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:
- design variability;
- simplicity in calculations;
- naturalness of water flow;
- integrity of the structure reduces the likelihood of leaks;
- efficiency;
- preserving the usable area of the attic or the possibility of arranging an attic;
- high maintainability;
- strength and wear resistance.
Types of gable roof
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.
Design of a gable roof truss system
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.
- Mauerlat. Designed to distribute the load from the rafter system onto the load-bearing walls of the building. To arrange the Mauerlat, a timber made of durable wood is selected. Preferably larch, pine, oak. The cross-section of the timber depends on its type - solid or glued, as well as on the expected age of the structure. The most popular sizes are 100x100, 150x150 mm.
Advice. For a metal rafter system, the Mauerlat must also be metal. For example, a channel or an I-profile.
- Rafter leg. The main element of the system. To make rafter legs, a strong beam or log is used. The legs connected at the top form a truss.
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.
- Puff- connects the rafter legs and gives them rigidity.
- Run:
- Ridge run, is mounted at the junction of one rafter to another. In the future, the roof ridge will be installed on it.
- Side purlins, they provide the truss with additional rigidity. Their number and size depend on the load on the system.
- Rafter stand- vertically located beam. It also takes on part of the load from the weight of the roof. In a simple gable roof it is usually located in the center. With a significant span width - in the center and on the sides. In an asymmetrical gable roof, the installation location depends on the length of the rafters. If there is a broken roof and one room is arranged in the attic, the racks are located on the sides, leaving free space for movement. If there are supposed to be two rooms, the racks are located in the center and on the sides.
The location of the rack depending on the length of the roof is shown in the figure.
- Strut. Serves as a support for the stand.
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.
- Sill. Its purpose is to serve as a support for the rack and a place for attaching the strut.
- Lathing. Designed for movement during construction work and fixing roofing material. Installed perpendicular to the rafter legs.
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.
Selection of material for rafters
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.
Calculation of the rafter system of a gable roof
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.
1. Calculation of the load on the rafter system
The load on the rafters can be of three types:
- Constant loads. Their action will always be felt by the rafter system. Such loads include the weight of the roof, sheathing, insulation, films, additional roofing elements, finishing materials for. The weight of the roof is the sum of the weight of all its constituent elements; such a load is easier to take into account. On average, the constant load on the rafters is 40-45 kg/sq.m.
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.
- Variable loads. They act at different times and with different strengths. Such loads include: wind load and its strength, snow load, precipitation intensity.
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 using 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.
2. Calculation of snow load on the roof
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.
- Special loads. Such loads are taken into account in places with high seismic activity, tornadoes, and storm winds. For our latitudes, it is enough to make a safety margin.
Nuance. The simultaneous action of many factors causes a synergy effect. This is worth considering (see photo).
Assessment of the condition and load-bearing capacity of walls and foundations
It should be borne in mind that the roof has significant weight, which can cause damage to the rest of the building.
Determining the roof configuration:
- simple symmetrical;
- simple asymmetrical;
- broken line
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.
- soft roof - 5-20°;
- metal tiles, slate, corrugated sheets, ondulin - 20-45°.
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°.
5. Calculation of rafter pitch
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 beam 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.
7. Calculation of the rafter cross-section
The cross-section of the rafters of a gable roof depends on several factors:
- loads, we have already written about it;
- type of material used. For example, a log can withstand one load, timber - another, laminated timber - a third;
- rafter leg lengths;
- the type of wood used in construction;
- distances between rafters (rafter pitch).
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.
Rafter cross-section - table
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:
- thickness (section) of the Mauerlat - 10x10 or 15x15 cm;
- the thickness of the rafter leg and tie is 10x15 or 10x20 cm. Sometimes a beam of 5x15 or 5x20 cm is used;
- run and strut - 5x15 or 5x20. Depending on the width of the foot;
- stand - 10x10 or 10x15;
- bench - 5x10 or 5x15 (depending on the width of the rack);
- thickness (section) of the roof sheathing - 2x10, 2.5x15 (depending on the roofing material).
Types of gable roof 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.
Hanging rafters
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.
Layered rafters
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.
Combined
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.
Installation of a gable roof rafter system
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.
1. Attaching the Mauerlat to the wall
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.
How to connect the Mauerlat?
The beams are cut only at an angle of 90°. Connections are made using bolts. Nails, wire, and wooden dowels are not used.
How to attach the Mauerlat?
The Mauerlat is installed at the top of the wall. The installation technology provides several ways to attach the Mauerlat:
- strictly in the center of the load-bearing wall;
- with a shift to one side.
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.
Methods for attaching the Mauerlat to the wall and rafters
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.
2. Manufacturing of trusses or pairs
Installation is carried out in two ways:
- installation of beams directly on the roof. It is not used often, since it is problematic to carry out all the work, measurements, and trimming at height. But it allows you to completely do the installation yourself;
- assembly on the ground. That is, individual elements (triangles or pairs) for the rafter system can be assembled below and then raised to the roof. The advantage of such a system is faster performance of high-altitude work. The disadvantage is that the weight of the assembled truss structure can be significant. To lift it you will need special equipment.
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.
3. Installation of rafter legs
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.
4. Installing the ridge of a gable roof
The roof ridge unit is made by connecting the rafter legs at the top.
Roof ridge structure:
- Method without using a support beam (see figure).
- Method using rafter beams. Timber is needed for large roofs. In the future, it can become a support for the rack.
- Method of laying on timber.
- A more modern version of making a ridge knot can be considered the method shown in the photo.
- Cutting method.
After the rafter system is installed, we perform major fastening of all structural elements.
5. Installation of roof sheathing
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:
- for metal tiles - 350 mm (the distance between the two lower boards of the sheathing should be 300 mm).
- for corrugated sheets and slate - 440 mm.
- We lay a continuous sheathing under the soft roof.
Rafter system of a gable roof with an attic - video:
Conclusion
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.
Making a residential building is a complex and lengthy process. It contains many pitfalls that await the novice builder at every stage. An important part of any house is the roof. We will dwell on the types of roofs and roofing materials separately in another article. Today we’ll talk about how to make rafters for a gable (gable) roof, and we’ll touch on the topic of calculation and selection of material.
Design Features
The traditional option for Rus' is a gable roof. Slopes are flat parts of the roof that have a constant slope to the horizon. The angle of inclination must be accurately calculated; it can vary from 10-15 to 60-80 degrees. Failure to comply with the specified parameters leads to negative consequences:
- As the angle of inclination increases upward, the length of the rafters changes and, accordingly, the height of the roof. This, in turn, leads to an increase in the load on the house frame and fastenings. In addition, due to the high windage, the sharp roof is highly susceptible to wind. In regions where strong wind gusts prevail, such a structure may collapse and cause harm to human health.
- Installing a roof with a slope of less than 10 degrees is also not recommended: the roof will not withstand the pressure of snow accumulating on its surface. In places with heavy rainfall, the optimal slope angle is 45-60 degrees.
Thus, the correct slope will ensure durability and safety of the gable roof. The basis for calculating this indicator are the corresponding tables of wind and snow loads for a particular region.
In recent years, a device called an attic has become popular for private housing construction. This gable design allows you to organize a full-fledged living space of large area and height in the under-roof space, as well as arrange a spacious balcony on the side of one of the facades of the house.
At the same time, trusses for attic structures are more complex and massive and require careful calculation and fastening.
Roof structure: getting to know the main elements
Structurally, a gable roof is represented by a rigid wooden frame, which is mainly made from softwood lumber of a certain section. The specific size of the frame elements and the fastening pitch are calculated based on the dimensions of the house and the load on the roof.
The main components of a gable roof include:
Types of rafter systems: choosing the right one
Gable roofs, based on the type of rafter system, are divided into layered and hanging. The first involves the installation of racks and a common beam attached to the mauerlat, the second is characterized by the presence of a tie between the base of the rafters.
Hanging rafters are used for small buildings without internal load-bearing walls, layered rafters are used for buildings with a load-bearing middle partition. The choice of rafter system depends on the size of the house, the expected angle of inclination of the slope and roofing materials, which together determine the amount of load on the entire structure. Only a professional builder can choose the right type of system and make an accurate calculation.
Roof parameters
Immediately before the start of construction work, at the design stage, the optimal roof parameters are calculated: the angle of inclination of the slopes, cross-sectional dimensions, installation pitch frequency and rafter layout.
Wind and snow loads in different regions of our country are uneven. SNiP 2.01.07-85 will help you calculate them for a specific area. At the same time, experts recommend making a certain safety margin for the roof frame, taking into account possible peak loads.
In addition, there is also a constant force on the rafter system - the pressure of the roofing material. The table shows the weight of popular coatings per 1 m2 of surface.
Different types of materials have different requirements for the optimal slope angle of the slopes. This aspect also needs to be taken into account when designing the roof.
Roof angle depending on material
Equally important is the calculation of the installation step and fastening of the rafters to the Mauerlat, that is, the distance between adjacent trusses. Typically this value is 0.6-1 m. An upward change in this indicator leads to an increase in the load on the rafters and, as a consequence, an increase in their cross-sectional area. It is necessary to install the supports so that the fastening step is the same for all pairs.
The cross-section of the rafters directly depends on the above indicators. By the way, the strength characteristics of wood of different species differ (glued laminated timber has the greatest strength). Here is a table for calculating the cross-sectional dimensions for rafters made of coniferous varieties, depending on the installation pitch and the length of the support.
Preparation and processing of lumber for the frame
Installation of the rafter system is not difficult to perform if you have at hand a roof drawing, the necessary materials and have experience working with carpentry and carpentry tools.
When choosing wood for a roof frame, preference should be given to pre-dried boards without rot and with a minimum number of knots.
If desired, rafters, racks, mauerlat and other elements can be pre-planed. Treatment with antiseptic compounds and fire retardants in two layers is required.
Applying liquid mordants with a brush or roller is difficult and time consuming. It is much more effective to use dipping.
To do this, a trough is made from edged boards with a cross-section of 200x25 and a length of 6 meters, inside which a plastic film is spread in one piece and fixed at the edges with a construction stapler.
Several canisters of antiseptic are poured into the resulting container, lumber is immersed in the solution and, thus, the treatment is carried out at one time. According to the instructions, it is prohibited to mix compositions with different effects to speed up impregnation.
Assembly of roof trusses
Builders do not have a consensus on where to assemble rafter trusses. Some make them on the ground and lift the finished structures up for installation, while others prefer to do all the work on the site of the future roof. Both methods are valid. The first option is safer, the second is less expensive, since lifting large trusses will require a crane, which is associated with additional costs.
Regardless of where the work is performed, the first step is to prepare templates for sawing the ends of parts at a certain angle or the required shape. Taking into account the specified parameters, the required length of lumber is measured and cut with a carpenter's hacksaw or circular saw.
The next rafter pair is attached taking into account the installation step. In order not to measure the required value each time, pieces of boards of a given length are prepared in advance and fixed to the mauerlat between the trusses. After installing all the rafters, the upper part of the supports is connected with a ridge girder. To increase the strength of the structure, longitudinal bars are mounted on the sides.
This completes the installation of the rafters. All that remains is to sheathe the outside of the trusses with lathing made of unedged boards, bars or sheets of plywood and OSB, laying insulation and vapor barrier. Read more about this in other articles.
If you decide to build a house or a small outbuilding, then you need to protect the building from moisture, and for this you need to build a roof. The design of the roof can be different, but in most cases a gable roof is used. Proven for centuries, it is easy to install and compatible with any type of roofing. Its installation is carried out on the sheathing, and it is pressed onto the rafters. In order for the roof to last for a long time, you need to know exactly how to correctly install the rafters on the roof.
The most actively used material from which rafters are made is wood. Usually, blanks made from coniferous wood are used, since the structure impregnated with resin allows the wood to retain its qualities for a long time and is light in weight. When choosing a material, it is advisable to avoid boards with knots and large cracks. It is not recommended to use freshly sawn boards and beams to make a rafter frame; the wood should be dried.
The rafters need to be assembled into a triangular truss; this design allows for optimal rigidity, and it affects the load-bearing capacity of the entire building.
Components of the truss structure
Rafter systems are divided into two types:
- Hanging. They are used if the width of the wall along the front does not reach 10 m. When using a hanging system, the rafters rest on the side walls, and they are connected using a tie to equalize the load.
- Layered. They are used in the presence of load-bearing walls, if the width of the wall along the gable is more than 10 m. In order to strengthen the rafter system, a vertical beam is placed in the middle, through which the entire load of the wall and the floor are distributed.
The installation of the rafter system must begin with the Mauerlat. The place for its installation is planned during the construction of the walls. To do this, you need to lay out a ledge on the outside of the wall, and lay the Mauerlat at the inner edge. To attach it use:
- binding wire;
- anchor bolts;
- wood plugs;
- fittings, cut into pieces.
The intended location for laying the Mauerlat must be waterproofed, and the timber must be treated with an antiseptic. To reduce the number of joints, the timber must be chosen as long as possible. If suddenly the length of the beam turns out to be short, you need to make an oblique cut, and then connect the two parts using self-tapping screws, nails and staples. The length of the cut should be up to 1 meter.
To make rafter legs, you need to cut the boards to the required length. A beam measuring 50 × 20 is well suited for this. The connection should not be located in the middle; the required offset is 1/3 of the entire length of the rafters.
For smaller buildings, roof trusses are easier to assemble on the ground and then raise to the roof.
You need to start installing the rafters from the outer gable trusses. The building level controls the verticality of their installation. And for precise installation of intermediate trusses, it is advisable to tension the cord from above and below.
The rafter legs are installed in increments of 0.6 to 1.2 m, and the trusses are secured to each other with a temporary clamp.
After installing all the trusses, they are fastened with a board in the upper chord, and the clamps are removed.
If the span is more than 6 m, and there is a load-bearing wall in the center of the house, then the rafters need to be installed differently. Supports are installed in the center, and a ridge beam is mounted on them. The rafters are attached to it alternately. Installation, as usual, begins with the outer supports. It is necessary to pull a cord between them to install the remaining rafters in the same plane. An additional beam can be installed between the internal supports; it will strengthen the ridge beam.
Having decided on the angle of inclination and height of the roof, you can make a template to facilitate marking work. All rafters are the same length, so you can cut down on the ground and assemble the prepared structure at the top.
If the rafters are installed without a central purlin, then they can be overlapped together. The upper points must be fixed rigidly, and a crossbar must be installed below.
Having become familiar with how to install rafters on a small building, you can do this work correctly yourself.
Is it time to install a roof? The very first thing you need to do is install the rafter system. This work is very important and complex, and therefore you need to carefully read our advice.
A little theory - what do you need to know about the rafter system?
First of all, we need to talk about the types of rafter systems and their characteristics. So, this system consists of the following elements:
- rafter legs;
- racks and vertical supports;
- struts;
- puffs - an element that connects the rafter legs.
You should also distinguish between rafters by type. Rafter systems are divided into:
- Layered. They should be used if the building has internal partitions or other supports. In this case, the “legs” of the structure must rest on both the external and internal walls.
- Hanging - in which the “legs” of the structure rest only on the outer walls. A distinctive feature of this design is that its construction requires tightening due to high thrust loads.
Several important technical characteristics
When choosing a method for installing rafters, it is necessary to assess the complexity of the work and the weight of the future structure. If the assembled product is lightweight or you can bring special lifting equipment to the site, then it is best to assemble the rafters on the ground, and then lift it to the roof of the building, where you can do all the other work. If the structure is heavy, then it will have to be assembled directly on the roof - this is easier and safer.
It is very important to connect the upper parts of the rafters correctly. This work can be done using several methods. First of all, butt jointing, when cuts are made on the opposite rafter legs at the required angle. Next, the rafters need to be joined along the resulting ends and secured with several nails. For a safer connection, secure the products with a metal pad.
You can attach the rafter legs with an overlap - in this case, the structural elements touch each other with planes. If you are going to make a rafter system in a house with fronts that are made of logs, then the rafters must be installed on the walls using the sliding fastening method. Thanks to this, you will be able to avoid deformation of the roof in the event of shrinkage of the house.
If you decide to use this method, then you need to keep in mind that it is quite difficult to do it yourself. Fastening is done as follows: the “legs” of the rafters must be placed with a gap, fastening them together using a specialized movable metal element. Now we proceed to the actual construction of the rafter system with our own hands.
Mauerlat - what is it and what is it for?
The construction of the rafter system must begin with the installation of the Mauerlat - this is the basis for the future structure. Mauerlat is a log or beam that is fastened along the entire perimeter of the external walls. Undoubtedly, it is possible to make a structure without a Mauerlat, but building such a structure with your own hands will be quite difficult and even risky. It is very important to follow all the recommendations exactly so that the base for the rafter system 100% fulfills the functions assigned to it.
Important Tips:
- Before laying the Mauerlat, you need to insulate the walls using a suitable waterproof material. To save money, you can put several layers of roofing felt.
- Installation of logs is carried out on a reinforced belt with a slight indentation from the edges of the walls.
- It is best to choose antiseptic wood logs with a cross section of 10*15 cm.
To make it easier to do the work yourself, the beams must first be laid out from one front to the other along the entire length of the wall. After this, you can take measurements: lay out the beams level, making sure the distance between them is even. Next you can attach the beams to the walls. As we have already said, it is preferable to carry out installation on a reinforced belt, using anchor bolts as fastening products - it is better to fasten them when pouring the reinforced belt. Also, do not forget to drill holes in the beam itself.
Important: if you want to achieve a perfectly even position of the bolts, before pouring the “belt”, attach the board to the bolts and give the fasteners a vertical position using a square.
We place the base prepared with our own hands on stands consisting of planks, after which we carefully lower the beams onto the bolts, removing a plank each time. Finally, screw the washer onto the bolt. Now it’s time to learn how to make a rafter system with your own hands.
Do-it-yourself rafter system installation
We have already talked about installing the Mauerlat. Now it’s time to move on to the main point of installing the rafter system - the installation of floor beams and ridge beams. But first things first. Floor beams are beams with a cross section of 20*10 or 15*10 cm. The length of the products should be such that when laid on the walls, the beams form a projection that will correspond to the width of the cornice.
In simple terms, the beams must extend beyond the walls at a certain distance. The bars are installed in one direction, leaving an equal distance between them.
To avoid errors while performing work, you should follow a clear sequence of actions:
- We install the boards with our own hands, retreating from the edge of the walls by an average of half a meter.
- We stretch a cord between the beams - it will serve as a kind of “beacon” for installing the next beams.
- The distance between the “legs” of the structure must be selected based on the cross-section of the rafters. So, if you decide to choose “floor” boards measuring 5*15 cm, then the step should be approximately 60 cm. It is worth noting that this will greatly simplify all further work. And all thanks to the fact that the width is most often 60 cm, which means there will be no need to trim anything.
- We proceed to the installation of transverse beams, one part of which should be in contact with the outer beam, and the second part should extend beyond the walls. The gap between such jumpers should be about 1 m.
- We attract the beams to the base (mauerlat) using nails, you can also use self-tapping screws and steel corners (for reliability).
To make your work as convenient as possible during the construction of the rafter system with your own hands, lay ordinary boards on the beams.
Now it's time to talk about installing ridge beams. This stage consists of several steps:
- Installation of auxiliary racks, which are U-shaped struts made of wood. Professional experts advise that the height of the struts be equal to the height of the first floor.
- We assemble the racks at opposite ends of the structure and install intermediate beams, maintaining a step of 2.5 meters.
- After installing the racks, we place a ridge beam on top (a wooden board with a cross-section of 5*20 cm). Secure the structure with self-tapping screws.
Since the rafters must be the same length, it is advisable to make a template in advance to determine the length. To do this, take one board measuring 2.5*15 cm, apply it to the beam and to the ridge, and put marks at the points of contact and saw off the unnecessary part - you can make blanks using this template. However, it is worth noting that not everyone can achieve perfect evenness, so be prepared for the fact that during the installation process you will have to use a saw more than once.
If you neglect this advice, the ridge may bend, which may make the structure not so reliable.
After you have installed the rafter system, you need to waterproof it, create a sheathing and cover the structure with roofing material. Now you know how to assemble the rafter system - the roof is almost ready. We hope our tips will help even you do the job yourself.
