Construction of a frame for a roof with four slopes is a complex process with characteristic technological features. During construction, our own structural components are used, the sequence of work is different. But the result will amaze with its spectacular shape and durability when repelling atmospheric attacks. And the home master will be able to be proud of his personal achievements in the field of roofing. However, before deciding on a device of such a design, it is worth familiarizing yourself with the algorithm according to which it is built rafter system hipped roof and the specifics of its structure.
Class of four pitched roofs combines two types of structures that resemble a square and rectangular envelope in plan. The first variety is called tent, the second - hip. Compared to their pitched counterparts, they are distinguished by the absence of pediments, called gables in the roofing industry. In the construction of both versions of hipped structures, layered and hanging rafters are used, the installation of which is carried out in accordance with standard technologies for the construction of pitched rafter systems.
Characteristic differences within the four-slope class:
- In a hip roof, all four slopes have the shape of isosceles triangles, the vertices of which converge at one highest point. There is no ridge as such in a tent structure; its function is performed by the central support in layered systems or the top of a hanging truss.
- For a hip roof, a pair of main slopes has a trapezoidal configuration, and the second pair has a triangular configuration. The hip structure differs from its tent-type counterpart in the obligatory presence of a ridge, to which the trapezoids are adjacent at the upper bases. Triangular slopes, also known as hips, are adjacent to the ridge at the top, and their sides are connected to the inclined sides of the trapezoids.
Based on the configuration of the roofs in plan, it is clear that hipped structures are usually erected over square buildings, and hip structures over rectangular houses. Both soft and hard roofing materials are suitable for covering. The characteristic square or rectangular shape is repeated in the drawings of the rafter system of a hipped roof with a clearly marked arrangement of elements in the plan and vertical projections of the slopes.
Often, hip and hip systems are used together in the construction of one building or effectively complement gable, lean-to, sloping and other roofs.
Structures with four slopes can rest directly on the upper crown of a wooden house or on the Mauerlat, which serves as the top frame of brick or concrete walls. If upper and lower supports can be found for each rafter, the roof frame is constructed using layered technology.
Installation of layered rafter legs is simpler and more accessible for an inexperienced home roofer, who needs to take into account that:
- When rigidly fastening the upper and lower heels of the rafters with metal corners or using a supporting wooden plate, reinforced fastening of the Mauerlat will be required, because the thrust will be transferred to it.
- If the upper heel is rigidly fixed and the bottom of the rafter is hinged, there is no need to strengthen the fastening of the Mauerlate, because if the load on the roof is exceeded, a hinged fastening, for example on sliders, will allow the rafter to move slightly without creating pressure on the mauerlat.
- When the top of the rafters is hinged and the bottom is rigidly fixed, expansion and pressure on the Mauerlat are also eliminated.
Issues of fastening the Mauerlat and the closely related method of installing rafter legs according to the rules are resolved at the stage of designing a house. If the building does not have an internal load-bearing wall or it is not possible to build reliable supports for the central part of the roof, nothing will work other than a hanging rafter system assembly scheme. True, in most cases the layered construction method is used, for the implementation of which it is necessary to provide in advance a load-bearing support inside the structure.
In the construction of rafter systems for hipped and hipped roofs, specific structural elements are used, these are:
- Diagonal rafter legs forming the spinal connections of the slopes. In hip structures, diagonals, also known as slanted rafters, connect the ridge girder consoles to the corners of the roof. In tent systems, sloping legs connect the top to the corners.
- Spreaders, or rafter half-legs, installed perpendicular to the eaves. They rest on diagonal rafters and are located parallel to each other, therefore they differ in different lengths. Narozhniki form the planes of tent and hip slopes.
Diagonal rafters and flanges are also used for the construction of valleys, only then concave corners of the roof are arranged, and not convex ones like hip ones.
The whole difficulty of constructing frames for roofs with four slopes lies in the installation of diagonal rafters, which determine the result of the formation of the structure. In addition, the slopes must withstand a load one and a half times greater than ordinary rafters of pitched roofs. Because they also work as a hobbyhorse, i.e. support for the upper heel of the runners.
If we briefly describe the procedure for constructing a layered frame for a hipped roof, then it can be done in several stages:
- Construction of a mauerlat on brick or concrete walls. The process of installing a mauerlat on walls made of logs or timber can be eliminated, because it can be successfully replaced by the upper crown.
- Installation of the central support for the hip structure or the supporting frame of the main part of the hip roof.
- Installation of conventional layered rafters: pairs for a hip roof and a row determined by the design solution for hip design.
- Installation of diagonal rafter legs connecting the corners of the systems with the top of the support or the extreme points of the ridge.
- Manufacturing to size and fastening of spigots.
In the case of using a hanging frame scheme, the start of the construction of the tent frame will be the installation of a triangular truss in the center. The installation of a four-slope hip rafter system will begin with the installation of a number of roof trusses.
Construction of a hip rafter system
Let's look at one of the common examples of a hip roof with layered rafter legs. They will have to rely on floor beams laid on top of the mauerlat. Rigid fastening with a notch will be used only to fix the top of the rafter legs on the ridge girder, so there is no need to strengthen the Mauerlat fasteners. The dimensions of the box of the house shown in the example are 8.4 × 10.8 m. The actual dimensions of the roof in plan will increase on each side by the amount of the eaves overhang, by 40-50cm.
Installation of the base according to the Mauerlat
Mauerlat is a purely individual element; the method of its installation depends on the material of the walls and the architectural features of the building. The method of laying the Mauerlat is planned according to the rules during the design period, because for reliable fixation of the Mauerlat it is recommended:
- Lightweight foam concrete, gas silicate and similar walls should be equipped with a reinforced reinforced concrete belt, poured around the perimeter, with anchors installed during the pouring period to secure the Mauerlat.
- Edge the brick walls with a side of one or two bricks along the outer edge so that a ledge is formed along the inner edge for laying a wooden frame. During laying, wooden plugs are placed between the bricks to secure the Mauerlat with staples to the wall.
The mauerlat is made from timber measuring 150×150 or 100×150mm. If you intend to use the under-roof space, it is advisable to take thicker beams. The timber is connected into a single frame with oblique cuts. Then the connection areas are reinforced with self-tapping screws, ordinary nails or wood grouse, and the corners are reinforced with staples.
Floor beams are laid on top of the horizontally leveled mauerlat, constructed in the optimal way for a particular building. A beam with a cross section of 100×200mm is used. The first step is to lay a beam running exactly along the central axis of the building. In the example, the length of the timber is not enough to construct solid beams, so they are assembled from two beams. The connection point should be located above reliable support. In the example, the support is an internal load-bearing wall.
The pitch between the floor beams is 60 cm. If the box being equipped does not have ideal parameters, as is the case in most situations, the distance between the beams can be changed slightly. Such an adjustment allows you to slightly “smooth out” the flaws in construction. Between the outer beams on both sides and the walls of the house there should be a gap of 90 cm wide, necessary for installing the outriggers.
Because the floor beams can independently form only two eaves overhangs; short half-beams of the floor - extensions - are attached to their ends. They are first installed only in the area of the main part of the hip roof, exactly where the rafter legs are to be installed. The extension is nailed to the mauerlat, fastened to the beam with screws, large-caliber nails, dowels, and the fasteners are reinforced with corners.
Construction of the ridge part
The central part of the hip roof is an ordinary gable structure. The rafter system for it is arranged according to the rules dictated by the technology for constructing pitched roofs. In the example there are some deviations from the classical interpretation of the pitched principle: the bed on which supports for the ridge run are traditionally installed is not used. The work of the beam will have to be done by the central floor beam.
In order to build the ridge part of the hip roof rafter system you need to:
- Build a support frame for the rafter legs, the top of which will rest on the ridge girder. The purlin will rest on three supports, the central one of which is installed directly on the central floor beam. To install the two outer supports, first two cross beams are laid, covering at least five floor beams. Stability is increased with the help of two struts. For the manufacture of horizontal and vertical parts of the supporting frame, a block with a cross-section of 100x150mm was used, the struts were made of boards 50x150mm.
- Make rafter legs, for which you first need to make a template. A board of suitable size is applied to the installation site, and lines for future cuts are drawn on it. This will be the template for the continuous production of rafters.
- Install the rafter legs, resting them with the notch on the ridge girder, and with the lower heel on the stem located opposite.
If the floor beams were laid across the frame, then the rafters of the main part of the roof would rest on the floor beams, which is much more reliable. However, in the example they rest on the stem, so it is necessary to arrange additional mini-supports for them. These supports should be positioned so that the load from them and the rafters located above is transferred to the walls.
Then three rows of outriggers are installed on each of the four sides. For the convenience of further actions, the roof contour is formed with a cornice board. It must be nailed to the floor beams and extensions strictly horizontally.
Installation of corner extensions
In the space limited by the eaves board, there were corner areas left unfilled with parts of the rafter system. Here you will need corner offsets, for installation of which is carried out as follows:
- To indicate the direction of installation, pull the string. We stretch from the point of conditional intersection of the outer support of the frame with the floor beam to the corner.
- On top of the lace we place the block in its place. Holding the block, we draw cut lines from below where the block intersects the floor beam and the corner connection of the eaves boards.
- We attach the finished stem with sawn off excess to the mauerlat and to the floor beam with corners.
The remaining three corner extensions are manufactured and installed in the same way.
Installation of diagonal rafters
Diagonal, or also slanted, rafter legs are made from two boards sewn together with a cross-section equal to the size of ordinary rafters. In the example, one of the boards will be located slightly higher than the second due to the difference in the angles of inclination of the hips and trapezoidal slopes.
Sequence of work for the manufacture and installation of slopes:
- From the highest point of the skate, we stretch the lace to the corners and to the central point of the slope. These are auxiliary lines along which we will mark upcoming cuts.
- Using a carpenter's goniometer, we measure the angle between the lace and the upper side of the corner stem. This is how the angle of the bottom cut is determined. Let's assume it is equal to α. The angle of the upper cut is calculated using the formula β = 90º - α.
- At an angle β we cut off one edge of a random piece of board. We apply it to the place of the upper fastening, aligning the edge of this workpiece with the lace. We outline the excesses that interfere with a tight installation. You need to cut again along the marked lines.
- At an angle α we saw off the lower heel on another piece of board.
- We make the first half of the diagonal rafter using templates for the upper and lower support. If a solid board is not long enough, you can join two pieces together. They can be spliced using a meter-long piece of inch mounted on self-tapping screws; it should be placed with outside constructed oblique leg. We install the finished first part.
- We make the second part of the sloped rafter in the same way, but keep in mind that it should be slightly lower than its first half. The area where the boards are joined into one element should not coincide with the area where the boards are joined in the first half of the slope.
- We sew two boards with nails at intervals of 40-50 cm.
- Along the cord stretched to the center of the slope, we draw a line along which it will be necessary to adjust the cut to connect it with the adjacent rafter.
Following the described algorithm, you need to install three more diagonal legs. Supports should be installed under each of them at the point where the corner extensions are connected to the beams. If the span is more than 7.5 m, another support is installed diagonally closer to the ridge.
Manufacturing and installation of hip rafters
The lace between the top of the skate and the center of the slope is already stretched. It served as an axis for outlining cuts, and now you need to measure the angle γ using it and calculate the angle δ = 90º - γ. Without deviating from the proven path, we prepare templates for the upper and lower supports. We apply the top trim to the place intended for it and mark the cut lines on it for a tight fit between the diagonal rafters. Using the blanks, we make the central leg of the hip and fix it where it should be.
We install short extensions in the space between the corner extensions and the cornice board to add rigidity to the structure and to ensure strong fixation of the outermost, shortest extensions. Next, you should start making templates for the makers themselves:
- We cut the piece of board at an angle δ and attach it to the place of attachment to the diagonal rafter.
- We outline the excess that needs to be cut down again. The resulting template is used in the manufacture of all flaps, for example the right side of the hip. For the left part, the upper template will be filed from the opposite side.
- As a template for the lower heel of the splices, we use a piece of board sawn off at an angle γ. If all previous steps were performed correctly, then this template is used to make the lower attachment points for all other springs.
In accordance with the actual length and “indications” of the templates, the splices are made, which are necessary for forming the planes of the hips and the parts of the main slopes that are not filled with ordinary rafter legs. They are installed so that the upper fastening points of the spigots to the diagonal rafters are spaced apart, i.e. the upper connecting nodes of adjacent slopes should not converge in one place. The splices are attached to the slanted rafter leg with corners, to the floor beams and outriggers in the way that is more reasonable and convenient: with corners or metal toothed plates.
The technology for installing a hip roof is based on the already familiar hip principles. True, there is no ridge part of the rafter system in their design. The construction begins with the installation of a central support, to which the rafters are attached, and then the frames. If hanging technology is used in the construction of an envelope roof, then the finished truss is installed first.
We invite you to take advantage of our free online calculator for calculations of building materials when installing a hip roof - go here and follow the instructions.
Useful video instructions
The video will briefly introduce the sequence and rules for installing the rafter system of a hipped roof of the hip and hip categories:
Having become familiar with the specifics of the device and having mastered the intricacies of installing roofs with four slopes, you can safely begin to implement plans for its construction.
The rafter system is a combination of all the supporting elements that form the frame on which the roofing cake rests. The ability of the roof to withstand wind and snow loads and to protect interior spaces from water and cold. In order not to resort to expensive services of companies performing roofing professionally, we will tell you what the rafter system of a hipped roof consists of, what materials are required for its manufacture and how to assemble it.
Types of hipped roofs
The name “hippable” combines several types of roofs, consisting of four planes, slopes:
Despite the external differences, the rafter systems of a hipped roof are made up of the same elements, guided by the same rules.
Types of rafter systems
The rafter system of a hipped roof takes on a different appearance, depending on the initial conditions: the area of the house being covered and internal layout. There are three types:
What type of rafter system is suitable for a particular house is determined during the design period, making calculations and drawing up drawings.
Calculation of the slope of the slopes and the height of the ridge
The design of the rafter system for a hipped roof begins with calculations that determine the geometry of the future structure:
The process of designing a rafter system for a hipped roof can be facilitated by special computer calculator programs that only require entering the initial data: the size of the house, the number of slopes.
Load calculation
The next stage of design is determining the composition of the elements of the rafter system and their cross-section. To do this, calculate the loads to which the hipped structure is subjected. They are divided into three types:
By summing the values of all loads, the total load is determined, which, depending on the type used roofing material can reach 180-250 kg per square meter. Based on this figure, the number of elements of the rafter system and their cross-section are determined by checking the reference table. It is more convenient to calculate more complex systems in special programs, the result of which is ready-made diagram hip roof truss system.
Essential elements
The rafter system of a hipped roof consists of many components, mandatory and auxiliary:
- Mauerlat. A beam with a cross section of 100x100 mm or 150x150 mm, which evenly distributes the load along the perimeter of the load-bearing walls. The difference between a hipped roof is that its installation requires four Mauerlats, and not two, as for a gable roof.
- Sill. A beam that serves as a support for racks, which is used in a layered rafter system. It, like the Mauerlat, distributes the weight of the roof, but is located on the internal load-bearing wall.
- Rafter legs. Elements made of boards with a section of 50x150 mm or 100x150 mm, which carry the roofing cake and set the geometry of the slopes. In the construction of hipped roofs, ordinary, layered and outer rafters are used. The rows are arranged in pairs along the ridge run, forming trapezoidal slopes. The slopes, diverging from the ridge to the two corners of the house, form triangular end slopes. And the outer rafters rest top part on layers and have different lengths.
- Ridge run. A beam supported by vertical posts to which the rafters are attached. This is the highest point of the roof.
- Racks. Vertical supports that are installed on a bench. They support the ridge purlin or the middle of the rafter leg.
- Struts. Bars that are installed at an angle to the rafter legs to prevent them from bending.
- Tightening and bolt. Horizontal lintels made of wood or metal connecting pairs of rafter legs, reducing the bursting load on the walls. The crossbar is installed at the top of the rafters, tightened at the bottom, often used as floor beams.
- Sprengel farms. Sprengel is a vertical riser for sloped rafters. If there is nothing to rest it on, install a tie between two adjacent sides of the house and attach the truss using metal corners.
- Lathing. Base for laying roofing material. If the boards are nailed without gaps, the sheathing structure is called continuous. And if the boards are alternated with a small gap - lattice. The sheathing pattern depends on the type of roofing material.
- Eaves. The part of the rafters that protrudes 40-50 cm beyond the perimeter of the house, protecting it from moisture.
Assembling the rafter system
Having a drawing of the rafter system in hand, you can begin assembly work. Since the material used is mainly natural wood, it would not be superfluous to treat it with a deep penetration antiseptic to protect it from moisture and bacteria. Roofers pay attention to a number of features that should be taken into account when installing a hip roof truss system:
A well-designed and high-quality assembled rafter system is the basis for the long-term operation of a hipped roof, which will provide reliable protection from the weather, regardless of whether it is hip or hip!
Video instruction
Pitched roofs are quite popular in private suburban construction, and therefore many people are of great interest in the rafter system of a hipped roof, which has some design features.
This type of roof is the preferred option both for a country cottage and for a gazebo built on the adjacent territory.
It should be noted that the hipped roof gives the building a rather attractive appearance, and also allows for additional attic room large area.
The rafter system of a hipped roof has a complex structure and its installation should be carried out only according to a preliminary calculation, the result of which should be a diagram.
The calculation of such a roof, both for a house and for a gazebo, can be done with your own hands if you use a special program developed specifically for these purposes.
Its rafter system allows several various options. Hip roofs include half-hip roofs and hip roofs, and each of them has its own specific features and differences.
Some types of these types of rafter systems, the installation of which you can do yourself, are presented in the photo below.
Features and types of hipped roofing
The structure and design of the rafter system for a hipped roof type primarily depends on the configuration.
Currently, the most common are hip, hip, and half-hip rafter system structures, which can be used both for a private house and for a gazebo.
Each of them has both advantages and disadvantages.
In any case, the rafter system of a hipped roof requires a calculation that is made depending on the type chosen.
The hip type of rafter system is quite popular in private construction. Its design is quite resistant to various external influences and involves the construction and installation of trapezoidal-type slopes.
As a rule, its installation is carried out using several separate rafters that extend from the two upper points. This type of rafter system can also be used to build a gazebo.
Hip roof options can be seen in the photo below.
Also quite common is a half-hip roof, the design of which vaguely resembles a gable roof.
The advantage of this type of rafter system is the ability to install a vertical window in the upper attic area.
Its design assumes the absence of a sharp protrusion, which allows it to withstand fairly strong wind loads.
In addition, in some cases, the half-hip rafter system makes it possible to equip full glazing of the upper space.
A hipped roof also belongs to the hipped roof, but for its arrangement it is necessary that the structure near the walls of the building be made in the shape of a square.
The construction of this type of roof implies, due to a certain design of the slopes, the formation of a triangle with equal sides. Very often, a hip roof is installed on gazebos.
Any type of this type of rafter system requires an exact calculation, on the basis of which the installation is carried out with your own hands.
Design Features
A hip roof, regardless of its type, must have a frame, the design of which requires the presence of a fairly large number of different elements.
Each of them has a specific purpose and must meet its functional requirements.
In order for such a roof to withstand all possible loads during its operation, it is necessary to accurately calculate the capabilities of each of its constituent elements.
Such a calculation is quite complex calculations that cannot always be done by hand.
It is best to entrust the calculation of a hipped roof to qualified specialists who have professional training.
You can do the calculation yourself, but you will have to use a special program to do this.
It is easiest to make such a calculation for a gazebo, since its design has a simpler shape and involves the use of fewer elements.
When calculating the roof frame, it is important to avoid critical errors, as this can lead to serious consequences during its subsequent operation.
If mistakes are made, correcting them can lead to serious financial investments and an increase in the cost of the entire construction.
First of all, when calculating the roof frame, it is important to determine the angle of inclination of its slopes. Calculations show that the higher the angle of inclination, the more building materials will be required.
Also, when calculating the roof, you should definitely take into account the fact that the lower its angle of inclination, the more powerful the structure of the frame itself should be.
Correctly made calculations will make the rafter system better and more powerful.
A semi-hip, hip or hip roof of the hipped type is shown in the photo above.
Types and features of rafter systems
The design of any type of hip roof frame can differ not only in the bay window, but also in the presence of certain components.
Thus, its installation involves the arrangement of a mauerlat, purlin, and also a support board. In addition, the roof frame must include tie rods, extensions, and the rafters themselves.
Installation of a hipped roof requires the installation of sheathing, as well as some other required elements.
A little simpler frame the roof of the gazebo and this is connected, first of all, with its design features. The installation of a hipped roof is shown in the video below.
In any case, in order to install the roof frame of a house or gazebo, it is necessary to develop a plan for the rafter system and this should be done as accurately as possible.
Both a half-hip roof and any other hipped roof consists directly of a frame and the rafter system itself, on which the roofing pie will subsequently rest.
An important point when arranging this type of roof with your own hands is the uniform distribution of the expected load over the entire surface of its structure and then onto the walls and directly onto the foundation of the building.
This can be achieved not only by the correct design of the roof frame, but also by its installation. For this, rafter systems of various types can be used.
Their choice mainly depends on the size of the house being built. In addition, the presence of load-bearing internal walls or additional supports is taken into account.
In any case, the installation of the roof can be carried out using hanging or layered rafters, which is described in detail in the video below.
Structures of truss systems
Hanging type rafter systems are often used. This type of construction involves the arrangement of two independent supports, which do not imply any intermediate support.
Such rafter systems work in both bending and compression. Also hanging type the design of the rafter system creates a horizontal force, which is accordingly transmitted to all load-bearing walls.
Reduce this type loads are possible through the use of special puffs, which are jumpers made of wood or metal that connect all the wooden legs.
When constructing an attic or attic roof, such tie-downs are installed at the base of the legs. If such a tie is attached above the base of the rafters, then its main function is only securing.
It should be noted that the higher such a tightening is installed, the more durable all the constituent elements of the rafter structure should be.
In those buildings in which a load-bearing middle wall is provided, or special supports are additionally installed, as a rule, a rafter system is installed, which provides for the arrangement of layered rafters.
Such layered rafters with their lower parts rest directly on the mauerlat, which must be laid over the entire surface of the external walls of the house. In addition, such a rafter system middle part additionally strengthened in the middle part of the house.
The design of the layered rafter system works in bending and has less weight than hanging rafters, which means that less building materials are used for its construction.
In addition, the rafter system, which is made using layered rafters, has higher strength and, accordingly, rigidity.
Some installation features
Any hipped roof, even if the device is designed for a gazebo, requires a complex structure, despite the fact that they can be equipped with a bay window of various shapes.
At the base of these types of roofs is a triangle, which determines their high rigidity and stability.
The main elements of such a roof, which bear the main load, are rafter legs, the design and installation of which should be given Special attention.
When installing such a roof with your own hands, it is recommended to follow the rules and construction technology with maximum precision.
In addition, you should use only high-quality Construction Materials, possessing the necessary strength and reliability.
When constructing a hipped roof, special attention should be paid to all its corner elements, which experience the maximum amount of loads.
If it is necessary to splice some frame elements, they should be additionally reinforced with appropriate racks and struts, which make it possible to reduce the overall load.
In general, a hipped roof is a complex constructively element of the house that must be completed in accordance with all requirements.
A roof made of four slopes - what is it good for? The numerous operational advantages of this type certainly outweigh the disadvantages. Is the rafter system of a hipped roof as simple as many construction beginners think? You will definitely find out soon! We will describe important nuances and features of the stages of erecting a hip roof in this article.
What do you need to know about hip truss systems?
There are two options for hip roofs: hip and hip. The first type has the shape of a rectangular envelope, consisting of two main trapezoidal slopes and a ridge, and two pediment (side) slopes - triangles:
A hip roof is four identical isosceles triangles connected at one top point (reminiscent of a tent):
Both options provide for installation of both layered and hanging rafters, which are installed using standard technologies.
How to choose the type of rafter system for a 4-pitched roof?
In the absence of a central roof support, the choice is made in favor of a hanging rafter system. If you can find upper and lower supports for each rafter, then you should choose a layered structure. This option is simpler and more accessible for non-professional craftsmen. You just need to remember two main conditions: when rigidly fastening the bottom and top of the stops, a reinforced Mauerlat is needed, since the thrust is transferred to it; with a hinged fastening or a semi-rigid connection (for example, the top is hinged and the bottom is rigid or vice versa), the Mauerlat does not need to be reinforced:
The choice of one type of hip roof should be determined by the shape of the house itself. For square houses, hip rafters are erected, for rectangular ones - hip rafters. Also, you can find complex multi-pitched roofs of a combined type, which contain both hip and hip elements.
Both hip and hipped structures retain the basic functions of a gable roof (for example, the possibility of arranging an attic) and look very aesthetically pleasing:
Why is a hipped roof more popular than a gable roof?
“Why the extra headache and difficulties?”, you ask: “After all, you can build a simple gable roof much faster and cheaper.” Here the masters emphasize some important points in favor of choosing exactly four slopes for the roof:
- High wind resistance. The hipped roof has no gables; all its planes are inclined towards the ridge. This structure minimizes the impact of strong winds and reduces possible destructive consequences to “0”.
- The most successful load distribution. A multi-pitched roof can withstand the maximum amount of precipitation, since the gentle slopes take part of the main load. Therefore, sagging, deformation and destruction of the rafter system, in this case, have a minimal probability.
- Availability of choice of any method of roof insulation. Straight gables require a special approach when choosing the type of roof insulation, since they are located vertically and are subject to wind blowing. The gentle slopes of hip and hip systems make it possible to evenly insulate the roof with any available material.
In addition to the listed “advantages”, a roof with four slopes perfectly conserves heat, can be covered with any roofing material and always has a neat appearance.
Construction of a four-slope rafter system
The four-slope rafter structure consists of the following elements: mauerlat, ridge beam, central and hip rafters, slanted legs, as well as beds, racks, crossbars, struts and other reinforcing parts. Let's look at the most basic elements.
I. Mauerlat
The Mauerlat is the most important part of the structure, since the entire rafter system rests on it. It is a powerful wooden beam 100x200, 100x250, 100x100, 150x250, 200x200 cm. The mauerlat is made from solid quality wood, mainly, coniferous species. The rafter system of a hip roof, like any multi-pitched roof, requires thorough fastening of the base beam. The procedure for installing the Mauerlat in this case: the formation of a monolithic foundation at the end of the load-bearing walls with the installation of spiers; laying waterproofing; processing and installation of Mauerlat around the perimeter of the entire house; reinforced with anchors and other fastenings for maximum reliability of the base.
The Mauerlat can be laid on the edge of the wall, or in a pocket provided for laying bricks with inside load-bearing walls.
II. Sloping legs
Sloping legs are the four corner rafters that rest on the edges of the ridge and the corners of the mauerlat. They are the longest among all the rafter legs of the system, therefore they must have a cross-section of at least 100x150 mm for maximum rigidity.
III. Ridge beam
Ridge purlin is a horizontal beam that connects all the rafters, the top of the rafter system. The beam must be strengthened with racks and struts. The ridge must be positioned strictly parallel to the plane attic floor and perpendicular to the posts.
IV. Rafters
Rafters for a hipped roof are divided into: central (attached to the mauerlat and ridge); main hip ones (attached to the ridge axis and Mauerlat); intermediate and shortened (installed on sloping legs and Mauerlat, connecting the corners of the slopes).
V. Strengthening elements
Additional reinforcing elements include ridge beam posts, crossbars or floor beams, rafter struts, wind beams, etc.
DIY rafter system for a hipped roof
Let's consider step by step process construction of the truss structure. For clarity, we have chosen the most popular option - hip roofing. The hip roof rafter system, a diagram of which step by step, is presented to your attention below:
Step I: Create a Project
To depict your version of a hip roof in a drawing, you need to calculate the height, length, slopes of the slopes and roof area. This is necessary for clear and quality implementation project and selection of the required amount of consumables:
Calculations should begin by choosing the angle of the roof slopes. The optimal slope is considered to be an angle of 20-450. The magnitude of the slope must correspond to the climatic characteristics of the region. So, in particularly windy areas, the slope should be kept to a minimum, and for areas where there is frequent and heavy rainfall, the steepest slope angle is necessary. In addition to the weather environment, you also need to consider the roofing material you plan to use. For a soft roof the degree of inclination should be less, for a hard roof it should be greater.
And one more small but important nuance on this issue - it is better to make the slope angle the same for all four slopes. So the load will be distributed evenly, and the structure will be as stable as possible, and the aesthetic appeal will remain “at its best.”
Now, knowing the angle of inclination and the width of the house, we can use simple mathematics to calculate the height of the ridge, the length of the rafter legs, racks and other details of the rafter system. When calculating the length of the rafters, do not forget to take into account the eaves overhang (as a rule, its length is 40-50 cm).
The roof area for purchasing the required amount of roofing material is calculated as the sum of the areas of all slopes of the structure.
How to draw a roof drawing correctly?
- We select the scale of the drawing and transfer the dimensions of the house in scale onto a sheet of paper;
- Next, we transfer the selected dimensions of our roof onto the diagram: the height of the ridge, its length, the number and size of rafter legs, struts, racks and all the details, in accordance with the calculations made earlier;
- Now you can count all the necessary materials and start searching for them.
Step II: Preparing for work
To erect a roof frame, you will need standard tools and equipment: drills, screwdrivers, jigsaws, hammers, chisels, etc. We already know the required amount of materials for the rafter system, so we can purchase them. The lumber for the frame must be solid, have no cracks, wormholes, have a light shade, without gray or yellow patina, and smell like fresh wood. Wet wood should not be laid on the roof immediately; it must be dried, treated with an antiseptic solution and dried again. Wood humidity should not exceed 20%.
Step III: Mounting the Mauerlat
Mauerlat – basic part the entire rafter system. It transfers thrust loads to the load-bearing walls of the house. Installing a Mauerlat for a hipped roof is no different from similar structures with two or one slope. This process is described in as much detail as possible in our previous articles.
The base beam, the parameters of which are described above, is placed on an armored belt and high-quality waterproofing. If it is necessary to connect the Mauerlat, then the bars are cut into half the section and overlapped using strong fasteners.
Step IV: Laying the floor beams or beams
If there are load-bearing walls inside the house, then it is necessary to install beams on their ends - the basis for support posts roofing system. If load-bearing floors is no longer in the house, then the attic floor is covered with reinforced beams, on which roof supports are subsequently installed, and then the attic floor pie is laid.
Beams must have a cross-section of at least 100x200 mm. The step between them is 60 cm. You can slightly adjust this figure, depending on the characteristics of your home. The distance between the outer beams and the mauerlat should not be less than 90 cm. This distance is used for installing the half-beams of the eaves overhang (extension). The stems are attached to the two outer beams using strong anchors and reinforced metal corners.
Step V: Installation of support posts, purlins and ridge
Racks are an important part for supporting the structure; they redistribute the weight of the rafter system onto the beams or floor beams. The racks are installed strictly perpendicular to the plane of the bed. IN hipped systems the supports are installed under the ridge beam (hip roof) or under the corner rafters (hip roof):
The racks must be securely attached to the base using metal plates and reinforced corners. The purlins are installed as additional support for the racks. In a hip roof, the purlins are rectangular in shape, while for the hips they are ordinary ridge purlins.
After we have made sure that the supports are installed correctly (using a meter and a level), we can attach the upper ridge beam. It is mounted on vertical posts and reinforced with reliable metal fasteners (plates, corners, anchors and screws). Now let's take on the corner extensions:
Step VI: Installation of rafters
First, you need to install the side rafters, which rest on the ridge beam and the Mauerlat (or are secured with an extension). To do this, you need to make a template rafter with the appropriate cuts. We apply the rafter leg to the ridge, mark the place of the cut with a pencil, then mark the place of the cut of the rafters for joining with the Mauerlat and make cuts. Attach the rafter to the supports again to make sure that the connection is correct and to correct any imperfections. Now this sample can be used to make all the side rafters. Installation of the rafter legs of the main slopes is carried out according to general rules described in the design of a gable rafter system (see article and video).
Diagonal (corner) rafters are installed next. Their upper edge is installed on the stand and joins the edge of the ridge beam. Before this, measurements are taken and the corresponding cuts of the rafter legs are made. The lower end of the diagonals is fixed in the corners of the Mauerlat:
Since diagonal rafters are longer than all other legs, they require additional support. This function is performed by trusses - support beams that are installed under each diagonal leg, in its lower quarter (this is where the greatest load occurs). Sprengels, like ridge posts, are installed on supporting corner beams located in the plane of the floor beams.
The space between the corner ribs is filled with auxiliary rafter legs - sprigs. Their lower part rests on the mauerlat, and the upper part rests on the diagonal rafter leg. The step between the frames should be equal to the step between the side rafters (50-150 cm).
Step VII: Sheathing
All that remains is to complete The final stage formation of the roof skeleton - installation of sheathing. These are boards or bars 50x50 mm, which are attached to the rafters parallel to the ridge girder and the mauerlat. The pitch of the sheathing boards is 50-60 cm. This is quite enough for laying the roofing pie. When a soft roof is provided, the sheathing is laid in 2 layers (counter-lattice and sheathing).
Finally, a few videos:
So, we described the installation of the rafter system of a hipped roof, its basic principles, and even went a little deeper into some of the nuances. Hip and tent structures are, although not the simplest, but quite feasible options for every novice craftsman. Especially if he has good assistants. We wish you success in your work!
For large buildings, a gable roof does not provide the required protection and reliability. This design rests only on 2 external load-bearing walls, so the load on the rafters is excessively high. For big house it is better to choose a hip roof, which effectively withstands atmospheric loads and more evenly distributes pressure on the external load-bearing walls and foundation.
Hip roof configurations
The geometric design of such a roof combines 4 inclined planes, the bases of which are the load-bearing walls of the house along the perimeter. There are several configurations that determine the shape and relative position of inclined surfaces.
Hip roof
A simple design, in appearance it partly resembles a gable one: 2 planes are formed parallel to the long walls, which are connected in the center by a ridge ceiling. The opposite gables are replaced with inclined hip triangles. The design is used for large buildings, two sides of which are significantly longer than the other. 
Half hip roof
It differs in the configuration of the end slopes. The bases of the triangles rise above the bottom edge of the structure. The remaining space is filled by the pediment. The corners at the base of large slopes are cut vertically. This allows you to create a spacious attic under the roof and install double-glazed windows.
Suitable for square houses or buildings where all walls are approximately equal. The four slopes are triangles connected by their vertices at a common central point. Such structures do not have a horizontal ridge.
The construction of all hipped roofs is based on these configurations, including the combination of various elements into complex structures.
Many country gazebos have the shape of a regular polygon; they are often erected hip roof. Why a hip roof is used for a small structure is explained by the practicality and aesthetic completeness of such a design. It is impractical to build a roof with two inclined surfaces for a summerhouse: the absence of closed gables will leave part of the structure unprotected from precipitation, for example, during slanting rain. The hipped roof wins in this regard.
Types of rafter systems
There are hanging and layered designs. The first type is distinguished by the fact that the rafters lean against each other. This type is used for buildings that do not have central load-bearing walls. The load is bursting. To increase strength, they make ties between opposite rafters, use racks, struts and other devices.
The sloped design of the hipped roof includes additional supports for the rafters. They are strengthened under the ridge girder and transfer part of the load to the load-bearing walls inside the building.
Differences between systems: 1) Hanging 2) Layered
Description of the rafter structure
The construction of a hip roof requires professional knowledge and experience from the master. Drawings of a rafter system for a hipped roof of this type include the following elements:
- Mauerlat is the base of the frame, laid on load-bearing walls. Since all sides of the house are supporting, the element is attached along the perimeter of the building. Since hip roofs are built on large objects, the Mauerlat must be of high strength. Typically, timber 150×150 or 100×100 is used. Mauerlat is not required if the structure is made of wood. In this case, the base is the upper frame of the walls.
- The ridge girder is installed horizontally at the intersection of the trapezoidal slopes and serves as a connecting element.
- From each end of the purlin there are 3 supports called central rafters. They are erected regardless of the pitch of the other elements.
- Diagonal (corner) rafters connect the ridge beam to the corners of the building. These are the longest supports with the greatest slope.
- Parallel to the directions of the slopes, short rafters are erected on the hips, fastening the corner supports (sides of the triangles) to the Mauerlat.
- The lateral edges of the trapezoids are connected to the base with sprigs, and the two parallel sides– intermediate supports.
- Sprengel is used to increase strength. It is a block located closer to the corner of the building, the ends of which are installed on adjacent walls.
- When installing struts and racks, a truss truss is formed - an additional structural unit.
- Tightenings are used in a hanging rafter system. They are mounted on two opposite supports.
- In a layered structure there is a beam that is laid on a load-bearing wall in the center of the building and takes on part of the load.
The peculiarity of the half-hip roof is that the lower edge of each triangular slope rises to the height of the pediment, thereby shortening the diagonal rafters. The hipped hip roof is simpler. The frame design includes similar components of the hips and internal ligament. All reinforcement elements are designed for one purpose - to tighten the frame into knots and make it rigid.
System features and calculations
The roof with four slopes can withstand high wind and snow loads. In order for the roof to be practical, reliable and to perfectly perform the functions assigned to it, an accurate calculation of all elements is carried out. The slope of the hip roof slopes does not exceed 40°. The construction of a tent system requires an angle of 40 to 60°.
The calculation of the supporting structure is based on the mutual dependence of the span length, rafter pitch and beam cross-section. The second parameter is selected individually based on the available material and ease of fastening. In the longest structures, the rafter pitch is 2.15 m, and in most cases 90 cm is chosen.
The distance determines the cross-section of the supports. The further apart the rafters are placed, the thicker the board will be required. The size of the section also depends on the length of the supports themselves. The connection is directly proportional. To ensure that the rafters can withstand bending forces, choose a material with a larger cross-section. For 6-meter supports with a pitch of 90, the cross-sectional area is 75×200 mm, and for 3-meter supports it is only 50×150.
Carrying out construction activities
The material for the frame must be well dried. Wood moisture content is limited to 20%. Work order:
A professional approach to assembling a durable frame determines the performance qualities of a hipped roof. Resistance depends on the reliability of the design weather conditions and the service life of the structure as a whole.
In private housing construction, in addition to the common gable roofs, stronger and more rigid hipped structures are often used. They are distinguished by the absence of pediments, which replace triangular slopes that cut off the ends of the ridge ridge. This configuration makes hipped roofs very attractive and economical, even though their construction increases the length of the eaves overhangs and the number of drainpipes and gutters. Therefore, they deserve the closest attention.
Types of rafter systems for hipped roofs
The design of the rafter system depends on the shape of the hipped roof. The most common configurations today are:
- Hip structure. All four slopes occupy the area from the ridge to the eaves overhang, with two side slopes having a trapezoidal shape, and two end ones (hips) having a triangular shape. A special feature of the hip rafter frame is the presence of two pairs of diagonally layered rafters, which extend from the edge of the ridge and serve as supports for the trusses and trusses.
The hip hipped design is characterized by the fact that the slopes occupy the entire roof area - from the ridge to the eaves
- Dutch half hip. A device with truncated end slopes that do not reach the cornice. As a rule, they are 2–3 times smaller than trapezoidal ones. The advantage of this hipped roof structure is the possibility of installation at the ends of the house regular window, as well as the absence of a sharp projection typical of gable roofs, which greatly increases the wind resistance of the structure.
The Dutch half-hip roof has truncated triangular slopes and part of the pediment into which a regular vertical window can be installed
- Danish half hip. It is characterized by the presence of a pediment at the ridge in the triangular slopes, which allows for full daylight under-roof space without installing roof windows.
- Tent structure. Installed on houses with a square frame. All four slopes of the hipped roof are identical isosceles triangles connected at one point. When constructing such a roof, an important aspect is maintaining symmetry.
The structure of the hip truss system depends on the selected roof configuration
Features of the supporting frame of a hipped roof
Let us immediately note that the rafter system of a hipped roof will be more complex compared to traditional gable structures for two reasons.
- Due to the increase in the number of inclined planes and their joining to each other. At its core, the connection of slopes is intersection lines running at a certain angle to the horizon. The joints that form an angle protruding above the surface of the slopes are called roof ribs. From them, water flows down the slopes and accumulates in grooves (valleys) - lines of intersection with the internal corner. If all planes have the same slope, then the ribs and valleys divide the angle of the base at the junction of adjacent slopes in two and create a slope to the perimeter of the building of 45°.
Four-slope rafter systems are distinguished by the absence of full pediments, instead of which there are two triangular end slopes, as well as the presence of two lateral trapezoidal inclined planes, grooves and ribs
- Due to the fact that the purlins in a hipped structure form a closed contour, where the hip (diagonal) rafter legs are located along the lines of the ribs and valleys. They are longer than ordinary beams, which are installed longitudinally on the slopes at a distance between the intersections of the hip rafters in the upper frame. But between the lower parts of the diagonal legs, short rafters, called sprigs, are mounted. A distinctive feature of the frame of a hipped roof is the presence of trusses - wooden struts under the hip rafters.
The support purlins in hipped structures have a closed contour, where diagonal rafter legs are located along the lines of the valleys and ribs
Main structural elements rafter system of a hipped roof are:
Thus, the number of elements of the rafter system of a hipped roof is much greater than, for example, that of a gable roof, and this, naturally, increases the cost of its construction. However, in general, as we noted above, the installation of a hipped roof will not cost much more due to savings on laying the roofing pie, since there will be significantly less waste of insulating materials and covering flooring when cutting into a multi-slope structure.
Despite the fact that the rafter system of the hipped structure is more complex and expensive, the construction of the entire roof is more profitable due to the savings on arranging the roofing pie
In addition, the hipped design:
Video: gable or hip roof - what to choose
How to calculate the rafter system of a hipped roof
The supporting structure of a hipped roof can be layered if the structure has capital interior walls, or hanging, when intermediate supports are not provided in the structure. With a hanging structure, the rafters rest on the walls of the house and exert a bursting force on them. To relieve the load on the walls in such cases, a tie is installed at the base of the rafter legs, connecting the rafters to each other.
The use of a layered structure makes the frame lighter and more economical due to the fact that less lumber is required for its arrangement. Because of this, the layered rafter system is used much more often in the construction of multi-pitched roofs. But regardless of the type of rafters used, only correct calculation supporting frame and precise marking will increase the economic effect of erecting a hipped structure.
Marking and calculation of the supporting frame of a hipped roof
When calculating the rafter system, you must adhere to the following rules.
To determine the installation location of the rafters and find their length, you will need a template.
Using a template will make measurements and calculations much easier rafter frame hipped roof
The length of the rafter leg can be determined by its position (horizontal projection). There is a special table of coefficients for this, presented below. The length of the rafter is determined by the size of its projection, multiplied by a coefficient corresponding to the slope of the slope.
Table: relationship between the length and laying of the rafters
| Roof slope | Coefficient for calculating the length of intermediate rafters | Coefficient for calculating the length of corner rafters |
| 3:12 | 1,031 | 1,016 |
| 4:12 | 1,054 | 1,027 |
| 5:12 | 1,083 | 1,043 |
| 6:12 | 1,118 | 1,061 |
| 7:12 | 1,158 | 1,082 |
| 8:12 | 1,202 | 1,106 |
| 9:12 | 1,25 | 1,131 |
| 10:12 | 1,302 | 1,161 |
| 11:12 | 1,357 | 1,192 |
| 12:12 | 1,414 | 1,225 |
| Note: when constructing a roof frame for which there is no data in the table (for non-standard slopes), the parameters should be calculated using the Pythagorean theorem or using a mathematical proportion. | ||
Let's consider an example: a private house is being built in Yekaterinburg measuring 7.5x12 m with a planned height of a hip roof made of metal tiles of 2.7 m.
- First of all, we draw a drawing or sketch of the roof.
Before calculating the rafter system, it is necessary to make a sketch of the building and apply all the initial data to it
- We find the angle of inclination of the slopes using the formula: the tangent of the angle of inclination is equal to the ratio of the height of the roof to half the length of the span, in our case - to half the end side L = 7.5 / 2 = 3.75. Thus, tan α = 2.7 / 3.75 = 0.72. Using reference tables, we determine: α = 36°, which corresponds to the standards requiring a roof slope for metal tiles of at least 14°, and the climatic conditions of Yekaterinburg.
The tangent of the slope angle is determined by well-known formula calculation of the parties right triangle as the ratio of the opposite side to the adjacent
- We determine the position and edge of the ridge ridge, for which we apply a template at an angle of 36° in the middle of the upper trim of the end (the installation location of the first central intermediate rafter) to a height of 2.7 m and project the outline onto the sketch.
- We retreat ½ the thickness of the ridge beam from the center (key) line and install the end of the measuring rod at this point. At the other end of the rail we make marks for the outer and internal contour side wall, as well as overhang. We turn the rail to the side and from the inner corner of the outer trim we mark the location of the intermediate rafter along the mark of the internal contour, thus determining the installation location of the second intermediate central rafter.
When arranging the rafter frame of a hipped roof, the position of the central rafter legs is initially determined using a template and a measuring rod
- We carry out similar actions at all corners, determining the edges of the ridge ridge and the location of all central rafter legs.
- After planning the intermediate rafters, we determine their length from the table. In our example, the tilt angle is 36°, its tangent is 0.72, which corresponds to a ratio of 8.64:12. There is no such value in the table, so let’s calculate the coefficient relative to the line with the parameter 8:12 - 8.64/ 8 = 1.08. This means that the required coefficient is 1.202 · 1.08 = 1.298.
- By multiplying the depth of the intermediate rafters by the calculated coefficient, we find their length. Let us take into account the laying depth of 3 m, then L str = 3 · 1.298 = 3.89 m.
The length of the row and central intermediate rafters depends on the angle of the roof and the depth of their laying
- Similarly, we determine the length of the diagonal rafters, having previously calculated the laying equal to the distance from the corner of the connection of the side and end slopes to the first intermediate central rafter. According to the initial data, the position of the corner rafters is 7.5 / 2 = 3.75 m. Then the estimated length of the corner rafters will be equal to 3.75 1.298 = 4.87 m.
Corner rafters differ from intermediate rafters in the arrangement of undercuts with a double bevel in the ridge area, deeper laying and longer undercuts for the supporting part
- We calculate the overhang using the Pythagorean theorem according to the markings made or simply add the desired size to the length of the rafters, for example, 0.6 m plus at least 0.3 m for arranging an external drain.
To calculate the length of the overhang, you need to multiply its position by the coefficient for the intermediate or corner rafters or add the planned length of the overhang and at least 0.3 m to the estimated length of the rafters for organizing an external drainage system
- Having marked all the elements of the rafter frame, we determine the length of the ridge ridge, which is equal to the difference between the length of the side and the doubled value of the intermediate rafters: 12 – 2 3 = 6 m. It is at this distance that the ordinary rafters will be installed. If we take a step of 1 m, then we will need 5 row rafters, equal in length to the central ones. In addition, in the area where the intermediate central rafters are laid, which is 3 m long, two short rafters will be installed on one and the other side edge.
- Since the short rafters (springs) are attached to the diagonal ones, it means that end sides Between the corner and central intermediate rafters there will also be two flanges installed on the left and right.
Let's summarize - for the rafter frame of a hipped roof you will need:
- two pairs of hip (corner) rafters with a length of 4.87 + 0.6 + 0.3 = 5.77 m;
- three pairs of intermediate central rafters with a length of 3.89 + 0.6 + 0.3 = 4.79 m;
- five pairs of ordinary rafters 4.79 m long.
There are only ten pairs of rafters, the total length of which will be approximately 100 linear meters. We add here 6 m for the ridge beam, as well as a ten percent margin, and we get that approximately 117 linear meters of lumber are needed to make a simple hip rafter frame with struts, spacers, crossbars, trusses and fillets. But if the design includes racks and a bench, then they will have to be calculated separately or a larger percentage of the margin should be added.
Video: hip roof rafter system, installation technology
https://youtube.com/watch?v=n_Yr2QB3diMThe measuring rod greatly facilitates the work and helps to avoid gross errors when taking measurements. It is most often made independently from plywood 50 mm wide.
A few words need to be said about short rafters. They are calculated in the same way as intermediate ones: the laying multiplied by the coefficient for intermediate rafters from the table. However, the task can be simplified and you don’t have to specifically calculate the length of the spigots, since a sufficient percentage of the margin is taken, and the trimmings of the boards will be needed for the manufacture of elements reinforcing the structure - struts, spacers, crossbars, etc.
The length of short rafters (springs) can not be calculated, since scraps of lumber will be useful for the manufacture of reinforcing structural elements
Video: rafter frame of a hip roof, marking of elements and assembly
Calculation of lumber cross-section
After marking the position of the components of the rafter frame, it is necessary to select suitable lumber, i.e., determine their permissible cross-section. For calculations, you will need a zoned map of snow and wind loads and thermal resistance, as well as auxiliary tables based on regulations - SNiP II-3–79, SP 64.13330.2011, SNiP 2.01.07–85 and SP 20.13330.2011.
The installation of a hipped roof includes the determination of the required cross-section of lumber, which is carried out based on an analysis of the loads on the truss structure during operation
The load from snow cover is determined by the formula S = S g µ, where S is the desired snow load (kg/m²); Sg- standard load for real terrain, indicated on the map, µ is a correction factor depending on the slope of the roof. Since our tilt angle ranges from 30 to 60°, we calculate µ using the formula 0.033 · (60 – 36) = 0.792 (see note to the table below). Then S = 168 · 0.792 = 133 kg/m² (Ekaterinburg is located in the fourth climatic region, where S g = 168 kg/m2).
Table: determination of the µ indicator depending on the roof slope
| Determining the angle of the roof | |
| Tangent value | Angle α° |
| 0,27 | 15 |
| 0,36 | 20 |
| 0,47 | 25 |
| 0,58 | 30 |
| 0,7 | 35 |
| 0,84 | 40 |
| 1 | 45 |
| 1,2 | 50 |
| 1,4 | 55 |
| 1,73 | 60 |
| 2,14 | 65 |
| Note: if the slope angle (α) ≤ 30°, then the coefficient µ is taken as 1; if angle α ≥ 60°, then µ = 0; if 30°< α < 60°, µ высчитывают по формуле µ = 0,033 · (60 - α). |
|
Table: standard snow loads by region
| Region No. | I | II | III | IV | V | VI | VII | VIII |
| S g, kg/m 2 | 56 | 84 | 126 | 168 | 224 | 280 | 336 | 393 |
We calculate the wind load using the formula W = W o k c, where W o is the standard indicator on the map, k is the tabular index, c is the coefficient aerodynamic drag, varying from -1.8 to +0.8 and depending on the slope of the slopes. If the angle of inclination is more than 30°, then according to SNiP 2.01.07–85 clause 6.6, the maximum positive value aerodynamic index equal to 0.8.
Yekaterinburg belongs to the first zone in terms of wind load, the house is being built in one of the city districts, the height of the building including the roof is 8.7 m (zone “B” according to the table below), which means W o = 32 kg/m², k = 0 .65 and c = 0.8. Then W = 32 · 0.65 · 0.8 = 16.64 ≈ 17 kg/m². In other words, it is with this force that the wind at a height of 8.7 m presses on the roof.
Table: k index value for different types of terrain
| Building height Z, m | Coefficient k for terrain types | ||
| A | IN | WITH | |
| ≤ 5 | 0,75 | 0,5 | 0,4 |
| 10 | 1,0 | 0,65 | 0,4 |
| 20 | 1,25 | 0,85 | 0,55 |
| 40 | 1,5 | 1,1 | 0,8 |
| 60 | 1,7 | 1,3 | 1,0 |
| 80 | 1,85 | 1,45 | 1,15 |
| 100 | 2,0 | 1,6 | 1,25 |
| 150 | 2,25 | 1,9 | 1,55 |
| 200 | 2,45 | 2,1 | 1,8 |
| 250 | 2,65 | 2,3 | 2,0 |
| 300 | 2,75 | 2,5 | 2,2 |
| 350 | 2,75 | 2,75 | 2,35 |
| ≥480 | 2,75 | 2,75 | 2,75 |
| Note: “A” - open coasts of seas, lakes and reservoirs, as well as deserts, steppes, forest-steppes, tundra; “B” - urban areas, forests and other areas evenly covered with obstacles more than 10 m high; “C” - urban areas with buildings over 25 m high. |
|||
Table: standard wind load by region
| Region No. | Ia | I | II | III | IV | V | VI | VII |
| W o , kg/m 2 | 24 | 32 | 42 | 53 | 67 | 84 | 100 | 120 |
Now let's calculate the load on the supporting frame from the weight of the roof. To do this, add up the weight of all the layers of the roofing pie laid on top of the rafters. We leave the rafters open to achieve a decorative effect, which means we lay all the layers on top of the rafters. The load of the roof on the elements of the rafter system will be equal to the sum of the weights of the metal tiles, sheathing and counter-lattens, insulating films, insulation, additional sheathing and ventilation slats, a solid plywood base and the facing material of the under-roof room.
When determining the load on the supporting frame from the weight of the roof, the weights of all layers of the roofing cake laid on top of the rafters are summed up
The mass of each layer can be found in the manufacturer's instructions by selecting highest value density. We calculate the thickness of the heat insulator using a thermal resistance map for a specific area. We find it using the formula T = R λ P, where:
- T is the thickness of the heat insulator;
- R is the thermal resistance standard for a specific area, according to the map included in SNiP II-3–79, in our case 5.2 m 2 °C/W;
- λ is the thermal conductivity coefficient of the insulation, which for low-rise construction is taken equal to 0.04;
- P is the highest value of the density of the thermal insulation material. We will use Rocklight basalt insulation, for which P = 40 kg/m².
So, T = 5.2 · 0.04 · 40 = 8.32 ≈ 9 kg/m². Thus, the total load of the roof will be equal to 5 (metal tiles) + 4 (solid flooring) + 23 (main, additional and counter lathing) + 0.3 2 (insulating films) + 9 (insulation) + 3 (cladding) = 44 .6 ≈ 45 kg/m².
Having received all the necessary intermediate values, we determine the total load on the supporting frame of the hipped roof: Q = 133 + 17 + 45 = 195 kg/m².
The permissible cross-section of lumber is calculated using the formulas:
- H ≥ 9.5 · L max · √, if angle α > 30°;
- H ≥ 8.6 L max √, if α< 30°.
The following notations are used here:
- H - board width (cm);
- L max - maximum working length of rafters (m). Since the layered rafter legs are connected in the ridge area, the entire length is considered working and L max = 4.79 m;
- R bend is an indicator of the bending resistance of wood (kg/cm). According to the set of rules 64.13330.2011 for wood of grade II R bend = 130 kg/cm;
- B is the thickness of the board, taken arbitrarily. Let's assume B = 5 cm;
- Q r - load per linear meter of one rafter leg (kg/m). Qr = A · Q, where A is the pitch of the rafters, which in our case is 1 m. Therefore, Q r = 195 kg/m.
Let's substitute numeric values into the formula → H ≥ 9.5 · 4.79 · √ = 9.5 · 4.79 · 0.55 = 25.03 cm ≈ 250 mm.
Table: nominal sizes of softwood edged boards
| Board thickness, mm | Width (H) of boards, mm | ||||||||
| 16 | 75 | 100 | 125 | 150 | - | - | - | - | - |
| 19 | 75 | 100 | 125 | 150 | 175 | - | - | - | - |
| 22 | 75 | 100 | 125 | 150 | 175 | 200 | 225 | - | - |
| 25 | 75 | 100 | 125 | 150 | 175 | 200 | 225 | 250 | 275 |
| 32 | 75 | 100 | 125 | 150 | 175 | 200 | 225 | 250 | 275 |
| 40 | 75 | 100 | 125 | 150 | 175 | 200 | 225 | 250 | 275 |
| 44 | 75 | 100 | 125 | 150 | 175 | 200 | 225 | 250 | 275 |
| 50 | 75 | 100 | 125 | 150 | 175 | 200 | 225 | 250 | 275 |
| 60 | 75 | 100 | 125 | 150 | 175 | 200 | 225 | 250 | 275 |
| 75 | 75 | 100 | 125 | 150 | 175 | 200 | 225 | 250 | 275 |
| 100 | - | 100 | 125 | 150 | 175 | 200 | 225 | 250 | 275 |
| 125 | - | - | 125 | 150 | 175 | 200 | 225 | 250 | - |
| 150 | - | - | - | 150 | 175 | 200 | 225 | 250 | - |
| 175 | - | - | - | - | 175 | 200 | 225 | 250 | - |
| 200 | - | - | - | - | - | 200 | 225 | 250 | - |
| 250 | - | - | - | - | - | - | - | 250 | - |
From the table, the thickness of the board with a width of 250 mm can vary from 25 to 250 mm. A table of the dependence of the cross-section on the pitch and length of the rafters will help you determine more specifically. The length of the intermediate rafters is 4.79 m, pitch 1.0 m - look at the table and select the appropriate section. It is equal to 75X250 mm.
Table: cross-section of lumber depending on the length and pitch of the rafters
| Rafter spacing, cm | Rafter length, m | ||||||
| 3,0 | 3,5 | 4,0 | 4,5 | 5,0 | 5,5 | 6,0 | |
| 215 | 100Х150 | 100Х175 | 100Х200 | 100Х200 | 100Х200 | 100Х250 | - |
| 175 | 75Х150 | 75Х200 | 75Х200 | 100Х200 | 100Х200 | 100Х200 | 100Х250 |
| 140 | 75Х125 | 75Х175 | 75Х200 | 75Х200 | 75Х200 | 100Х200 | 100Х200 |
| 110 | 75Х150 | 75Х150 | 75Х175 | 75Х175 | 75Х200 | 75Х200 | 100Х200 |
| 90 | 50Х150 | 50Х175 | 50Х200 | 75Х175 | 75Х175 | 75Х250 | 75Х200 |
| 60 | 40Х150 | 40Х175 | 50Х150 | 50Х150 | 50Х175 | 50Х200 | 50Х200 |
Let's give another table for those who will use hardwood lumber.
Table: maximum deviations from the nominal dimensions of the boards
We check the correctness of the calculations by substituting the numerical parameters into the following inequality / ≤ 1. We get (3.125 · 195 x 4.79³) / (7.5 x 25³) = 0.57 - the cross section is selected accurately and with a good margin. Let's check less powerful beams with a section of 50x250 mm. We substitute the values again: (3.125 · 195 x 4.79³) / (5 x 25³) = 0.86. The inequality is satisfied again, so a beam measuring 50x250 mm is quite suitable for our roof.
Video: calculation of the hip roof rafter system
After all the intermediate calculations, we summarize: to erect the roof we will need 117 linear meters of edged boards with a section of 50X250 mm. This is approximately 1.5 m³. Since it was initially agreed that for a four-slope hip structure it was desirable to use lumber of the same section, then for the mauerlat the same timber should be purchased in an amount equal to the perimeter of the house - 7.5 2 + 12 2 = 39 linear meters. m. Taking into account a 10% margin for cutting and scrap, we get 43 linear meters or approximately 0.54 m³. Thus, we will need approximately 2 m³ of lumber with a section of 50X250 mm.
The length of the rafters is the interval from the cut for the supporting part to the cut for the ridge beam.
Video: example of roof calculation using an online calculator
Rafter system installation technology
The arrangement of a hipped structure has its own characteristics that must be taken into account:
Manufactured and assembled in compliance with all the rules, a layered rafter frame for a hipped roof will be a non-thrust structure. You can prevent the appearance of thrusts if the planes of the rafters are made horizontal in places where they support the Mauerlat.
In most cases, two schemes are used to support the rafter legs.
In hip hip structures, the length of the corner legs is often longer than the typical length of the lumber. Therefore, the beams and boards are spliced, trying to place the joints at a distance of 0.15 span lengths (L) from the center of the supports, which is approximately equivalent to the interval between the support points. The rafters are connected using the oblique cutting method, tightening the joints with bolts Ø12–14 mm. It is recommended to make the cut on the rafters, and not on the support beam, so that the cut does not weaken the support.
Since the standard length of most lumber does not exceed 6 m, diagonal rafters are increased in length using the oblique cutting method and connected with bolts when using timber or with nails and clamps if boards are spliced
Table: position of supports for corner rafters
| Span length, m | Types of supports | Location of supports |
| less than 7.5 | stand or strut | at the top of the rafters |
| less than 9.0 | stand or strut | at the top of the rafters |
| truss or stand | at the bottom of the rafters - 1/4L inc. | |
| over 9.0 | stand or strut | at the top of the rafters at the bottom of the rafters - 1/4L pr |
| truss or stand | in the center of the rafters | |
| rack | in the center of the rafters | |
| Note: Lpr is the length of the span, which is covered by rafters. | ||
To connect the frames to the rafters, the top of the half-rafters is ground off, keeping them in the same plane as the corner legs, and secured with nails. When placing sprigs on the rafters, make sure that they do not converge in one place. If you use not a notch, but a cranial bars 50X50 mm, stuffed in the lower zone of the rafters on both sides, then the rigidity of the rafter legs will be higher, which means their load-bearing capacity will increase.
To increase the rigidity of the rafter frame, it is recommended to use cranial bars stuffed on both sides at the bottom of the rafter legs when installing the rafters.
Do-it-yourself installation of a truss structure
The construction of the frame of a hipped roof is carried out in several stages.
- The materials are marked and calculated, after which roofing felt is laid as waterproofing along the entire perimeter of the building. A support for the racks and a Mauerlat are placed on top of it, securing it to the walls, fixing it especially well in the corners.
The Mauerlat in hipped structures is laid around the entire perimeter and is well secured to the walls, especially in the corners, to create a strong unit for attaching diagonal rafters
- A frame for the ridge girder is installed and the girder itself is laid, strictly maintaining the height and spatial arrangement of the ridge, since the strength and reliability of the entire rafter structure directly depends on this.
- Place the support posts using a water level for leveling and secure them under the ridge with inclined supports. The placement of racks is done based on the configuration of the roof - in a hip structure, the racks are installed in one row with an interval of no more than two meters, and in a hip roof - diagonally at the same interval from the corner.
- The central intermediate rafters are mounted, and then the ordinary ones, filling the middle of the side slopes.
- According to the markings, install corner rafters, preferably made with reinforcement, supporting them bottom on the corner of the Mauerlat, and with the upper fragment on the stand. The installation of the eaves overhang and drainage is also done here.
- Next, half-rafters (springs) are placed, strengthening the lower part of the diagonal legs with trusses, which will partially relieve the corner rafters, and they are sheathed along the perimeter of the roof with a wind board.
Truss grating is used for steep roofs and relatively large spans in order to avoid deflection of diagonal rafters
- After installation of the rafter system, the roofing pie is laid, the eaves overhangs and drainage system are installed.
When installing the rafter system of a hipped roof, you need to carefully consider the joining of the diagonal rafters, the central rafter at the end of the building, as well as the ridge beam
Video: hipped roof on nails and stool
Self-construction a hipped roof is, of course, not an easy process. But if you have measuring instruments, as well as necessary tools, you will succeed. The main thing is the desire to assemble the structure with your own hands and the desire to adhere to general principles. And in order for the roof to last as long as possible and maintain its amazingly beautiful appearance, try not to skimp on the elements of the rafter frame and use modern reliable metal fasteners for wood to fix them.
Classic - the design with four slopes remains unusual for Russians, evoking associations with the overseas way of life. They build it when they want to use interesting architectural solutions, to achieve a special effect that is perceived differently, the house compares favorably with monotonous buildings.
The photo of a hipped roof shows a wide variety of options, the main thing is to build in accordance with all the rules, then you can take advantage of the numerous advantages.
Types of hipped roofs
Making drawings of hipped roofs yourself is a difficult task: specialists will be able to correctly perform the calculations. The slopes are made as isosceles triangles; when the roof looks like a square from above, it is hipped, and if it resembles a rectangle, the variety is called hip.
Classic variation
The classics include a hip or Dutch roof, which is resistant to adverse weather conditions: strong winds and heavy snowfalls.
The surface of the structure is formed by 2 slopes in the form of a trapezoid on the long sides and 2 slopes with a triangular shape on the short sides.
Many modern architects believe that, aesthetically, a Dutch roof looks more presentable compared to a hip roof. The rafter system is formed by 4 support bars; they descend from the slopes to the upper corners of the structure.
2 types of half-hip roof:
- Dutch - a part is cut off from the side slopes from the end upper side.
- Danish - a part is cut off from the side slopes from the end bottom side.
Dutch roof design
The half-hip combines the characteristics of a gable and hip roof: the end slopes are presented in the form of triangles, the length of the hip is 1.5 - 3 times less than the length of the side slopes.
The design allows for the installation of a vertical window; it does not have a sharp protrusion characteristic of a gable roof, so the roof can withstand high wind loads.
Danish roof design
This type of hip roof is characterized by ease of installation; it is necessary to mount the end slope from below, leaving a small pediment under the ridge.
The Danish design provides the following benefits to users:
- No need to install problematic skylights who require high-quality waterproofing.
- The option provides good natural light to the attic floor thanks to vertical glazing.
Hip roof design
This type of roof is installed on buildings with a square perimeter; an important nuance is that all slopes must have the same shape. The construction of a hip structure is more complex when compared to a hip structure: it is necessary for the rafters to meet at one point.
Rafter system
DIY hipped roof - optimal solution for everyone who wants to save money on their family budget. Sequence of construction work:
The planning and design phase is time consuming and every detail needs to be carefully considered. No matter how easy the installation of the roof may seem, be sure to make a drawing, which will help identify defects and shortcomings.
If the calculation of a hipped roof is done incorrectly, it will be quite difficult to correct the situation - as a result of the error, the diagonal rafters will not connect at the ridge. It is better to use the best option; prepare a drawing using one of the special graphic programs.
Creating a 3D model allows you to see what the future roof will look like in order to prepare detail drawing, seek professional help.
Preparation of structural elements
The Mauerlat is laid on top along the perimeter of the walls, its task is to serve as a support for the rafters; the material used is 15x10 cm timber.
The slope of the roof is made using rafter legs, standard rafters are made from boards 50X150 mm, diagonal ones - 100X150 mm.
Special tightenings do not allow the rafter legs to move; they are fixed, and their ends are connected at the bottom; a 50X150 m board is taken for manufacturing.
A beam made of timber 100x100 mm or 100x150 mm is cross beam, serving as a support for the racks that hold the ridge girder.
The slopes do not allow the rafters to move; they are installed at an angle to the racks; the material used is timber with the same dimensions as for making the beam.
On vertical stand the ridge rests on it, it is made from material for the mauerlat.
The horizontal wind board connects the rafter ends from below; it is nailed to the rafters from the inside of the roof using a 100x50 mm board.
A filly is attached to the outside of the structure - a board made of exactly the same material.
The most complex element is considered to be the truss; it gives rigidity to the roof, connecting the horizontal and vertical components. The sprengel is made from timber with dimensions of 100x100 mm; it must be installed at an angle.
Rafters or shortened rafters are found only in hip roofs; they are made from 50x150 mm boards.
Attic floor installation
It is better to make roof hangers from steel; they are used for fastening special clamps and purlins, suspended ceilings significantly reduce the load.
If the trusses are steel, then the floor is made fireproof, prefabricated reinforced concrete slabs are laid between the steel beams, and lightweight insulation is placed on them.
Optimal material for manufacturing load-bearing structures- These are large-sized factory-produced panels with high fire resistance.
Installation of a ridge run
It will be necessary to make 2 runs if the structure has permanent longitudinal walls or there are internal pillars in 2 rows. When the building has internal supports, construction trusses are made and the ceiling is suspended from them. When the width of the house is large, the structure is suspended on steel clamps to the truss belt below.
Installation of rafters
The diagonal rafter legs must rest on the ridge; they are additionally secured with metal wire.
When one purlin is made, the diagonal legs are nailed to the console, and when there are two purlins, they are attached to a truss structure made of a horizontal beam with racks.
Photo of a hipped roof
DIY hipped roof: drawings and photos below.
How to install a hipped roof
Drawing of the rafter system plan
Installation of sheathing, vapor barrier, waterproofing
Arrangement of different layers of a hipped roof requires careful attention to each stage of work.
Each laid layer has its own function, all layers together form a single system, which provides protection to the structure.
Laying the sheathing
Sheathing is a wooden structure consisting of beams located across the rafters. The optimal cross-section of the sheathing bars is 50x50 mm.
Before installing the batten boards, they require treatment with antiseptic agents..
The lathing is installed either in a continuous layer or in increments of 100-150 mm (depending on the external covering).
The sheathing should be secured with nails.
Installation of sheathing
Installation of vapor barrier
A vapor barrier film is installed in order to to prevent moisture from entering the thermal insulation layer. The vapor barrier film is attached to the sheathing boards with an overlapping stapler. The overlaps are sealed with tape.
In this case, it is necessary to ensure that the film fits tightly to the boards. In areas where pipes or windows are installed, rubber or polyurethane adhesive tapes can be used.
CAREFULLY!
The vapor barrier material should not bend around the sheathing boards to prevent the formation of places for water accumulation.
Water vapor has a high penetrating ability, therefore installation of vapor barrier is a very important stage of work.
Installation of vapor barrier
Installation of waterproofing
After installing the insulation, waterproofing is laid. Waterproofing does not allow moisture accumulated in the under-roof space to pass into the roofing pie. Like thermal insulation film, the waterproofing is laid overlapping and the joints are glued.
It is especially important to correctly lay the film in the ridge part. The ridge area is most susceptible to the accumulation of condensate vapor.
The importance of each stage of installing a hip roof cannot be underestimated, much less refuse to install any element.
Installation of waterproofing
Hip roofs are considered the most durable and durable. They were installed more than a hundred years ago, and such structures have proven themselves to be reliable and durable.
Despite the complexity of the design, You can install it yourself, the main thing is to carry out each stage of work step by step in a clear sequence and choose a quality one, reliable material, because the roof must protect the house for decades.
Useful video
In this video you will learn how to build a hip roof with your own hands:
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