Do-it-yourself attic roof: drawings and stages of how to build an attic roof for a house. Construction of an attic roof with your own hands Attic roof frame components dimensions between rafters

IN Lately There is a return to the use of various architectural elements that were undeservedly forgotten during the era of industrial construction. Again you can find bay windows, mezzanines, and attics, which make the exterior of the house more interesting and, at a relatively low cost, allow you to increase the interior space. For example, a rafter system mansard roof 8x10 will increase costs by about $4,500, while adding 60-65 m2 of usable space to the area of ​​the house.

Types of mansard roof truss systems

In practice, several types of rafter systems for the attic are used. They are classified according to the type and shape of the roof: two-, three- and four-slope, hip and half-hip, broken. The simplest option is gable rafter system attics. Its advantage is simple and reliable design, capable of withstanding heavy loads. However, there are also disadvantages - a simple form does not allow you to create interesting design, which, however, is compensated by the addition decorative elements. Another more significant drawback is the limited internal space, which is significantly less than in the case of a sloping roof.

Idea You can get rid of the lack of space by building a semi-attic - that is, a room with side walls 1.5-1.8 meters in height. This will increase the internal volume while maintaining the advantages of the double design. pitched roof.

The drawing shows an example of a half-attic type mansard roof with walls 1.8 m high

The most interesting from an architectural point of view is the rafter system of the sloping mansard roof. It allows you to show your imagination, of course, subject to compliance building codes and, above all, strength characteristics. This design can have a regular and asymmetrical shape. The configuration is selected based on the characteristics of the house and the layout of the interior space of the attic. In some cases, the rafter system of the attic roof allows you to create a rather interesting interior space, especially if it is possible to plan a second light or mezzanine. It is important to use the volume as fully and efficiently as possible - this is not an easy, but very interesting task, which allows you to increase the usable area and make the house more comfortable at a relatively low cost.

Advice Since space is limited where the attic floor meets the roof, it is advisable to organize storage areas, install furniture, and lay utility lines.

Spaces near the walls of the attic are best used for installing convenient cabinets, shelves and built-in furniture

Elements and components of mansard roof rafter systems

Rafter system- this is the basis of the roof, its skeleton, on which they are mounted roofing pie and interior lining of the attic. It is often used as a basis for laying engineering systems and communications. In turn, the rafter system of the attic roof consists of component units and elements, a set and mutual arrangement which ensures the transfer of wind and snow loads from the roof to load-bearing walls building:

• rafters (hanging and layered);
• Mauerlat;
• purlins (ridge and side);
• connecting elements (struts, spacers, diagonal connections).

The loads acting on the rafter structures of mansard roofs are quite large and reach an average of 200 kg/m2. However, in each specific case this is determined based on the characteristics of the roof structure, as well as the wind and snow loads present in the area. In any case, the rafters must be guaranteed to withstand these loads and have the necessary strength margin that can withstand very strong winds or heavy snowfall.

When calculating the load on the rafter system, it is very important to take into account the likely amount of precipitation and wind strength

The parameters and main components of the mansard roof rafter system are determined by calculations. Calculations make it possible to determine the length, profile and cross-section of each structural element and the features of how the parts are connected to each other. The strength of the entire structure largely depends on the strength of the connection of the nodes of the rafter system of the attic roof. The most common types of connections are tongue-and-groove, screw, bolted and welded. The choice of connection type depends on the design loads, the material used and design features.

Calculation and drawing of the mansard roof rafter system

Having chosen the type and determined the design of the attic, it is necessary to calculate the rafter system of the attic roof. It should be taken into account that the rafters not only provide the strength and reliability of the roof, but also shape the internal space of the attic. It is allowed that part of the area will have a low ceiling height. Furniture is usually placed there, or used to organize storage areas. Despite some restrictions, the interior space should be spacious enough and not cause discomfort.

The first stage of design is the selection of the truss system for the mansard roof. The diagram determines the type and location of the rafter system elements. In particular, the type of rafters is determined: layered or hanging. The difference between these elements is as follows: layered rafters on the attic floor rest on side walls or other supports. Hanging rafters form a single, rigidly interconnected structure. Depending on the width of the span, the truss system of the attic roof can be reinforced with additional connections.

The diagram shows the main elements and parts of the attic roof rafter system and their relative positions

Next, it is necessary to perform calculations that take into account wind and snow loads that will act on the roof. The material, cross-section and distance between the rafters of the attic roof depend on these parameters. It is recommended to use the so-called “safety margin”. This means that the obtained result must be multiplied by a multiplying factor, thereby guaranteeing increased reliability of the attic rafter system. Taking into account the characteristics of operation, the value of this coefficient is taken from 1.5 to 3.

Important When making calculations, it is necessary to take into account the weight of the roofing system. In particular, when using ceramic tiles The cross-section of the timber for the rafters must be at least 70x150 mm, with a pitch of 0.5 m.

Quite often, the rafter system of an attic roof is created from wooden structures. It is recommended to choose wood that has high strength and at the same time minimally susceptible to rotting. The best option larch can be considered, however, it is possible to use cheaper wood with sufficient strength. In this case, more thorough treatment with antiseptic compounds is necessary. It is desirable that these compositions also have fire retardant components.

The rafters of the attic roof must be treated with a special antiseptic to prevent wood rotting

However, it is not always possible to use wood to make rafters. For heavy loads, the use of timber with large profile sections, or a significant reduction in the distance between elements. This leads to a significant weighting of the entire structure of the attic roof and, as a consequence, to the need to increase bearing capacity attic walls. In this case, they often use metal rafters mansard roofs.

The results of the calculations are reflected in the drawings, which indicate all the design decisions made for this attic truss system. If the work is done independently, then instead of a detailed drawing, it is permissible to develop a simplified sketch of the rafter system of the attic roof. In this case, the sketch must have all the information and parameters necessary for assembling and installing the rafters.

An example of a schematic drawing of an attic rafter system indicating the main parameters and distances

Construction of an attic rafter system using the example of a gable roof

The design of the attic roof rafter system depends on the type of roof chosen for the house project. The simplest, and at the same time reliable and effective, can be considered the classic gable roof. Of course, it looks simple compared to complex, broken roofs, but at the same time it contains many basic elements and parts characteristic of all types of mansard roof truss systems.

The rafter system of a gable mansard roof consists of several main parts and elements. In general this is:

• Linear parts and elements - beams, columns, rod systems;
• Planar parts and elements - slabs, panels, floorings;
• Spatial parts and elements - shells, vaults, volumetric elements.

In practice, not all parts and elements of the mansard roof rafter system are used. In particular, for a gable roof, rafters, crossbars, ties, struts and struts are used. Their dimensions and relative position are determined during design. When assembled, all these elements form the truss of the mansard roof truss system.

Six examples of roof truss design, indicating the height of the ridge and the location of the rafters

The truss is the most important part of the rafter system of the attic roof. The number of trusses depends on the length of the facade and the selected installation step. The type of truss and the installation pitch are interrelated quantities; the more complex and durable the spatial structure of the element, the larger the step can be used during installation. In turn, an important element of the farm are the rafters for the attic, or, as they are also called, rafter legs.

Rafter legs – essential element trusses, the distance between which determines the stability of the roof

The video attached to the article talks in sufficient detail about the rafter system of the mansard roof. From it you will learn about all the intricacies of constructing a rafter system and performing installation work. Options for roofing systems from a simple gable to a more complex - broken one - are considered. By following the instructions and recommendations in the video instructions, even a novice master can understand the features of this work and perform it independently.

Installation of the attic roof rafter system

The work of installing mansard roof rafters is also called raftering. This is a set of works on marking and installing rafters. At the same time, work is also carried out to remove the horizontal ridge and trim the pediment. You can do the raftering yourself. A good guide The video instructions below can be used for this.

The installation of a mansard roof truss system has many features, many of which are unknown to novice craftsmen. The frame must be installed on hydro- and heat-insulating material. This increases service life and reduces heat losses. Another common mistake is covering elements protective compounds after installing them. Treatment with an antiseptic must be carried out before installation, then the entire surface will be treated and the rafters will last longer.

Note to the masterWood for rafter work must be pre-dried; its optimal moisture content is approximately 18%.

The quality of fastening of the attic roof rafter system must be given special attention. You can correctly complete the attic project, purchase quality materials and a professional tool, but if the connection of the rafter system parts is performed poorly, then after some time it will be necessary major renovation. The choice of fasteners is a separate section of the project, in which the length and diameter of the hardware is determined.

To assemble the attic roof rafters, you must use galvanized fasteners the right size. An attempt to save on fasteners does not give a significant result, but it contributes to the emergence of serious problems during operation. The distance between fasteners is selected in proportion to their sizes. The fastener pitch should not be very small, so as not to reduce the strength characteristics of the part itself.

Installation truss structure gable mansard roof wooden country house

The first truss is mounted from one of the ends, while checking the correct installation vertically and horizontally. Then, from the other end, a second truss is mounted, and its verticality and horizontality are also verified. Two construction cords are pulled in parallel between the trusses, which will serve as a guide for installing the intermediate rafters of the attic roof.

Advice To temporarily secure trusses, you can use struts made from substandard lumber or scraps.

After all the trusses are installed in their places, the installation of side and ridge girders begins. Having assembled the rafter system of the attic roof, you can move on to other types of work: filling and covering the gables, installing a roofing pie, heat and sound insulation, interior lining and finishing.

An attic, which makes it possible to effectively use the floor space of a private house, is a rather complex design. As a rule, homeowners entrust its construction to experienced roofers. But if you are skilled in carpentry and are not afraid of difficulties, then you can certainly cope with the task yourself. The first step is to receive theoretical knowledge about how an attic roof is calculated and built with your own hands according to individual drawings. This information, presented in the form step by step guide, you will find in this article.

Choosing a roof design

To construct an attic floor instead of a conventional attic, the following types of roofs are suitable (shown in the diagram below):

• regular gable with a slope of 45° or more (steep);
• broken roof;
• four-slope, half-hip.

Note. As can be seen from the diagram, various half-hip roofings are complicated gable roofs, so there is no point in considering them separately. In terms of design, the multi-gable structure shown in the photo is of interest, but its construction requires considerable experience.

The gable mansard roof is the simplest to implement and is economical in terms of material consumption. But you will have to pay for this with a smaller usable area and sloping walls of the attached floor, which do not allow the placement of tall furniture. This will not be a problem if you plan to set up a bedroom in the attic - the beds will easily stand near the longitudinal walls. Another way to solve the issue is to raise the rafter system to the required height, as shown in the drawing below.

Roofing with broken shapes is the most popular option, since it allows you to create full-fledged living rooms upstairs. If you do not provide protruding windows on its slopes, then in terms of installation technology such a roof is not much more complicated than a gable roof, although the consumption of building materials will increase. To make your choice easier, we suggest considering and comparing the 3 most common options for an attic superstructure for a private home standard sizes 6 x 6 m:

1. Steep roof with two slopes inclined at an angle of 45°.
2. A broken structure, where the lower rafters are inclined at an angle of 60°, and the upper ones - 30°.
3. The same as option 1, only the trusses are raised to a height of 60 cm, and the rafter legs are at an angle of 37.5°.

For convenience, we depicted all three structures on one drawing, which can be taken as a basis for future construction.

Note. A board with a cross section of 50 x 150 mm was taken as the main building material for the manufacture of rafters and other frame elements.

To choose the best of the three options, we suggest studying the comparative table, which presents the parameters of attic rooms based on 1 linear meter building length.

Knowing the length of the roof slopes indicated in the plate, you can approximately estimate the consumption of building materials for the frame, covering and insulation. The following table allows you to evaluate total area rooms on the second floor when implementing all 3 solutions in private houses of different sizes.

Calculation of the rafter system

The rafters of a do-it-yourself attic must withstand the following loads throughout its entire service life:

• own weight;
• weight of roofing and insulation;
• maximum gusts of wind for a given area;
• snow cover pressure.

Reference. When the roof slope is more than 45°, snow practically does not stay on it, and at 60° it is not taken into account at all in the calculations. But wind pressure increases due to the height of the structure and its position, which is close to vertical.

The result of the calculations should be 2 parameters - the cross-section of the rafters with beams (otherwise known as tie rods) and the pitch of their installation. It is a mistake to think that the size of the wooden beams of the roof grows along with the loads on it. Maximum structural rigidity is achieved through the use of trusses made from logs with a diameter of 120-200 mm or lumber with a thickness of 40 to 200 mm, installed in increments of 50-120 cm. If you are not a civil engineer, you will not be able to determine these values ​​more precisely, since the methodology quite complicated.

Online calculators posted on the Internet do not solve the issue, because their calculations still need to be checked. The solution is this: use ready-made data that has been calculated a long time ago. To do this, you will need table No. 1, which shows the cross-sections of rafter legs at different lengths and loads:

We will explain the calculation method with an example. Let’s assume that the snow load on a flat surface (projection of a pitched roof) in your area is 100 kg/m², the slope is 60°, the span length is 4.5 m (before the strut), the pitch of the rafters is 120 cm. The roofing is slate. We count:

1. Real weight of snow cover: 100 x 0.32 = 32 kg/m². The slope coefficient of 0.32 is taken from Table 2 below.
2. Specific gravity slate covering with a regular profile is 25 kg/m².
3. Total specific gravity – 32 + 25 = 60 kg/m².
4. We calculate the specific gravity per 1 linear meter of rafters, multiplying 60 kg/m² by an installation step of 1.2 m. We get 72 kg.
5. We return to table No. 1 and select the cross-section of the beam according to the span length. We accept a load of 100 kg per 1 line of rafters (with a margin). A log with a diameter of 140 mm, a board 40 x 200 mm and other materials whose dimensions are in the same horizontal line are suitable.

Reference. When installing a sloping mansard roof, 2 types of rafters are used - layered and hanging. On gable roof Only hanging ones are used; the difference between them is shown in the diagram.

The last table No. 3 will help you correctly determine the installation interval of roof trusses:

The proposed method is suitable for small houses rectangular shape dimensions 6 x 6 m. To build a mansard roof on a large cottage, it is strongly recommended to contact specialist designers for calculations.

Frame making

The simplified method presented below involves the installation of an attic sloping roof in 2 stages: assembly of roof trusses on the ground and subsequent installation on finished walls lumber or log house. The structural material is boards with a section of 15 x 5 and 10 x 5 cm with a standard length of 6 m.

Start of assembly - formation of the upper chord of the rafter system

The technology looks like this step by step:

1. Prepare the beams of the lower chord of the truss, taking into account roof overhangs of 25-27 cm on each side. If the length of the beam is not enough, it needs to be increased using an overlay of the same section, nailed.
2. Lay the beam on the ground and attach vertical posts to it with corners to form the walls attic room. Install ceiling beam and a support for the ridge (headstock), then attach two boards to it and the corners of the frame hanging rafters for marking, as done in the photo.
3. Cut the elements into place and secure them. From the remaining parts of the boards, make layered (lower) rafter legs in the same way and nail them to the frame. The farm is ready.
4. Make the remaining trusses using the same method.

Advice. As a rule, windows or doors to the balcony are provided on the front gables. It is also convenient to make racks and belts for their installation on the ground, as well as to cover the openings with clapboard.

How to quickly and accurately assemble rafters for the attic is described in the video:

The finished frames are lifted onto the walls and fixed in place one by one, starting from the first gable. To prevent it from falling, install spacers and nail them to the walls of the log house. The second and subsequent trusses are placed in the design position and connected to each other with boards.

After placing the rafters, they must be secured to the walls in the following ways:

• staples to the second top crown of logs or beams;
• on steel corners and galvanized screws, as shown in the photo.

Note. Installation on brick and other solid walls is carried out using a Mauerlat - wooden beam, laid on bearing structures along the entire perimeter of the building. In turn, the Mauerlat is mounted on studs or anchor bolts, and a waterproofing layer of roofing felt is placed between it and the stone wall. Mounting unit looks like that:

The next step is laying on top of the rafter system diffusion membrane– a film that protects from wind and precipitation, but allows water vapor from the insulation to pass through. Roll out the first sheet at the bottom of the roof and secure it to the boards with a stapler, lay the next one with an overlap of 10-15 cm. When you have covered the entire roof, nail the sheathing boards. The installation is shown in more detail in the video:

Lay on top of the sheathing roof covering– slate, metal tiles and so on. The technology of installation and fastening depends on the selected material.

Attic insulation

Since the attic space is planned as a residential space, it should be well insulated. Of the thermal insulation materials, mineral wool works best with wood because it allows moisture to pass through and allows it to “breathe.” The layer thickness is at least 150 mm, and in northern regions– up to 300 mm. Insulation is carried out in the following order:

1. Cut the mineral wool slabs and insert them spaced between the rafters.
2. To insulate the gables, nail additional posts and lay insulation between them in the same way.
3. If the width of the rafter legs is not enough to create thermal insulation required thickness, after laying the first layer, nail the horizontal bars of the counter-lattice to them. Insert the second layer slabs between them.
4. Cover the insulation from the inside with a vapor barrier film, laying it with an overlap of 15 cm and gluing the joints with aluminum tape.
5. Nail the sheathing strips on top for cladding with plasterboard or other finishing material.

Important point. When laying insulation, make sure that between it and windproof membrane a ventilation duct of 3-5 cm remained. Through it, the moisture formed in the mineral wool due to the occurrence of the dew point will be removed.

The process of thermal insulation of the attic is clearly shown in the next video:

Conclusion

Construction of an attic roof is a labor-intensive task and you cannot overcome it alone. Most work needs to be done with an assistant, and lifting trusses will require 3 people. Also, the success of your event largely depends on the correctness of the initial calculations. If the calculation methodology confuses you, and there are no smart engineers nearby, consult with experienced craftsmen– roofers, whose competence there is no doubt. They will suggest the right solution and, perhaps, tell you about the details of installing such systems.

Design engineer with more than 8 years of experience in construction.
Graduated from Eastern Ukrainian National University them. Vladimir Dal with a degree in Electronics Industry Equipment in 2011.

Related posts:

Using all possible space, giving the house originality and significantly reducing heat loss through the roof - these are the tasks that the attic solves. If there is a certain margin of safety at the foundation, in this way you can turn a one-story house into a two-level one. Another attractive thing is that you can build an attic roof with your own hands even without special construction skills. It is important not to make a mistake with the choice of materials and do everything according to the rules.

Windows on a regular floor are located in the walls. In attics there are no or almost no walls. They are replaced by a roof. That’s why windows are made special: they not only have to let light in sufficient quantity, but also withstand wind and snow loads, which are much greater on the roof than on the walls.

Dormer windows

When planning an attic, you should take into account the recommendations of SNiP. They recommend making the window area no less than 10% of the floor area. So if the attic is divided into several rooms, each should have a window.

Of all the methods shown in the photo for installing skylights with an attic, inclined installation is the easiest to implement. In this case, it is necessary to ensure the proper degree of waterproofing of the junction, and also to use special models with reinforced frames and reinforced glass - the load on the surface can be significant.

Advantages of a sloping roof window:

• more light, less sharp boundaries of light and shadow;
• the roof surface remains flat, its relief is not complicated;
• relatively easy installation.

When planning such a window, it is necessary to remember that its area increases with increasing angle of inclination. At what height is it more convenient to install such a window and how its height increases in centimeters depending on the inclination, look at the photo.

The steeper the slope relative to the floor, the smaller the window height should be.

The width of the window frame should be 4-6 cm less than the pitch between the rafters. Then it can be easily installed without disturbing the structure of the frame. If the window is wider, it is necessary to make a reinforced beam above it and calculate the load.

If you need to have a larger window, it is easier to place two narrow ones side by side. They look no worse than one big one, and there will be fewer problems.

When installing a dormer window, the roof geometry becomes more complicated: a valley appears on top and on the sides. Because of this, the rafter system becomes more complex both during planning and during assembly. The complexity of laying the roof covering also increases. All valleys are the places where leaks are most likely to occur. Therefore, everything needs to be done very carefully. In regions with a lot of snow, it is advisable to install snow guards over such windows so that they are not blown away in the event of a sudden meltdown.

Installation of a vertical dormer window in an attic roof

The advantage of such a window: you can stand near it full height. But they let in less light, the terrain becomes more complex and the roof becomes more problematic.

A recessed window is usually used if there is access to a balcony through it. In other cases, this method of arrangement is not the best option: little light gets in, the shadows turn out to be very deep, which is tiring for the eye, the geometry also becomes more complex, although not to the same extent as in the previous version.

The easiest way is to make a window at the end of the attic. In this case, a reinforced frame or reinforced glass is not needed. Just high-quality glass is quite enough. It is this option that can most often be seen in country attics: this is the most inexpensive option, which you can easily implement with your own hands.

Rafter system

At self-construction In private houses with an attic, a broken roof is usually chosen. It allows you to get a room of significant area, larger than under a gable.

With the same width of the base (of the house), the attic space under a sloping roof is larger than under a regular gable roof. The rafter system is becoming more complex, but a gable roof with an attic under a sloping roof is still more popular

The design of the sloping mansard roof is such that the overhangs can be lowered quite low, giving the house an interesting look. But a long roof overhang is not only decorative role. They also cover the upper part of the wall from precipitation and divert the bulk of the water away from the foundation. Although when planning you need to keep in mind that in strong winds they increase windage. Because of this, it is necessary to use more powerful boards and beams. Therefore, the size of the roof overhang is chosen based on several considerations, the main one of which is weather conditions.

Tilt angle

Depends on roofing material, but most of all - from the region and weather conditions. The classic version is shown in the figure: the lower slopes in relation to the plane of the attic floor are inclined by 60°, the upper slopes by 30°. Based on these data and the parameters of your building, you can calculate all lengths. Just take into account that according to SNiP, the ceiling height in the attic cannot be less than 2 m. Then, by definition, this is an attic. A person will feel comfortable if the ceiling is raised to a height of at least 2.2-2.3 m. Based on this, according to the rules of geometry, calculate the required lengths.

At classic version load from precipitation on side surfaces may not be taken into account. Precipitation can only be retained on the upper part, the angle of inclination of which is less than 45°.

In general, the inclination of the side surfaces usually varies between 45° and up to 80°. The steeper the slope, the greater the windage it has, this must be taken into account: in regions with strong winds it is better to make flatter roofs. Then wind loads will be perceived much better.

Types of rafter systems for sloping roofs

The design of a sloping mansard roof is one of the options for the rafter system (the most common)

To make the frame of a sloping roof with your own hands, they most often use pine lumber, grade no lower than 2. The choice of cross-section of timber and boards depends on the size of the roof, the selected roofing covering (its weight), wind and snow loads in the region, and the pitch of rafter installation. All these parameters are taken into account in the calculation. The methodology is prescribed in SNiP 2.08.01-89 and TKP 45-5.05-146-2009.

One of the options for constructing a frame with hanging rafters

The figure above shows a drawing of a frame with hanging rafters. It can only be implemented if the base of the upper triangle is no more than 4.5 meters (in this case, this is the width of the attic room). If more, you will have to make layered rafters, which should rest on the load-bearing wall in the middle (the attic will be divided into two parts by a row of beams).

Another version of the upper part is shown in the photo below (the picture is clickable). In this case, the side rafters are reinforced with struts. They significantly increase the rigidity of the system.

There is a second way to achieve a similar effect - to establish contractions - in the figure they are only outlined with barely visible lines. The length of the side rafter leg is divided by three, and contractions are established in these places. They will be needed if the roof covering will have a significant weight.

Option for installing a sloping roof truss system - with struts that increase the rigidity of the system

For a building that is small in size, the roof frame can be generally simple: at the top there are two hanging rafters, a tie rod, floor beams, racks and side rafters (pictured below).

Construction of a rafter system for a broken mansard roof for small house

How to calculate a sloping roof

The attic sloping roof of a small house (no more than 6-7 meters wide) has been built so many times that, based on experience, we can say what materials should be used. Many parameters are dependent on other materials. For example, the installation step of the rafters is tied to the parameters of the insulation. To ensure that there is as little waste as possible during insulation and installation is simpler, it is necessary that the distance from one rack to another be slightly less than the width of the insulation (20-30 mm). So, if you are going to use mineral wool, its width is 60 cm. Then the racks need to be installed so that the clearance between two adjacent ones is 57-58 cm and no more.

The width of the board for the rafter leg is again determined based on the insulation. For central Russia required thickness basalt wool is 200-250 mm. That's not all. In order for the thermal insulation to dry, a ventilation gap of 20-30 mm is required (without it, condensation will gradually rot the wood and render the mineral wool unusable). In total, it turns out that the minimum width of the rafter leg should be 230 mm. The thickness of the board is at least 50 mm. This is in regions with light winds and not very heavy snowfalls. To summarize, for all rafters - ridge and side - a board of 230 * 50 mm is required.

If lumber with such characteristics turns out to be too expensive, it will be possible to do the insulation in two directions: partly along the rafters, partly, filling the sheathing, across. You can lay a minimum of 100 mm of basalt wool, therefore you can take standard board 50*150 mm and leave a 50 mm ventilation gap, or order a non-standard 130*50 mm. It's up to you to see which is more profitable for the money.

For racks and beams, it is better to take a beam of at least 80 * 80 mm, better - 100 * 100 mm. Especially in areas with difficult weather conditions - heavy snowfalls or strong winds.

Order a more accurate calculation from specialists. This is a long process consisting of collecting loads from the roofing material, the structural elements themselves, wind and snow loads. After which, according to a certain formula, elements are selected. More detailed information For information on how the calculation is carried out, see the following video.

Do-it-yourself mansard roof: installation procedure

The design of the Mauerlat on mansard roofs is no different from the standard version. If or logs, you can use the upper crown as a mauerlat. It is only pre-treated with impregnation with high protective properties.

If the wall is made of foam blocks, a reinforced monolithic belt. On a brick wall or made of shell rock, others similar materials, the device of such a belt is not necessary. Waterproofing is laid in two layers on the wall, and on top is a timber treated with an antiseptic - 150 * 150 mm or a log. It is secured with embedded studs.

When assembling all elements, long nails are used - at least 150 mm long. In the most critical places, it is better to connect three or more elements using bolts or studs with double-sided threads. It is advisable to strengthen all joints with steel plates or corners.

First way

Installation of attic roof rafters is done in two ways. First: they assemble the parts on the ground, then lift them up in finished form. There, the outer structures, which will become pediments, are put up first. They are placed vertically and secured. It is often more convenient to secure them with long bars nailed to the wall (temporary). The following are inserted into the prepared recesses in the Mauerlat (they are made with the required step): assembled structures. They are positioned strictly vertically and carefully secured. If necessary, additional temporary spacers are installed to fix them in the desired position. Side beams are installed.

How to build a sloping roof in this way and assemble the nodes, see the video below.

Second way

The second method - the construction of a sloping roof is carried out sequentially by assembling elements directly on site. This method is more convenient if the structure is large and when assembled it can only be lifted using special equipment (crane).

First, the floor beams are laid. Stands and ties are attached to them, and temporary spacers are installed to hold them in the vertical direction. Next, the upper and side rafter legs are assembled, and the tie rods and jibs are installed.

During installation, the following sequence of actions is observed: first, the outermost elements are installed and adjusted to the desired position, and securely fastened. If necessary, use temporary spacers. A fishing line, rope, and cord are stretched between them, which will serve as a guide for the installation of all subsequent elements. This simple move allows you to get the ideal geometry (don’t forget to check the slope angle, verticality or horizontality).

On top of the racks, tie-downs are attached - bars, to which the side rafters are then fixed and onto which the tie-down of the upper triangle is installed. The ties are secured using metal corners. Since the beams are long, they sag. This can be eliminated later - after installing the upper rafter legs - using vertical beams fixed or adjustable height. And temporarily they can be supported with racks (so as not to pull the entire system).

To make it easier to maintain the desired angle when installing the side rafter legs, templates are made according to which cuts are made. But since the geometry of buildings built with your own hands is rarely ideal, adjustments may be necessary. To check the resulting angle of inclination, another template is knocked down from several boards, which is used to check the correct installation.

If the standard length of lumber - 6 meters - is not enough, either order the required length (expensive) or increase it. When building up, two boards measuring at least 0.6 meters (30 cm on each side of the joint) are nailed to the joint. They are nailed on both sides or bolts are used.

A reliable way to build rafters. The length of the “patch” is at least 60 cm

After installing the side rafters, all that remains is to install the top ones. A template is also made for them, pre-cut on the ground, and installed on top.

The top part can be made in different ways. Its structure depends on the width of the base. How to make it, look at the photo below.

Since the structure of the attic sloping roof does not provide for the presence of a ridge, a beam is placed in the middle to tighten it, to which the slopes are attached, fixing the triangle in the required position.

Nodes and their drawings

When installing a rafter system, questions may arise regarding the assembly of nodes—the intersections and connections of several structural elements. In the photo you see drawings of key connections.

The second option for connecting the side layered rafters and the upper triangle. Bolts are used for more secure fastening.

How to make a do-it-yourself fastening of the upper tee and rafter leg on an attic roof

Methods for attaching rafter legs to the mauerlat or, as in this case, to the side beam are shown in the figure below. To make it easier to mount a heavy element, a thrust board (bar) is nailed to the bottom of the rafter, which limits its movement: the board rests against the edge and does not allow it to sink lower.

The attic is an excellent opportunity to increase the total and usable area of ​​the house. It is installed in the attic and is quite suitable for living, provided that it is designed correctly. The rafter system of the attic roof, drawings of which can be found in this material, is the basis of the entire structure. And it is precisely this that needs to be given the closest attention when designing.

Mansard roof rafter system - drawings

An attic is a room located directly under the roof. Its facade is partially or completely formed by the roof surfaces (according to SNiP 2.08.01-89).

SNiP 2.08.01-89. Residential buildings. Downloadable file (click the link to open the PDF in a new window).

It is a full-fledged residential floor; there can be one or several rooms, depending on the design parameters.

On a note! The word "attic" comes from France. It was the French architect who, in 1630, came up with the idea of ​​usefully arranging attic spaces. And this man’s name was Francois Mansart - hence the name of this type of superstructure.

The features of attic roofs are not only special design rafter system, but also the need for detailed consideration of other aspects - insulation, moisture and vapor barriers, etc. Since the attic usually increases the load on the foundation and walls of the building itself, all its elements are mainly built from lightweight materials. That is, it is recommended to use wood to create a rafter system; lightweight materials are used as insulation.

The attic can be of impressive size and occupy the entire area of ​​the building, but within its walls. Sometimes it is installed only on part of the floors, and then the rear ones are covered by a regular roof.

Very often, the attic is used in individual construction, because it is an opportunity to increase the living space of the house and make it warmer (heat loss through the roof is reduced by an average of 7-9%). And the costs of arranging an attic will be much less than building a full floor.

In general, building an attic is not very difficult and you can cope with the task yourself. The main thing is to correctly calculate wind, snow and other types of load.

Prices for timber

Types of attics

The design of the attic will directly depend on what shape the roof is supposed to be installed. After all, part of the walls of this room will be formed by the roof slopes. Depending on this, there are several types of mansard roofs.

Perhaps the simplest option for arranging the roof itself and the attic floor. This roof has only one slope, which rests on the multi-level walls of the building. Thus, the slope angle is formed. By the way, it should not go beyond the strictly limited limits - 35-45 degrees (if the slope is less, then snow will constantly accumulate on the roof). winter time, which will significantly increase the load on the entire house and will cause the installation of additional supports in the already small attic). The rafter system here is extremely simple.

On a note! The rafter structure will not require additional supports if the distance between two walls located opposite each other does not exceed 4.5 m.

Such attic roofs look original, despite the simplicity of their design. Usually, a fairly large window is made on the side of the high wall of the attic, which allows you to get a well-lit room.

Mansard roof with two slopes

This option is also relatively simple to implement and is therefore widely used. The main thing is that the height of the roof itself allows you to arrange a living space underneath it. The rafter system of this roof looks like a regular gable roof; it can be asymmetrical or symmetrical depending on the location of the ridge.

The gables are usually simple and straight, and the room inside will have the shape of a trapezoid or square (the latter option is only possible if the attic space is spacious enough). The height of the ceilings near the walls should not be more than 1.5 m; above that there is a sloping cone-shaped ceiling.

Main disadvantage gable roof in terms of arranging the attic, this is a loss of most of the free space. That is, it is cut off by the roof slopes lion's share premises. Of course, this free space is usually used as a storage space, but this aspect has a very significant effect on the size of the attic.

Broken mansard roofs

In fact, this is also a kind of gable roof, but its slopes have two parts, located at different angles relative to the ceilings. Due to this, you can get a fairly spacious attic floor, which will be equal in area to almost a full second floor (it will be only 15% smaller than the lower floor). The height from ceiling to floor will be the same throughout the attic and will be about 2.2-2.3 m.

Broken mansard roof - drawing

However, this design involves the construction of a rather complex rafter system. And not every novice master will be able to cope with this task. However, despite this, the sloping roof option is quite common.

Hip roofs, mansard roofs

Such a roof involves the creation of the most complex type of rafter system, requiring the most accurate and painstaking calculations. The surface of the roof itself will have a fairly large area, which is why you will have to spend a lot of money on other materials - insulation, hydro- and vapor barrier films etc. But in general, the attic turns out to be quite spacious, although parts of the usable area are cut off.

But such a roof has maximum resistance to snow and wind loads. The overhangs can be quite large and will be ready to protect the walls of the building from the effects of precipitation. Such attic roofs look very attractive.

Attention! When arranging a hipped roof, it is important to take care of the need to strengthen the layered rafters - they are the ones who experience the maximum load.

Attic roof rafter system

When settling in mansard roof the rafter system can be made from elements of layered or hanging type. In the first option, the rafters are installed so that they form a triangle with even edges. In this case, the support is carried out on the mauerlat fixed along the perimeter of the walls, on additional supports installed under the rafters, and the connection of two boards in the ridge area also serves as a support point.

When installing hanging type rafters, supports in the form of additional beams are not provided. They rest only on the walls of the house. Pulls may be used. In this case, the rafters themselves work in bending and compression.

Hanging and layered rafters - example drawing

Creating a rafter system when building an attic is a primary task. It is first important to correctly calculate it and take into account all the subtleties of its construction. To understand what will be discussed, you need to familiarize yourself with its main elements.

Table. Main details of the rafter system.

Element	Description
Mauerlat	This is a beam (or board) that is fixed on the upper end part of the load-bearing wall of the building. The rafter legs will be attached to it. It plays the role of a support and will transfer the entire load from the roof to the walls of the building.
Rack	Any vertically located beam that acts as a support for the rafter legs.
Floors	This is a series of beams laid horizontally to form the floor of the attic floor. They also play the role of the ceiling of the first floor of the building.
Rigel	These beams are located horizontally and are additional reinforcing and supporting elements for the rafters. May also be called "puffs".
Rafters	Also called “rafter legs”. They form the frame of the roof and give it its shape. Moisture-proof materials, sheathing and roofing will be attached to them on top.
Lathing	Many blocks or sheets of plywood that are attached to the rafters. It is on them that the roofing material will be directly fixed.
Suspension	A board that helps distribute the load. Installed under the bolt or tightening.
filly	The board that forms the roof overhang is fixed at the bottom of the rafter leg.

Prices for construction boards

Construction boards

Required calculations

In order to avoid mistakes when designing an attic, it is important to carry out a number of preliminary calculations. Depending on the chosen type of rafter system and type of roof, they may differ. The easiest way is to use some special program, but you can try to do all the calculations manually.

It is important to determine the area of ​​the final roof, the dimensions of the attic, and the width of the floors. The calculation is made based on the following data:

• length and width of the house;
• precipitation volumes in winter and summer period(this will help determine the required roof slope angle);
• the width of the joints between parts of the floors.

An example of calculating the pitch of rafters in the program "Rafters 1.1"

Let's consider an example calculation: the length of the house is 12 m, the width is 3 m. The amount of precipitation in the area indicates that the required roof slope angle should be about 40 degrees. The calculation is made using the formula Hk = L x tgA, where Hk is the required height, L is ½ the width of the building, tgA is the tangent of the angle. Total: Nl = 3/2 x tg40 = 1.26. This means that the recommended roof height should be 1.26 m.

On a note! Most often, when installing mansard roofs, owners opt for broken rafter systems. The methodology for calculating parameters in this case can be found in SNiP 2.08.01-89 and TKP 45-5.05-146-2009.

The housing problem, for many, has become the number one problem. And if it is not possible to increase the living space in width, then you have to look for other ways and arrange unexpected premises for housing. One of possible solutions became a mansard roof, in the internal space of which premises adapted for living are organized.

Today this solution is very popular. And this is understandable, because the rafter system of the mansard roof in its modern design allows you to find the most rational option design that allows you to achieve convenient forms rooms under a reliable and, therefore, durable roof.

Mansard roof rafter system: photo of the design of the sloping roof load-bearing system

Rafter structures for mansard roofs

The attic roof, like any roof structure, consists of two systems:

• fencing, including roofing pie, hydro-, steam- and thermal insulation;
• power, which includes, firstly, the rafter system, and, secondly, the power plate.

Mauerlat distributes the loads experienced by the rafters of the attic roof onto the load-bearing walls

The rafter system of an attic roof is its power frame with many types and varieties. In addition, it is considered the most optimal due to its relative simplicity and low costs for increasing internal space.

On a note: For example, square meter The usable area of ​​an 8x10 attic roof costs about 70–75 dollars. That is, equipping an attic of 60–65 m2 is much cheaper than building the same area from scratch.

Classic attic - rafter system

Being the basis for the attic roof, the rafter system, in addition to its weight, must also withstand the design loads from wind and snow. If we also take into account that this is the link that binds together roofing slopes, floor beams, walls and ceiling, then it is obvious that the calculation of the rafter system of the attic roof must be carried out carefully and competently.

The relationship between the usable area of ​​the attic and the angle of the roof

The design and dimensions of the attic depend on many parameters, in particular on the width of the house and the height of the room. Therefore, you first need to prepare the appropriate drawings and work out all the connections. The diagram of the attic roof rafter system must contain comprehensive information about

• interconnected height, pitch and cross-section of the racks;
• the length and slope of the rafters;
• location of roof windows;
• sheathing size
• material for gable cladding.

Important: special attention requires fastening the rafters to the Mauerlat and the latter itself to the wall of the building. With any serious miscalculation, the attic roof may come off or collapse in the event of a hurricane wind.

System calculations can be significantly simplified if you use tables that present ready-made Constructive decisions assemblies of the supporting system, indicating fastening methods and main dimensions.

The design of the attic roof truss system

There are two types of rafters for the attic.

Types of rafter systems

• Hanging ones have two supports, say, walls, columns, etc. They simultaneously work in bending and compression, thus transferring horizontal forces to the load-bearing walls. The simplest hanging ones roof trusses consist directly of rafters and a lower belt - a tie (crossbar), resting on the mauerlat. Such a system justifies itself if the supporting walls are no more than 6–6.5 m apart from each other.
• Layered rafters have additional support in the center, for example, interior wall or a column, so they only work in bending. This design reduces the loads that load-bearing walls are exposed to. The layered supporting system can cover a distance of up to 10 m, and when installing additional purlins and racks - up to 16 m.
• The load-bearing system of the attic floor often includes both of these types

The simplest attic rafter system

As can be seen from the top figure, the load-bearing system of the attic roof includes lower rafters (sloping), upper (hanging) rafters, vertical posts, a connecting horizontal crossbar and a ridge beam. For a small attic availability ridge beam not necessary. It can be completely replaced with a continuous sheathing, which creates a diaphragm of rigidity.

As you know, the most rigid figure in geometry is a triangle, therefore ridge and side trusses, made in a triangular shape, can provide rigidity to the system in two directions - lateral and vertical.

The design of the supporting system for the attic

As for volumetric rigidity, for this purpose struts are installed, which also form a triangle together with the vertical posts.

Materials in the construction of rafters for the attic

The most popular materials for attic rafter systems are wood and metal.

As a rule, the system is assembled from solid wood species such as pine and spruce. Beams and boards must be treated with antiseptics and fire retardants, which protect them from fungus, mold, insects and fire.

Glued laminated timber is often used for these purposes, which has certain advantages over regular timber:

• it is more durable and lightweight;
• allows you to increase the distance between the rafters of the attic roof without loss of rigidity;
• does not require additional impregnation.

Metal rafters for mansard roofs

To give extra strength attic structure use steel thin-walled structures. They are distinguished by durability, endurance and ease of assembly, they are fire-resistant, but, unfortunately, they cost much more than wooden ones.

On a note: Since LSTS are assembled using bolts and rivets, such structures can be disassembled and rebuilt if necessary, replacing any part or rebuilding the entire roof.

Rafter system of a gable mansard roof

The attic roof, depending on the angle of inclination, is divided into three main types:

• classic: slope slope 45 degrees, house width 6–8 m;
• pointed: slope – 60 degrees, width – from 6 m:
• broken line: has two unequal slopes, usually with a slope of 30 and 60 degrees. This design is often found in houses up to 6 m wide.

Project of a country house with a gable attic floor

Features of rafters for an attic with two slopes

IN gable roof The principle of hanging rafters is used. Relying only on the outer walls and on each other, they form a single under-roof space - a void without walls or supports in the middle of the attic space. Hanging type attic rafters are also called non-roof rafters.

Gable roof rafter system

The design of the rafter system of the attic roof in this case has some features, for example, a bolt tie, which, in contrast to the thrust created by the rafter legs, fastens them and the opposite slopes, is located not at the base of the attic rafters, but above. The height is chosen in such a way that it is enough to construct an attic space.

If a system of hanging rafters is used for an attic with a span of 6 m or more, then the trusses are supported by braces or racks. They are placed on purlins installed on the ceiling. The lower part of their legs has a limitation - the length should not exceed 4.5 m.

As you know, the pitch of the rafters varies from 0.6 to 1 m. How to calculate this distance for a specific roof?

Initially, in the calculations we will use the average pitch value - 0.8 m. We will carry out calculations for a roof with a slope length of 23 m. For its installation, on average, taking into account rounding up, 23/0.8 = 29 rafter legs will be required. Let's add 1 more - this is an element that must be installed along the edges of the frame. In total, there were 30 elements. It remains to adjust the step: 23/30=0.77. Thus, the rafters must be installed with a distance of 0.77 m between them.

Installation of attic roof rafters

Installation of rafters for the attic is schematically carried out in the following order.

Gable roof rafters

1. The top beam is attached to the racks, and the first one will simultaneously serve as a rafter frame.
2. Install the Mauerlat.
3. The rafter legs are mounted in increments of 60–100 cm. First, the trusses that are outermost to the pediment are installed and a level is drawn in accordance with which the intermediate elements are installed.
4. The rafters at the top of the frame are connected to each other.
5. For roofs longer than 7 m, a ridge beam is installed.

Rules for fastening rafters

They are attached to the Mauerlat using a rigid or sliding method. In the first option, the possibility of interaction between fixed elements is almost completely excluded.

Attachment to the Mauerlat: sliding and rigid

For this

• use metal corners for attaching the lower part of the rafters with additional rigid support to the sheathing beam;
• attached to a cut made on rafter leg and additionally fix the connection using staples, nails, and wire.

The sliding coupling of the elements provides the rafters with freedom of movement within certain limits. It is more suitable for wooden houses, since it eliminates deformation of the supporting system during shrinkage of the house. It is carried out using a “sled”, a bracket, and nails.

Attachment to the ridge: butt and overlap

Attachment to the ridge is carried out:

• connecting the rafters end-to-end, cutting the top edges at a certain angle.
• fastening per run one at a time
• overlap connection.