Four-pitched roofs are the most popular option in modern private construction. Often, developers have a question: how to calculate the area of a hipped roof. This is necessary to determine the amount of roofing material, waterproofing and insulation.
Today, calculations can be made using computer programs designed for all types of roofs. This has its advantages: high accuracy, the ability to choose different design options, convenience. However, some builders choose to rely on their wits and not spend money on things they can do on their own.
Before proceeding with the calculation of the roof area, a detailed plan should be drawn up, where all dimensions will be applied. Not a single roof element should be overlooked. In addition, already at the stage of designing a house, you should decide on the choice of roofing material, since the slope of the roof depends on this. The sharper the angle of inclination, the longer the roof slope. This means more material consumption. In addition, each roofing material is different. For example, profiled metal sheets require much more overlap during installation than, say, natural tiles. 
Having an accurate calculation of the roof area of a house, you can choose the most profitable roofing material, as well as insulation, steam and waterproofing.
Four-pitched roofs can vary in shape:
- directly four-slope;
- half-hip;
- hip;
- four-slope gable.
The easiest way to calculate are the areas of roofs, the slopes of which are regular trapezoids and triangles and do not have any kinks on the slopes.
However, in modern construction, hip roofs are increasingly being erected, with many slopes, the surface of which can consist not only of triangles and trapezoids, but also rhombuses, rectangles and other geometric shapes.
That is why, before starting the calculation of the hipped roof, it is advisable to refresh your knowledge of the course of school geometry.
Self-calculation of the gable roof area
As mentioned earlier, the first step is to draw up a complete roof plan. If there is no house project or the rafter system has already been installed, then the roof plan will have to be drawn up according to the existing frame. All you need is a tape measure and an angle. This tool measures all roof lines, from ridge to floor. If the roof is multi-level and consists of different heights, then in the drawing it is necessary to reflect where what is the height. It is also advisable to draw up a plan of the roof in the projection. This will help to most clearly present the picture. However, it is only necessary to draw up a roof projection if you have drawing skills.
Having drawn up a detailed drawing, it will not be difficult to decompose the roof into separate geometric constituent elements. This is necessary for more accurate calculations.
Remember that the size of the roof cannot be limited only by its perimeter. It is also necessary to add the length of the roof overhangs where expected.
Rules that must be followed when calculating a hipped roof:
The simpler the shapes are, and the more parameters you know, the easier it will be to calculate.
- The length of one slope is determined by measuring the distance from the extreme line of the cornice to the ridge.
- Each roof slope is calculated as follows: the area of the figure is multiplied by the cosine of the angle at which this roofing element is located.
- If any slope is an irregular rectangle, it must be divided into regular geometric shapes. And also carry out the calculation of each separately.
- After the calculations of each element have been made separately, the obtained digital values are summed up.
Calculation example.
For example, we will give the calculation of the roof of a hipped roof.
Suppose that our hipped roof consists of the following elements: two regular trapezoids and two isosceles triangles. The roof slopes are at an angle of 30 °. The cosine of this angle is 0.87.
Trapezoidal slopes have the following parameters: one side 10 m, the other 7 m, height 3 m.
Triangular slopes: two sides 3.34 m each, one side 7 m. The height of the triangle is 4.8 m.
Let's get down to the calculations.
The area of the trapezoid is found as follows: we sum up the length of the horizontal sides, divide by 2, and multiply by the height. That is, in our case: S = (10 +7) / 2 x 3 = 25.5.
Do not forget that the resulting number must be multiplied by the cosine of the angle, in our case by 0.87. As a result, the area of the trapezoidal slope is 22.185. Rounding up, up to 22.5 meters.
The final stage is the summation of all areas: S = 22.5 × 2 + 14.7 × 2 = 74.4. Round up to 75.
Thus, the area of the hipped roof, in our case, will be equal to 75 m2.
During the calculation, various small elements are not subtracted from the total area, such as: skylights, ventilation ducts, chimneys, parapets or skylights. Since their area is small, they do not entail any special financial costs. In addition, it is quite possible to make a calculation error.
Calculation of roofing and other materials
After the calculation of the gable roof has been carried out, and the total area has been calculated, you can begin to calculate the required footage of the roofing material. The opinion is erroneous that the area of the roof drawing and the area of the required material are the same. The bottom line is that all elements of the roofing material must be overlapped. In addition, each roofing material has its own technical indicators of the size of the overlap. Accordingly, the costs of materials increase significantly.
When calculating the required amount of roofing material for a multi-level roof, it is advisable to seek help from a computer program. It will make calculations faster and more reliable.
But you can do the calculation of the required material for a simple roof yourself. This does not entail any particular difficulties.
Let's give an example of calculating the amount of slate for our four-pitched roof, the area of which we calculated earlier.
To do this, we need to make a proportion:
X - 15%, where S is the roof area, X is a margin equal to 15%.
After X is calculated, the resulting number must be added to the area S. As a result, the area of the required amount of material will be obtained.
Thus, in our case, the proportion will look like this:
X = 15 x 75/100 = 11.25. round up to 11.5.
11.5 + 75 = 86.25 (m?) - the area of the required roofing material.
In addition, when calculating the required material, it should be remembered that waste will invariably remain, they may require up to 20% of the material. That is, again, a proportion should be drawn up, where X is now the flow rate. We add the resulting result to the area.
It remains only to calculate the number of roofing sheets. To do this, the resulting total area of the entire roof should be divided by the area of one roofing sheet.
When erecting a complex roof, you should take a stock of material not 15%, but not less than 20%.
The calculation of soft roofs is carried out according to the same formulas as the calculation of slate. Consumption depends on the type of roofing material and the technology of its installation. The areas of the valleys and skates are counted and ordered separately, since they are measured not in square meters, but in linear meters.
The length of the roofing sheets, determined by the height of the slope, is calculated by the dimensions of the roof of the house. As a rule, metal tiles are produced in lengths up to 8 meters. In this case, the thickness of the sheets ranges from 0.2 to 0.4 cm. As a result, long metal sheets bend very strongly. This can complicate the transportation process, as the sheets may break on the road. Therefore, when ordering metal tiles, take into account the area of the roof, roofing sheets, choose the most suitable dimensions. Also, take into account the qualifications of the workers who will be involved in the installation of the roof. Thus, with a roof area of up to 150 m? it is recommended to purchase roofing sheets up to 2 m long with a roof area of up to 250 m? roofing sheets up to 4 m long are preferable, with a roof area over 250 m? acquire sheets over 6 meters long. Metal sheets over 6 meters long are difficult to lay, as they bend very strongly. Experienced roofers must be hired to install them.
When transporting long roofing sheets, control over the loading, transportation and storage of the material.
Since the material consumption is high on complex roofs. It is preferable to purchase piece material. The piece is a soft roofing material such as flexible bitumen shingles. Thus, waste is minimized due to the small size of the elements. But with proper calculation and a responsible approach, the installation of the roof can be carried out in such a way that high costs can be avoided.
We draw your attention to the fact that soft roofs require the organization of continuous sheathing, as well as additional installation costs. At the same time, prices for these types of coatings are much higher.
Thus, the calculation of the hipped roof allows you to timely calculate the upcoming costs for the purchase of roofing material, insulation and waterproofing.
The first thing to do before starting to build a roof is to make accurate calculations. A detailed description of all connections and assemblies, an accurate drawing of the entire rafter system and the approval of this by an experienced person are required.
It sounds difficult, although in reality everything is simpler - no more difficult than a children's designer, it is only important to do everything right. And, if you are looking for how to calculate the rafter system of a hip roof, you will find all the information you need here!
So, what is a hip roof rafter system? This is a four-slope design, i.e. one that has four planes. Such a roof is much more complicated than a gable roof, but it is stronger and more reliable in operation. And her appearance is recognized all over the world as one of the most successful and aesthetic.
Here are the main advantages of this design:
- Due to the triangular end slopes in the hip roof, conventional skylights can be installed.
- Due to the absence of a sharp protrusion, the hip roof has a higher resistance to various atmospheric phenomena.
- The hip roof is considered economical due to the fact that it does not have gables.
- Temporary deformations of such a roof are reduced to zero - all thanks to its special design.
- Insulation of such a roof is much easier than that of a gable roof (there are no all the same problematic gables).
- High resistance to wind loads of the terrain - due to low slope angles.
- The ability to convert an attic space into a comfortable attic is easier and simpler. And this is already a valuable increase in the living area of the house.
Of the shortcomings, we will single out the main one: the rafter system of the hip roof is more complicated than that of the usual one, and therefore its installation will cost you more, although you will save on brickwork.
Types of hip roof construction
So, let's see what types and subtypes hip roofs are built today:
- Hip. This is a traditional hipped roof with triangular slopes on all end sides.
- The roof, in which the hip does not reach the eaves, is called half-hip.
- A hip roof is called a hip roof, in which identical triangles are connected together by one upper point. By the way, once upon a time in Russia they built just such roofs.
- A cruciform hip roof is a rarer type due to the high cost of execution and high labor intensity of work. Usually it is built on houses with complex layouts or separately only above the front doors.
Our scheme will help you to understand in more detail:
As we have already said, if the hip does not reach the eaves, the roof is called half-hip. It is in these places that dormer windows are installed, which completely solves the problem of the need for inclined dormer windows. But in terms of complexity and cost of construction, a half-hipped roof is higher than others.
The simplest example of a hip roof (quite aesthetic, note) is a triangular roof. All slopes here are the same size, and all angles are equal. If this height and design suits you, then give preference to this particular option - you will avoid many pitfalls and nuances!
The only point: the hip roof in its classic version is bad in that it has no vertical planes and dormer or attic windows have to be placed on inclined walls. As a result, such elements become the most unprotected in terms of leakage during rain.
Hip roof architecture in detail
For the device of a specifically hip roof, experienced builders recommend taking rectangular beams from conifers, and reinforcing the stability of the entire system with additional steel elements. Indeed, in addition to the rafters themselves, in any case you will need the following building elements:
- The Mauerlat is the lower support for the rafters.
- A run is a beam that needs to be placed parallel to the Mauerlat as another additional support.
- Racks and struts are supporting elements for a structure with a so-called multi-span.
- Crossbars are special elements that help to cope with spacers (a common occurrence with improper installation).
- Sprengel is another additional element of the rafter support.
- Lezhen - a special support for struts and struts.
So, the building material has been purchased? Now put all the parts in a stack or dry them additionally. The main thing is to consider protection from rain.
How to avoid calculation errors?
Now let's avoid the very first and most annoying hip roof design mistake - the lack of measurements of the house itself. The problem is that even trained craftsmen manage to start work by drawing up a plan and drawing a roof, but they do not work with the base - the walls. But only at first glance it seems that the walls are perfectly even, everything is parallel to each other and the like, but in fact, even a completely new house is far from ideal. And then, already only during the construction process, certain errors are discovered that prevent the first supports from being installed correctly.
Therefore, first of all, before carrying out any calculations on the hip roof, we arm ourselves with a ruler and a level. We check the elevation marks, parallelism of the walls, diagonals (the correctness of rectangular walls) and draw up a measurement plan of the house. Let's say you are surprised at some inaccuracies. And now we decide how to fix what:
- We correct a slight error in parallelism with a Mauerlat.
- We correct the slight difference in the heights of different walls with gaskets.
- We correct significant differences with additional elements of the rafter system, which we must include in the calculations.
In addition, we recommend that you do not make a simple two-dimensional drawing of the roof, but create a volumetric model that will give you a clear idea of your hip roof. At first glance, you can understand whether you like the result or not. Redoing something is quite difficult. And modern computer programs, which are quite a lot, will help you with this.
If you are looking for a ready-made roof drawing that fits the required parameters, do not take too detailed drawings with Latin abbreviations and formulas: they are needed only by the master who can read them. And so that you have an idea of what exactly awaits you, we offer you a simple master class on the construction of a hip roof, where all the elements are clearly visible:
What data is required for construction?
Here are the parameters of the future roof you should know before you start building it:
- Roof slope angle, on each side of the hip slopes.
- The angle of inclination of the roof from the sides.
- The exact area of the entire roof surface
- The weight of the future roof and the exact load of the roofing material on the roof truss system.
- The length of the diagonal rafters.
- The cross-section of the rafters, taking into account the regional wind and snow loads, the pitch of the rafters and the weight of the roofing material.
- The required volume of all rafters in cubic meters.
You will need to know the area of the entire surface in order to purchase the required amount of roofing material and calculate its future weight in advance:
Next - the rafters. On hip roofs, rafters are placed directed to the corners of the walls - to the inner and to the outer ones, and are called oblique or diagonal. The second ones are longer than the usual rafters, and the shortened ones are supported on them - the rafters. As a result, such rafters carry a load 1.5 times more than usual.
The length of the diagonal rafters is longer than the standard length, so they are made paired. Their advantage is that the double cross-section is designed for an increased load and, as a result, is a solid, uncut board. As a result, the constructive solutions for such a roof are quite simple. And in order to ensure the multi-span of the hip roof, one or two supports will need to be placed under the slant leg.
If you have already purchased scaffolding for the construction of the roof, then calculate the pitch of the rafters based on the section of the finished boards. If you have not purchased it yet, search now, before drawing up the project. After all, it is not uncommon for a project to be ready, but it turns out that good wood is obtained from the parameters that were not planned at all.
We bring to your attention a special free one.
What should be considered when calculating?
The hipped roof project is one of the most difficult. It is extremely important here not to be mistaken in the calculations, because the hip roof is a large number of very different elements, and each of them has an important function.
So, the slope of the hip roof usually varies from 5 to 60 °. Based on this, roofing material is chosen: roll coatings for small slopes and tiles for steep surfaces. But expect right away that the greater the angle of inclination of such a roof, the more roofing material you will end up with. And the smaller the angle, the more solidly the frame will have to be built, because a considerable load will now go on it.
For the final decision, you will have to consider all these factors:
- The total weight of the planned roofing material.
- Additional weight of waterproofing and insulation.
- Local climate features (check with your neighbors).
- The type of rafters and the presence of additional elements to maintain the strength of the roof.
- All devices and equipment that you are going to put on the roof.
It is important to take into account the wind and snow load so that your roof does not break through tons of snow and is not blown away by a dashing wind, and the weather conditions of a specific area will indicate what deformations of the rafter system are possible over the years (for example, dampness, sea air, etc. .).
Note that a hip roof usually has no problems with a wind load, but almost always with a snow one. The reason is that all the planes of the hip roof are inclined. Bad for the wind, but good for the snow.
Have you decided on a project? Did you do all the necessary calculations? Then get started!
The construction of a hip roof structure with four slopes is considered one of the most difficult construction and arrangement options due to the presence in the frame of numerous rather complicated interfaces. Until the construction of the rafter system begins, it is necessary to make a general calculation with the drawing, and only after that the situation will become clear how massive and heavy the rafter structure will turn out to be.
What is the calculation of a hipped roof
In any structure of a hipped roof, from the simplest hipped roof to a complex hip roof of a broken type, the calculation is performed according to the same scheme:
- Do-it-yourself sketch design of the hip roof is carried out according to the concept of construction and design assignment;
- The main drawing of the hip roof is being developed;
- The calculation of the hip roof, the most loaded parts of the frame of the hip hip roof is carried out;
- Clarify the dimensions of the main parts of the rafter system, carry out detailed drawings of individual units.
For your information! Only after performing calculations and detailing can you make an estimate and calculate the cost of building a beautiful hipped hip roof.
In this case, a methodology for manual calculation of a wooden frame and roof truss system is given. The method and the main stages of the calculation are not particularly difficult, even schoolchildren are quite capable of performing the design and understanding the calculations. If a person owns the calculation method, then he has a clear understanding of how the rafter, ridge and support beam works, where the weakest links of the hipped roof are located.
You can use any online program or CAD system to determine the dimensions, but sometimes you have to do the assessment of strength and stability on the go.
Hip roof device
Structurally, the classic four-slope hip roof consists of two main slopes and two side hips. To calculate the lengths and sections of the timber, it is necessary to draw up the most accurate sketch, or better -. Using diagrams with different versions of slope angles and roof heights, you can draw and calculate various options for the layout of the roof, and most importantly, determine the geometric dimensions of the most loaded frame parts.
The main structural elements of a hipped roof are:
- Ordinary rafter beams that form two main ramps. The rafters are exactly the same in shape and design as in a conventional gable roof. The slopes are shaped like an isosceles trapezoid;
- Hip angular, also called slant or diagonal rafters, are located in the corners of the roof frame and form the so-called hip slopes in the form of symmetrical isosceles triangles;
- Folk rafters, from which the plane of the hip slopes is formed;
- Vertical racks on which the ridge beam and all four ramps are supported.
In addition, a large number of auxiliary elements are used in the design, designed to increase the rigidity of the entire hipped frame. These are all kinds of struts, struts, sprengels installed as supporting elements of rafters, photo.
The longest rafters are called angular, the shortest are called rafters.
Calculation of the parameters of the roof frame
According to the conditions of the problem, it will be necessary, using the drawings, to perform an estimated calculation of the most loaded elements of the rafter system - the vertical support post and the rafter beam of the hipped roof. In addition, it is necessary to calculate their sizes and the position of the saw lines under the support surfaces on the Mauerlat and ridge run.
Usually, schemes with a single ridge run are used, as in the drawing, but if the under-roof space is planned to be used as an attic or an attic, in this case, the hipped roof is built according to a two-run scheme. This option is much more expensive, but allows you to get a more stable and rigid hip structure in the case of building a roof with a large slope surface.
Both versions of the hipped roof use layered rafters with fixation of the rafter beams on the Mauerlat and support on the ridge girder. The calculation of both hip roofs is carried out using the same method.
To complete the calculation, we need:
- Determine the loads acting on the hip roof frame;
- Check the strength and stability of the vertical support;
- Calculate the deflection and strength of the ordinary and diagonal rafter beams.
To perform the calculation, a simplified four-pitched hip roof scheme is used, shown below.
All elements of the frame of a hip hip roof can be conditionally divided into two groups - beams, including racks. The former work under deflection conditions or under the action of a bending moment. The second group of load-bearing elements refers to simpler cases, they work under conditions of linear compression or tension. In this case, the calculation of the bearing capacity of a compressed rack is determined from the conditions of static stability under a compressive load.
Methodology for calculating the stability and strength of vertical supports and struts
The first step is to determine the strength of the vertical strut based on the known value of the vertical load. The force of pressure on the vertical struts is calculated as the sum of three components - the mass of the roof with the roofing and the weight of the maximum snow cover. Since the slopes are located at an angle, the final vertical pressure perceived by the roof can be roughly taken as half the weight of the timber structures of the four-slope structure and the mass of snow, calculated based on the area of the roofing multiplied by the maximum weight of 1 m 2 of roof snow for a given region. 
The strength of the vertical support is determined from the following ratio:
σ = P / S ≤ M s, where M s is the specific compressive strength of a particular wood species, P is the vertical load under the weight of the hipped frame and the mass of snow, in kilograms, S is the total cross-sectional area of all vertical supports in this structure. The value obtained from the division should not be more than M s, a reference value, which can be taken from a reference book or SNiP No. II-25-80. For example, a stand made of dry pine with a section of 120 cm 2 can withstand a huge vertical load of almost 16 tons, so the strength calculation is not decisive.
Almost always, calculations of vertical struts are performed according to the margin of stability or the ability of the support to perceive a force without deformation and bending.
To classify the flexibility of the support, the concept of the flexibility coefficient λ is introduced, for a cube it is equal to 0, for most real wooden supports its value can be from 40 to 100 units.
The formula for calculating the stability of a long wooden rod, which is a support for a hipped roof, looks like this: σ = P / φS ≤ M s, where φ is the buckling factor, determined according to the provisions of SNiP No. II-25-80 by the formula:
- For λ values less than 70 units, φ is calculated by the formula: φ = 1 - 0.8 (λ / 100) 2;
- For λ values greater than 70 φ units, one obtains: φ = 3000 / λ 2 .
The practical value of φ ranges from 0.3 to 0.7.
The simplest way is to use a graph that allows you to obtain the exact value of φ from the dependence of λ - φ and the ratios of the length to the diameter of the support and to perform a verification calculation for stability.
The strength of the rafter
The calculation of bearing vertical supports, as a rule, is a verification one, since in reality the margin of safety and stability of racks made of a standard 100x150 mm beam is always greater for most hip roofs than is required in reality. It is much more important to check the strength of the diagonal rafter, which often break under the weight of snow due to insufficient stiffness.
To check the strength of the rafter beam for load, the standard formula is used - (Р / φS) + (M z / W z) ≤ M y , where :
- P is the total load from the weight of the hip roof structure, snow cover and the vertical component of pressure from the wind flow in kg;
- S is the cross-sectional size in cm 2;
- W z and M z are the moment of resistance and the value of the bending moment of the rafter beam, respectively;
- M y is a reference value for the bending force of a particular wood species of a beam.
For your information! When the angle of inclination is less than 27 °, the value of the wind load on the frame of the hip hip roof can be neglected, but the component from the snow and the additional weight of the lathing increases.
All strength calculations are carried out on the assumption that the timber used for the rafters of the hip roof is free from defects and damage, which in practice is not always true. In addition, boards from different parts of the tree trunk have different strength, therefore, the rafters for a hipped hip roof are made composite, in the form of a package of knocked down two or three boards 50x150 mm. Calculations of such a rafter according to the standard scheme.
Calculation of the geometry of the elements of a hip hip roof
The structure of a hip hip roof can be represented as a spatial set of rectangles and trapezoids.
The initial values are the dimensions of the Mauerlat rectangle, according to which all elements of the hipped roof frame will be calculated.
Initially, you need to calculate the height of the vertical support posts. For this, a value equal to half the length of the side wall, minus ½ the wall thickness of the house S, is used. Knowing the angle of inclination of the overhang A, we can easily determine the height of the vertical support of the ridge bar by the formula: H k = 0.5 (L bc - 0.5S) * tgА.
Having accepted the fact that L oq = L do, we can define:
- The length of the horizontal projection of the angular rafter beam according to the planimetry formula L oc = 1.22 * L do and, accordingly, the size of the diagonal rafter L ac, using the Pythagorean theorem and the legs L oc and H k;
- The length of the ridge girder, as the longitudinal dimension of the building box, minus the doubled length L do, L ak = L cm -2L do.
In addition to the actual dimensions of the frame, it is necessary to calculate the places of sawing down the ordinary and diagonal rafter beams.
To do this, along the lower edge of the board of an ordinary rafter, the size H ad obtained by the calculation is laid, after which the width of the Mauerlat is laid off at the angle of inclination of the slope and a wedge-shaped gash is performed, as in the figure.
Conclusion
For competent operation, certain knowledge is required in structural mechanics and strength materials, especially in matters of strength and stability of structures. However, for simple schemes, for example, for a gazebo or a shed, strength problems are not so critical. It is enough to know the rules for the geometric calculation of a hip-type hipped roof, and for the most important supporting and rafter elements, use a bar with an increased margin of safety.
Hip roofs are becoming increasingly popular among private house owners. This is not surprising, since such a scheme will differ in a number of indisputable advantages of the operational property, and in addition, it looks very original, giving the house a special aesthetics.
Some DIY homeowners may be intimidated by the fact that the hip roof truss system looks too complex. Yes, it is certainly not as simple as or a conventional gable roof. Nevertheless, this rafter system is completely subject to the laws of geometry, and it is quite possible to make a preliminary calculation of it. Installation, of course, will require some experience in carpentry work, but with good helpers, and even better - with a qualified consultant, you can take on this large-scale event.
What are the advantages of a hip roof?
A fairly popular type of roof is. This variety is referred to as four-slope structures.
For slate, a calculation example is as follows:
- Usually, seven sheets of wave slate are used for covering, the useful area of which is 1.335 m 2.
- If 8 sheets of such material are used, then the value of the useful area is 1.56 m 2.
- Further, the value of the total roof area is divided by the value of the usable area of the material. If the roof area is, for example, 26.7 m 2, then the number of slate sheets required for roofing equipment is 20 pieces.
Calculation example for metal tiles:
- When choosing a similar material for coating, it is worth knowing that the smaller the size of the material, the larger the size of the joints must be used.
- Initially, the total area is multiplied by a correction factor of 1.1.
- After that, the resulting area value is divided by the useful area of the tile, depending on its size and, accordingly, the size of the overlap.
If the structure of the roof covering is combined and complex, then the value of the overrun can reach 60%.
Roof calculator
Rafter step
The value of the distance that forms between the two rafters is called the pitch. Most of the structures are made in such a way that the step is 1 m... The minimum permissible value of such a parameter is also set, equal to 60 cm.
The process of calculating the distance between the rafters is as follows:
- Initially, you need to choose an approximate estimated step of the rafter system. You can build on the above values, i.e. the distance is 1 m.
- The next value you need is the length of the ridge (slope).
- After that, the length of the rafter is divided by the roughly selected step value. The result is rounded up to a higher value and then increased by 1.
- The latter in the calculation is the division of the total length of the slope by the value from the previous paragraph. This will be the required distance that must be observed during the installation process.
For example, you can consider the construction, the length of the slope of which is 12 m, and the approximate chosen step distance is 0.8 m:
- 12 / 0.8 = 15. If the number in the calculation turned out to be non-integer, then it should be rounded to the nearest integer value.
- 15 + 1 = 16. Increase per unit for more accurate calculations of the number of legs in the structure.
- 12/16 = 0.75 m. This value will be the optimal step distance for the rafter structure.
Rafter step
Choosing the angle of the roof slope and determining the height of the ridge
As in the previous calculations, the process of determining the height of the ridge depends on the chosen angle of the slope... Despite the fact that the hip roof structure allows you to build ramps with different angles, it is best to make a structure with the same angles.
This will allow the load to be distributed evenly and to give the roof an aesthetic appearance.
ATTENTION!
The angle of inclination relative to the hip type of the design varies between 20 and 45 degrees.
A more specific definition of such a parameter is influenced by:
- The increased snow load factor implies the construction of a structure with a steeper slope.
- If the wind in the area where the house is located is strong and gusty, then it is recommended to make the slope no more than 30 degrees.
- The intention is to use the attic as a living space. In this case, the convenience of movement in the attic is taken into account and the ability to provide all communication structures in such a way that they have free access if necessary.
- The coating chosen for the roof also plays an important role. When choosing a certain material, you need to inquire about the minimum allowed characteristics in relation to the slope angle.
Regarding the height of the ridge, it is very simple to determine it, knowing the value of the slope angle. In the construction, it is necessary to conditionally select a right-angled triangle, in which one of the sides will be the desired height.
Formula: h = b / 2 * tanA.
Roof angle
Conclusion
The stage of designing a house and all the elements of its construction is quite complex and painstaking. It is very important to carefully carry out all calculations and recheck them each time. This task can be facilitated by a visual representation on a smaller scale of the entire future structure.
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