Why are sliding supports for rafters needed? Sliding support for rafters - device, functions, application. Application of screw jacks

The mobility of roof fastenings is used in the construction of multi-pitched roofs made of materials that shrink.

First of all, we are talking about wooden elements roofs wooden houses.

Connections with several degrees of freedom allow you to create a balanced design.

Despite all its mobility, it must be strong so that it can be used in areas with soil fluctuations, as well as where there is a harsh, snowy and windy winter.

Purpose of moving connections

Wood shrinkage, which occurs natural reasons- the main reason for the misalignment of the entire roofing system.

Minor deformations will occur in any case.

They are mainly associated with seasonal weather changes.

So, for example, when the heating is turned on (this is usually 5 - 6 months in a row) the walls wooden house are subject to shrinkage more than in warm, dry weather.

In this case, the central wall is more likely to settle than others.

And this is due to a decrease in its volume with loss of humidity.

Noticeable deformation occurs during the rainy season (mainly in autumn) and during the cold season (winter).

In autumn, constant high humidity leads to an increase in the volume of walls.

In winter, the walls dry out due to minimal humidity, reaching almost their minimum size.

If the rafters are rigidly attached to the wall, the deformations of the wooden house will in any case be transferred to the roofing system.

And then, a measured and clearly calculated roof (except, of course, for the mobility of the joints) will shrink in the center.

Another possible option is that bumps, irregularities, and noticeable depressions will appear along the entire plane of the roof.

Not only will such changes negatively affect the condition of the entire house, but it is also impossible to eliminate the defects without completely dismantling the roof.

Therefore, in order to avoid such a negative result (the investment of money during construction is practically the same for both sliding and monolithic supports), it is best to equip the system at the points where the supports are attached to the walls with elements that can move slightly.

When creating a roof project, you need to rely on what kind of house it will crown, as well as the area in which it will be used.

Any movable support has a fixed frame of movement.

Features of sliding joints

It is advisable to use sliding joints in places high humidity, and also when condensation forms when water gets under the roof slopes.

Any wooden house will change its physical properties for several years after construction.

In any case, on rafter leg it is necessary to make a cut to ensure a tight stop in the mauerlat (for information about what shape and depth it can be, read the section “Installing sliding joints”).

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The rafter junctions require a certain freedom of movement.

This can be achieved in three ways:

1. On the sides of the leg, long nails are driven into the log.
2. You can drive one large nail on top.
3. For fastening, it is sometimes advisable to use metal brackets or plates.

Whatever the method of fastening, the rafter must be extended to the required length beyond the wall.

The sliding joint gains the ability to move due to its design features.

Types of movable joints

Method of fastening the main structural elements rafter system varies depending on the type of system.

The fastening elements themselves are made of low-carbon steel, hot-dip galvanized.

All sliding joints that can be used in modern construction, are divided into two types:

1. Open connections.
2. Connections closed type.

For complete fastening of movable joints, it is important to determine the uniform distribution of the load on the walls of the building.

It is necessary to take into account the weight of the rafters and the total weight of the entire roof.

Open connection

There are only two here open element.

The first is the guide, which must be attached to the rafter leg.

The guide is a steel plate, curved and having holes at the edges.

There may be two or three at each end.

The stroke length of the moving element is minimum value 60 millimeters, and the maximum is 160.

An angle is a fixed part of an open type sliding joint.

It can have a maximum of five holes.

Closed connection

A closed sliding joint cannot be disassembled into individual elements.

This is only a monolithic single structure.

Its installation on the roof is only possible in assembled form.

The fixed part of the system is made in the form of a corner.

Its long side has a holder into which the fastening bar is threaded.

If logs and boards, theoretically, can be prepared independently, rafter connections best to buy from finished form, in a specific way for high-quality installation roof quantity.

Photos of sliding supports for rafters

Purchasing connection elements

The roofing system, like all other construction elements, must be calculated in advance.

To select elements, it is worth knowing that the percentage of shrinkage of logs in a wooden house, where the beams have a diameter of 195 millimeters, is 6%.

This indicator is accurate for the first year of operation.

Over the next 3 -5 years it will be 2 - 4%.

To select sliding joints, it is worth determining:

• what is the approximate weight of the entire roofing covering;
• expected snow and wind loads on the roof.

These indicators are enough for selection.

They are attached to each rafter.

The average price for one connection is 100 - 180 rubles.

You can buy these elements in construction stores or at construction bases.

There are also Internet resources that sell products online, including those for roofing.

Naturally, it is also possible to purchase sliding joints there.

Installation

Sliding supports are two parts: a guide and a bent plate.

During operation, the guide slides within the bent plate.

A priori, they must be mobile.

But it is important that it does not come off the mauerlat (load-bearing log) under any load on the roof.

Sliding joints are always attached perpendicular to the rafters.

Therefore, the cut in the beams should be made at an angle of 90° to the rafters.

The design features of the installation of sliding elements are as follows:

1. A semicircular cut is made on the support of the rafter leg.
2. One or two spikes are installed (the number depends on the angle of the roof), which relieve the load from the entire rafter system.

There is another way to attach sliding joints.

Special cuts are made in the load-bearing log to 3/4 of its diameter.

This creates a little friction on large area, which makes it possible to hold a heavy structure in strong winds and under heavy snowfall.

This method of fastening sliding joints is advisable when the roof slope is small, as well as when intermediate supports are required for additional fastening.

Installation of the sliding system can be done with self-tapping screws.

The roof, which contains sliding joints, must be correct and geometrically correct in shape.

Installation of rafters should take place only after checking the perimeter of the objects and its compliance with certain dimensions.

All rafters must be the same size.

This will make installation much easier.

And minimizes the “fitting” of elements.

Using movable joints, not only rafters and walls are attached, but also ridge joints.

True, there are slightly different elements here, but the principle of operation is very similar to sliding joints.

To prevent jamming of the moving systems, each support of the sliding rafters must be secured parallel to each other and perpendicular to the supporting mauerlat.

Operation of roofs with movable joints

Streamline the physical, natural processes during the operation of a wooden house with wooden roof possible when installing a roof with elements of a sliding system.

The wall located directly under the ridge is more susceptible to subsidence.

And smaller - the outer, outer walls of the house.

A properly designed roof of a wooden house can withstand significant snow loads(up to one and a half meter snow layer) provided that movable joints are present in all structural connections.

Twice a year (after winter and before it) it is worth carrying out an audit connecting elements systems.

This will ensure that the system not only has not lost its strength, but also remains strong.

If any screws come out of the holes, it is better to tighten them or completely replace them.

The roof of a wooden house with a sliding connection system should not be insulated inside.

Firstly, this will enable the elements of the system to fulfill their purpose.

Secondly, this will make it possible to inspect the connecting elements.

Sliding support for wooden rafters can be used in the roofs of wooden houses that are operated in more severe climatic conditions.

A correctly calculated system will enable the roof to be strong and withstand a large number of snow, as well as ground vibrations and strong winds.

Moreover, the installation of such a system practically does not increase the cost of the entire roof.

Video about the sliding connection of rafters.

The design of any roofing system is difficult process, in which only professionals should participate. When constructing any type of roof, the most difficult and serious stage is the construction of the rafter system.

Today, rafter systems can be of several types. We propose to consider in this article one of the most common types - sliding rafter systems. So, we will look at the main nuances that need to be taken into account during their construction, and also learn about their functions.

The construction of rafters must be approached with great responsibility. If you make any mistake, the structure of the roof may be damaged, which will lead to its destruction. In addition, this may have a negative impact on the building itself.

To build a roofing system correctly, you first need to start preparing its main elements.

Among them are:

• Ridge - the top element of the roof. Based on the first skate made, a mandatory template is made, which will then help to produce the elements necessary for the skate;
• Extended boards for home big size. In this case, you need to make special holes for the bolts in the docking board. They must be drilled using a drill bit - only in this case the wood structure will not be damaged.

The developer must not forget about weight when installing a roofing system roofing material, as well as about various types of precipitation. As you know, our country experiences snowy winters, during which a large amount of precipitation falls in the form of snow.

Wood shrinkage also plays a big role during the calculation of the roofing system. In this case, it is necessary to proceed from the dimensions of the log section. For example, with indicators such as 195x195 millimeters, the total shrinkage along the eaves or fronts should be 6%.

When all the important elements have been calculated and prepared, you can begin the construction of the rafter system.

sliding rafter system consists of the following elements:

• roof ridge;
• rafter leg supports intended for intermediate beams;
• rafter leg supports intended for eaves overhang.

To attach the roof ridge, you need to purchase docking plates. As for the support of the rafter legs to the intermediate beams, in this case a rafter slide is needed. Such sliding elements are often used in the construction of rafters.

Sliding supports for rafters must be attached to each rafter in a perpendicular position (more details: " "). Slides for rafters must be made with precise cuts in the beams. Correct installation there will be rafters only if the element is installed at an angle of 90 degrees.

The slipper can be installed in the very emergency situation. In this case, maximum progress of the rafter system will be ensured in the further process of shrinkage of the house. That is, wood shrinkage will not affect the condition of the rafter system in any way. When the process has stabilized, the permanent material can be installed again. roofing. Pay attention to the photo - they show the main elements of the sliding rafter system. The sliding support for the rafters is also shown here.

How to use sliding rafters

The device of sliding rafters is perfect for houses made of beams and logs. The photo shows some options for such buildings. As you know, houses of this type are settled at first, so roofing system must be properly thought out. Sliding rafter fastenings are especially important in this regard. In this case, the rafter legs are attached to the frame. This is typical for a log gable.

As is known, shrinkage log houses, accounting for almost 10%, occurs unevenly. This factor affects the condition of the entire building structure.

Usually sliding ones are attached to the rafters made of wood on the ridge log. In this case, the rafters can be connected end-to-end or overlapped. For this purpose, steel plates, bolts and nails are used.

The choice of rafter section will depend on the weight of the roof. Perfect fit edged board 50 millimeters thick and 200 millimeters wide.

The rafter legs cannot be attached rigidly to the mauerlat, as in this case the walls of the log house may burst, as well as the roof sagging. Sliding fastening of rafters involves the use of special brackets. They are usually made of two millimeter high-strength steel. They are also equipped with a corner that allows the support to slide. Such brackets can be purchased at any hardware store behind inexpensive price. The guide line of such a mechanism must be attached strictly parallel to the rafters. The corner on the log should be located in a perpendicular position.

Only in this case, during the shrinkage of the house, there will be no distortion. The corner should be attached at the level of the ruler at which further sliding of the rafters along the entire length is permissible when the process of shrinkage of the house occurs.

How the rafters are attached

The rafter must be correctly and securely attached. If it is simply rested against the beam, then with some force in the future the end of the rafter may begin to slide a little. This factor will ultimately lead to the destruction of the entire roofing system.

Thus, the rafters must be securely and correctly fastened. In this case, elements such as a tooth with a tenon and a stop, a tooth with just a stop, and a stop at the end of the beam are used.

The angle of inclination of the rafter will determine how many teeth the connection will take. It is usually done using one or more teeth. Using this method, the pressure of one element is transferred to another element.

If the roof slope is large, then it is better to use single teeth to connect the beams and rafters. Usually the angle of inclination in this case is more than 35 degrees.

• It is necessary to make a tooth with a spike in the heel of the rafter leg;
• You need to cut a certain stop in the beam. It must have a socket for placing a spike. The depth of the tenon in this case is approximately 1/3 of the thickness of the beam. Too much great depth can weaken it;
• At a distance of 25 - 40 centimeters from the edge of the hanging beam, cutting occurs. In this way, you can avoid chipping its end under the load that may be caused by the rafter in the future.

As for single teeth, they usually have spikes, which in the future eliminate the possibility of the rafter leg shifting. This connection method is called a tooth with a tenon and a stop.

If the slope of the roof is, on the contrary, less than 35 degrees, then in this case the friction area on the floor beam must be increased. Thus, it is necessary to cut with two teeth.

It may have the following options:

• two stops, that is, to go with a spike or without a spike;
• have two stops with spikes;
• have a lock with 2 spikes.

There are other options with two teeth. The first method is the most common. In this case, a tenon with a stop for one tooth is cut into the beam, then it is cut out for the second tooth. Then an eye with a stop for the 1st tooth is made in the rafters, a stop is cut out for the 2nd rafter. The teeth should cut to the same depth at this moment.

Rafters can be connected by tightening, but this method is less common. In this case, a stop tooth is cut out in the rafter leg. One tooth plane is then placed on the edge of the beam surface. The second plane of the tooth should rest against the cut, which was specially made in the beam. The depth can be 1/3 of the beam thickness.

The basics of constructing a rafter system for a wooden house, details in the video:

You can make the structure of the rafter system strong and reliable using bolts and clamps. Loops made of wires or iron strips will help attach the entire corner to the wall of the house. In this case, there should be an anchor bolt in the wall of the house, or a crutch embedded in the wall.

The rafters are connected using the following elements:

• dowels, plates, bars, insert or overhead triangular scarves - wooden roofing elements;
• bolts with washers, nuts, nails, screws, hinges, clamps, linings, etc. – metal roofing elements.

The rafter system must be properly attached. Only then will its design be reliable and last long years. The installation of sliding rafters must be approached with special responsibility, since they are made on wooden houses, which shrink in the first two years.

Wooden roof structures are subject to deformation. This is due to changes occurring in the geometry of the wood during the process of natural shrinkage. Therefore, when constructing a roof, technologies are needed that make it possible to prevent its expansion or sagging.

A rigid mount is completely unsuitable for solving such problems. When choosing nails, brackets or other similar options for fastening rafters, for example, you should first think about whether the structure is prone to shrinkage. Of course, this problem is not new, and traditionally the solution has been to use twisted, tear-resistant wire. It reliably connected the rafter legs to the upper crown of the frame, leaving a certain degree of freedom for the elements of the supporting structure.

Currently, there is a more advanced method that was specifically developed for these cases - a sliding support for rafters. Among its advantages are ease of installation, reliability and durability.

Sliding support for rafters: what is it for?

Any wooden structure, regardless of what material it is built from - timber or logs, a carriage or a half-carriage, will certainly begin to change in size, and quite noticeably, a few years after commissioning.

Changes in wall dimensions significantly affect the rafter system. The behavior of its elements in the ridge connection and in the places where they rest on the wall is different. In the first case, the rafters “try” to rotate around an axis, in the second - to rotational movement another progressive one is added.

If the rafters are rigidly fixed to the walls, then they will transfer the deformation of the structure to the roof, and for some time it, which seems so reliable at the beginning, will begin to sag in the central part, the slopes will bend, etc.

The only way to avoid complications of this kind is to allow the rafters to move at the connection points without changing their shape. This is exactly what the sliding support for the rafters serves. It works more effectively in structures made from solid pieces of wood, in which there are central walls that run parallel to the ridge beam.

Production and price

Typically, rafter legs work in non-standard conditions. Mostly this is high humidity or condensation and moisture that has entered the under-roof space. They are made from steel with a low percentage of carbon, which makes it quite easy to process the metal. To increase the strength indicators, the products undergo a deoxidation process.

Sliding supports (photo below) are made by cold stamping. The material is protected from corrosion using a galvanic coating obtained by processing it using hot-dip galvanizing technology. This prevents premature failure of the metal fastening.

If the factory protective coating is not available, the sliding rafter support should be coated before installation. oil paint, which takes on the function of anti-corrosion protection.

These systems, like all others, are calculated in advance. For example, when purchasing for log house the degree of log shrinkage is taken into account:

• 195 mm beams give a shrinkage of 11.7 mm for the first year.
• in three to five years – another 2–4 percent.

When choosing, also take into account:

• approximate weight of the coating;
• the estimated force of loads on the roof from wind and snow.

The cost of these products on average ranges from 100–180 rubles.

Types and characteristics

This element has a composite structure, open or closed. It includes:

• a guide that is attached to the rafter;
• a metal bracket, a corner, bent in a certain way by 90⁰, having a support platform.

The corner has a loop along the top, which is put on the guide. With this approach, the rafter beam acquires a certain degree of freedom. It can move in a certain direction for a period corresponding to the length of the guide. The sliding zone provides the roof with a margin of displacement, as well as stability during shrinkage of the house.

Dimensions of the sliding support for rafters:

• the length of the support varies in the range of 10–48 cm;
• height – 9 cm;
• width – about 4 cm.

The sliding support is often called perforated.

What sliding rafter supports should be installed?

The following types are distinguished: similar supports or slides:

• open system consists of two separate elements. There are two or three holes at both ends of the guide. How many of them there will be on a particular product depends on its manufacturer. For example, on the sliding support of rafters pa1 78 120 there are two of them, and on Kucis models there are three. They also differ in the stroke of the moving part - 60 and 90, respectively. The number of holes on the supporting part of the angle is at most five.

• closed installed already assembled as a single structure. To fasten the plate to the log, you must first cut a notch, the width of which coincides with the width of the L-shaped section of the sliding fastening. Otherwise, the movement of the elements will be hampered, and the resulting friction may cause kinks or damage.

You should also pay attention to the ridge connection rafter elements. When walls are deformed, as a rule, the angle of their articulation with the ridge also changes. Therefore, in order to prevent deformation of the roof plane and or balance the displacement, it is recommended to use a sliding support for the rafter system on the ridge. Among other things, this approach makes installation easier. Thus, reliable support in these cases can be ensured without the need for complex cuts on the elements of the supporting structure.

Application

Wood shrinkage can be caused by different reasons, say, humidity, sudden temperature fluctuations, etc. But whatever the reason, the result will be the same - the shrinkage of the wood also sets the rafters in motion - they tend to change their position in relation to other elements of the rafter system. Of the walls, the one located under the wall shrinks the most. ridge beam, as for external walls, then their shrinkage is less.

Functionally, a sliding support is needed to firmly fix the rafters to the wall and support beam in vertical plane. The connection, which has several degrees of freedom, allows you to balance the structure. By compensating for shrinkage, they allow you to maintain strength and resistance to loads from snow and wind.

Often, a similar method of fastening is also used in cases where it is necessary to fix elements of a certain structure so as to allow them to move in relation to each other. Consider the example of a bathroom in wooden house, if you plan to partially tile its wall. First of all, it is sheathed with materials such as gypsum fiber board or OSB. This is done using a pre-fabricated frame, which, which is extremely important, is “floating”.

This is due to the fact that after some time the walls may begin to settle. In addition, they regularly experience seasonal deformations. The problem can be solved only if two conditions are met:

• lining not completed to the end of the wall;
• securing the frame using sliding supports.

Installation

There are two options for installing supports for rafter legs. They are either installed in pairs, that is, on one and the other side of the rafters, or only on one. Single-sided fastening is possible only in regions with low levels of loads from snow and wind and for structures with low mass. In all other cases, double-sided fastening is recommended.

Installation of supports begins after making the ridge connection and making a cut in the support beam. The length of the stroke must correspond to the calculated displacement value by which the rafter legs move when the walls shrink and deform under the influence of heat and humidity changes.

Attention!

It is important to take into account that if the insert into the Mauerlat is made deeper than ¾ of it, this can significantly weaken the roof structure.

Let's note some design features installation:

• A fixed component of the support is attached to the upper log. The fastening is carried out on a flat platform, previously ground on a beam.
• The second component part of the support is attached to the rafter leg, which, in turn, is fixed to the ridge either on sliding or hinged joints, which allow the slope of the rafter legs to change in relation to the ridge beam.
• During installation, the guide strip must be positioned parallel to the rafter ribs.
• The corner loop, which is located on the guide bar, should initially be located in its lower part, since the rafters, when the walls shrink, sit down.
• The sliding support area in mandatory positioned strictly at an angle of 90⁰ with respect to the axes passing through the center of the rafter legs.
• Fasteners are made using self-tapping screws that have an anti-corrosion coating.

Organization truss structure for arranging the roof in the future in a wooden house is a responsible undertaking.

The slightest mistake over time can lead to the complete destruction of the object, in best case scenario- to the loss of their own technical characteristics(tightness).

To ensure the integrity of the truss structure and the roof as a whole, while at the same time taking into account the features wooden structure(its shrinkage), sliding rafters are used.

Any construction material wooden house - an ordinary log, profiled, laminated timber, which shrinks during operation. It continues for the first 2-5 years after construction.

It consists of the loss of natural moisture from the log, which cannot be removed artificially during material processing. The percentage of natural shrinkage can be 5-8% of the total volume of wood.

However, the danger lies not in the presence of shrinkage, but in its unevenness. That is, each log loses moisture to a greater or lesser extent.

As a result, the design of the rafter system, which is connected to the masonry in a rigid way - using iron brackets or bolts, occurs. Rafters with broken geometry cannot act as a reliable support for the roof. The latter, in turn, sags and loses its tightness.

Thanks to the special design, they can compensate for uneven shrinkage of the logs, thereby maintaining the correct geometry of the roof.

What is the “sliding rafter” system?

Sliding rafters in a wooden house consist of two elements - a metal bracket and a hinge with an angle.

They are made of high-strength material - steel, grade 08 PS, which contains a low percentage of carbon - 0.08% (according to GOST 14918-80).

It is thanks to this that the bracket and hinge can withstand the entire load of the rafter system for a long period of time, without losing their integrity.

Standard characteristics for sliding are as follows:

• thickness – from 2 mm;
• 40 mm width;
• up to 90 mm in height;
• length is in the range 90 mm – 160 mm.

The principle of operation of the system is as follows: the bracket is fastened with bolts to the rafter, the loop is attached to the log. Thus, the structure moves relative to each other, thereby compensating for the change in the geometry of the building and the skew of the roof.

Before you start organizing moving rafters, you need to take into account several nuances. Experts in this field provide the following series of recommendations:

• installation is carried out only on a geometrically correct object. Since the sliding rafters are a movable system, it will be impossible to make adjustments in the future, and the fastening elements in the process of shrinkage of the building will not cope with their task. Before starting work, it is recommended to measure the perimeter of the object and adjust it to the recommended tolerances;

• You can make the fasteners yourself. But each of them must be made according to the same template in order to maintain consistency in size;

• The fastening must also be movable. This can be done using movable hinges mounted with self-tapping screws;

• If the building is large, it is often necessary to build up the rafters for a high-quality ceiling. This is done by overlapping with bolts into pre-prepared holes. They are made using a drill, the dimensions of which must correspond to the parameters of the bolts used. The location of the holes should be random and not reach the edge of the board by at least 10 cm. These measures will prevent delamination of the material;

• each subsequent rafter must be attached strictly parallel to the previous one and strictly perpendicular to the supporting log. Otherwise, there will be disturbances in the operation of the sliding rafter system.

Installation technique for sliding rafters

Since the above system is a dynamic (moving) structure, it will not be possible to simply install it on top of a support log. In this case, it will fall under its own weight.

To do this, a semicircular cut is made in the support log. A spike is also made on the rafters, its angle should correspond to the angle of the roof. This will remove the load from the system and transfer it to the support log.

The depth of the cut should not exceed ¾ of the diameter of the log, otherwise it may collapse. The emphasis is also placed on a depth of no more than ¾ of the beam. If you don't stick this condition, will weaken load bearing capacity designs. The notch is made 30 cm from the hanging edge of the beam.

Modern construction includes the construction of buildings of the most various types, but at the same time, roofs with several slopes continue to retain their leadership as the most promising. In the case of wooden buildings, there is a high probability of shrinkage, which leads to deformation of the structure. This means that a design element is required that allows it to adapt to changes in configuration. Such an element is a sliding support for rafters.

What are they?

With the help of such supports, the rafters are attached to the supporting beam, resulting in a balanced structure. This part is also used in other cases - when it is necessary to connect several sliding elements with a fixed base.

If you are interested in what it looks like, you can see it on our website.

More information about the rafter system pitched roof garage read in a separate section.

In addition to giving the rafter structure additional strength, sliding supports have many advantages, one of which is ease of installation, which does not require special tools and skills.

Using a sliding support reduces costs manual labor during the construction of the roof, since in this case there is no need to manually balance the parts of the roof structure.

Functions and characteristics of sliding supports

The purpose of the sliding supports is to attach them to the mauerlat during the construction of log and timber houses. These perforated elements have proven their effectiveness many times: the sliding method of fastening prevents hanging roofing structure and bursting of the walls of a wooden building.

Absolutely all buildings created from solid wood (this includes chopped and rounded logs and profiled timber) are subject to natural shrinkage. As a result of shrinkage of the rafter system of a wooden structure, the structure weakens and significant distortions are possible. Floating rafters made using sliding supports solve this problem.

The components of these fasteners are a metal bracket and an angle with a loop. Basically they have the following parameters:

• height: 90 mm;
• width: 40 mm;
• thickness: 2 mm;
• length: from 90 to 160 mm

Since the rafter system must withstand heavy loads, all fasteners used, including sliding rafters, must be made of durable and reliable materials. Low carbon steel, which is the material used for making sliding fasteners, meets these requirements

The process of installing a roof structure using these fasteners is not difficult: it only requires a screwdriver.

Scope of use of supports

The process of shrinkage of wooden houses is especially intense during the first few years of operation. Changes in the shape and size of the structure are mainly due to changes in temperature and humidity levels. In this case, the height of each individual log or timber changes, resulting in a general change in the height of the wall, which consists of changes in the parameters of each element separately. From the above, we can conclude that as the height of the wall increases, the degree of its shrinkage during operation also increases. The wall located under the ridge has the maximum height, which means its shrinkage is the greatest.

The walls that serve as support for the rafters located along the edges of the house are subject to less shrinkage. Over time, this process leads to a change in the angle of the roof. For this reason, it becomes necessary to take into account the data of geometric changes when attaching rafters and ensuring the mobility of connections.

The rafters located in the ridge are created to rotate relative to each other, securing them on both sides with the help of metal-based plates on studs.

The lower edges of the rafters present a certain difficulty, since during shrinkage they not only rotate, but also move relative to the wall. The device of a rigid and fixedly fixed fastening of the rafter leg to the wall will lead to its bulging as a result of shrinkage.

For rafters, it is necessary to ensure the possibility of a not very large, but still noticeable rotation and a certain shift along the wall without reducing the degree of strength of the fastening. In earlier times, annealed wire was used for this purpose. With its help, the top log was tied to the rafter leg. This technique ensured the mobility and reliability of the created fastening..

Sliding supports for rafters have become an effective, most convenient in terms of installation and a replacement for the described method that meets all requirements. When using it, the rafter leg is securely fastened to the beam or log of the mauerlat. If laminated timber is used in the rafter system, this method becomes the only one that simultaneously provides the necessary mobility and strength. The location of the fastening is the area along the displacement of the beam. To do this, the wood of the top beam is ground down. The result is a platform - the fixed lower part of the support is attached to it.

When performing installation, the support must be positioned in such a way that its shift reserve is the maximum possible.

As a rule, the rafters are fastened on both sides of the rafter leg, however, with a low roof and a small slope of the roof slopes, you can limit yourself to one fastening.

The rafter leg, which has intermediate supports between the mauerlat beam and the ridge, must also be secured with a sliding support.

Manufacturing of sliding supports

In most cases, these parts are operated at high humidity and often come into contact with water and condensate penetrating under the roof slope. When manufacturing sliding supports, it is necessary to take into account the strong impact of these and other negative factors external environment. For this reason, they are pre-coated with a layer of molten zinc, additionally alloyed with other substances to reduce susceptibility to corrosion and improve strength characteristics, thereby increasing the overall load-bearing capacity of the structure.

The sliding supports themselves are manufactured by cold stamping on the basis of a fairly strong and ductile material - low-carbon steel grade 08 PS. The percentage of carbon in it is 0.08%, which makes it possible to stamp the material with high quality. Balancing the strength characteristics of the element is carried out by deoxidation.

Types of sliding supports

All currently used sliding supports are divided into two groups:

Open type- such structures are composed of two separate elements. The first is the guide attached to the rafter leg. This is a curved steel plate with holes at the ends. There may be two or three of them at each end - the specific number depends on the manufacturer. The stroke length of the moving element also changes. Lowest value should be 60 mm, the largest - 160 mm. The corner (the fixed part of the element) has up to 5 holes.

Closed type– this type of support cannot be disassembled into its component parts and represents an integral structure. Installation is carried out in assembled form. With this option, the fixed part has the shape of a corner with a special holder on the long side: a fastening bar is threaded into it.

Installation

Sliding rafters are installed when the material for the gables is logs or beams, and the ridge purlin is fastened in the body of the gable. This requirement is necessary to prevent the walls from expanding when the roof slope angle changes during shrinkage.

The rafters are laid on ridge run on top and secured with a hinge joint. In this case, it remains possible to change the angle at which the rafter legs are connected.

The manufacture of such a connection is made on the basis of perforated plates connected by pins. The second option is to overlay upper parts and connection using studs with washers and nuts.

In this case, certain conditions must be met:

1. Mauerlat connection (in in this case– the upper crown of the log house) with rafter legs is carried out using sliding supports. As a rule, their sizes correspond to the following parameters:

• 90 x 90 x 40;
• 120 x 90 x 40;
• 160 x 90 x 40;
• 270 x 90 x 40 mm

The choice of length is determined by the expected displacement of the rafter legs.

Other uses for sliding supports

Sliding fasteners can be used anywhere when there is a need to ensure the movement of parts wooden structures– for example, when creating linings and partitions for wooden buildings.

CONCLUSIONS:

• The sliding support for the rafters is very important element roofing structure, allowing to compensate for distortions of the rafter system that arise during operation due to wood shrinkage.
• With the help of such supports, the rafters are attached to the supporting beam, resulting in a balanced structure.
• The sliding method of fastening prevents the roof structure from hanging and the walls of a wooden building from expanding.
• The components of these fasteners are a metal bracket and an angle with a loop.
• The production of sliding supports is carried out by cold stamping based on low-carbon steel grade 08 PS.
• Sliding supports are of open and closed types.
• “Slippers” are mounted at a 90-degree angle with respect to the rafter support using special cuts. This method ensures unhindered movement of the structure.
• The sliding supports are secured using self-tapping screws with a protective coating.
• To ensure the possibility of sliding with the maximum possible shrinkage length, the guide line of the sliding support must be laid parallel to the rafter leg, and the angle is installed perpendicular to the leg in the upper part.

Find out how rigid and sliding connections of rafters are made from the video.