Roofs with four slopes have higher reliability and resistance to loads. This design is much more complex than a conventional gable one, and installation takes longer. And yet, a do-it-yourself hipped roof is a completely doable task if you prepare properly and study in detail the intricacies of its construction.
Roof design
The hip roof has many variations. The most simple design It consists of 2 trapezoidal slopes connecting in the center of the roof, and 2 triangular slopes on the side of the gables. Sometimes all four slopes are made triangular, then the ribs of the roof converge at a central point. More complex designs suggest the presence of broken lines, a combination of short slopes with pediments, built-in straight and inclined windows, as well as multi-level slopes.
Without appropriate experience, it is impossible to build a rafter system of such a configuration, so it is better to pay attention to a standard hip roof.
Hip roof project
Hip roof design
The slope of the slopes can have an angle from 5 to 60 degrees. To calculate optimal value slope, the following factors must be taken into account:
- attic functionality;
- type of roofing;
- atmospheric loads in this region.
Gentle slopes are not suitable for arranging an attic, as they take up too much free space. Therefore, if an attic is planned in the house design, the roof slope should be 45 degrees or higher. You can select the angle of inclination depending on the type of roofing using the table.
Atmospheric loads also have great importance. Where there is a lot of snow, you cannot make a slope of less than 30 degrees, otherwise the rafter system will not withstand the loads. If the angle of inclination is more than 60 degrees, the snow load can be ignored. In addition to these factors, you should consider the location of objects such as water tanks or ventilation chambers. They are usually suspended from the rafters and place additional stress on them. After preliminary calculations you can start drawing up the drawing rafter system.
Materials for roof installation
Like a gable roof, a hip roof consists of a mauerlat, tie rods, rafters, support posts, ridge beams and sheathing. The difference between the second design is the location of the rafters and their length. For a hipped roof, it is recommended to use lumber from pine or larch, good quality, without defects, with a maximum humidity of 22%.
Attaching the Mauerlat to the wall
The rafters are made from boards with a section of 50x100 mm; if the roof area is very large, it is better to take 50x200 mm boards. For Mauerlat you need solid timber with a cross section of at least 150x150 mm. Additionally, you will need metal threaded studs for fastening the Mauerlat, boards for sheathing and overhead metal plates, which are used to connect wooden elements.
Threaded metal studs for fastening the Mauerlat
Before assembling the roof, lumber must be impregnated with an antiseptic agent.
Rafter system installation technology
Step 1. Laying the Mauerlat
In houses made of timber, the functions of the mauerlat are performed by the last crown of the log house, in which special grooves are cut for the rafters. In brick houses, the Mauerlat is laid on the walls around the perimeter of the box, having previously secured metal studs with threads between the bricks of the last rows. To more accurately mark the holes for fasteners, the timber is lifted and laid on top of the tips of the studs, and then hit with a hammer. After this, clear marks remain on the tree, along which holes are drilled.
Attaching the Mauerlat to the wall
Having removed the timber for drilling, the surface of the walls is covered with one or two layers of waterproofing material, usually roofing felt. It is placed directly on the studs and pressed downwards. Next, lay the Mauerlat, aligning the holes with the studs, align them horizontally and screw the nuts tightly onto the threads. At the corners, the beams are connected with metal plates or brackets. After fastening, the beam should not move even a millimeter, because the reliability of the entire rafter system depends on this.
Attaching the Mauerlat to the wall
Step 2. Installation of racks
If the house does not have a central load-bearing wall, it is necessary to lay the support beam perpendicular to the load-bearing floor beams. Connect two boards with a cross section of 50x200 mm, leaving a gap of 50 mm between them. To do this, short bars 50 mm thick are inserted between the boards and nailed down. The distance between the bars is about 1.5 m; the beams are not fastened at the ends. Having measured the middle of the attic, lay the support beam so that its ends extend beyond the boundaries of the Mauerlat by 10-15 cm.
Now take 3 boards 50x150 mm, cut them to the height of the roof, and install them on the support beam using a plumb line. Each post should rest against the beam where the boards are connected by a block. The racks are temporarily reinforced with beams made from beams. The top of the racks is connected by a ridge beam, for which a 50x200 mm board is used.
Step 3. Attaching the central rafters
They take a rafter board and attach it with one end to the ridge beam and the other to the mauerlat on the front side of the building. Immediately adjust the length of the eaves overhang and cut off the excess. Mark the lines of the cuts with a pencil, after which they cut off the upper end of the board and make a groove in the mauerlat 1/3 of the width of the rafter. The board is nailed to the ridge, the lower edge is inserted into the groove on the Mauerlat and secured with metal plates.
The rest of the rafters are made in the same way and installed in 60 cm increments from the facade of the house. The outer boards should be positioned perpendicular to the ridge beam and attached to its ends. On the opposite side of the building, everything is done in the same way. On the hips there is only one rafter on each side: the board is placed on its edge and attached with the upper end to the ridge beam, and the lower end is inserted between the boards of the support beam and secured with nails.
Step 4. Attaching the corner rafters
Installation of a hip roof truss system
To make corner rafters, two boards with a section of 50x150 mm are usually connected. In one of upper corners boxes, at the point of connection of the Mauerlat beams, drive a nail and tie a thin cord on it. At the point of connection between the ridge and the central rafter, a nail is also driven in from the hip side, a cord is pulled to it and secured. This is how the line of diagonal, or corner, rafters is designated. Their length must be the same, otherwise the roof will be uneven. The prepared rafter is lifted up, placed along the markings and connected to the ridge beam and mauerlat. The overhang of the rafters is approximately 50-70 cm.
Step 5. Installation of spigots
To secure the diagonal rafters, they use spigots - shortened rafters, the lower end of which rests on the mauerlat and located at right angles to the ridge beam. They are attached in increments of 60 cm, starting from the outermost ordinary rafter. As they approach the diagonal, the narozhniki make everything shorter. Now it is necessary to strengthen the structure with ties and braces, as well as install additional vertical supports.
If the span under the diagonal rafter is more than 7 m, you need to install another support at a distance of a quarter of the span from the corner of the attic. The lower end of the rack should rest on the floor beam. In the case when the beam is located further than the designated place or is completely absent, instead of a vertical post, a sprengel is attached - a horizontal jumper made of timber, the ends of which are nailed to the sprocket.
Step 5. Installation of the sheathing
Sheathing pitch under corrugated sheeting
When all the supports are installed, you can fill the sheathing. For a hipped roof, the sheathing is done in the same way as for a gable roof. First, a waterproofing membrane is attached to each slope separately. The joints are carefully taped, and then thin slats are placed on top of the membrane to ensure air gap. The boards are laid in increments of up to 40 cm, depending on the type of roof, and always perpendicular to the rafters.
Installation of roof sheathing
At this point, the assembly of the rafter system is considered complete. All that remains is to insulate the structure, lay the roofing, install wind strips and sheathe the overhangs. To make a hipped roof look more stylish, it is recommended to install inclined or straight windows on the slopes.
DIY hipped roof - instructions and calculations!
Find out how to install a hipped roof with your own hands! Detailed Guide on the construction of the rafter system, photo + video.
Rafter system of a hipped roof
The roof of a private house, which has four rather than one or two slopes, looks like a much more serious structure, which is what it is. Assembling such a rafter structure is no more difficult than a gable roof, but the rafter system of a hipped roof has more advantages. The quality of the roof is ensured by the strength of the rafter system.
DIY hipped roof
Features of a four-slope roof
- The main advantage is the absence of gables and gables. The unconventional design of the rafter system allows the roof to withstand strong winds without consequences, to minimize possible damage in places where the eaves overhang over time, and the absence of a pediment means savings on building materials and labor costs;
- The ends of the rafters, which intersect with each other and are attached to the ridge beam, give rigidity to the structure and prevent the roof from deforming under the weight of precipitation, roofing building materials or equipment mounted on the roof;
- The design and arrangement of the hip roof truss system suggests the possibility of installing eaves overhangs around the perimeter of the entire house, protecting the facade from atmospheric influences and temperature changes;
- In terms of architectural compliance, a hipped roof when adding a veranda or attic to a house makes the building more resistant to unevenly distributed loads;
- The aesthetics of a hipped roof have been proven by practice and time - such structures have been used since the times when people learned to build shelters for themselves, which later turned into durable and beautiful houses.
How the rafter system of a hipped roof will be constructed depends on whether the roof will be hip or hip. Therefore, it is worth taking a closer look at these types of hipped roofs, their features and structure.
Hip roof device
Hip roof
A hip-type roof is an assembly of two trapezoidal or triangular wooden knots. These elements are fastened together by the planes of the upper surfaces, and the edges of the triangles are overlapped by ridge slopes.
A roofing pie consisting of several layers is mounted on the rafter frame of the hip roof: a waterproofing material, a heat insulator, a ventilation layer of building materials, and a finishing decorative and protective coating. According to the type of fastening, the rafter system of a hip roof is divided into hanging and layered types. The layered design of the hipped roof rafter system is more economical, easier to install and easier to design. 
Rafter systems
Important: When the hip roof slopes ≤ 35°, it is necessary to install auxiliary support beams to strengthen the long span with layered rafters. Additional supports protect the house from atmospheric moisture, strong winds and temperature changes.
Scheme truss structure roofs with four slopes
- Rafters of a slanted design are a beam mounted diagonally, with one end resting on the Mauerlat, and the second end attached to the next pair of rafters. Since the slanted rafters are very large in their expanded form, they must be immediately securely fixed on the roof. Also, the slanted rafters act as a support for the riggers;
- Trapezoidal wooden assemblies for roof slopes;
- Narozhniks are small-sized structures made of rafter beams short length, mounted on rafters of the mowing type. If the width of the walls of the house is ≥ 4.5 m, then the rafter structure is connected into a block of several elements, so that these blocks can then be used to form a single roof;
- Struts, crossbars and racks serve to minimize the size and use of spigots. The use of these elements allows you to assemble the roof with virtually no additional reinforcement;
- The beds serve as supports for racks and struts; their lower end rests against brick supports on the inner wall end or is adjusted to size using wooden blocks;
- The purlin is a beam laid parallel to the lower support beam. Serves to ensure the strength of the rafter structure;
- Sprengels increase the rigidity of the rafter system in all directions. The trusses must have the same cross-section as the rafters, and they are attached along the length of the span.
Scheme of a hipped roof
Hip roof
The tent-type roof is assembled from triangular wooden structures. It will not be easy for a non-specialist to cope with the construction of such a roof, since it is important to absolutely accurately observe all dimensions and dimensions in order to achieve complete symmetry of the hip roof. But thanks to such a roof, your house will withstand winds of any strength, even a hurricane. A homemade hipped roof, the rafter system of which is designed in the form of a tent, perfectly protects housing from the penetration of cold and moisture even into the attic or attic space.
Roof in the form of a tent
In terms of design, the drawings of the hip and hip rafter systems are similar, since they consist of the same units and elements. The only difference is the length of the rafters and installation options. In a tent structure, hanging or layered rafters also work well, but it is very difficult for an amateur to secure the hanging elements on his own - the help of a professional will be required. A hip roof is often installed over areas without internal ceilings, partitions or walls, and rafter beams for supports are laid on load-bearing walls. Parts of a layered structure are cheaper and easier to manufacture, but in order to be able to work with them, it is necessary to have an internal load-bearing wall and/or concrete columns.
Non-thrust-layered scheme
How to work with rafters - tips and rules
- Before starting work with any wood products, they must be treated with antiseptic and fire retardant agents;
- Wood for any elements of the rafter system must be well dried in natural conditions. The moisture content of the material should be ≤ 22%;
- Mauerlat is made of timber with a square section of 150 mm or rectangular cross-section 150 x 100 mm.
- The rafters must be ≥ 50 mm long and ≥ 150 mm wide;
- For all products of the rafter system, one type of wood is used, and preferably coniferous species;
- To produce a large number of crossbars, racks and purlins with one cut angle, a pre-prepared template is used.
Template for marking rafters
In the hip rafter system, a support is first made in the form of a Mauerlat. Not only the strength of the structure, but also the aesthetics of the entire roof depends on the even structure of the Mauerlat, so the support beams must be laid strictly horizontally. The alignment of the mauerlat can be facilitated by pouring a small grillage (formwork) around the entire perimeter of the walls of the house.
To attach the grillage to the walls, reinforcing pins driven or inserted into the wall are used. Through the holes in these rods, the Mauerlat is attached with threaded connections to the walls and grillage.
How to attach the Mauerlat
How to assemble and install on site a hip roof rafter system:
- The upper planes of the load-bearing walls of the house must be opened with waterproofing agents - mastic, bitumen, tar - before installing the rafters. Roofing felt is laid on top of the waterproofing layer;
- The support beam from which the Mauerlat will be assembled is mounted on pins in the walls and tightened with nuts and washers. When installing the Mauerlat, you need to constantly check its horizontalness using a level;
- The central support is attached next - the racks with the ridge will be attached to it. The support beam is laid either on the side beams of the mauerlat, or on the surface of the internal load-bearing walls;
- Vertical beams are installed for the main support of the ridge. The ridge supports do not need to be rigidly fastened immediately - only after the rafter system has been completely assembled. Rigidity can be provided by steel angles, wooden spacers or metal studs;
- To ensure that the hip roof is perfectly symmetrical, the rafters of triangular hip structures rest on the Mauerlat in the calculated locations. Markings for each rafter must be done in advance so that the beam does not fall on fastening rod. Intermediate rafter beams are needed to connect the ridge to the walls;
- Next, slanted rafter beams are installed, which will connect each corner of the house with the end of the ridge beam;
Important: a distance of ≥ 50 cm is maintained between the overhang and the wall. If the site is selected in a region with strong winds, then this distance increases by 2 times. This ensures protection of the roof and walls from precipitation, which can blow in and moisten the surfaces down to the foundation.
Attaching the rafters to the mauerlat
- Now you can attach ordinary rafter beams to connect the Mauerlat to the ridge. The distance between the rafters is calculated based on the overall dimensions of the roof and the length of the intermediate rafters. Some roofing building materials need to be laid on frequently installed sheathing, so there are no general recommendations for maintaining distances. Ordinary rafters in the standard solution are attached to a groove every 0.4-0.5 m, and the attachment point can also be reinforced with nails or steel overhead plates;
- If the roof has a small angle of inclination, then the rafters need to be reinforced with trusses due to the additional pressure of snow in winter;
- To strengthen the upper end of the slanted rafter beams, a truss made of trusses is installed. It consists of 2 struts extending from one point.
- The last step in the construction of the rafter system is lathing. The material for the sheathing frame is selected based on the roofing material. Most often these are square slats with a cross-section of 5 cm, and if the sheathing is solid, then you can use five-layer plywood for the board.
Hip roof rafter system, video, photo
The roof of a private house, which has four rather than one or two slopes, looks like a much more serious structure, which is what it is. Assembling such a rafter structure is no more difficult than a gable roof, but the rafter system of a hipped roof has more advantages.
In private housing construction, in addition to the common two pitched 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 structure of a hipped roof is the possibility of installing a regular window at the ends of the house, as well as the absence of a sharp protrusion typical for 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. Distinctive feature 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
The main structural elements of the 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, installing a hipped roof will not cost much more due to savings on installation 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 building. 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 markings will increase economic effect from the construction of 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 it much easier to measure and calculate the rafter frame of a 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 angle of inclination of the slopes is determined by the well-known formula for calculating the sides of a right triangle as the ratio of the opposite side to the adjacent one
- 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 slats, we make marks for the outer and inner contours of the side wall, as well as the 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 (spreaders) are attached to the diagonal ones, this means that two spandrels on the left and right will also be installed on the end sides between the corner and central intermediate rafters.
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); S g - standard load for real terrain, indicated on the map, µ - 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 aerodynamic drag coefficient, 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 of the aerodynamic index, equal to 0.8, is taken into account.
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 roof load 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 facing material 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 the highest density value. 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.
Substitute the numerical 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 edged boards section 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.
Because the standard length 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
Frame construction hipped roof is produced 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, corner rafters are installed, preferably made with reinforcement, resting their lower part on the corner of the Mauerlat, and their 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 the 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.
The rafter system is a combination of all supporting elements, forming a frame on which the roofing cake lies. 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 the expensive services of companies that perform roofing work professionally, we will tell you what the rafter system 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 hip roof truss system takes different kind, depending on the initial conditions: the area of the house to be covered and internal layout. There are three types:
What type of rafter system is suitable for specific house, are determined during the design period by 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 up the values of all loads, the total load is determined, which, depending on the roofing material used, 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 a ready-made diagram of a hipped 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 ridge run 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
The problem of choosing the most successful roof frame design is always accompanied by two conflicting desires. No matter what type of building is planned for construction, any developer would prefer to get the most attractive, strong and durable structure possible, at relatively low construction costs. The hipped roof rafter system most fully meets the above requirements, which today is one of the optimal design solutions for the housing stock.
Advantages and disadvantages of using hip roofs
Even a superficial glance at a hipped roof system suggests that such a rafter frame system of two pairs of symmetrical slopes will look much more elegant and prettier than a simplified design gable design.
It is clear that most future customers prefer to build a rafter system for their home not only because interesting design, although the factor appearance buildings are also important. First of all, such a design solution is chosen because of the tangible advantages of the four-slope system:
- The use of two additional opposing slopes instead of roof gables reduces the wind load on the entire structure of the rafter system;
- Installing two additional inclined surfaces makes it possible to remove and dump any amount of rainwater, snow and ice from the roofing pie, most dangerous looking moisture - water condensate;
- Using a hipped roof system allows you to reduce heat loss by reducing the total area of the roofing and gable surfaces.
Important! A roof with four slopes cannot be built “by eye” and using the fitting method, therefore, before making rafters for the roof, the dimensions of the rafter beams of the four-slope system must be calculated using tables and checked by lengths and joining angles before cutting and assembly.
The four-slope rafter system is a balanced structure in which the loads on the roof frame from the roofing pie, snow and wind are mutually compensated, like in a house of cards. If you try to assemble a frame without careful design preparation, instead of maximum strength and stability, you may end up with an emergency object.
The four-slope rafter system also has a lot of disadvantages. Most often, problems arise due to the need to take additional measures to protect the joints on the mating line of the slopes. In addition, 30% more roofing material, insulation and expensive long timber will be required.
Options for a hipped roof scheme
In addition to the classic version, which uses two triangular and two trapezoidal planes, a roof with four slopes can be built using one of the types of frame:
All modifications of the hip or hip scheme are designed for specific climatic conditions of roof operation. For example, Danish roofs resist wind well and a large number snow, while "Dutch" boots are designed to withstand heavy rains and snowfalls in urban areas. Tent schemes with small angles The slope of the slope is used for buildings in open, windy areas. The classic version can be used for any conditions, but in this case you will need to carefully check the position of the building relative to the wind rose.
Construction of a rafter frame for a hipped roof
The easiest way to understand the structure of the rafter system of a hipped roof is from the drawings. In a conventional gable structure, the weight of the rafter beams was partially transferred to the ridge girder and to the timber frame of the walls or mauerlat.
Balancing the two roof slopes is relatively simple by simply adjusting the rafters and installing struts.
In a four-slope rafter system, everything is much more complicated, therefore, in addition to ordinary rafters, a significantly larger number of power elements have to be used in the roof frame:
- Sloping or diagonal rafters. With their help, the side slopes of the roof are formed, the rafter system is balanced in the direction along the main axis of the roof;
- Central rafter beams. Often the strength and stability of diagonal rafters is not enough, especially on large roofs, so you have to use central rafters installed on the same axis with the ridge girder;
- Roofs are short rafters that form the side slopes of the roof. The length of each frame is calculated and cut at the location where the rafter is installed on the frame.
Except rafter elements, when building a hipped roof, trusses, struts and struts must be used. With their help, the load is strengthened and redistributed in the roof’s load-bearing elements.
For your information! The result is a rather complex multi-element design; in order to take into account all the requirements for the strength and stability of the rafter system, it is best to use a ready-made software package, even the simplest one.
Of course, you can build a rafter system without any design and calculations. For example, you can use timber and boards of increased cross-section, and instead of the recommended strength coefficient of 1.4 units, get a two or three times safety margin bearing capacity. But it is worth understanding that in this case the weight of the rafter system and the cost of building a hipped roof will increase by 3 and 8 times, respectively.
Methodology for calculating the lengths of rafters of a hipped system
For simple buildings, for example, a gazebo, barn or small garden house, you can use a simplified version of calculating the lengths of rafter beams. To do this, you will need to draw up drawings of the rafter system of the hipped roof. To simplify the calculation, we choose the classic version with two side triangular hips and trapezoidal main slopes.
The basis for calculating the roof truss structure is a system of right triangles. Each rafter represents the hypotenuse of a right triangle. The smaller leg is equal to the height of the ridge posts, and the larger leg coincides with the projection of the rafter onto the plane ceiling, which is also called mortgage. The projection line intersects with the axial or projection of the ridge beam at an angle of 45°, which greatly simplifies the calculation.
Initially, you will need to select the angle of inclination of the slopes, usually 20-35 o, depending on the design of the hipped roof and the type of roofing. For calculations, you can use the Pythagorean theorem for a right triangle or standard tables with ready-made conversion factors for rafter lengths for given angles. In such tables, the angle value is indicated in the form decimal, for example, 3:12. This means that for a given angle and laying length of 12 m, the height of the rack will be 3 m. The conversion factor for a diagonal rafter is also given here; it is enough to multiply the laying length by the value of the corresponding table correction.
At the first stage, we will determine the installation coordinates of the vertical posts of the ridge and its length. To do this, measure the distance from the corner to the intersection point of the center line and the Mauerlat, then lay off the resulting segment from the corner along the ridge axis and draw a line parallel to the wall. The intersection point of the axis and the drawn line will give the installation location for one of the ridge posts. A similar procedure will need to be performed again on the opposite wall, as a result we will obtain the installation point of the second rack and the length of the ridge beam.
At the second stage, using a plumb line, you will need to measure the position of the diagonal rafter with a ruler, knowing the angle of inclination of the slope, you can calculate the length of the slanted rafter beam. The length of row and central rafters is calculated in a similar way.
The calculation of the moneymakers is a little more complicated. First, the diagonal rafter beam is marked with the step of installing the flanges, as a rule, this is 70-90 cm. Each flange can be considered as a leg of a triangle. Knowing the size of the leg and the height of the junction point of the outer rafter to the diagonal beam, you can easily calculate the size of the outer rafter.
If trusses are used in the design of a hipped roof to strengthen the diagonals, then their size can be calculated even more easily. Most often they are installed at a distance from the corner of 1/3 of the laying length.
Features of assembling a hipped roof frame
The process of assembling the rafter system of a hipped roof always begins with the installation of the central element of the frame - the ridge girder and vertical posts. A ridge bench can be assembled from timber with a cross-section of 70x100 mm, but most often the racks are made from a pair of 50 mm boards. To increase the rigidity of the entire system of ridge beams and posts, metal plates are stuffed into the corner joints, and the frame itself is reinforced with internal bracing.
Typically, the assembly of rafter beams is carried out using nails, and the places of reinforcement are fixed with steel plates bolted connections. Before installing the rafter beams, a sawing template in the form of a right triangle is usually made from a sheet of plywood. The acute angle should correspond to the angle of inclination of the slopes. Using a template, mounting areas for supports on the mauerlat and ridge are cut out on the rafters.
The process of installing rafters begins with the installation of central rafter beams, which will provide the necessary rigidity of the ridge frame in the axial direction. Sometimes they do without them, in which case they immediately proceed to the installation of the outer pairs of ordinary rafters, but the timber is only grabbed with nails, without final fixation to the ridge.
After strengthening the ridge frame, corner diagonal rafters are installed. Typically, the length of a beam or beam is cut with a margin, since the upper edge will need to be sawed at a double angle, first at the angle of inclination of the slope, then the oblique edge is beveled at an angle of 45 degrees. At the last stage, they install the trusses, struts, fill the frames and ordinary rafters.
Conclusion
The most difficult stage of assembling the rafter system of a hipped roof is the joining of two diagonal beams with the ridge. The strength and stability of the entire hipped roof depends on how accurately the diagonals are inserted, so most of the time has to be spent on adjusting and trimming the size of the rafters. The rest of the assembly operations are practically no different from the construction of a gable rafter system.
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 to install such a design, it is worth familiarizing yourself with the algorithm according to which the rafter system of a hipped roof is constructed and with the specifics of its design.
The class of hipped 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 options 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 hip structures are usually erected over square buildings, and hip structures over rectangular houses. Both soft and . Characteristic square or rectangular shape repeat 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 wooden house or on a 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:
- With rigid fastening of the upper and lower heels of the rafters 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, This:
- 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 slanted 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 certain design solution rows for hip construction.
- 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 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 docking point must be located above a 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. 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 ease of implementation further actions the contour of the roof is formed by 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 outline the cut lines from below where the block intersects the floor beam and corner connection cornice 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 on the outside of the bevel leg being constructed. 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 the 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 - 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.
