Over time, wooden truss structures can be damaged due to heavy snow loads, rot due to moisture, and become deformed due to errors in roof calculations or installation. rafter system. The cause of damage to the rafters may also be the use of quality material- damp, rotten boards with a lot of knots. In these cases, repair or strengthening of the rafters is necessary.

Also in the process of creating a rafter system, structural reinforcement is performed. This means using various racks, struts, jumpers that distribute the load. Without them, the rafter legs would have to be made very thick and heavy, which would increase the load on the walls of the building. Without such additional elements You can only get by in small buildings - garages, bathhouses.

What is the reinforcement of rafters?

May be required

• increasing the load-bearing capacity of rafters,
• strengthening the rafter legs in the lower part, at the junction with the Mauerlat,
• strengthening damaged rafters,
• increasing the roof slope angle and building a new rafter system,
• strengthening the nodes of the rafter system in case of poor-quality connection of elements.

To strengthen the rafters, beams and boards are used; they must be of the first grade and well dried. It's better to take conifers tree. Also, to fasten the elements of the rafter system to each other you will need metal corners, perforated plates and wire.

How to increase the load-bearing capacity of rafters

The need to strengthen wooden rafters may arise if they are not strong enough to withstand deflection, even if their cross-section is suitable for the load that falls on them. For this they use

• unloading beams (help),
• struts,
• double sided pads.

The supports are placed between the mauerlat and the rafter leg (strut). They are attached using bolts or special plates with teeth.

Double-sided overlays are used to avoid deflection of the rafter leg at the point where it rests on the strut. It is at this point that the maximum bending moment occurs. With the help of overlays, the cross-section of the timber in the problem area is increased. The covers are secured with nails or special bolts.

If the rafters are bent, they are straightened using a jack (hydraulic cylinder), and then strong horizontal struts are inserted to hold the connected rafters straight. This creates a design in the shape of the letter “A”.

Important! Before straightening the rafters, it is necessary to strengthen the place where they meet the Mauerlat so that the rafter legs do not jump off the beam while the jack is in operation.

Creating a new rafter system

Also, sometimes when reconstructing a roof it is necessary to make a new rafter system; with its help you can, for example, make the slope steeper. The need to increase the slope angle arises if snow accumulates on the roof and creates a large load on it. New rafters are installed above or below the old ones. In such cases, in order not to disassemble the old truss structures, new ones associate with them.

For the connection, a cross board-and-nail wall (truss) is used: new rafter legs are connected by cross-positioned boards to the existing ones. Most often, this method is used in layered rafter systems, which rest on a wall located in the center of the building. This technique cannot increase the height attic room.

How to strengthen the lower part of the rafters

Reinforcement of the rafters in the lower part is usually required at the junction with the Mauerlat. The lower parts of the rafter legs adjacent to the Mauerlat, and the Mauerlat itself are considered the most vulnerable parts of the rafter system.

To strengthen the rafters, additional struts are installed at the junction with the Mauerlat. They can rest either on the Mauerlat itself or on the bench. Sometimes it may be necessary to cut out the rotten part of the Mauerlat. Then the rafter is reinforced as shown in the figure.

The rafter is temporarily placed on supports, and the rotten parts of the rafter leg and mauerlat are cut out. Crutches are hammered into the wall and a beam 1 m long is placed on them. You can also put a piece of beam 1 m long on the wall or ceiling, this way the load will be distributed from one beam to two. Two struts are attached to the rafter leg on both sides, which rest against the mauerlat or bench.

The struts are attached to nails arranged in a checkerboard pattern. In this case, the struts are placed at an angle, as in the figure, in order to better distribute the load.

If the lower parts of several rafter legs have rotted, then they are temporarily installed on supports, the roof is dismantled, the rotten sections are sawed off, and then a rod (metal) prosthesis is made, which is put on the rafters and rests against the mauerlat. , thus resting on the prosthesis. The rigidity of the prosthesis is ensured by struts.

Replacing damaged parts

To replace rotten rafters, first remove roofing material on both sides of the house. In this case, the damaged part is cut out and the rafters need to be extended in length.

When replacing a horizontal beam, install temporary posts on which the horizontal beams will rest, then remove and save the posts that supported the damaged beam, replace the beam and place the posts back. Temporary stands are being removed.

If you need to replace the rack, then first install a temporary rack nearby, supported by a board at least 2.5 cm thick. Next, the damaged rack is removed, a new one is put in its place, then the temporary support is removed.

Strengthening the ridge unit

The connection of the rafters at the ridge is one of the most important units in the rafter system. It is important here that the boards fit together tightly. If you find that the rafters have separated at the ridge assembly, you need to join them using a jack and secure them using a wooden overlay (boards at least 20 mm thick) or a perforated metal strip that is attached under the ridge. You can also use special bolts.

Bay window connection

The bay window roof can be separate or connected to the main roof of the house. Its shape can be very diverse: gable, multi-gable, complex hip. The simplest option — gable roof. To construct a bay window roof, a mauerlat is installed around the perimeter. In brick or concrete houses The reinforcing belt is first poured, and the Mauerlat is installed on it.

The rafters for the bay window roof are thinner than for the main roof, since the load on them is less. They are installed in such a way that they protrude beyond the Mauerlat, forming a roof overhang. How to connect rafters in a bay window, watch the video:

The bay window can be included in the house design immediately or added later.

How to extend the life of rafters

The rafter system begins to rot due to moisture ingress, which can occur as a result of poor air exchange in the under-roof space or leaks. It is important to make a good hydro- and vapor barrier of the roof.

If the air exchange is insufficient - this can be checked by measuring the temperature at the upper boundary of the insulation layer; it should not be more than 2C at any temperature below zero outside - make additional air vents. The total area of ​​vents and dormer windows should be 1/500-1/300 of the roof area. If loose insulation is used, which tends to cake, then it is loosened once every 5 years. If necessary, the thickness of the insulation layer on the ceiling is increased; near the external walls it can be doubled compared to the calculated one.

Conclusion

By strengthening the truss structures, it is possible to eliminate deficiencies or damage that occurred during the operation of the building or during its construction. Most often, reinforcement is required at the junction of the rafter legs with the Mauerlat. To ensure that the rafters do not rot and serve for a long time, it is important to ensure good air exchange under the roof and use high-quality materials.

The Mauerlat belt is the basis for the rafters. The lifespan of the entire roof depends on how strong you make it, how you secure it and think through the connection with the rafter system. So what is a Mauerlat for two pitched roof, what to make it from, how to mount it on a brick, frame wall and wall made of hydrophobic gas blocks? What pitfalls might there be and what mistakes should you avoid? It is precisely in order to answer all these questions that we have prepared this useful article for you.

By the way, if you heard from builders or a foreman you know such a word as murlat, this is the same mauerlat, only in common parlance. This is exactly what we will be talking about.

Mauerlat is a stable structure that is laid around the perimeter of the walls and serves as the basis for attaching the rafters. The main task of the Mauerlat is to distribute the loads of the roof overhangs as evenly as possible and firmly tie the roof itself to general design Houses. In other words, this is the same connecting link between the walls and the roof, and therefore it is necessary to proceed with its manufacture especially responsibly.

The secondary task of the Mauerlat is to reduce to a minimum the so-called windage of the roof, i.e. its ability to be torn by the dashing wind.

But why then, if this is so important, are there roofs without any Mauerlat at all? Yes, such a practice exists. The rafters are simply attached to the floor beams, if they are strong enough. But in this case, all the concentrated loads of the roof fall on the places where the rafters support, whereas the Mauerlat would distribute them over all the walls. What do you think is better and safer?

What materials can it be made from?

This roofing element made from wooden beam, I-beam, channel or metal.

Option #1 – durable timber

So, depending on the future weight of your roof, use timber with the following cross-section as the material for making the Mauerlat: 10x10, 10x15, 8x18, 15x15 or 20x20 cm. You just need to place it under the rafters along the entire perimeter of the roof to evenly distribute the load on walls of the house.

So, if you have already chosen wood for the mauerlat, pay attention that the knots on it in no case exceed two-thirds of the thickness in their length. What's the catch? The fact is that knots are dangerous not because of the release of resin, as many people think. It’s just that these places on the beam will ultimately work poorly in tension, and yet the Mauerlat is the one that experiences the heaviest loads of all other roof elements. What are the consequences of a poor choice of wood for this purpose? Cracks!

Option #2 – bonded boards

But, if you are building lightweight frame house and no special loads are planned on the roof, then save money and instead of heavy solid timber Use fastened boards as a mauerlat.

Option #3 – steel pipes

Often, additional beams made of steel pipes are used when constructing the Mauerlat. It looks like this: the wooden Mauerlat no longer protrudes beyond the perimeter of the building, but pipes are attached to its ends, which serve as the main support for gable roof. Moreover, there are a number of serious requirements for pipes:

• Small section. The pipes pass through holes in the rafters.
• Exceptional strength. The whole roof is on them!
• High quality steel. It is important that such support element did not deform over time.

Make holes in the rafters strictly along the axis, with a diameter 10 cm less than the height of the rafter leg. If this does not work, attach additional steel elements. Steel pipes work well for bending, and the fact that they require small holes round shape- also good. Such “damage” has almost no effect on the strength of the rafters themselves.

The main advantage of this design is that here the wooden Mauerlat is hidden under the roof, and is already more protected from smudges and melting snow.

Mounting the Mauerlat on the wall: 2 ways

So, we selected the material and made the Mauerlat. Now let's decide whether he needs reinforced belt. They are usually built on walls that are not strong enough so that the future roof has something to rest on:

Method #1 – installation without armored belt

But even for a strong overall building, a reinforced belt will not be superfluous, because It’s convenient to make special fastenings for the Mauerlat through it.

Method #2 – installation on an armored belt

The most difficult thing is to make a mauerlat on aerated concrete - the most fragile wall material. We advise you to make a structure on it for this purpose from more durable brick or concrete, because... the Mauerlat needs a solid base. But just an armored belt will do. Moreover, you can easily cope with this important construction task:

Calculate the thickness of the reinforced belt based on what loads will act on your roof: as constant, in the form of the weight of the rafter system and roofing, and temporary, in the form of winds and snow. But in any case, the width of the armored belt should not be less than that load-bearing wall. The minimum limit is 25x25 cm. And do not forget that the pressure on the main walls of the house is exerted not only by the Mauerlat, but also by those posts and ridge beams that rest on the internal floors. And for them, too, you need to build an armored belt.

To make the reinforced belt strong, use a concrete grade of at least M400 and pour the entire belt in one go. Of course, for this it is advisable to use a concrete mixer with a pump. To prepare the mixture, take cement, washed sand and crushed stone in a ratio of 1:3:3. Additionally, add modern plasticizers to reduce the amount of water used in the mixture and thereby increase the strength of the future belt.

Additionally, this will help you figure everything out short video:

We construct the formwork

It is important that the armored belt is continuous on both sides external walls Houses. And special U-shaped blocks can serve as a kind of formwork for constructing an armored belt. You can also complete the outer row with sawn blocks up to 10 cm wide, or build formwork from OSB boards. Even ordinary people will help wooden boards. But, no matter what formwork you make, be sure to check its upper edge with a water level.

If, due to some design feature of the building, you still have to interrupt the reinforced belt, then do it according to the same successful principle as in this project:

Choosing a mount

On frame walls and walls made of logs or Mauerlat timber are fastened with screws, self-tapping screws and even ordinary nails. For greater strength, special perforated connectors are used.

Also, if the area of ​​your house is large and the roof is at least 250 m2, then you need to attach the Mauerlat to the walls with studs. Studs are long metal pins with threads, which are distributed at the place where the Mauerlat is attached so that it happens at least every 2 meters, plus always at the ends.

First, an armored belt is poured around the perimeter of the walls - concrete screed, and then the studs are embedded vertically, one after another. The height of each should remain greater than the thickness of the Mauerlat, and remain at least 3 cm higher. This is the only way you can firmly tighten the Mauerlat with nuts and a washer.

As you can see, nothing complicated:

And another way:

Strong metal brackets for attaching the Mauerlat are also convenient to some extent:

And also do not forget about anchors and twisted wire, which works great in tension:

Using wire rod - thick wire - is the easiest method of all. So, between the rows of bricks, 3-4 rows before the top masonry, a piece of wire is placed in the middle so that the ends are enough after finishing the masonry to tie the entire mauerlat. Then the remaining ends are hidden in the thickness of the wall between the bricks.

They do it differently. It is not the studs that are embedded vertically into the reinforced belt, but the pins of the reinforcement itself so that they are lower than the height of the mauerlat. And studs of only 4-5 cm or long bolts with pre-cut heads are already welded to them.

Another popular method is that pins or studs are embedded during the laying process. brick wall. But this technique is only suitable for small roofs, and for greater reliability, take longer studs.

We reinforce the belt

So, if you don’t use any of the things proposed to attach the Mauerlat, then simply leave the protruding rods from the reinforcement, and put the beam itself on them after the concrete has hardened. So, even on the shortest wall, the armored belt should have at least four metal rods of 12 mm in diameter - for attaching the Mauerlat. Moreover, with such rods you can not only string the Mauerlat, but also secure it with outside:

But in any case, even if you chose pins or wire, there should be reinforcement in the belt.

Fill with concrete

When making such an armored belt, make the thickness of the concrete at least 5 cm. As soon as the concrete is laid, make sure that no air cavities form in the armored belt - you will notice them by bubbles. Why is this bad? All this reduces the strength and uniformity of the structure, but on the belt you still have to install a mauerlat - the foundation of the roof. Therefore, simply pierce the concrete with a reinforcing bar along its entire length, and the air lenses will disappear.

The formwork must be removed on day 10-12, when the concrete has already gained its strength.

We put waterproofing

But this point is required!

Place a layer of roofing material as insulation or another similar layer on the finished armored belt waterproofing material. A tree is a tree, and it is better for it not to come into contact with wet wood.

All the subtleties and nuances of installation

Your most important task when installing the Mauerlat is to constantly check the levelness building level. If you find an unevenness, even a small one, correct it immediately: cut off the protruding parts, and raise those that are below the level using linings.

Now prepare a beam that will serve as a mauerlat. Treat it with a disinfectant and fire retardant (against fire), and dry it well. Attach the beam to the future location of fastening and make marks where the holes will then be drilled. Connect the individual parts of the Mauerlat with a straight lock and additionally secure them with nails at the places of such connections.

Fasten the timber at the corners with a straight lock or an oblique cut - whichever is more convenient for you. Attach the Mauerlat to these boards using corners, dowels or metal brackets. But for the sake of economy, just don’t use the board that was fixed in advance in the upper groove of the SIP panels (if you are building from this very material) - this is completely unreliable and is fraught with future distortion of the roof, destruction of the panels themselves under the weight of the roof and other disastrous results.

And finally, secure all connections on the Mauerlat with locknuts, and cut off all protruding studs with a grinder.

We build a “bench” on the Mauerlat

As soon as the Mauerlat is laid, we proceed to the construction of the so-called “bench”:

• Step 1. Measure the distance between the opposite Mauerlats.
• Step 2. Divide this distance in half and mark the middle of the span.
• Step 3. Connect the marks so that you get the axis of the future “bench”.

It is along this axis that you will lay the bottom run. Most convenient option– make the “bench” with the bottom girder immediately intact, in a horizontal position, and then lift it and secure it vertically along the axis of the floor.

Fastening the rafters: all popular methods

Because the main task maueralat to distribute the loads from the roof, be sure to pay special attention to attaching the rafters to it. The fact is that it depends on whether the roof will move over time, whether it will begin to sag or create stronger loads on one of the walls. This is serious!

There are two technologies for tying rafters to the Mauerlat:

• Tough. Here, any displacement of the rafter leg, bends or shifts is completely eliminated. For stability, a hemming block is used, which prevents the rafter leg from slipping. And the metal corners prevent the rafters from moving to the sides.
• sliding. Such fastening is necessary if the house was built from logs or timber, which noticeably settle over time. And the Mauerlat itself is usually not used here - only the upper crown of the log house. If you use a rigid rafter fastening system, then next year the roof will lose up to 50% of its strength - it will simply collapse.

And now about everything in more detail.

Rigid fastening of rafters to the mauerlat

Most often, when constructing a roof, wooden rafters are used, as they are the most affordable and easy to process. But wood is bad because it quickly absorbs moisture and swells just as quickly, although it returns to its previous size after drying. And it is especially important to correctly fasten the wooden rafters to the mauerlat in order to prevent the formation of the so-called expansion force during a wet hike. Which, in turn, can significantly reduce the durability and reliability of the entire structure.

The main task of rigid fastening is to completely eliminate the possibility of rafters moving in any direction. Here, the saddle of the cutout on the rafter is rested against the Mauerlat and firmly fixed with nails driven at an angle. But it is extremely important that all such cutouts on the rafters are the same, according to the same pattern and no more than 1/3 of the width of the rafters.

The second method is single fastening with a special fastening plate. Additionally, in some cases they are hemmed under the rafters meter beam, which also serves as a stop, and the fastening is done with a metal corner.

A sliding mount is also called a hinged mount, and for good reason. Keep in mind that different wooden houses shrink in different ways. So, laminated veneer lumber sags the least over time, and the most is a fresh log house, which drops to 15% in just a year! Moreover, the shrinkage itself always occurs unevenly, which has an even greater impact on the distortion of the entire rafter system - if you have not installed a sliding fastening.

Roof distortion also occurs during the operation of the house itself. Thus, during prolonged rains, wood swells greatly, and in winter it loses a large percentage of moisture and dries out noticeably. Moreover, they settle in completely different ways:

• south and north side;
• the side that is constantly exposed to wet river or sea ​​air, and drier;
• the side blown by the winds and the one in front of which there is a utility building;
• hidden from the sun by a tree and open.

All this time geometric parameters log houses are constantly changing. Moreover, even the central wall of the house, on which the racks and beams of the rafter system rest, changes its parameters. Especially during the winter heating period, when it dries out noticeably. Therefore, if the rafters on the mauerlat or the upper crown of the log house are firmly fixed, then in winter snow load will cause the rafter system to bend.

Therefore, the node needs to be a little free, for which you will need such fastener, like a “sled” or “slider”, as people like to call it. This is a special metal part that looks like a loop. When the geometry of the log house naturally changes, it moves along the guide, and the rafters settle a little without any harm to the entire system.

Here's more detail about the process itself:

By the way, some roofers still perform a sliding angle more traditional ways. To do this, they make a cut in the rafter leg, place the beam with a cut on the upper crown and secure it in the following ways:

• With staples.
• Crossing nails in the mauerlat.
• One nail driven vertically.
• Stylish fixing plates.

Also, as a good alternative to a modern sliding support, use strong forged wire, twisted twice (we talked about it in the paragraph on attaching the Mauerlat to the wall). It works well in tension and gives a certain degree of freedom to all elements of the roof structure.

As you can see, everything can be sorted out!

In order to increase the load-bearing capacity of rafter legs in all types of rafter systems, it is necessary to strengthen the rafters. To do this, use the installation of unloading beams, or, as they are also called, supports, and double-sided overlays and struts.

Main types of roofs. All types of roofs have their own rafter system.

As practice has shown, rafters selected according to strength characteristics are not always confirmed by deflection calculations according to SNiP “Loads and Impacts”, and therefore it is necessary to increase their cross-sectional area. Reinforcing the rafter legs is very simple: just include an additional wooden beam - help. The help is attached to the lower belt of the rafter leg in the span between the Mauerlat and the rafter leg. The rafter reinforcement is secured with metal toothed plates or bolted clamps.

In a continuous rafter leg there is another dangerous knot - leaning on the strut.

A simple example: if you break a stick over your knee, it turns out that in this case the knee is the brace. Therefore, the largest bending moment occurs at this location. Since there can be no deflection in this node, the cross-section along the entire rafter leg can be increased using reinforcing double-sided board overlays. In other words, you need to increase its width, not its height. The dimensions of the linings are selected based on the required cross-section, which is determined by calculations for the maximum bending moment.

The covers are secured with bolts, bolt clamps or regular nails. If it is already reinforced with help, then you just need to make it longer and bring it beyond the edge of the support on the strut. In this case, we solve two problems: we achieve satisfactory deflection indicators in the span and strengthen the support unit.

Sometimes during reconstruction it is necessary to choose a steeper roof slope. In this case, the old and new rafter elements are joined together using a board and nail cross wall. In this case, new rafters can be installed both below and above the old rafters. The truss formed as a result of these actions provides increased rigidity and a new slope. This method makes it possible not to dismantle the existing rafter structure, which significantly speeds up the work, but it does not increase the under-roof space. If you do this to build an attic, you should know that the volume of the attic will not increase.

Scroll necessary tools and materials:

• axe;
• hammer;
• nail puller;
• wood saw or hand-held circular saw;
• square;
• building level;
• pencil;
• roulette;
• drill;
• drills d=4-10 mm;
• timber (the cross-section is the same as that of existing rafters);
• board 25-40 mm (determined by calculations);
• fastening materials: nails, staples, clamps, self-tapping screws.

Reinforcement of the bottom part of the board and nail truss

Often the most vulnerable part of rafter structures is the lower parts of the rafter legs, which rot over time, or the Mauerlat itself. In this case, the problem can be solved with the help of additional struts. Additional struts attached to the lower end of the rafter leg, which, in turn, rest against an additional beam or mauerlat beam, make the support unit more reliable. To ensure better stability of the truss structures, it is recommended to slightly move the lower ends of the additional struts apart. In order to partially reduce the deflection in the span between the Mauerlat and the rafter leg, the struts can be supported by an additional support.

If you use raw wood(humidity above 25%) and with insufficient ventilation attic space, Mauerlat and lower ends of rafter structures can rot over time. Rotting can occur in roofs of any type when the wood of the mauerlat or rafters is moistened, when the wood is moistened from the masonry, or in the absence of a waterproofing layer between the wall masonry and the wood. In addition, this may be a consequence of damage to air vents, vapor barriers, or clogging of their ends in the structure of an insulated attic roof.

Methods for restoring and strengthening damaged structures

There are several ways to strengthen and restore damaged structures:

1. Installation of wooden overlays. They are used when single rafter legs are damaged. Wooden overlays are secured with nails or bolts. Thus, with their help, the damaged section of the roof is strengthened. The linings must rest on the Mauerlat with their entire end and are attached to it using twisted wire.
2. Installation of rod prostheses. This method is used for massive damage to rafter structures. First, the damaged area is secured using temporary supports. rafter leg. After this, the covering is dismantled and the rotten part of the rafter leg is cut out. Then, exactly the same element is prepared from a new beam (the so-called “prosthesis”), which is inserted in place of the rotten one and rests on the mauerlat.
3. Application of overlays resting on the beam. This method is suitable when replacing a rotten section of the end of a rafter leg or a section of a mauerlat. Areas of rotten structures are cut out, having previously strengthened the rafter leg with temporary supports, and a beam about 1 meter long is laid on the crutches driven into the masonry. Then a piece of wood of the same length is laid on the ceiling or wall. After this, two struts secured with nails on both sides of the rafter legs rest against the new beam.

Attic ventilation

Strengthening the rafter system is important, but not the only part. For her long-term operation There must be sufficient air exchange in the attic. With insufficient air exchange in the attic, with wood rotting and the development of fungal spores in wooden structures roof, it is necessary to carry out measures to restore ventilation. In the attic there are additional ventilation and dormer windows. Cross-sectional area to area ratio attic floor should be 1:300 - 1:500.

It is also necessary to find out what the air temperature is at the upper boundary of the insulation (at any negative outside temperature air it should not exceed 2°C), study the nature of air movement. Caked insulation needs to be loosened approximately once every five years. When the thickness of external walls is up to 1 meter, it is better to increase its actual thickness by 50%, since over time it thermal insulation properties are getting worse. The width of the vents should be within 2 - 2.5 cm. It is also necessary to check and restore, if necessary, the vapor barrier under the insulation layer.

Strengthening truss structures may be required in cases where errors were made at the design or construction stage of the structure. Incorrectly calculated loads or material properties can lead to partial deformation of the roof, or even to its complete destruction. In this case, the reinforcement of the rafters becomes acute necessary procedure, which can save your home.

The rafters, which are the basis of any roof, must be periodically checked for any defects or damage caused by the use of the roof. If any are detected, it is necessary to strengthen and strengthen the rafter system of the house, garage, barn, bathhouse or other buildings. Errors during installation and calculations can occur with any type of rafter system, so home craftsmen need the ability to strengthen rafters for each of them.

Strengthening rafter legs

Strengthening rafters can be done in several ways, the main ones will be discussed in detail below. These methods can be used individually or in combination. In each specific case, homeowners must resolve this issue themselves. But it is best not to save money and take into account that the destruction of the roof above the same garage can damage the car and cause significant material damage, not to mention the danger of deformation of the roof structure of the house.

So, strengthening of load-bearing functions is carried out using:

• “help”, beams that take on part of the loads on the rafter structure;
• installation of struts;
• double-sided overlays.

Supports are installed in cases where incorrect calculations of the loads on the rafters have been made, and as a result, an increase in the cross-section of the beams holding the structure of the entire roof is required. It is quite easy to carry out such reinforcement; to do this, you need to install this additional beam and secure it between the Mauerlat and the rafter leg. It is fastened either with bolt clamps or with special steel plates with teeth.

The location of the rafter leg on the strut also requires special attention homeowner, since this is where the maximum bending pressure occurs. For clarity, remember how as a child you broke a stick over your knee; it is the knee that plays the role of the brace. To reduce the load and the risk of deformation of continuous rafters in the place where they rest on the strut, we recommend increasing the cross-section of the beam by covering it with overlays from boards. The thickness of the overlays depends on the calculation of the required cross-section for the structure under the planned bending loads. The rafters are connected to reinforcing linings using various fasteners, but more often with nails or special bolts. If at the same time the length of the support is extended beyond the fulcrum, then it is possible to increase not only the strength of the beam, but also the entire connecting unit.

Sometimes a project may have an error in determining the angle of the roof slope, and operation reveals this miscalculation. For example, if the slope is not steep enough, snow accumulates, which can damage the roof. In this case, it becomes necessary to make some changes to the design of the rafters. To do this, to the old elements using plank walls and nails, new parts of the rafters are attached, due to which the newly formed trusses become more rigid and change the slope of the roof in the desired direction.

This method will allow you to make changes without having to disassemble the entire roof again; however, you won’t be able to make any special changes to the under-roof space, since you won’t be able to either enlarge it or configure it in any way.

Strengthening the lower parts of the rafters

The roof truss structure of any building is most vulnerable in its lower part, which is where it most often requires reinforcement - this is the bottom of the rafter legs and the mauerlat beam. The reason for this vulnerability is that it is in the contact area between wood and brickwork that condensation most often forms and moisture enters if the integrity of the roof is damaged. Another reason is the use of low-quality wood, which was either raw or dried in violation of technology. All this leads to the formation of putrefactive processes in the wood and its destruction. Therefore, during construction, it is important to pay attention to the choice of high-quality material and ensure reliable hydro- and vapor barrier. The absence or improper functioning of ventilation ducts can also cause moisture accumulation and wood destruction.

In this case, struts are used to strengthen the roof frame. They are attached to the lower end of the rafter leg and rest against the mauerlat or leg. The number of such additional struts depends on your situation. To give additional stability, the struts are attached slightly at an angle, that is, their lower part extends slightly to the sides. It is the support in the bed that will allow you to remove the effect of bending deformation on the span of the rafters in this part.

Strengthening rotted parts of the rafter system

If you still cannot protect yourself from the destructive effects of rot on wood, you can try to strengthen the damaged areas of the rafters or mauerlat of your house or garage. If we're talking about In one case of damage to the rafters, you can get by with wooden plank overlays. They are fastened with nails or bolts, while the lower part of the board of the lining should rest against the Mauerlat, to ensure additional reliability of fixation, and it is better to attach the linings in this place to the Mauerlat using steel wire.

But if we are talking about massive damage to the rafters, when deformation or rot is found on many rafters, then it is necessary to use a special prosthetic system. These prostheses are made of steel rods and are attached to an undamaged area of ​​the structure, while the deformed part is simply removed. For this operation, it is necessary to fix the rafter with special temporary supports and remove the damaged part (for this you will have to disassemble part of the roof). Then you should cut out a similar size prosthesis from the same wood and install it in place of the removed area, its lower part should rest against the Mauerlat. The steel rods of the prosthesis provide additional fixation of the entire structure.

If strengthening with partial replacement requires not the rafter leg, but the mauerlat, then the following manipulations must be carried out:

• are fixed with temporary supports of the rafters of the roof frame;
• the rotten section of the Mauerlat is cut out and removed;
• steel spikes are driven into the masonry, on which the timber is laid the required section, at least one meter long;
• a piece of beam equal to the length of the beam is installed on the ceiling;
• then the rafter leg is fixed on both sides with struts, which rest on the newly installed beam.

Work to strengthen the rafters of any roof is a whole complex of works, which includes various operations to correct the deformation and destruction of the roof itself. wooden elements or places of their fastening.

Deformations are most often expressed through curvature and the formation of cracks in the beams and boards of rafters and other wooden roof elements, but sometimes intervention is required when it is necessary to correct poor-quality fastening of parts of the system to each other.

In the latter case, it is worth paying attention to the key connection points. First of all, make sure that the rafters and ridge of your roof are properly secured; problems in this area often arise if you are not careful during installation.

When correcting defects, it is necessary to achieve the tightest possible connection between the rafters and ridge beam, using a special jack can help with this. To qualitatively strengthen this unit, use various techniques. This unit is fastened using either a special steel strip with perforated holes, or various wooden planks, or by placing the rafters on a steel fastening bolt. In each of these methods, several options can be distinguished, for example, wooden overlays can be attached both above and below the ridge beam; there are also several types of metal plates for reliable fixation of rafters and overlays.

There are some secrets when correcting the deflection of rafters. To do this, special wooden stops are securely attached to the inside of the beams, after which the rafters are straightened using a jack, and strong jumper spacers are inserted between them one by one. Such a system will help to resist external pressure on the roof and rafters and stop the deformation of the latter.

When strengthening the legs of the rafters through timber extensions, it is necessary to correctly select its parameters. It should be either equal in width to the rafters or slightly wider. For ease of installation, the timber is secured with self-tapping screws to rafter beam, and then make holes through both elements, after which the entire structure is mounted on special steel bolts or studs.

It is better to drill these holes in a staggered pattern, which increases the structure’s resistance to loads during bending deformation. The diameter of the drill and mounting pins must be equal. Fastening is done with steel studs, self-locking nuts and washers. This design is not only easy to install, but also reliable in operation. It will not come loose and will last as long as the wood can withstand.

Strengthening the rafter system is usually required if during operation the roof cannot withstand the load and becomes deformed. As a rule, this is the result of errors in calculations or installation.

Increasing the load-bearing capacity of rafter legs

The rafter system of a house, garage, bathhouse and other buildings should be regularly checked for damage and deformation. Reinforcing the rafters in a timely manner will avoid roof destruction and costly repairs. In the case of a garage, the car may also be damaged, which is associated with serious financial loss. Gain load-bearing capacity rafters may be required in any type of rafter system. For this purpose, the most common practice is to install unloading beams (“help”), install struts or double-sided pads.

If rafters are selected according to strength characteristics, they do not always have the necessary deflection indicators corresponding to SNiP “Loads and Impacts”. Thus, it is necessary to increase the cross-sectional area of ​​the rafters. Strengthening thin wooden rafters of the roof of a garage or other building is carried out using additional wooden beams- helped. The beam is attached to the lower chord of the rafter in the span between the rafter leg and the mauerlat. A metal toothed plate or bolt clamps can be used as a fastening element.

Particular attention should be paid to strengthening the support unit of the continuous rafter leg on the strut.

At the point where the continuous rafter of the roof of a house or garage rests on the strut, the maximum bending moment occurs. It is necessary to avoid deflection in this unit, which requires increasing the cross-section of the rafter leg with overlays installed on both sides. The dimensions of the board overlays are selected based on the calculated parameters of the section at the maximum bending moment. Reinforcing the rafter leg with board overlays is done using bolted clamps or nails. If you increase the length of the support and move it beyond the edge of the support on the strut, then this beam will at the same time serve as an overlay, strengthening the support unit, in addition to increasing the rigidity of the span.

When reconstructing a roof, it is often necessary to make a steeper roof slope. In order not to completely replace the rafter system of a garage, bathhouse or residential building, new rafters are installed, fastening them to the old ones. The splicing of wooden elements is carried out using a cross board and nail wall. The resulting truss has a given slope and provides increased structural rigidity. It should be borne in mind that this approach does not allow increasing the space of the attic or attic when remodeling the roof.

Strengthening the lower part of rafter structures

The most vulnerable parts of the rafter structures of a garage, house or other buildings include the lower parts of the rafter legs, resting on the mauerlat, and the mauerlat beams themselves. If raw lumber was used during the construction of structures, or the wood is moistened due to roof leaks or insufficient waterproofing between the Mauerlat and brickwork garage or house, the wooden elements rot and the strength of the structures decreases. Moisture ingress or condensation can also be caused by damaged vapor barriers, blockage or damage to ventilation ducts.

To strengthen the roof frame, additional struts are installed. Such a brace is attached to the bottom of the rafter and rests against a mauerlat beam or an additional beam. To increase the stability of the farm structures, it is advisable to move the lower ends of the additionally installed struts slightly apart. By resting the struts on an additional support, you can remove the bending moment from the span between the rafter leg and the mauerlat.

Strengthening a damaged rafter system

If it is necessary to replace a rotten part of the mauerlat or sections of the rafters of the roof of a garage or other building, additional linings are used. Reinforcement with wooden overlays is performed in case of single damage to single rafters. The linings are fastened with bolts or nails, while the lower end of the lining should rest on the Mauerlat beam and be additionally fixed to it using twisted rolled wire.

Strengthening structures with bar prostheses is used in cases of massive damage to wooden rafters. In this case, strengthening involves dismantling damaged parts of structures. The damaged rafter leg is fixed on temporary supports, then part of the roofing covering is dismantled, and the rotten section of the rafter is cut out. A “prosthesis” is made from the new timber - an element whose dimensions correspond to the sawn piece of the rafter. The prosthesis is installed in place of the removed fragment, supported by the Mauerlat.

If strengthening of structures requires partial replacement Mauerlat, strengthening the roof frame is carried out using the following technology. The rafter legs are fixed to temporary supports, and the rotted fragment of the Mauerlat is dismantled. On the crutches driven into the masonry, it is necessary to lay a beam of a suitable cross-section, the length of which should be about 1 meter. A piece of timber of the same length is laid on the ceiling or wall. Then the rafter leg needs to be strengthened with two struts resting on the new beam.

Strengthening pitched roof structures involves a set of works aimed at correcting damage to wooden elements that have undergone biological destruction, or eliminating deformations of rafters and fastening points. Most often, you may encounter a problem such as deflection of the rafter legs during the operation of the roof, but you should also pay close attention to the quality of the rafter fastening even at the stage of erecting the roof of a garage or other buildings.

One of the fundamentally important nodes is the place where the rafters are attached to the roof ridge. If there are discrepancies, it is necessary to promptly correct this defect. The work technology may require the use of a jack to ensure a tight fit of the rafter leg in the ridge part. The place where the rafters join must be properly reinforced. Reinforcement is done using a perforated metal strip or a wooden overlay made from a board at least 2 cm thick. The overlay is mounted directly under the ridge.

Next, you should eliminate the deflection of the rafters. For this purpose, a hydraulic cylinder is activated. Using self-tapping screws it is recommended with inside rafters, attach wooden triangular supports. After which the rafter is straightened using a hydraulic cylinder and a rigid expansion bridge is installed, which prevents deformation of the roof truss under external loads.

To reinforce wooden rafter legs using the beam extension method, it is necessary to prepare a beam of the required width - it must correspond to the dimensions of the rafters, or slightly exceed them. Before securely fixing the reinforcing beam, it is best to secure this element to the rafter using self-tapping screws. Next, you should make several through holes through the rafter leg and the reinforcing beam for fastening the elements with studs.

The holes should be staggered, with a pitch of about 30-50 cm. This fastening principle makes it possible to increase the resistance of the structure under bending loads. The diameter of the holes must exactly match the diameter of the fasteners. Threaded rods are inserted into the prepared holes, wide washers are put on their ends and self-locking nuts are screwed on - this allows you to create reliable fasteners that will not come loose during operation of the rafter system. Tighten the nuts until the sound of cracking wood appears.