Correct mansard roof. How to build a mansard roof with your own hands using a unique construction technology
How to increase the living space of an old house without additional extensions? The best option- installation of a new roof mansard type. To erect it, it is necessary to carry out the calculation part, select the correct rafter scheme and roof covering material.
First you should find out optimal weight new design, since not all walls of an old house are designed for additional load. The total weight of the roofing pie is equal to the sum of the following components: rafters, sheathing, insulation and waterproofing. At the same time, it is easy frame construction must be serviceable: withstand not only standard snow and wind loads, but also the weight of a person.
Taking data from the table, you can calculate optimal load on load-bearing walls. Let's assume that they are made of solid brick with a masonry thickness of 400 mm. Then the constant load will be equal to: 400*1800/1000= 720 kg/m². In this case, the walls are able to withstand the weight of the attic, made of beams with a density of 300 kg/m³ and covered with ceramic tiles.
If the walls are not able to withstand total weight attic, you can build an additional foundation. Bearings are installed on it vertical supports to create the base of the roof. This design will avoid stress on the walls of the house.
Most often, a new attic is made in the form of a gable sloping roof. This is due to the large interior space, which can be used as a living space.
Before starting construction, you need to make the correct calculation optimal distance between the rafters (see Gable roof rafter system). An old wooden house cannot always withstand the load of a new roof, so you should choose the installation step of load-bearing structures based on the calculated weight of the roof. Data about this parameter can be taken from the table.
Then, based on the calculated data, material is purchased - wooden beams, rafters and slats for sheathing. The last step depends on the coating material. Often it should not exceed 400 mm. But the final parameters are determined based on the recommendations of the roofing material manufacturer.
Mauerlat installation
Mauerlat are horizontal beams on which the load-bearing elements of the roof will be mounted. It is designed to evenly distribute the load on the walls.
To perform installation work you will need following materials and tools:
- Hammer, wood saw.
- Nails up to 50 mm long. The quantity depends on the roof area.
- Measuring tools: plumb line, building level, tape measure.
Most often, a wooden beam with a cross section of 150*100 is used for mounting the Mauerlat. Its quantity is determined by the perimeter of the roof. To connect timber with load-bearing wall It is recommended to use mounting dowels.
Installation of rafter frame and sheathing
At the first stage, it is necessary to install load-bearing beams on the Mauerlat. Then they are attached to vertical racks, connected to each other in the upper part by beams - purlins. The rafters for the future attic roof are mounted on the resulting frame.
The sheathing is designed for installation roofing. Its size and configuration depends on the used protective material. Typically, 40*150 mm boards are used to make lathing. They are packed on top of the rafters, forming an installation platform.
Final stage
The above construction technology mansard roof is universal. It is recommended to use a special rolled microfiber as a waterproofing layer. It is attached to the sheathing. The roofing covering is already installed on top of it. For improvement thermal insulation properties The roof needs to be insulated internally. This is done using basalt wool or extruded polystyrene foam.
What you need to pay attention to when arranging a mansard roof in an old one-story house? First of all, correctly calculate the total weight of the structure, install a reliable roofing pie and select the appropriate material. The result of the work is an additional living space, the comfort of living in which will be no worse than in the other rooms of the house.
The attic does not have to be used as a place to store unnecessary things. Very often, the area of this room allows you to equip it with a full-fledged living area or a place for family leisure or hobbies. The idea of such construction has been successfully used since the mid-17th century thanks to the French architect Francois Mansart and is especially relevant for increasing the area of a private house, and sometimes city apartments.
How to inhabit an attic, what measures should be taken for this and how to build an attic where there has never been one? Look for answers to these questions in our article.
We are building an attic
Installing an attic will help to significantly reduce construction costs as a whole, rationally use the available floor space and realize the most daring ideas. The attic floor can occupy either the entire attic or part of it, depending on the purpose of the future room: bedroom, study, office or bathroom.
Cozy do-it-yourself attic
Building an attic with your own hands also provides the following advantages:
- The infrastructure of the main building is fully used.
- The living space increases significantly.
- Reducing heat loss through the roof and, as a result, reducing energy costs during the cold season.
- Relatively simple installation (without the use of special equipment) and the ability to stay in the house during construction.
- Possibility of building a one- or two-level floor.
How to make an attic a unique architectural element
Important: During construction attic floor With your own hands, you need to take into account the design features of the building, including: the height of the walls, the shape of the roof, the location of communications - and comply with fire safety requirements.Features of the construction of the attic floor
The roof is an enclosing structure, which, in addition to precipitation and temperature changes from the outside, is subject to influences from the inside: heat and moisture from the living space, and these can cause dampness and corrosion. Therefore, when constructing an attic floor, very stringent requirements are put forward for hydro-, steam- and thermal insulation of the roof, compliance with which will ensure reliable protection of the room from negative factors.
How to properly insulate an attic floor during construction
Also, when building an attic floor, it is important to take care of high-quality ventilation, which is installed between the insulation and the roof. This will ensure that excess moisture is removed and the attic is ventilated.
Particular attention should be paid to the construction technology and the materials used (especially their weight) - this will ensure the safe operation of the attic floor in the future. In addition, do not forget that using the attic floor as a living space does not eliminate compliance technical requirements for roof maintenance.
Where to start construction?
Before construction begins, a technical examination of the building is carried out. It is worth remembering that initially the walls and foundation of the building were designed for a certain load, and the construction of an additional floor will significantly increase it, so it is worth making sure of their load-bearing capacity.
Construction frame attic
Design
The next stage of construction will be the development and approval of the attic floor project - for this it is better to contact qualified specialists who will help you draw up a competent drawing, calculate loads and estimates.
Important: If the construction of an attic with your own hands is carried out within the city limits, then for this you must obtain permission from the city authorities, expert opinion and the consent of all building owners.The attic floor plan is developed based on the layout of the main building, with the geometry of the roof playing a dominant role. The architectural appearance of the house will influence not only the design rafter system, but also on the materials used in construction and individual elements of the attic. All structures and parts must be as lightweight as possible, which will ensure minimal load on the walls of the building and ensure easy lifting of materials to the floor.
If the roof of the house has a large slope, then the choice of roofing materials, insulation and waterproofing during the construction of the attic floor should be approached especially carefully.
In addition, all communications of the attic floor must be interconnected with the systems in the house, and their joint operation must be ensured.
The shape of the room, as well as its dimensions, determine the choice of windows, their design and placement in the interior.
Construction of an attic
Regardless of whether the attic is being built with your own hands, photo below, in an existing attic or is being built from scratch, it is necessary to ensure the unity of architectural and design solutions.
Can be built on wooden attic on brick house
It is better to make the attic structure from wood (timber) or a metal profile; in addition, you can complete the floor from SIP panels, as in the photo below. Stone materials, including brick and concrete, are not recommended for construction due to their heavy weight. As a last resort, you can use aerated concrete blocks.
We build an attic with our own hands using SIP panels
Durable but lightweight materials, such as corrugated sheets, bitumen or composite tiles, and metal tiles, are also suitable for roofing.
Since the attic has a large surface area in contact with the environment and significant heat loss occurs through the roof, it is necessary to take care of high-quality and effective thermal insulation this floor. For insulation, it is best to use mineral wool or fiberglass with a thickness of 150 mm or more. WITH inside The insulation on the attic floor must be covered with a vapor barrier, and on the roof side – with waterproofing. In addition, it is necessary to install a ventilation system between the waterproofing and the roof, which will ensure the removal of excess moisture.
Since the attic is a living space, it needs natural light, which windows will help provide. These can be either ordinary vertical window structures that are mounted into walls, or special inclined windows that are installed in the roof plane at an angle of 15-90 degrees.
Dormer windows- expensive but effective
Important: Dormer windows let in more light than standard windows with a smaller opening area. To ensure the most efficient and uniform lighting, the ratio of window area to floor area should be 1:10.The final stage of installing the attic floor will be finishing work. The most simple option plasterboard is used for cladding the walls of the attic floor; it can be used to construct internal partitions. GKL sheets are attached to a frame made of metal profiles, after which they are puttied and the finishing coating can be applied: paint, wallpaper, etc. In addition to plasterboard, the walls can be sheathed with clapboard, wood panels— the choice of material depends on the purpose and design of the future attic. The same materials that are used throughout the building are suitable for the floor: parquet, laminate, batten, ceramic tiles, etc.
After construction is completed, you can start decorating: think through the interior, install a staircase, arrange furniture, etc.
More information about building an attic with your own hands (video):
Attic floor extension
The addition of an attic floor allows you to simply and effectively increase living space without the use of expensive equipment and complex technologies, and such construction can be carried out both in a private house and in a standard urban building. The cost of completion is approximately half of the cost of new construction. The structure can be wooden - from logs and timber; stone - made of foam blocks, brick and concrete; made of metal, as well as their various combinations.
Monolithic attic can have any shape
It is necessary to determine which part of the building structure will bear the load from the extension. If the strength of the walls and foundation is not enough, you will need to install racks on the outside of the building on a separate foundation that will support the attic floor. New attic frame independent foundation also necessary in an old house if the supporting structures have significant wear. It would be useful to change attic floor, since it is most likely not designed for heavy loads.
The construction of an attic involves the construction of a power structure, which depends on the roof truss system. To build this structure, it is better to use lightweight materials: thin-walled profiles and wood. They will help speed up construction, since fastening is carried out using bolts and rivets. Optimal angle The slope of the rafters should be 45-60 degrees.
Important: When manufacturing a rafter system, you should focus on the conditions of the area where construction is taking place. Load bearing capacity The roof must be designed for the pressure of wind, snow and roofing material.The roofs themselves, picture below, can be:
- Single-pitch.
- Gable.
- Broken.
- The hip ones.
1 – simple gable roof; 2 - gable roof with attic wall; 3 – hip; 4 - hipped
The last two types are best suited for the attic, but the final choice is determined by the intensity of the load acting on the coating.
During construction, it should be taken into account that the width of the room should not be less than 4.5 m, and the area of the entire attic floor should not be less than 7 m2, while the ratio of height and area is ideally 1:2.
The simplest construction option is to build a frame attic with your own hands. To install an attic, it is necessary to remove the old roof and examine the condition load-bearing structures for damage and develop a floor plan. After this, the foundation and frame of the attic are installed. Then the roof is installed and insulated.
Learn more about how to build an attic with your own hands - video:
Construction of the attic individual house- a fairly common occurrence. This construction method allows you to reduce the cost per square meter and create a fairly interesting room in the under-roof space. In order to properly install an attic floor, you need to study the basic requirements for it and choose the right type of roof and its slope.
What is an attic
According to regulatory documents, the attic floor is the volume under the roof that is used to accommodate residential and utility rooms. In this case, the height of the external walls should be no more than 1.5 m in the general case, otherwise the space will be considered a full-fledged residential floor.
A do-it-yourself attic is beneficial both during the construction and operation of a private house. In the first case, costs are reduced due to the fact that the height of the vertical enclosing structures is reduced. The roof takes on this function without ceasing to fulfill its original purpose.
An attic is an under-roof space that can be converted into a separate room for living.
During operation, cost reduction may include the following:
- The heated volume of premises is reduced, as a result, there is a reduction in heating costs, which are an impressive item of utility costs.
- After completion of construction, the house must be measured by specialists from BTI, after which a passport of the object is issued. It is based on the area values given in it that taxes are calculated and payment is made utilities(subject to connection to centralized systems and the absence of metering devices, which is now practically unheard of). The area of the marsard floor is included in the area of the entire house with coefficients of 0.7 or 0.8 depending on the height outer wall and the angle of inclination of the roof, which allows significant savings throughout the entire life of the facility.
Preparatory stage
Construction should begin with the development of a project or diagrams on which the future structure will be drawn. Most often, the roof that is used for the attic floor is a gable roof, but it is also possible to use a four-slope hip roof. The gable design makes it possible to provide full-fledged windows in the gables.
In the case of using a hip for lighting rooms, it is possible to install only attic window openings. This option may become more labor-intensive in terms of installing roof elements and developing interior interiors. Cost reduction with a hip roof is achieved due to the absence of gables (the savings will be especially noticeable in a brick house, where the cost of materials and the work itself on installing wall fences is quite high).
Do-it-yourself attic construction begins with determining the geometric dimensions and shapes of the roof. We have already talked about choosing the type of rafter system for a house (gable, hip), after which you will need to decide whether the slope will be straight or broken. The broken design has such disadvantages as increased cost and labor intensity. Its use is justified by the need to increase the height of the room by changing the angle of the roof.
At the design stage, the optimal roof slope is determined. Its choice depends on ergonomic considerations and the roofing material used, which imposes restrictions.
Before making an attic, it is also necessary to calculate all its load-bearing elements for strength and bending, select the composition of the roof pie, perform thermal calculations and decide on materials. More on this below.
Main load-bearing elements
The design includes the following components:
- Rafter legs, which transfer the load from the weight of the roofing and the wall to the walls of the house. The section is selected depending on the angle of inclination, span, pitch and design load. A professional can perform detailed calculations correctly. For private construction, you can use approximate values, but it is best to provide a small margin.
- Narozhniki- This rafter legs, which on one or both sides rest on obliques. The cross section is calculated in the same way as for rafters.
- Sloping legs- a design that is used in hip roof. This element serves as a support for the narodniks. The cross-section is taken depending on the load and span; in any case, it should be larger than that of the rafter legs.
- Mauerlat- an element that serves as a support for the footrails and transfers the load from the roof to the walls, distributing it evenly. It would be correct to choose a section with dimensions of 100 by 100 or 150 by 150, depending on the complexity of the object. Installation of the Mauerlat is not carried out during the construction of frame and wooden houses, since in this case its role is played by the upper crown of the walls or trim.
- Rigel- a beam, which also serves as a support for the rafters, but in the upper part. The crossbar is installed at the ridge of the roof or at a break in the slope, in the case of a broken structure. The cross-section should be taken depending on the conditions; the recommended value is 200 by 200 mm.
- Struts, racks, contractions– additional elements for securing elements. They are used to reduce the cross-section of load-bearing structures. Their cross section is most often chosen constructively. It is important to consider the convenience of making connections.
A do-it-yourself attic roof must be erected starting with the selection of sections of all elements of the roof frame. The material for manufacturing is selected taking into account the following conditions:
- the wood must be coniferous species(pine, spruce, larch);
- material grade – first or second;
- humidity no more than 15%.
Be sure to treat all boards and bars with antiseptic compounds before starting construction.
Thermal calculations
To keep the house warm, you will need to select the thickness of the insulation. Most often, mineral wool is used for attic spaces (more often in slabs than in mats). It is also possible to use polyurethane foam, polystyrene foam, extruded polystyrene foam and ecowool. Having determined what to make the thermal insulation layer from, select its thickness. It is important to consider the height of the rafters. It should always be equal to or greater than the thickness of the thermal insulation. For mineral wool It will also be necessary to provide a 50 mm thick ventilation gap between the top surface of the heat insulator and the roof covering. If the cross-section of the rafters is small, then in order to fulfill this requirement, a counter-lattice is installed.
Before you build an attic roof with your own hands, you can calculate it using heating engineering manually, guided by the joint venture “Thermal protection of buildings.” But it’s better to ask for help special programs. To correctly calculate the thickness in the Teremok program (available for free on the Internet), you need to know the thermal conductivity of the insulation and the area where the house is being built, the program will find the rest itself.
A do-it-yourself mansard roof differs from a conventional pitched roof only in the presence of thermal insulation. More layers are also added to the cake to protect the insulation. Below step-by-step instruction will allow you to correctly install the elements of the attic roof.
The procedure is as follows:
- fastening the Mauerlat to the wall;
- installation of rafters and systems of struts and racks;
- installation of waterproofing and wind protection;
- sheathing;
- roofing;
- insulation;
- bottom trim.
Assembling the roof frame
Installation begins with the Mauerlat. It is laid on the inner grant of the outer wall. Fastening depends on the material of the load-bearing walls, but in general it can be done in several ways:
- on staples;
- on stiletto heels;
- on the anchor.
For fragile house wall materials, such as aerated concrete and foam concrete, trimming is carried out monolithic belt which will prevent the walls from collapsing. For wooden and frame houses Mauerlat is not provided.
Next, you need to install the crossbars, if provided. After the supporting structures are laid, the rafter legs are laid out. The fastening of the rafters to the mauerlat can be rigid and hinged. It is better to do it using cutting and fixing metal corners on both sides.
This is a fairly old album, so all the drawings in it use nails as fasteners. It is better to replace them with studs. The design of the roof of the house in this regulatory document shown in great detail, so it is recommended that you familiarize yourself with it before starting work.
Before you begin installing insulation in the house, it is necessary to ensure its protection from negative impacts environment. To do this, spread a moisture- and wind-proof membrane over the surface and secure the sheathing. After this, the roofing covering is installed, taking into account the recommendations for the selected material. For example, for bitumen shingles you need a continuous sheathing, which is most often made of moisture-resistant plywood.
Installation of thermal insulation
To insulate a house, you need to install insulation without gaps or cracks. For mineral wool, it will be easier to install if the clear distance between the rafters is 580 or 1180 mm. This will allow the material to be laid with a slight spacer, which will prevent cracks from occurring.
When using expanded polystyrene, the distance between the slabs and rafters is filled with sealant or polyurethane foam.
After laying the insulation, you need to attach a vapor barrier to it from below. After this, the lower sheathing and ceiling lining are installed. For an attic, it is best to cover the frame with two layers of 12.5 mm thick plasterboard followed by finishing.
Arranging it is the easiest and most quick way increase the number usable area. Rooms in the attic acquire a certain romantic aura and become a favorite place for household members to spend time. The main advantage of these premises is the large number fresh air and light. But you need to approach it with all responsibility, otherwise you risk becoming a hostage to weather conditions.
The mansard roof can be of any shape, but most often it is gable. And if it is also broken, then with its help the space is used most rationally. A huge advantage of the attic floor is that its construction is much more economical than the construction of a full floor with solid walls.
The strength structure of the roof where there will be an attic or the one under which there will be no living space is no different. The strength and stability of the roof depends entirely on its rafter system.
Rafters- This is the main load-bearing structure of the roof. They must withstand both the weight of the roof and the load in the form of precipitation and wind. The rafter system is calculated based on the selected roofing material, as well as depending on the climatic conditions of the area.
For the construction of a power rafter system, ferrous metal in accordance with GOST, galvanized thin-walled cold-formed profile or wood, as well as combinations of ferrous metal and galvanized profile, metal and wood are used. In places that are difficult to access for installation, it is better to use a thin-walled profile.
The choice of material directly depends on the length of the spans that need to be covered. For long distances, ferrous metal or trusses are suitable.
It is very important to use only lightweight materials and structures for the construction of an additional floor. The advantages of a thin-walled profile are that it does not require welding and can be assembled locally using bolted connections or rivets.
Wood as a material is also good, but requires additional treatment with an antiseptic.
Rafters, frames or trusses are built from load-bearing structures. They are mounted on the Mauerlat, and then purlins are made on them. If the step is large, this also becomes part of the power structures.
Mauerlat- this is part roofing system in the form of a beam laid on the perimeter of the wall and is the lower rafter support.
An important task is how to make the attic warm, that is, to organize an insulation cake. The difference between a living space and just a roof is the need for its thermal insulation. As an additional load, all insulation is not significant and does not affect the strength structure of the roof.
The main principle in design is that the load-bearing structure must be placed either in warm contour, or cold, but not in the middle. Warm placement is preferable, then the entire insulation pie goes outside.
The most common mistakes:
- lumber is not treated with antiseptic and fireproof impregnations and this reduces the service life of your roof
- rafter legs are joined together with cuts without the use of thermal insulation gaskets, which leads to freezing and cold bridges
- rafter sections and their installation occurs “by eye” without taking into account loads
- the rafter legs are not attached to the mauerlat or are attached with nails, which is the same thing in case of a strong gust of wind
- The waterproofing film is laid with the front side inside the room, and not outside, as it should be
- not enough reliable fastenings joints of rafters with purlins, sometimes it’s just a couple of nails.
As a result of non-compliance construction technologies, many get disastrous results, even if not immediately. To avoid this, let's consider in detail how to do it.
An example of how to calculate an attic
Before you start building an attic with your own hands, you will need to make a drawing. If you do not know, for example, AutoCad, you can do this by hand. It is important that you clearly see the projection of your attic from the front, side and top view.
To begin, mark the load-bearing walls of your home in the front view (looking at the gable of the building).
So, let's say there is a house with the following initial parameters:
- Three load-bearing walls made of aerated concrete, 300 mm thick.
- The distance between the walls is 4m.
- The floor beams of the first floor are laid with a 50cm cornice extension.
- Because the maximum length wooden beam– 6m, then this value is taken as the basis for the width of the attic floor. Based on this, we get a drawing of a gable sloping roof.
- The height from the ceiling to the beam is 2660mm.
- The length of the side and top rafters (roof breaks) is 3300 mm each. When these values are the same, then, in addition to the fact that it looks harmonious, it will be easier to calculate the area of the roofing.
- The angle of inclination of the side rafters is 60°, the top one is 25°.
- The thickness of the floor beams is 250mm, the rafter beams are 200mm.
- Vertical posts of 150 mm each were installed, on which the strapping beam was laid, and the attic floor beam, side and top rafters were attached to it.
- The total height of the roof is 4260mm, and the height of the living space is 2250mm. According to the standards, this is the permissible ceiling height for premises for temporary stay, that is, bedrooms, children's rooms.
Essentially, an attic is a frame consisting of several posts, beams and rafters.
If the length of the transverse floor exceeds 6 m, and, accordingly, one beam is not enough, then the upper part of the attic can be made in the form of a truss with a rack, a truss and an additional rack. In the side part, trusses can also be installed that push the rafters apart. In this case, these details are not necessary.
When making calculations, you must have at hand a set of rules and tables for technical standards construction, which is called “Loads and Impacts”. It contains not only general provisions, but also formulas with coefficients, for example, of melting, snow drift and the unevenness of its distribution over the roof area.
When calculating how to build an attic, you must remember that it is subject to 4 types of loads at once:
- own weight (it is relatively easy to calculate, knowing what kind of insulation pie will be in the ceiling and rafters)
- pressure on the floors of people inside, furniture, etc.
- snow load on a slope less than 30° is equal to 1.52 kPa; if the slope is steeper than 60°, then there is no such load on it
- wind, which acts evenly on all rafters on the windy side, and on the leeward side at this time a suction occurs, “tearing off” both the top and side rafters.
Also, the tearing force of the rafters is especially effective when the wind blows into the gable of the building. These loads are calculated using formulas using the appropriate aerodynamic coefficient.
We build an attic with our own hands
Installation sequence:
- First of all, floor beams with a section of 70 (50) x 250 mm are laid in steps of 1 m (for each wall length this is calculated individually, the main thing is that the step is the same). In this case, this is also explained by the fact that a ladder will go into one of the gaps, and it should not be narrower than 90 cm. If you take a step smaller, the floor beam would have to be cut and strengthened, and this is an additional concern.
- On the sides of the beams, beams are packed onto which the sheet material or boards.
- After installing the beams, racks are attached to them in 2 rows, which are leveled using a plumb level, and then temporary jibs are made, perpendicular to each other and nailed, along and across the axis of the roof. This additionally secures the beams and prevents them from deviating to the side. You can use any board for the jib.
- A rope is pulled between the two outer posts and the remaining posts are leveled along it. Their step is always equal to the step of the floor beams. All racks are secured in the same way as the outer ones. The result should be two parallel rows of racks, on which the strapping bars are then placed.
- The purlins are laid and secured to the posts with 150mm nails and corner screws.
- Crossbars made of timber 50 x 200 mm are placed on top on the edge, which increases their rigidity. Since subsequently there is no significant load on them, this section is usually sufficient. But in order to insure them during installation, supports made of timber no thinner than 25mm are placed under them. At this stage, the rigidity of the attic is ensured only in the transverse direction; V longitudinal design unstable. From above, while the rafters are not installed, you can also temporarily strengthen one or two boards on the crossbars.
- Lower rafters with a section of 50 x 150 mm are installed. First, a template is made from a 25 x 150mm board (it is easier to process). The length is measured, applied to the top beam and the shape of the joint is drawn directly on the board, which is then cut out. Next, the template is tried on at all other places where the rafters are installed, and if it matches them, all legs are cut out according to the template. However, the lower part, which rests on the Mauerlat, is cut in place. The rafters are secured using corners with self-tapping screws and nails. Beams with rafters can be mounted in parallel, that is, when all the elements are fastened in one span at once, or they can be mounted sequentially, when all the floor beams are installed first, and then all the side rafters.
- So-called wind connections are installed. These are wooden braces that push out the top point at the level where the attic beams are installed.
- Line of upper rafters. At the ridge level, for convenience, sometimes an overlay is made and a tightening in the middle in order to pin the rafters on the ground, and then lift them and unfasten them in place. The center of the roof is marked using a temporary stand, which is nailed to the Mauerlat and the extreme tie on the end side so that this board goes up the center of the roof. This will be the guide for the rafters. Next, as in the case of the lower ones, they make a template, applying it with one end to the edge of the installed board, and the other to the purlin on which the upper rafters will rest. They cut it out and try it on at all points on both sides of the roof. If the posts were secured parallel, there should be no problems with the upper rafters.
- According to the template, the required number of rafter legs is made. They are placed on longitudinal beams with cuts, fastened with corners and in the upper part connected with scraps of boards with screws or metal plates. They are often fastened with cuts to the transverse beams: hanging racks 25 x 150 mm are fixed between the junction of two rafters and the attic tie.
- Next, the attic ceiling is installed in the same way as the floor, when boards are laid on the sides on nailed bars.
- Installation of the frame for sewing up the pediment, it is called half-timbering. Here it is indicated window hole. Its racks can be a 50 x 150mm board with a pitch of about 600-700mm. Important: the rib of the post must run across the pediment, creating additional rigidity.
- Now you can start covering the pediment with boards. It is worth doing this before laying the sheathing, so that later, if some boards extend beyond the rafters, it will be easier to cut them down. If you do the opposite, you will have to adjust the corner of each board to fit the existing sheathing. Up to the attic floor beam, the pediment is covered with boards horizontally. The remaining piece of the pediment is sewn vertically.
- The top connections are made. Since the gable frame beams were attached to a fairly flexible floor beam, it is necessary to create a kind of stiffening truss using the next floor beam.
- A brace is installed that expands top part rafters Its base is attached to the third floor beam from the edge, and its end rests on the outermost point of the ridge. This element is used more often with soft roofing, when the rigidity of the ridge is not enough.
If the house is completely framed, then it is necessary to install such connections in the ceiling of the first floor. If the house is reinforced concrete, then there is already a stiffening belt in the upper part of the ceiling and does not need connections.
In some cases, it is also necessary to provide stiffening connections in the rafters. If corrugated sheeting or metal tiles are used as roofing, then the rafters no longer need to be reinforced: the sheet material will already serve as a rigidity diaphragm if it is installed well.
Fastening elements to each other can be very diverse, for example, staples with nails, wooden or metal plates, MZP (metal gear plates, whose teeth are driven in with a sledgehammer). It is important to remember that the length of the nails should be at least twice the thickness of the board you are nailing.
Fastening the sheathing
Depending on the chosen roof covering, sheathing is laid at the final stage of attic construction.
The sheathing is a structure made of beams that are laid perpendicular to the rafter legs, attached specifically to them. The function of the sheathing is to take on the weight of the roofing, holding it securely in place.
Lathing for sheet covering is a continuous sheathing and is made of edged boards 25mm each. The width should be no more than 140mm, since wide boards tend to deform. If there is more than 1 m between the rafters, then it may be necessary to speed up the movement of the rafters with special bars, and then lay out the boards. Next, roofing material or glassine is placed, and spread on top roofing material. It should be noted that such lathing makes the roof extremely reliable and is suitable for absolutely all types of coatings, while reducing noise from rain.
Sheathing for metal tiles make it sparse and, if possible, adjust it to the course of the waves of the tiles. Mounted from edged boards 25(30) x 100mm in increments of 80-100cm. The peculiarity is that before installation on the rafters, a waterproof membrane is strengthened. The first board from the eaves should be installed higher than the others at the height of the wave of the tiles. If short boards are used, it is better to place their joints in a checkerboard pattern.
Lathing for ceramic tiles and other piece elements are considered the most complex. The work also begins with the installation of a hydraulic barrier, and then a sparse sheathing is made from 50 x 50 mm bars. The difficulty is to maintain a precise rhythm between the elements, since one step is equal to the covering surface of one tile.
There are always several approaches to the process of any construction. Here we described how to make an attic with your own hands on an already built house, however, there are cases when the attic is assembled in a position on the ground and placed in its place with the help of a crane, and then strengthened in the right places.
A house with an attic is not only an additional living space, but also a respectable appearance of the entire building. Even if the room under the roof is made unheated and is used only in the summer, it still creates a powerful “air cushion” that helps retain heat inside the entire building.
And about that - read on our portal.
Attic project
When drawing up a diagram for the construction of an attic, it is best to do this in different projections in order to see and understand the placement of all elements of the rafter system. It is very important to correctly calculate the height of the roof ridge, since the size of the area under it will directly depend on it.
When drawing up a design diagram for the construction of an attic roof, you need to calculate the height of the ridge, ceiling and total area of the room.
The minimum height from the floor to the ridge should be 2.5-2.7 m, but if this distance is less, then the room is not an attic, it can only be called an attic. This parameter is established by SNIP standards.
In order for all elements to be drawn accurately and have the desired location in the overall system, you need to start from a figure with right angles, that is, a rectangle or square - a section of the created attic room. Based on the sides (height and width of the future room), it will be almost impossible to make a mistake with the magnitude of the angles at which the roof slopes are located, with the location of the ridge, rafters and all supporting elements. When determining these parameters, they must immediately be entered into the drawing.
First you need to find the middle of the width of the front wall. Starting from this point, the parameters of the height of the ridge, the future ceiling of the attic, the location of the wall studs and the size of the eaves overhang are determined.
Due to the fact that each of the structures has a certain number of connecting nodes, which have different configurations, it would be a good idea to draw each of these connections separately in order to understand their features of interconnecting all the elements connecting at this point.
Any rafter system consists of basic elements and additional ones, which may not be present in every structure. The main components of an attic roof include:
- Floor beams, which are the basis for the remaining elements of the rafter system. They are laid on the main walls of the building.
- Rafter leg, straight in gable system roof or consisting of two sections - in broken pattern. In this case, the top rafter is called the ridge rafter, since it forms the highest point of the roof - and the rafters that form the walls of the attic are called side rafters.
- A ridge board or beam is a mandatory element for a gable roof, but is not always used when installing a broken roof model.
- Mauerlat is a powerful beam attached to the main side walls of the building. Rafter legs are installed on this element.
- Racks are the supporting elements necessary to strengthen a gable and broken structure. In the latter case, the ridge and side rafters are attached to it, and in the first, the stand is a reliable support for a long rafter. In addition, the racks serve as a frame for insulating and covering the walls of the attic.
- Diagonal bracing members or bevels additionally secure posts or longitudinal beams and rafters, making the structure more durable.
- Attic floor beams are used in all versions of the attic - they connect the racks, and they also serve as the frame for the ceiling.
- Inter-rafter purlins are installed in a broken roof for structural rigidity.
To be sure that the prepared project is developed correctly, you need to show it to a specialist. Only he will be able to determine whether the attic parameters are correctly selected for the width and length of the walls of the building.
Video: professional calculation of a mansard roof using special software
Material parameters for the construction of an attic roof
If the graphic design is ready, then, based on the dimensions marked on it, you can calculate the amount of materials required for the construction of the attic roof. Materials must be selected according to their characteristics, which must meet fire and environmental safety requirements. For wood, it is necessary to provide special treatment with fire retardants, which will reduce the flammability of the material. So, for construction you will need:
- Boards for rafter legs. Their cross section is selected based on the results of special calculations - this will be discussed in more detail below.
- A beam with a cross-section of 100×150 or 150×200 mm is for floor beams, depending on the selected rafter system and the width between load-bearing walls, as well as for purlins, diagonal legs or valleys - if they are provided for in the design.
- Beam with a cross section of 100×150 mm or 150×150 mm for laying the Mauerlat.
- For racks, timber 100 × 100 or 150 × 150 mm is usually used.
- Unedged board for laying the subfloor and some fasteners.
- Annealed steel wire with a diameter of 3-4 mm - for fastening some parts together.
- Nails, bolts, staples of various sizes, angles of various configurations and other fasteners.
- A metal sheet with a thickness of at least 1 mm is for cutting out overlays.
- Lumber for sheathing and counter-lattens for roofing material - depending on the type of roof chosen.
- – for thermal insulation of the roof.
- Waterproofing and vapor barrier membranes.
- Roofing material and fastening elements for it.
What section of rafters are required?
Rafters are roofing elements that will bear the main external loads, so the requirements for their cross-section are quite special.
The size of the required lumber will depend on many parameters - on the step between the rafter legs, on the length of these legs between the support points, on the snow and wind load that falls on them.
The geometric parameters of the rafter system design are easy to determine in the drawing. But with the remaining parameters, you will have to refer to the reference material and make some calculations.
Snow load is not the same for different regions of our country. The figure below shows a map on which the entire territory of Russia is divided into zones according to the intensity of the snow load.
There are eight such zones in total (the last, eighth, is rather extreme and cannot be considered for the construction of an attic roof).
Now you can accurately determine the snow load, which will depend on the angle of the roof slope. For this there is the following formula:
S = Sg × μ
Sg– table value – see the map and the table attached to it
μ — correction factor depending on the steepness of the roof slope.
- If the slope angle is me 25°, then μ=1.0
- With a slope from 25 to 60° - μ=0.7
- If the roof is steeper than 60°, then it is considered that snow does not linger on it, and the snow load is not taken into account at all.
It is typical that if the attic roof has a broken structure, then for different sections of it the load can have different values.
The slope angle of the roof can always be determined either with a protractor - according to the drawing, or by a simple ratio of the height and base of the triangle (usually half the span width):
Wind load also mainly depends on the region in which the building was built and on the characteristics of its surroundings and the height of the roof.
And again, for the calculation, the initial data on the map and the table attached to it are first determined:
The calculation for a specific building will be carried out according to the formula:
Wp = W × k × c
W– table value, depending on the region
k– coefficient taking into account the height of the building and its location (see table)
The following zones are indicated by letters in the table:
- zone A - open areas, steppes, forest-steppes, deserts, tundra or forest-tundra, wind-exposed sea coasts, large lakes and reservoirs.
- zone B – urban areas, wooded areas, areas with frequent wind obstacles, relief or artificial, at least 10 meters high.
- zone IN– dense urban development with an average building height above 25 meters.
With– coefficient depending on the predominant wind direction (wind rose of the region) and on the angle of inclination of the roof slopes.
With this coefficient the situation is somewhat more complicated, since the wind can have a dual effect on the roof slopes. Thus, it has a direct, overturning effect directly on roofing slopes. But at small angles special meaning takes the aerodynamic effect of the wind - it tries to raise the plane of the slope due to the resulting lifting forces.
The drawings, diagrams and tables attached to them indicate areas of the roof exposed to maximum wind loads, and indicate the corresponding coefficients for calculation.
It is characteristic that at slope angles of up to 30 degrees (and this is quite possible in the area of ridge rafters), the coefficients are indicated both with a plus sign and negative, that is, directed upward. They somewhat dampen the frontal wind load (this is taken into account in calculations), and in order to neutralize the effect of lifting forces, it will be necessary to very carefully secure the rafter system and roofing material in this area, using additional connections, for example, using annealed steel wire.
After the wind and snow load calculated, they can be summed up, and, taking into account design features system being created, determine the cross-section of the rafter boards.
Please note that the data is given for the most commonly used coniferous material (pine, spruce, cedar or larch). The table shows the maximum length of the rafters between the support points, the section of the board depending on the grade of the material, and on the pitch between the rafters.
The value of the total load is indicated in kPa (Kilopascals). Convert this value into more familiar kilograms per square meter- not difficult. With completely acceptable rounding we can accept: 1 kPa ≈ 100 kg/m².
The dimensions of the board along its cross-section are rounded up to standard lumber sizes.
| rafter section (mm) | Distance between adjacent rafters (mm) | ||||||
|---|---|---|---|---|---|---|---|
| 300 | 600 | 900 | 300 | 600 | 900 | ||
| 1.0 kPa | 1.5 kPa | ||||||
| higher | 40×89 | 3.22 | 2.92 | 2.55 | 2.81 | 2.55 | 2.23 |
| 40×140 | 5.06 | 4.60 | 4.02 | 4.42 | 4.02 | 3.54 | |
| 50×184 | 6.65 | 6.05 | 5.28 | 5.81 | 5.28 | 4.61 | |
| 50×235 | 8.50 | 7.72 | 6.74 | 7.42 | 6.74 | 5.89 | |
| 50×286 | 10.34 | 9.40 | 8.21 | 9.03 | 8.21 | 7.17 | |
| 1 or 2 | 40×89 | 3.11 | 2.83 | 2.47 | 2.72 | 2.47 | 2.16 |
| 40×140 | 4.90 | 4.45 | 3.89 | 4.28 | 3.89 | 3.40 | |
| 50×184 | 6.44 | 5.85 | 5.11 | 5.62 | 5.11 | 4.41 | |
| 50×235 | 8.22 | 7.47 | 6.50 | 7.18 | 6.52 | 5.39 | |
| 50×286 | 10.00 | 9.06 | 7.40 | 8.74 | 7.66 | 6.25 | |
| 3 | 40×89 | 3.06 | 2.78 | 2.31 | 2.67 | 2.39 | 1.95 |
| 40×140 | 4.67 | 4.04 | 3.30 | 3.95 | 3.42 | 2.79 | |
| 50×184 | 5.68 | 4.92 | 4.02 | 4.80 | 4.16 | 3.40 | |
| 50×235 | 6.95 | 6.02 | 4.91 | 5.87 | 5.08 | 4.15 | |
| 50×286 | 8.06 | 6.98 | 6.70 | 6.81 | 5.90 | 4.82 | |
| total snow and wind load | 2.0 kPa | 2.5 kPa | |||||
| higher | 40×89 | 4.02 | 3.65 | 3.19 | 3.73 | 3.39 | 2.96 |
| 40×140 | 5.28 | 4.80 | 4.19 | 4.90 | 4.45 | 3.89 | |
| 50×184 | 6.74 | 6.13 | 5.35 | 6.26 | 5.69 | 4.97 | |
| 50×235 | 8.21 | 7.46 | 6.52 | 7.62 | 6.92 | 5.90 | |
| 50×286 | 2.47 | 2.24 | 1.96 | 2.29 | 2.08 | 1.82 | |
| 1 or 2 | 40×89 | 3.89 | 3.53 | 3.08 | 3.61 | 3.28 | 2.86 |
| 40×140 | 5.11 | 4.64 | 3.89 | 4.74 | 4.31 | 3.52 | |
| 50×184 | 6.52 | 5.82 | 4.75 | 6.06 | 5.27 | 4.30 | |
| 50×235 | 7.80 | 6.76 | 5.52 | 7.06 | 6.11 | 4.99 | |
| 50×286 | 2.43 | 2.11 | 1.72 | 2.21 | 1.91 | 1.56 | |
| 3 | 40×89 | 3.48 | 3.01 | 2.46 | 3.15 | 2.73 | 2.23 |
| 40×140 | 4.23 | 3.67 | 2.99 | 3.83 | 3.32 | 2.71 | |
| 50×184 | 5.18 | 4.48 | 3.66 | 4.68 | 4.06 | 3.31 | |
| 50×235 | 6.01 | 5.20 | 4.25 | 5.43 | 4.71 | 3.84 | |
| 50×286 | 6.52 | 5.82 | 4.75 | 6.06 | 5.27 | 4.30 | |
Tools
Naturally, during work you cannot do without tools, the list of which includes:
- Electric drill, screwdriver.
- Building level and plumb line, tape measure, square.
- Axe, chisel, chisel, hammer
- Circular saw, jigsaw, hacksaw.
- Carpenter's knife.
Installation will be accelerated if the tools for the work are of high quality, and the work will be carried out with competent mentors and assistants, carefully and step by step.
Installation stages
It is necessary to strictly follow the sequence of work - only under this condition the structure will be reliable and durable.
Mounting the Mauerlat
Installation of any rafter system begins with securing a powerful supporting structure to the end of the side walls of the building. timber - mauerlat, on which it will be convenient to install rafter legs. The Mauerlat is made from high-quality timber with a cross-section of at least 100 × 150 mm. It must be laid on roofing felt waterproofing laid along the upper end of the wall (regardless of the material).
Due to the Mauerlat, the load will be evenly distributed over the walls and transferred to the foundation of the building.
The Mauerlat is secured to the wall using metal pins, which are pre-embedded in concrete belt or a crown running along the upper edge of the wall, or anchor bolts with a diameter of 12 mm. They must go into the wall at least 150 — 170 mm. If the Mauerlat is installed on wooden wall, then the beams are attached to it using wooden dowels.
Installation of truss structure
- Installation of the rafter system begins with the installation of floor beams. They can be attached to the mauerlat from above if the beams are planned to be moved outside the perimeter of the building and thereby increase the area of the attic. In this design, the rafter legs are fixed to the floor beams.
Floor beams fixed on top of the Mauerlat (Fig. A) - In another case, they can be stacked on waterproofed walls and fastened with corners or staples to the inner edge of the Mauerlat. This option is used when the rafter legs are planned to be attached directly to the mauerlat.
Another option is that only the rafter legs are attached to the Mauerlat - Next, you need to find the middle of the floor beam, since this mark will become a guideline for determining the location of the support posts and the ridge.
- The racks should be located at the same distance from the marked middle of the floor beam. They will subsequently determine the location of the walls of the attic room, that is, its width.
- The bars for the racks must have a cross-section equal to the size of the floor beams. The constructions are attached to the beams using special corners and wooden overlays. However, to begin with, they are first nailed, then carefully leveled using building level and plumb line, and only then they are thoroughly secured, taking into account future loads.
- When the first pair of racks is installed, they are fastened together from above with a bar, which is called a tie. This tightening is also connected to the racks using special metal corners.
- After securing the tie, you will get a U-shaped structure. Layered rafters are installed on its sides, the second end of which is attached to the floor beam or placed on the mauerlat.
- A special recess (groove) is cut into the installed supports for the timber or in the rafters. With its use The rafters are tightly installed on the Mauerlat beam and secured with metal brackets.
- To provide rigidity to the structure, additional struts can be installed from the base of the rack to the middle of the installed side rafters. If this does not seem enough, and saving material is not in the foreground, then you can strengthen general design also with additional stands and contractions (they are indicated in the drawing, Fig. A, by translucent lines).
- Next, while tightening, the middle is calculated - the headstock will be attached to this place, supporting the ridge connection of the upper hanging subsystem of the rafters.
- The next step is to install ridge rafters, which can be fastened together different connections- this can be a metal plate or powerful bolts with metal plates or washers.
- After installing them, the headstock is attached to the ridge and the middle of the tightening.
- Having completed work on one part of the rafter system, you need to make all the rest according to the same principle. The distance between adjacent rafters in such a system should be no more than 900 — 950 mm, but the optimal interval would probably still be 600 mm - this will provide the necessary rigidity and stability of the structure, and will be convenient for insulation using standard mineral wool mats. True, this makes the structure heavier and will require more materials.
- First, the side parts of the system assembly are installed, and then the intermediate parts. They are connected to each other by purlins, which are installed between the upper ends of the racks and act as spacers. Thus, you will get a rigid structure of the attic rafters, in which the frame for wall cladding will already be ready.
Prices for various types of fasteners for rafters
Rafter fasteners
Waterproofing attic roof
When the rafter system is built, you can proceed to finishing it and accompanying materials.
- The first coating that should be fixed directly on top of the rafters will be a waterproofing and windproof film. it is attached to the rafters using staples and a stapler, starting from the cornice. The canvases are laid with an overlap of 150 — 200 mm, and then the joints are glued together with waterproof tape.
- On top of the waterproofing, a counter-lattice is placed on the rafters, which will more reliably fix the film on the surface and create the necessary ventilation distance between the windproof and roofing material. The counter-lattice is usually made of boards 100 wide — 150 mm and thickness 50 — 70 mm.
- The sheathing is fixed perpendicular to the counter-lattice, on which the roofing material will then be laid. The pitch between the slats must be calculated depending on the type and size of the sheet roofing material, taking into account the overlap required for it
- If a soft roof is chosen, then plywood sheets are most often fixed to the counter-lattice.
Roofing installation
The roofing material is attached to the prepared sheathing or plywood. Its installation usually starts from the roof eaves and proceeds in rows, from one of the edges - depending on the type of roof. Roofing sheets are mounted with an overlap. If used for coating metallic profile or metal tiles, then such material is secured with special self-tapping screws with elastic gaskets. Fastening elements are usually matched in color to the roofing material.
The most difficult thing in covering an attic sloping roof is the transition from layered side rafters to hanging ridge rafters. There may be certain difficulties if the roof has projections for installing roofs over balconies or windows.
In addition, if a chimney pipe goes onto the roof, it requires a separate design of the hole inside the rafter system and an insulating layer, and on the roof, reliable waterproofing must be installed around the pipe.
You can find out in detail how and what is the best way to cover the roof on our portal; there is a whole section where you can find answers to many questions, including recommendations for reliable insulation of the attic space.
Prices for popular types of corrugated sheets
Corrugated sheet
Video: detailed video tutorial on building a mansard roof
It should be noted that the work of constructing any roof, and especially one as complex as an attic roof, is not only responsible, but also quite dangerous and requires special, increased safety measures. If there is no experience in carrying out such construction processes, then it is better to entrust their implementation to professionals or perform all actions under control experienced craftsman, and with the utmost care and precision.