One of the most important parts of the pitched roof is a rapid system consisting of durable and reliable beams. It is rafters that are the basis for the roof. It is important that the materials used can easily withstand not only the roofing structure, but also the pressure of snow or ice masses in the winter, as well as wind loads throughout the year. In this regard, before proceeding with the installation of rafters, the necessary calculations should be made, given all possible factors and nuances. Of course, it is possible to order the miscalculation of the rafter in various construction companies, however, a similar service will cost a fairly decent amount, therefore an optimal option can become an independent calculation. So how to calculate the rapid roof system correctly? Of course, before proceeding to the main issue, it is worth studying the features of rafters and a variety of design.

Features of the rafter system

To make the calculation of the rafter system, it should be understood that it represents. So, rafters are the supporting structure of the roof, which takes on all external loads, in the form of snow nansions, strong shower or squall winds. The main elements are:

• vertical racks are necessary for the maximum stability of the rafter system;
• stropyl inclined legs - determine the slope of the roof slide and its general view;
• ramans - allocate side and skate varieties of runs, elements are necessary for fastening and maintaining the rafter feet;
• tightening, Rigels - fixing elements;
• slopes - diagonal supporting bars that give strokes;
• konk - the top bar, stacked at the junction of two roofing rods;
• filkings - an element that allows to increase the length of not long rafters in the case of mounting the roof of the roof;
• the farm is a set of racks, squeaks, crates and other elements that make up the basis of the roofing system.



Getting Started with the calculation of rafters, the calculation of each individual element should be calculated. It is also important to comply with the requirements for the rafter system, it will help choose the right material, as well as create the most durable and durable roof.

Basic requirements when choosing a material rafters

Today, quite many owners of their own homes prefer roofing from wood. As a rule, the rafter system is made from coniferous wood. At the same time, the timber must have a humidity of no more than 20%. This is the so-called air-dry wood, which is characterized by the necessary strength and ease. In addition to the percentage of humidity, when choosing a tree, such conditions should be observed as:

• the presence of a minimum number of bitch, cracks and other possible defects, for this it is worth choosing wood 1 or 2 varieties. When choosing a tree of 3 varieties, you should pay attention to the 1 m board or timber, there are no more than 3-4 bitch with a height of up to 3 cm, and in the presence of cracks, their length and depth must be small;
• for carriers, capital elements, such as rafter legs, Mauerlat, Konk, and so on, it is recommended to use a ram with a thickness of more than 5 cm, optimally apply products with a square or rectangular cross section from 10 to 20 cm;
• when choosing coniferous boards, the length of products is allowed to 6.5 m, and if deciduous rocks are used, the lumber length should not exceed 4.5 m. As a rule, deciduous rocks are used for such constructive parts such as runs and Mauerlat. It is also worth giveing \u200b\u200bpreference to solid rocks.



Important! All the erected system must have rigidity and durability. That is, the finished design should have a reliable fixation and be fixed. If at least one element does not correspond to this requirement, then the likelihood that the roof can be destroyed with hurricane wind either with heavy snowfall, and it will not matter how it is correctly made by the calculation of wooden roof rafters. In the very deplorable situation, it will be destroyed not only the roof, but also the walls of the structure. It should also be borne in mind that the rafter system should be made easy, especially in the case when wooden bearing walls are used. To be able to apply strong and reliable beams, but it is not for the design, it is recommended to choose a lumber with a low percentage of humidity, that is, about 10-15%. Also, do not forget about the processing of wooden elements by antiseptics, antipirens, hydropobizats and other protective drugs. Before proceeding with the question, how to correctly calculate the rafter system, should obtain ideas about the types of rafters.

Video on the topic:


Varieties of Stropil

The specific type of rafters depends on the type of roof and, producing the calculation of the rafter system, it should be considered. For example, the roof can be two-tie or four-tie, respectively, the rafters will be calculated differently. In this case, the presence of structural elements and the principle of their installation remains practical unchanged. Today it is customary to allocate 2 main varieties of rafter systems.

1. Slot rafters - in this case, the rafter legs are based on the walls of the structure, and their middle pin the intermediate support. This system is mounted if necessary, if you make spars of more than 5-7 m. Each additional support can increase the flight length by 3-4 m.
2. - Installed when the distance between the outer walls, which is set to the rafter system of not more than 6.5 m.

By choosing a specific type of roof, as well as the type of the rafter system, you can move to the execution of all necessary calculations, that is, the calculation of the cross section of the rafted, load, length and height of the beams, and so on.

Terminal load calculation

Conducting the calculation of the rafted roof on its own, it is recommended to take enlarged parameters, so that you can have a certain stock of the roof strength. Of course, at the same time increase the consumption of building materials, however, the security issues of the house still should be taken to first place. So, the first thing is to take into account all the possible loads that will affect the roofing structure. In particular, this loads include snow and wind loads. Also, when calculating the load on the truss system, it is worth considering quite a lot of features. Including factors such as:

• the weight of the roofing material;
• weight of the crate;
• weight of insulation, hydro and vaporizolation;
• weight of the rafter system.

Only calculating each item, you can make the calculation of the rafter system. For example, the formula for calculating snow load will look like this:

S \u003d SURCH. · Μ,
where S is the desired parameter, SRASCH. - The value of snow weight per 1 sq. M, which should be taken from the SNIPOs operating on a certain territory, and μ is a coefficient calculated from the angle of inclination of the roof. To calculate wind load, you can also use the formula:

WM \u003d WO · k · C,
where Wo is the normative parameter of the wind pressure, determined by the slope in effect in the region, K is a coefficient, wind pressure, depending on the height of the roof over the ground and C is an aerodynamic coefficient that depends on the form of the roof. Knowing all the initial values \u200b\u200bto make calculations will not be difficult. However, today is not necessarily all the necessary measurements and calculations in manual mode. After all, special programs have been created for these purposes, for example, a program for calculating a rafter system or a rafaling and farm calculation program. These programs include:

• STROPILA;
• AutoCAD;
• Arcon;
• Online calculation services (building calculators).

What is the principle of such software? It is pretty simple, you must enter all the parameters from the SNIPs or the structure of the structure into the corresponding windows or lines, and then click the "Calculate" button and the program will give the result. As a rule, these resources include all the necessary calculations, that is, the wind and snow load, as well as the calculation of the total load, the calculation of the distributed load, the calculation of the rafter system, and so on. Also in programs there are cards with the value of wind pressure and the weight of snow cover in all regions. To make calculations in such applications, not even prepared users will be able, while all parameters will be the most accurate. In addition, it should be borne in mind that certain parameters are constant and they can be found in the instructions for building materials or on the Internet.

View of the roofing and its weight

Depending on which it is planned to use the material for the roof, the load on the rafter systems is changed. Almost all types of coatings have a fixed weight, due to which it is fairly easy to make calculation. Consider the weight of the main varieties of roofing coatings that provide manufacturers in the manufacture.

As for the mass of draft flooring, a rafter system and crates, then these values \u200b\u200bare considered standard. In particular, the rough roofing design will have a weight of 18-20 kg / sq. M, a wooden cutter - 8-10 kg / sq. M and rafters - 15-20 kg / sq. M. Summarizing all values \u200b\u200bcan be easily found a desired load parameter on the rafter system.

Calculation of timber

After the load is defined, you can proceed to such a paragraph as the calculation of the rafter system. It is necessary to determine the load on each rafter foot to understand how the cross section should be at the rafter, their strength and how much forests need for rafters in each case. The formula for calculating the load on each rafter foot is as follows:

QR \u003d A · Q,
where QR is the desired value measured in kg / m, and -, measured in meters and q - this is a total load acting on 1 sq. M of the roof, is measured in kg / sq. M. (This amount was found in the calculations produced Earlier). Calculate the load is also possible in automated mode, using programs. Various applications make it possible to make the calculation of the cross section of the rafter, their number, height and many other parameters. Important! By producing the calculation of the rafter system, the parameters should always be rounded into the most side, as it allows you to increase the strength of the roofing structure.

Make the necessary calculations yourself is not at all difficult. Of course, if knowledge in this question is not enough, you can always contact the specialists. However, a huge variety of automated programs can help cope with the calculation of the rafter system without much trouble. It is important to remember that not only the strength and reliability of the roof depends on the correctness of the calculations, but also the safety of residents at home.

We present the free calculator for the calculations of the bartal roof. Online calculation of the crates, the angle of inclination of the rafted and the required amount of materials.

Specify the roofing material:

Choose a material from the list - slate (wavy asbetic sheets): medium profile (11 kg / m2) Slate (wavy asbetic sheets): reinforced profile (13 kg / m2) wavy pulp-bitumen sheets (6 kg / m2) bitumen (soft , flexible) tile (15 kg / m2) from galvanized tin (6.5 kg / m2) sheet steel (8 kg / m2) ceramic tile (50 kg / m2) cement-sand tile (70 kg / m2) metal tile, professional flooring (5 kg / m2) Ceramoplast (5.5 kg / m2) Folding roof (6 kg / m2) Polymer-sand tile (25 kg / m2) Ondulin (erector) (4 kg / m2) Composite tile (7 kg / m2 ) Natural slate (40 kg / m2) Specify the weight of 1 sq. Cover meter (? Kg / m2)

kg / m 2

Enter the roof parameters:

Base width A (cm)

Foundation length D (cm)

Lifting height B (cm)

Length of side skes with (cm)

The length of the front and rear swell E (cm)

Rafters:

Step rafal (cm)

Wood grade for rafters (cm)

Working section of the side rafter (not necessarily) (cm) "\u003e

Calculation of doom:

Width of the Grubel Board (cm)

Baseline thickness (cm)

Distance between boards dolets
F (cm)

Snow load calculation:

Choose your region using the map below.

1 (80/56 kg / m2) 2 (120/84 kg / m2) 3 (180/126 kg / m2) 4 (240/168 kg / m2) 5 (320/224 kg / m2) 6 \u200b\u200b(400/280 kg / m2) 7 (480/336 kg / m2) 8 (560/392 kg / m2)

Calculation of wind load:

Ia II III IV V VI VII

Building height

5 m from 5 m to 10 m from 10 m

Type of terrain

Open area Closed terrain city districts

Results of calculations

Roof inclination angle: 0 degrees.

The angle of inclination is suitable for this material.

The angle of inclination for this material is desirable to increase!

The angle of inclination for this material is desirable to reduce!

Roof surface area: 0 m 2.

Approximate weight of roofing material: 0 kg.

The number of rolls of insulating material with the adoption of 10% (1x15 m): 0 rolls.

Rafters:

Load on the truss system: 0 kg / m 2.

Length raftered: 0 cm.

Number of rafters: 0 pcs.

Obsek:

The number of rows of crates (for the whole roof): 0 rows.

Uniform distance between the shell boards: 0 cm.

Number of clamping boards standard 6 meters long: 0 pcs.

Scope Board Volume: 0 m 3.

Approximate weight of the shell boards: 0 kg.

Additional information about the calculator

Online calculator of the duple (double) roof will help you calculate the angle of the skate, the size and number of rafters, the number of doom, as well as the volume of the necessary materials online. In the calculated base, such common roofing materials such as metal tiles, slate, ondulin, tiles from ceramics, bitumen, cement and other materials are made in advance.

Note! Calculations are made on the basis of SNIP "Load and Impact" and TKP 45-5.05-146-2009, taking into account the standards contained in these documents.

Dux roof (also there are writing "Double roof", "forcep roof") - an option of the roof with two slopes, walking from the skate to the outer walls of the building. Today it is the most common type of roofs, due to the ease of execution, low cost and attractive appearance.

The rafters in the design of such a roof pairly rest on each other and are connected by the shap. The end sides of the structure with such a roof have the shape of a triangle and are called the frontones (sometimes with tongs). Typically, a loft is satisfied with a duplex, and small attic windows are done on the lighting frontions.

Filling the calculator fields, pay attention to the "Additional Information" icon, under which explanations are hidden on each item.

The calculation results are also accompanied by explanations with which you can find below.

Explanations to the results of calculations

The angle of inclination of the roof

This is the name of the angle under which the skate and rafters are tilted to the ceiling plane. Calculations are made taking into account the fact that the construction of a symmetric bone roof is planned. Entering angle, you can not only calculate the desired amount of materials for this angle, but also check whether the roof is possible at this angle from the materials you have chosen. You can reduce or zoom in an angle by changing the width of the base or the height of the lifting: these parameters are toughly interconnected.

Roof surface area

The total area of \u200b\u200bthe roof rods, including the area of \u200b\u200bthe scenes of a given length. Determines the amount of roofing and undercase material required during the construction of the roof.

Approximate weight of roofing material

Supporting the total weight of the roofing material.

The number of rolls of insulating material

The required number of subsecutive material, taking into account the necessary launcher at 10%. In the calculations, we proceed from rolls of 15 meters long and 1 meter width.

Load on the truss system

The maximum possible load taking into account wind and snow loads per rafters.

Length of Stropil

The rafters are measured from the base of the slope to the ridge of the roof.

Number of timelines

The total number of rafters required for the rafting roof system at a given step.

Minimum cross-section of stringel

To ensure the roof sufficient strength, it is necessary to choose the rafters with the options offered here.

Number of rows of dohes

With the parameters you specified, this number of rows of crates will be required. If you need to determine the number of rows for one skate, then this value must be divided into 2.

Uniform distance between the shell boards

To exclude the overrun of materials and save yourself from unnecessary work on the trimming, you need to choose this distance between the shelter boards.

Volume of the shell boards

The number of boards required for the entire roof (in cubic meters).

This article provides a simplified method for calculating the solo system. You will learn how to quickly and correctly decide on the cross section of rafters and the width of the span. Adapted mathematical calculation contains a minimum of formulas and leads to sufficiently accurate results.

There is a standard method for calculating the rafter design, summarized with SNiP 2.01.07-85 "load and exposure". It includes many rather complex counts and reference values. Popular site service - Online Calculation of the rafter system of the bone roof - will allow you to accurately determine the amount of material.

Note. The article discusses the method of calculating the rafter system of the duplex roof with a hollow, semi-wave or fronton without additional structural elements - visors, "birdhouses", towers, etc. and an angle of a row of at least 45 °.

Where to begin

The traditional technique involves the following approach: the design of the roof and the section of the beams is selected. This does not fully meet the requirements of today and the source data in our case will be the following indicators:

1. Requirements (wishes) to roof design. First of all, it is refers to the presence of an attic (residential) floor, the location of the attic windows or the presence of an attic technical room.
2. Existing house sizes or borders of the construction. 70% of private houses are in relatively tight construction, and this is also worth considering when designing a roof. The limited area of \u200b\u200bthe plot and the possible requirements of the neighbors with respect to sunlight can make their own adjustments.
3. Unification. The rafter system is a multi-element design. It is reasonable to try to bring the maximum number of items to one standard - the cross section of the board or timber.

The most difficult, oddly enough, is the first item. However, after a complete idea of \u200b\u200bwhich functions should perform a rafter system (straight or combined), you can start the design stage.

Create a sketch

This stage is one of the decisive, since in it we will learn about the sizes of the elements. The main one - the rafter farm - will be the basis of further calculations. The very drawing is based on two source parameters:

1. Span between carrier walls. It is extremely desirable that the support points of the rafter system, which transmit vertical loads, were located along the axes of the bearing walls or supports. The distance from the projection of the skate to the wall is called semi-trap.
2. Height of the skate from the overlap. This parameter consists of the functional features of the design - the height of the attitude of the attic, an affordable attic or a "deaf" attic space.

As is known, 75% of simple rafter systems are roofs with direct and "broken" skate. This significantly affects the calculations, so we immediately divide these species. Since the basis of any standard roof is a triangular design, we will try to limit ourselves to one formula (Pythagora theorem):

• c 2 \u003d A 2 + B 2

At this stage, it is possible to quite accurately calculate the area of \u200b\u200bthe rods and the flow of roofing material together with the cut. To do this, it is enough to take advantage of the calculation of the slinging system of the bone roof of the online, which is provided by many sites.

Direct equilateral scat

We carry on the sketch of the overlap or the location of the bearing walls (the design does not always imply the presence of wooden overlap) on the scale. Then we celebrate the skate point and carry out straight to the walls taking into account the received roof departure. These direct can already be measured and multiplied by scale - we get the length of the rafter foot.

In accordance with the selected structure of the organization of the internal space (integrated or separated), we have a subcording tightening (beyl) and determine its length. We have in the drawing stops, slopes and vertical racks, observing the requirements that the site portal led in the article "The Slingerous System of the Dusco Roof with your own hands." The spills should not be more than 2 m, and the rafters should necessarily have an intermediate boost. At the same time, it is enough to adhere to the exemplary tolerances.

Applying the formula of the relationship of the parties of the rectangular triangle, you can calculate any of the sizes of the rafter farm. The remaining sizes can be removed from the drawing through the scale. The main task is to get the dimensions of each of the elements.

"Loan" Skat

This type of roof is always taken in connection with the dispute device or the superstructure of the residential floor. It has one characteristic feature - a number of vertical racks at the place of crossing the rods and the substropylene riglel, which can be located both at the level of the top of these racks and under the skate. Rows of racks and riggers form walls and an attic ceiling.

Similarly, we are transferred to the drawing the main elements - first the walls and overlap, then a row of racks and riggers (at the ceiling level), then connect them with lines that will definitely show the shallow shaft form.

After measurements and calculations, the lengths of all elements of the rafter farm should be added and added to the resulting number of 10%. It will be the total length of the design of one farm (CH 1).

Selection of the cross section of rafters and unification

The cross section of the elements of the system, especially the rafter legs, directly depends on the span between the supports in the central part. From all sawn timber for the rafter system, a timber and a board are suitable (not counting factory glued farms). At the same time, the board has a much better indicator of the relationship of the cross section for flexural strength. In our case, we are talking about the reliability of the rafted, for which the board is used, because There is a stock of the sinuses to bookmark the insulation.

Table of dependence of the width of the span and thickness rafters

It is not recommended to arrange rapid farm flaps without intermediate supports.

Council. When splitting two boards to create a vertical support, launch between them in places of attachment of the cutting of the boards of 25 mm ("Bars") with a step of 300-400 mm. So the strength of the support will be higher compared to direct splicing.

After determining a sufficient section of the board, you can calculate the volume of one rafter farm. To do this, multiply the ADC-1 on the cross section area of \u200b\u200bthe board. The resulting volume of one farm (of 1) will be used when calculating the total volume.

Calculation of the step of rafter farms

The step of the attic of the attic rafter system depends on the thickness and construction of the rafter farms.

Table dependency steps from thickness

Dividing the length of the longitudinal (parallel skate) walls on the selected step. We obtain the number of rafting farms (N). Accordingly, we can calculate the length of the farm boards:

• CH 1 x N

farm Board Scope:

• Of 1 x N or ADC 1 x S Single Board X N

Calculation of Maurolat

If the rafter system is arranged on wooden overlap, then the whole horizontal strapping belongs to it. We will look at the option with Mauerlat on a stone wall.

Since the vertical racks, pods and runs are included in the calculation of the farm, we left to calculate the horizontal strapping. There is a simple rule - it should be a thickness of an at least double rafter foot. If the total weight of the roof (along with the cut and roofing material and snow) is significantly high, three layers of the board should be applied.

The volume of the Mauerlat board will be equal to the length of the bearing walls multiplied by the board cross section and on the number of layers. Maurylalat, made of several layers, will better contact the corners.

General counting

We fold all the volumes obtained together and add 20% for waste and trimming. The amount of metal products and fastening elements is determined individually. It is reliably known only to what they are more, the better.

Note. All the above values \u200b\u200band proportions of addiction are taken from regulatory reference.

Despite the seeming simplicity, this adapted calculation can compete exactly with the online calculators of the rafter system. However, the decisive word always remains for those who will execute the project.

Video on the topic

rMNT.ru, Igor Maksimov

The roof is a very important functional element of the house. To ensure the necessary strength of its design, special calculations are produced, including the determination of the amount of sawn timber. This is very important to determine the amount of forthcoming work due to the considerable value of the building material.

How to start computing?

The number of required lumber directly depends on several factors. By producing calculation, it is necessary to consider:

• the area of \u200b\u200bthe roof covered;
• roof type;
• coating material;
• climatic conditions;
• size and section of wooden beams;
• approximate weight of the whole design.

The easiest way to independently calculate the calculation for relatively simple roofs, single and bounced.

Tent, hip or broken roof structures are more complex and requires certain knowledge for the qualitative calculation of the necessary materials. The number of skates in each particular case will depend on the form of the house and personal preferences of the owners. Determining the number of sawn timber largely depends on this indicator. The roof frame is a rafter system.

It must easily withstand strong wind gusts, a significant thickness of snow cover and other impact, keeping the roof itself in working condition. The rafter system is a construction constructed from a bar with different cross-section, boards, logs, other materials and fasteners. The main elements that will be calculated are Mauerlates, rafters, a doomle and a counterclaim. The calculation of the maximum load on 1 m rafter is performed using special tables.

Back to the category

Performing the calculation of the rafter system

The determination of the lumber required for the roof structure is carried out in this order:

1. Mauerlates are laid around the perimeter of a brick house, so in this case it comes down to calculating the perimeter of the building. For Mauerlatov, high-quality logs or a ram of a minimum thickness of 100 mm are used.
2. To calculate the lumber for rafters, it is necessary to determine their length. For example, take a duplex roof of 4 meters high for a home of 8 sizes 10 meters. The rafters are installed across a 10-meter side. Using the Pythagora theorem, make calculations:

• a \u003d √ (B2 + (C / 2) 2), where;
• a - the length of the rafter;
• in - the height of the roof;
• c - width of the building + editions under the eaves of 0.5 m;
• a \u003d √ (42 + (9/2) 2) \u003d 6.02 m.

1. The cross section of the rafter vehicle is calculated by relying on many factors. For simple designs use recommendation tables. For example, at a length of the rafted 6 m and step 0.6 m, their cross section should be at least 50 per 200 mm, with a step 1.1 m - 100 per 200 mm, and with a step of 1.75 m - 100 per 250 mm.
2. Next, determine the total number of timber for rafters. For example, if a timing of 50 per 200 mm is used, then at a roof length of 10 m, 17 pairs of rafter (10 / 0.6 \u003d 16, 66) must be used, which at the length of one rafter foot 6.02 will be:

17 x 2 x 6.02 \u003d 205 m

At step 1.1 m, 9 pairs of BRUSEV are needed, or:

9 x 2 x 6.02 \u003d 109 m

The rafters are the main supporting elements of the design experiencing significant loads, so they should acquire a high-quality lumber from coniferous rocks with a minimum amount of bitch, without cracks.

1. In addition to rafters, there is a calculation of lumber for the counterclaim (in the case of a waterproofing device). It is strengthened on rafters to create a gap between the crate and the waterproofing membrane. For the device, the counterclaims use bars with a thickness of 2-5 cm, the overall method of which corresponds to the total length of the required rafter timber.
2. The amount of lumber for the crate depends on the choice of roofing material. For example, for bitumen tiles or galvanized steel sheets, it is suitable for a solid crate, for polymer and ceramic tiles - frequent, and for metal tile and ondulin - rare. For continuous crates, boards are used, and for a crate with a certain step - a thickness of at least 5 cm. To determine the amount of step should be approached with special attention. Too much distance can lead to roofing deformation, and too small - to the unreasonable increase in the total mass of the structure.
3. In addition to these elements, in the design of the roofs, the racks from a bar 100-150 mm thick for strengthening the design, tightening, fuels, fusion and front boards.

The roof in the building is designed to hold external loads and their redistribution on bearing walls or supporting structures. Such loads include the weight of roofing pie, the mass of the design itself, the weight of the snow cover and so on.

The roof is located on the rapid system. This is the name of the frame design, which the roof is fixed. It takes all external loads, distributing them by supporting facilities.

The rafter system includes the following elements:

• Maurylalat;
• Picpipes and disclosures;
• Side and skate runs;
• Stropile legs.

A rapid farm is a design that includes all the listed elements with the exception of Maurolalat.

Double roof load

Permanent loads

The first view is called such loads that act on the roof always (in any season, time of day and so on). These include the weight of roofing pie and various equipment installed on the roof. For example, the weight of the satellite antenna or aerator. It is necessary to calculate the weight of the entire harrowing design together with fasteners and various elements. Professionals for this task are used by computer programs, as well as special calculators.

The calculation of the two-sheet roof is based on the calculation of loads on the rafting legs. First of all, it is necessary to determine the weight of roofing pie. The task is quite simple, you just need to know the materials used, as well as the size of the roof.

As an example, we calculate the weight of roofing pie with Ondulin material. All values \u200b\u200bare taken approximately, high accuracy is not required here. Usually builders perform the calculations of the weight of the square meter of the roof. And then this indicator is multiplied by the total area of \u200b\u200bthe roof.

Roofing pie consists of ondulin, a layer of waterproofing (in this case - isolation on a polymer-bitumen basis), a layer of thermal insulation (the weight of basalt wool will be calculated) and the crates (the thickness of the boards is 25 mm). We calculate the weight of each element separately, and then lay all values.

Calculation of the roof of a two-sheet roof:

1. The square meter of roofing material weighs 3.5 kg.
2. Square meter of the waterproofing layer weighs 5 kg.
3. Square meter insulation weighs 10 kg.
4. Square meter of the crate weighs 14 kg.

Now we calculate the total weight:

3.5 + 5 + 10 + 14 = 32.5

The resulting value must be multiplied by the correction factor (in this case it is 1.1).

32.5 * 1.1 \u003d 35.75 kg

It turns out that the square meter of roofing cake weighs 35.75 kg. It remains to multiply this parameter on the roof area, then it will be possible to calculate the two-screw roof.

Blood load variables

Changes are called such loads that act on the roof is not constantly, and seasonally. A bright example is snow in winter. Snow masses settled on the roof, creating an additional effect. But in the spring they melt, respectively, the pressure is reduced.

Variable loads belongs to the wind. This is also a weather phenomenon that is not always valid. And there are a lot of such examples. Therefore, it is important to take into account variable loads when calculating the length of the rafted bone roof. When calculating, you need to take into account the many different factors affecting the roof of the building.

Now consider the snow load. When calculating this parameter, you need to use a special card. There is a lot of snow cover in different regions of the country.

To calculate this type of load, the following formula is used:

Where SG is an indicator of the area taken on the map, and μ is a correction coefficient. It depends on the roof slope: the slope is stronger, the smaller the amendment coefficient. And here there is an important nuance - for the roofs with a bias from 60 o it is not taken into account at all. After all, they will simply slide with them, and not to accumulate.

The whole country is divided into areas not only by weight of snow, but also by the strength of the winds. There is a special card on which you can find out this indicator in a certain area.

When calculating the rafted roof wind loads are determined by the following formula:

Where X is the correction coefficient. It depends on the location of the structure and its height. A W O - the parameter selected by the map.

Calculation of the size of the rafter system

When with the calculation of all types of loads is finished, you can proceed to calculate the dimensions of the rafter system. Performing work will differ depending on which roof design is planned.

In this case, two-tie is considered.

Section of a rafter foot

The calculation of this indicator is based on 3 criteria:

• Loads from the previous section;
• Distance peril;
• Length raftered.

There is a special table of cross sections of a rafter foot, in which it is possible to find out this indicator based on the criteria described above.

Length of rafted in a double roof

When calculating manually, the basic knowledge of geometry, in particular, the Pythagoreo theorems. Slinge - hypotenuse of a rectangular triangle. Its length will get to know if it is divided by the length of the catech on the cosine of the opposite angle.

Consider a specific example:

The calculation of the length of the rafted two-tie roof for a house with a width of 6 m is required, in which the slope slope is 45 o. Let L be a long rafted. Substitute all the data in the formula.

L \u003d 6/2 / COS 45 ≈ 6/2 / 0.707 ≈ 4.24 meters.

You need to add a visor length to the resulting value. It is approximately 0.5 m.

4.24 + 0.5 \u003d 4.74 meters.

On this, the calculus of the length of the rafted for a two-tie roof is over. It was a manual way to perform a task. There are special computer programs designed to automate this process. The easiest to use "Arkon". This is a fully free program that is easy to understand even well-disassemblers in computers.

It is enough just to specify the introductory parameters based on the size of the house. The program will independently fulfill the calculations and show the desired section, as well as the length of the rafted bone roof.

How to calculate the length of the rafted two-tie roof: the calculation of the roof, load and design rules

Calculate the length of the rafters and the row of a bone roof

When designing a private house, it is necessary to take into account many different parameters. If you calculate them incorrectly, the strength of the structure will be under great doubt. The same applies to the roof of the house. Here, before the start of construction, it is necessary to find out the height of the skate, and the roof area and much more, including the length of the rafter. And about how to make the last calculations and will be discussed in this article.

What type of roof

How to calculate the length of the rafted? This question will interest everyone who independently builds the house. But to answer it, it is necessary to figure out the many other parameters. First of all, it is worth deciding with the type of roof, because it will be from this that the length of the skate and rafters will depend on. The most common option is the two-tie design. But here there are several options, namely:

You can consider even more complex structures, such as multi-level. Such roofs will look very attractive. But to make the calculation, but especially the rafter system, in this case, it will be almost impossible without the help of professionals. Therefore, in most cases, three, the above-mentioned variants of the bone roof are limited.

System type

The calculation of the length of the rafted double roof will also depend on the system used. Here specialists allocate the following two main varieties:

1. Hanging system. This is the easiest option. In this case, the rafting legs rests only in Maulelat. The upper part of them is simply connected to each other. Such a system is used if the house width is small. At the same time, the length of the rafter should not exceed six meters. The suspension is undesirable to use with an asymmetric duplex roof.
2. The urban system is a stronger rafter system. It is used if the axial carrier wall is used in the middle of the house. In this case, the supports and the ski run are installed, on which the upper part of the rafter feet is attached.

You can use the combined option. It is often used when erecting houses with complex geometry. Here, calculate the length of the rafter and other system parameters will be more difficult. If you exactly have this option, it is better to trust everything to calculate the specialist. In this case, there will be less errors, which means the roof will last longer and will not give you problems during operation.

What else to take into account

The roof type and system used is not all parameters that will be required to calculate the length of the rafted two-tie roof. Before computing, you need to learn more of information, namely:

In addition, making the calculation of the length of the rafters, you should find out which skes should be. Without this "additional" element, not one roof does not cost. Sails play the role of protection that protects the walls of the house and its foundation from the blur by water flowing down from the roof.

They can be a continuation of rafters or are made as independent elements. In the latter case, boards wearing the name "Film" are attached to the main design. In essence, they are lengthening rafters.

What length to choose skes is to solve the owners yourself at home. According to existing construction standards, this parameter must be between 50 to 60 centimeters. It is not necessary to do less, otherwise walls and foundation may suffer. Sometimes the sinks make more than one meter. In this case, a small canopy is obtained along the wall, which can be used to relax or storing things.

Making calculations

And how is the length of the rafter calculated? If the roof has a symmetrical form, then it is not difficult to calculate this parameter. For this, the formula of the Pythagora theorem is used, namely: equals the root square from a in square plus in square, where:

• C is the desired length of the rafted;
• And is the height on which the horse is located (from the root base);
• B is half the width of the house.

At the same time, with the help of this formula, it is possible to calculate Dina rafters only to Mauerlat. The length of the soles is not taken into account. If they are a continuation of the rafter, then the calculated parameter must be added to their length.

And how to make a calculation if the roof is asymmetric? In this case, the rods will be different. But here you can use the Pythagora theorem. You can calculate the roof rafters in the same formula, only first to figure out the value of the "B" parameter (in the first case it is equal to half the width of the house). If the roof is asymmetric, then at the stage of its design, you calculate, at what distance from the walls will be located. It is this value and is taken as the "B" parameter. As a result of the calculation, you will receive the length of each of the rafting legs (on the left and right-wing skate). As you can see and there are no problems with calculations.

There is another way to calculate rafters. In this case, the angle of inclination is used. This formula is a bit more complicated by the previous one. The length of the rafter (for a two-tie symmetric roof) will be equal to the amount of 0.5 and height from the roof base to the skate divided by the causing angle of the slope.

No matter how much the calculation would be made, the main thing is to make it correctly and accurately. From this will depend on the strength of the entire rafter system. If you calculate the length of the rafter to an integer, it does not work, it is better to make rounding to the biggest side. It is better to sprinkle a bit too much when installing the montage itself.

The calculation of the length of the dual-tie roof lines depending on the type of roof (symmetric, asymmetric, broken) and the type of the rafter system (hanging, urban). Main nuances and calculations.

The roof is not only the protection of the house from the external environment, but also a certain decor element that gives the construction a finished view. That is why the developers are being built today the most unusual roofs with complex structures of rafter systems.

The system of rafters is an essential element of the arrangement of any roof. It accounts for the weight of coating and precipitation. Therefore, the correct implementation of such a system, taking into account all the rules of construction art, is a guarantee of the reliability and durability of the roof. It is very important to correctly determine the length of the rafted and other structural elements. At the same time, such climatic features should be taken into account as:

What is the system of rafters

Any design of this kind is performed as interconnected elements, strictly corresponding to the calculations produced earlier. The following elements can be distinguished as part of this system:

• sound legs that are still called rapid;
• stops, shpregels and other fasteners that give the design necessary hardness;
• vertical type racks;
• netigaries.

Note! It is necessary to take much responsibility to calculate the length of the rafted - any, albeit a minor error can lead to the deformation of the geometry of the roof and, accordingly, its collapse.

If you do not understand the features of the roofing structure, then it is better to refer to a qualified person specialists. For self-calculation, you use special calculators and tables - it will help you avoid errors.

Varieties of the rafter system

Varieties of the rafter system

Slinge systems are divided into two groups depending on the material used:

• wooden structures;
• metal designs.

There are still railway rafting systems, but they are used mainly in industrial buildings. In any case, be raftered with metal, wooden or concrete, they must be firmly attached to the walls of the house.

Often for the construction of rafters in country houses use wood, mainly coniferous rocks. Compared to the metal, the tree is easier to handle and install. Moreover, even if an error occurred during the calculations, the wooden parts are easy to replace.

Before proceeding with the calculations, first measure the width of the house. The fact is that although small contact legs do not need additional buildings, but in some cases the special geometry of the roof requires a strengthening of the rafted, even if the house is minor sizes.

According to the features of the construction of the rafter are divided into:

In the construction of country houses, inclined rafters are often used, but often builders are combined and those and others. As already mentioned, it may be necessary to extend the offended feet. It depends on the roofing material used in construction. So, slate or ceramic tile due to the high weight can only be installed on the rapid system of increased strength.

Types of two-sheet rafal systems

The cross-section of the boards used in the construction of the rafter may be 20x6 cm or 15x5 cm. But if the design is enhanced, you can choose a bar with b about To the cross section (there is another way of amplification - by splicing the boards).

And now - directly to the calculations.

What you need to consider when calculating rafters

First we define the fundamental moments.

1. The view and shape of the roof directly affect the functional features of the rafter system. The fact is that calculations for the tent and double roofs will differ among themselves, because they need to be carried out by different methods. Moreover, the asymmetrical roofs (for example, broken) need additional stabilization elements - riglias, spit, pins and so on.
2. Very important in calculations and future loads on the design, mainly snow and winds. For example, in the snowy regions of the country it is rather difficult to build a roof with a row of less than 45 °, and if you increase the tilt or the height of the structure, the wind load will increase. In a word, you need to define the very "golden middle", but not to the detriment of attractiveness and. Very often, only true masters can solve such a problem.
3. Another important point when calculating is the coating material. Many of these materials need certain conditions. Thus, the flexible tile is stacked exclusively on a solid surface (as a last resort - frequent crate). Ceramic tile needs an enhanced frame.
4. Size and area - these are the main indicators affecting the choice of one or another type of roof. If the area is large, then the step of the rafter and, accordingly, the distance between them is increasing. Because of this, the cross section of the used bar is increasing.

Note! The distance between the bearing walls is called a run. With increasing run, the number of changes in the design is growing, in particular, the number of stabilizing and reinforcing elements.

How to calculate the roof rafters

Now, having familiarized with the starting points, you can take paper, line and pencil and proceed to calculations.

First stage. Weight of roofing pie

First, determine how much the roof itself will be messenger. It is very important, because the rafter system should withstand this weight long enough. It is very easy to calculate: learn the weight of the square meter of each of the layers, summarize the data obtained and add a correction 10%.

Here is an example of such calculations.

1. Square meter of the crate weighs 15 kg.
2. It will be roofing, say, ondulin with a weight of 3.5 kg.
3. Meter square bitumen waterproofing weighs another 6 kg.
4. The weight of the 10-centimeter on the mineral wool layer is approximately 10 kg per square meter.

Let's see what happens.

We add correction 10%, it turns out 37.95 kg. It is this figure that is an indicator of the weight of the roofing cake.

Note! In most cases, this weight does not exceed 50 kg, but experienced professionals are confident that when calculating it is necessary to be based on this value - "to the stock".

It turns out that the weight of the roofing cake should be 50 + 10% \u003d 55 kg / m².

It is very important to take into account the snow load, because the snow can accumulate on the roof in a sufficiently large quantity. Use to determine this load a special formula:

S. In this case, this is the load of the snow that you need to calculate;

µ - amendment, depending on the tilt of the skate;

In a flat roof, the slope of which does not exceed 25 °, the correction will be equal to one; If the slope slope is more than 25 °, but does not exceed 60 °, then the correction will be 0.7. If a very cool roof is constructed, then snow loads for it can not be calculated at all.

S ᶢ - This is the weight of the square meter of snow cover. This indicator depends on the climatic features of a particular region, it is possible to learn about it in Snip.

Suppose the roof slope will be 25 °, and the snow mass is 200 kgf / m².

To calculate the wind load on the rafter, use the formula below.

Wᵒ. In this case, it is a regulatory indicator that you must define on the table (it all depends on which region you live);

TO - This is an amendment that takes into account the height of the house and the type of terrain.

Fourth stage. Calculation of the step and the length of the rafted

Selecting the section and the length of the rafter

To calculate the length of the rafter, you can recall the geometry at school, namely the famous Pythagore's theorem. After all, the rafter design is, in fact, the rectangular triangle and measuring its diagonal is very simple. But do not forget to consider in the calculations:

• the strength of BRUSEV;
• the possibility of deformation - what load will be able to withstand the system without breaking.

Note! As GOST says, rafters should not be fed more than 1/250 part of its length. For example, if the length of the rafter is 5m, then multiply this number about 0.004 - so you will receive a limit of deflection, namely 2 cm.

Basic requirements for material

According to GOST, wood must comply with the following requirements:

• her humidity should not exceed 18%;
• the number of bitch should not exceed three pieces on the straight meter of the bar;
• non-separated cracks can be, but their length should not exceed half of the total length;
• wood should be treated with antiseptic, flame retardant and biological protection.

In addition, when buying Bruusyev, pay attention to:

• firm-manufacture la;
• date of manufacture;
• product name, standard;
• the quality of the execution of individual parts;
• sizes and humidity of products;
• tree breed.

Special computer programs

Apparently what has been said above, for calculations, the rafter needs to be possessing not only a sufficient margin of knowledge, but also the skills of drawing and drawing. Of course, not each of us can brag all this.

Fortunately, today there are many computer utilities designed to facilitate the calculations. There are professional, such, for example, as "autocades", but you can find simpler options. So, in the Arcon program, you can easily create various projects, and also clearly see how the future roof will look like.

Note! In such utilities there are a calculated calculator referred to. With it, it is possible to calculate the length, step and section of the rafted with the utmost accuracy.

There are such calculators in the online mode, but all the data that can be obtained with their help is advisory and will not replace the full preparation of the project.

As a conclusion

One of the most important stages of the roof structures is the calculation of the rafter system. Of course, this business is better to entrust professionals, but the preliminary measurements can be made on their own - it will help you to figure out the finished drawing.

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Learn how to calculate rafters on the roof! What data are needed for calculations, step-by-step guide, tables, photos + video.