For low-rise buildings, a rafter roof is perfect. It will decorate the facade of the house, and with a sufficient slope, snow does not accumulate on such a roof, unlike a flat structure.
One of the types of roof rafters - gable. This is a fairly simple system, which is formed by two slopes. The slope of the roof is the entire inclined plane, with the help of which a drain is provided.
The structure rests on two parallel walls. Such a roof forms two triangular side pediments. A pediment is the end of a building's facade.
Advantages of a gable system
- Ease of Design.
The calculation of the bearing capacity and the necessary materials for the installation of such a roof is quite simple, since there are few options for the types and sizes of supporting structures; - Ease of installation.
A gable roof does not have complex structural elements. A small number of standard sizes allows you to quickly install all the elements of the roof; - Ease of use.
The fewer different breaks the roof has, the more reliably it protects the home. In the simplest version, a gable roof has only one break - a ridge. Such a roof is easier to repair in case of defects; - Free space.
For the arrangement of the attic, a gable roof is preferable, since it “eats up” space less. For comparison, consider a 6x6 m house with an attic. At the outer walls, the height from the floor of the room to the roof is 1.5 m, at the ridge - 3 m. For a gable roof under such conditions, the volume of the room will be 81 cubic meters, and for a hip roof with four slopes, 72 cubic meters. For larger building sizes, volume loss will increase.
Construction types
There are four main types of gable roofs:
- symmetrical.
Reliable, stable, easy to perform, based on an isosceles triangle; - Asymmetrical.
The ridge is not located in the center, the roof slopes have different slopes; - Polyline symmetrical.
Roof slopes are broken. Significantly increases the height of the room; - Polyline asymmetrical.
The attic or attic room is smaller than in the previous case. The roof has a very unusual appearance.
The choice of the type of gable roof depends on the purpose of the room located directly under it and the architectural appearance of the building.
General principles for calculating the truss system
The most important load-bearing parts of the gable roof truss system of a building are the mauerlat, crossbar and rafters. Mauerlat works in compression, so its cross section can be taken conditionally.
The crossbar and rafter legs experience a bending moment.
The calculation of such structures is carried out in terms of strength and stiffness. For small buildings, you can choose their cross section approximately, but for serious buildings, for safety and material saving purposes, the calculation of the truss system should be performed by a professional.
Roof self-weight load
To perform the calculation, you need to know the load per 1 sq.m. roofs.
To do this, you need to add the masses of 1 sq.m. all roofing materials:
- filing(if it is, it is most often performed from drywall);
- rafter legs. To calculate the weight of the rafters per square meter of the roof, you need to find the mass of the running meter of the rafter leg and divide this number by the pitch of the rafters in meters. For the calculation, you can take the approximate cross section of the rafter, the area of \u200b\u200bthis section must be multiplied by the density of the wood;
- heater (if any). The density of the insulation must be indicated by the manufacturer, it must be multiplied by the thickness;
- crate. To ensure a margin, a continuous crate can be taken into account. For example, 1 sq.m. lathing from a board 32 mm thick will weigh approximately 25 kilograms;
- roofing material. Weight 1 sq.m. coatings are usually specified by the manufacturer.
Snow load
The snow load for each area is different and is equal to the weight of the snow cover on a horizontal plane.
On the territory of Russia, it can take values from 80 to 560 kilograms per square meter. On the Internet, you can easily find a snow load distribution map and select the right number based on the construction area.
Roof pitch
The angle of inclination of the roof is quite easy to calculate, knowing the geometry and having an engineering calculator or a standard calculator on a personal computer at hand.
If we divide the height of the roof rise by the distance from the ridge to the cornice in the plan, we get the slope of the roof in fractions or the tangent of the angle of inclination. In order to calculate the angle, it is enough just to find the arc tangent.
If using an engineering calculator is difficult, the arc tangent can be found using an online calculator.
Rafter step calculation
The pitch of the rafters of the attic roof should be chosen for reasons of ease of installation of the insulation. Mats usually have a width of 60 centimeters, so the pitch of the rafters should be chosen so that the distance between them in cleanliness is 58 or 118 centimeters. Two centimeters will allow you to install the insulation boards very tightly, which will allow it to stick between the rafters and improve thermal insulation.
Rafter leg length
Leg length is easy to calculate using the formula:
L/cosα,
here L is the distance from the roof ridge to the inner surface of the outer wall in plan, and cosα is the cosine of the roof pitch angle. With rigid fastening, you need to add the size of the notch.
Section of the rafter leg
The cross section of the rafter leg must be selected as a multiple of the size of the boards and timber.
An example of a simple calculation of the section of the rafter leg:
- we find the load per 1 linear meter of the rafter.
q =(1.1*weight of 1 sq.m. of roof*cosα + 1.4*normative snow load*cosα2)* rafter spacing; - find W.
W= q * 1.25 * flight of rafters / 130; - solve the equation:
W= b*h2/6.
In this equation, b is the width of the section of the rafter leg, and h is the height.
To solve, you need to ask for the width and find the height by solving a simple quadratic equation. The width can be set to 5 cm, 7.5 cm, 10 cm, 15 cm. For small spans, a width of 15 cm is impractical.
To calculate the truss systems, there are all kinds of tables, programs, online calculators.
The main elements of the roof
The main elements of a gable roof, like any other roof truss, are:
Rafter roof with attic
To fully use the space under the roof, you can design an attic.
Attic floor- This is the floor in the attic space. The facade of the attic is completely or partially formed by the roof surfaces. According to regulatory documents, in order for a room to be considered an attic, the line of intersection of the roof plane and the outer wall should not be higher than 1.5 m from the floor level. If this requirement is not met, the space will be considered a normal floor.
The roof of the attic floor differs from the roof of the attic floor by the presence of a heater in its design. Most often, mineral wool boards are used to insulate the attic roof.
Lighting of the attic space can be carried out in three ways:
- window openings in the gables;
- dormers;
- roof windows.
dormer window - this is a window structure that has a frame mounted simultaneously with the truss system. This frame is made of wood. The dormer has its own small roof, which can be gable or cylindrical. The double-glazed window is installed vertically.
roof window- This is a window specially designed for use on a rafter roof. It is installed in the plane of the slope in an inclined position. The roof window must withstand the calculated snow load. It is better not to use this type of windows in roofs with a slight slope.
The choice of roofing material
After the appearance of the roof is determined, you can proceed to the choice of material. There are several types of modern coatings. In the list below, material options are listed in descending order of average market value.
- Ceramic tiles.
Ceramics as a roofing material has a long history. The ceramic roof is reliable and durable. The disadvantages of this material are the price and the large mass. Under the roof of ceramic tiles, you will have to arrange a reinforced truss system and crate; - Cement-sand tiles.
It has almost all the characteristics of ceramic, but costs a little less; - Flexible shingles.
It has good soundproofing characteristics. Thanks to the rough surface, the tiles are able to prevent snow from moving off the roof. Requires a continuous crate, usually a layer of moisture-resistant plywood is used. Cannot be used on roofs with large slopes; - Metal tile.
Compared to previous coatings, it is lighter in weight. Easy to mount. The disadvantage of a metal roof is that it can be too noisy when it rains. - seam roof.
The most attractive option in terms of cost. It requires special qualifications during installation, since it will be difficult for a non-professional to make high-quality connections. Installation is more laborious than that of metal and flexible tiles. The same "noisy" as metal tiles.
The material of the roof depends entirely on the desires and capabilities of the customer. The exception is roofs with too much or too little slope, since all materials have limits on the slope of the slope.
Types of truss systems
Structural roof truss systems can be of three types:
- Rafters.
The rafters rest on two sides. From below - on the Mauerlat, from above - on the crossbar. Racks and struts can be used as intermediate supports. Most often used in buildings with a small distance between the ends or, if possible, put racks or a wall in the middle of the attic.
With large spans of rafters (large distances between the longitudinal walls), racks, struts or puffs can be additionally used.
Laminated rafters are easy to calculate.
Usually the most powerful element of such a system is the crossbar, which bears half the load of the entire roof structure. - Hanging rafters.
In the absence of the possibility of using a crossbar as an upper support, it is reasonable to use this truss system.
Hanging rafters rest only on the Mauerlat, and at the top point they are interconnected with the help of an overlay.
This truss system works like a truss under load. The greatest pressure falls on the outer walls. There is a horizontal force - thrust, which can lead to displacement of the walls. In the design of hanging rafters, the expansion force is perceived by a puff, which tightens the rafter legs and prevents them from moving apart.
Hanging rafters are classified depending on the location of the puff:
1) Triangular three-hinged arch.
The puff and rafters form a triangle. The puff is located at the level of the overlap;
2) Triangular three-hinged arch with suspension.
With a large span of rafters, the tightening may not pass according to the deflection requirements. To prevent it from sagging, the puff is suspended from the ridge. But with such a system, as well as with a system of layered rafters, a row of racks is formed in the middle of the attic;
3) Triangular three-hinged arch with a raised puff.
The puff is most often located at the level of the ceiling of the attic room. Such a scheme is less beneficial from the point of view of the design. The higher the puff is located, the greater the thrust it perceives.
Hanging rafters must be considered as a triangular truss, which complicates the calculation. - Combined rafters.
The combined system includes spacer layered rafters. They need both bolt installation and tightening. Unlike the previous options, in which the rafters are hinged to the Mauerlat, here the rafter leg is rigidly attached, so there is a thrust in the system. For such a system, the Mauerlat must be securely attached to the wall, and the wall itself must be strong and thick. An excellent option would be to run a reinforced concrete belt around the perimeter.
Installation of the truss system
Installation takes place in the following order:
- mauerlat laying;
- installation of a crossbar (if any);
- layout of rafters;
- insulation (if any);
- crate;
- roofing material.
Attaching the rafter leg to the Mauerlat can be rigid and articulated.
Hinged fastening
It makes it possible to compensate for the expansion of wood under the influence of humidity and temperature changes.
Fastening can be done in several ways:
- using special fasteners, a metal "sled";
- using a mounting plate;
- washed down on the rafter leg. The junction of the rafter leg and the Mauerlat is fixed with nails.
Rigid fastening
The rafter is attached to the Mauerlat with a notch and securely fixed with nails hammered at an angle with respect to each other. One nail is driven vertically into the surface of the Mauerlat. Such a connection excludes displacement in any plane.
The gable truss system has undeniable advantages. You can design and install it yourself, you just need to take this issue responsibly and think through everything to the smallest detail.
The roof, along with the foundation and walls, is one of the main structural elements of the structure, protecting the interior of the building from precipitation, waterlogging, temperature changes, wind loads and other influences. At the same time, the roofing system is the most bulky structure in the house, difficult to erect, since it consists of a huge number of individual components and connections. For most novice craftsmen, construction turns into continuous test, which has no end in sight - it is necessary to draw up a project, carry out many calculations, draw diagrams, make elements and, ultimately, assemble everything into a single structure.
The online construction calculator for calculating the roof from the KALC.PRO service allows you to facilitate the process of erecting a roof structure at the stage of preparatory work, providing a detailed report with the parameters of individual elements and quantity of lumber for their manufacture, providing detailed drawings truss system and battens, as well as visualizing the resulting structure in the form 3D models for later evaluation. In addition, our program takes into account all additional structural elements of the roof, including mauerlat, vapor barrier, insulation, counter-battens, OSB sheets. In the near future, it is planned to introduce accounting for wind and snow loads.
The 3D roof constructor is simple, convenient and does not require special skills to use - you will need to measure the dimensions of the building, select the type of roof (hard, soft) and indicate the characteristics of the materials used. If invalid values are entered, the program will stop the calculation and indicate the cell where the error was made. Also on the tab of each calculator there is a detailed text instruction describing all the fields and symbols, which are duplicated on the corresponding images for clarity.
Save time and money using a professional roof calculation on the KALC.PRO website - we have been counting roofs for more than 5 years and have helped to implement over 1000 different projects!
Why are our tools better?
Close cooperation with roof manufacturers
Highest detail drawings and 3D models
Final report with a list of required materials
Ready estimate for the manufacture of the structure by the contractor
Technical support helps when working with the calculator
Positive feedback and a large number of completed projects
You can calculate the roof on any site and this is a fact, but you must be aware that, unlike other resources, our project has a long history, positive reviews, operational technical support and regularly updates the algorithms of work, eliminating the occurrence of errors. Feedback from users is established and works flawlessly, any visitor can ask a question, and KALC.PRO will try to answer it.
In addition, we would like to highlight the following:
- Constructor functionality. Our tools provide ample opportunities for designing a structure - you can set the characteristics of any element, and in case of entering invalid values, the program stop calculation and will indicate in which field the error was made.
- Cooperation with professionals. Service KALC.PRO actively cooperates with manufacturers and designers of roofing systems, so only with us you can find such detailed study separate nodal connections.
- Ready estimate. Upon completion of the calculation, the user receives not only a standard report with the parameters of structural elements and a set of drawings, but also detailed estimate with the amount of materials needed for manufacturing.
- Graphic arts. The main advantage of our service is high-quality detailed graphics, which is as close as possible to the standards of technical documentation. We also provide free interactive 3D model , with which you can evaluate the advantages / disadvantages of the chosen design.
- . If you are having difficulty using the calculator or have questions regarding the resulting calculation, we will look into the situation and we will try to answer for any constructive questions 24/7.
- Personal Area. Also on our website there is a convenient personal account in which the results of the calculation of the roof or any other structure are saved - you never lose your project, and you can also download the download at any time, regardless of the time of the operation.
In the comments to each calculator and on the "Reviews" page, you can read the messages of real people who use our tools. Check for yourself what users write about us.
Constructor Features
The KALC.PRO service is a universal assistant for beginners and professional craftsmen, with which you can make a really reliable and safe design. However, it must be understood that the program performs roof calculations based on the entered data and does not take into account their correctness, except in exceptional cases when the structure is guaranteed to be unstable. When building a roof (especially for the first time), we recommend paying attention to the following regulatory documents: SNiP 2.01.07-85 (SP 20.13330.2010) "Loads and Impacts", SNiP II-26-76 (SP 17.13330.2017) " Roofs”, TSN 31-308-97 “Roofs. Technical requirements and acceptance rules. Moscow region”, SP 31-101-97 “Design and construction of roofs”.
At present, we provide the calculation of the following roof structures:
- the roof is shed;
- gable roof (two-slope, gable);
- four-slope roof (hip);
- hipped roof (hipped).
Among the main features of the constructor, it is necessary to highlight (- only on KALC.PRO):
Our professional roofing calculators are used by many professionals - if you want to use them commercially, you can remove our watermark and upload your logo.
The result of the calculation of the roof
After entering all the initial parameters, you will receive a comprehensive report that contains a ready-made estimate for the manufacture of the structure with a detailed calculation of lumber and roofing, a set of drawings of all roof elements in various projections and an adaptive 3D model. Also, the roof area will be automatically calculated and an indicator of the angle of inclination of the slope, rafters will be available. Unlike other services, we disclose each element of the structure in detail and do not generalize the parameters so that you can use our results as a guide. guides to action.
Roof drawings with dimensions
Drawings are an integral element of the design documentation of any structure, since they represent a kind of "working card" for installation work. Many professionals prefer to make a roof plan with their own hands in specialized programs such as AutoCAD, ArchiCAD, etc., however, for a novice master, independent development without proper work experience usually ends without even starting, or ends very badly. It must be remembered that any accidental mistake can lead to unforeseen expenses and disruption of the structure of the entire structure.
Using the KALC.PRO online roof calculator, you eliminate errors in calculations, since the graphics are based on the actual parameters entered, the correctness of which can be double-checked on an interactive 3D model. Depending on the roof structure, we provide a different number of drawings - complex systems are described in more detail. For example, when calculating a bulky hip roof, the kit contains 12 design drawings with a detailed description of the truss system (in different projections), its elements, lathing, saw cuts and laying of roofing materials.
When creating the roof calculator, we made every possible effort to ensure that the subsequent assembly of the structure and the layout of individual elements, in particular, was as fast and comfortable as possible.
3D model
Architectural visualization allows you to visually evaluate the planned structure in real proportions, make sure that the project is completed with high quality and without errors. Nevertheless, spatial modeling is a painstaking and technically complex process that cannot be performed without special skills, and for professional designers, such services cost quite a lot of money.
However, when you perform a roof calculation on our website, you get a FREE, responsive, dimensionally accurate 3D model that you can interact with and download in OBJ format to load into your editing software.
How to calculate the roof on the online calculator?
To calculate the roof on the online calculator, you must correctly fill in all the available fields and click the "Calculate" button. We recommend taking measurements as accurately as possible and rechecking the entered values several times in order to avoid problems when assembling the structure in the future, since a large number of elements may have to be re-manufactured.
Recall that our calculators have built-in functionality in order to perform:
- calculation of the truss system;
- lumber calculation;
- calculation of metal tiles;
- calculation of the roof area;
- calculation of the angle of inclination of the roof.
You do not need to look for other tools on the Internet or bother with manual calculations.
Detailed step-by-step text instructions with graphic annotations for each tool are provided on the tabs of the corresponding calculator in the Help section. We also offer to watch a short overview video of the calculation of the gable structure, which demonstrates the main features of the roof calculator.
- The area of any classical roof can be calculated using the formulas for the area of a rectangle, triangle, parallelogram, trapezoid: S = a×b, S = (a×h)/2, S = a×h, S = (a+b) × h/ 2, where a, b are the lengths of the sides, h is the height.
- The optimal roof slope for a full-fledged attic is 45 °.
- The angle of inclination of the roof directly depends on the climatic conditions of the region: in snowy areas there should be steep roofs, in windy areas - gently sloping.
- The angle of inclination of the roof depends on the roofing material: a rigid roof requires a steeper slope.
- The angle of inclination of the roof affects the final cost of the structure: a steep roof is more expensive than a flat one.
- The height of the roof is derived from the formula for the height of an isosceles triangle: H \u003d a × sin α, where H is the height directed to the base, a is the side (the length of the rafter leg along the slope), α is the angle at the base (applicable for gable roofs).
- The optimal value of the cornice overhang of the roof is in the range of 50-100 cm, but not less than the width of the blind area.
- The optimal value of the gable overhang of the roof should be in the range of 40-60 cm.
- The calculation of the roof must be made based on a load of at least 200 kg / m 2.
- It is recommended to equip the roof with through ventilation holes from the cornice overhang to the very ridge.
- All fixing materials (especially external) must be galvanized or made of stainless steel.
- All wood must be treated with flame retardants, antiseptics and antifungal agents.
- The wood moisture index for all structural elements should not exceed 18-22%.
- It is recommended to use wood of at least class 2, and for load-bearing elements - only class 1.
- The ideal roofing pie is in order from the inside out: vapor barrier, insulation, waterproofing (membrane), counter-lattice, crate, tile (or other material).
Mauerlat
- The optimal size of a bar for a Mauerlat is 150x150 mm, sometimes it is used - 50x150 mm.
- It is recommended to fasten the Mauerlat to the armored belt using studs. However, the beam must be insulated so that it does not come into direct contact with the concrete.
- The pitch of the studs for fastening the Mauerlat should not exceed 150 cm.
rafters
- The depth of the cut should not exceed 1/3 of the width of the board (optimally 1/4).
- The recommended board width and thickness for most designs is 150-180mm and 50-60mm, respectively. The cross section of the board is selected depending on the frequency of the pitch of the rafters and the potential load on the roof.
- The distance between the rafters should not be less than 60 cm and more than 120 cm.
- All connections are recommended to be fixed in two different ways.
- To increase the reliability of the bolted connection, it is recommended to use metal plates and corners.
- With a span width of more than 10 m, the mandatory installation of additional supporting structures (rails, struts, racks) is required.
crate
- The recommended board for the lathing is 25x100 mm, in case of heavy roofs - 40x150 mm.
- For hard roofing materials, it is recommended to install a dense sparse crate, for soft ones - with a wider pitch, since OSB sheets will be installed on top.
- The step of the crate is selected for each material individually and is specified by the manufacturer. On average, for a soft roof - 1-10 cm, ceramic tiles - 30-35 cm, metal tiles - 30-40 cm, corrugated board - 30-65 cm.
Insulation and warming
- It is recommended to buy roll insulation, since the slab is difficult to fix (especially alone) and it crumbles more.
- The recommended thickness of thermal insulation is 15 cm, the minimum is 10 cm.
- It is recommended to lay the vapor barrier with an overlap (10-20 cm) followed by gluing the joints.
- Waterproofing is best laid in two layers.
- Permissible deflection of waterproofing is not more than 15 mm.
The online roof calculation calculator from KALC.PRO is the most effective way to obtain project documentation for the manufacture of a reliable roof truss system and other structures.
The website of our company provides the widest selection of roofing materials from the best manufacturers for complete or partial replacement of roofing: natural ceramic tiles, soft bituminous tiles, metal seam roofs, roofs made of metal profile sheets, metal tiles with various types of protective and decorative coatings.
Prices from the manufacturer
Our company FS-Group is the official dealer of roofing materials manufacturers presented on our website, which guarantees the best prices for you.
Roofing material and installation warranty
When concluding an agreement with us for the installation of a turnkey roof, you simultaneously receive a guarantee for both roofing materials and installation work in one contract.
Calculation and selection of materials
Currently, the range of roofing materials is quite wide, because of this it is difficult to make the right choice. Call our qualified managers and they will help you choose exactly the material for your roof that you need.
field manager
If you need to accurately determine the cost of replacing the roofing, order the service of a manager to visit the facility. He will not only give advice on the choice of roofing material, but also calculate the required amount of it, as well as the required amount of additional materials, and show samples of materials.
All types of payments and credit
We accept all types of payments: cash, bank transfer, payment by bank card in our office and online. All operations for payment for goods are carried out on the principles of confidentiality and security of payment. It is possible to pay for goods on credit, for details, contact our managers.
Delivery to the object
When concluding a contract for the purchase of goods, a delivery service from our warehouse to the object is possible. In this case, you must contact our managers, as the cost of delivery depends on the distance to the object.
Experience over 12 years
We have been in the market of installation services for more than 12 years. We successfully apply the accumulated experience at the facilities of our clients. The experience of our teams allows us to take on the most complex projects and implement them with maximum quality.
When carrying out any construction work, including roofing, it is necessary to accurately calculate the material, both main and auxiliary. Thanks to a thoughtful approach to determining the required amount of roofing finish, as well as components and consumables (insulation, waterproofing, lathing, fasteners), you provide yourself with several advantages at once:
- You buy everything at once in one place, guaranteeing yourself a complete match of the material in color. The need to purchase material elsewhere, from a different batch, can lead to the fact that the difference in shades will be clearly visible on the finished roof. Why do you need it?
- Accurate calculation of the roof will help to avoid the need to subsequently buy additional material, and this requires time, effort, additional costs (there is a difference, bring everything you need with one car or hire special vehicles several times).
- Calculation of the roof from specialists is a guarantee of the absence of a large amount of unnecessary surplus. Then you also need to do something with them (sell, take them out of the site), and this is also a waste of time and money.
Before starting the construction of the roof, it is necessary to calculate the material. Especially for this, we have an online calculator on our website. Its main purpose is to help the buyer estimate the approximate cost of roofing material. Knowing the amount of metal tiles, corrugated board, flexible tiles that you will need to buy to cover the roof, you can calculate the approximate cost of the roof (excluding discounts and possible bonuses).
Also, the roof calculation calculator will allow you to calculate the approximate cost of the roofing work itself, since knowing the amount of material, this value can also be calculated. Knowing these figures, you will be able to fully prepare for such an important and responsible event as the purchase of material and the conclusion of a contract for roofing work.
Calculation results
Above the roof layout there are product profile switches, they will allow you to select the required profile, taking into account its working width and forbidden lengths. To view the layout of sheets on a ramp, select the ramp by clicking on it. Use the arrows to change the length of the sheets according to your need for the selected slope.Calculation results
Below are the parameters of your roof and the amount of material needed, taking into account the forbidden lengths and overlaps of the sheets. Then you can add the product to the cart and, if necessary, refuse any items in the cart.How does the online roof calculator work?
First of all, the determining factor in the calculation of the roof is its shape. When filling in the fields of the online calculator, you can select the type you need, this step will be the very first. You will be able to calculate a single-pitched, double-pitched, four-pitched hip, mansard roof, etc.
Also included in the online calculation of the cost of the roof are other parameters that affect the amount of material - the need for insulation, additional elements (overhangs, gutters, etc.). The greatest attention, of course, should be paid to the size of the roof. In order to obtain the most accurate calculation possible, refer to the drawing when specifying the dimensions.
As a result, the online calculator for the roof of the house will give you all the necessary numbers, taking into account the choice of the type of metal tile profile and the cost of all the necessary materials at Roofing No. 1. The program will calculate the total area of the roof, the cost of the finishing coating, additional elements, fasteners, as well as the cost of additional elements, if you indicate this when filling out the form (insulation, waterproofing, drainage system, spotlights). Also, the roofing cost calculator will calculate the amount for turnkey installation work. The final amount will reflect all your expenses, both for the purchase of material and for the installation process.
How to buy materials after calculating the roof?
You can order and buy everything you need for roof installation right here without leaving the calculator page. The order will be automatically generated in the basket, you can make all the changes you need to it, refuse some of the goods or services and calculate the final cost. You can pay for the purchase directly through the site using a bank card, cashless transfer. Cash payment is made at the office of the company.
It is very convenient, it allows you to save your time and money, and also to purchase everything you need for the roof in one place, without tiring trips in search of the necessary materials.
This online calculator allows you to get a fairly accurate preliminary calculation, which is especially suitable for those who plan to build a roof of a simple form. If there is a project for a complex, multi-pitched roof with dormer windows, it is best to contact the specialists of Roofing No. 1 for a cost calculation.
The roof of the house is a load-bearing structure that takes on all the external load (the weight of the roofing pie, its own weight, the weight of the snow cover, etc.) and transfers it to all the load-bearing walls of the house or to internal supports.
In addition to its aesthetic and load-bearing functions, the roof is an enclosing structure, separating the attic from the external environment.
The basis of the roof of any house is the truss system.
This is the frame to which the roof is attached.
It is this skeleton that takes all the loads.
The truss system consists of:
- rafter legs;
- Mauerlat;
- side runs and ridge run;
- braces, diagonal ties, braces.
When all these elements (except for the Mauerlat) are interconnected, a truss truss is obtained.
The basis of such a farm is a triangle, which is the most rigid of the geometric shapes.
The main element of the roof frame are the rafters.
Rafter calculation
Before you directly start calculating the rafters, you should find out what loads will affect the roof of the house.
That is, on rafter legs.
The loads acting on the roof frame are usually divided into constant and variable.
Constants are those loads that act constantly, regardless of the time of day, season, etc.
This is the weight of the entire roofing pie, the weight of additional equipment that can be installed on the roof (fencing, snow guards, aerators, antennas, etc.).
Variable loads appear at certain times of the year.
For example, snow.
When snow falls on the roof, this is a very decent weight.
In any case, it should be taken into account.
The same with the wind.
It is not always there, but when a strong wind blows, a fairly large wind force acts on the roof frame.
And an inexperienced person is unlikely to succeed.
Although it's worth a try.
Just when calculating, you need to remember a large number of different factors that affect the roof.
At least the weight of the truss system itself with all the elements and fasteners.
Therefore, professionals use special computer programs and calculators to calculate rafters.
How to find out the load on the rafter legs?
The collection of loads should begin with determining the weight of the roofing cake.
If you know what materials will be used and the area of \u200b\u200bthe slopes, then it is not difficult to calculate everything.
It is customary to calculate how much 1 square meter of roof weighs.
And then multiply by the number of squares.
For example, let's calculate the weight of a roofing pie.
The roofing material is ondulin:
- Ondulin. A square meter of ondulin has a weight of 3 kg.
- Waterproofing. If polymer-bitumen insulation is used, then it weighs 5 kg / square meter.
- Insulation. The weight of one square of basalt wool is 10 kg.
- Crate. Boards 2.5 cm thick. Weight per square meter 15 kg.
We summarize all weights: 3+5+10+15= 33 kg.
Then the value obtained as a result of the calculations should be multiplied by a factor of 1.1.
This is a correction factor.
It turns out 34.1 kg.
How much does 1 sq. meter of our roofing cake.
And if the total area of our roof is 100 squares, then it will weigh 341 kg.
Snow load calculationThere is a map of snow loads.
It shows the amount of snow cover in each region.
We calculate the snow load using the following formula: S = Sg x µ.
Sg is the mass of snow cover.
µ is a correction factor.
And this coefficient depends on the angle of inclination of the slopes of your roof.
The larger this angle, the smaller the value of this coefficient.
At angles of inclination greater than 60 degrees, it is not used at all.
Since snow does not collect on the roof.
Calculate wind load
Just as the whole country is divided into regions according to the mass of snow, so it is also divided according to the strength of the winds.
And there is also a special map on which the strength of the wind is indicated in each area.
The following formula is used to calculate wind loads:
Wo - an indicator taken from the map.
k is a correction factor depending on the type of terrain where the building is located and its height.
We calculate the cross section of the rafter leg
The cross section of the rafters depends on three factors:
- from the length of the rafter;
- from the distance between the railings;
- from the loads acting on the roof.
Knowing these parameters, it is easy to determine from the table.
How to calculate the length of the rafter legs of a shed roof
Of all the types of roofs, pitched roofs are the simplest.
There are no complex elements in it at all.
And its installation is carried out on load-bearing walls, which have different heights.
Such a roof is arranged on garages, baths, utility rooms.
To calculate what will be the length of the rafters of a shed roof, you should determine the angle of inclination.
And the angle of inclination of the slope depends, first of all, on the type of roofing material that you want to use.
In the case when it is corrugated board, then the optimal angle of inclination is 20 degrees.
But it is forbidden to make an angle less than 8 degrees!
Otherwise, in the cold season, under the weight of the snow cover, the roof will not withstand and simply fail.
If you will lay metal tiles, then the minimum angle of inclination increases to 25 degrees.
When using slate - 35 degrees.
If the roof is folded, then the angle of inclination can be different: 18 - 35 degrees.
After you figured out the angle of the slope, you need to raise the back wall to such a height that you get the desired angle.
The most difficult thing in such calculations is to find the sine and tangent.
But for this they use this sign:
| Roof slope angle, degrees | Tangent tgA | sine sinA |
|---|---|---|
| 5 | 0,09 | 0,09 |
| 10 | 0,18 | 0,17 |
| 15 | 0,27 | 0,26 |
| 20 | 0,36 | 0,34 |
| 25 | 0,47 | 0,42 |
| 30 | 0,58 | 0,5 |
| 35 | 0,7 | 0,57 |
| 40 | 0,84 | 0,64 |
| 45 | 1,0 | 0,71 |
| 50 | 1,19 | 0,77 |
| 55 | 1,43 | 0,82 |
| 60 | 1,73 | 0,87 |
For example, let's find the length of the rafter and the height of the elevation of the facade wall for a house 5 meters long.
The tilt angle is 25 degrees.
To determine the height of the front wall rise Lbc x tg 25 = 5 x 0.47 = 2.35 meters.
Accordingly, the length of the rafter leg Lc = 2.35 x 0.42 = 5.6 meters.
And do not forget to add the length of the front and rear overhangs to the resulting length, which are necessary in order to provide the walls of the building with protection from slanting rain.
On average, the length of one overhang is 0.5 meters.
If required, this length can be longer.
But less than 0.5 meters is impossible.
This means that 1 meter should be added to the length of the rafter: Lc \u003d 5.6 + 1 \u003d 6.6 meters.
Calculation for a gable roof
The truss system of a gable roof is much more complicated than the truss system of a shed roof.
There are more elements, and the principle of its operation is somewhat different.
To calculate the length of the rafter leg, we use the Pythagorean theorem. 
If you look at the right triangle shown in the figure, you can see that the hypotenuse b is our rafter.
And its length is equal to the length of the leg, divided by the cosine of a specific slope angle.
For example, if the width of the house is 8 meters, and the slope of the slopes is 35 degrees, then the rafter leg will have a length of:
b \u003d 8 / 2 / cos 35 \u003d 8 / 2 / 0.819 \u003d 4.88 meters.
Now it remains to add the length of the visor, about 0.5 meters, to get the desired length of the rafters.
It should be said that these are simplified versions of the calculations of rafters.
In order to get the most accurate data, it is best to use special programs.
For example, the free Arkon program.
The built-in calculator, according to the parameters you set, will automatically calculate both the cross section of the rafter leg and the length of the rafter.
Video about the rafter calculation program.
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