Accurate calculation of the height of a gable roof. How to calculate roof height? Calculation procedure, instructions and recommendations Calculation of the height of the roof of the house

When constructing any building, one of the most significant moments is the correct calculation of the height of the roof ridge, as well as its area. With a low ridge height, the roof can collect a large number of snow, which will create an additional load on the entire structure. On the other hand, with a sufficiently high ridge and a large coverage area, the windage of the roof increases, which can become a problem in strong winds. Therefore, it is important to know how to calculate the height of the roof ridge, preventing its premature destruction.

Roof design features

When designing any building, it is important to correctly calculate the parameters of the roof. Here, all possible loads must be taken into account, as well as required amount roofing materials. In this case, one of the main parameters will be the correct slope of the slopes of the structure. In typical gable roofs, the slopes usually have a slope of 12–45 degrees. The direct dependence of this angle of inclination on the loads created by the weight of the roof on the entire roof structure of the building is known.

Note! It is necessary to make additional strengthening of the truss system, which will entail additional construction costs. If you reduce the slope of the slopes, then there will be an increase in the load on all structural elements due to precipitation.

It is equally important to correctly calculate the rafter system. This is caused by the transfer of the total load from rafter legs to the load-bearing walls of the building. In turn, the rafter legs are determined by the size of their section and length. Such structural elements are selected based on what acting loads are on the roof, taking into account the angle of the slopes. To ensure the necessary margin of safety, experts recommend slightly increasing the results of calculating the thickness of the rafter legs.

Since the roof configuration may be different, the calculation of the necessary parameters will be made depending on some features. To correctly calculate the height of the roof, you should always take into account the number of slopes and its shape. Neglecting these characteristics will lead to errors in the calculations. Without such data, it will be impossible to determine the roof area, as well as calculate the required amount of materials for roofing. The height of the ridge affects the length and configuration of the rafters.

main parameters

Constructing own house, each owner will definitely be faced with the calculation of the height of the roof level. Before determining such a parameter, it is necessary to take into account the following nuances:

• the number of slopes;
• the presence of a residential attic or attic;
• the angle of inclination of the slopes, taking into account possible precipitation;
• selected roofing material.

In this case, one should take into account the simple dependence of the amount of precipitation and the angle of inclination of the slopes. The amount of material needed for roofing can be determined by first calculating the height of the roof. In practice, a slope of 45 degrees implies an increase in the cost of the roof by 1.5 times compared to the design of a flat slope.

It is believed that regulatory requirements to the building determine the proportions and height of the roof ridge. Meanwhile, such a parameter can be calculated, knowing the actual dimensions of the walls of the structure. In this case, the calculation of the height of the ridge can be determined using the simplest geometric formulas. To do this, you need to know the width of the structure, as well as the angle that determines the slope of the roof slopes.

Calculations

Parameters such as the height of the roof ridge and the angle of inclination of its slope are directly related. In addition, the selected roofing material also affects the angle of the roof. For example, soft tiles can be laid on a roof that has a slope of 11–90 degrees. Ceramic tiles requires a slope limit of 60 degrees.

It is also necessary to take into account the aesthetic component, therefore, it is necessary to provide for the correspondence of the height of the roof ridge to the height of the building. The fact is that an excessively flat or too high roof can adversely affect appearance structures. Given the available climatic conditions, most the best option It is customary to consider the angle of inclination of the roof, which is 35–45 degrees. Roof with more flat design, will be subject to increased loads due to precipitation.

If we take the height of the ridge as one of the legs of a right triangle, then the other leg will be half the width of the building. Accordingly, the length of the slope will be considered the hypotenuse. In accordance with the trigonometric formula, the length of the leg in such a triangle will be equal to the length of the second leg, multiplied by the value of the tangent of the angle at the base. For example, let's take a building width of 6 m with a roof slope angle of 40 degrees. Turning to trigonometric table Bradis, we determine the tangent of an angle of 40 degrees. It will be equal to 0.83. It turns out that half the width of the house - 3 meters must be multiplied by 0.83. As a result, we obtain the height of the roof ridge of such a building, which will be 2.49 m.

Aesthetic indicators, architectural specifics and specifications Houses. It is extremely important when developing a project to correctly determine the correct size of the structure.

To get the perfect result, we invite you today to figure out how to calculate the height of the skate gable roof, and which method is better to use in independent calculations.

A ridge is called a horizontal edge of a gable roof, formed at the junction of the vertices of its inclined planes. Without the slightest doubt, we will attribute the height of the ridge to the most significant parameters that set the proportions of the roof.

Both underestimation and overestimation of it can lead not only to a violation of the architectural picture, but also to problems in operation. The ardent desire of the owner of the house to realize own ideas often runs counter to technical regulations, familiarization with which will help to avoid serious errors.

In order to make the process of studying the value under study easier and more understandable, let's imagine the future roof in the form of an equilateral triangle. This is the most common option. In addition to it, there are asymmetrical gable roofs with slopes that differ in area.

However, the angle of inclination of both structural components is most often equal, therefore the height of the ridge is calculated according to the standard scheme.

For convenience, we divide an equilateral triangle into two symmetrical parts. The line passing from the top of the triangle to its base is the axis of symmetry of the figure presented by us, it is also the leg of the right triangle and the height of the ridge.

Landmark #1: Atmospheric Phenomena

There is no point in arguing with climate reality, it is necessary to adapt to its inexorable dictation and adapt. Atmospheric phenomena that affect the choice of ridge height include:

The indicated characteristics will be prompted by the local meteorological service. You can independently find them in the collection with rules and tables on building climatology SNiP 23-01-99 or according to the zoning maps given in SP 20.13330.2011.

Landmark number 2: The presence of an attic

In the gable roof family, there are attic and non-attic representatives. In the first case, the attic space is separated from the box of the house. ceiling. They are also called "separate", which confirms the architectural independence of the premises between the roof structure and the ceiling.

Attic representatives are residential and non-residential. The height of the ridge of residential roofs is set by ease of movement. Structures with an operated attic are built mainly according to, involving the construction of a truss system of two tiers.

Skate Height Operated attic roof consists of two values: the height of the lower part of the roof and the height of the top of the roof, erected on the lower tier. The height dimension of the lower tier is usually taken from 2.0 to 2.3 m.

It is calculated by adding the growth of the tallest of the future owners and a margin of 30 - 40 cm, necessary for the convenience and safety of movement. Top size broken roof arbitrary, depending on the taste preferences of the owners.

The height of the ridge of non-residential attics is determined by fire regulations. In addition, the size of the attic space should not create obstacles for Maintenance. The building code regulations indicate that in the attic there should be a through passage along the entire roof of at least 1.6 m in height and 1.2 m in length. In short sections of a composite structure, the width and height of the through passage can be reduced by 40 cm in both directions.

In the second "non-attic" case, the space under the roof is not separated from the box by a ceiling. It is usually located below: at the level ceiling system the previous floor. Non-attic roofs are called "combined", which just indicates the connection of the space under the roof with part of the space of the foot.

Bright representatives of structures without an attic belong to. They are raised in the usual way. gable scheme, but the Mauerlat is laid on walls with a height of at least 1.4 m. The height of the ridge of the half attic is measured from the lower edge of the Mauerlat.

The practicality of building a semi-mansard roof in regions with high wind load is difficult to overestimate. Thanks to its construction, the minimum lateral load acts on the roof, and the owners receive a comfortable and very spacious additional floor.

no attic and attic floor construct low, small household buildings, warehouses. Covering in such situations is neither economical nor reasonable in terms of access for maintenance.

Landmark #3: Type of roofing

We have already represented the gable roof as an equilateral triangle. And the height of the skate was represented by the leg of its rectangular counterpart, obtained by dividing the structure into two symmetrical parts. In our created geometric figure all components are interconnected, including angles and side lengths.

We, as roof designers, are interested in the angle of its slope, because. it is directly dependent on the type and technical characteristics roofing. It will help to determine the optimal height of the designed structure.

There are several selection rules. roofing material taking into account the height of the ridge and the steepness of the roof, this is:

• The smaller the piece elements of the roof, the greater must be the angle of inclination of the pitched planes. Numerous joints of piece coatings create the prerequisites for the penetration of moisture under the roof, so it is necessary to accelerate the precipitation.
• The lower the roof, the fewer joints and seams should be on the floor. The priority for the arrangement of large-sheet and roll roofs.
• The heavier the coating, the steeper the roof should be built. The weight of massive elements will be distributed in projection per unit area of ​​the base. As a result, the higher the ridge, the less the load puts pressure on the rafter system and the ceiling.

True, the arrangement of a steep roof with a high ridge will cost more. The construction of a structure with a slope of 45º will take 1.5 times more material than covering a flat roof with a steepness of up to 7 - 10º. And if the slopes are tilted at an angle of 60º, the costs will double.

Typically, the range of suitable angles of inclination is indicated by roofing manufacturers in the instructions. The recommendations of the manufacturers should be followed in the name of the long-term service of the structure.

Knowing the recommended angle of inclination, the width of the cornice overhangs and the dimensions of the house box, it is possible to find the height of the ridge in the course of simple geometric constructions. However, in the design of roofs, not only the graphic method is used.

The slope of the slopes is indicated by degrees, percentages or decimal, in the numerator of which the height of the ridge is indicated, in the denominator - half of the overlapped span. All three slope expressions are interrelated, but on a construction site it is more convenient to use the latter option.

There are few who want to postpone the angle of inclination of the ramp with a construction protractor at the facility. Moreover, the process of installing layered rafters, for example, is carried out on an already installed ridge run. Those. you need to know the height of the ridge run ahead of time. This is another one of the good reasons that stimulates interest in calculating the height of the skate.

To the percentage expression of the slope of the roof, there was a general attitude both among the masters and among the home craftsmen. Percentages will only help to confuse. The most acceptable method of displaying the slope is the ratio of the height of the ridge to half the span to be covered. It is most often used on the construction site.

Knowing the height of the ridge, you can not peep every minute in the project documentation. Simply by measuring, the middle of the gable wall is determined. At the point obtained, a bar or pole is nailed strictly vertically. From the upper face of the Mauerlat pre-installed on the wall, the size we are studying is laid upwards. It is guided by the construction of the truss system.

Ways to determine the height of the ridge

To calculate the height of the ridge of a gable roof, the area of ​​\u200b\u200bplanes and other dimensions of the designed structure, there are a significant number of calculator programs on the network. All calculations are carried out automatically, the speed and simplicity of the procedure pleases. True, it is difficult to check the results of the calculations without a visual representation of the planned roof configuration. And if you accidentally enter an erroneous number, it will be possible to detect “amazing” sizes only at the construction site. Therefore, it is better to understand the features of construction and calculations in advance so that a banal flaw does not cause super-high costs.

Independent designers will need memories of a school trigonometry course and a desire to build diagrams to scale using a monitor or a regular paper sheet.

Mathematical and graphic methods

To determine the height of the ridge of the roof structure, the following methods are used:

• Mathematical. It consists in calculating the size according to the formula for calculating the length of one of the sides of a right triangle.
• Graphic. It consists in building a roof scheme on a scale to obtain the height of the ridge.

For the production of mathematical calculations, the formula a \u003d b × tgα is used, where a is the desired height of the ridge; b - half the width of the span; tgα is the slope angle chosen by the owner of the house on the basis of technical regulations and recommendations from the roofing manufacturer.

Graphically the height of the ridge is determined at the intersection of the axis of symmetry of the roof and the line of the slope, plotted at a given angle from the extreme point eaves overhang. Let's take a look at one of the obvious examples. graphic construction to get an idea of ​​the process.

Let's note an important nuance. The described methods calculate the rise of the roof, and not the total height of the ridge. The real value depends on the technology of fastening the top of the rafters. In hanging systems, the height of the ridge remains unchanged. Similarly, in layered versions, if the top of the rafter does not protrude above the line of the ridge run.

If the tops of the rafter legs rise above the run, then 2/3 of the thickness of the board or timber used in the construction of the rafter system should be added to the roof rise. It is believed that the depth of the cut reduces the thickness of the material by a third.

The crate built over the rafters and the thickness of the roofing are usually neglected in the calculations. It is practically impossible to avoid slight deviations during the construction of the roof, in fact, 5-7 cm of the roof with the crate have almost no effect on anything.

Practical Calculation Example

Let us analyze the procedure for calculating the height of the ridge using a specific example. This is how North American carpenters specializing in the construction of low-rise frame houses calculate the dimensions of a gable roof. Fundamentally, the process is no different from the actions of masters in other countries.

In the example, there is a purely technological specificity: the attachment point of the lower heels of the rafter legs to the base is attached with a notch. The rafters rest on a ridge board. If this is not taken into account when drawing up the diagram and performing calculations, the slope will change, which is highly undesirable when choosing the limit value of the slope angle recommended by the coating manufacturer.

At the heart of independent constructions is the same equilateral triangle, divided into two symmetrical halves. We know the width of the span of the house box and the angle of inclination, because it is selected in accordance with the type of roofing.

The algorithm for calculating the height of the ridge is reduced to a number of the following actions:

• Let's build a scaled diagram and put on it the exact dimensions of the equipped box. The most convenient and understandable scale is 1: 100, according to which 1 cm displays on a scale of 1 m. If working with such a decrease is uncomfortable, you can choose a smaller or larger scale.
• Let's find the middle of the span and draw an axis of symmetry of the roof from the obtained point upwards.
• From the corner of the box, we set aside with a protractor the angle of the slope of the projected roof. We draw a slope line according to the marked angle.
• The intersection of the axis of symmetry of the roof and the line of the slope of the slopes, i.e. diagonal, will give us the opportunity to estimate at what height the board of the ridge run will be located.
• We outline schematically the outline of the ridge run and the support post on which the run will be laid. Their axis of symmetry must coincide with the axis of symmetry of the roof. You just need to set aside half the thickness of the ridge board on both sides of the axis and draw arbitrary lines.
• The line of the base of the triangle, the diagonal and the nearby side face of the ridge run, together with the rack, determine the desired triangle, the vertical leg of which is the rise of the roof.
• We reduce the rise by 1/3 of the thickness of the board, i.e. to the depth of the cut of the lower node of the rafters.
• From the resulting height, we set aside the width of the ridge board and draw the ridge run, then the ridge rack.
• On a scale, we draw the rafter leg, not forgetting that it will sink 1/3 of the width due to the cut. To simplify work, we draw a straight line parallel to the diagonal at a distance of 2/3 of the thickness of the rafter board.

Simply put, the height of the ridge is the sum of the rise of the roof and 2/3 of the thickness of the rafter board. In practice, there will still be no impeccable accuracy, but the error can be considered insignificant and quite acceptable according to construction standards wooden structures prescribed in the collection SP 64.13330.2011. Ideally, the processes of compression and crushing should be taken into account wooden parts systems.

Video example of a skate device

The video will acquaint you with the option of building a gable roof ridge, similar to the design described in the example:

A well-designed roof with a properly calculated ridge height will look great. Its components will not create conditions for leakage and premature wear of the structure. It is not difficult to master the calculation methods proposed by us.

Roofing is one of essential elements construction of a private house, as it prevents the penetration of precipitation, melt water and cold air masses into the premises. If you know how to correctly calculate the height of the roof and ridge, its device will allow gravity to remove moisture from the roof surface without increasing the load on the rafter system.

The need to calculate the height of the roof

The house will look harmonious, provided that the appearance of the roof complements it. architectural design. To do this, you need to correctly calculate the height of the roof in relation to the width of the house. Let's look at how roof height is calculated, what are the nuances in the calculations.

In accordance with the accepted terminology, the height of the ridge is the distance between the middle of the base of the roof structure and its highest point.

The following characteristics depend on the value of this parameter:

1. The slope angle. The greater the height of the hipped roof ridge, the steeper the slope of the roof of the house turns out. In regions where there is a large amount of snow in winter or heavy rains often occur during the year, the angle of inclination of the slopes should be 20 - 50 degrees.
2. roof surface area. The higher the roof, the larger the area of ​​\u200b\u200bthe slopes, which means that the cost of installation increases. It's connected with big amount building materials required for the construction of the truss system.
3. Load bearing capacity roof frame. With an increase in height, the weight of the structure increases, as does the load from the layers of the "pie". For this reason, there is a need to strengthen the frame by installing additional elements.

There are 2 methods for finding out the height of the roof:

• calculate the desired value depending on the size of the desired slope;
• first decide on this parameter, and then only calculate what the slope of the slopes should be.

Selecting the height of the structure

When designing, it is necessary to know the height of the roof, since this value has a significant impact on its performance.

Possession of information on how to determine the height of the roof of a house will help to calculate and create its project, which will meet the climate of the region and the purpose of the building. As a result, the roof will last much longer and require less maintenance.

When designing a roof structure, consider the following:

1. Average annual rainfall. The higher this indicator, the higher the skate should be made.
2. wind load. On the ground with strong winds usually build low-rise buildings with a sloping low roof.
3. The purpose of the building. If the project of the house provides for the arrangement of a residential attic space, then the height of the ridge must be made at least 2.5 meters.

How to correctly calculate and determine the height of the roof, in relation to the width of the house

The technique for calculating the height of the roof and ridge is simple. When carrying out calculations, it is generally accepted that the vertical section of the roof is an isosceles triangle, in which the base is equal to the width of the pediment. In this case, mathematical formulas are used.

1. The width of the structure is divided by 2.
2. To determine the slope, you need to choose the angle between the base and the surface of the roof slope.
3. Further, according to the Bradis table, the tangent of this angle is determined.
4. Multiply half of the width value by the tangent of the angle and get the height of the ridge.

Usually this parameter is chosen so that the slope of the roof is 25-45 degrees.

The gable roof is the most popular roofing structure, which is equipped with private residential buildings, baths, garages and other buildings. The construction of a roof of this type - rational solution protection issue interior spaces from the penetration of precipitation, wind and cold. In the process of designing a gable roof, the calculation of the height of the ridge, the determination of the slope and the area of ​​\u200b\u200bthe slopes take center stage. The service life and efficiency of the overlap depend on these three parameters, so in this article we will tell you how to independently calculate the main parameters and technical characteristics of the roof without using a calculator program.

They call it a skate highest point gable roof, a horizontal rib, which is located at the junction of the planes of the slopes. It is mounted on final stage roofing works, but before installing the crate on the rafter legs. Skate length gable roof corresponds to the length of the slope. This element of the truss frame solves the following tasks:

1. The main function of the ridge is to be a support for the upper part of the roof rafters. It connects all pairs of rafters together, giving rigidity to the structure, evenly distributing the weight of the roofing material of the gable roof.
2. Ensuring air circulation. Air gap, formed in the place of the equipment of the ridge protects truss frame from air stagnation and decay, provides ventilation for all wooden elements, due to which the service life of a gable roof is increased.

Important! In the process of designing the roof, you need to choose and correctly calculate the height of the ridge. If the room located under the roof vault is used as a residential area, then the choice is made based on the desired ceiling height, in other cases, the calculation is performed based on the recommended angle of inclination of the slopes.

The easiest way to make calculations is using a special calculator program, by entering the initial data into which you can determine the height of the ridge, the area of ​​\u200b\u200bthe slopes and the roof space.

Methods for calculating the height and area of ​​\u200b\u200bthe roof

You can calculate the height of the ridge and the area of ​​\u200b\u200bthe gable roof and other related parameters without using the calculator program. This requires knowledge of elementary geometric formulas, which, we hope, you have not forgotten since your school days. You can independently calculate the skate by two simple methods:

Important! The most reliable way to calculate the height of the ridge and the area of ​​\u200b\u200bthe slope is a special online calculator. To use it, you need to enter the initial data: the length and width of the house, the slope of the slope.

Roof Height Determination

The most important factors influencing the choice of the height of the ridge connection relate to natural conditions the area in which the construction is taking place. According to building codes, this parameter is selected based on the following conditions:

Note! The height of the ridge connection affects the useful area of ​​​​the attic room. To equip living room under the roof, the roof should be raised to a height of at least 2.5 m, however, this will negatively affect usable area because of the low sidewalls.

Video instruction

The gable roof has long been a classic of architecture. The list of its advantages includes ease of installation, low maintenance costs and practicality in terms of the natural removal of rainwater and snow. In order to fully experience these advantages, it is necessary to correctly think over the roof project and calculate the dimensions. This is the only way to make the structure durable and maintain an attractive appearance for many years.

The main parameters of the gable roof

Selection optimal size Roofs are a complex process of finding a compromise between the desired appearance of a building and its safety requirements. In a properly designed roof, all proportions are close to ideal. The main parameters of a gable roof include the angle of inclination, the height of the ridge, the width of the roof and its overhangs.

The slope of the roof is a value that determines the position of the slope relative to the horizon. The choice of this indicator is carried out at the design stage of the structure. Traditionally, both slopes of a gable roof are made with the same angles of inclination, but there are also asymmetric varieties.

Most often there are roofs with a slope of 20 ° to 45 °

The unit of measure for slope is degrees. For roofs, the range 1 0 -45 0 is accepted. The larger the number, the sharper the structure, and vice versa, as the degree decreases, the roof becomes sloping.
Depending on the slope, several types of roofs are distinguished:

• flat (less than 5 °), the advantages of which are low consumption of materials and ease of maintenance, and the disadvantages are the mandatory presence of a good waterproofing system and measures to prevent snow accumulation;
• gently sloping (up to 30°), allowing the use of all existing materials, but more expensive in cost than flat;
• steep (more than 30°), capable of self-cleaning, but not resistant to wind loading.

An inclinometer is used to measure the slope angle. Modern models equipped with an electronic scoreboard and bubble level. When the device is oriented horizontally, "0" is displayed on the scale.

Manufacturers offer to purchase inclinometers with laser sensors that allow measurements to be taken at a distance from the object

Photo gallery: roofs with different slope values

The load on a roof with a slope of 45° is 5 times higher than on a roof with an angle of 11°
Steep slopes, due to the large slope of the slope, drain precipitation well
A multi-slope roof is erected if necessary to connect walls of different heights or a neighboring extension to the house
Minimum Angle slope recommended by builders, 14°

In a number of regulatory documents, for example, SNiP II-26-76 "Roofs", the slope is indicated as a percentage. There are no strict recommendations for a single parameter designation. But the percentage value is very different from the variant in degrees. So, 10 equals 1.7%, and 300 equals 57.7%. For error-free and quick conversion of one unit of measure to another, special tables have been created.

Table: relationship between slope units

Skate height

Another important parameter of the roof is the height of the ridge. The ridge is the top point of the truss system, located at the intersection of the planes of the slopes. It serves as a support for the rafters, giving the roof the necessary rigidity, and allows you to evenly distribute the load on the entire structure. Structurally, it is a horizontal rib made of wooden beam. If we imagine a gable roof in the form of a triangle, then the height of the ridge is the distance from the base to the top of the figure.

According to the rules of geometry, the height of the ridge is equal to the length of the leg of a right triangle

Total roof width and overhang width

The total width of the roof is determined by the width of its box (the size of the truss system) and the width of the eaves.

The overhang is the part of the roof that protrudes beyond the walls. The overhang width is the distance from the intersection bearing wall from the roof to the bottom of the roof sheet. Despite the modest dimensions and a small specific percentage in total area, the overhang plays a key role in the operation of the house. The cornice protects the outer walls from atmospheric precipitation, keeping their covering in its original form. It creates a shadow in adjoining territory in the summer heat and shelters people during a snowfall. In addition, the overhang facilitates the drainage of rainwater from the roof.

The required size of the cornice overhang B is obtained by lengthening or building up the rafter legs

There are 2 types of overhangs, differing in location and width:

• pediment - a small section of the roof slope, located on the side of the pediment;
• eaves - a wider overhang that is along the roof.

To protect the lower surface, the overhang is sheathed edged board, siding or soffits

Photo gallery: roofs with different widths of overhangs

Optimal Width cornice is within 50–60 cm
The edge of the roof ends at the top line of the gable or wall
Houses built in mediterranean style, have narrow overhangs and a small slope angle
A wide cornice gives monumentality to the entire building

Factors affecting roof parameters

The first stage of roof construction is the development and preparation of a technical plan. It is necessary to take into account all the nuances that will affect the life of the roof. The design parameters are determined by considering a group of factors: the climatic features of the region, the presence of an attic and the type of roofing material.

Depending on the area in which the building is located, it can be influenced by various natural forces and loads. Among them - wind, snow pressure and the impact of water. You can determine their value by contacting a special construction organization that performs such surveys. For those who are not looking for simple ways, there is an option to determine the parameters yourself.

wind load

The wind creates significant pressure on the walls and roof of the building. The air flow, which meets an obstacle on its way, is divided, rushing in opposite directions: to the foundation and the overhang of the roof. Excessive pressure on the overhang can cause the roof to fall off. To protect the building from destruction, the aerodynamic coefficient is estimated, which depends on the angle of inclination of the ramp.
The steeper the slope and the higher the skate, the stronger wind load per 1m 2 surface. In this case, the wind tends to topple the roof. Hurricane winds have a different effect on sloping roofs - the lifting force lifts and carries away the crown of the house. Therefore, for areas with weak or moderate wind strength, roofs with any ridge height and angle of inclination can be designed. And for places with strong gusts of wind, low-slope species from 15 to 25 ° are recommended.

In addition to the horizontal impact, the wind exerts pressure in the vertical plane, pressing the roofing material against the crate

Calculation of wind load on a gable roof

The design wind load is the product of two components: normative value parameter (W) and coefficient (k), which takes into account the change in pressure depending on the height (z). The standard value is determined using the wind load map.

The territory of the country is divided into 8 zones with different nominal values ​​of wind load

The height factor is calculated from the table below based on the respective terrain type:

1. A - coastal areas of reservoirs (seas, lakes), deserts, steppes and tundra.
2. B - urban area with obstacles and buildings 10–25 m high.
3. C - urban area with structures from 25 m in height.

Table: coefficient for calculating the wind load

Consider an example. It is necessary to determine the design wind load and draw a conclusion about the acceptable slope of the roof. Initial data: region - the city of Moscow with a view of the terrain B, the height of the house is 20 m. We find Moscow on the map - zone 1 with a load of 32 kg / m 2. By combining the rows and columns of the table, we obtain that for a height of 20 m and terrain type B, the required coefficient is 0.85. Multiplying two numbers, we determine that the wind load will be 27.2 kg / m 2. Since the value obtained is not large, it is possible to use a slope of 35–45 °, otherwise it is necessary to take a slope angle of 15–25 °.

Snow load

Snow masses accumulating on the roof exert a certain pressure on the roof. The more snowdrifts, the greater the load. But not only the pressure of snow is dangerous, but also its thawing when the temperature rises. The average weight of freshly fallen snow per 1 m 3 reaches 100 kg, and in its raw form this figure is tripled. All this can cause deformation of the roof, violation of its tightness, and in some cases lead to the collapse of the structure.

The greater the slope of the slope, the easier the snow deposits are removed from the roof. In areas with heavy snowfalls, a maximum slope of 60º should be taken. But the construction of a roof with a slope of 45º contributes to the natural removal of snow.

Under the influence of heat coming from below, the snow melts, increasing the risk of leaks.

Calculation of snow load on a gable roof

The snow load value is obtained by multiplying the average load (S) characteristic of a certain type of terrain and the correction factor (m). The average value of S is found on the snow load map of Russia.

The territory of Russia includes 8 snow regions

The correction factor m varies depending on the slope of the roof:

• with a roof angle of up to 25 0 m equals 1;
• the average value of m for the range 25 0 -60 0 is 0.7;
• for steep roofs with an angle of more than 60 0, the coefficient m is not included in the calculations.

Consider an example. It is necessary to determine the snow load for a house with a slope angle of 35 0 located in Moscow. On the map we find that the required city is located in zone 3 with a snow load of 180 kg/m 2 . The coefficient m is taken equal to 0.7. Therefore, the desired value of 127 kg / m 2 will be obtained by multiplying these two parameters.

The total load, consisting of the weight of the entire roof, snow and wind loads, should not exceed 300 kg / m 2. Otherwise, you should choose a lighter roofing material or change the slope of the slope.

Roof type: attic or non-attic

There are 2 types of gable roofs: attic and non-attic. Their names speak for themselves. So, the attic (separate) roof is equipped with a non-residential attic, and the non-attic (combined) roof is equipped with an exploited attic. If you intend to use the space under the roof for storing items that are not used in everyday life, then it makes no sense to increase the height of the roof ridge. Conversely, when planning a living room under the roof, the height of the ridge should be increased.

The height of any type of roof must be sufficient to carry out internal repairs.

For non-residential roofs, the height of the ridge is determined by fire safety rules. Building regulations say that the attic should contain a through passage 1.6 m high and 1.2 m long. For residential roofs, the height is set based on their convenience of living and trouble-free placement of furniture.

Type of roofing material

Until recently, the construction market offered only a few types of roofing materials. It was traditional slate and galvanized steel sheet. Now the assortment has noticeably replenished with new products. When choosing a material for a roof, several rules should be considered:

1. With a decrease in the dimensions of piece roofing materials, the angle of inclination is increased. This is due to the large number of joints, which are potential places for leaks. Therefore, they try to make the rainfall as fast as possible.
2. For roofs with a low ridge height, it is preferable to use rolled roofing materials or large-sheet sheets.
3. The more the roofing material weighs, the steeper the roof slope should be.

The interval of possible slopes is described in the manufacturer's instructions for installation of the roof.

The cost of a gable roof

It is logical that with an increase in the slope of the slope, the roof area increases. This leads to an increased consumption of sawn and roofing materials and components (nails, self-tapping screws) for their fastening. The cost of a roof with an angle of 60 ° is 2 times more than the creation flat roof, and a slope of 45 ° will cost 1.5 times more.

The greater the total load on the roof, the greater the cross section of the beam is used for the rafter system. With a slight slope of the roof, the step of the crate is reduced to 35-40 cm or the frame is made solid.

Accurate calculation of roof dimensions will save the family budget

Video: rafter system and roof parameters

Calculation of roof parameters

To quickly calculate the dimensions of the roof, you can use the online calculator. Initial data are entered into the program fields (building base dimensions, type of roofing material, lifting height), and the result is the required value of the slope of the rafters, roof area, weight and amount of roofing material. A small minus - the calculation steps are hidden from the user.

For greater understanding and clarity of the process, you can carry out independent calculations of the parameters of the roof. There is a mathematical and graphical method for calculating the roof. The first is based on trigonometric identities. A gable roof is represented as an isosceles triangle, the dimensions of which are the parameters of the roof.

Using trigonometry formulas, you can calculate the parameters of the roof

Calculation of the slope angle of the roof slopes

The initial data for determining the slope angle is the selected roof height and half of its width. As an example, consider a classic gable roof with symmetrical slopes. We have: the height of the ridge is 3 m, the length of the wall is 12 m.

Dimensions c and d are usually called the laying of the roof

Slope calculation sequence:

1. We divide the conditional roof into 2 right-angled triangles, for which we draw a perpendicular from the top to the base of the figure.
2. Consider one of the right triangles (left or right).
3. Since the design is symmetrical, the projections of the slopes c and d will be the same. They are equal to half the length of the wall, i.e. 12/2 = 6 m.
4. To calculate the slope angle of slope A, we calculate its tangent. From the school course, we remember that the tangent is the ratio of the opposite leg to the adjacent one. The opposite side is the height of the roof, and the adjacent side is half the length of the roof. We get that the tangent is 3/6 = 0.5.
5. To determine which angle the resulting tangent has, we will use the Bradis table. Finding a value of 0.5 in it, we find that the slope angle is 26 0.

Simplified tables can be used to convert tangents or sines of an angle to degrees.

Table: determination of the slope of the slope through the tangent of the angle for the range 5–60 0

Calculation of the rise of a gable roof and the height of the ridge

The height of the roof is closely related to the steepness of the slope. It is determined in the reverse way to the slope method. The calculation is based on the angle of inclination of the roof, which is suitable for the area, depending on the snow and wind load, the type of roof.

The more bias, the more free space under the roof

The procedure for calculating the rise of the roof:

1. For convenience, we divide our “roof” into two equal parts, the axis of symmetry will be the height of the ridge.
2. We determine the tangent of the selected roof slope angle, for which we use Bradis tables or an engineering calculator.
3. Knowing the width of the house, we calculate the size of its half.
4. We find the height of the slope according to the formula H \u003d (B / 2) * tg (A), where H is the height of the roof, B is the width, A is the angle of the slope of the slope.

Let's use the given algorithm. For example, it is necessary to set the height of a gable roof of a house with a width of 8 m and an angle of inclination of 35 0 . Using a calculator, we find that the tangent of 35 0 is 0.7. Half the width of the house is 4 m. Substituting the parameters into the trigonometric formula, we find that H \u003d 4 * 0.7 \u003d 2.8 m.

Properly calculated roof height gives the house a harmonious look

The above procedure refers to determining the rise of the roof, that is, the distance from the bottom of the attic floor to the fulcrum of the rafter legs. If the rafters protrude above the ridge beam, then the full height of the ridge is determined as the sum of the rise of the roof and 2/3 of the thickness of the rafter beam. So, the total length of the ridge for a roof with a rise of 2.8 m and a beam thickness of 0.15 m is 2.9 m.

In places where ledges are cut for assembly with a ridge run, the rafters are reduced by 1/3

Calculation of the length of the rafters and the width of the roof

To calculate the length of the rafters (hypotenuse in right triangle) can be done in two ways:

1. Calculate the size using the Pythagorean theorem, which says: the sum of the squares of the legs is equal to the square of the hypotenuse.
2. Use the trigonometric identity: the length of the hypotenuse in a right triangle is the ratio of the opposite leg (roof height) to the sine of the angle (roof slope).

Let's consider both cases. Suppose we have a roof height of 2 m and a span of 3 m. We substitute the values ​​\u200b\u200binto the Pythagorean theorem and we get that the desired value is equal to square root out of 13, which is 3.6 m.

Knowing the two legs of a triangle, you can easily calculate the hypotenuse or the length of the slope

The second way to solve the problem is to find the answer through trigonometric identities. We have a roof with a slope angle of 45 0 and a rise of 2 m. Then the length of the rafters is calculated as the ratio of the rise number of 2 m to the slope sine of 45 0, which equals 2.83 m.

The width of the roof (in the figure Lbd) is the sum of the length of the rafters (Lc) and the length of the eaves overhang (Lkc). And the length of the roof (Lcd) is the sum of the length of the wall of the house (Ldd) and two gable overhangs (Lfs). For a house with a box width of 6 m and overhangs of 0.5 m, the width of the roof will be 6.5 m.

Building codes do not regulate the exact value of the slope length, it can be selected in a wide range of sizes

Roof area calculation

Knowing the length of the slope and the width of the roof, you can easily find its area by multiplying the indicated dimensions. For a gable roof, the total roof area is equal to the sum of the areas of both surfaces of the slopes. Let's take a look at a specific example. Let the roof of the house be 3 m wide and 4 m long. Then the area of ​​​​one slope is 12 m 2, and the total area of ​​\u200b\u200bthe entire roof is 24 m 2.

Incorrect calculation of the roof area can lead to additional costs when purchasing roofing material

Calculation of materials for the roof

To determine the amount of roofing materials, it is necessary to arm yourself with the area of ​​\u200b\u200bthe roof. All materials are overlapped, so when buying, you should make a small margin of 5-10% of the nominal calculations. Correct calculation the amount of materials will significantly save the construction budget.

General rules for calculating lumber:

1. Dimensions and section of the Mauerlat. The minimum possible cross-section of a beam is 100 × 100 mm. The length corresponds to the perimeter of the box, the margin for connections is set in the region of 5%. The volume of the beam is obtained by multiplying the dimensions of the section and the length. And if you multiply the obtained value by the density of wood, then there is a mass of lumber.
2. The size and number of rafters. The calculation is based on the total load on the roof (pressure of the roofing cake, snow and wind). Let's assume that the total load is 2400 kg/m 2 . The average load per 1 m of rafters is 100 kg. Given this, the footage of the rafters will be 2400/100 = 24 m. For a rafter length of 3 m, we get only 8 rafter legs or 4 pairs. The cross section of the rafters is taken from 25x100 mm and above.
3. The amount of material for the crate. It depends on the type of roofing: for bituminous tiles, a continuous crate is constructed, and for corrugated board or asbestos-cement slate, a sparse one.

Consider the calculation of roofing materials using the example of a metal tile. This is sheet material mounted on the roof in one or more rows.

Calculation sequence:

1. Determining the number of sheets. The metal tile sheet has a total width of 1180 mm and a working width of 1100 mm. The latter is smaller than the real one and is not taken into account in the calculation, since it goes to overlap the joints. The number of sheets is defined as the ratio of the total width of the roof (together with overhangs) to the useful width of the sheet. Moreover, the result of the division is rounded up to the nearest whole number. So, for a roof with a slope width of 8 m and a Monterrey metal tile sheet 1.1 m wide, the number of sheets is found by the formula: 8 / 1.1 \u003d 7.3 pcs, and taking into account rounding, 8 pcs. If the canvas is laid in several vertical rows, then the length of the slope is divided by the length of the roofing sheet, taking into account the overlap between the sheets up to 15 cm. Considering that the roof is gable, the value is doubled, that is, 16 sheets are required in total.
2. Determination of the total area. To determine the total area of ​​\u200b\u200bthe roofing material, the number of sheets is multiplied by the total area (the product of the total width and length) of one sheet. In our case, 8 * (1.18 m * 5 m) \u003d 47.2 m 2. For gable structures, the result is multiplied by two. We get that the entire roof area is 94.4 m 2.
3. Determining the amount of waterproofing. Standard roll waterproofing material has an area of ​​65m2 without overlap. The number of rolls is obtained by dividing the total roof area by the area of ​​the film, i.e. 94.4 m 2 / 65 m 2 = 1.45 or 2 full rolls.
4. Determining the amount of fasteners. There are 6-7 self-tapping screws per 1 m 2 of the roof. Then, for our situation: 94.4 m 2 * 7 = 661 self-tapping screws.
5. Determination of the number of extensions (skates, wind bars). The total footage of the planks is 2 m, and the working area is 1.9 m due to partial overlap. Dividing the length of the slope by the working length of the slats, we obtain the required number of extensions.

Video: calculation of materials for a gable roof using an online calculator

The graphical method for determining the parameters of the roof is to draw it on a reduced scale. For him, you will need a piece of paper (plain or millimeter), a protractor, a ruler and a pencil. Procedure:

1. The scale is selected. His optimal value is 1:100, i.e., for every 1 cm of a paper sheet, there is 1 m of the structure.
2. A horizontal segment is drawn, the length of which corresponds to the base of the roof.
3. The middle of the segment is found, from the point of which a perpendicular is drawn upward (a vertical line at an angle of 90 0).
4. With the help of a protractor, the required angle of the roof is laid off from the border of the roof base and an inclined line is drawn.
5. The intersection of the inclined line with the perpendicular gives the height of the roof.

Video: manual calculation of materials for a gable roof

The first thing they pay attention to is the visual appearance of the roof. Architects make sure that the roof is in harmony with the facade of the building. But beauty alone is not enough. It is important to correctly calculate the parameters so that the design is durable and functional. Neglect of snow and wind load, installation of rafters at the wrong angle can cause the destruction of the roof. And an incorrect determination of the roof area will lead to additional costs for the purchase of missing materials. Therefore, one should responsibly approach calculations, paying attention to all the nuances.