How to secure rafters on a gable roof? Gable roof truss system: device, installation, drawings and diagrams, photos and videos Scheme of a gable roof truss system.

How to make a rafter system with your own hands? What are the options for fastening rafters? From the article you will learn how to arrange hanging or layered rafters and in what cases they are used. We will give examples of techniques used by professionals when creating a gable rafter system.

In previous articles we talked about the rafter system and the features of a gable roof. In this article you will find step by step guides for DIY installation. In order to follow the manual exactly, the necessary terms will be given, without understanding which correct installation will be impossible.

Construction of the rafter system. Nuances

Gable roofs differ fundamentally only in the method of constructing the rafters - hanging or layered - which directly depends on the length of the span. In this guide, we'll cover both options and use a set of basic terms.

Attic height- the distance from the top of the wall (the place where the rafters support the wall), either from the upper plane of the Mauerlat, or from the upper plane of the floor beams to the top point of the ridge of the gable roof.

Cutting- mating (connection) of wooden parts by creating an anchor and a seat, or a coupling or stop from the body of the wood of the element itself. Basically, the cutting points are reinforced with various anchors - wooden chop, threaded rod (stud), self-tapping screws, turboprops.

1 — roof overhang; 2 - wall; 3 - beam; 4 - lying down; 5 — intermediate stand; 6 - attic height; 7 — central post or “headstock”; 8 - rafter; 9 - working part of the rafters; 10 - skate; 11 - projection of the working part of the rafter

Other basic terms are given in previous articles.

Their function in the supporting area can significantly influence the design of the rafters. There are three types of supports.

1. Support without cutting or cutting. It is used only on temporary, auxiliary buildings, or for roofs that do not bear significant loads. In such cases, a powerful wedge is installed according to size.

Support without cutting: 1 - rafters; 2 - wedge; 3 - beam; 4 — armored belt; 5 - Mauerlat

2. Full cut or end notch support. The rafters rest on a beam or mauerlat over the area of ​​the entire cut or on the end tooth. In this case, to create a roof overhang, the filly is extended or an additional counter-lattice is installed. Typically, this method is used when the length of the slope is approximately equal to the length of one unit of material (board, beam) adopted for the rafter leg (usually 5-6 m). This is done in order not to splice the rafters in the working part.

Support on a full cut or end tooth: 1 - beam; 2 - end tooth; 3 - wedge; 4 — cutting; 5 — studs with nuts; 6 - rafters

3. Support on the intermediate notch. The rafter leg remains solid from the ridge to the edge of the roof, i.e. the outermost part of the rafter leg performs the function of an overhang. The most common option for slope lengths of more than 5 meters. In this case, merging of the rafters is inevitable. The notch provides an additional hook for rigidity, and the sufficient length of the rafter leg guarantees the optimal length of the roof overhang. The depth of the cut into the rafter leg should not exceed 40% of its height.

Support on the intermediate notch: 1 - Mauerlat; 2 - support bar; 3 — studs with nuts; 4 - beam; 5 - wedge; 6 - rafters

To create a gable rafter system with your own hands, you will need a set of carpenter’s tools:

  1. Power tools - a circular saw, jigsaw, powerful drill with a set of “feathers” for wood.
  2. Hand tool- saws, axe, hammer, sledgehammer, set of chisels, locksmith's keys.
  3. Measuring tools - tape measures, levels, hydraulic level, rule, cord, plumb line.

Preparation

In preparation for work, it is necessary to create drawings or sketches. To do this, you need to decide on the principle of the roof structure and draw specific components:

  1. Rafter leg support unit. Here it is necessary to take into account local conditions - the material of the walls and the distance between them.
  2. Horse. This is an equally important area and the method of connecting the rafters must be chosen in advance, based on the dimensions of the projection of the rafters, the span and the thickness of the beams.
  3. Selection of rafter system material. If units are selected that provide a through tie across the width, then the thickness of the rafter leg must be at least 60 mm. If rafters of such power are not needed, select another option for supporting the rafters (for example, “in the overlay”).

Notch on the overlay: 1 - notch on the side of the beam; 2 — departure; 3 — studs with nuts; 4 - top view

Hanging rafters for small spans

The method of constructing a rafter system without intermediate supports is applicable only in the case of a small span - up to 6 meters. As mentioned in the previous article, the tightening in this case is the floor beam or rafter beam. We will consider two options for installing rafters.

Option 1. With subfloor

This method is convenient if it is possible to arrange a subfloor along the floor beams.

Operating procedure:

  1. Arrange a subfloor from unedged boards and available materials.
  2. Mark the mauerlat or beams - step, cutting locations. Pull the cord over the future skate. Be sure to check the perimeter.
  3. Apply rafter material to the ceiling.
  4. Find by location best option rafter fastenings.
  5. Make two roof trusses*.
  6. Install the outermost trusses using temporary spacers (lighthouse trusses).
  7. Check for correct installation and compliance with levels and tolerances.
  8. Make and install the remaining trusses according to the dimensions of the lighthouse trusses using screws and nails. At the same time, it should remain possible to correct the pitch and size.
  9. After installing all trusses, compliance with levels and tolerances should be checked again.
  10. The final fastening of the rafter system is the installation of ties, brackets, turboprops and other elements provided for by the project.

* WITH tropile farm- one complete element of the rafter system.

Option 2. Without subfloor

In this case, the ceiling is not arranged; the floor space is combined with the attic.

Operating procedure:

  1. Carefully measure the dimensions at the installation location.
  2. Based on local dimensions and conditions, choose the method of supporting the rafter leg and tying the ridge, and the option of cutting the slope.
  3. Create a polygon that repeats the dimensions of the span and the projection of the rafters. On a horizontal grid or workbench, install a system of stops that guides the board to the design position in the truss.
  4. Assemble one experimental roof truss.
  5. Lift the truss to the installation site and install it on temporary fastenings.
  6. Choose a cutting method locally and make a cutting for the experimental farm.
  7. If necessary, correct the dimensions, angle and design.
  8. After achieving a high-quality landing, finally fix the components of the truss and lower it to the landfill.
  9. Adjust the stops of the polygon (workbench) according to the template.
  10. Make required amount roof trusses using an experimental truss as a template.
  11. Make notches or seats at support points.
  12. Install and secure a number of roof trusses in the designed position.

Often the project involves combining space over large spans - up to 9 meters. In this case, hanging rafters with a crossbar are also required. Such projects must take into account three points:

  1. The rafter leg must be made of a board with a thickness of at least 75 mm and a width of 200-250 mm.
  2. All notches, support points, and joints must be tightened with a through threaded tie (stud) with a diameter of at least 12 mm. It is advisable to cover the joints of the planes with wood glue.
  3. The level of installation of the truss crossbar (tightening) is from 1/2 to 2/3 of the attic height.

Otherwise, the rafter installation technology repeats the described options.

Layered rafters

The installation of this type of roof will require advanced carpenter skills. This type of rafters is suitable for large spans and when attic space planned to be used separately. Before installing the rafters themselves, additional preparation is required:

  1. Under the vertical supports, you should install a bench - a board or timber with a thickness of at least 60 mm.
  2. Since roof trusses have a larger number of elements, they are assembled only locally. This may require scaffolding.
  3. Mauerlat is a mandatory element of the system. It must be secured to the armored belt with anchors and connected at the corners with half-tree notches.

Board thickness for rafter legs and intermediate supports (if any) - at least 50 mm with a width of 150 mm. It is advisable to make the central support (headstock) from 100x100 timber.

Installation of rafters. Operating procedure:

  1. Install the Mauerlat. Usually it is mounted on the inner plane of load-bearing walls. Based on the fact that the thickness of the wall is obviously thicker than the width of the Mauerlat, the distance to the edge of the wall will allow it to be insulated. Docking of elements is only through a notch with fixation with brackets or ties.
  2. Place a row of central supports on the bed, securing them into the designed position with temporary rods (rail). Attach temporary or permanent ridge purlin to the tops.
  3. Temporarily fix the rafter board in the desired design position. At the same time, it does not need to be trimmed or trimmed in advance.
  4. Adjust the ridge run.
  5. Mark the seats on the headstock, rafter leg and mauerlat and make cuts.
  6. Install the rafter leg into the seats, measure and check for correct installation. If necessary, adjust the seats.
  7. Make cuts and tie-ins for the entire row of rafters of one slope, observing the step.
  8. Make notches and mortises on the rafter board for one slope (wing) according to the template.
  9. Install a row of slope rafters on temporary fasteners (screws, corners).
  10. Fit the opposite roof slope in the same way.
  11. Check for correct installation and tolerances. Secure the trusses with transverse lathing.
  12. Place the beds under the intermediate supports (if any) and the supports themselves.
  13. Mark and trim the roof slope in place and install a wind board if necessary.

Option for the rafter system: 1 - wall; 2 - Mauerlat; 3 - lying down; 4 - stand; 5 - rafter; 6 - “grandmother”; 7 - run; 8 - ridge run; 9 - intermediate cut; 10 - half-tree cutting; 11 — studs with nuts

Rafter pitch

When selecting, follow the rule: The pitch of the rafters should not exceed ten times the thickness of the rafter leg.

This rule also applies in reverse side: The thickness of the rafter board should not be less than 1/10 of the rafter pitch (along the axes).

The most popular step - 600 mm between the internal planes of the sinus - is due to standard width slabs (sheets) of mineral wool insulation, which fits into such a cavity without trimming. The thickness of the board should be 60 mm.

Rafter length

  • c 2 = a 2 + b 2, where
  • a - rafter projection
  • b - attic height
  • c - length of the working part of the rafter leg

However, this does not take into account the roof overhang. Therefore, it is recommended to adjust the length of the rafter row to the location, trimming the ends after installation. This makes it possible to make the ends even. The optimal structural overhang of the roof is 600 mm.

When creating roof rafters with your own hands, remember the dangers of unreasonable savings. The rafter system, like load-bearing walls and the foundation is an irreplaceable element of the building. This means that replacing it will require complete dismantling. Typically this occurs during reconstruction or overhaul. If the rules described in the article are not followed, this procedure may be required after 2-3 years.

Erection of the roof is one of the most critical stages of construction. From the reliability of the “umbrella” from above, from its resistance to precipitation and any external influences, the durability of the building itself and the level of comfort of living in it directly depend.

Of all the variety of roof designs, the gable roof can be considered one of the most popular, simply due to relative simplicity its construction. However, behind this “simplicity” lies a lot of different nuances, the need to carry out certain calculations and follow technological rules. However, this publication has a main objective: to show that installing rafters gable roof with your own hands is a completely doable task, even for a novice builder.

Let's go through all the stages of the process of installing rafters for such a roof, from the basics of preliminary design to an example of practical implementation.

General structure of a gable roof

Basic Concepts

Structural elements of a gable roof truss system


Let's say right away that this scheme, of course, cannot reflect the entire possible variety of designs, but the main parts and assemblies are shown quite clearly.

1 - Mauerlat. This is a board or beam that is rigidly attached to the upper end of the external load-bearing walls of the building. Its purpose is to uniformly distribute the load from the entire roof system onto the walls of the house, creating conditions for reliable fastening of the rafter legs at their lower support point.

2 – rafter legs installed in pairs. They become the main load-bearing parts of the entire roof system - it is the rafters that determine the steepness of the slopes and will be the basis for attaching the sheathing, roofing, and if the roof is planned to be insulated, then the entire thermal insulation “pie”.

For the manufacture of rafter legs they are used quality boards or timber, you can also use round timber. The cross-section of lumber, which will be sufficient to guarantee withstand all possible loads, will be discussed below.

The rafters can end at the mauerlat, but more often they extend beyond the perimeter of the walls of the house, forming a cornice overhang. However, lighter parts can also be used for this - the so-called “fillies”, which are used to extend the rafter legs to the required overhang width.


To form the eaves overhang, the rafters are extended with “fillies”

3 - ridge run. It could be a beam, a board, or even a composite structure. The purlin runs along the entire line of the ridge and serves to reliably connect the upper points of paired rafter legs, connecting all rafter pairs in order to impart overall rigidity to the entire roof structure. IN various options For roofs, this purlin can be rigidly supported by racks, or linked only to the connection node of the rafter legs.

4 – tightening (contracts, crossbars). Horizontal reinforcement parts of the system, additionally connecting paired rafter legs to each other. Several puffs located at different heights can be used.

5 – floor beams, which will serve as the basis for installing the floor in the attic and the ceiling on the side of the room.

6 - and this beam simultaneously serves as a bench. This is a beam that runs along the entire length of the roof, which serves as a support for installing additional reinforcement parts for the rafter system. The beam can be installed as shown in the figure (like a floor beam), or it can be rigidly laid on a permanent partition inside the building.

7 – racks (headstocks) – additional vertical supports of the rafter legs, preventing them from bending under the influence of external loads. The racks at the top can rest against the rafters themselves, or into an additional purlin that longitudinally connects the rafter legs at a certain height.


8 – struts. Often, when the rafter legs are long, their load-bearing capacity is not enough, and reinforcement with racks alone does not provide the necessary strength. In these cases, diagonal reinforcing elements are used, resting on the bottom, creating additional point rafter supports. The number of struts and their installation location may vary on roofs varying degrees difficulties.

Some differences between the hanging and layered gable roof systems

Gable roofs can be divided into two types of structures - with layers and hanging rafters. In addition, they are widely used combined systems, which combine both principles of construction. What is the fundamental difference?

Layered rafter system

This rafter system design is characterized by the presence of support on the internal main partition in the building. At the upper end of this partition, a bench is mounted on which the drains supporting the ridge girder rest. Thus, the rafter legs are “leaned” onto vertical support, which makes the entire system as durable as possible.


This type of scheme is the most popular because of its reliability and relative ease of implementation. If it is possible to create an additional point of support in the center, then why not take advantage of it? True, if it is planned to place living space in the attic, then vertical racks can sometimes become a hindrance. However, their presence is also sometimes “played up”, using, for example, to install an internal light partition.

Depending on the number and placement of internal partitions, the design of the layered rafter system may vary. Some examples are shown in the illustration below:


Fragment “a” shows the simplest option, which, by the way, on short rafter lengths (up to 5 meters) may not even have the shown struts - a row of central posts under ridge run

As the width of the building increases, the system naturally becomes more complex, and additional reinforcing elements appear - tie rods and struts (fragment “b”).

Fragment “c” clearly demonstrates that the internal main wall does not have to be located exactly in the center, under the ridge. An option as shown in the illustration is also quite possible, but with the condition that the displacement of the bed relative to the ridge does not exceed one meter.

Finally, fragment "d" shows how the rafter system in a building can be supported big size, but having two capital partitions inside. The distance between such parallel beams can reach up to a third of the width of the building.

Hanging rafter system

Graphically, this roof diagram can be depicted something like this:


It is immediately noticeable that the rafters rest only on the lower part, and then are connected to each other at the ridge. There is no additional support in the center, that is, the rafter legs seem to “hang”, which determines the name of such a system. This feature imposes certain restrictions on the use of hanging rafters - usually this scheme is practiced when the distance between the load-bearing walls to which the Mauerlat is attached is no more than 7 meters. The installed puffs only partially relieve the load from the external walls.

The illustration below shows several options hanging system. However, some of them can rather be classified as combined.


Fragment “d” - hanging rafters are connected to each other by a tie at the level of the mauerlat or fixed to a powerful floor beam, forming a triangle with it. There are no other reinforcing parts. A similar scheme is acceptable with a distance between walls of up to 6 meters.

Option “w” is for a house of the same size (up to 6 meters). The tie (bolt) in this case is shifted upward, and is often used for lining the attic ceiling.

Options “e” and “z” are designed for a span between walls of up to 9 meters. Multiple tie-downs may be used (or a top tie-down in combination with a bottom joist). Another approach is to install racks under the ridge girder, similar to the layered system. Only, as the lower point of support, it is not the support on the main partition that is used, but the racks are supported by a tie or a floor beam. It is already difficult to call this option purely “hanging”, since here it is clearly a combination of parts from both designs.

To an even greater extent, this combination of two schemes is expressed in the “and” option, which is designed for large spans, from 9 to 14 meters. Here, in addition to the headstock, diagonal struts are also used. Often such trusses are assembled on the ground, and only then they are lifted and installed in place, connected to each other, thereby forming the entire roof frame.

So, when preparing for the construction of a gable roof, it is necessary to study the principles of the design of a particular system, evaluate their advantages and disadvantages, choose the optimal one for your conditions and draw up a graphical working diagram. You will also need it when purchasing required material, and for the production themselves installation work. However, drawing up a drawing must still be preceded by some calculations.

Calculation of the basic parameters of a gable roof rafter system

Let's take another look at schematic diagram gable roof installations in order to highlight those parameters that will need to be calculated.


So, in the calculation process we will need to decide on the following values.

The initial data is the length of the side of the house along the gable part (highlighted in blue - F), and the length of the house along the ridge ( purple– D). It is assumed that the owners have already decided in advance on the type of roofing - since there will be certain restrictions on the steepness of the roof slopes. (angle a).

  • The height of the ridge above the plane of the Mauerlat (H – green color), or, conversely, decide on the angle of the slope, starting from the planned height of the ridge.
  • Length of rafter leg ( Blue colour– L), and, if necessary, extending the rafters to form a cornice overhang of the required width (l).
  • Calculate the total loads falling on the rafter system in order to determine the optimal cross-section of lumber for the manufacture of rafters, the pitch of their installation (red color - S) and the permissible length of spans between support points. All these parameters are closely interconnected.
  • Once you have these calculated values ​​in hand, it is no longer difficult to draw up a graphical diagram, determine the need and optimal location of reinforcement elements, and calculate the amount of material for their manufacture.

Chainsaw prices

chainsaw

We calculate the steepness of the slope and the height of the ridge

The steepness of the slopes can be determined by the owners according to various evaluation criteria:

  • For purely aesthetic reasons - when “at the forefront” becomes appearance buildings. Many people like roofs with a high ridge, but we must not forget that the wind load on such a roof increases sharply. And there will be immeasurably more materials needed to make a high roof. At the same time, on steep slopes the snow load is reduced to almost zero - it is possible that for “snowy” regions this assessment parameter may become decisive.
  • For reasons beneficial use attic space. With a gable roof scheme, in order to achieve the maximum area of ​​the attic, it is necessary to build slopes with a very large steepness, that is, with the same consequences as mentioned above.

  • Finally, there may be a completely opposite approach - for reasons of economy, make a roof structure with minimum height in a skate. But in this case you will have to focus on the minimum permissible slope angles for specific type roofing covering. Reducing the slope below the values ​​recommended by the manufacturer means “planting a bomb” in your roof, both for reasons of its strength and durability, and from the standpoint of the waterproofing qualities of the coating.

Calculating the height of the ridge above the plane of the ceiling (mauerlat) is not difficult. The vast majority of components of any roofing system are based on a triangle, which, in turn, obeys strict geometric (more precisely, trigonometric) laws.

So, in our case, the width of the roof along the gable line is known. If the roof is symmetrical, then the ridge will be placed exactly in the middle, and for calculations you can simply divide the width F by two (the base of the triangle f =F/2). For asymmetrical slopes, you will have to project the top of the ridge onto line F, and measure the distances f1 and f2 from it to the edge of the triangle (to the Mauerlat) on each side. Naturally, in this case the slope of the slopes will be different.

N =f×tga

In order not to force the reader to look for tangent values ​​and carry out calculations manually, below is a calculator in which the necessary tabular values ​​have already been entered.

Properly designed and assembled according to technology, the roof serves as a barrier preventing cold air and moisture from entering the house. From the outside, with the naked eye we see only a small part of the structure - the roofing. But the roof frame, which is the most an important component, performs the main supporting functions and takes on the effects of wind and snow loads.

To prevent it from deforming as a result of operation, it is necessary to correctly calculate the cross-sectional size of its elements and determine the distance between them, taking into account the weight roofing material, slope and climatic conditions. In this article we will tell you what the rafter system of a gable roof of a house is, what it consists of, how it is designed and assembled with your own hands.

A rafter system for a gable roof of a house is a system of interconnected supporting elements that together make up the frame of the structure.

It is made of wood or metal in accordance with the calculation of the loads that will affect them during operation. The roof rafter frame performs the following functions:

  1. Gives the roof slopes the necessary slope. The traditional shape in the form of an equilateral rectangle of a gable roof is given by the rafter frame, which forms the slope between the base of the roof and its ridge. The angled surface allows snow and water to slide freely off the slope.
  2. Distributes the load from weight roofing pie . The weight of the roofing pie, taking into account the snow load, can reach up to 500 kg/m2, so the gable roof is subject to intense loads, especially in winter period. The rafters of a gable roof evenly distribute the weight that rests on them, and then transfer the load to the load-bearing walls and foundation of the house.
  3. Serves as a basis for attaching thermal insulation and roofing material. The rafter frame of the roof serves as a kind of skeleton of the structure around which its “body” is built. Thermal insulation should be installed between the rafter legs, and a roofing covering should be fixed to the sheathing, which protects against moisture penetration.

Please note that the design of a gable roof truss system is quite complex to design and assemble, especially if the craftsman lacks experience. After all, in order for it to be able to withstand intense loads, you need to correctly calculate the cross-section of the rafters and the pitch of the rafters, taking into account the slope and length of the slopes, the roofing material used, and also draw up a drawing according to which the assembly will be carried out.

Types of rafter systems

Rafter systems differ in many factors; their composition depends on the layout of the wooden or brick house, the total weight of the roofing pie, the material from which the frame is made, as well as the type of roofing covering.

An important design characteristic is their load bearing capacity, which determines how much weight they can support without deformation. By characteristic features differentiate the following types rafter systems:

Layered

A layered rafter frame is a frame whose rafters have 2 support points. The upper end of the leg rests on a ridge girder mounted on vertical posts fixed to the inner wall. And with the lower end it is installed on the Mauerlat.

Assembly of a layered rafter system on a gable roof is possible only if there is at least 1 load-bearing partition or main column located inside the house. This design is often called non-thrust, because the second support point of the rafters compensates for the thrusting load on the walls of the house, which is assumed by the hanging installation of the frame.

Rafter legs of the layered type experience load only in bending, which can be eliminated by various struts. The layered rafter system allows you to cover houses up to 14 meters wide.

Hanging

The hanging rafter system is distinguished by the fact that its rafters rest only with their lower end on a mauerlat beam installed on the external load-bearing walls. The upper end of the rafter legs of this design does not rest on anything, but seems to hang in the air, which is why 2 types of load arise: bending and expansion.

The thrust load of such a layout of elements on the external walls is so great that it has to be compensated with the help of numerous crossbars and ties, due to which the rafter pairs are tied together.

The structure of a gable roof with hanging rafters consists of triangular trusses, the rigid shape of which is not subject to loads. The complexity of the dangling circuit is believed to be much higher.

The rafter system of a gable roof can be easily installed with your own hands if you correctly calculate the pitch of the rafters, that is, the distance between the rafters and the size of their cross-section.

Combined

Combining the best of both systems, it is recognized as the most reliable. It is used in cases where columns, rather than walls, are used indoors as support inside the house. Then hanging and layered rafters can be alternated to strengthen the structure due to additional elements without increasing the consumption of building materials.

Important! sliding rafter roof- another type of frame, which differs in that the rafter legs are installed on the Mauerlat not using a rigid fastening, but using a movable support. The sliding fastening allows the roof to change dimensions within the range of movement during the shrinkage of the wooden house.

Design

Construction of a rafter system for a gable roof of any of listed types is a set of auxiliary and supporting elements. They distribute the weight of the roofing pie evenly, and also compensate for the bursting and bending loads that arise between them.

The cross-section, length and pitch of the rafters are determined using an engineering calculation that takes into account the weight of the roofing pie, climatic conditions in the construction region, as well as the slope of the structure. Part rafter frame gable roof usually includes the following elements:

  1. Mauerlat. Install the Mauerlat beam on the outer walls of the house, on which the roof slopes rest. It serves to soften the pressure on the supports and evenly distribute the load from the weight of the roofing pie. It is made of durable timber with a cross-section of 150x150 mm or 200x200 mm and is attached to the upper chord of the walls using anchor bolts or long metal pins.
  2. Sill. This is an analogue of the Mauerlat, only it is installed on internal load-bearing walls, and vertical supports must be placed on it for mounting the ridge girder.
  3. Rafter legs. This term refers to frame elements that are made from boards with a cross-section of 150-40 mm and are installed at an angle to the base of the roof, forming an angle of inclination of the slope. The distance between the rafters, their length and thickness are determined using calculations that take into account the total loads to which they are subjected during operation.
  4. Puff. A tie is called a beam that is placed horizontally and connects the legs of one pair of rafters to reduce the bursting load on the outer walls of the structure. The crossbar is a tie installed under the very ridge of the structure.
  5. Racks. A stand is a vertical beam placed flat to support the ridge girder. It is easy to determine what distance should be between the racks, because it follows the pitch of the rafters.
  6. Struts. Diagonally located supports that support the rafter legs in the middle or at the bottom, preventing them from bending, are called struts.

Please note that determining how to correctly position the elements of the rafter system can only be done by calculating the temporary and permanent loads to which they will be subjected during operation. Calculating the total weight of the roofing pie helps determine the correct distance between the rafters, calculate their length and required thickness.

The calculation of the rafter system of a gable roof is based on the fact that in the frontal dimension it has the shape of an equilateral triangle, the sides of which can be easily calculated using simple trigonometric formulas.

These simple calculations help determine the optimal distance between the rafters, their thickness and length. The design calculations are performed in the following sequence:

  • Determine the structure and slope of the roof. There are various ways to select the type and slope of the roofing structure. This parameter depends on climatic conditions and performance characteristics selected roofing material.
  • Determine the total load on the structure. To do this, sum up permanent loads (the weight of the roofing, the weight of the frame, thermal insulation and floors) with temporary loads (snow load, wind load), multiply by a correction factor that takes into account the slope of the slopes, and then add 10-15% to this figure so that the frame had some margin of safety.
  • Calculate the length of the rafter legs. To do this, they use the Pythagorean theorem, because roof truss is an equilateral triangle. It turns out that the square of the length of the rafter leg is equal to the sum of the squares of the height of the blood and half the length of the laying. Knowing how to calculate the length of the rafters, you can calculate the height of the ridge.
  • Determine the cross section of elements. Optimal cross section elements are selected from tables in accordance with the length of the rafter legs and the distance between them. The higher these indicators are, the thicker the rafters should be.

Remember that before you calculate the rafters for the roof, you need to decide on the basic design parameters. In particular, it is necessary to know exactly the height of the ridge and the slope of the roof, as well as the dimensions of the room being covered. The result of the calculation of the roof elements should be a detailed diagram of the rafter system, reflecting their sizes and angles between them.

Calculating the angle of inclination

The angle of inclination of the slopes is selected not depending on aesthetic preferences, but based on weather conditions, taking into account the roofing material. Steeper slopes of 40-45 degrees are constructed in areas with a lot of snow cover, and flatter slopes of 10-20 degrees in places with strong gusty winds.

Keep in mind that the steeper the slope, the higher the consumption of materials, the higher the final cost of the roof. Be sure to take into account the requirements of the material:

  1. Tiles and slate require a slope of at least 22 degrees, otherwise precipitation will seep through the joints between the elements.
  2. Metal tiles are laid at an angle of at least 14 degrees, since they suffer greatly from gusts of wind, they can become deformed or even fly off.
  3. The soft roof allows an inclination angle of up to 5-10 degrees, making it possible to cover slopes of any geometry.
  4. Ondulin is considered one of the most reliable materials and can be used even for roofs with a slope of less than 6 degrees.
  5. Profiled sheets cannot be laid at an angle of less than 15 degrees, however, slopes even with permissible slope It is advisable to treat it with sealant for better waterproofing.

Assembly technology

Before installing the roof frame, it is necessary to calculate the parameters of its elements, based on calculating the total load on the structure, and also create detailed drawing, reflecting its results.

Having a frame diagram in front of you, it is much easier to carry out high-quality installation of the rafter system of a gable roof. The technology for assembling the structure implies the following sequence:

  1. First, a mauerlat is laid on the upper belt of the external walls, on which the slopes will rest, and a bench is mounted on the internal partitions, if the system is layered. These elements must be firmly fixed using anchor bolts or studs.
  2. Then the rafters are fastened. They are fixed with nails to the Mauerlat, and are also connected to each other using a metal plate. It is worth remembering that the rafters are cut to fit the mauerlat timber, and not vice versa. First, the rafters located on the edge are installed in order to set the level along which the remaining pairs will be aligned.
  3. After installing the rafters, you should install auxiliary supporting elements that will support them - struts, tie rods, tie rods. To fix the crossbar more reliably, its end is made with a protrusion half the thickness of the beam and it is cut to the rafters, fixing it with nails in several places.
  4. A sheathing is nailed over the rafter legs, onto which the roofing material is fixed. The material and pitch of the sheathing are selected in accordance with the characteristics of the roofing material and the slope of the roof.

Remember that a well-designed and high-quality rafter system is the key to the strength, reliability and durability of a gable roof. Therefore, do not neglect the help of professional roofers and designers when creating a roofing design for your home.

Video instruction

Thanks to simple device, ease of maintenance and durability, ensuring long-term operation, a gable roof is the most common solution when arranging houses.

Types and features of a gable roof

The shape of the gable roof is determined at the design stage. It largely depends on the further use of the attic space. There are three main types of gable roof:

  • Symmetrical. The most common option provides a reliable device and uniform load distribution. There is virtually no risk of rafters bending down. Significant disadvantage- impossibility of arranging an attic. Sharp corners form areas of the attic that are unusable.
  • Simple asymmetrical. The formation of one angle exceeding 45° ensures an increase in usable area. This allows you to organize additional living rooms. Uneven distribution of load on the foundation and load-bearing walls causes difficulties at the stage of calculations for installing rafters.
  • Broken. The fracture of a gable roof can be internal or external. Thanks to the non-standard design, it becomes possible to use the attic space to create a full second floor. Calculations for installing rafters become much more complicated.

Calculate correct angle slope is a key task preceding the installation of rafters for a gable roof. The climatic features of the region are taken into account. The presence of frequent and heavy rainfall necessitates the need for a steep slope of the gable roof. Installation of flat slopes is preferable in case of significant wind loads. With a possible range from 5 to 90 o, the most common roof option is one with a slope of 35 to 45 o, characterized by savings in material consumption and uniform load distribution.

Rafter system options

The Mauerlat and rafter system are the load-bearing elements of a gable structure. The rafters themselves consist of several parts:

  • rafter legs and tie rods connecting them and imparting rigidity;
  • vertical racks;
  • crossbars;
  • ridge and side girders;
  • longitudinal struts, in regions with significant snow and wind loads is performed additional installation diagonal struts;
  • spacers;
  • bed and sheathing.

Advice ! The rafter diagram necessarily includes the installation chimney and ventilation shaft.

For the selected gable structure, there are three options for installing rafters. Let's look at the features of each method.

  • If the roof width is less than 6 pm, the option of installing hanging rafters is considered. The process involves fixing the leg between the ridge girder and the supporting wall. This ensures a reduction in the impact of bursting force on the rafter legs. The connection of rafter elements is carried out using tightening made of wood or metal. Their installation at the bottom allows them to perform the function load-bearing beams. An indispensable condition is reliable fixation of the tightening, as it is subject to bursting forces.
  • Layered rafters are not limited to the size of gable structures; they include beams and posts. A significant advantage of this type of rafters is ease of installation. The practicality of the design is overshadowed by the presence of a stand.
  • Complex configurations of gable roofs require the installation of combined rafters.

Having determined suitable look rafter system, proceed to calculating the amount of material. Moreover, each roof element needs separate drawing and recording the obtained calculation results.

Calculation of the rafter system

In fact, the rafter system is triangular elements connected together, characterized by maximum rigidity. If the gable roof has a broken structure, the irregular rectangles need to be divided into separate components, followed by calculation of the loads for each part. On final stage the data is summarized.

Determination of permanent and temporary loads

An integral condition for installing rafters is determining the loads on a gable roof. They are divided into constant, variable and special. Components of the magnitude of permanent loads - the weight of the sheathing, finishing materials attic, insulation and other elements that generally form the weight of the roof. On average, this load on the rafters is 40-45 kg m2.

Advice ! Calculation of the strength of a gable structure provides for a 10% margin.

Based on the indicators in the table indicating the weight of individual roofing materials, you should adhere to a maximum load of 50 kg per 1 m 2 of roof area.

The very name of variable loads indicates their inconsistent action. This includes wind force, snow cover and other types of intense influence of weather conditions. A gable roof is like a sail; an incorrectly calculated angle of inclination can provoke its destruction under the influence of strong winds. To calculate this parameter, we turn to the indicators specified in SNiP “Loads and Impacts”, taking into account related factors (location of the house in open space or among high-rise buildings). Determining the influence of snow cover on a gable roof is the product of the weight of the snow and a correction factor that takes into account aerodynamic effects. According to SNiP, the weight of snow ranges from 80-560 kg/m2. The dependence of the coefficients on the angle of inclination of the roof is presented in the following figure:

If the angle exceeds 60°, this parameter is not taken into account due to the impossibility of retaining snow cover on a gable structure. Special loads are provided in regions with increased seismic activity, with possible storm winds or tornadoes, which is not typical for most territories.

Calculation of technical parameters of rafters

The installation of the rafters is based on the shape of the gable roof; the more complex it is, the more rafter elements the system includes. Using soft roof, the angle of inclination of the roof does not exceed 20 o; steeper designs require the installation of ondulin, metal tiles or standard slate.

The choice of rafter pitch depends on the roofing material used and the weight of the gable structure; it varies between 0.6-1.0 m. The number of legs is determined by dividing the length of the roof by the gap between the rafter pairs and then adding 1. The result shows the number of legs per one side of the roof, to determine the overall indicator, the figure is doubled.

Installation of rafters will not be complete without determining their length, for which the Pythagorean theorem is used (c 2 = a 2 + b 2), where:

  • The roof height (a) is selected based on the possibility of further use of the attic space.
  • Let us denote half the width of the house as b.
  • The hypotenuse (c) represents the desired quantity - the length of the rafters.

Note! The result obtained should be increased by 0.6-0.7 m for cutting and moving the rafter element beyond the wall.

If the maximum beam length of 6 pm is not enough to install the rafter leg, it can be spliced ​​by joining or extending.

When determining the cross-section of the rafters, the following factors are taken into account:

  • constant and variable loads:
  • what roofing material will be installed;
  • type of wood used;
  • the length of the rafter legs and the pitch between them.

The table below will help you determine the parameter you are looking for:

Rafter installation pitch (m)

Rafter leg length, m

Analyzing the data, a pattern emerges: increasing the installation pitch of the rafters proportionally increases the load on each leg, therefore, its cross-section should increase.

Approximate cross-sections of individual elements of the rafter system of a gable roof are given below:

Installation of a gable roof

After carefully checking the calculations, they begin to install the Mauerlat.

Mauerlat

Installation of the Mauerlat includes the following steps:

  • Fixing the beam on the wall intended to support the rafters. If the house is made of logs, the function of the Mauerlat is performed by the upper crown. Buildings made of porous material require the installation of a Mauerlat along the entire length of the load-bearing wall.
  • Overshoot problem standard sizes lumber when installing the mauerlat is solved by splicing them.
  • To connect the Mauerlat of a gable roof, the timber is cut exclusively at a right angle; the function of the connecting link is performed by bolts. The use of wire, nails and wooden dowels is not acceptable.

Installation of the Mauerlat can be done in the center of the supporting wall or offset. When fixing the structure, at least 5 cm must remain to the outer boundary of the wall. The use of waterproofing protection will protect the wooden frame of the gable roof from damage by moisture. Secure fastening- an essential condition for installing rafters and mauerlat on a gable roof. There are several ways to fulfill this requirement:

  • Anchor bolts are ideal for a monolithic structure;
  • It is preferable to equip log houses with wooden dowels;
  • porous materials combine well with reinforcement or studs;
  • annealed wire is used as an additional fastening when installing rafters;
  • hinged fastening involves displacement of the rafter legs during the process of shrinkage of the house.

Installation of rafters

Installation of rafter pairs is carried out in two ways: directly on the roof, which is very impractical, or on the ground. With the second method, difficulties may arise when moving the assembled elements onto the roof. The installation of assembled pairs on the mauerlat is preceded by the preparation of cuts; they are made exclusively on the rafter leg, so as not to weaken the base wooden structure. Mounting options are shown below:

To install paired rafters, temporary spacers and struts are used. The ridge unit is formed by connecting at the top of the rafter legs. The process involves several options for completing the task:

  • the small design of the gable roof allows for the absence of a support beam;
  • large dimensions require the use of rafter beams, which subsequently serve as support for the rack.
  • cutting method.

Arrangement options are shown in the photo:

Installing the sheathing makes it easier to attach the roofing material; its pitch directly depends on the coating used:

  • a maximum pitch of 44 cm is possible when arranging the roof with slate or corrugated sheeting;
  • a distance of 350 mm will be sufficient when covering with metal tiles;
  • soft roofing requires continuous sheathing.

Installing rafters contains a lot of nuances that are difficult to foresee in advance. Templates made from thin boards can make it easier to prepare cuts and cuts. The video will also answer some of your questions.

A roof with two slopes is the most common option for completing the box of a private house. When making it, it is important to choose the sections correctly load-bearing elements, securely fasten the nodes and choose the right type of structure. The rafter system of a gable roof is not very complicated and can easily be made with your own hands.

Classification of rafter systems according to the method of support

The design can be classified according to two criteria. The first of them is the method of supporting load-bearing elements. The gable roof truss system of the house in this case includes the following types:

  • with layered rafters;
  • with hanging rafters.

The construction of a roof using layered rafters involves supporting them at two points. The design in this case avoids the occurrence of serious expansion. To do the installation yourself, you will need the following basic elements:

  • rafter legs;
  • Mauerlat;
  • crossbar;
  • intermediate posts and struts for large spans of load-bearing beams;
  • sheathing and counter-lattice;
  • lining thrust bars.

At the top point, installation involves resting on the crossbar. The installation also provides support at the lowest point - the Mauerlat. You can assemble such a structure for your home with your own hands only in two cases:


  1. A layered system is possible if the distance between the gables is not large. That is, like this installation will do for a small house with your own hands. The greatest length of the structure, which allows the installation of a wooden crossbar without additional reinforcements, is 6 m. For large spans, it will be necessary to install metal beams as a crossbar. Using wooden beam It will be necessary to provide intermediate racks, which are located on average every 2 meters. This can only be avoided by using laminated veneer lumber as a crossbar. large section. In this case, a free layout of the space becomes impossible - the racks in the middle of the room cannot be removed.
  2. The second option, when installation of a layered system is possible gable roof with your own hands is the presence of a wall in the middle of the house. The device in this case provides that the beam on which the rafters will rest at the top point will transfer the load to interior wall. In this case Basic structure should not be confused with the septum. The partition rests on the floors, and installing the wall of the house with your own hands involves resting it directly on the foundations. This device is suitable for buildings with sufficient width, where it makes sense to install a wall fence in the middle.

The second option is hanging rafters. They are more complex to calculate, but allow installation in the under-roof space of a free-plan house. The design assumes the absence of supporting wooden or metal beam at the top. Installation involves supporting the rafters only at the lowest point. At the top, the supporting beams are securely connected to each other. Installing such a system resembles a farm. The structure works under tension, so it is important to prevent excessive horizontal load on the walls of the house. This can be accomplished by performing the following activities:

  • device monolithic belt along the edges of the walls;
  • it is necessary to securely fasten the gable roof mauerlat to the wall of the house with your own hands;
  • To eliminate the thrust, a contraction is established.

The screed or screed becomes one of the significant elements of the gable roof of a house. It prevents the walls from expanding under the influence of thrust. The following types of fights can be distinguished:

  • located in the attic floor level;
  • located at the attic ceiling level.

It is worth noting that the second option provides less reliability, since the higher the element is mounted, the stronger the impact the rafters have on it. If the contraction turns out to be too long, you need to strengthen it with your own hands. To do this, additional elements of the gable roof of the house are installed - pendants. They connect the ridge to the middle of the puff, which prevents it from sagging.

The rafter system of a gable roof with hanging rafters allows installation with pre-assembly of trusses on the ground, after which they are lifted onto the roof and secured.

Such option will do only if you have lifting equipment, since the finished gable roofs of the house will become too bulky and heavy to lift with your own hands.

Classification by type of stingray

The second division can be made depending on how the ramp line is designed. The views here suggest two options:


  1. With straight slopes. The easiest way to do it. Allows you to get the job done without major difficulties. The disadvantage of this do-it-yourself roofing option is the reduction in attic space.
  2. With broken slopes. These types of roofing are more difficult to implement. It is assumed that there is a line along which the angle of inclination changes. The angle of inclination of the lower part of the slope must be made larger than that of the upper one. This way you can raise the attic ceiling and increase the free space. The roof is installed with the installation of an additional crossbar at the fracture site.

These types require a choice between them depending on the wishes of the future owner of the building.

Basic roof elements

The rafter system of the gable final part of the building consists of many elements. Installation should begin with a detailed study of each of them and the selection of their sections.

Mauerlat

When installing elements under metal tiles or other coverings, it means using timber with a cross-section of 150x150 or 200x200 mm. It is this size that allows for the most optimal distribution of the load. Next, you will need to choose a fastening method; it depends on the material of the walls. There are several options:


  1. Frame, timber or log walls do not require installation of a Mauerlat. In the case of a frame building, the support for the rafter legs is top harness walls When building fences from timber or logs, the upper crown becomes the Mauerlat. It is important to properly secure these elements in the wall structure.
  2. When using lightweight concrete for construction, additional reinforcement will be required. TO lightweight concrete include materials such as foam concrete, slag concrete, expanded clay concrete. They can collapse if the roof is not placed centrally on them. To distribute the load evenly, a monolithic reinforced concrete belt is poured along the edge of the walls. During work, special wire, pins or bolts are placed in it, onto which the Mauerlat will be attached.
  3. For brick structures, a reinforced concrete belt may not be required.. In this case, to connect to the strapping beam, a wire is inserted into the masonry, which is then wrapped around the mauerlat and twisted. The second option is one row before the walls are cut into masonry with outside wooden blocks impregnated with antiseptic are introduced. Such plugs and Mauerlat are fastened with staples. It is also possible to use studs and bolts, the fastening of which will require pouring a monolithic belt.

An important point is waterproofing.

When installing, it is important to provide roofing felt, linochrome or waterproofing at the junction of concrete or brick with wood. This is required to prevent wood from rotting upon contact with material of a different moisture content.

Rafters

After securing the Mauerlat, the rafter legs are installed. Their cross-section is selected depending on the pitch of the load-bearing beams, their span, snow load and type of coating. When installing a frame under metal tiles at a pitch of 60 cm, it is recommended to follow the following recommendations depending on the span:

  • 3 m – 4x15 cm;
  • 4 m – 5=15 cm;
  • 5 m – 5x17.5 cm;
  • 6 m – 5x20 cm.

Table of average values ​​of rafter legs

These are average values; to perform a more accurate calculation, it is better to contact a specialist or study additional literature.

There are two ways to attach the rafter legs to the mauerlat:

  • with a notch;
  • without her.

Attaching rafter legs to the mauerlat with and without a notch

In the first case, a cut is made on the strapping beam, in the second, a special board is nailed to the rafters, which becomes a thrust block. Further, for both methods, the work is performed in the same way. By using metal corners the inclined beam is fixed so that it does not move relative to the design position along the mauerlat. Additionally, nails are driven in at an angle.


Scheme of fastening rafters using wire and staples

In addition, you will need to fasten the rafter to the wall. This activity is provided for in regulatory documents. You can do this in two ways:

  • on brackets (suitable for wooden buildings);
  • using twisted wire (a more labor-intensive option, but the only one possible for stone houses).

You can perform fastening according to the norms through one leg. This is necessary to more securely attach the roof to the frame of the house.

If the work is done correctly, you won’t have to worry about its condition even in the strongest winds.

Racks, ties, struts

Such elements are most often made from boards. Optimal thickness is in the range of 32-50 mm. The exception is racks. Here you can use boards with a thickness of 50-100mm. Fastening is carried out on studs or using support bars.