new data. The direction of influence of forces, the magnitude of torque and bending moments change. During calculations, three types of loads must be taken into account.
- Permanent. These loads include the weight of roofing materials, sheathing, and insulating layers. If the attic space is in use, then the weight of all finishing materials should be taken into account internal surfaces walls Data on roofing materials are taken from them technical characteristics. Metal roofs are the lightest, natural slate materials, ceramic or cement-sand tiles are the heaviest.
- Variable loads. The most difficult efforts to calculate, especially now, when the climate is changing dramatically. For calculations, data is still taken from outdated SNiP reference books. For his tables, information from fifty years ago was used; since then, the height of the snow cover, the strength and the prevailing direction of the wind have changed significantly. Snow loads may be several times higher than those available in the tables, which has a significant impact on the reliability of the calculations.
Moreover, the height of the snow changes not only taking into account the climate zone, but also depending on the location of the house on the cardinal points, the terrain, the specific location of the building, etc. Data on the strength and direction of the wind are also unreliable. Architects have found a way out of this difficult situation: data is taken from outdated tables, but to ensure reliability and stability, a safety factor is used in each formula. For critical rafter systems on residential buildings, the standard is 1.4. This means that all linear parameters of the system elements increase by 1.4 times and due to this, the reliability and safety of the structure’s operation increases.
The actual wind load is equal to the indicator in the region where the structure is located, multiplied by the correction factor. The correction factor characterizes the location of the building. The same formula is used to determine the maximum snow load.
- Individual loads. This category includes specific forces that affect the rafter system of a gable roof during an earthquake, tornado and other natural disasters.
The final values are determined taking into account the probability of simultaneous action of all the above loads. The dimensions of each element of the rafter system are calculated using a safety factor. Using the same algorithm, not only rafter legs are designed, but also lintels, stops, braces, purlins and other roof elements.
