Calculator for calculating a gable roof, rafters and sheathing. Rafter system of a gable roof: calculation of rafters for various coatings. Video: hip roof rafter system

The roof, along with the foundation and walls, is one of the main structural elements of the structure, providing protection to 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, difficult-to-build structure in the house, since it consists of a huge number of individual components and connections. For most beginning craftsmen, construction turns into full test, which has no end in sight - it is necessary to draw up a project, carry out many calculations, draw diagrams, manufacture elements and, ultimately, assemble everything into a single structure.

The online construction calculator for roof calculations from the KALK.PRO service allows you to facilitate the process of erecting a roofing 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 rafter system and sheathing, as well as visualizing the resulting structure in the form 3D models for subsequent evaluation. In addition, our program takes into account all additional structural elements of the roof, including Mauerlat, vapor barrier, insulation, counter-lattice, OSB sheets. It is planned to introduce wind and snow load recording soon.

The 3D roof designer 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 exactly the error was made. Also on the tab of each calculator there is a detailed text instruction with a description of all fields and symbols, which are duplicated in the corresponding images for clarity.

Save time and money by using professional roof calculations on the KALK.PRO website - we have been calculating roofs for more than 5 years and have helped implement over 1000 different projects!

Why are our tools better?

Close cooperation with roof manufacturers

Highest detail in drawings and 3D models

Final report with a list of required materials

Ready-made estimate for the construction 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 website and this is a fact, but you should be aware that, unlike other resources, our project has a long history, positive reviews, prompt technical support and regularly updates its work algorithms, eliminating the occurrence of errors. Feedback with users is established and works flawlessly; any visitor can ask a question, and KALK.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 customize the characteristics of any element, and if you enter invalid values, the program will stop calculation and will indicate in which field the error was made.
• Cooperation with professionals. The KALK.PRO service actively cooperates with manufacturers and designers of roofing systems, so only here you can find such detailed study separate node 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 production.
• Graphic arts. The main advantage of our service is high-quality detailed graphics, which are 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 selected design.
• . If you experience difficulties using the calculator or have questions regarding the resulting calculation, we will look into the situation and we'll 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 calculating a roof or any other structure are saved - you you'll 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 messages from real people who use our tools. Check for yourself what users write about us.

Designer capabilities

The KALK.PRO service is a universal assistant for beginners and professional craftsmen, with the help of which you can make a truly reliable and safe design. However, it is necessary to understand that the program calculates the roof 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".

We currently provide calculations for the following roofing structures:

• roof is pitched;
• gable roof (gable, gable);
• hip roof;
• The roof is hipped (hipped).

Among the main features of the designer, it is necessary to highlight ( - only on KALK.PRO):

Our professional roofing calculators are used by many professionals - if you want to use them for commercial purposes, you can remove our watermark and upload your logo.

Roof calculation result

After entering all the initial parameters, you receive a comprehensive report, which contains a ready-made estimate for the manufacture of the structure with detailed calculations of lumber and roofing, a set of drawings of all roof elements in various projections and an adaptive 3D model. The roof area will also be automatically calculated and the angle of inclination of the slope and rafters will be available. Unlike other services, we reveal each element of the structure in detail and do not generalize the parameters so that you can use our results as guidelines for action.

Roof drawings with dimensions

Drawings are an integral element of the design documentation of any structure, since they represent a kind of “working map” 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 before it even begins, or ends very badly. It must be remembered that any accidental mistake can lead to unexpected expenses and disruption of the structure of the entire structure.

Using the online roofing calculator KALK.PRO you eliminate errors in calculations, since the graphics are built based on the actually entered parameters, the correctness of which can be double-checked on an interactive 3D model. Depending on the roof design, 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 rafter system (in different projections), its elements, sheathing, places of cuts and laying of roofing materials.

When creating the roofing 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, making sure that the project is completed with high quality and without errors. However, spatial modeling is a painstaking and technically complex process that cannot be performed without special skills, and such services cost quite a lot of money from professional designers.

However, when you perform a roof calculation on our website, you receive a FREE, adaptive, dimensionally accurate 3D model that you can interact with and download in OBJ format to later load into your editing software.

How to calculate a roof using an online calculator?

To calculate the roof using 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 double-checking the entered values ​​several times in order to subsequently avoid problems when assembling the structure, since you may have to re-manufacture a large number of elements.

Let us remind you that our calculators have built-in functionality to perform:

• calculation of the rafter system;
• lumber calculation;
• calculation of metal tiles;
• roof area calculation;
• calculation of the roof slope angle.

You don't need to look for other tools on the Internet or bother with manual calculations.

Detailed step-by-step text instructions with graphical annotations for each tool are provided on the corresponding calculator tabs in the Help section. We also suggest watching a short overview video of calculating a gable structure, which demonstrates the main capabilities of the roof calculator.

• The area of ​​any classic 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 angle for constructing a full 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 - flat ones.
• The angle of the roof depends on the roofing material: a rigid roof requires a steeper slope.
• The angle of the roof affects the final cost of the structure: a steep roof costs more than a flat one.
• The height of the roof is derived from the formula for the height of an isosceles triangle: H = a × sin α, where H is the height directed towards the base, a is the side (the length of the rafter along the slope), α is the angle at the base (applicable for gable roofs).
• The optimal value of the eaves overhang of the roof is in the range of 50-100 cm, but not less than the width of the blind area.
• The optimal size of the gable roof overhang should be in the range of 40-60 cm.
• Roof calculations must be made based on a load of at least 200 kg/m2.
• It is recommended to equip the roof with through ventilation holes from the eaves overhang to the ridge.
• All fastening materials (especially external ones) must be galvanized or made of stainless steel.
• All wood must be treated with fire retardants, antiseptics and antifungal agents.
• The wood moisture content 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, sheathing, tiles (or other material).

Mauerlat

• The optimal size of timber for the Mauerlat is 150x150 mm, sometimes 50x150 mm is used.
• It is recommended to fasten the Mauerlat to the armored belt using studs. However, the timber must be insulated so that it does not come into direct contact with the concrete.
• The pitch of the studs for attaching 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 width and thickness of the board for most designs is 150-180 mm and 50-60 mm, respectively. The section of the board is selected depending on 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.
• It is recommended to fix all connections in two different ways.
• To increase the reliability of bolted connections, it is recommended to use metal plates and angles.
• When the span width is more than 10 m, the mandatory installation of additional supporting structures (rails, struts, racks) is required.

Lathing

• The recommended board for sheathing is 25x100 mm, in the case of heavy roofs - 40x150 mm.
• For hard roofing materials, it is recommended to install dense sparse lathing, for soft ones - with a wider pitch, since OSB sheets will be installed on top.
• The pitch of the lathing is selected individually for each material 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 sheets - 30-65 cm.

Insulation and insulation

• It is recommended to buy rolled thermal insulation, since slab insulation is difficult to fix (especially alone) and is more likely to crumble.
• The recommended thermal insulation thickness is 15 cm, the minimum is 10 cm.
• It is recommended to lay the vapor-waterproofing in an overlap (10-20 cm) with subsequent gluing of the joints.
• It is better to lay waterproofing in two layers.
• The permissible deflection of waterproofing is no more than 15 mm.

The online roof calculation calculator from KALK.PRO is the most effective way to obtain design documentation for the manufacture of a reliable roof truss system and other structures.

Metal tiles appeared in a series of roofing materials relatively recently, but quickly gained popularity. This can be explained simply - when installed correctly, such a cover provides reliable protection of the house from precipitation, while at the same time giving the roof a reliable imitation of natural classic tiles.

The popularity of this coating is also based on the fact that its installation is not particularly difficult, and the owner of the house must cope with it even on his own, naturally, having an assistant, but without resorting to hiring a team. The clear profile of the metal tile allows you to combine adjacent sheets without much difficulty, and it is very difficult to make a mistake even if you want to. But all this will be fair only if high-quality sheathing is installed under such a roof. A calculator for calculating lumber for lathing under metal tiles will help you figure out how many boards or timber will be needed to create it.

Below are some comments about working with the program.

The roof of a house is a load-bearing structure that takes on the entire 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 space from the external environment.

The basis of the roof of any house is the rafter system.

This is the frame to which the roof is attached.

All loads are taken by this skeleton.

The rafter system consists of:

• rafter legs;
• Mauerlat;
• side purlins and ridge purlins;
• struts, diagonal braces, braces.

When all these elements (except for the Mauerlat) are connected to each other, a roof truss is obtained.

The basis of such a truss is a triangle, which is the most rigid of the geometric shapes.

The main element of the roof frame is the rafters.

Calculation of rafters

Before you begin directly calculating the rafters, you should find out what loads will affect the roof of the house.

That is, on the rafter legs.

Loads acting on the roof frame are usually divided into constant and variable.

Constant loads 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.

It's the same with the wind.

It's not always there, but when the wind blows strong, there's quite a lot of wind force acting on the roof frame.

And an inexperienced person is unlikely to succeed.

It's worth a try though.

When making calculations, you just need to remember a large number of different factors that influence the roof.

At least the weight of the rafter 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 pie.

If you know what materials will be used and the area of ​​the slopes, then calculating everything is easy.

It is customary to calculate how much 1 square meter of roofing weighs.

And then multiply by the number of squares.

Let's calculate the weight of a roofing pie as an example.

The roofing material is ondulin:

1. Ondulin. A square meter of ondulin weighs 3 kg.
2. Waterproofing. If polymer-bitumen insulation is used, then it weighs 5 kg/square meter.
3. Insulation. The weight of one square of basalt wool is 10 kg.
4. Lathing. The boards are 2.5 cm thick. Weight per square meter is 15 kg.

We sum up all the 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 square meters, then it will weigh 341 kg.

There is a snow load map.

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 the snow cover.

µ—correction factor.

And this coefficient depends on the angle of inclination of the slopes of your roof.

The larger this angle, the lower the value of this coefficient.

At tilt angles greater than 60 degrees, it is not used at all.

Since snow does not collect on the roof.

Calculating wind load

Just as the whole country is divided into regions according to the mass of snow, it is also divided according to the strength of the winds.

And there is also a special map on which the wind strength is indicated in each area.

To calculate wind loads, use the formula:

Wo - indicator taken from the map.

k is an adjustment 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:

• on the length of the rafters;
• on the distance between the railings;
• from 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 pitched roof

Of all the types of roofs, the shed roof is the simplest.

There are no complex elements in it at all.

And it is installed on load-bearing walls that have different heights.

This kind of roofing is installed on garages, bathhouses, and utility rooms.

To calculate what the length of the rafters of a pitched roof will be, you need to 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 sheeting, the optimal angle of inclination is 20 degrees.

But it is prohibited to make an angle less than 8 degrees!

Otherwise, in the cold season, the roof will not withstand the weight of the snow cover and will simply fail.

If you lay metal tiles, the minimum tilt angle increases to 25 degrees.

When using slate - 35 degrees.

If the roof is seam, then the angle of inclination can be different: 18 - 35 degrees.

After you have 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 the following sign:

For example, let's find the length of the rafters and the height of the facade wall for a house 5 meters long.

The tilt angle is 25 degrees.

To determine the height of the front wall, Lbc x tg 25 = 5 x 0.47 = 2.35 meters.

Accordingly, the length of the rafter leg is Lc = 2.35 x 0.42 = 5.6 meters.

And do not forget to add to the resulting length the length of the front and rear overhangs, 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 = 5.6 + 1 = 6.6 meters.

Calculation for a gable roof

The rafter system of a gable roof is much more complex than the rafter 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 the specific angle of inclination of the slopes.

For example, if the width of the house is 8 meters, and the angle of inclination of the slopes is 35 degrees, then the rafter leg will have the length:

b= 8 / 2 / cos 35 = 8 / 2 / 0.819 = 4.88 meters.

Now all that remains is to add the length of the canopy, approximately 0.5 meters, to get the required length of the rafters.

It should be said that these are simplified options for rafter calculations.

In order to obtain the most accurate data, it is best to use special programs.

For example, the free program "Arkon".

The built-in calculator, based on the parameters specified by you, will automatically calculate both the cross-section of the rafter leg and the length of the rafter.

Video about the rafter calculation program.

Our company’s website provides the widest selection of roofing materials from the best manufacturers for complete or partial replacement of roofing: natural ceramic tiles, soft bitumen 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 an official dealer of the companies producing roofing materials presented on our website, which guarantees the best prices for you.

Warranty for roofing material and its installation

When concluding a turnkey roofing installation agreement with us, you simultaneously receive 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, which makes it 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 visiting the site. He will not only give advice on choosing roofing material, but will also calculate the required amount, 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 credit card in our office and online. All transactions 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 more details, please contact our managers.

Delivery to the site

When concluding a contract for the purchase of goods, a delivery service from our warehouse to the site is possible. In this case, you need to contact our managers, since the cost of delivery depends on the distance to the object.

Experience more than 12 years

We have been in the installation services market for more than 12 years. We successfully apply the accumulated experience at our clients’ sites. The experience of our teams allows us to take on the most complex projects and implement them with maximum quality.

Specify the parameters of wooden rafters:

B– rafter width, an important parameter that determines the reliability of the rafter system. The required cross-section of the rafter (in particular the width) depends on: loads (constant - the weight of the sheathing and roofing pie, as well as temporary - snow, wind), the material used (quality and its type: board, timber, laminated veneer lumber), the length of the rafter leg, distances between rafters. You can determine the approximate cross-section of the beam for the rafters using the table data (the width value is the larger value from column 3, for example, with a rafter length of up to 3000 mm and a pitch of 1200 mm, the desired width value is 100 mm). When choosing the width of the rafters, be sure to take into account the recommendations given in SP 64.13330.2011 “Wooden Structures” and SP 20.13330.2011 “Loads and Impacts”.

Y– roof height, distance from the ridge to the attic floor. Affects the angle of inclination of the roof. If you plan to equip a non-residential attic, you should choose a small height (less material will be required for rafters, waterproofing and roofing), but sufficient for inspection and maintenance (at least 1500 mm). If it is necessary to equip a living space under a roof vault, to determine its height, it is necessary to focus on the height of the tallest family member plus 400-500 mm (approximately 1900-2500 mm). In any case, you must also take into account the requirements of SP 20.13330.2011 (updated edition of SNiP 2.01.07-85*). It should be remembered that on a roof with a small angle of inclination (small height) precipitation can be retained, which negatively affects its tightness and durability. However, a high roof becomes more vulnerable to strong wind gusts. The optimal tilt angle is between 30-45 degrees.

X– The width of the roof (without overhangs) is determined by the width of the outer perimeter of your house.

C– the size of the overhang, an important structural element of the roof that protects the walls and foundation from precipitation, is determined taking into account the climatic conditions of your region (SP 20.13330.2011) and the general architectural idea. For one- and two-story houses without external water drainage, no less than 600 mm. If you arrange a drainage system, you can reduce it to 400 mm (SNB 3.02.04-03). According to the requirements of IRC-2012, paragraph R802.7.1.1 (International Building Code for 1-2 apartment individual residential buildings), the maximum length of the free overhang of rafters, which does not require the installation of additional support struts, is 610 mm. The optimal overhang size is considered to be 500 mm.

Z– this is the distance from the top edge of the rafter to the cut. Size Z is related to the width of the rafter by a simple ratio - no more than 2/3 of its width (neglecting this rule significantly reduces the load-bearing capacity of the rafter). The cut is necessary to attach the rafters to the mauerlat - a support that takes the load from the roof and redistributes it to the load-bearing walls.

By checking the “Black and white drawing” option, you will receive a drawing that is close to GOST requirements and will be able to print it without wasting color paint or toner.

Calculation results:

Length to rafter overhang– this size should be used to mark the cut of the rafters to the mauerlat.

Overhang length will show how far it is necessary to extend the rafter beyond the perimeter of the house to obtain a given roof overhang ( WITH) protecting from bad weather.

Having calculated total length of rafters and overhang It’s not difficult to find out the required amount of lumber of the required length and estimate how much reagents are needed to treat wood from rotting.

Calculation of the angle and section of the rafters: The cut angle is the angle at which the ends of the rafters must be cut to connect to each other. The beginning of the cut should be measured at the same angle to the edge of the rafter. To maintain the same cutting angle on all rafters, it is advisable to use a template.