Gain 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 rafter system 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 rafters and the mauerlat beam. The reason for this vulnerability is that it is in the area of ​​contact between the tree and brickwork Most often, condensation 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 quality material and provide 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 fortifications 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 wooden elements themselves or the places where they are fastened.

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 on inside Special wooden stops are securely fastened to the beams, after which the rafters are straightened using a jack, and strong 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.

Living on the seaside is a dream for many people. However, in such regions, as in mountainous areas, winds often blow near a lake or river. strong winds. And this factor cannot be ignored when building the roof of a house.

Aerodynamic parameters

The slope angle is the most important value when calculating roof loads. Lateral wind pressure on steep slopes can lead to capsizing.

The wind puts less pressure on flatter structures with a slight slope. This roof shape is suitable for areas with strong winds.

But the roof is too shallow air flow tends to lift, tear down.

When the flow collides with an obstacle - and the structure crowning the building - a vortex occurs: without going into details, we can say that two tangential forces and one lifting force act on the roof. The value of each of these forces depends on the angle of inclination of the slope. A flat roof can be partially protected from exposure - for example, using a laid parapet.

A competent project must be drawn up taking into account geographical location buildings, climate and terrain. Wind resistance is also affected by windage roofing material and the quality of fastening the elements of the rafter system and sheathing.

When constructing the frame, it is not allowed to use any substrates or other parts that can deform over time.

To prevent the roof from being torn off or overturned by a gust of hurricane wind, it must have maximum stability. It is achieved thanks to elements such as braces, struts, diagonal braces - depending on the type of structure, some or all of them can be used in the rafter system.

Exist certain parameters fastening timber laid around the perimeter of the building. It is fixed to the wall in various ways, and at a certain distance from the edge. All fastenings - both the rafters to the Mauerlat and the Mauerlat itself to the wall - must be done carefully.

Additional fastening of the lower ends of the rafter legs to load-bearing walls buildings using metal pins will increase resistance to wind loads.

Everything must be additionally securely fastened with wire twists - if strong winds prevail in the area, and after one - if moderate wind pressure is expected.

Different areas of the roof experience different wind loads - the rigidity must withstand this pressure.

The wind also distributes snow on the roof - and it distributes it unevenly, due to which more snow is blown onto some areas, and the snow pressure increases. Therefore, throughout roofing structure there should be no weak points.

Another important point: not only the connections must be strong - the rafter legs must be made of high-quality wood.

Hip roof

This type is optimal for a house with a square base.

However, the future homeowner must remember that in this case it will not be possible to equip the attic.

Two trapezoidal slopes and two triangular ones - this is what it looks like, usually crowning a rectangular house and having great wind resistance.

This option involves the use of diagonal supports - slanted rafters, running from the two ends of the ridge to the four corners of the house. Such load-bearing frame practically not subject to deformation.

The absence of gables significantly reduces resistance to the wind, which “slides” almost unhindered across the surface.

Dutch half hip type

They are characterized by trapezoidal pediments and hip slopes cut off from the bottom.

It does not have such a sharp protrusion as top structure buildings: truncated end slopes increase the ability of the half-hip to withstand loads.

To arrange such a roof you will not need a lot of materials, and its installation will also be simple.

If you position the slope in the direction of the prevailing winds, it will be reliable: that is, on the leeward side there should be the part that is lower. The same rule applies here: the greater the slope, the greater the wind load.

Roof covering against hurricane winds

Sheet materials have many advantages, but at the same time they have a high windage capacity.

Soft bitumen shingles

This coating is optimal for the upper structure of a building with the most complex configuration.

IN model range There are specially designed types that have a special shape - with increased resistance to wind loads. The shingles are not only glued, but also nailed with special nails - this fastening to the base is as reliable as possible, and can withstand even hurricane winds - up to 220 km/h.

The optimal value of the roof slope when using natural tiles considered 30-60 degrees.

The main arguments in favor of or are its weight and small size. The wind finds it difficult to cope with the weight natural coating, however, if the tiles are torn off, in the event of a fall, this very weight will become a serious threat.

You can increase reliability by securing not only the bottom and top rows, but also the tiles completely along the entire slope - using staples.

The sequence of repair and restoration work on wooden roofs can be reduced to the following basic processes: dismantling the roof in places of destruction, unfastening the remaining load-bearing structures(construction legs, sheathing, truss flooring), removal of rotten or heavily damaged parts, phased restoration (strengthening, repairing, unfastening and bringing in new roof elements), installation of the roof and performance of work to protect and seal mates, joints, nodes, seams, etc. etc., painting and anti-corrosion or fire protection.

Exposed roof structures are inspected, after which a final decision is made on the scope of work to restore them bearing capacity. Weak rafters, racks, braces or sheathing elements can be strengthened by installing overlays and additional supports. Before starting work, the lumber used must be antiseptic and then treated with fire-fighting compounds, for example an aqueous solution of lime and table salt.

Sagging rafters are usually eliminated by adding additional posts and supports after first leveling them with temporary fasteners or a jack. Deformed sheathing can be repaired from the attic side or by opening the roof. New bars or sheathing boards are laid in the same plane with the previously laid sheathing and nailed to each rafter leg, keeping in mind that the joints of the boards and bars should not be located in the same line.

The rotten ends of the rafters are removed by building them up with short pieces or reinforcing them with overlays. In addition, the rafter leg on the mauerlat can be strengthened with struts (Fig. 6.4). The replaced and retained parts of the rafters are fastened together with bolts or nails. Before starting work, temporary fastenings are arranged, the rafter legs are hung to the required height, the damaged ends are removed and the overlay or “prosthesis” is prepared. After securing the latter to the rafters, the repaired structures are lowered onto a previously cleaned and antiseptic Mauerlat and fastened accordingly. At the same time, they must check the quality of the work performed and the serviceability of the roof over the repaired area.

To replace mauerlats and linings, rafter structures are hung in an area of ​​1.5...3 m to the height required for the work. The damaged area is removed, and the remaining

Rice. 6.4. Reinforcing the ends of the rafter legs:

a - double-sided overlays; b - struts; / - decay zone; 2 -

nails 125... 150 mm long (no more than 12 pcs.); 3 - pads; 4 - Mauerlat;

5 - strut; 6 - bracket

After cleaning from rot, adjacent structures are antiseptic. Mauerlats or linings made from timber are connected using notches with suspended structures, laid in their place and secured with permanent fastenings, and temporary supports are removed.

Rice. 6.5. Strengthening existing rafters:

a - for spans up to 5 m; b - the same, up to 7 m;

/ - existing rafter leg;

2 - new rafter leg;

3 - existing strut;

4 - wooden pads

All surfaces of rafter legs, support pads and mauerlats in contact with masonry or concrete are coated with resin or mastic and insulating pads made of two layers of roofing felt, roofing felt or glassine must be placed under them. Weak connections of struts, racks, crossbars, tie-rods with rafter legs or trusses are strengthened by installing clamps, additional staples, twists, overlays, or nailed down.

Sometimes it is necessary to slightly change (usually increase) the angle of the rafters, while simultaneously strengthening them. In such cases, the rafter leg is raised to the required slope, extended in length, and a strut is installed to reduce its working span. This method is applicable for spans up to 5 m (Fig. 6.5, A). For spans of more than 5 m, a change in span is achieved by increasing the rafters in height, which is carried out by cutting a new one into the existing rafter from the eaves side and embedding it into the opposite wall. The existing brace is extended and connected to the new rafter leg. Then both legs are connected to each other with overlays made of boards (Fig. 6.5, b).

Strengthening the rafters without changing the slope is achieved by using a truss. Existing rafters In this case, they turn out to be the upper chord of the truss truss, and the lower broken chord is made of round steel. Sprengel posts are made from

gas pipes.

When completely replacing the roof of a building being renovated, more durable reinforced concrete or reinforced cement prefabricated elements should be used.

Quite often, homeowners are faced with the problem of sagging rafters. This occurs due to excessive savings or incorrect design. If the rafters are not strengthened in a timely manner, they may break, which will ultimately lead to expensive roof repairs.

The concept of strengthening rafters implies a set of works to correct deflection and strengthen them for further trouble-free operation. It is also necessary to process the junction of the “legs” to the ridge, which will additionally remove the load from their middle part.

Strengthening rafters - choosing a strategy, preparing for work

Eat two ways to strengthen the structure. The first is to increase the thickness of the beams, and the second is to increase their width. The first option is used only when for some reason it is impossible to increase the width of the beams, since with the same amount of material used, structures reinforced using the second method have much greater resistance to bending loads.

There are also various ways fastening reinforcing bars to rafters: with wire, nails, self-tapping screws, using threaded rods. The most reliable way to increase the width of the beams is what we will consider.

For preparation for work freeing all work surface from the sheathing, open the rafter attachment points and assemble next tool: kit wrenches, set of miter heads with ratchet, drill, screwdriver, hydraulic cylinder, grinder. Since these jobs are very responsible and labor-intensive, they cannot be performed by one person.

First of all, we pay attention to the fastening of the rafters to the ridge. If they separate there, then first, through the efforts of several people, using a jack if necessary, we join the upper ends.

Then, using perforated metal strips, plywood or, in extreme cases, a two-centimeter board, using self-tapping screws, we strengthen the junction of the beams on both sides. If the rafters are joined at the ridge, then we strengthen the connections under it.

Next we need to remove the deflection of the rafters. To do this, we will use a hydraulic cylinder. Before starting this work, it is necessary to strengthen the joints of the structure to the mauerlat, for which we screw a board from below to the rafter beam (when increasing the thickness) or to the side (when increasing the width), which will rest against the mauerlat beam and will not allow the legs to move apart when working with a hydraulic cylinder.

For good support of the hydraulic cylinder from the inside into the ends of the opposite rafter beams In places of greatest deflection, we screw homemade triangular wooden stops with self-tapping screws.

Next, carefully working with hydraulics, we straighten the rafters and fix them in this position with any available board at least 3 cm thick using self-tapping screws. That is, if you look from the side, it looks like a big letter “A”.

How to strengthen the rafters - we build up the timber

In order to build up the rafters, we proceed as follows. First of all, we prepare a beam identical to the existing one in dimensions (the width may differ slightly). For the convenience of subsequent work, we fix it to the existing beam with several self-tapping screws.

Then, using a drill, we drill through holes 30-50 cm apart immediately through two beams fastened to each other. The holes are not located on the same line, but go in the form of a “snake” to improve the bending resistance of this structure.

Next, we insert studs into the holes, pre-cut to size, onto the ends of which we attach self-locking nuts, having previously placed washers under them. The rafters are tightened until the wood crackles characteristically.

To strengthen the rafters using the second method, we perform the same work and in the same order, except that the reinforcing bar must be fixed to the inner end of the beam and the holes are located on the same line.

It will be necessary to strengthen the rafter system if during operation it turns out that it is not able to withstand the required load and begins to deform. Below we will talk in detail about how to strengthen the rafter system from the inside in order to eliminate all errors that were made during calculations before installation.

Strengthening the rafter legs

First, it is worth noting that the rafter system of a house, garage, bathhouse and other buildings must be checked in a timely manner for possible damage and deformation. Timely reinforcement of rafters will help prevent possible roof damage and huge repair costs. If the garage roof is damaged, the car may suffer. Rafter reinforcement may be required for any type of rafter system. To do this, expansion beams are often installed - “supports”, struts or double-sided overlays.

If the selection of rafters was carried out taking into account the strength characteristics, then their deflection forces will always correspond to the required indicators, which are regulated by the relevant SNiP “Loads and Impacts”. It turns out that we will need to increase the cross-section of the rafter legs. To strengthen thin rafters, wooden supports are used. They are attached to the lower chord of the rafters in the gap between the rafters and the mauerlat. In this case, the fasteners are steel toothed plates or clamps with bolts.

How to strengthen correctly and reliably - rules for strengthening a roof structure

Particular care must be taken in strengthening the element of support of the continuous rafter leg on the strut. This is because there should be no deflection in such a place, which means that the cross-section of the rafters is increased with the help of overlays that are installed on both sides. The dimensions of the overlays are determined based on the design parameters of the section with the maximum bending moment. Fastening of board overlays is carried out using bolted clamps or nails.

An installed support can also serve as an overlay if its length is increased and it is brought beyond the limit of support on the strut. In this case, it will not only give the span additional rigidity, but will also be able to increase the support capabilities of this unit.

In some cases, to improve performance characteristics roofs, steeper slopes are made for it. In this case, the old frame can not be disassembled, but a new rafter system can be assembled and connected to each other. Such strengthening of rafter structures will make it possible to new roof more rigid, however, the under-roof space, which serves as an attic or non-residential attic, will not increase. The structural elements can be connected to each other using rafter joints on both sides, secured crosswise.

Work to strengthen the rafter system

Most often, the mauerlat beams and rafter legs in their lower part are destroyed. This happens as a result of poor waterproofing of the Mauerlat from brick wall due to the leakage of rainfall and melt water through roof covering, or due to the initial installation of insufficiently dried lumber. In addition, moisture ingress into wooden structures may occur due to clogging. ventilation ducts or violation of the integrity of the vapor barrier membrane.

You can reinforce the roof rafters in their lower part using auxiliary struts. These elements are fixed to the lower edge of the rafter leg with an emphasis on an additional leg or mauerlat. You can give the resulting truss additional stability if you slightly move the lower ends of the struts apart. If you place the emphasis of the strut on an auxiliary installed support, you can eliminate the bending forces between the Mauerlat and the rafter elements.

Repairing a damaged rafter system

To repair wooden rafters or mauerlat beams, additional pads are usually used. This method is used if single rafters are damaged. Such elements are fixed with nails or bolts, resting the lining with its lower part on the Mauerlat and screwing it with knitting wire.

When deciding how to strengthen the rafter system in the presence of numerous damages, rod prostheses are usually used. Moreover, all deformed and unusable wooden elements needs to be removed. First of all, the rafter is fixed with temporary supports, after which a piece of roofing is dismantled and the damaged area is removed. In its place, a similar element is attached - a “prosthesis” made from fresh wood. For reliability, he must rely on the deer.

If it is necessary to replace individual sections of the Mauerlat, the work is performed in the following sequence:

• before strengthening the roof of the house, under rafter frame temporary support pillars;
• then dismantle the damaged piece of the Mauerlat beam;
• prepare a beam of the appropriate size (about 1 meter) and place it on studs located in the masonry of the wall;
• then a piece of timber of the same size is mounted on the wall or floor beams;
• at the end of the rafters they are additionally fixed with two struts, which rest on a new beam.

The question of how to strengthen the rafters arises in cases where it is necessary to eliminate defects wooden structures that appear as a result of natural wear and tear or loss of rigidity wooden frame and damage to its individual elements. As a rule, the rafter legs are the first to undergo deformation and begin to bend. This phenomenon can occur if, during the construction of a house or garage, the installation of gable roof rafters on a log house was not carried out according to all the rules.

The junction of the rafter legs with the roof ridge beam is one of the most important. If the slightest deviations are detected, the roof rafters should be strengthened in this place as quickly as possible. Sometimes a jack is used to tighten the rafters to the purlin or to each other. After this, the joint is properly strengthened with a perforated metal strip or a wooden overlay with a thickness of 2 cm. Such an overlay is installed under the ridge.

On next stage proceed to leveling the rafters. A hydraulic cylinder is used for this. Before strengthening the rafters and leveling them, triangular wooden stops are attached to them from the inside with self-tapping screws. After installing them, you can straighten the rafter leg with a hydraulic cylinder and install a spacer, which in the future will protect the roof frame from external loads.

Before strengthening the roof of the house with extensions additional beams, you should purchase material of the required width (it should match or slightly exceed the cross-section of the rafters) and length. First, the prepared timber is attached to the rafter leg using self-tapping screws. After this, a series of holes are drilled through the timber and rafters so that these elements can be secured with studs.

The holes should be drilled with an indentation of 30-50 cm in a checkerboard pattern. Thus, an increase in the resistance of the frame to bending forces is achieved. The cross-section of holes and mounting studs must match. Threaded studs are threaded into the prepared holes, washers are put on and self-tightening nuts are tightened. They will provide high-quality fastening and operation of the roof without the need to tighten fasteners. You need to tighten the nut until the characteristic creaking sound of wood appears.