A gable roof or gable roof is a roof with two slopes, i.e. having 2 inclined surfaces (slopes) of a rectangular shape.
Due to its design features, the frame of a gable roof ideally combines simplicity of design and maintenance with reliability and durability. These and many other parameters make the construction of a gable roof a practical and rational solution for private and commercial housing construction.
In this article, we will look at how to make a rafter system for a gable roof with your own hands. For effective perception of the material, it is presented in the form of step-by-step instructions from A to Z, from selection and calculations, to installation of the Mauerlat and sheathing under the roof. Each stage is accompanied by tables, diagrams, drawings, drawings and photos.
The popularity of the house roof is due to a number of advantages:
The installation of a gable roof truss system depends, first of all, on its design.
There are several options for gable roofs (types, types):
The most common roof installation option due to its simplicity and reliability. Thanks to symmetry, a uniform distribution of loads on the load-bearing walls and mauerlat is achieved. The type and thickness of the insulation does not affect the choice of material.
The cross-section of the beam makes it possible to provide a reserve of bearing capacity. There is no possibility of rafters bending. Supports and struts can be placed almost anywhere.
An obvious drawback is the impossibility of arranging a full-fledged attic floor. Due to sharp corners, “dead” zones appear that are unsuitable for use.
The arrangement of one angle of more than 45° leads to a reduction in the amount of unused area. There is an opportunity to make living rooms under the roof. At the same time, the requirements for calculations increase, because the load on the walls and foundation will be distributed unevenly.
This roof design allows you to equip a full second floor under the roof.
Naturally, a simple gable rafter roof differs from a broken roof, not only visually. The main difficulty lies in the complexity of the calculations.
Building a roof of any complexity with your own hands requires knowledge of the purpose of the main structural elements.
The locations of the elements are shown in the photo.
Advice. For a metal rafter system, the Mauerlat must also be metal. For example, a channel or an I-profile.
The silhouette of the roof truss determines the appearance of the structure. Examples of farms in the photo.
The parameters of the rafters are important. They will be discussed below.
The location of the rack depending on the length of the roof is shown in the figure.
Advice. Installing the brace at an angle of 45° significantly reduces the risk of deformation from wind and snow loads.
In regions with significant wind and snow loads, not only longitudinal struts are installed (located in the same plane as the rafter pair), but also diagonal ones.
Advice. An important purpose of the sheathing is to redistribute the load from the roofing material to the rafter system.
Having a drawing and diagram indicating the location of all the listed structural elements will help in the work.
Advice. Be sure to add information about the passage of the ventilation shaft and chimney to the gable roof rafter system diagram.
The technology of their installation is determined by the type of roof.
When calculating the material for a gable roof, you need to choose high-quality wood without damage or wormholes. The presence of knots for beams, mauerlat and rafters is not allowed.
For sheathing boards, there should be a minimum of knots, and they should not fall out. The wood must be durable and treated with the necessary preparations that will increase its properties.
Advice. The length of the knot should not exceed 1/3 of the thickness of the timber.
Calculating the material parameters is an important step, so we present the calculation algorithm step by step.
It is important to know: the entire rafter system consists of many triangles, as the most rigid element. In turn, if the slopes have different shapes, i.e. are an irregular rectangle, then you need to divide it into separate components and calculate the load and amount of materials for each. After calculations, summarize the data.
The load on the rafters can be of three types:
Advice. To make a safety margin for the rafter system, it is better to add 10% to the calculation.
For reference: The weight of some roofing materials per 1 sq.m. presented in the table
Advice. It is desirable that the weight of roofing material per 1 sq.m. roof area did not exceed 50 kg.
In essence, the roof slope is like a sail and, if you take into account the wind load, the entire roof structure can be destroyed.
The calculation is carried out according to the formula: wind load is equal to the regional indicator multiplied by the correction factor. These indicators are contained in SNiP “Loads and Impacts” and are determined not only by the region, but also by the location of the house. For example, a private house surrounded by multi-story buildings experiences less load. A detached country house or cottage experiences increased wind loads.
The roof calculation for snow load is carried out according to the formula:
The total snow load is equal to the weight of the snow multiplied by the correction factor. The coefficient takes into account wind pressure and aerodynamic influence.
The weight of snow that falls on 1 square meter. roof area (according to SNiP 2.01.07-85) is in the range of 80-320 kg/sq.m.
Coefficients showing the dependence on the slope angle are shown in the photo.
Nuance. When the slope angle is over 60 ° the snow load does not affect the calculation. Because the snow will quickly slide down and will not affect the strength of the beam.
Nuance. The simultaneous action of many factors causes a synergy effect. This is worth considering (see photo).
It should be borne in mind that the roof has significant weight, which can cause damage to the rest of the building.
The more complex the shape of the roof, the greater the number of trusses and rafter elements needed to create the necessary safety margin.
The angle of inclination of a gable roof is determined primarily by the roofing material. After all, each of them puts forward their own demands.
It should be noted that increasing the angle increases the area of space under the roof, but also the amount of material. What affects the total cost of work.
Nuance. The minimum angle of inclination of a gable roof must be at least 5°.
The pitch of the gable roof rafters for residential buildings can be from 60 to 100 cm. The choice depends on the roofing material and the weight of the roof structure. Then the number of rafter legs is calculated by dividing the length of the slope by the distance between the rafter pairs plus 1. The resulting number determines the number of legs per slope. For the second, the number must be multiplied by 2.
The length of the rafters for the attic roof is calculated using the Pythagorean theorem.
Parameter "a"(roof height) is set independently. Its value determines the possibility of arranging a living space under the roof, the convenience of being in the attic, and the consumption of material for the construction of the roof.
Parameter "b" equal to half the width of the building.
Parameter "c" represents the hypotenuse of the triangle.
Advice. To the obtained value you need to add 60-70 cm for cutting and moving the rafter leg beyond the wall.
It is worth noting that the maximum length of the timber is 6 m.p. Therefore, if necessary, the timber for the rafters can be spliced (extension, joining, joining).
The method of splicing rafters along the length is shown in the photo.
The width of the roof rafters depends on the distance between opposite load-bearing walls.
The cross-section of the rafters of a gable roof depends on several factors:
You can determine the cross-section of the beam for the rafters, knowing the distance between the rafters and the length of the rafters using the data below.
Advice. The larger the installation pitch of the rafters, the greater the load on one rafter pair. This means that the cross-section of the rafters needs to be increased.
Dimensions of lumber (timbers and boards) for a gable rafter system:
For the roof structure under consideration, there are 2 options: layered and hanging rafters.
Let's consider each type in detail in order to make an informed choice.
They are used for roof widths of no more than 6 lm. Installation of hanging rafters is carried out by attaching the legs to the load-bearing wall and the ridge girder. The design of hanging rafters is special in that the rafter legs are under the influence of a bursting force. Hanging rafters with a tie installed between the legs reduce its impact. The tie in the rafter system can be wooden or metal. Often the ties are placed at the bottom, then they play the role of load-bearing beams. It is important to ensure that the tie is securely attached to the rafter leg. Because a bursting force is also transmitted to it.
Advice.
The higher the tightening is located, the greater strength it should have.
If the tightening is not installed, the load-bearing walls may simply “move apart” from the pressure created by the rafter system.
They are used for arranging roofs of any size. The design of layered rafters provides for the presence of a beam and a stand. The bench lying parallel to the Mauerlat takes on part of the load. Thus, the rafter legs are, as it were, inclined towards each other and supported by a stand. The rafter legs of the layered system work only in bending. And the ease of installation also tips the scales in their favor. The only drawback is the presence of a stand.
Due to the fact that modern roofs are distinguished by a wide variety of shapes and complexity of configurations, a combined type of rafter system is used.
After choosing the type of rafter system, you can accurately calculate the amount of materials. Write down the calculation results. At the same time, professionals recommend drawing up drawings for each roof element.
After the gable roof rafters have been calculated, installation can begin. We will divide the process into stages and give a description of each of them. The result will be a kind of step-by-step instructions containing additional information on each stage.
The beam is installed along the length of the wall on which the rafters will rest.
In log houses, the role of the mauerlat is played by the upper crown. In buildings built from porous material (aerated concrete, foam concrete) or brick, the Mauerlat is installed along the entire length of the load-bearing wall. In other cases, it can be installed between the rafter legs.
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Since the length of the Mauerlat exceeds the standard dimensions of lumber, it has to be spliced.
The connection of the Mauerlat to each other is done as shown in the figure.
The beams are cut only at an angle of 90°. Connections are made using bolts. Nails, wire, and wooden dowels are not used.
The Mauerlat is installed at the top of the wall. The installation technology provides several ways to attach the Mauerlat:
Advice.
The Mauerlat cannot be placed closer than 5 cm to the outer edge of the wall.
To protect the timber for the Mauerlat from damage, it is laid on a layer of waterproofing material, which most often is ordinary roofing felt.
The reliability of the Mauerlat fastening is an important aspect of construction. This is due to the fact that the roof slope is like a sail. That is, it experiences strong wind load. Therefore, the Mauerlat must be firmly fixed to the wall.
Anchor bolts. Ideal for monolithic structures.
Wooden dowels. Used for log houses and beams. But, they are always used with additional fasteners.
Staples.
Stud or fittings. It is used if the cottage is built from porous materials (aerated concrete, foam concrete).
Sliding mount (hinge). Tying in this way allows for the displacement of the rafter legs when the house shrinks.
Annealed wire (knitting, steel). Used as an additional mount in most cases.
Installation is carried out in two ways:
Advice. Before assembling the rafter legs, you need to apply markings. It is very convenient to use templates for these purposes. The rafter pairs assembled according to the template will be absolutely identical. To make a template, you need to take two boards, the length of each of which is equal to the length of one rafter, and connect them together.
The assembled pairs rise to the top and are installed on the Mauerlat. To do this, you need to make a gash at the bottom of the rafter legs.
Advice. Since the slots on the Mauerlat will weaken it, you can only make cuts on the rafter leg. To ensure that the cut is uniform and fits tightly to the base, you need to use a template. It is cut out of plywood.
Methods of fastening the rafter leg are shown in the figure.
You need to start installing rafter pairs from opposite ends of the roof.
Advice. To correctly install the rafter legs, it is better to use temporary struts and spacers.
A string is stretched between the fixed pairs. It will simplify the installation of subsequent rafter pairs. It will also indicate the level of the ridge.
If the rafter system is mounted directly on the roof of the house, then after installing the two outer rafter legs, the ridge support is installed. Next, the halves of the rafter pair are attached to it.
It is worth noting that the opinions of professionals differ on this issue. Some advise using a staggered fastening pattern, which will allow the increasing load to be distributed more evenly on the walls and foundation. This order involves installing one rafter in a checkerboard pattern. After part of the rafter legs is installed, the missing parts of the pair are mounted. Others insist that it is necessary to mount each pair in a sequential manner. Depending on the size of the structure and the configuration of the truss, the rafter legs are reinforced with supports and racks.
Nuance. Additional structural elements are connected using cutting. It is preferable to fix them with construction staples.
If necessary, you can lengthen the rafter leg.
Methods for splicing rafter legs are shown in the photo.
Advice. The method by which the mauerlat is lengthened (cut at 90°) cannot be used in this case. This will weaken the rafter.
The roof ridge unit is made by connecting the rafter legs at the top.
Roof ridge structure:
After the rafter system is installed, we perform major fastening of all structural elements.
The sheathing is installed in any case, and is designed for more convenient movement along the roof during work, as well as for fastening roofing material.
The sheathing pitch depends on the type of roofing material, for example:
As you can see, despite its apparent simplicity, the installation of a gable roof rafter system contains many pitfalls. But, based on the recommendations given, you can easily build a reliable structure with your own hands.
Wooden floors on joists are one of the oldest methods of flooring and the only one used in the northern regions of our country. Modern materials have only improved ancient technologies, due to which the scope of applications has significantly expanded and performance indicators have improved. Before proceeding directly to the consideration of various options, you should familiarize yourself a little with the engineering requirements for calculations.
Logs are distinguished from beams by their smaller size and mobility. If beams cannot be moved after installation, and repairs are very long and labor-intensive, then logs are a mobile architectural element. They are much easier to install and, if necessary, repairs are carried out faster.
Before you start building a floor, you need to study the requirements of regulatory documents for the size of the joists and the distance between them, taking into account the thickness of the floorboards.
Table of lag sections at a pitch of 70 cm
Table of distance between joists depending on the thickness of the board
In order to learn how to independently make calculations based on tables, it will be useful to consider a simple example. Initial data: the length of the room is 10 m, take a floorboard 30 mm thick.
Calculation method
According to the table, with such a thickness of the board, the distance between the logs is 50 cm; with a room length of 10 m, 20 logs will be needed. The distance between the logs and the walls cannot exceed 30 cm. This means that we will have to increase their number by one piece, the distance between the others will decrease to 45 centimeters.
Important note. During calculations, all roundings should be done only downwards, thus creating an additional margin of safety.
There is no need to calculate dimensions and distances accurate to the millimeter; no one takes such measurements. By the way, during construction, the vast majority of architectural elements and structures are measured in centimeters, the greatest accuracy is half a centimeter. Millimeters are almost never used during measurements.
These types of floors can be installed on a wooden or concrete base or on the ground. Each option has its own technological features, which must be kept in mind during work. As for the specific purpose of the premises, taking this parameter into account, the base of the floor and its operational characteristics are selected. The technology of the device itself remains almost unchanged. There are, of course, options for warm and cold floors, but these features also have a common construction algorithm.
Such floors can be made in both wooden and brick buildings and can have several varieties. The features of flooring need to be considered at the building design stage. Not only the purpose of each room and its size are taken into account, but also the climatic zone of residence, microclimate requirements and the financial capabilities of the developer. Below are step-by-step recommendations for constructing this type of flooring.
Depending on specific conditions, the algorithm can be slightly modified, but all main construction operations must be completed. The base can be moisture-resistant OSB boards or sheets of plywood. The design of the floor coverings provides for the possibility of laying insulation; the use of rolled and pressed glass wool or polystyrene foam is allowed. If there are insulation materials, then you should definitely install hydro- and vapor barriers.
Step 1. Take the dimensions of the room and calculate the number of joists, taking into account the above recommendations. Prepare materials and tools, make markings. Do the work slowly; mistakes made at this stage have extremely negative consequences. Eliminating them will take a lot of time.
Step 2. Start installing the logs from the outer wall ones. If the room has subfloors, then the logs can be fixed directly to them. To make work easier, it is better to use metal squares with perforations; such elements significantly speed up work and increase the stability of the joists. Using the mark on the wall, taking into account the thickness of the floorboards, align one end of the joist and fix its position.
Practical advice. When installing the outer joists, do not fix them immediately; first, you should only tighten the screws. This will allow you to make final fine adjustments.
Do the same actions at the second end of the log, constantly monitor its level position. Once the lag lays down normally, you can firmly fasten the ends and begin installing intermediate fasteners. The distance between them depends on the thickness of the boards that are used for the logs; it is approximately 70 centimeters.
Step 3. You need to stretch the ropes between the outermost joists; place all the remaining joists along this line. Constantly check with a level; installation accuracy should be ±1–2 mm. There is no point anymore, it takes a lot of extra time. A small difference in height will be removed during finishing of the front surface of the floorboards.
Step 4. If the floors are warm, then you need to lay thermal insulation between the joists; waterproofing and vapor barriers are used to prevent moisture from entering. The distances between the logs must be adjusted taking into account the length and width of the insulation. This can be either mineral wool or polystyrene foam, or bulk types of insulation. If all the preparatory work has been completed, you can begin laying the floorboards.
There are options for installing joists on floor beams. These are so-called ventilated floors and are most often used for non-residential premises. There is no need to be particularly precise; size alignment is done using lags. The logs are attached to the beams with nails or self-tapping screws from the side. The algorithm of work is the same. First, the extreme ones are placed, a rope is pulled between them and all the others are fixed along it.
Ventilation is carried out through special vents in the foundations; the distance between the ground and the floor must be at least fifty centimeters. Otherwise, the air exchange rate does not meet the required indicators, and this causes damage to wooden structures.
Such floors are considered more complex, labor-intensive and expensive; all wooden structures must be reliably protected from direct contact with concrete. Otherwise, the structures will quickly become unusable and will have to be replaced prematurely. There is a chemical way to protect lags from rotting processes using various impregnations. They are quite effective and actually prevent the process of wood deterioration. But unfortunately, impregnated wooden structures can no longer be considered environmentally friendly, and it is for this indicator that most developers install natural wooden floors.
If the logs are laid over the entire area on concrete, then waterproofing is required between them.
But they can also be secured using metal squares, which allows you to create a gap between the base and the joist. It must be borne in mind that in this case the load-bearing characteristics of the floor are somewhat reduced.
This fixation method has its advantages. Firstly, direct contact of wooden structures with concrete ones is completely excluded. Secondly, logs can also be installed on a black screed. Using corners, you can eliminate irregularities of several centimeters; there is no need to make a finishing screed. This saves a lot of time and money.
The second method of laying on a concrete screed is to lay the logs directly on it; a material based on modified bitumen is used for insulation.
The method is used for outbuildings, bathhouses, gazebos, verandas, etc. The wood must be treated with antiseptics. It is better to have a columnar foundation; if you want to make a more durable strip foundation, then it is necessary to provide vents for natural ventilation in advance.
How is this floor made?
Step 1. Remove the topsoil. You can use it to fill the beds or level the area in front of the house.
Step 2. Mark the columns. The distance between them is selected taking into account the load and size of the logs. The posts can be made of concrete, block or prefabricated. The dimensions of the supports are approximately 40x40 cm, the burial depth is within 30 cm. A layer of sand ≈ 10 cm thick should be poured onto the bottom and compacted.
Step 3. Fill the supports with concrete. To prepare concrete, you should use two parts crushed stone and three parts sand for one part of cement. Water is added as needed. There is no need to make formwork in the ground; formwork from boards or OSB scraps is installed above the ground level. During the manufacture of formwork, you need to use a level; all edges must be strictly vertical.
Practical advice. It is much easier to make columns from ready-made blocks. Horizontal alignment must be done along the rope. After the outer ones are aligned with the hydraulic level, a rope is pulled between them. Deviations should not exceed ± 1 cm. This variation is eliminated during installation of the log.
Step 4. Proceed to fixing the lags; you also need to start work from the outermost ones. For precise horizontal alignment, you can use shims. It is not advisable to take wedges made of wood; over time, they will dry out and wobble will appear: the floor will begin to creak unpleasantly when walking. Between wooden structures and concrete surfaces, it is imperative to place two layers of roofing material for reliable waterproofing.
Step 5. After the outermost logs are laid, a rope is stretched between them and all the remaining ones are laid under it. The logs are fixed with metal squares on dowels and screws. To increase stability, it is recommended to install them on both sides. Floor boards can be laid directly on the joists or a subfloor can be laid first. The final choice depends on the characteristics of the operation and purpose of the room.
Joists laid on blocks and waterproofing
Coniferous wood should be used for logs.
If possible, materials should be impregnated with antiseptics. These are very effective means for protecting wood not only from fungi, but also from many pests.
Always select joists with a safety margin, especially in cases where the installation method involves bending loads. It must be remembered that correcting mistakes made during the construction of flooring always costs much more than carrying out the work with high-quality materials and in compliance with recommended technologies.
Choose your joist boards carefully. They must be absolutely healthy without signs of rot. The presence of through cracks and rotten knots is completely prohibited. If there are large healthy through knots, then you need to install the joists in such a way that there is a stop under them.
When attaching the logs, do not allow the possibility of wobbling.
Most loose joists cause very unpleasant squeaks in the flooring while walking. To eliminate such phenomena, you will have to remove floor coverings; this is time-consuming and expensive; it is not always possible to keep the dismantled materials in a condition suitable for reuse.
Installation of rafters is one of the key stages of roof construction. To ensure that the rafter system does not deform or collapse under high loads during operation, the rafters must be properly secured.
When designing a rafter system, special attention is paid to this issue. The strength characteristics of the roofing system depend on the cross-section of the rafters and the pitch of their installation.
The rafter pitch is the distance between adjacent rafter legs. The minimum pitch of the rafters is 60 cm, the maximum is more than 1 meter. A simplified version of calculating rafter pitch involves using the table:
The length of the eaves slope must be divided by the rafter pitch selected in the table, then add one to the resulting value and round up to a whole number. The resulting result indicates the required number of rafter legs per slope. Then the length of the slope along the eaves should be divided by the calculated number of rafter legs - the final number corresponds to the value of the center distance between the rafters.
This calculation method is general; it does not take into account the specifics of roofing coverings and the type of insulation used. If you intend to lay a roll or slab insulator, it is recommended to adjust the pitch of the rafters to the size of the material. It should be taken into account that the width of the cotton insulation should be 1-1.5 cm greater than the span between the rafters.
When determining at what distance to install the rafters, you should also pay attention to the recommendations for installing the selected roofing covering.
Installing rafters with your own hands requires not only knowledge of the process technology, but also proper preparation of the wooden elements of the system for installation. The rafters are made from edged boards or timber; the cross-section of the lumber is selected at the roof design stage. The tree should not have cracks, wormholes or other damage.
Rafter legs should be made of well-dried coniferous wood to prevent their deformation.
Wooden elements must be treated with fire retardant and bioprotective compounds. Before you begin installation, you need to decide on the method of attaching the rafters to the mauerlat or beams, and the type of ridge connection. In accordance with the project, metal and wooden fasteners are selected, including:
When constructing the roof of a house, hanging or layered rafters are used. In some cases, a combination of both may be used. Hanging ones rest only on the walls of the building, while layered ones require the installation of additional supporting structures, so this option is primarily used if there is a middle load-bearing wall or support pillars inside the building box.
The lower part of the layered rafters rests against the mauerlat; accordingly, the walls of the structure must have sufficient width for the installation of a special supporting structure made of timber with a cross-section of 150×150 mm. The upper part of the layered rafters rests on the ridge girder. Thus, installation requires the installation of a purlin, for which racks should be mounted on the middle wall or pillars.
Hanging rafters rest only on the walls. This design can be mounted both on the Mauerlat and on thin walls without laying the Mauerlat. In this case, the support for the lower part of the legs is provided by floor beams protruding beyond the plane of the wall on both sides of the building. Hanging rafters are connected by a jumper (tightening, crossbar) which relieves the pushing forces. When covering large purlins, the trusses are reinforced with additional elements to enhance the rigidity of the structure. When installing hanging rafters on a mauerlat, a low-lying tie can serve as a floor beam.
Before installing the rafters, it is necessary to mount the scaffolding. This makes it possible to ensure the necessary safety and convenience of work.
When choosing how to install rafters, it is important to evaluate the complexity of the work and the weight of the rafter structures. If the assembled truss has a relatively light weight, or it is possible to use lifting equipment, then it is easier to assemble the structures on the ground, and then lift and install them on the roof. If the elements of the system are heavy and have to be lifted manually, then the trusses are assembled on the roof. The technology for installing roof trusses is described in the video instructions.
The connection of the upper ends of the rafters can be done in different ways. First of all, this is a butt mount. On the opposing rafter legs, cuts are made at the desired angle. Then the rafters are joined with the resulting ends and attached to two nails. The connection is further reinforced with a wooden or metal overlay.
Attaching the rafter legs with an overlap is done using bolts or studs with wide washers and nuts. In this case, the rafters are in contact with the planes.
If the rafter system is mounted on a wooden house with gables made of timber or logs, it is necessary to install the rafters on the walls using sliding fasteners to avoid deformation of the roof during shrinkage of the structure. Accordingly, in the ridge part, the rafters must be connected in a special way: the rafter legs must be positioned with a gap, and they are fastened together using a special movable metal connecting element.
If there is a ridge beam, installation of rafter trusses on the ground is not required - the rafter legs are installed one at a time and attached to the ridge girder.
The ridge run must be positioned strictly horizontally so that the rafter system evenly distributes the load experienced by the roof.
The lower ends of the rafters are attached to beams or mauerlats. The hanging rafter trusses, assembled according to a template, rise to the roof. The outer trusses are installed first. It is necessary to make two or three holes in the tightening to attach the rafters to the beams laid on the upper crown of the frame.
If hanging rafters are mounted on a stone building, it is necessary to use special fasteners - the so-called “ruff”, made of durable steel. This fastener is driven into every fourth row of brickwork. Using the loops extending from the ruff, you can secure the beams. It is recommended to use a strong beam as a mauerlat - in this case the load will be evenly transferred to the walls.
On buildings made of brick or other material that is not prone to shrinkage, the rafters should be firmly secured. To do this, a cutout is made in the rafter leg, the lower part of which should lie firmly on the Mauerlat. The rafter is fixed with three nails (two are driven in on both sides at an angle, and the third vertically from above) and tied with wire. A connection using corners and a support bar can also be used to prevent the rafters from shifting.
Proper installation of rafters involves making a fire break in the place where the chimney passes through the roof. If its arrangement involves the installation of a special rafter system, this should be taken into account when installing a shortened rafter leg (from the Mauerlat to the chimney structure). The distance between the structural elements and the pipe must be at least 130 mm.
+9Before installing the rafter system, the question arises at what step to install the floor beams. Correctly calculating the distance between the rafters means preventing subsequent deformation or even destruction of the roof frame. After reading the article to the end, readers will learn what the distance between the rafters should be for different types of roofing and how to make the calculation correctly.
Even at the design stage of a wooden house, all load calculations must be made. This also applies to the rafter system. This is especially important in wooden house construction, since the top link is often used instead of a Mauerlat. It is difficult to correct errors in such a design later. There is a technique for correctly calculating the distance between beams.
The span of the roof frame for the construction of a house made of timber usually exceeds 1 m, and the smallest permissible value is 60 cm, such indicators are indicated in GOSTs (see figure). You can correctly calculate the length of the rafters and their pitch using the following option:
Using a tape measure, the length of the roof slope is measured, the result is divided by the pitch size of the roof frame. For example, if the distance between the rafters is 1 m, then you need to divide by 1, if 70 cm, then by 0.7. The resulting figure is added to 1 and rounded to the nearest higher number. This way you can determine the number of beams for one roof slope.
You need to divide the length of the future slope by the result obtained. The result will be the distance between each rafter.
For example, consider a roof whose slope is 25.5 m and in increments of 0.6 m. You need to calculate the following indicators: 25.5:0.6=42.5, to 42.5+1=43.5. We round this figure to the nearest larger integer, we get 44. This is the number of rafter beams per 1 slope of the future roof.
Now we calculate the span between the rafters: 25.5:44 = 0.58 m. It turns out that you need to install the legs of the frame after 58 cm. This way you can easily calculate the pitch of any roof frame, single or complex, without taking into account the roof. But professionals recommend their calculations for a certain type of roof.
Since each forging material has its own characteristics and features. Among the most common are:
We will consider the step size for the most common types of coverage below.
The distance between the roof beams depends on the size of the sheet that the corrugated sheet has. The pitch of the roof frame beams under the corrugated sheeting is standardly taken to be no less than 60 cm and no more than 90 cm.
If this distance is greater, then boards with a larger cross-section are attached between the rafter beams. The cross-section of the rafter legs under the corrugated sheet is selected 50x100 or 150 mm.
The most important thing to consider when planning to attach corrugated sheets is the sheathing. It is made from boards with a cross-section of 30x100mm; it must be mounted with a span of 50 cm. It depends on the brand and thickness of the corrugated sheeting and the slope of the roof.
So, a 15º roof, grade C 10 corrugated sheeting is mounted on a continuous sheathing, C 21 corrugated sheeting is mounted on the sheathing with a span of 30 cm. The largest corrugated board C 44 is mounted on the sheathing in increments of 50 cm to 1 m. In this case, before attaching the sheathing, you need to consider the free space passage of a chimney, ventilation hood, etc.
The specifics of installing a rafter system for laying ceramic tiles are related to the weight of this roof. Ceramic tiles are made from clay, and this roofing weighs 9-10 times more than metal tiles. The calculation of the load on the rafter system for ceramic tiles is 40-60 kg/m2.
Beams for the roof rafter system for ceramic tiles are made only from dried material. The cross section is suitable 50x150 or 60x180 mm. The standard distance between the rafters for a tile roof is 80-120 cm. The span depends on the slope of the roof. At an angle of 15º, the span between the rafters is 80 cm, at 750 every 1 m 30 cm.
When calculating the step, you need to take into account the length of the beam. Taking the maximum length, the distance between the rafters is minimal. And, on the contrary, with a minimum length of rafters, the step is maximum.
When laying ceramic tiles, it is important to consider that you will need to walk on the roof. The maximum safe step of the rafter legs for such movement is 80 cm.
It is important when laying ceramic tiles to calculate the span of the sheathing. This distance is directly related to the size of the roofing material. A standard sheet of tiles is 40 cm long. Laying occurs with an overlap of 50 to 90 mm. When calculating the sheathing pitch, the overlap size is subtracted from the length of the tiles. The result is a pitch of 305-345 mm.
For a pitched roof for the construction of a house made of profiled timber, it is not difficult to make calculations. If the roof has a complex, multi-pitched shape, then each distance between the rafters is calculated separately per sheathing step. By securing the cord on the opposite side of the roof slope, you can easily mark the rows.
Metal tiles are used more often than ceramic or corrugated sheets. Externally, the roof resembles ceramic tiles, but unlike it, it is easier to install and lighter.
Metal tiles weigh from 35 kg/m2 of roofing. This makes it possible to lighten the rafter structure and use beams of smaller cross-section. The step between the rafter legs of the roof frame increases and is equal to 60 to 90 cm. The beam is used with a section of 50x150 mm.
To create a ventilated space, holes with a diameter of 12-13 mm are drilled in the beams under the roof.
The design of the roof frame for metal tiles is not much different from corrugated sheets or ceramic tiles. But there is a small peculiarity: the support from above is attached to the ridge girder from above, and not from the side as in other cases. This will create a ventilated gap under the metal tiles, which will prevent the accumulation of condensation.
Ondulin is a soft roof used for the construction of a house made of laminated veneer lumber or other material. Ondulin is produced in the form of sheets; it looks like painted slate, but is lightweight. This material is excellent for wooden houses, both low and large.
Rafter beams under the ondulin are placed with a distance of at least 60 cm, maximum 90 cm. For the rafter system, softwood timber with a section of 50x150 or 50x200 mm is used. A smaller cross-section will not provide sufficient strength to the rafter purlins.
The sheathing on the rafters is made of material with a cross-section of 40x50 mm in increments of 60 cm. This is quite enough for fastening sheets of ondulin with an overlap of 30 cm. Ondulin is fastened with special nails, which are sold as a set.
Slate is rarely used to cover the roofs of modern houses. But in dacha construction and household. This material is irreplaceable in buildings. It is low cost and easy to install.
Slate rafters
Slate rafter legs are used with a section of 50x100 or 50x150 mm. The fastening spacing between the rafters is no less than 60 cm and no more than 80 cm.
The slate lathing is made from 50x50 mm bars or 30x100 mm wide boards. The sheathing is laid in steps depending on the slope of the roof. For a steep pitched roof it is 45 cm. The consumption is 4 bars per 1 sheet of slate. For a flat pitched or gable roof 63-65 cm, the consumption is reduced to 4 bars per sheet.
The pitch of the rafter system under slate differs in the roof structure. For households It is not uncommon for buildings to have a shed roof installed.
Whether a safety margin is needed during installation depends on the shape of the roof. And the distance between the rafter beams directly depends on this.
A pitched roof is more durable and easier to assemble. The thickness of the rafters is selected depending on the type of wood, its strength and the specifics of a particular structure. The step between them can be 60-140 cm. The distance also takes into account whether the structure will be insulated. If yes, then the step should correspond to the width of the insulation.
The thickness of the rafter beams must be calculated depending on the roof slope. For a slight slope of 15-20º, you can use material with a cross section of 50x100 mm. For a steep slope of 45º, stronger ones with a section of 50x150 mm are needed.
If you do not calculate the pitch of the frame of a pitched or other type of roof correctly, the roof may move away, and the beams will sag and bend due to the weight of the structure. In this case, simple repairs are not enough; you will have to redo the entire structure. Therefore, it is so important to correctly calculate the distance between the legs of the rafters, depending on the roofing material used: corrugated sheets, ceramic or metal tiles, ondulin or slate, etc.
DIY pitched roof
A pitched roof is the easiest type of roof to install. It does not have any complex elements; it is installed on load-bearing walls that have different heights.
Typically, a pitched roof is used in the construction of outbuildings: garages, bathhouses, verandas, sheds, but it is also often found in the construction of private houses and country houses. So, let's figure out how to make a pitched roof with your own hands.
Slope roof angle
The first step when building a pitched roof is to determine the angle of inclination. The angle of inclination of a pitched roof will depend primarily on what roofing material you are going to cover it with. For a pitched roof made of corrugated sheets, the optimal slope angle will be 20 degrees, and the minimum slope will be 8 degrees. If you do less, the roof may simply collapse under the weight of snow in winter or spring, which is especially true for the regions of Siberia. For metal tiles, the minimum slope of a pitched roof rises to 25 degrees. When installing a pitched slate roof, this figure rises by another 10, and is already 35 degrees. For a seam roof, the minimum angle of inclination is from 18 to 35 degrees.
After determining the angle of the pitched roof, we raise the front wall relative to the rear wall to the height necessary to obtain the required degree; for this we will need to turn to some trigonometric formulas.
To make the calculation of a pitched roof clearer, here is a drawing:
tgA and sinA are found using the following table:
Let us give an example of calculating the height of the facade wall Lbc and the length of the rafters Lc for a house whose wall length Lсд = 5 m, and the slope angle of the pitched roof A = 25 degrees.
We determine the height of the front wall Lbc = 5 x tg 25 = 5 x 0.47 = 2.35 m.
We determine the length of the rafter leg Lc = 2.35 / 0.42 = 5.6 m.
Also, do not forget to add to the resulting length of the rafter leg the lengths of the rear and front overhangs, which will serve as protection for the house from precipitation. We take the length of the overhangs at 0.5 meters, you can take more, but not less. In total, you need to add another 1 meter. So, we get: Lc = 5.6 m + 1 m = 6.6 m. This concludes the calculation of the pitched roof, and we can proceed to further work.
Shed roof design
Like any other, a pitched roof includes the following elements:
1) The rafter system, which in turn consists of other additional elements, for example, to cover a large span, fasteners such as racks, spacers, crossbars, struts, etc. are required, which will impart the necessary rigidity to the rafter system;
2) Lathing, which acts as a base for the roof;
3) A layer of heat and waterproofing;
4) Roofing material.
Shed roof rafters
We begin the construction of a pitched roof with our own hands by constructing a rafter system. The truss system of a gable roof is essentially half of the truss system of a gable roof. To make rafters, it is better to take pine or spruce without knots. The joists must be thoroughly dried and treated with an antiseptic to repel pests, fire-resistant and moisture-repellent compounds.
The work of fastening the rafters of a pitched roof begins with laying the Mauerlat. Mauerlat is a log or beam that is laid along the entire length of the load-bearing wall. To ensure the reliability of the design, the Mauerlat must be tied to the wall using wire embedded in the wall, or secured with long anchor bolts.
In the Mauerlat it is necessary to cut out special nests into which the rafters of the pitched roof will be laid. Now we place the rafters with one end into the cut-out nest of the mauerlat, and with the other end we nail them to the beam or place them on the mauerlat of the opposite wall, and nail them with slate nails or screw them with wire for reliability.
If the width of the building is more than 4.5 meters, then the rafters are supported to avoid sagging.
Lathing
After installing the rafter system, you can begin making sheathing from planed boards treated with all the necessary compounds (see above). The boards are laid perpendicular to the rafters, with a distance from each other not exceeding 15 cm.
Steam and waterproofing
Now we lay the vapor barrier film and attach it to the sheathing using a construction stapler or small nails with a wide head, and if necessary, insulate the roof, depending on the nature of your building.
Next, the construction of the pitched roof continues with the stage of laying waterproofing material. A roll of waterproofing material is unwound along the entire length of the wall, perpendicular to the rafters, and gradually moves upward, making a slight overlap on the previous strip, and carefully sealing the joints.
Now all that remains is to cover our roof with the selected roofing material, and the work on installing a pitched roof with your own hands can be considered complete. We hope this article helps you! Good luck in construction!
Shed roof rafters
Shed roofs are not typical for residential buildings; they can most often be found on outbuildings - garages, sheds. The rafters of a pitched roof are always layered. What this term means can be found in the previous article: “Gable roof rafter system.” For roofs with spans of no more than 4.5 m, rafters without struts are installed. For everyone else - with struts.
Some technical data
Layered rafters are made from grade 2 timber. For work, you can use logs, beams, plates and boards. If you use logs, beams or plates, the pitch of the rafters will be 150-200 cm; when working with boards, the pitch will be shorter: 100-175 cm. For spans of 4.5 m, logs or plates with a diameter of 180-200 mm are used, boards are taken dimensions 60 x 220 mm. The final dimensions of the material from which the truss system of a pitched roof will be made is determined using calculations. But, it should be remembered that rafters made from logs cannot be less than 120 mm in diameter, from plates - d/2 = 70 mm, from boards - 40 x 150 mm.
Installation of a pitched roof If the roof structure requires the installation of struts, then logs, beams or boards can be used for them. The required dimensions of the material are also determined by calculation, but there are minimum values below which the material is not used. In particular, for logs - a diameter of at least 100 mm, for beams - 80 x 80 mm. Boards for struts are rarely used, but if they are used, the struts are made from two boards 25 x 150 mm.
When installing pitched roofs, a mauerlat made of logs is used; its dimensions should not be less than 180-200 mm. If not a solid log is placed, but short sections under each rafter leg, then their length should not be less than 600-800 mm, while maintaining the minimum diameter.
If necessary, a pitched roof can have purlins, which are made of logs or beams. The required cross-section of the purlin is calculated for each roof separately, but the minimum values for logs: 200-260 mm, and for beams: 180 x 180 mm. If the purlins are long, they will require racks. Under the racks, logs with a size of at least 130-200 mm or beams with a cross-section of at least 120 x 120 mm are used.
Rafter system without struts
Shed roof If the spans are less than 4.5 m, the rafters can be made without struts, but it is better to make them without braces.
The fastening of the rafters of a pitched roof in this case must meet the following conditions:
One support is fixed, but can be rotated
The second support can rotate and move freely.
Technically this is done in the following way:
In the lower part of the rafter leg, a notch is made with a tooth to rest against the mauerlat, or a support block is attached.
In the upper part, a cut is made with a bevel with a depth of no more than 0.25h, where h is the height of the rafters section. The bevel is needed so that the rafters can bend. Otherwise, the side surface of the cut will rest against the purlin and create a thrust. The length of the cut must be at least 0.5h.
If it is impossible to make a cut in the upper part of the rafter leg, then use a rafter cut, which is attached on both sides using mounting plates or wooden nails. Both the cut and the fastening of the trim should be done horizontally. On the run, the upper ends of the rafters are laid freely.
The manufacture of the upper fastening unit must be very precise, since any deviations instantly transform the system from a non-thrust system to a spacer one.
The calculation of the rafters of a pitched roof is always carried out on the condition that the loads act uniformly on the entire plane of the slope. In reality, everything is much more complicated. The wind can sweep snow onto one side of the slope; in spring, snow can slide unevenly off the roof, etc. To prevent a lean-to roof from slipping, its ridge girder is rigidly fixed, and the posts on which it rests must be absolutely vertical.
Rules for installing purlins
If the roof has spans of 3-4.6 meters in size, then a cantilever-beam system is used to construct the purlins. The console is needed to reduce the bending of the purlin and use material of a smaller cross-section for it. The purlins should be joined at a distance of 0.15-0.2 span lengths from the supports. Additionally, the purlins are reinforced with support beams. The support beam is connected to the purlin with bolts, and the racks to the support beams are connected with a tenon. For large roofs, trusses are placed between the racks every 4-5 spans. The end of the purlin is attached to the end wall with anchors. Installation of purlins
If the building design provides for an additional wall or beam in the attic, then the transverse struts will rest against the beam running along the purlin. The purlin itself, in this case, is mounted without support beams; it is supported by racks that are located above the pillars. In the middle of the span, the girder is supported by longitudinal struts. Longitudinal struts are mounted in pairs, through the rack. The struts and racks are connected to the purlin with round iron brackets. The minimum diameter of the staple is 10-12 mm.
For longer spans (for example, 6 meters), longitudinal struts are located at each rack. Thus, every third of the span is supported. The joints of the purlins are located in the middle of the spans. Staples are used as fasteners. If there is an additional wall or beam, then a bench will be used, as in the above option. All types of purlin fastenings can be seen in the photo:
Rafters with intermediate supports
If the span of a pitched roof is more than 4.5 m, then rafters with struts or struts must be installed. The struts can be installed under each rafter leg or through one. The angle of inclination of the strut is 45 degrees.
The installation of a large pitched roof truss system is possible only with additional purlins. Moreover, in order to strengthen the higher wall against the wind, additional struts are installed, which will transfer part of the wind load to the mauerlat.
Where the rafter legs rest on the mauerlat or purlins, horizontal platforms are hewn out. In the figure you can see options for rafters made of logs, timber or boards. Shed roof with additional purlins
The rafters are attached through one wire twist to a crutch, which is driven into the wall 20-30 cm below the mauerlat. We take a wire with a diameter of 2-3 mm, and twist it from 2-3 wires. If the area is with strong winds and the building is brick, then the mauerlat is attached with wire to the masonry. For wooden buildings, staples can be used.
If the size of the rafters is such that they need to be joined, the joints should be on racks or consoles. The joint itself is made using an oblique cut. For rafters made of logs, additional fastening of the joints is done using bolts 12-16 mm in diameter. And if the rafters are made of boards, then they are fastened with nails of 5 or 5.5 mm in diameter.
In a short article we gave the most general description of the design of rafters for a pitched roof. Those who want to do everything with their own hands will first have to sit down with engineering calculations to order the necessary material for the rafters. A special program for calculating truss structures can help you with this.
Roof construction. Shed roof
First, a little theory. What is a pitched roof, what are its features?
I often visit various regions of the CIS countries, and I noticed that gable roofs, or as they are also called “houses,” are generally popular in Russia. What does such a roof provide? Firstly, of course, a large attic or attic. It's practical. By building a house with a gable roof, you get another room that can be used for household needs or even as a living space, with appropriate insulation. In addition, this room is like a buffer. If it is not heated, the temperature inside is higher than outside, but lower than indoors. In this case, you can save significantly on ceiling insulation.
However, in regions where timber is a scarce or excessively expensive commodity, strong, prolonged winds are not uncommon, a pitched roof is popular. It is much more economical in materials than a gable roof, and also simpler in design. It takes twice or even three times less forest. In addition, shed roofs rarely have a large angle of inclination, usually no more than 25º. This reduces the area of attack on the roof by wind and makes it more resistant to blowing off. Shed roofs are often protected from being blown up by the wind with stone curbs, that is, only one part of the roof is open - the drainage part, while the other three are, as it were, inside the building, under the protection of these curbs. When choosing such a warrant with curbs, it is necessary to cover the top of the curbs with galvanized iron or tiles. Otherwise, precipitation will be absorbed into the wall, causing dampness and mold to appear, which is so difficult to remove. All this will lead to the destruction of the wall.
Let's move on to practice.
How to build a pitched roof
Materials and tools:
Wood: timber 15, timber 12, unedged board;
Slate nails;
Nails 80;
Hammer;
Hacksaw;
Hydrobarrier;
Stapler, staples for stapler;
Sharp knife.
We will take (as a starting point) a stone house with the latest seismic belt. It is on the seismic belt that we will lay the ceiling beams. We will use beam 12 as the ceiling beams. If you filled the seismic belt correctly, then you should have the same level along its entire perimeter. This eliminates the need to place a Mauerlat board under the ceiling beams. We place beams every 70-80 cm. This is the most optimal distance, which has been tested in practice more than once.
We fill the gaps with a stone, leaving the gaps on the drain side unfilled. If your house is stone, built from shell rock, then drive three rows of stone and lay a mauerlat board. Here it is mandatory. Firstly: it will smooth out natural unevenness, since masonry is rarely completely smooth, and secondly, it will strengthen the fastening of the roof joists.
We lay the logs with one end on the mauerlat board (parallel to the ceiling beam) and nail it to it, and with the other end close to the beam. We knock down the beams and logs with slate nails. You should end up with a right triangle.
Now, in the place where the logs and beams lie on the seismic belt, we fasten them to the belt with steel wire. To do this, we insert the wire under the belt (through the stone) and twist it around the beam. It is necessary to carry out this operation, since this is the weakest point - here the roof simply lies on the seismic belt.
It is necessary to cut off the bark (wane) from an unedged board with an axe. After all, it is in it that pests infest, which, having infected the bark, penetrate into the body of the board.
We stuff the board perpendicularly onto the joists. You can leave a distance of 1-15 cm between the boards (this way you can save material).
The end board on the drain side and on the top side should protrude 10 cm beyond the walls. This is done to prevent water from flooding under the roof. You should now have a wooden roof skeleton.
Let's move on to the next stage: laying the hydrobarrier. A hydrobarrier is the same roofing felt, plastic film or any other material that is sold in abundance in construction stores. It all depends on personal preferences or financial capabilities. We roll out the hydrobarrier from one edge of the roof to the other parallel to the board. We start from the lowest point of the roof, closest to the drain. Having unwound the hydrobarrier, cut off a piece from the roll and repeat all operations from the very beginning. We overlap the new piece over the old one, by 5-10 cm. If you chose film or any other similar material, you should attach it to the boards with a stapler. The roofing material itself is quite heavy.
Please note that moving on a roof covered with a hydrobarrier will become dangerous. There will be a danger of tripping or falling between the boards. Move carefully on the roof. It is better to lay boards over the hydrobarrier and walk on them.
The last stage has arrived, laying the slate. Laying is carried out according to the following rule: the sheet furthest from you is placed first at the very bottom of the roof, that is, the first one from the drain. And then we lay the slate closer and closer to “your” edge, overlapping one sheet over another. Usually one edge of the slate sheet is marked with a red stripe. So, you should always cover this red stripe with another sheet. Having laid the first row from one edge to the other, lay the next one, now also overlapping the lower edge onto the lying sheets.
Having laid out all the slate, we begin punching. Slate must also be nailed according to one simple rule: at the junction of four sheets. That is, two bottom rows and two top rows. The joint at this point forms a cross. Nail the topmost sheet into the second wave. It will press down all the sheets pressed down by it. This way you will press four sheets of slate with one nail. Along the edges you should also punch two nails at the top and bottom. No hurricane can blow away such a roof.
Your pitched roof is ready. Now you should nail the wind board onto the joists protruding from the top and bottom sides. This will prevent the roof from being blown away by the wind. Typically, wind boards are ordered from a carpentry shop. It is made from a single long board, exactly according to the size of your roof.
The last operation with the finished pitched roof will be the installation of flashings. You can install the ebb tides yourself or call specialists to install them. If you do not have certain skills, it is better to choose the second option, because roofing work and installation of flashings are high-altitude work associated with certain risks. Without the use of appropriate equipment, these works pose a danger to life and health.
If you did everything correctly, then your pitched roof will serve you for many years, protecting your home.
