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# Articles

# How to calculate the angle of inclination of the roof

**How to calculate the angle of inclination of the roof**

**Projects constructed suburban mansions can consider many requirements, wishes and even fads or "kaprizov9raquo; the owner of their respective owners. But always their "rodnit9raquo; common - without a solid roof never do any of their buildings. And in the foreground should go not only architectural delights the customer's specific requirements as to the structure element in this regard. This reliability and stability of the truss system and roofing, roof full performance of its direct purpose - protection against moisture penetration (and in some cases, in addition, even heat and sound insulation), if necessary - the functionality located directly below the roof space.**

**Design of the roof structure - it is extremely responsible and quite difficult, especially for complex configuration. The most sensible thing would be to entrust this work to professionals who own methods of carrying out the necessary calculations and appropriate software for this purpose. However, the home owner may also be interested in some of the theoretical aspects. For example, it is important to know how to calculate the angle of the roof on their own, even approximately - to start. This will give the opportunity to immediately estimate the opportunity to realize their "copyright prikidok" - by matching your actual conditions of the region, according to "arhitekture9raquo; the roof, on the planned roofing materials on the use of the attic. To some extent, the calculated angle of slope of the roof will make a preliminary calculation of parameters and the number of timber for the rafter system, the total area of the roofing.**

**In what quantities it is more convenient to measure the angle of the roof?**

**It would seem - a completely unnecessary question, since all at school know that the angle is measured in degrees. But clarity is still needed, because in the technical literature, and reference tables, and in the usual everyday life of some skilled craftsmen are not uncommon, and other units of measurement - percentages or relative aspect ratio.**

**And one more thing you need clarification - that is taken as the angle of the roof?**

**The inclination angle - the angle formed by the intersection of two planes: the horizontal and the plane of the roof slope. In the figure it is shown by the letter of the Greek alphabet α.**

**We are interested acute angles (obtuse skates can not be simply defined) lies in the range from 0 to &09deg;. Skates cooler 50 ÷ 60 ° in "chistom9raquo; an extremely rare and is usually for decorative roof - in the construction of the pointed towers in the Gothic style. However, there are exceptions - such steep slopes may be the bottom row of the rafters of the roof mansard.**

**Yet often we have to deal with slopes lying in the range from 0 to 45 °**

**With degrees clear - all probably represent a protractor with its divisions. A ka to be with a different unit?**

**Nothing too complicated.**

**The relative aspect ratio - is maximally simplified fraction showing a ratio of a height lifting ramp (shown above denotes Latin H) to the projection of the roof slope to the horizontal plane (the diagram - L).**

**L - this may be, depending on the design of the roof, half the span (at symmetric gable roof) completely span (if pent roof), or in complex configurations roof indeed linear section defined conducted to the horizontal projection. For example, in Scheme mansard roof portion of such a well is shown - the horizontal beam from the angle to the vertical upright, extending from the top of the lower rafter.**

**slope angle and recorded fraction, e.g. "1: 3".**

**However, in practice it often happens that the use value of the slope angle in such a representation would be extremely inconvenient if, for example, the numbers in the fraction obtained non-circular and irreducible. For example, there is little to say inexperienced builder ratio of 3: 11. In this case there is an opportunity to use another quantity measuring roof slope - percent.**

**This value is located is extremely simple - just need to find the result of dividing the already mentioned fractions, and then multiply it by 100. For example, in the above example 3: 11**

**3: 11 = 0,2727 × 100 = 27.27%**

**Thus, the value obtained slope of the roof slope, expressed as a percentage.**

**And what to do if you want to switch from degrees to percent, or vice versa?**

**You can remember this relationship. 100% - the angle 45 degrees when the legs of the right triangle equal to each other, i.e. in this case the height of the ramp is equal to the length of its horizontal projection.**

**In this case, 45 ° / 100 = 0,45 ° = 27'. One deviation percentage is 27 angular minutes.**

**When approached from the other side, 100/45 ° = 2,22%. That is, we find that one degree - this is 2, 22% slope.**

**For ease of transfer values from one to the other, you can use the table:**

**Calculation of the roof inclination,**

**The roof should be reliable and beautiful, and it is possible with the right determination of its angle of inclination for this type of roofing material. How to calculate the angle of the roof - in the article.**

**Appointment of roof space**

**Before calculating a roof angle should be defined so as to be used attic space. If you plan to make it a living, the angle of inclination will have to do more - to the room was spacious and the ceiling above. The second output - making scrap a mansard roof. Most often, such a roof is made of a gable, but it can also have four ramp. Just in the second version is very much complicated turns truss system and without an experienced designer simply can not do, and most prefer to do everything on their own, with their own hands.**

**The higher the horse, the more useful area of roof space. But at the same time increases and the roof area**

**By increasing the roof pitch angle should remember a few things:**

**Significantly increased by roofing materials costs - increases rays area.****Long slopes greater impact wind load. If you compare the load on the same building with an angle of 11 ° and 45 °, and in the second case it is more than the nearly 5-fold. To the roof can withstand such loads, truss system made reinforced - put the beams and rafters of larger cross-section with a smaller step. And this - the increase in its value.****If the angle of slope is greater than 60 °, snow loads are not taken into account - rainfall roll and are not delayed. But if device polygonal mansard roof snow loads considered when calculating its upper part - there are plane inclination less than 60 °.****Not all roofing materials can be used on steep slopes, so carefully SRAs in the tilt angle, which can be used data of the roof.**

**The inclination angle is displayed as ratio ridge height and half the width of the building**

**This does not mean that low-slope roofs better. They cost less on materials - less roof area, but there are nuances:**

**Require measures to snow retention to prevent an avalanche of snow gathering.****Instead of snow guards can be heated roof and gutter system - for the gradual melting of snow and timely drainage.****For a small slope is great likelihood that moisture will flow into the joints. This entails reinforced waterproofing measures.**

**So with a small slope of the roof - it is not a gift. Conclusion: calculate the angle of the roof must be so to find a compromise between the aesthetic component (house should look harmoniously), practical (at podkrovlelnom residential space) and financial (expenses must be optimized).**

**The inclination angle depending on the roofing material**

**The roof on the house can have almost any kind - may have low slopes, can - almost vertical. It is important to correctly calculate its parameters - section of rafters and a step of installation. If you want to lay on the roof of a certain type of roofing material, it is necessary to take into account indicators such as the minimum and maximum tilt angle for the material.**

**Minimum angles are registered in reviews (see table above), but manufacturers often give their recommendations, so it is advisable to decide on a particular brand at the design stage.**

**Most roof pitch is often determined on the basis of how they are made from the neighbors. From a practical point of view it is right - in terms of the nearby houses are similar, and if the neighbor's roof are good, do not flow, it is possible to build on their parameters. If the neighborhood is not the roofs roofing material that you want to use, you can start with the calculations of averages. They are given in the following table.**

**As you can see in the graph "how to do" in most cases, have a solid range. So it is possible to vary the appearance of the building, even with the same roof. In fact, besides the practical role of the roof and even jewelry. And the choice of the angle of inclination of its important role played by the aesthetic component. Make it easier to program, making it possible to display the object in the three-dimensional image. If you use this method, then calculate the angle of the roof, in this case - to choose from a designated range.**

**The effect of climatic factors**

**An angle of inclination of the roof affects the amount of snow falling in the winter in a particular region. Also taken into account in the design wind loads.**

**Map of Russia Snow loads**

**All more or less simple. According to long-term observations whole territory RF is divided into zones with the same snow and wind load. These zones are marked on the map, painted in different colors, so it is easy to navigate. Map specifies the location of the house, find the area on it - the value of wind and snow load.**

**Map of snow loads worth two digits. The first is used when calculating the strength of the structure (our case), the second - the determination of the allowable deflection of beams. Once again, in the calculation of the angle of the roof we use the first digit.**

**The main task of calculating snow load - take into account the planned roof pitch. The steeper the slope, the smaller the amount of snow on it can be kept correspondingly smaller section of the rafters or larger step of the installation is required. correction factors are introduced to take account of this parameter:**

**angle less than 25 ° - ratio of 1;****from 25 ° to 60 ° - 0.7;****on roofs with a slope of more than 60 ° snow loads are not taken into account - the snow is not retained on them in sufficient amounts.**

**As we can see from a list of coefficients, the value is changed only on roofs with an inclination angle of 25 ° - 60 °. For the rest, this action has no meaning. So, to determine the actual snow load on the roof planned, taking the value found on the map is multiplied by a coefficient.**

**And all this roof should withstand**

**For example, forward snow load in Lower Housing Novgorod roof slope angle - 45 °. Map this fourth zone, with an average snow load of 240 kg / m 2. Roof with ramp requires adjustments - the value found is multiplied by 0.7. We obtain 240 kg / m 2 * 0.7 = 167 kg / m 2. It is - only part of the calculation of the roof angle.**

**Effect of snow calculate simple - the more snow in the region, the greater the potential load. Predict wind behavior is much more complicated. It can only be guided by the prevailing winds, location of the house, and its height. These data when calculating the angle of inclination of the roof are recorded using the coefficients.**

**Map of the Russian Federation wind loads**

**The position of the house in relation to the wind rose is of great importance. If the house is worth between higher buildings, the wind loads will be lower than when it is in an open area. All the houses on the type of arrangement is divided into three groups:**

**"A" zone. House located in open areas - in the desert, desert, tundra, on the banks of rivers, lakes, seas, etc.****"B" zone. The houses are located in a wooded area, in the small towns and villages, with a barrier to wind up to 10 m in height.****'B' zone. Buildings which are built-up areas, not less than 25 m tall.**

**The house is considered to belong to this zone if the specified environment is at least 30 times the height of the house. For example, a height of 3.3 meters at home. If a distance of 99 meters (3.3 m * 30 m = 99) are only a small one-storey houses or trees, it is considered to belong to the area "B" (even if geographically located in a large city).**

**Depending on the area entered coefficients, taking into account (shown in the table) the height of the building. Then they are used in the calculation of wind load on the roof of the house.**

**For example, calculate the wind load for Nizhny Novgorod, one-storey house is located in the private sector - refers to the group "B". Map find area of wind loads - 1, wind load to it 32 kg / m 2. Table find coefficient (for buildings less than 5 meters), it is equal to 0.5. Multiply: 32 kg / m 2 * 0.5 = 16 kg / m 2.**

**But that is not all. We must also take into account the aerodynamic components of the wind (under certain conditions he seeks to thwart the roof). Depending on the wind direction and the impact the roof, it is divided into zones. In each of them there are different loads. In principle, each zone can be put rafters of different sizes, but do not do - is unreasonable. To simplify the calculations recommend taking performance of the busiest zones G and H (see table).**

**Coefficients to account for aerodynamic wind load component**

**Found coefficients used to wind load calculated above. If the coefficient of two - negative and positive component, is considered both values, and then they are added together.**

**The values found for wind and snow loads are the basis for calculating the section rafters and steps to install them, but not only. The total load (weight of the roof construction + + snow, wind) should not exceed 300 kg / m 2. If after all calculations of the amount you get more, you have to, or choose a lighter roofing materials, or reduce the angle of inclination of the roof.**

**Thus, conclusions. Calculate the angle of the roof - rather, it is to choose one of the options. It is only important that this choice was correct.**

**Learning how to determine the angle of inclination of the roof**

**Angle of a roof depends on many factors, but the most important of them - is the construction of roof covering and its material. So, the flat roof inclination angle is small, but the roof made using truss - a separate issue. It is particularly important to properly calculate the required angle of tilt, as it affects the removal rate of precipitation from the roof. Typically, this indicator is expressed in degrees, percentage or ratio of the legs. In this article we will learn how to define the desired angle of inclination of the roof.**

**Degree roof slope of the measure shows us the angle formed on the roof with respect to the horizon. Roofs with a large angle of inclination is called steep, with small - gentle.**

**Determination of the angle of inclination at different measurement values**

**As you know, to determine the angle of inclination of the roof, you need to know exactly what will be used roofing.**

**Typically, the following materials can be used as a covering pitched roofs:**

**slate;****Flexible roll roofing materials****metal;****roofing;****natural tile;****profiled et al.**

**If we imagine the right-angled triangle, we can understand that it is the hypotenuse in any case more than the legs, so the optimum angle of inclination of a particular roof will assume the lowest permissible rate. How do we determine the angle of the roof? First of all, this index depends on the density of the roofing and sealing the entire roof structure as a whole. This is due to the fact that the roof with a large angle of inclination have a larger sail area, so you need a good seal. And on the roof with a small angle stingrays will be delayed rainfall, thereby creating a higher load on the cover.**

**In the table below, you can access schedule, which helps determine the angle of inclination of the roof as a percentage and a ratio of the legs. It is also possible to link these indicators to the definition of the degree of the angle measure. To understand how to use the graph look at the angle of inclination of 50%. Thus it is seen that the ridge height (H) is placed in the leg twice at the base of the triangle (L / 2), this yields a ratio of 1: 2.**

**The most convenient way of calculating the angle of inclination of the roof is the dimensionless ratio (ratio of the legs). For example, the index angle of slope as a ratio of 1/3 indicates that for determining the height of the ridge is necessary to find the midpoint of the span and move up the third part of its length.**

**Roofing type roof and the angle of inclination**

**To give some perspective on the upper and lower permissible limits the angle of the roof with the use of a roof covering, we have developed a special table. The study of various instruments, as well as monitoring during construction allowed us to draw conclusions about the conditions of the use of different roofing materials.**

**However, it is worth remembering that the construction market is rapidly filled with new materials, and the performance of the existing roof covering can improve in the course of development of modern technologies. Therefore, over time the strength of some materials may be increased as a result of the roof inclination angle may vary.**

**The lower limit of the angle of inclination of the roof**

**As for the maximum angle of inclination of the roof, the roofing for light materials such as pulp and bituminous coating, soft roofing, corrugated board and metal, it may even be greater than 1: 1. The maximum slope of the rest of roofing you can see in the table below suggested.**

**The upper limit of the angle of inclination of the roof**

**So you can easily and quickly convert degree angle measure in percentages, can take advantage of the proposed table.**

**Knowing the angle of the roof, you can easily calculate the height of the standing of the ridge. In order to facilitate this calculation, you can use the suggested following table, where each corner of the roof in degrees corresponds to a certain relative value, which will help to calculate the height of the ridge beam. To do this, ½ length of the span of the roof multiplied by the index of the rightmost column of the table.**

**For example, the span length in your house is 16 meters, and the projected angle of slope is 30 degrees. Find the height of the ridge as follows: 16: 2h0,59 = 4.72. In this case, the number 0.59 is taken from a table of bookkeeping that the angle of inclination of the roof is 30 degrees.**

**Now that you know how to find the angle of the roof, from which performance depends on this value. We hope that our table to help you easily navigate the values of the slope of the roof slope.**