Calculation of the ridge of a gable roof. How to calculate the height of the ridge of a gable roof? Calculation of the ridge on a wooden roof

The buildings 26.06.2020

The buildings

The process of selecting the best parameters for a gable roof is always a search for a compromise between the desired shape of the frame, the desire to obtain a beautiful high structure and the requirements for ensuring the strength and stability of the roof. In addition, the dimensions of the gable roof will have to be linked to the weather "tricks" of the local climate and their own financial capabilities.

What determines the height of the ridge of a gable roof

To get a durable and beautiful design, first of all, you need to choose the optimal angle of inclination of the gable roof. This is a basic parameter, it must be selected based on the following criteria:

The strength of the truss system, the higher the angle, the less the load on the frame from snow, the precipitation is removed faster and more efficiently;
The presence of strong winds, the right angle helps to reduce pressure on the roof slope;
The height and dimensions of the attic space. The larger the volume of the attic air cushion, the warmer the gable roof will turn out. If you correctly calculate and plan the height of the ridge beam, the attic can be turned into an additional living room.

Important! In addition to the above conditions, it is necessary to take into account the weight of the structure, the longer the rafters and overhangs of a gable roof, the greater its weight, which loads the walls of the house, and the higher the cost of construction.

At what angle for a gable roof is the optimal height of the ridge

In contrast to the design process, it is quite difficult to work with angular values during direct construction. In order to directly determine and accurately set the angle of inclination of the slope, accurate measuring equipment is required. Instead of the angle of the rafters, it is easier to use linear values, such as the length of the rafters, the size of the span, or the height of the ridge. The desired angle of inclination in this case is easy to calculate using trigonometric formulas by measuring the height of the ridge and the distance between the supports of the rafters on the Mauerlat.

Climatic and technological restrictions on the height of the gable roof ridge

For areas where the main factor is open space, respectively, strong wind loads, the height of the ridge is most often calculated based on the recommendations of the roofing material manufacturer.

In such conditions, the main factor determining the stability of a gable roof is the wind load. Rain water and sleet do not pose a particular threat due to the sweeping effect of horizontal air currents, so there is no need to increase the angle of inclination of the roof structure. Moreover, with a significant height of the ridge, the windage of the gable roof and the pressure on the walls of the building sharply increase.

Experts do not recommend reducing the height of the ridge beam to a minimum. Firstly, it significantly reduces the thermal insulation qualities of a gable roof and reduces the amount of usable space in the attic.

Secondly, the air currents no longer press the roof with a reduced ridge height to the box of the building, but tend to overturn or tear it off the supporting surface. This situation is much worse than the situation with windage, since a gable roof is not designed for excessive internal pressure. Thirdly, certain types of roofing material cannot be laid on roof slopes with an extremely low ridge height. If such a situation arises, it is better to seek advice from specialists in a particular type of roofing material, who will help calculate the margin of safety and installation method.

If a large amount of precipitation in the form of wet snow is recorded on the ground, the height of the gable roof ridge and, accordingly, the steepness of the slopes is calculated according to the following scheme:

The maximum amount of wet snow that has fallen in a given area over the past decades is determined;
Based on the future dimensions of the house box and financial capabilities, the maximum size of the rafters and the bearing capacity of the roof frame are determined with the established snow cover thickness. The number of rafters, the height of the lift and the pitch are calculated based on the methodology set out in SNiP 2.01.85 "Loads and Impacts";
If the size of the beam under the rafters turns out to be prohibitively large, it is necessary to increase the height of the ridge, but so that the angle of inclination of the gable roof does not exceed the optimal values for the selected roofing material.

When calculating the load on the rafters, it is assumed that with a ridge height that provides an angle of inclination of more than 60 °, the weight of the snow mass on the surface of a gable roof can be ignored. If the ratio of the height of the ridge above the Mauerlat horizon to the distance between the lower supports of the rafters is less than ¼, the snow pressure on the roof is taken into account in full. In an intermediate position, with an increase in the angle of inclination of a gable roof from 20° to 60°, the correction reducing factor changes monotonously from 0.7 to 0.1.

The optimal height of the ridge of a gable roof

Often, the decision to increase the height of the ridge is made not to reduce the load on the roof, but to increase the usable space of the attic. The benefit of such a modification, at first glance, is obvious. You can increase the amount of usable space and equip, for example, an attic and even a balcony. It is relatively easy to evaluate changes in the shape and size of the under-roof space using the diagram shown in the figure.

Before making a decision, try to calculate the geometry of the consequences of increasing the height of the ridge. Consider, as an example, the change in the characteristics of the height and dimensions of a gable roof for the smallest building with a size of 6x4m and a wall height of 2.5m. A sketch of the roof structure is shown in the figure.

With an optimal height of the ridge above the floor slab of 2 m, the length of the rafter beam will be 2.9 m. At the same time, the usable space under the gable roof will be only 4x1.8x0.5 m. This is enough for ventilation and roof insulation work. The width of the useful space used, if desired, can be increased to 1.5 m. On this area, you can organize a bedroom or a rest room, for which, in fact, the attic is used.

An angle of inclination of 45 ° with a ridge height of 2 m provides optimal structural strength, if you choose the right material and calculate the beam consumption for the construction of rafters, you can get a very moderate cost of the rafter system, primarily due to the absence of struts and struts.

You can try to increase the width of the attic comfort zone from 0.5 m to 1.5 m. In this case, the height of the ridge and the angle of inclination of the gable roof will increase to 3.6 m and 60 °, respectively. The space available for use has increased from 1.5 m to 2.5 m, the comfort zone, or the area within which you can walk without bending down, is 1.5 m, which is consistent with the average attic parameters for a country house.

The length of the rafters has increased from 2.9 m to 4.2 m. It is expected to increase the cost of timber for the gable roof frame by 30% due to the need to install additional power elements - crossbars and struts. If you correctly calculate the loads and the method of fastening, the structure will be as strong as in the previous version.

Alternative option

Even a cursory comparison of the two options, without trying to calculate the exact characteristics, allows us to draw certain conclusions.

The size of the useful area of the attic in the broken version of the roof is larger than that of the gable scheme with an increased height of the ridge by 15%, the amount of timber and roofing materials was spent more by 19% and 7%, respectively. The cost of work for a broken circuit is 30-33% higher. The gable roof structure is 0.8 m higher, but the center of gravity of the frame is below the center of pressure, which allows it to be more stable in strong winds, despite the fact that the angle of the rafters is 60o higher than the angle of the top row of a broken roof.

In addition, large air "bags" above the ceiling and in the side walls of the attic of the gable version well insulate and soundproof the room. For a long stay in the attic room, a broken circuit is more suitable due to increased comfort. Whereas for a country house or a bath it is quite possible to use the design of a classic gable roof with an increased height of the ridge beam.

The above comparison is valid only for small-sized gable and broken circuits. As the size of the house increases, the gable version of the roof with an increased height of the ridge beam becomes much more expensive than the cost of a similarly sized broken pattern.

Conclusion

It should be noted that the calculation of the required height of the ridge depends to a large extent on the type of roofing material. On a slope with an angle of inclination of 60 °, the vast majority of roofing materials fit perfectly, from tiles to ondulin. Due to the fact that the roof slope is a single plane, the laid roof has a significantly higher resistance to any form of precipitation. Broken structures often suffer from rainwater leaks during heavy rain with wind precisely on the fracture line.

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One of the main building elements is the roof. The viability of the house and the peace of its inhabitants depend on its quality and the correctly chosen form.

Any pitched roof consists of several basic elements. These include:

truss system;
crate;
Roof.

A preliminary calculation when designing a house should help determine the required amount of materials for its construction. Based on this, a budget (estimate) of expenses is drawn up. It is impossible to calculate the cost of a roof without determining its shape and height.

In modern construction, almost all forms of roofs existing in architecture are common. One-slope and two-slope, as well as four-slope (hip) species are widespread.

In addition to them, there are hipped roofs, and domed, and broken (attic) and complex multi-pitched.

Among the most widely used roofs are gable roofs, which are a simple structure consisting of two inclined slopes and two gables - vertical walls of a triangular shape.

Roofs of a gable structure are usually mounted on a garage, garden gazebo. The gable roof with an attic also looks original.

The truss system of such roofs consists of paired parts located at an angle to the horizontal line. Their stability is ensured by a plank or solid crate.

The upper part of the gable roofs, the junction of the rafter legs was called the ridge. This is the uppermost part of the entire building on which many owners of private houses install a decorative weather vane.

To determine the area of \u200b\u200bthe roof and calculate the number of boards for the crate, roofing material and the length of the logs themselves, you need to learn how to calculate the height of the ridge.

You can quickly and accurately calculate a gable roof, including determining the height of the ridge, using an online calculator on the Internet.

Parameters affecting the height of the roof

The roof is the upper part of the building, so it takes all the loads that fall on it. In winter, this is the accumulation of snow on the roof, during the year - the wind effect, which is the greater, the larger the area of \u200b\u200bthe slopes and the steeper they are located relative to the horizontal.

When designing, you can slightly reduce the influence of weather factors. So, when using smooth roofing materials, such as corrugated board or metal tiles, you can significantly reduce the amount of snow that will accumulate. With a sufficient angle of inclination, it will slide down without significantly increasing the load on the rafter system and the crate.

To reduce the wind load, it is desirable to make roofs with a smaller slope. But this is fraught with the formation of large snowdrifts, which, when the snow melts, can lead to the collapse of the roof. Therefore, it is necessary to find a "golden mean" between increasing and decreasing the angle of inclination of the roof.

We draw your attention to

about OSB boards - material for roofing lathing.

Also, an article about ondulin may be useful to you.

Determine the height of the skate

The first way is mathematical

To calculate the height of the ridge of a gable roof, it is necessary to present its design in a cross section. It will be an isosceles triangle. Therefore, the height of the skate will be the height of this triangle.

Having built the height (perpendicular to the base of the triangle), we get two right-angled triangles, in which one of the legs will determine the parameter we need. The second leg can be determined by dividing by 2 the total width of the house.

To comply with the optimal operating conditions of the house in conditions of high rainfall and sufficiently strong winds, the slope angle of the roof slopes is taken in the range of 20o - 45o. Calculate the height of the ridge of a gable roof, based on the specified parameters, will help the Pythagorean theorem and the Bradis table.

According to the theorem known to everyone since school years, the length of one leg (ridge height) will be determined as the product of the second leg (half the width of the house) by the tangent of the angle opposite the desired leg (roof slope angle).

We give the value of the tangent of the angles from 20o to 45o with a step of 5o.

For example, we calculate the height of the ridge for a standard wooden house 6x8 meters, located in the middle zone of our country, with a roof slope of 40o. In accordance with the above formula, the leg at our disposal will have a length of 3 meters (6:2 = 3).

The tangent of the angle 40o is determined from the table. It is equal to 0.839. We multiply the numbers we know and get:

Thus, with the specified parameters, the height of the ridge from the house will be 2.517 meters.

Method two - graphic

Less accurately, without the use of mathematical formulas and tables, you can determine the height of the ridge by making an image of the roof section on a small scale. To do this, draw an isosceles triangle and draw the median, which will also be the height.

The angle at the base of the triangle must be accurately drawn using a protractor. When correcting for the accuracy of mathematical tools, you can get an approximate value of the quantities you are looking for.

Important! After completing the process of mounting the ridge on the roof, it is necessary to cover the ridge run with lightweight side tiles. This is required by the installation of a pitched roof ridge.

Thus, the height of the gable roof ridge is calculated. When planning to use the attic, it is necessary to determine the optimal parameters of the internal space for the free movement of residents and guests of the house.

Watch a video on building a gable roof ridge and installing rafters:

ratings, average:

The aesthetic indicators, architectural specifics and technical characteristics of the house depend on the height of the roof ridge. It is extremely important when developing a project to correctly determine the correct size of the structure. To get the perfect result, we suggest that today you figure out how to calculate the height of the ridge of a gable roof, and which method is better to use in independent calculations.

Guidelines for choosing the height of the ridge

A ridge is 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 his own ideas often runs counter to technical regulations, familiarization with which will help to avoid serious mistakes.

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:

. In areas where the weather conditions are characterized by frequent gusty winds, it is customary to build flat and low-pitched roof structures with an inclination angle of up to 10º. In regions with weak and moderate winds, the height of the ridge can be any.

Precipitation. Precipitation is a potential threat of leaks, due to which they become damp, then the elements of the rafter system and the roofing pie gradually become unusable. From roofs with a steepness of more than 45º, precipitation is removed much faster than from flat structures.

Snow mass. In areas with heavy winter precipitation, the construction of roofs with a slope of more than 45º is recommended in order to optimize the rate of snowfall. Lower and flat roofs will need to be cleared of snow more frequently.

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 by a 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 exploited attic are built mainly according to a broken pattern, involving the construction of a truss system of two tiers.

The height of the ridge of an exploited 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. The size of the top of the sloping roof is 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 of the ceiling system of 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 are of the semi-mansard type. They are erected according to the usual 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.

Without an attic and an attic floor, low roofs of garages, small household buildings, and warehouses are being built. 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 the geometric figure we created, 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 of the roofing. It will help to determine the optimal height of the designed structure.

There are several rules for selecting roofing material, taking into account the height of the ridge and the steepness of the roof, these are:

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 fractions, 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, laid out at a given angle from the extreme point of the cornice overhang. Let's analyze one of the illustrative examples of graphical 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 the construction standards for the construction of wooden structures, prescribed in the collection of joint ventures 64.13330.2011. Ideally, the processes of compression and crushing of the wooden parts of the system should be taken into account.

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.

The height of the roof affects the appearance of the house, the complexity of assembling the truss frame and technical characteristics. Therefore, it is important to pay special attention to sizing and only then purchase material. In order to make calculations, it is not necessary to contact specialized organizations. In the article we will discuss how to correctly calculate the height of the roof, as well as what affects it.

What affects the height of a skate?

A ridge is a horizontal edge connecting the tops of two roof slopes. Overestimation and underestimation of the height negatively affects the operation of the roof, spoils the appearance of the building. Therefore, when calculating, it is not enough to be guided only by your own taste. Before calculating the height of the skate, it is important to pay attention to various technical conditions.

In the article, we will default to roofs with equal slopes in length and angle of inclination. This will make it easier to determine the height, although all the principles described apply to asymmetrical structures.

According to geometry, one of the slopes will be the hypotenuse, and the distance from the ridge to the base will be the leg.

type of roofing;
attic room;
atmospheric phenomena.

Now let's go over each item in more detail.

Roofing

Different materials have their own slope requirements. The calculation of the height of the gable roof ridge will depend on this indicator. There are general principles for choosing material depending on the slope angle:

For small piece elements, the slope of the slope should be greater than for long sheet materials. This is due to the fact that when moisture accumulates in the joints, leaks may appear. Therefore, ridges for a slate roof are higher than ridges for a metal roof. The fact is that the length of the wave slate is only 1.75 m, and the metal roofing material can occupy the entire length of the slope.
The height of the ridge roof also affects the number of joints. With an underestimation of the angle, the number of joints and overlaps should also decrease. Therefore, large-sheet and roll materials are considered the most reliable options.
Heavy roofing elements are placed on steep slopes. Roofs made of slate and ceramic tiles have a large mass, so they make a steep slope. So, they do not bend the rafter beams.

It is worth remembering that the steeper the slope, the more material will be needed to cover the roof. So, if we take as 100% the need for a slope angle of 7-10 °, then an angle of 45 ° will require 150% overrun, and an angle of 60 ° - all 200%.

The dimensions of the slopes relative to the width of the house will change along with the height of the ridge.

Attic space

There are two types of houses: with and without an attic. Each option has its own conditions for calculating the height of the ridge. If the attic is residential, then 30-40 cm is added to the height of the tallest owner. But it is better to think about the guests by making the ceiling at a height of 2.4 meters. But it is important to remember that this is only the ceiling, not the height of the roof. Here you will need to add another half a meter or more, depending on preferences.

If the attic is non-residential, then the height of the ridge is calculated under the influence of fire safety. One of the points obliges the owners to provide a through passage under the roof with a height of at least 1.6 meters and a width of 1.2 m. With complex truss systems, these dimensions can be reduced by 0.4 m. This space will provide free air exchange and passage for repairs, inspection.

Barren buildings are built in such a way that additional walls are erected over the ceiling of the previous floor. For example, in semi-mansard buildings, the height of the walls is increased by 1.4 meters. In such structures, the height of the roof is measured from the lower edge of the Mauerlat. Such designs are suitable for climatic zones with strong winds. This makes it possible to reduce the slope of the slope.

Non-attic structures are popular in the construction of garages, warehouses and other small residential buildings. Usually they do not provide for an attic floor, thereby saving material and time.

atmospheric phenomena

Climatic conditions directly affect the height of the ridge. Therefore, in different cities there is a "golden" slope slope. Atmospheric factors include the following:

Precipitation. The more snow it rains in your area, the more slope you need to do. Accordingly, the height of the roof also increases. If this condition is neglected, then the likelihood of leaks increases.
Wind. For areas with medium and low winds, there is no difference in the height of the ridge. But so, where strong, gusty winds often blow, usually the roof slope does not exceed 10 °. This imposes certain restrictions on the materials used. Without taking into account the strength of the wind, you risk losing the entire roof structure.
The amount of snow. There is a relationship between the steepness of the slope and the amount of snow. The more it falls in winter, the greater the angle you need to make. The reason is the increased load on the truss system. It is recommended to give preference to slopes with a slope of more than 45 °.

You can determine the features of the region of residence by contacting the local weather service or reference literature. The regulatory documentation SNiP 23-01-99 or SP 20.13330.2011 has weather maps and recommendations for construction.

Ways to calculate the height of the ridge

The calculation of the height of the roof largely depends on your preferences. There are two main ways:

mathematical;
graphic.

Let's deal with the mathematical method of counting. As already mentioned in the first subheading, a gable isosceles roof was taken by default. We have the ability to calculate the required height if we know the slope angle and the distance between the slopes. Now you need a Bradis table and a calculator. In the reference literature we find the value of the tangent of our angle, and then we multiply it by half the length between the slopes. The result is the height of the skate.

Let's consider the calculation on a real example. Suppose that our building has dimensions of 7x10 meters. At the same time, we are in an area with medium winds, and we use metal tiles as roofing. We do not plan to equip the attic, but we will take the slope equal to 20 ° so that rainwater drains without problems.

It turns out that the length of the leg is 7/10 = 3.5 meters. According to the table, the tangent of 20° is 0.839. Now we multiply the resulting numbers: 3.5 * 0.839 \u003d 2.94. This means that the height of the gable roof ridge, from the bottom of the Mauerlat, is 2.94 meters.

The graphical method is suitable for those who have a sheet of paper, a pencil and a ruler with a protractor at hand. All that is needed is to draw the roof in section, observing the scale. To do this, draw a horizontal line, mark the boundaries of the roof base on it. Determine the midpoint and draw a perpendicular. On one side, use a protractor to draw a line at the desired angle. The intersection point will show the height, you just need to measure it with a ruler.

The resulting result will be approximate, you also need to add 2/3 of the thickness of the rafter leg to it. Small deviations are acceptable and do not critically affect the operation of the roof. These errors are made up of the need to make ventilation under the metal tile and battens.

In order to mark the desired height in reality, it is enough to determine the middle of the building. Then nail a vertical bar or pole at the desired height. After the calculation has been made, try to transfer it as accurately as possible from paper to a real building. Then the roof will last for many years and will not leak on the rainiest days.

The roof is an important structural part of the house, performing a number of the most important functions. It protects against atmospheric adversity and removes precipitation, provides insulation and makes a solid contribution to the formation of its own building style. In order for such a significant structure to "excellently" cope with the entrusted work, it is necessary to thoroughly think over the project and scrupulously figure out the dimensions.

Careful analysis and calculation of a gable roof is required for both independent craftsmen and owners of suburban property who resort to the services of construction organizations. Let's figure out how to do it right.

The roof, resembling an inverted V in a section, leads the list of pitched structures for a reason. In terms of simplicity of construction and economy, a gable roof has practically no rivals. For centuries, proven in practice, they are the basis for the construction of most roofing structures.

Unpretentious pitched planes do not require complex cutting of the coating and other materials, which results in an impressive amount of waste. No specific tricks are needed to implement intricate configurations. Precipitation does not linger on sloping surfaces, so there is no need to strengthen the waterproofing. As a result, the installation of a gable roof is often cheaper than a shed roof.

A roof with two slopes can be an independent object or part of a complex of structures of a similar or different form. Its simplest version does not have built-in dormer windows and canopies over the entrance porch, i.e. there are no additional fractures, ridges and accompanying valleys.

The absence of convex and concave corners deprives the master of "pleasure" to suffer with a number of difficult operations. Again, the owners will not get imaginary pleasure from leaks, which often appear at the joints of the pitched roof elements.

In principle, no one bothers fans of bizarre architecture to equip two slopes with numerous built-in structures. True, there are climatic limitations: in areas with a high volume of winter precipitation, the construction of roofs with numerous components is undesirable. In the grooves formed by excesses, favorable conditions are created for the accumulation of snow deposits. They will have to be cleaned faster than usual, and excessive zeal in the field of snow removal can cause damage to the coating with all the consequences.

However, adherents of simple and clear forms should not relax either. The corner roof configuration must be perfectly matched and calculated, otherwise it will not be able to perform the entrusted work flawlessly.

Despite the deceptive elementarity, there are tricks in determining the optimal form of the structure. It is impossible to overcome and get around them without knowing the technological subtleties, because all the parameters of the structure are interconnected:

The width of the gable roof depends on the dimensions of the box and the type of coating, which in turn affects the selection of the steepness of the slopes.
The slope of the roof depends on the climatic features of the construction area and on the type of roofing material.
The combination of the above circumstances, width and slope, determines the height of the structure, which in the end may not meet architectural requirements and aesthetic considerations.

The impeccably designed roof has all the proportions perfectly matched. Its width and height determine the rise and slope necessary for the removal of precipitation in a particular area. Lower is impossible for technical reasons, higher is expensive and unreasonable, unless the unique architecture requires it.

Note that, coupled with an increase in steepness, the construction budget also increases. According to the slope, roofing material is selected. Focusing on its weight and specifics, design and calculate the truss frame. The calculation of the truss frame is carried out taking into account the listed parameters and taking into account the loads acting from the outside on the structure.

The interdependence of the proportions of the roof, the complexity of the construction of the truss frame and the nuances of the selection of the coating makes it necessary to determine the best shape through a banal selection. If something does not fit, replace or strengthen the supporting structures. Fortunately, the assortment on the construction market is now plentiful, and all kinds of methods have been developed to strengthen the structure.

If the upcoming calculations and shuffling of data are scary, it is better to resort to a win-win solution - a typical project. It is not for nothing that abroad all the houses of one settlement are equipped with roofs of equal height and covered with material of the same color and characteristics. Typification allows you to maintain landscape identity and reduce design costs.

However, even a typical design solution is not a panacea for technical troubles and aesthetic shortcomings. We must not forget about the individual dimensions of the box over which it is planned to build a roof. Compatriots deny leveling in height and steepness, therefore it is still desirable for us to deal with the proportions of the roof structure.

Step by step calculations

The configuration and dimensions of any pitched roof are set by the truss frame. On the edges of the rafter legs, slopes are laid, forming a dihedral angle. They construct truss systems from rolled metal and wood, use industrial structures and lumber in construction.

Let's look at the options available for the efforts of an independent master, i.e. construction method of erecting a roof frame from lumber.

Stage # 1 - choosing the type of truss system

The method of constructing a gable roof is indirectly related to the dimensions, but without taking into account the difference in the arrangement of structures, it will be difficult to understand the geometric parameters.

In the construction of gable roofs, two traditional technologies are used:

Layered, according to which the top and bottom of the rafters have a strong fulcrum. The walls of the house, equipped with a Mauerlat, serve as the lower support. The top of the layered rafter legs rests on a running beam that forms a ridge. The girder is supported on a support system built specifically for it, on the inner wall or on the stone gables of the box, erected to the roof. The layered method is mainly used in the arrangement of large houses with an internal load-bearing wall or a row of columns.
hanging, according to which the tops of the rafters rest only against each other. The walls serve as a support for the bottom, as in the previous case. Hanging rafter legs form an equilateral triangle, the base of which is called a puff. Taken together, such a system does not create thrust, i.e. does not transfer the bursting load to the walls of the box. Rafter triangles are installed either ready for installation, i.e. assembled on the ground, or constructed from separate rafters on site. The absence of an upper support makes adjustments to the scope of use: the hanging method is used in the arrangement of only small buildings with small spans.

Schemes of truss systems of both types include a minimum of structural elements when overlapping boxes up to 8-10m wide.

When arranging spans larger, there is a danger of deformation of the rafter legs. To eliminate sagging and deflection of wooden parts made of lumber, reinforcing elements are installed: struts, contractions, side runs, etc.

Additional details provide rigidity and stability of a large structure, but increase the load. How the total load is determined and produced, we have already analyzed.

Step #2 - Width Calculation

Both types of wooden truss systems are built along the floor beams or along the Mauerlat. How the width of the roof is calculated depends on the type of base:

When mounted on floor beams, it is they who form the cornice overhang, i.e. determine the dimensions of the roof.
When installed on a Mauerlat, the width of the roof is determined by adding three values. You need to sum up the width of the box and two projections of the width of the cornice overhang. However, only the bearing part of the width of the roof, equal to the width of the box, is used in the calculations.

The function of the Mauerlat in frame buildings is performed by the upper trim, which at the same time connects the disparate elements into a single frame. In wooden construction, the upper crown, folded with a bar or log, serves as a Mauerlat.

In the case of using the "beam" scheme of the device, the so-called matrices are used - bars or logs laid under the upper crown of the foot as an overlap.

Eaves overhangs of roofs installed on the Mauerlat can be formed directly by rafter legs, fillies sewn to them or a brick ledge. The latter option, of course, is used in the construction of brick walls. The choice of the width of the overhang is dictated by the type of roofing and the material from which the walls are composed.

For a slate roof no more than 10cm;
For bituminous tiles in the range of 30-40cm;
For metal tiles 40-50cm;
For profiled sheet 50cm;
For ceramic tiles 50-60cm.

Walls made of logs and timber require enhanced protection from slanting rains, therefore the overhangs above them are usually increased by 10-15 cm. If the limit value of the overhang width recommended by the manufacturer is exceeded, it is necessary to provide for measures to strengthen it.

It is possible to install external struts on the walls or support pillars, which can simultaneously play the role of structural elements of the terrace, porch, veranda.

Stage # 3 - determining the slope

The angle of inclination of the slopes is allowed to vary within the widest limits, on average from 10º to 60º with permissible deviations in both directions. Traditionally, both planes of a gable roof have equal angles of inclination.

Even in asymmetric structures for residential buildings, they are mainly located at an equal angle, and the effect of asymmetry is achieved by constructing different-sized slopes. Most often, differences in the slope of the main parts of the roof are observed during the construction of country houses and domestic facilities.

The procedure for determining the optimal steepness of a gable roof is significantly influenced by three factors:

The type of coating, coupled with the weight of the crate intended for it. The type of roofing material determines the installation technology and the method of arranging the base for its fastening. The denser the roof is, the lower the value of the slope can be. The fewer overlaps and joints between the elements of the coating, the lower the roof is allowed to be. And vice versa.
Roof weight with. A heavy coating located at an angle to the horizon presses on the base only with its projection. In short, the higher the slope, the less mass is transferred to the floor. Those. under a heavy roof you need to build a steep roof.
Climatic specificity of the region. The high slope helps to quickly drain snow and water, which is highly desirable in areas with significant rainfall. However, high slopes are very sensitive to the effects of winds that tend to overturn them. Therefore, in regions with characteristic strong winds, it is customary to build gently sloping structures, and in areas with abundant rainfall, roofs with a high slope.

In the regulatory documentation used in calculating the angles for the construction of gable roofs, there are units that can confuse inexperienced home builders in roofing. The simplest value is expressed in dimensionless units, the most understandable - in degrees.

The second version conveys the ratio of the height of the roof to half its width. To determine it, a line is drawn from the central point of overlap to the top of the roofing triangle. The real line is drawn on the diagram of the house, imaginary at the facility. The value is indicated either as a percentage, or as a mathematical ratio such as 1: 2.5 ... 1: 5, etc. In percentages, it is wiser and more inconvenient.

Stage # 4 - determining the height of the skate

A roof with two slopes, at the request of the owner, may or may not have an attic. In the attic spaces of gable roofs, it is not supposed to arrange useful premises. There is for this. However, the height of the attic used for servicing and inspecting roofs at an angle is not arbitrary.

According to the requirements of the fire service from the top to the ceiling should be at least 1.6 m. The upper limit is dictated by the aesthetic beliefs of the designers. They argue that if the height of the roof is greater than the height of the box, then it seems to “press” on the building.

The height of the ridge top for hanging roofs arranged on beams is easiest to determine by the drawing method:

We draw a diagram of the box of the house on a scale.
We are looking for the middle of the upper floor.
From the middle up we lay the axis of symmetry.
On either side from the middle, we set aside half the width of the roof - we get the extreme point of the overhang.
With the help of a protractor, from the extreme point of the overhang, we draw a straight line at an angle recommended by the roofing manufacturer. The point of its intersection with the axis will be the top of the roof. We measure the distance from the top to the overlap, we get the height.

To get a complete picture, on the diagram you need to draw a second slope in a similar way. Parallel to the lines of the drawn slopes, two more lines must be drawn at a distance equal to the thickness of the rafter legs on the same scale.

If the configuration of the roof does not suit you, you can "play" with the height on paper, changing the position of the vertex point and the slope of the roof within reasonable limits. The same manipulations can be carried out in one of the drawing programs.

When drawing the outline of a roof constructed using layered technology, the thickness of the running beam should be taken into account. With impressive power, it will slightly shift the position of the slopes.

Craftsmen believe that the calculations of the elements of the truss system for the construction of a gable roof can generally be reduced to calculating only the section of the run. This is the most loaded element, all the others have the right to be thinner. For example, if calculations show that a 100 × 150 mm material is required for a ridge run, then a 50 × 150 mm board is enough for rafters, supports, struts.

The process of finding the height of structures with overhangs formed by filly is slightly different from the described method. It’s just that the slope angle is drawn not from the extreme point of the overhang, but from the lower attachment point of the rafter to the Mauerlat. In any case, it is better to choose variations with the steepness and dimensions of the gable roof planned for construction on “paper” than on the construction site.

Stage # 5 - calculation of material consumption

A normal owner thinks ahead of time about the construction budget. True, in the preliminary estimate, by definition, there will be inaccuracies. The process of erecting a gable roof will impose its own adjustments on the initial calculation of the material, but it will help to find out the amount of basic expenses.

The preliminary estimate should include:

Beam for the Mauerlat device. In residential construction, lumber with a cross section of 100 × 150 mm to 200 × 200 mm is used. The footage is calculated around the perimeter of the box with a 5% margin for processing and connections. A similar material is purchased for the bed device, if it is designed.
Board for the manufacture of rafters. Most often, for the manufacture of rafter legs, material is used with a cross section from 25 × 150 mm to 100 × 150 mm. The footage is determined by multiplying the length of the outer edge by the number. The material is purchased with a margin of 15-20%.
A board or bar for making struts, puffs and supports with a section of 50 × 100, 100 × 100 mm, depending on the project. You also need a margin of about 10%.
Material for the device of the crate. Its consumption depends on the type of finish coating. The crate is constructed either solid, if it will be produced, or sparse for corrugated board, metal tiles, ordinary tiles, slate, etc.
Roll waterproofing, the footage of which determines the type of roof and the steepness. High roofs are covered with a waterproofing carpet only along the overhangs, the ridge and in convex or concave corners. Gentle ones are covered with a continuous carpet.
Finish coating. Its amount is calculated by summing the area of the slopes. If there are embedded dormer windows, then their areas are also calculated. Only calculated as a rectangle, not in fact. The amount of laying stock is recommended by the coating manufacturers.
Material for sheathing gables and overhangs.
Corners, plates, self-tapping screws, staples, nails. We need anchors and studs, their number will tell the project.

You will also need shaped elements for arranging through passages through the roof, valleys, overhangs, ridge. The cost estimate presented is valid for a cold design. For an insulated roof, it will be necessary to purchase insulation and a vapor barrier film, a bar for a control batten and material for roof sheathing from the inside.

What determines the height of the ridge of a gable roof

The strength of the truss system, the higher the angle, the less the load on the frame from snow, the precipitation is removed faster and more efficiently;
The presence of strong winds, the right angle helps to reduce pressure on the roof slope;
The height and dimensions of the attic space. The larger the volume of the attic air cushion, the warmer the gable roof will turn out. If you correctly calculate and plan the height of the ridge beam, the attic can be turned into an additional living room.

At what angle for a gable roof is the optimal height of the ridge

Climatic and technological restrictions on the height of the gable roof ridge

For areas where the main factor is open space, respectively, strong wind loads, the height of the ridge is most often calculated based on the recommendations of the roofing material manufacturer.

The maximum amount of wet snow that has fallen in a given area over the past decades is determined;
Based on the future dimensions of the house box and financial capabilities, the maximum size of the rafters and the bearing capacity of the roof frame are determined with the established snow cover thickness. The number of rafters, the height of the rise and the step are calculated based on the methodology described in SNiP 2.01.85 "Loads and impacts";
If the size of the beam under the rafters turns out to be prohibitively large, it is necessary to increase the height of the ridge, but so that the angle of inclination of the gable roof does not exceed the optimal values for the selected roofing material.

When calculating the load on the rafters, it is assumed that with a ridge height that provides an angle of inclination of more than 60 °, the weight of the snow mass on the surface of a gable roof can be ignored. If the ratio of the height of the ridge above the Mauerlat horizon to the distance between the lower supports of the rafters is less than ¼, the snow pressure on the roof is taken into account in full. In an intermediate position, with an increase in the angle of inclination of a gable roof from 20 ° to 60 °, the correction reducing factor changes monotonously from 0.7 to 0.1.

The optimal height of the ridge of a gable roof

With an optimal height of the ridge above the floor slab of 2 m, the length of the rafter beam will be 2.9 m. In this case, the usable space under the gable roof will be only 4x1.8x0.5 m. This is enough for ventilation and work on the insulation of the roof. The width of the useful space used, if desired, can be increased to 1.5 m. On this area, you can organize a bedroom or a rest room, for which, in fact, the attic is used.

Alternative option

Even a cursory comparison of the two options, without trying to calculate the exact characteristics, allows us to draw certain conclusions.

The size of the useful area of the attic in the broken version of the roof is larger than that of the gable scheme with an increased height of the ridge by 15%, the amount of timber and roofing materials was spent more by 19% and 7%, respectively. The cost of work for a broken circuit is 30-33% higher. The gable roof structure is 0.8 m higher, but the center of gravity of the frame is below the center of pressure, which allows it to be more stable in strong winds, despite the fact that the angle of the rafters is 60 degrees higher than the angle of the top row of a broken roof.

Conclusion

Options for calculating the area of the roof ridge have their own characteristics. You should know the following values:

The sum of the entire length of the skates;
Width and length of the structure;
How many ridges and total length;
How many stingrays are present and what type they are.

When covering the skate with soft and flexible materials, the following formula is used:

Roof area = (2 x eaves width + whole house length) x (2 x eaves width + whole house width) / cos (corner slope). With all this, it is necessary to take into account the entire coverage area, and the valleys must be calculated in a separate order. Then, the amount of material used will depend on the type of metal tile used.

The structure of a gable roof is almost similar to the structures of other pitched types.

To cover the roof use:

Slate;
Metal tile.

Roof units have units of shaft ventilation passages and chimneys that go through the roof covering. The individual method of constructing nodes and their quality directly depend on the type of roof.

The gable roof consists of the following structures:

Rafter;
crate;
overhangs;
Mauerlat;
thermal insulation;
horizontal ribs;
Waterproofing;
rack;
Valleys.

To calculate a soft roof, take into account:

Structural elements;
Calculation of the height of the roof and rafter system;
Consider overhangs of cornices, overlaps and overlaps of skates.

The whole calculation will be exactly the same as that of a gable roof, but there are some differences. The main difficulty is that this roof will have more than one angle of inclination, and before starting the calculation, we recommend that you use the “golden section” rule, which will allow you to fit the roof outline into a circle. This action will help to avoid the most common drawback: if the calculation is performed incorrectly, the roof will look very ugly.

Pay special attention to the calculations, because the entire reliability of the structure, its long service life and aesthetic appearance will depend on this. Do the calculations in advance, otherwise, you may lose a significant amount of money and spend time reworking all the shortcomings.

A gable roof is a complex, large building structure that requires a professional approach to design and work. The biggest costs go to building materials for rafters, battens, insulation, waterproofing, roofing material. Our gable roof calculator will allow you to calculate the amount of material.

Using a calculator saves roof design time and money. The final 2D drawing will guide the work, while the 3D visualization will give you an idea of what the roof will look like. Before entering data into the online calculator, it is necessary to have an idea about the elements of the roof.

Rafter parameters

To calculate the truss system of a gable roof, you need to consider:

roof load;
step between rafters.
type of roofing

100-150 mm with a span of no more than 5 m, and with additional props .;
150-200 mm with a span of more than 5 m, with a step of more than 1 m, and if the angle is not large.

Important! The distance between the rafters of a gable roof is usually set to 1 m, but with a roof slope of more than 45 degrees, the pitch of the rafters can be increased to 1.4 m. With flat roofs, the pitch is 0.6-0.8 m.

Rafter legs are attached to the Mauerlat, which runs along the perimeter of the house. For him, either a board with parameters 50x150 mm, or a bar 150x150 mm (for load distribution) is taken

Lathing parameters

For a metal tile, a sparse crate is created with a board, the width of which is 100 mm, and the thickness is 30 mm. The board is stuffed with a step that should correspond to the longitudinal axis of the metal tile module - 35 cm (supermonterrey).

For flexible tiles, the crate is carried out with a large step, since OSB or plywood will be laid on top of it with a continuous carpet.

Important! When choosing materials, pay attention to indicators of moisture resistance and minimum thickness.

When constructing warm roofs, a counter-lattice is made between the waterproofing and the roof with a bar, the thickness of which should be 30-50 mm.

Roofing parameters

To calculate the roof of a gable roof, you need to know the dimensions of the roofing material and the size of the overlaps.
A metal tile for a hard roof is produced with a width of 118 mm (working 110), but the length can be different. The manufacturer under the order can cut any length.
Flexible tiles for soft roofs have different sizes, so you need to look at the specific material
As for the choice of insulation, for Russia a minimum thickness of 100 mm is recommended, and the correct one will be 150-200 mm.