How to assemble the roof rafters of a house. Types and diagrams of rafter systems: an overview and recommendations for the installation of a roof rafter system

The construction of a reliable truss system is one of the most difficult tasks in the construction of the roof of a country house, summer cottage or garage. And nevertheless, do not rush to give up - today we will refute the conventional wisdom that such work is beyond the power of a beginner. Knowing the rules for calculating, sawing and installing a roof frame, you can build a roof just as well as specialists. In turn, we will try not only to talk about the device, design and construction features of rafter systems of various types, but also share the secrets of experienced craftsmen.

What is called a rafter system and how it works

Any, even the most seedy roof is based on a strong power frame, called a rafter system. The rigidity of the roof depends on how correctly this structure is installed, and therefore the ability to withstand even the strongest wind and snow load.

The rafter system is a power frame of the roof, which takes all the wind and snow load

The best material for the manufacture of rafters (trusses) is considered to be a bar or thick board made of coniferous wood. And there is an explanation for this - pine or spruce lumber has a relatively low weight, and the presence of natural resins makes it quite durable. Even if the timber has a slight residual moisture, it will not dry out, which is no less important factor than ease of use and long service life.

Depending on the size of the roof, the supporting elements of the structure can have a cross-section from 50x100 mm to 200x200 mm or more. In addition, the length of the roof directly affects the number of rafters, because they are installed in small steps - from 60 cm to 1.2 m.

Structural elements of the rafter system

The main requirement for a wooden frame is the ability to resist bending and twisting. For this reason, a triangle shape is best for timber frame trusses. Moreover, they can consist of several parts:

rafter legs - the base of the roof frame, which has the greatest impact on the size and geometry of the slopes;
crossbars (tightening) - boards with which a pair of rafter legs are pulled together;
girders - transversely installed beams, due to which the rafters are connected into a single structure;
racks - vertical supports that serve to support the rafter legs or prevent the bending of the girders;
struts - the same racks, only set at an angle to the vertical;
beds - boards attached to the floor of the attic, on which supports are installed;
Mauerlat - a support bar installed on the bearing walls, to which the lower parts of the rafter legs are attached;
filly - pieces of timber or boards that are nailed to the lower ends of the trusses and are used to equip the overhangs of the roof.

Additional elements of the rafter system make the roof frame stronger, more rigid and stable

When choosing a roof frame design, it is important to find the very middle ground that will allow you to get a strong and reliable structure at minimal cost. For this reason, you can deviate a little from the established canons, if it does not concern the rigidity of the entire structure. For example, it is quite possible to do without fillies, and to form the eaves overhang due to the longer rafter legs. Or use not a solid Mauerlat, but pieces of timber laid only at the points of attachment of the rafter legs - it all depends on the engineering ingenuity and experience of the roofer.

Rafter classification

Depending on the design of the roof and the purpose of the attic, the wooden frame can consist of several types of rafters:

Features and varieties of rafter systems

To make a balanced choice, you need to understand the features of the rafter systems of various types and know the strengths and weaknesses of each structure.

Roof frame with hanging rafters

Since the principle of attaching hanging rafters does not imply additional support points, this design is used for buildings no more than 6 m wide.

The roof frame with hanging rafters transfers only vertical forces to the walls, therefore it has simpler attachment points to the load-bearing walls

During operation, a force acts on the hanging rafters, striving to push the structure apart. To compensate for the bursting force, a crossbar from a wooden bar or a metal profile pipe is installed between the rafter legs. If the attic space will be used for household purposes, then the upper lintel is attached as close to the ridge as possible, and the lower edges of the pairs of rafter legs are connected with puffs. Such a scheme allows you to increase the useful height of the attic without at all reducing the strength of the frame. By the way, if the lower lintels are made of a bar with a cross section of more than 100x100 mm, then they can also be used as load-bearing beams. It is necessary to ensure a reliable connection of the puffs and rafter legs, since significant stretching forces also act on the place of their attachment.

Roof with layered rafters

Reinforced rafters require the installation of at least one support, therefore they are used for buildings with internal load-bearing walls. The maximum length of a single span should not exceed 6.5 m, otherwise the strength and rigidity of the roof frame will suffer. To increase the width of the roof, the rafter system is reinforced with intermediate supports. Even one additional pillar allows you to increase the roof width up to 12 m, and two - more than 15 m.

The layered rafter system is ideal when wide roof widths are required

The stability of the layered trusses can be increased by means of a rafter frame with purlins, struts and struts. In addition, this rafter system requires much lower lumber costs. Versatility, strength and cost-effectiveness have long been appreciated by both construction companies and individual developers, most often using roof structures with layered beams in their projects.

Combined options

Today, the roofs of country houses surprise with the elegance of design, whimsical forms and a variety of configurations. There is only one way to build such complex structures - by combining rafter systems of both types in one frame.

The combination of layered and hanging trusses allows you to get a rafter system of any configuration

Even for the construction of not the most complex broken roof, both rafter systems are used at once. Right-angled triangles located on the sides are layered rafter structures. And they are connected due to the upper tie, which simultaneously plays the role of tightening for the upper hanging rafters.

The procedure and rules for the installation of roof frames

Since two types of roof frames are used in the construction of roofs, we will consider the installation technology for each structure separately. However, before starting construction work, it is necessary to study the methods of fastening the structural elements to each other.

Roof structure with hanging rafters

It was already mentioned above that hanging rafters are most often used in the construction of small or undemanding buildings. In this case, a log house is almost an ideal option, since you can do without a Mauerlat. The lower part of the rafter legs is attached to the upper rim or the edges of the ceiling beams (mat) protruding beyond the perimeter of the walls. In the latter case, the tightening must be moved upwards - this will allow the timber to be let over the finishing log and make the attic more convenient.

To increase the height of the attic space, the puff should be installed as close to the top of the roof as possible.

Preparatory work

The geometry of the slopes depends on how well the beams are prepared for the rafter legs. A cord stretched between nails driven into the extreme beams will help to level the supporting surfaces..

It is necessary to cut the slab, having received flat platforms for installing trusses. After that, you should definitely check how accurately they lie in the same plane. This can be done using a long, even rail and a level.
Before installing the trusses, the supporting surfaces are aligned with the cord.
After removing the excess wood, in each beam you need to make a recess under the rafter spike. You can outline the locations of future nests using the same nails and cord as in the previous case. Although the recesses for the rafters can be made both before and after the manufacture of trusses, experts advise to perform them first - this will allow fitting with higher accuracy and convenience.
The method of fastening the rafters depends on many factors - the type of support beams, their cross-section, the characteristics of the roof overhang, etc.
Professional roofers recommend installing an additional landmark in the center of the span of each gable - a vertical batten. One of its lateral sides is used as an axis of symmetry, which will make it possible to monitor strict observance of the geometry of the structure.
In order to simplify the process of marking and installation of the roof frame, vertical slats are used, installed along the centerline of the roof.

Making rafters

In order for the rafters to have the same dimensions and configuration, they are made according to a pre-made template. For its manufacture, we suggest using the following instructions:

Take two hawk planks and bolt them together to create a compass-like structure. Do not overtighten the threaded connection - the structure must rotate around the top. Be sure to check that the slats are 10-15 cm longer than the rafters - this will be needed to take into account the height of the stubborn tooth.
The simplest template allows you to get roof trusses of the same size and configuration
Place two marks on the rail set as a guide. The lower one should correspond to the height of the rafter system, and the upper one should be spaced from it by the height of the mounting protrusion.
Place the template on the mat so that the corners of the boards rest against the rafter teeth grooves.
In order for the structure to successfully cope with the bursting loads, the persistent tooth at the end of the rafter leg is inserted into a recess on the floor beam
Align the axis of rotation of the "compass" with the upper mark on the staff and set aside the height of the tenon from the lower corners of the conductor.
Pull the template down and cut the teeth along the line you marked. After that, lift the device to the roof and insert the spikes into the slots on the mat. Check the alignment of the sample axis with the bottom mark on the vertical staff. If necessary, move the bolt in the desired direction and fix the angle between the boards with a cross member.
Several methods are used to fasten the trusses - it all depends on the type of support beams, the design of the roof frame and the section of its elements
After adjusting the template in height, draw vertical abutment lines on each board. Finally, measure the length of the ledger and construct a template from the board scraps for making truss tops.
To attach the crossbar to the rafters, overlays made of inch board segments are used

After the template is lowered to the ground, it is disassembled and cuts are made according to the applied markings. In addition, a separate template is being constructed, along which the ends of the rafter legs will be cut. The manufacture and assembly of hanging rafters is most often done below, lifting ready-made structures to the roof. If the weight and dimensions of the assembled trusses do not allow to drag them up manually, then the assembly is carried out on the spot. In this case, the components of the rafter system are fixed with nails ranging in size from 100 to 200 mm.

How to install roof rafters

In order to raise and install the trusses, you will need the help of at least one person. Fitting and plumbing the rafters alone is an extremely difficult task - you have to fasten them to the struts more than once and descend from the roof many times to check the deviation from the vertical plane.

With the rafter tooth, it is possible to obtain such a reliable connection that only one nail can be used for final fixation.

Lifting the assembled rafters up, first mount the extreme structural elements, and then the central and intermediate ones. To strengthen the structure, a support is installed under each leg:

Having set the hanging rafters in level, they are fixed with temporary struts. After that, the lower ends of the beams are nailed to the mat or floor beams.

Various temporary structures greatly simplify the process of leveling rafters

It is not worth resorting to newfangled fixing methods using a variety of corners and perforated plates. A reliable "old-fashioned" method of fastening with 200 mm nails or construction staples will be much better both in terms of strength and reliability, and in terms of cost. At this stage, don't worry about the design looking flimsy.... After the remaining elements of the rafter system are installed and the crate is made, the structure will acquire the necessary rigidity and stability.

Video: making and installing hanging rafters with your own hands

Features of the installation of layered rafters

The process of making and installing layered rafters is generally very similar to the construction of a suspended roof frame. The main difference is at the top point and it is connected with the fact that the tops of the layered beams rest on the ridge girder. In this case, the connection with the latter is performed in several ways:

simple joining apart (in parallel to each other);
with the execution of a vertical joint (the same as when connecting the paired legs of a hanging truss);
by the method of tight fitting of the beams to the upper beam (using a vertical saw or a cut).

If the structure of the wooden frame provides for the support of the trusses on the side girder, then the rafters are joined end-to-end, and grooves are made in the places of abutment to the girder.

For fastening the layered rafters, nails, construction brackets or lining made of wood and metal are used

To ensure structural strength, the notches should not be too deep.... Experts recommend making indentations no more than a quarter of the thickness of the timber or a third of the width of the board.

Individual developers most often resort to installing rafters in the following way:

the upper part rests on the ridge beam by means of a vertical cut;
from below, the rafter legs are held by the corner cut.

It is convenient to use a construction square for marking. After the scale is selected, the values of the rise of the slope and half of the span are plotted on the sides of the right-angled triangle. Thanks to this, it will be possible to obtain the slope angle of the slope without resorting to mathematical calculations.

For the manufacture of rafters, we suggest using the most convenient method:

At first glance, this method is very tricky. However, even a cursory acquaintance with the instructions given is enough to master it perfectly. Of course, you can postpone the necessary distances and make the markup in a calculated way, however, when calculating angles and distances, it will be much easier to get confused.

It should be remembered that the saws made in the rafter legs must be exactly the same, otherwise the slope of the roof will be uneven. To do this, you can use a block of wood as a template. It is only important that its thickness does not exceed 1/3 of the thickness of the workpiece.

For the most common slope angles, there are templates, the configuration of which has already been calculated by professionals. Using one of these patterns, you can significantly simplify the task of marking the corners of the cuts.

Patterns with pre-cut corners simplify the rafter manufacturing process

Assembly and installation of the layered structure

Video: installation of rafter legs of a layered roofing system

Methods for joining rafter lags

When choosing a beam for oversized roof trusses, you have to find a reasonable compromise between the length and thickness of the rafters. This is due to the characteristics of the standard range of lumber, in which the longer beams have a larger cross-section. On the other hand, their use is not always justified both technologically and in view of the increased cost of the structure. The way out of this situation is to lengthen the rafter legs using the splice method. The rigidity and mechanical strength of the timber depends on how correctly the joint will be made, therefore the connection is performed strictly according to a specific method.

Oblique cut method

The method of splicing with an oblique cut consists in the fact that inclined cuts (cuts) are formed on the mating parts of the beams. They should be performed very carefully - after combining both parts of the timber, there should be no gaps, otherwise deformation will appear at the junction.

When splicing with an oblique cut, there should be no gaps and gaps between the mating surfaces that can weaken the rafter and cause its deformation

When making cuts, a small transverse section with a height of at least 15% of the rafter thickness is left - the presence of the end part will make the connection more durable. To calculate the optimal length of the bevel cut, you need to multiply the height of the bar in the place of the cut by two. The cut is fastened with nails, clamps or bolted connections.

Rallying connection

To lengthen the rafter by the method of rallying (stitching), the edges of the boards are overlapped and a rack is installed in the center of the junction zone. The elements are fastened with nails, which are hammered in according to a certain pattern:

along the edges of the ends - every 45–90 mm;
along the edges of the stitched boards - in a zigzag manner, with a step of 50 cm.

Joining the boards by rallying allows you to do without additional overlays, but requires the installation of an additional support in the center of the junction area

In order for the timber to successfully cope with the operational loads after joining, the length of the rallying section (T) is calculated using the formula T = 0.42 × L, where L is the length of the span to be covered.

Frontal support

The connection by frontal build-up consists in the fact that the edges of the individual parts of the rafters are carefully butt-trimmed and aligned end-to-end. For fastening, lining of lumber with a thickness of at least 1/3 of the section of the main beam is used. The length of the overlays is determined by the formula L = 3 × h, where h is the width of the board.

When splicing with a frontal stop, a monolithic structure will turn out only with the correct placement of fasteners

Fixation of all parts is carried out using a nail fight or bolted connections. In the first case, nails are driven in in two parallel rows, trying to place the fasteners in a zigzag. The threaded connection is performed in a staggered manner, determining the number of bolts depending on the length of the lining.

Composite length extension

To build up a rafter leg, it is not at all necessary to use both parts of the same section. In case of compound build-up, a single element can be lengthened by means of two boards, which are sewn onto its lateral planes. The resulting gap is filled with sawn timber scraps of length l = 2 × h with a step L = 7 × h, where h, as before, is the thickness of the lengthened element.

Composite rafter extension allows you to attach crossbars, supports and other structural elements in the most convenient way

Expert advice on the manufacture of rafters and the assembly of the roof frame

When starting to design and install a rafter system on your own, be sure to consult with experienced roofers regarding the peculiarities of roofing in your area. Perhaps their advice will keep you out of trouble and help you save time and money. In turn, we offer several recommendations that will help make the structure more reliable and durable:

If a minimum cross-section beam is used for the manufacture of a Mauerlat or upper strapping, then the cuts can weaken it. For this reason, cutouts should only be made at the lower ends of the rafter legs.
In order for precipitation not to fall on the wooden frame and walls of the house, the roof must have an overhang. For its arrangement, pieces of timber (filly) are used, with which the length of the rafter legs is increased, or larger farms are made.
The connection with saws at an angle of 90 o must not be used- in this case, the resistance of the element to load forces is significantly reduced.
If the elements of the rafter system are connected with threaded fasteners, then wide washers or metal plates are installed under the heads of the bolts and nuts. Thanks to the increased area, the fasteners will not be pressed into the wood.
All wooden parts of the structure must be thoroughly impregnated with an antiseptic and fire retardant.
When determining the cross-section of the puffs, they are guided by how close they will be to the ridge. The shorter the connecting bar, the greater the load it carries and the more heavy-duty lumber and bolted fasteners are used.
When determining the cross-section of the timber for the manufacture of rafters, do not forget to take into account the thickness of the heat-insulating layer.

Video: expert recommendations on the correct connection of the elements of the roof frame

https://youtube.com/watch?v=GbTAu5-flfs

Modern materials and technologies make it possible to build a roof of any configuration and purpose. Given this variety, it is simply impossible to consider in detail all the options within the framework of one article. However, based on the basic building principles discussed here, you can easily tackle even the most complex structures. The main thing is to pay attention to the little things, to be attentive and accurate in your work. And then the roof will not only be a reliable functional superstructure, but also a true decoration of your home.

Thanks to my versatile hobbies, I write on various topics, but my favorites are engineering, technology and construction. Perhaps because I know a lot of nuances in these areas, not only theoretically, as a result of studying at a technical university and graduate school, but also from the practical side, since I try to do everything with my own hands.

A roof with two slopes is the most common option for completing the box of a private house. When manufacturing it, it is important to correctly select the cross-sections of the bearing elements, to securely fasten the nodes and to choose the right type of structure. The rafter system of a gable roof does not have great difficulties and can well be made by hand.

Classification of rafter systems by the method of support

The design can be classified in two ways. The first of them is the way of supporting the 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 roofing device using layered rafters involves their support at two points. The design in this case avoids the occurrence of serious pressure. To do the installation yourself, you will need the following basic elements:

rafter legs;
mauerlat;
crossbar;
intermediate struts and struts with a large span of load-bearing beams;
lathing and counter-lathing;
lining persistent bars.

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

The elevated system is possible if the distance between the gables is not large. That is, such an installation is suitable for a small house with your own hands. The greatest length of the structure, which allows the construction of a wooden girder without additional reinforcement, is 6 m. For large spans, it will be necessary to install metal beams as a girder. When using a wooden beam, it will be necessary to provide for intermediate racks, which are located on average every 2 meters. This can be avoided only when used as a crossbar of glued laminated timber of a sufficiently large cross-section. In this case, free space planning becomes impossible - the racks in the middle of the room cannot be removed.
The second option, when it is possible to install a layered gable roof system 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 the inner wall. In this case, the supporting structure should not be confused with the partition. The partition rests on the floors, and installing the wall of the house with your own hands involves resting it directly on the foundations. Such a 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 in calculation, but they allow the device in the under-roof space of an open-plan house. The design assumes the absence of a supporting wooden or metal bar in the upper part. Installation involves the support of the rafters only at the lowest point. In the upper part, the supporting beams are securely connected to each other. Installing such a system is like a farm. The structure works on a spacer, so it is important to prevent excessive horizontal stress on the walls of the house. this can be done with the following activities:

the device of a monolithic belt along the edge of the walls;
it is necessary to securely fasten the Mauerlat of the gable roof to the wall of the house with your own hands;
to eliminate the tension, a fight is established.

The scaffold or screed becomes one of the significant elements of the gable roof of the house. It prevents the walls from expanding under the action of the expansion. The following types of contractions can be distinguished:

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

It is worth noting that the second option provides less reliability, since the higher the installation of the element is, the stronger the rafters have an effect on it. If the fight turns out to be too long, you need to make it stronger with your own hands. For this, installation of additional elements of the gable roof of the house - suspensions is carried out. They connect the ridge to the middle of the puff, thus preventing it from sagging.

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

This option is only suitable if you have lifting equipment, since the finished gable roof of the house will become too large and heavy to lift with your own hands.

Classification by type of ramp

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

Straight slopes... The easiest way to do it. Allows you to get the job done without serious difficulty. The disadvantage of this do-it-yourself roof option is a decrease in the space of the attic.
With broken slopes. These types of roofs are more difficult to perform. 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. Thus, it turns out to raise the attic ceiling and increase the free space. Installation of the roof is carried out with the installation of an additional crossbar at the fracture site.

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

The main elements of the roof

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

Mauerlat

When installing elements for metal tiles or other coating, it is assumed that a bar with a section of 150x150 or 200x200 mm is used. It is this size that allows the most optimal distribution of the load. then you will need to choose a method of fixing it depends on the material of the walls. There are several options:

Frame, timber or log walls do not require the installation of a Mauerlat. In the case of a frame building, the upper wall rail serves as a support for the rafter legs. when building fences from a bar or log, the upper crown becomes the Mauerlat. It is important to correctly fix these elements in the wall structure.
When used for construction of lightweight concrete, additional reinforcement will be required. Lightweight concrete includes materials such as foam concrete, slag concrete, expanded clay concrete. They can collapse if the roof is not supported centrally on them. For even distribution of the load, a monolithic reinforced concrete belt is poured along the edge of the walls. During work, a special wire, pins or bolts are laid in it, on which the Mauerlat will be fastened.
For brick funds, you do not need to provide a reinforced concrete belt... In this case, to connect to the strapping bar, a wire is introduced into the masonry, which is then wrapped around the Mauerlat and twisted. The second option - one row before the walls are cut, wooden blocks impregnated with an antiseptic are brought into the masonry from the outside. Such plugs and Mauerlat are fastened with staples. It is also possible to use studs and bolts, which will require pouring a monolithic belt.

An important point is waterproofing.

When installing, it is important to provide roofing material, linokrom or waterproofing at the junctions of concrete or brick with wood. This is required to prevent wood from rotting when it comes into contact with material with a different moisture content.

Rafters

After fixing the Mauerlat, the rafter legs are installed. Their cross-section is selected depending on the pitch of the supporting beams, their span, snow load and the type of coverage. When installing a frame under a metal tile at a step of 60 cm, it is recommended to observe 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, in order to perform a more accurate calculation, it is better to consult a specialist or study additional literature.

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

with a notch;
without her.

Fastening the rafter legs to the Mauerlat with and without a notch

In the first case, a gash is performed on a strapping bar, in the second, a special plank is nailed to the rafter, which becomes a stubborn bar. Further, for both methods, the work is done in the same way. With the help of 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.

The scheme of fastening the rafters with wire and on staples

In addition, you will need to fasten the rafter to the wall. The implementation of this measure is provided for in the regulatory documents. There are two ways to do this:

on staples (suitable for wooden buildings);
using a wire twist (a more laborious option, but the only one possible for stone houses).

It is possible to carry out fastening according to the norms through one leg. This is necessary for a more secure attachment of the roof to the box of the house.

If you carry out the work correctly, you can not worry about its condition even in the strongest winds.

Racks, ties, struts

Such elements are most often made from planks. The optimum thickness is between 32-50 mm. Racks are an exception. Here you can use boards with a thickness of 50-100mm. Fastening is carried out on pins or using support bars.

The simplest gable roof is at the same time the most reliable. The availability of do-it-yourself execution does not give rise to self-confidence - before starting work, you need to thoroughly familiarize yourself with the design features in order to make decisions and execute them in a qualified manner.

Diagram and features of the gable roof device

A gable roof is called a roof formed by the intersection of two rectangular slopes at a certain angle. Such a device is the most reliable and simplest, therefore, even a person with average carpentry skills can independently mount a gable roof.

The base of the roof is a rafter system that acts as a support for the roofing cake and topcoat. The service life of the roof and the comfort of living in the house depend on its strength and reliability. The rafter system, subject to regular wind and snow loads, must be securely attached to the building body. This task is solved with the help of a Mauerlat, which is firmly fixed to the upper plane of the walls of the house. Thus, an almost monolithic system is created that reliably protects the internal space of the house from any manifestations of the external environment.

Photo gallery: how you can use the space under a gable roof

A residential attic can be arranged under a gable roof A gable roof with a Danish half-hip improves the exterior of the building and allows you to increase the size of the attic The attic above the garage can be used to store spare parts, set up a break room or equip a warehouse for household equipment The area of the attic under a gable roof depends on the height of the ridge and the angle of inclination of the slopes

The structure of the gable roof truss system

A roof with two opposite slopes is the most common construction used in individual housing construction. The intersection line forms a ridge, and the side openings of the extreme rafter legs serve for the device of gables - vertically located walls that create a closed under-roof space. To obtain a strong and durable structure, many retaining and reinforcing elements are used, giving additional rigidity to the entire structure. The gable structure is based on a triangle - the most rigid geometric figure. The rafter system consists of the following main elements:

Mauerlat is a wooden beam that acts as a connecting element between the frame of the house and its rafter system. It is attached to the walls with threaded rods, anchor screws or wire harnesses. The size of the cross-section of the timber is from 100x100 to 150x150 mm and depends on the size of the building, its number of storeys and the shape of the roof.
Rafter leg - a wooden beam measuring 50x150 or 100x150 mm, connected at the top of the roof with the ridge and resting on the opposite end on the Mauerlat. Rafters are the main bearing element of the roofing system, which perceives all types of external loads: wind, snow, rain and the dead weight of the structure.
Roof trusses form the load-bearing frame of the roof and determine its geometric shape
Lezhen - timber made of wood, laid horizontally with support on the internal load-bearing wall. The size of the bed, as a rule, is equal to the size of the Mauerlat. Supports roof racks.
Tightening is an element used in hanging rafter systems. Its purpose is to compensate for the tensile forces that occur at the lower ends of the rafter legs.
Racks - square beams that transfer part of the load from the rafters to the beds.
Struts are structural elements that transfer part of the load from the rafter legs to the tightening. Thus, a farm with increased strength characteristics is formed.
Counter lattice - wooden bars ranging in size from 25x50 to 50x50 mm, stuffed onto the upper edge of the rafters. The purpose of the counter-lattice is to form a ventilation gap between the lathing and the waterproofing film. This element is required when constructing a roofing pie in the attic.
Sheathing is a support base for installing a finishing roof covering. The sheathing can be solid or sparse and can be made of 25 mm thick boards, waterproof plywood, OSB sheets and other similar materials. The choice of lathing design depends on the characteristics of the topcoat.
A ridge is a horizontally located beam along which opposite slopes intersect.
Roof overhang - is a continuation of the rafters at a distance of up to 40 cm from the walls of the building. Protects walls from getting wet, and also serves to place spotlights, which are an integral part of the ventilation system of the under-roof space. With insufficient rafter length, the overhang is formed by additional parts for their lengthening - filly.
The rafter system of a gable roof consists of triangular trusses, supported by a Mauerlat and a ridge, lathing and several auxiliary elements that reinforce the structure

Calculation of the load on the rafter system of a gable roof

The rafter system experiences certain loads, which can be divided into two types.

Constant loads acting independently of any other factors. Their size is determined by the design of the roofing pie and consists of the weight of waterproofing and vapor barrier films, insulation, additional elements, fasteners and any other elements of the roofing covering, including the finishing one. In practice, the average weight of all components of the roof of a house is about 40–45 kg / m 2. More precisely, this value can be calculated by summing the specific load values of each material used, which can be taken from the look-up tables. When calculating the weight of the roof, it is recommended to lay a safety margin of 10%.
When calculating the load, the weight of each element of the roofing cake is taken into account
Variable loads. These include the effects of wind and snow, depending on their intensity. In fact, the roof of the house is a sail that takes up the load from the wind. The force of direct impact on the roof along the normal depends on the angle of inclination of the slope - the smaller it is, the lower the load. At the same time, eddies arise on the leeward slope, and a load on the roof appears with an inverse impact vector. With hurricane winds, the separation force can reach 630 kg / m 2. Snow influences also belong to variable loads. It should be noted that they also have clearly defined regional indicators.
Wind loads are a risk factor for roofs as they create large tearing and overturning forces.

Obviously, careful calculation of snow and wind loads, taking into account local climatic conditions, is vital when choosing a roof structure and materials. These loads can be determined from the map drawn up on the basis of SNiP 2.01.07–85.

The map can be used to determine the value of wind and snow load in the construction region.

The values of snow and wind loads marked on the maps for each region are called normative. In order to obtain the calculated snow load, the standard value must be multiplied by a special coefficient that takes into account the angle of inclination of the roof. This coefficient is equal to:

1 with a slope of less than 25 o;
0.7 at an angle of inclination from 25 to 60 o;
0 for steeper slopes.

The calculated wind load is determined by multiplying the standard value by a factor that takes into account the height of the building and the type of terrain in which the construction is being carried out.

Table: Correction factor for calculating wind load (taking into account building height and type of terrain)

The specific load of the most popular roofing materials can be taken from the following table.

Table: Weights of some roof materials

It is possible to take into account the features of the impact of different types of loads only in aggregate, therefore, calculations of this nature should be entrusted to an experienced specialist.

Video: calculation of the rafter system

Types of gable roof truss systems

According to the principle of the device, rafter systems are of two types:

Hanging.
Forced.

Hanging rafters are used for buildings in which the bearing supports are located at a distance of up to 10 meters in the absence of an intermediate wall inside the building box. For other cases, it is necessary to use a layered rafter system.

Features of the device of the hanging rafter system

The hanging rafters are supported by the outer walls. Since the arch has a joint at the upper point, when vertical loads are applied to it, expanding loads are created on the lower supports. To compensate for them, puffs are used - horizontal ligaments between the lower ends of the rafter leg. The result is a rigid force triangle. When arranging an attic room, floor beams are used as a tightening. Various constructive solutions for the hanging rafter system are possible:

Simple three-articulated arch. It is a triangle-shaped structure. In this case, the tightening works only in tension and is not a supporting one. Therefore, it can be replaced with a conventional metal beam. In this case, the connection of the cornice joint is performed with a simple orthogonal cut using wooden plates or metal plates.
The three-pivot arch is the simplest truss structure for a gable roof
Reinforced three-articulated arch. This scheme was used earlier in the construction of industrial buildings, when the span exceeded 6 meters. In this case, the tightening is suspended on a wood headstock. The assemblies are connected using metal parts and equipped with devices for adjusting the tension. The main load in such a system falls on the ridge of the roof. In individual housing construction, such rafter systems are not used.
A three-articulated arch with reinforcement differs from a simple one by the presence of a vertical stiffener (headstock) and the ability to adjust the tension at the joints
Hinged arch with a raised latch. In this version, the rafter leg is partially unloaded through the roof ridge by the suspension to the raised puff. It rises to a height of at least 2.2 m from the attic floor level. Such a system is ideal for the construction of an attic room in the under-roof space. The connection of the tightening with the rafters is made by a tie-in, as a result of which the connection in the unit becomes fixed.
A hinged arch with a raised latch is ideal for installing an attic under-roof space
A three-pivot arch with a deadbolt is used to strengthen the rafter system by creating an additional power triangle. The system is used for significant bursting loads. The connection of the crossbar to the rafter must be fixed, otherwise the entire system will not have the required rigidity.
An additional horizontal element (transom) gives the system greater resistance to bursting loads

The crossbar, in contrast to the lower tightening, operates in compression, not tension.

In addition to those listed, other elements are also used to strengthen the roofing skeleton. Very popular are struts and struts located in the system at the places where the rafters are most loaded.

In the most loaded places, roof trusses can be reinforced with struts and struts

Video: rafter system step by step

Roof systems of the layered type

Reinforced rafters are used for buildings with a width of more than 10 meters. They are characterized by the presence of a load-bearing wall inside the building, which is an additional support for the rafter system. Nesting structures are of several types:

In non-expansion layered systems, the main load from the roof frame is transferred to the Mauerlat

Determination of the pitch of the rafters of a gable roof

The task of ensuring sufficient strength of the rafter system is solved by selecting the material for the manufacture of its elements and calculating the parameters of their installation. The pitch of the rafters is one of these elements and is selected depending on the weight of the roofing cake. The distance between the support beams is usually set in the range of 0.6-1.5 m. The actual pitch between the rafters depends on the geometry of the roof and is calculated as follows:

The number of rafter legs is determined. To do this, you need to use the ratio n = L / d 1 + 1, where n is the number of rafter legs, L is the length of the roof along the ridge, d 1 is the desired distance between the rafters.
The calculated distance between the rafters is calculated, for which the length of the roof along the ridge is divided by the amount obtained in the previous paragraph: d = L / n.

For example, consider an option with a roof length of 13 m with a preferred distance between rafters of 750 mm (option for a roof with ceramic tiles).

The number of rafter legs n = 13000/750 +1 = 18.33. Since the number of rafters must be sold in whole, round this value to 19.
The rafter pitch d = 13000: 19 = 684 (mm).

Thus, on the roof we have chosen, the rafters must be installed with a pitch of 68.4 mm.

It should be remembered that the result obtained is the distance between the axes of the rafters.

Gable roof truss system units

We have already discussed the main types of joints in the nodes of the roof supporting structure above. But it makes sense to dwell in more detail on the auxiliary materials that make the rafter system more reliable and durable.

You can strengthen the fastening of parts when installing the rafter system using metal plates and corners of various shapes

Such products are made of galvanized steel up to 1.5 mm thick. They have various configurations and can be installed on any kind of connection.

Photo gallery: types of connections in the nodes of the rafter system of a gable roof

In the ridge part, the rafter legs are usually connected by flat bolted plates To strengthen the structure of the rafter system, it is necessary to select metal plates that correspond to the configuration of the fastening unit Sliding knot mates relieve the rafter structure Junction points in the rafter system can be additionally reinforced with metal inserts Depending on the type of rafter system used, there are different ways of attaching the ridge knot On flat joints operating under heavy loads, it is convenient to use nail plates

All docking nodes of the rafter system have the function of strengthening the rafters by redistributing the loads and strengthening the bearing elements. So, in the lower part, the rafter is supported on the Mauerlat at a right angle, for which the corresponding inserts are made.

To strengthen the rafter system, they try to use connections with the maximum bearing capacity, for example, cutting the rafters into the Mauerlat at a right angle

In addition, metal mounting plates are used for additional reinforcement in the docking points. The same principle is used when installing struts to the rafters. In any case, the mating parts must work "on the stop" and not move during operation.

Any parts must be loaded along their axis

There are three main types of nodes in the rafter system:

Ridge connections. This is the joining of two rafter legs at a given angle along the line of intersection of the slopes. They can be hinged or blind. The first ones are used when installing a rafter system on log or log houses, which tend to sag and rise, depending on the season, during almost the entire service life. Blind joints are used in the truss systems of houses made of building stone. In such structures, a reinforced belt is installed on top of the wall, which takes on the lateral loads.
Fastening the lower ends of the rafter legs to the Mauerlat. Since they are at an angle to the support bar, a sliding vector is created that is directed outward from the structure. To compensate for it, a tie-in is made in the Mauerlat, and a heel is made on the rafter. The rafter is inserted into the groove with an emphasis on it and is fastened with a nail through the edge of the beam into the Mauerlat. Additional support parts made of bars are also used. In cases where the rafter has to move (on wooden log cabins), sliding fasteners are used. They make it possible to compensate for seasonal changes in the height of the walls.
Other nodes. All other parts of the rafter systems are essentially stubborn elements working in compression, rarely in tension. They are installed by cutting into the mating parts to prevent them from displacement under load. Such details include crossbars, struts, struts, stops and other similar parts.

For a stronger connection, the additional elements mentioned above are used.

Installation of a gable rafter system

Currently, the construction market offers services for the manufacture of individual roof trusses for specific buildings. It should be noted that this service has a number of advantages:

Guaranteed product quality, ensured by the use of special equipment and assembly technologies.
Fire safety, since all truss parts are flame retardant.
Longer service life, which is achieved by antibacterial treatment of products with special compounds.
Easy to install ready-made trusses.

The only drawback of this method of installing a rafter system is the relatively high cost of products.

For self-erecting a gable roof, you can use ready-made roof trusses ordered from professional manufacturers

Assembling roof trusses on the ground

The assembly of rafters on the ground is used in cases where there is a flat area of sufficient size right next to the house for the manufacture of trusses. In this case, not complete trusses are mounted, but rigid structures of three or four parts, which can be lifted to the installation site by the efforts of two or three people. Lifting is carried out with the help of ropes along the slopes. The advantage of this assembly method is the possibility of using a single template, which ensures high precision in the manufacture of each structural element. A possible option for partial installation of trusses below is as follows:

Make a slipway for assembling trusses. It consists of three platforms, the distance between which corresponds to the length of the mating parts. They can be assembled from several boards or beams located in one horizontal plane.
For the convenience of assembling the rafter frame on the ground, you need a free area of a certain size and auxiliary elements on which you can place structural details
To assemble the first truss, you need to take two rafter legs and a tightening - lower or upper.
Having laid out the parts on the slipway, place them in accordance with the truss drawing and fasten them with nails. Check the truss blank for compliance with the dimensions specified in the technical documentation. Correct the location of the components if necessary.
Carry out the final fixation of the parts in the truss nodes using additional fixing plates. The nail plates can be installed using a power clamp, using additional heavy plate shims under its jaws.
The power clamp allows you to pre-tighten the nail plates, and then fix them in any convenient way
Lay the details of the second truss on top of the first and fix with clamps, exactly following the contours of the lower truss, which acts as a template. After assembling the second truss, move it to the side.
Make the required number of trusses by repeating the operations from the previous paragraph. This ensures full compliance of all manufactured trusses.
When making trusses according to one template, they will exactly repeat the size and shape of each other.

Installation of the rafter system at the installation site is as follows:

The first two trusses rise to the roof. To do this, you can use an inclined deck of several beams and fairly strong ropes.
The first to install gable trusses at the ends of the roof. They need to be set strictly vertically and fixed to the Mauerlat with temporary jibs.
Gable trusses need to be installed first
A construction cord is stretched between the gable trusses perpendicular to the location of the rafter legs.
Each subsequent truss is installed in compliance with the previously calculated rafter pitch.
In order for all trusses to be installed evenly, twine is pulled between the extreme structures
After the installation of the last truss, the entire structure of the rafter system is reinforced with girders, after which the temporary fasteners are dismantled.
Further, the rest of the structural elements are mounted - jibs, ridge beams, beds, racks, etc., provided for in the project of the rafter system.

The lathing, which is stuffed last, gives additional strength to the roof.

Assembling the rafter legs directly at the installation site

On-site rafter assembly is used on small roofs. At the same time, billets are fed upward, from which the necessary parts are cut. Installation is carried out from the bottom up, starting with the installation of the rafter legs. The horizontal level of the rafter system is controlled by stretched cords, and the verticality of the truss assembly is controlled by a construction plumb line. The installation procedure is the same: first, gable trusses are mounted, then the rest in any convenient order.

The assembly of the rafter system directly on the roof begins with the installation of racks and a ridge girder on which the rafters are laid

Accurately following the requirements of the drawings, you can mount the rafter system yourself. It is almost impossible to do this alone, so the participation of one or two assistants is mandatory.

Video: installing rafters with your own hands

When assembling a rafter frame for a gable roof, it is important to adhere to certain rules:

All wood used for the installation of the truss system must be treated with antiseptic and fire-fighting compounds.
When working with a hand-held power tool, the safety requirements specified in the instructions must be observed.
Installation of nail plates cannot be done by hammering in, this leads to their deformation. A clamping tool must be used during installation.
A waterproofing layer must be laid under the Mauerlat. Roofing material is traditionally used for this.
When installing the rafter system, you must use fasteners with a protective coating.
Installation of the rafter system should be done in dry, calm weather.

Video: gable roof for metal tiles

Like any roofing system, a gable roof requires careful and responsible attitude. Mistakes in the construction of such roofs are usually costly. Not only a careful selection of materials is important, but also their competent use. Nevertheless, the main part of the work can be done independently. I wish you success!

A good foundation does not mean that the house will stand "faithfully" for many years. Another extremely important component is a reliable and high-quality roof rafter system. Let's see how it works in the case of a pitched roof, what types there are and what elements it consists of.

Roof rafter systems

What should be the rafters for roofs

There are several types of rafters that are most often used in modern construction:

metal is difficult to change, but this material is durable;
wooden ones are easy to use and change, but require additional processing;
wooden I-beams (made of timber and OSB) are flat with a maximum length of up to 12 meters, but the cost is higher than the usual wood system;
reinforced concrete cannot be changed at all, but they are distinguished by a long service life;
mixed or combined systems.

Each of them has its own pros and cons, which include strength, price, ease of installation, the possibility of small changes associated, for example, with inappropriate dimensions, interaction with the environment. In this material, we will talk about the most popular material for the manufacture of rafters - wood. let us highlight the main tasks that are posed for structures of this type.

First and foremost - strength of each item. The roof must not deform or move. The basis of the rafters is a triangle. It is in the form of a triangle that trusses (frames) are made, attached in parallel. Fixed and rigid, they “head” the entire structure.

Low weight. A heavy roof is extremely bad. Therefore, most of the elements are made from wood. If the weight of the roofing system is large, then it is reinforced with a metal frame. The basis is low moisture conifers.

What requirements the tree should answer:

1-3 grades. No chips, knots or cracks.
Elements made of wood should not be less than 5 cm in thickness, and with an area of up to 45 sq. cm.
The maximum length of coniferous timber should not exceed 5-6 m.
Mauerlat and purlins are made exclusively from hardwood.

The main structural elements of the rafters

Any owner planning the construction of a rafter system must be aware of what it consists of.

Mauerlat... The basis of the entire structure. With this element, the correct load is established on all load-bearing elements of the house.
Rafter leg... It touches the slope of the slope, gives the roof an attractive look, reliably fixes the structural parts of the system.
Tightening... Does not allow legs to "disperse". Holds them firmly at the bottom.
Run... Attaches the rafter legs to the top of the system (ridge girder) and to the sides (side girder).
Lathing... It is mounted strictly perpendicular to the beams. It is made of cut timber or boards.
Racks / struts... They "add" even more stamina to the legs.
Overhang... Protects the main structures of the building from various natural precipitations.
Ridge... The place where the slopes are fixed.
Filly... Create an overhang. Needed when the rafters do not have the required length.

Details of rafter systems using the example of a gable roof, which can be used for various roof structures

Let's take a look at such a component of a rafter system as a truss. It is made flat, and, in addition to stretching, braces and the beams themselves are included in it. All these parts are fixed in such a way that the load on the main structures goes vertically.

In the case when the span is quite large, then the truss is made of several components. The lower part of the truss is the attic ceiling. The exact number of farms is determined after serious calculations at each specific facility.

Types of truss systems for different types of roofs

All design options are determined by two main types of rafter systems: hanging and layered.

Hanging

Ideal for gable roof types, with small spans up to 5 m, without internal partitions. The lower support is the Mauerlat. In such a system, tightening is used, which reduces the expansion of the structure onto the main pillars of the building.

Suspended roof structure

Hanging rafter beams are located at the bottom - they also act as floor beams. In the case where the slabs were made of reinforced concrete structures, they can also be system ties.

Important additions:

Do not use your legs as the main support for your roof overhang. A more optimal option is a filly (provided that the overhang is no more than 1 m wide). The leg, with this solution, transfers the load along its entire plane to the Mauerlat.
When the wood has a moisture content of more than 20%, it is worthwhile to prepare in advance for the fact that after drying the system will begin to "walk". The solution is to use bolts as fasteners, which can always be tightened. But, even more "advanced" option - "powerful" mounting screws.
At the top of the roof, it is imperative to fix a wind board (it should go from the Mauerlat itself to the top of the ridge). The corner is organized from the attic. This is necessary to create the most durable roof that is resistant to wind loads.

Fortified

They are used for roofs with spans of 9-15 m. At the top, such rafters are attached to the ridge girder, at the bottom - to the Mauerlat.

Roof rafter system

If the span is more than 15 m, then instead of the ridge run, two lateral ones are mounted, which are additionally attached to the racks. In the case when an attic will be created, a wall is used as a support for the layered beams.

Peculiarities:

Any structural part of such a system should not be thicker than 5 cm.
The surfaces of the elements should be as smooth and finished as possible.
You need to be very careful when calculating the loads on each structural element.
The Mauerlat should be located strictly in a horizontal position relative to the vertical supports.
Symmetry must be adhered to when installing struts with struts.
Good ventilation is a guarantee that your rafter system will not rot in the future.
Good waterproofing is needed at the points of connection of elements with stone or brick.

Depending on the shape of the roof chosen by the developer, its frame will also be different. We suggest exploring the different options for the most popular top house designs.

Shed roofs

They are made at an angle of 13-25 degrees, such roofs have the simplest (in terms of manufacturing and installation) rafters. In the case of a small building with spans up to 5 m, a layered system is used. In the case when the spans are more than 5 m, trusses are additionally used.

Gable

It's also a pretty simple option. Especially when an attic or an attic floor is equipped under such a roof. Tilt angles - 15-63 degrees. If the main partitions are located at a distance of up to 6 m (relative to each other), hanging rafters are mounted. For the running dimensions of the house 6x6 or 9x9 meters, we recommend using the following roof schemes.

Recommended installation diagram of a hanging type truss system for a gable roof

Increasing the size of the house, it is necessary to modify (strengthen) the structure. In such cases it is necessary to use layered technology.

Gable roof options for spans over 10 meters: use of a layered rafter system

Hip or hip

Rules for the construction of the rafter system of the hip roof

With inclination angles of 20-60 degrees, and spans no more than 13 m. A prerequisite is internal reinforcing elements. For roofs of this type, trusses are used, or rafters for layered roofs are mounted.

Broken roof

Installation of rafters of a broken roof

In its lower part, it can have an inclination of up to 60 degrees, in the upper part it is flat. In view of this feature, the attic area becomes somewhat larger. The same types of rafters are used as in the version with hipped roofs. But, farms are recommended.

Additional elements

To create the most durable roof, each component of the structure must be very firmly connected to the frame and other elements. In this case, it is extremely important to take into account the strength of the wind and the direction of possible mechanical loads.

Moreover, it is worth paying attention to wood as well. It can crack due to drying out. Therefore, it is important to create a structure in which each element will "work" as smoothly as possible.

Previously, all structural elements of the rafters were fixed with cuts. But, it was not a very "cheap and economical pleasure", since it was necessary to take wooden elements of a large cross-section.

Methods for attaching the rafters to the Mauerlat and ridge girder

So, today, not cuttings are used for fasteners, but special bolts and pins:

Anti-corrosive metal pads are another option for fasteners. They are mounted on system elements using toothed plates or nails. The advantages of such mounts are as follows:

Low consumption per unit of wood.
Ease of installation.
High clamping speed.

Perforated fasteners: corners, plates, beam support

Features of the installation of the rafter system and gable roof Mauerlats

Installation diagram of the rafter system in the case of a gable roof

I - mauerlat, II - rafter leg, III - overlap.

Using narrow rafter legs is a “straight path” to sagging the system in the future. To prevent this, you need to use a special lattice - reinforcement, which includes struts, struts and crossbars. To create it, you need to take wood 2.2 cm thick and 15 cm wide, or use wood plates with a minimum diameter of 13 cm.

Roof rafters - the supporting structure of the slopes. It consists of elements that can be interconnected with crossbars, spacers, uprights, etc. The material for the support beams, in addition to the most common - wood, can be anything - metal, reinforced concrete or mixed.

Table for calculating the rafter system depending on the distance between themselves and the length

Wood (timber) should have a cross-section from 40 to 150 to 100 to 250 mm. This figure depends on the distance of the legs from one another, and the number of sedimentary loads for a particular area (the calculation is carried out separately).

The board should not be more than 5 cm in cross section. Width is directly proportional to length. For example, if your board is 5 m long, then its width should not be less than 13 cm. The main material of the roof sheathing is also important. When choosing it, you should pay attention to the presence of knots, chips and cracks. If you cannot find the most even wood bars, then the maximum length of the knots should not be more than 1/3 of the wood's thickness.

The last step in the installation of roof rafters is to securely fasten each element. Brackets and metal corners are the most optimal elements for this purpose. But, in modern construction, bolts are increasingly used.

How to make a rafter system with your own hands? What are the options for attaching 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 professional techniques when creating a gable rafter system.

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

The device of the rafter system. Nuances

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

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

Cut- conjugation (connection) of wooden parts by creating an anchor and a seat, or a link or stop from the body of the tree of the element itself. Basically, the places of the cut are reinforced with various anchors - a wooden chop, a threaded rod (hairpin), self-tapping screws, turboprops.

1 - roof overhang; 2 - wall; 3 - beam; 4 - bed; 5 - intermediate rack; 6 - the height of the attic; 7 - central rack or "headstock"; 8 - rafter; 9 - the working part of the rafters; 10 - skate; 11 - projection of the working part of the rafters

The rest of the basic terms are given in the previous articles.

Their function in the support area can significantly affect the design of the rafters. Supports are of three types.

1. Support without cutting and cutting. It is used only on temporary, auxiliary buildings, or for a roof that does not bear significant loads. In such cases, a powerful wedge is installed in size.

Support without cutting: 1 - rafters; 2 - wedge; 3 - beam; 4 - armopoyas; 5 - mauerlat

2. Support on a full cut or end cut. The rafters are supported on a beam or Mauerlat on the area of the entire cut or on the end tooth. In this case, to create a roof overhang, a filly is built up or an additional counter-lattice is mounted. Usually, this method is resorted to when the length of the slope is approximately equal to the length of one unit of material (board, timber) 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 - cut; 5 - studs with nuts; 6 - rafters

3. Support on the intermediate cut. The rafter leg remains solid from the ridge to the edge of the roof, that is, the extreme part of the rafter leg performs the function of the overhang. The most common option with a slope length of more than 5 meters. In this case, the splicing of the rafters is inevitable. The notch provides additional grip 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 an intermediate cut: 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 carpenter's tool kit:

Power tools - circular saw, jigsaw, powerful drill with a set of "feathers" for wood.
Hand tools - saws, an ax, a hammer, a sledgehammer, a set of chisels, locksmith keys.
Measuring tool - tape measures, levels, hydrolevel, as a rule, a cord, a plumb line.

Training

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

Rafter leg support assembly. Here it is necessary to take into account local conditions - the material of the walls and the distance between them.
Skate. This is an equally important area and the method of connecting the rafters must be selected in advance, based on the dimensions of the projection of the rafters, the span and the thickness of the beams.
The choice of material for the truss system. If nodes are selected that provide for a through screed in width, then the thickness of the rafter leg must be at least 60 mm. If the rafters of such power are not needed, choose another version of the rafter support (for example, "in the overlay").

Cut overlay: 1 - cut on the side of the beam; 2 - departure; 3 - studs with nuts; 4 - top view

Hanging rafters for small span

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 a floor beam or a rafter girder. We will consider two options for installing rafters.

Option 1. With subfloor

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

Operating procedure:

Arrange a rough floor from unedged boards and scrap material.
Mark out the Mauerlat or beams - a step, notches. Pull the line over the future skate. Be sure to check the perimeter.
Apply material for the rafters to the floor.
Choose the best option for attaching the rafters in the place.
Craft two roof trusses *.
Install end trusses using temporary struts (lighthouse trusses).
Check for correct installation, compliance with levels and tolerances.
Make and install the rest of the trusses according to the size of the lighthouse trusses on screws and nails. At the same time, it should be possible to correct the pitch and dimensions.
After all trusses have been installed, the levels and tolerances must be checked again.
The final loosening of the rafter system is the installation of ties, brackets, turboprop and other elements provided for by the project.

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

Option 2. Without subfloor

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

Operating procedure:

Measure the dimensions carefully at the place of installation.
According to the local dimensions and conditions, choose a method of supporting the rafter leg and the ridge tie, the option of cutting the slope.
Create a polygon that repeats the dimensions of the span and the projection of the rafters. On a horizontal grate or workbench, install a system of stops that guide the board to the design position in the truss.
Build one experimental roof truss.
Lift the truss to the place of installation and install it on temporary fasteners.
Select a cutting method locally and make a cutting for an experimental farm.
Correction of dimensions, angle and structure, if necessary.
After reaching a high-quality landing, finally fix the nodes of the truss and lower it to the landfill.
Correct the stops of the polygon (workbench) according to the template.
Build the required number of roof trusses using the experimental truss as a template.
Make cuts or footprints at the anchor points.
Install and unfasten a number of trusses in the design position.

Often the project provides for the unification of space on large spans - up to 9 meters. In this case, hanging rafters with a rafter are also required. Such projects must necessarily take into account three points:

The rafter leg must be made of a board with a thickness of at least 75 mm and a width of 200-250 mm.
All cuts, support points, mating points 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 joiner's glue.
The level of installation of the rafter girder (tightening) is from 1/2 to 2/3 of the attic height.

Otherwise, the technology for installing rafters repeats the described options.

Rafters

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

Under the vertical supports, a bed should be installed - a board or timber with a thickness of at least 60 mm.
Since roof trusses have a larger number of elements, they are only assembled locally. For this, you may need a scaffolding device.
Mauerlat is an obligatory element of the system. It should be fixed to the armored belt with anchors and connected at the corners with half-wood cuttings.

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

Installation of rafters. Operating procedure:

Install Mauerlat. Usually it is mounted on the inner plane of the 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 - only through a cut-out with fixation with brackets or ties.
Install a row of central supports on the bed, securing them to the design position with temporary rods (rail). Attach a temporary or permanent ridge run to the tops.
Temporarily fix the rafter foot board in the desired design position. Moreover, it does not need to be cut or trimmed in advance.
Correct the ridge girder.
Mark the seats on the headstock, rafter leg and Mauerlat and make cuts.
Install the rafter leg in the seats, measure and check for correct installation. Correct the footprints if necessary.
Make cuts and cuts for the entire row of rafters of one slope, observing the step.
Make cuts and cuts on the rafter board for one ramp (wing) according to the template.
Install a row of rafters of the ramp on temporary clamps (screws, corners).
Adjust the opposite roof slope in the same way.
Check for correct fit and tolerances. Fasten the trusses with a transverse crate.
Install the beds under the intermediate supports (if any) and the supports themselves.
Mark and cut in place the cut of the roof slope and install, if necessary, a wind board.

A variant of the rafter system device: 1 - wall; 2 - Mauerlat; 3 - bed; 4 - rack; 5 - rafter; 6 - "grandmother"; 7 - run; 8 - ridge run; 9 - intermediate cut; 10 - cut in half a tree; 11 - studs with nuts

Rafter step

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

This rule also applies in the opposite direction: The thickness of the board for the rafters should not be less than 1/10 of the step of the rafters (along the axes).

The most popular step - 600 mm between the inner planes of the sinus - is due to the standard width of the slab (sheet) of mineral wool insulation, which enters such a sinus without undercutting. In this case, the thickness of the board should be 60 mm.

Rafter length

c 2 = a 2 + b 2, where
a - projection of rafters
b - attic height
c - the 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 in place, trimming the ends after installation. This makes it possible to make the ends smooth. The optimal constructive roof overhang is 600 mm.

When creating roof rafters with your own hands, remember the danger of unreasonable savings. The rafter system, like the load-bearing walls and foundation, is an irreplaceable element of the building. This means that a complete dismantling is required to replace it. As a rule, this happens during reconstruction or major repairs. If the rules described in the article are not followed, this procedure may be required after 2-3 years.