What size should the ridge beam be? Calculation of the ridge bar and the dimensions of the run. Rafters paired in two or three planks

When building a house, there are practically no such elements or connecting nodes that would not be particularly important, since the overall reliability of the structure in one or another of its areas depends on each of them. . Splicing the rafters in the ridge area is a rather difficult task that can be done in various ways. The master usually chooses the most reliable of them, applicable for a particular structure.

It should always be remembered that any mistakes made during installation work during the construction of the roof structure, from the rafter system to the roofing material, will sooner or later negatively affect the quality of the entire building. Therefore, when drawing up a project for a house, it is imperative to think over the connection of each of the nodes. And it is especially important to choose a reliable fastening of the rafter legs when forming the ridge.

A few words about the basic design of the rafter system

First of all, a few minutes of attention must be paid to the general structure of the rafter system in order to remember what its main elements are called, since in the further description of installation work they will be encountered quite often.

Mauerlat - This is a bar fixed to the load-bearing wall. It serves to fix the lower side of the rafter leg on it, and to evenly distribute the load from the entire roofing system to the walls.

Mauerlat - a reliable basis for the rafter system

This element of the rafter system must be correctly selected and fixed on the wall, since the reliability of the installation of all other bearing parts depends on this. How to install - described in detail in the corresponding publication of our portal.

Rafter legs or just rafters - they form the frame of the slope, fixed on the Mauerlat in the lower part, and on top - on the ridge run or between themselves, forming a ridge.
Ridge run fixed on a rack supported by struts. It is designed for rigid fastening of rafters.
Tightening Is a horizontal bar that additionally connects a pair of rafter legs, giving the structure additional rigidity. Tightenings are of particular importance in hanging truss systems, when it is impossible to create intermediate supports on the main walls. Ties placed between two Mauerlat beams are often used as attic floor beams. Installed closer to the ridge - they can serve as the basis for filing the ceiling of the attic.
Braces and help - These are reinforcing elements designed to give the truss of the truss system additional rigidity and strength. They are usually used in cases where a large length of rafter legs is required, more than 5 ÷ 6 meters.

Rack It is used as a support for a ridge run and is most often installed in each of the trusses if a layered rafter system is being erected, which has additional supports in the form of capital intra-house partitions.
Lezhen - This is a beam that is laid on the load-bearing partitions of the house, and is designed to fix racks or struts on it.

The importance of the correct fastening of the rafters on the ridge

An element such as a ridge is present in the design of most types of roofs. He is not in the tent, vaulted and

rafter mount

The ridge is the highest point of the roof, at which the elements that form the slopes - the rafters - are connected. Therefore, the main mission of the ridge knot is to give the entire rafter system strength and rigidity. From how correctly the fastening is made, the operation of the roof structure will become longer without the need for repairs.

The main methods of installing rafters

Installation on the load-bearing walls of the structure can be done in various ways, which you need to be aware of before choosing the type of connections for the load-bearing elements of the slopes on the ridge:

The rafters and the brace are connected in a triangle on the ground, and then they rise to the box of the house in finished form, where they are fixed on the Mauerlat laid on the walls. Installed trusses are interconnected by side slopes or a ridge run.

On the ground, two extreme triangular trusses are assembled, which will go to the end, pediment sides of the structure. Then they go up and are fixed on the Mauerlat. The upper ridge corners of two opposite trusses are connected by a stretched cord, which becomes a kind of level along which the rest, middle rafter pairs, assembled already in place, will be exposed. After that, the assembled trusses are connected by a ridge run.

All elements are individually lifted onto the floor and assembled at the place of their installation. In this case, on the end walls, in the center, vertical posts are installed that set the height of the ridge. Then the racks are connected to each other by a ridge run, on which the rafter legs are fixed.

If the rafters are connected on a run, then they do not require control with a pull-on cord. Therefore, the racks and the girder must be set very carefully, in level and plumb line, at right angles to each other.

Varieties of rafters on the ridge

As mentioned above, there are several ways to mate the rafters when forming a ridge, and different fasteners are used for this purpose.

The main options in private housing construction include three types of connections:

A cut "in half a tree", when half of its thickness is selected at the edges of the rafter beam. These selected sections are superimposed on each other and fastened with one of the suitable fasteners for this case, for example, twisted with a bolt passed through.

Overlap - the ends of the rafters are superimposed on each other and fixed to each other by a through fastening element.

Trimming the end sides of the rafters - this method of joining is performed most often. It is carried out by overlapping the rafters, then they are trimmed at the same time. This is how an even cut of two rafters is formed at the same angle in the mirror image, so they perfectly fit together.

It should be noted that there are other ways of joining, for example, "tongue-groove" or butt to the ridge girder, possibly with fastening to the girder for additional strength between the rafters of additional bars or boards.

Often one of the sides of the rafter leg, top or bottom, is fixed on movable mounts, hinged (top) or sliding (bottom). This is important to provide in cases where the roof is installed on a newly built, new house, in particular - a log cabin. This approach is due to the fact that in the first years of operation, the structure usually shrinks, and if a rigid fastening is applied, then the roofing structure can be damaged, deformed, as the "geometry" of the system will change, and the distribution of loads will be disturbed.

Read the advice of professionals, which one is better to choose, in our new article on our portal.

Elements for fastening rafters on the ridge

There are many options for fastening rafters to each other or on a ridge run - they can be rigid or hinged. To determine their choice, you need to know what they are and which rafter connections are suitable.

To fix the rafters in the ridge area, they use fasteners such as overlays made of metal or wooden plates, timber, metal corners of various configurations, staples, movable fasteners, wooden wedges, nail plates. These fasteners are secured with self-tapping screws, screws, bolts and nails. The choice of fasteners mainly depends on the chosen connection design.

Bolt fixing

Fixing the rafters on the ridge with one bolt allows them to move to one side or the other relative to the axis when the structure shrinks. If such a mount is applied in the upper part, the lower side of the rafter leg must be rigidly mounted on the Mauerlat.

In the above diagram, under the first number, the connection of the rafters by the "groove-thorn" method and fastened with a bolt is shown, allowing them a small play relative to each other when the building shrinks.

It should be especially noted that this method is suitable for light cold roofs that will not be burdened with a large load, since the rafters in the fastening unit are somewhat weakened by the cutouts for the groove-tenon connection and the through hole drilled in them.

The sixth figure of the diagram also shows the fastening of the rafters with a bolt, but in this case, they are installed with each other "overlapping", and on the run - by the cut-in method. This method of bonding gives a smaller offset range, but it is still possible within certain limits. In this version, the rafters are less weakened, since they do not have cutouts for the connection and can withstand a large one. However, it is still not recommended to use this connection technology for roofs with a large area of slopes.

If it is planned to make a rigid fastening of the rafter legs fitted in the end part with bolts in the ridge part, then two fasteners are used, installed in through holes, through two metal plates that are mounted on both sides of the connection.

If you want to make the connection of the overlapping rafters and fixed with one bolt rigid, additional fasteners are used - metal corners fixed to the ridge girder.

Fastening rafters with plates

The above diagram, numbered two and three, shows options for rigid fastening using metal plates and wooden plates. In this case, the correct arrangement of additional elements is very important. A similar method of fastening is used when the connection of the rafters is made end-to-end by trimming and fitting their edges, as well as when installing the rafters on a ridge girder.

Perforated metal plates are fixed to the rafters with nails, screws or bolts. For rigidity of the connection, the rafters can be additionally attached to the purlin using metal corners. This type of fixation is strong enough, and it can be used for the installation of roofs with a large area and load.
Wooden linings are more reliable, since they work not only as fasteners, but also as a tightening of the rafters between themselves.

If it is supposed to make a reinforced version of fastening, for a roofing covering that has a large weight, the rafters are fastened with two rows of overlays, between which the ridge girder is pinched. This method of fixing rigidly holds the rafters in the area of the ridge, but in this case, a sliding connection must be installed on the Mauerlat, which will avoid deformation of the system when the structure shrinks.

wood screws

A separate line is the fastening of the rafters on the ridge with a triangular overlay that repeats.

This method of fixing gives a high degree of rigidity of the attachment, but if the slopes have a large area, then additionally the rafter legs are connected with puffs. They are located below the ridge connection, and they are designed not only to stiffen the structure, but also to remove part of the expanding load from the rafter system from the bearing walls.

These elements can also act as a frame for ceiling sheathing if it is planned to equip a living or utility room in the attic.

The pads and braces can be fixed to the rafters with nails or self-tapping screws.

Fastening the rafters with a cut

This method of securing is shown in the diagram above with the fourth and fifth numbers. With this approach, cutouts are made on the rafters to fit the width of the ridge run. The cutouts are made 5 ÷ 7 mm wider than the purlin width, since it is necessary to provide a distance for temperature and humidity expansion. The cut can be used in combination with other fasteners, for example, "overlap", "groove-thorn", overlays and metal corners.

Hinged rafters

This method of connecting rafters is not often used in construction, although it is quite convenient in installation and allows you to balance the rafter system when the load-bearing walls shrink. In this method, you do not have to adjust the angle of the rafter legs, since it can be formed using a hinge. It is fixed between the rafters at the required distance, which will depend on the slope angle of the roof slopes. The bolt acts as a hinge, which fasten the rafters after installing them on the girder at the desired angle.

Fastening rafters with nail plates

In addition to the elements mentioned above, nail plates are used to fasten the rafters to the ridge connection.

However, they can only be used when the trusses are assembled in a lying position on the ground, and are already ready-made installed on the Mauerlat, since this type of plates is fixed on the rafter legs using a special press. This process is almost impossible to carry out by weight, in an upright position.

Using this method of fastening wooden parts, you can significantly speed up the installation process, but for this you will have to purchase or rent a special press.

screwdriver

In this way, not only the rafter legs are fastened, but also other structural elements. Nail plates help to significantly save money on screws, bolts or nails, since you will have to purchase a lot of these fasteners, given the number of connecting nodes in the rafter system.

In addition to these fasteners, metal corners and brackets of the required size are used as auxiliary ones, driven into both rafters at once on their ridge part. However, it is necessary to work with the brackets extremely carefully, since they can easily split the rafter beam.

Splicing rafters on different types of roofs

Now, having familiarized yourself with the main methods of connecting and fastening the rafter legs on the ridge, then you should consider what types of them are used for the installation of various rafter systems.

Gable roof system

Splicing rafter legs in a gable roof system can be done:

- Butt, that is, they abut against each other, and in this case, their ends are adjusted by trimming;

- With fastening on the ridge run on both sides.

If the rafters are connected end-to-end, then they are usually fixed together with overlays, which are screwed with self-tapping screws or bolts.

If the rafters are fixed on a ridge run, then they are fixed on it with metal corners, corner brackets or overlays screwed using self-tapping screws.

This diagram shows a design with two purlins:

1 - Rafter legs.

2 - Racks.

3 - Tightens (crossbars).

4 - Runs.

5 - Mauerlat.

6 - Beds.

The rafter legs of the gable rafter system can be supported by two girders fixed on racks that are installed and fixed on the racks. For the spacer effect of the structure, tightenings (crossbars) are also applied. All these elements firmly hold the rafter legs, removing the main load from the ridge, so the rafters can be overlapped or with a tongue-and-groove connection.
If the rafter system is assembled without using a girder, only by joining the butt ends of the rafter legs, then in addition they must be supplied with one or two pairs of pads, which are fixed to the rafters with nails, screws or bolts.
To fasten the rafter leg with the crossbar, when installing it end-to-end, side wooden or metal plates are used, and nail plates can also be used if the truss is assembled in advance.

If the rafter legs are made of logs, then they are fastened to the crossbar without the use of overlays. To connect at the ends of the crossbar, recesses are made to ½ of their thickness, then they are pressed against the rafters and fixed with nails or self-tapping screws. Additionally, such rafter legs are reinforced with struts. This is especially important to take into account if the distance between the load-bearing walls is more than 7000 mm.
Corner brackets are used for more reliable fixation of rafter legs on a ridge run in buildings located in regions with strong winds. The brackets will help prevent possible displacement and deformation of the elements of the rafter system.

Rafters from logs are made only with reliably reinforced, having a large thickness of load-bearing walls, since the entire rafter system from them will turn out to be quite massive. If it is planned to use this particular material for the structure, then it is recommended to make accurate calculations of the bearing capacity of the walls and the system itself in advance, and it would be best to entrust them to specialists.

Another point that must be taken into account when drawing up a roof project and during its installation is that the steeper the roof slopes, the stronger the horizontal reinforcing elements of the structure should be. And, conversely, if the roof slopes are at a slight angle, then special attention should be paid to the strength of the vertical retaining elements of the rafter system.

Hip and half hip roof

There are two similar designs - this is a half-hip rafter system. They differ in the configuration of the end slopes: if in the first two full hip slopes are equipped, from the ridge to the level of the cornice, then in the second slope ends above the level of the cornice or is crowned on top with a small triangular vertical pediment.

The fastening of the rafters in the ridge girder in both structures has its own characteristics, somewhat different from the usual gable roof. The installation of these rafter systems is complicated by additional elements that form the hips - slant legs or diagonal rafters. In addition, in addition to the usual rafter legs, which in this design are called central and intermediate, shortened ones (napkins) are installed parallel to them.

If a hip roof is chosen, then the ridge size will be less than the length of the building. According to the "classical" scheme, with equal angles of steepness of the side and hip slopes, the length of the ridge will decrease by the width of the building. The eaves side of the side slopes will be equal to the length of the wall, excluding the overhangs. Thus, the side slopes will have a trapezoidal shape, and the end hips will be triangular.

In such roofs, the installation of a ridge girder (console) differs from the standard design, since the load on it will be much higher than in a conventional rafter system with two slopes.

The support racks, on which the purlin will be fixed, should be installed on a bed, laid and fixed on a capital house partition or on powerful floor beams. The rafter leg extreme to the hip in this design is fixed on the girder, with an indent from the edge of 150 ÷ 200 mm. This distance will depend on the width of the diagonal rafters, which must be fixed to this section of the purlin end-to-end with the outer rafters of the trapezoidal part of the roof. Such a connecting knot is rather difficult to self-adjust, and the corners of the elements converging on it must be carefully calculated and adjusted by trimming.

The Mauerlat in the hip and half-hip roof structure is necessarily laid along the entire perimeter of the building box, representing a single, rigidly connected frame, since this is necessary to fix the hip elements and evenly distribute all loads on the walls.

Diagonal (oblique) rafters, forming the edges of the hip, must have cuts in the form of a step, or mounted cranial bars, along their entire length on both sides. This is necessary to simplify the fastening of the shortened rafter legs of the hip - Since the diagonal rafters are of a greater length than the central ones, and the maximum load falls on them, they are often made of two boards, fastening them together. Skull bars on diagonal rafters are fixed with nails or self-tapping screws.

Work on the installation of hip elements is carried out in the following order:

The finished diagonal rafters are installed and fixed by the cutting method on the edge of the ridge girder and to the central rafters of the gable part of the structure. The underside of the rafters is fixed exactly at the corner of the building on the Mauerlat. Fastening can be done with metal corners and angle brackets.

The next step can be the installation of two struts, which are fixed on the rack of the main rafter system with one edge, and on the inner sides of the diagonal rafters, at a level of about ⅓ of the length from the upper attachment - with the other. Fastening is carried out using metal corners or pads and self-tapping screws (nails).

Further, if there is a need for this, the diagonal slant rafters should be reinforced from below with stands-supports fixed to the sprengel. A sprengel is a beam that is installed diagonally at the corners of the Mauerlat frame, on which the rack rests, supporting the slant rafters. These elements can be held together with metal corners or brackets.

The upper edge of the racks is cut off at an angle equal to the slope of the diagonal rafters, and fixed to them with self-tapping screws. If necessary, the rack can be additionally reinforced with struts fixed on it and on the sprengel.

Then, depending on the slope of the diagonal rafters, they are marked on them and fixed by cutting them onto the cranial bars. In the lower part of the structure, the handcuffs are fixed to the Mauerlat.

Calculation and installation of a hip roof is not an easy task!

If a decision is made to build just such a roof, then you will have to work hard both on the calculations and on the preparation of the necessary structural elements. Read more about it in a special publication of our portal.

The installation of any truss system is an extremely responsible event, since the durability of the entire structure as a whole depends on the quality of its installation. Therefore, if it is decided to do this work on your own, it is recommended to invite an experienced craftsman as an assistant, who will not make gross mistakes that beginners often make.

At the end of the publication - a short video that shows the process of fitting and installing rafter legs.

Video: installing rafters on a gable roof structure

The rafter system is the foundation of your future roof, so its construction must be taken very seriously. Before you start work, you need to sketch out for yourself a rough plan of the system in order to understand what the type of general structure will be and what functions its individual elements perform.

In order to calculate the parameters and technical characteristics of the rafter system for large objects, it is best to resort to the services of professionals. If your roof is intended for a private building of a relatively small size (house area up to 100 m 2), then you can carry out the installation, guided by the materials below.

The first step is to determine the angle of inclination of the slopes. Usually, average calculations are based on the amount of materials, which has a very good effect on the material component of the issue, it is generally accepted that the smaller the angle of inclination, the more profitable and cheaper the building will cost. In fact, it is necessary to choose the angle of inclination from two main indicators - wind loads and the weight of precipitation (in particular in winter), as you can see, the question of prices in the technical parameters is not taken into account. The universal angle of inclination for our climate is 45-50 degrees, with such parameters, the strength indicators in front of loads, both wind and those that can be caused by precipitation pressure, are maximally balanced. Sometimes it happens that about 180 kg of snow falls on one square meter of the roof. In addition, the financial component will also be at an average level, which is much better than saving money by reducing the angle of inclination, but subsequently overpaying two prices for eliminating defects that will be caused by the above factors.

Choosing a tree

For the rafter, two parameters are important - strength and lightness of the structure, so ordinary pine is suitable for installation. It is often used for such structures, since it has these two qualities, plus it has a favorable price compared to noble wood species. It is necessary to use a board of the first grade, 150-200x50x6000 mm in size, we also need a bar with a section of 200x200 mm.

An important technical point is the moisture content of the wood. A freshly sawn tree has a 50% moisture coefficient, it is impossible to mount such a tree, because if it dries out in a state of tension, it can be driven, it will bend and crack in places where knots are located. It is necessary to purchase material with 15-20 percent moisture content.

When buying, check that all boards are even and free of rot, the strength and durability of the structure depends on this.

When the tree is delivered to your construction site, it must be treated with antiseptic drugs and laid in the most ventilated area. The laying of the tree must be done in a certain way: first, we lay three or four transverse slats, on them, along, we lay boards so that there is a distance of 0.5-1 cm between each board, then again a row of transverse slats and a row of boards.

Thanks to this, we will create an air space between each unit of lumber, they will be ventilated in the right conditions, which will allow us to avoid rotting and moisture accumulation.

We put a ridge bar

The ridge bar is the center top bar, which is designed to evenly transfer the total weight of the roof onto the gables, distributing the pressure area around the entire side perimeter. The installation of a bar is a very complicated process. First of all, let's decide on its length. As a rule, according to the plan, there are small canopies (from 0.5 to 1.5 m) from the sides of the roof, the ridge beam should exactly lie along this length with all the protrusions outside the gables. On concrete foundations, in places of contact with the timber, we lay pieces of roofing material so that the tree does not touch the pediment directly - only through the waterproofing. We bend the roofing material around the timber, and drill on the sides and insert two segments of the 12th reinforcement, 0.4 m each. We do not drill the timber itself in order to avoid cracks.

Elongated timber

Very rarely, a standard 6 meters is enough for a "ridge". In most cases, this length has to be increased. The build-up takes place at the place of installation, otherwise the spliced beam will be very difficult to lift up and install. The joining point of the timber must be selected in such a way that it is as close as possible to some partition or other point on which a temporary vertical support can be placed. For vertical support, we measure and cut off the board, on the sides of which we nail two small boards, so we get something like a wooden fork, between the teeth of which there will be a joint of the ridge bar. On the upper side of the ridge, we pull a thread that will serve as a level for us before we fix the beam to each other. It is necessary to fasten them with two one and a half meter segments of the board, the joining segments are located exclusively on the sides, in which case the load will be applied to the tree in the right direction, reducing the risk of fracture at the junction. The boards are fastened with nails, since if you try to organize bolted connections, the timber can give a number of cracks when drilling.

Mauerlat

This element is used for joining the rafters with the longitudinal bases of the load-bearing wall, for point distribution of the load of the entire structure. It must be laid using roofing material (as is the case with the ridge). Choose the flattest boards, they should adhere to the wall surface as much as possible. The Mauerlat is fixed with 0.2 m long anchor bolts. The points where the anchor will be placed must be calculated in advance, their location should be in the intervals between the future rafter boards, so that the anchor heads do not interfere with us when further fastening the following elements.

If the standard length of the board is not enough, feel free to pick up the boards and fasten them in the same way as the joint between the Mauerlat boards will be organized - it does not matter, the main thing is that they fit snugly to the concrete.

Do not forget to put the Mauerlat on short sections behind the gables where you have your roof peaks outlined.

The device and installation of rafters

The first step is to determine the number of rafters, for this we take the total length of the roof and divide by approximately 1.2-1.4 m, after we get an integer, we divide the length of the roof by it. An integer is the number of rafters on one side, dividing the length by this number will give us a more accurate pitch between them, for example, if the roof is 9 meters long:

9 m / 1.3 m = 6.92(round up) = 7 - the number of rafters;
9 m / 7 = 1.28 m- a step between the rafters.

We multiply the number of rafters by two and again by two, thanks to these calculations, we will get the total number of boards that will need to be used to make the structure.

The next step is to cut the boards at the angle of the roof. To do this, on one side of the board, the perpendicular between the cut and the longitudinal part must be shifted downward by the required number of degrees. With the help of a protractor and a pencil, everyone can do this procedure. Next, we cut the board along the marked line, we will get a template according to which we will trim all the other boards.

First, we mount the extreme rafters that are inside the zone between the gables. Installation of rafters is performed on two levels, the first at the ridge, the second near the Mauerlat. The marking of the step between the rafters should be done both above and below. This line is the middle of the rafters, the structure of one rafter consists of two boards, the distance between them is 50 mm.

We cut off 9 boards 30 cm long and fasten them on the ridge beam clearly according to the step markings. Fastening is carried out using self-tapping screws and corners, the board should lie on top and perpendicular to the ridge. These sections will serve as a connecting link for attaching two opposite rafters.

In a similar way, we attach 9 segments on each side to the Mauerlat, only the length of the board should be 20 cm, and it should be placed vertically, this node will be used to fasten the lower sides of the rafters.

Now you can start the basic procedures. On each upper segment (30 centimeters), it is necessary to draw a middle vertical line, it will play the role of a guide, where the joining of two boards cut at an angle takes place. Installation of rafters begins with the fact that the first board is aligned in the center from above and tacked onto a nail to a 30-centimeter segment. Then a second board is nailed on the other side. It is necessary to ensure that the boards are at the same horizontal level, for this it is necessary to undermine the board, which is planted below, and raise it to the level of the second board, fixing it on a nail to the connecting jumper. It is highly discouraged to make cuts in the ridge bar. Below, to level the level between the boards, the opposite procedure is performed, the board, which turns out to be slightly higher, is heated into the Mauerlat, for this it is necessary to hollow out a small groove using a chisel.

After the boards are adjusted to the level, it is necessary to tighten the lower part of the rafter with two nails and make two bolted connections, one at the top, the other at the bottom, in the places where the boards are baited on the nails. The bolted connection must be through three planks.

After that, we get an almost finished rafter, which must be strengthened in order to give it rigidity. We will conditionally divide the length of the rafter into four parts, you can sketch out the markings with a pencil. At the junction of the first and second quarters, we fasten a 60-centimeter segment between the boards to tighten the rafters. We use nails as fastening materials. We perform a similar procedure at the junction of the third and fourth quarters.

After the four rafters are mounted, we have two extreme triangles, at the bases and at the top it is necessary to pull the threads along the entire roof, which we will use as guides to adjust the level of all diagonally located elements.

After the side rafters, the central part is mounted, now you can knock out the support, which is located at the junction of the ridge beam, we no longer need it, at this stage the structure already has a sufficient margin of safety. Next, all the other rafters are placed, one section on each side in a checkerboard pattern, to evenly distribute the loads. Upstairs, at the joints of opposite rafters, it is necessary to additionally strengthen the connections, we use connecting plates and self-tapping screws for this.

When all the rafter sections are in their places, it is necessary to cut off with a hand hacksaw all the corners that go beyond the level of the rafters, in particular, these are the corners of the connecting boards on the timber and on the Mauerlat.

Assembling bows

The bow is a connecting board that is located approximately at the level of the centerline of the rafter triangle. It serves to reduce the load on the sides of the roof, thanks to the bows, the likelihood of roof deflection under the weight of precipitation and the likelihood of vibrations under wind loads is greatly reduced.

In our case, the height of the ridge beam is slightly more than 4 meters, which means that the arrangement of the bows can be done strictly in the center, thus, all loads are distributed evenly, plus the height of the ceiling of the attic will be relatively normal and there will be no obstacles for movement of a person with average height in it.

As in the case of the rafters, the first bows are attached to the sides, after which two threads are pulled, they will help us maintain the level. After that, the central bow and all the others are attached. On the extreme rafter triangles, bows are not needed, this will spoil the appearance of the roof, besides there are very weak loads, so from a technical point of view, this step is not required.

One side of the bow is wound in the middle of the rafters and sits on the nail, the second side, after observing the horizontal level, also benefits from the nail, then we make two bolted connections. It is very important to adhere to the level at this stage, since the bow is not only a spacer, but also the basis of the ceiling of the attic or attic room.

In fact, this technology is very simple, no matter how complicated it may seem at first glance. Armed with a sheet of paper and a pencil, draw the roof in stages, as indicated in the article, then the whole puzzle will fold into one accessible and elementary picture.

With the help of a standard set of construction tools, two people are able to build a similar roof in 5-6 working days.

Evgeny Ilyenko, rmnt.ru

If you follow the wording, then a purlin is a load-bearing beam that rests on a wall with two ends. In most cases, the ridge rests on two pediments, but sometimes this formulation does not quite correspond to reality. So, in hip roofs, the ridge does not lean on the walls. The simplest option is a beam laid on gables without the use of props. In any case, it is necessary to correctly determine the cross-section of the ridge run.

To calculate the cross-section of the ridge run, it is necessary to sum up the loads from half of the roof, or rather, from its horizontal projection. The dimensions of the purlin depend on its length and the dimensions of the building. In a large building, the run will turn out to be so powerful and heavy that you will need to use a crane for installation. However, it is very difficult to find an even solid timber longer than 6 meters, therefore, to make such a ridge, it is better to take an ordinary log or a glued beam.

In this case, the ends of the ridge element, which will rest on the wall and are actually walled up in it, must be treated with antiseptics and wrapped with tar paper or roofing felt to protect against decay. If a solid wood beam is used, then its end must be cut at an angle of 60 degrees and left open, that is, this end should not come into contact with the wall material. Such a measure is needed in order to increase the end area, which will improve the moisture exchange in the wood.

If the ridge run will pass through the entire wall, then that part of it that is in contact with the wall should also be treated with an antiseptic and wrapped in roll material. This overhang of the ridge outside the wall makes it possible to form an unloading console. If in the middle of the ridge the load from the roof tries to bend the beam downwards, then on the consoles the pressing force promotes the deflection in the opposite direction, thereby reducing the deflection of the girder in the middle part.

Important: even if the cross-section of a long solid wood girder is selected correctly, and it is suitable for its deflection strength, the beam can bend under its own weight. Therefore, instead of such a long wooden ridge, it is better to use a construction truss.

Section calculation

To select the cross-section of the ridge beam, it is necessary to carry out a calculation according to two indicators:

deflection;
and calculate the breaking strength.

First, you need to determine the internal stress that occurs in the beam when bending under the action of an external load. This value should not be more than the calculated bending resistance of the material, which can be found from the table or in SNiP number II-25-80. The internal stress is found by the formula: Σ = M: W, where:

Σ - the required value, which is determined in kg per cm²;
M - ultimate bending moment (kg X m);
W is the moment of resistance to deflection at the selected section of the rafters (found by the formula bh²: 6).

The deflection of the run must be compared with the normalized value, which is equal to L / 200. It should not exceed it. The deflection of the beam is found by the formula f = 5qL³L: 384EJ, where:

J is the moment of inertia, which is determined by the formula bh³: 12, where h and b are the dimensions of the section of the run;
E - the value of the modulus of elasticity (for coniferous wood it is equal to 100 thousand kg / cm²).

First you need to calculate the bending moment. If there are several of them on the beam diagram, then after the calculation the largest is selected. Further, to determine the dimensions of the beam section, we can arbitrarily set the beam width parameter and then determine its required height by the formula: h = √¯ (6W: b), where:

b is the value of the beam width specified by us in cm;
W is the bending resistance of the run, the value is determined by the formula: W = M / 130, where M is the largest bending moment.

You can do the opposite, set an arbitrary width of the purlin and calculate its height using the formula b = 6W: h². After you calculate the dimensions of the cross-section of the purlin, it must be checked for deflection using the formula from paragraph 2.

Attention! It is better to add a small margin of safety to the calculated value of the deflection.

When the ridge bar is designed for deflection, then it is necessary to compare this value with the value L: 200. If the deflection in the longest section does not exceed this value, then the section of the beam is left as it turned out. Otherwise, it is necessary to increase the height of the purlin or use additional supports from below. In the latter case, the resulting section must be rechecked by again performing the calculation taking into account the supports used.

The obtained values for the width and height of the ridge must be rounded up. In principle, this calculation is not difficult. The most important thing is to indicate the values in the desired units of measurement, that is, do not get confused by converting meters to centimeters and vice versa.

A special "ridge" in the skill of builders can be considered the installation of a ridge beam - an upper crossbar designed to fasten rafters in some roof models. Often, the beam itself requires the installation of additional supports, especially when the ridge part of the attic has an estimated length of more than 4.5 meters.

Nevertheless, with any design of a ridge bar, it remains important for him to solve problems:

evenly distribute the total weight of the roof to the gables;
evenly distribute the area and force of pressure along the lateral perimeter;
to give rigidity to the structure of the rafter system.

For the ridge beam, it is also important to maintain the geometry of the roof, especially with a length of more than 4.5 meters, in order to be able to mount the rafters without using a template. The rafters lie with their upper part on the ridge beam, and with the lower part on the Mauerlat.

Ridge wood

The construction of wooden houses from profiled timber provides for the use of a rafter system in accordance with the design features of the building. Taking into account the fact that the ridge beam carries a large operational load, it is made from reliable sawn timber. The weight of the ridge bar should not increase the total weight of the roof, but in terms of strength it should be such that for many years of operation it flawlessly performs the functions assigned to it. Therefore, for the ridge beam, as well as for the entire rafter system, pine lumber is selected so that the beam comes out with a cross section of at least 20x20 cm.

A ridge girder is laid at the top of the rafter structure of any roof

For the construction of an 8x8 residential building from a bar, whose roof will be covered with slate or flexible tiles, all components of the rafter system, including the ridge girder, are made of well-dried pine wood. In the construction of a bathhouse, where hot steam can damage the wooden structure, larch lumber is used for the rafters. In addition, the sauna requires a heavy roof that retains heat optimally. Light pine is not suitable here, a stronger and heavier larch is needed.

Larch for the production of a ridge girder is also used when a heavy tiled roof is planned for a residential building, under which a very strong and equally heavy rafter frame must be built. Here, calculations take into account that the walls of the house can withstand the load from the total weight of the roof.

The choice of materials used in the construction of the truss system depends on the structure of the building. Therefore, only professionals can make a qualified decision.

Ridge run in the rafter system

When the rafters require a center support, a ridge girder setup is used. It rests on two sides against parallel load-bearing walls.

The installation height of the ridge bar is determined by:

the design width of the house;
the average annual amount of winter precipitation;
the presence of strong winds.

The peculiarity of the installation of the ridge bar is to exclude its drilling and hammering of nails. This is necessary for:

preventing the formation of cracks;
preserving the integrity of the timber;
ensuring the reliability of the rafter system.

The design of a gable roof requires the installation of a ridge girder. In the future, it serves as a ridge of the roof. When building a house from a 6 by 6 bar, the ridge run is prepared from a solid bar or log, which structurally rests on two gables, without the use of additional supports. If the design length of the house exceeds 6 meters, a compound ridge girder and construction trusses are used. Regardless of the design length of the house, the length of the ridge bar is determined in such a way that it lies exactly on the ledges of the outer gables.

warm corner dovetail

The construction of wooden houses involves the use of several types of joining of beams. Modern construction is reaching a high level of environmental friendliness and reliability of housing, when even the joints between the beams in the structure of the house are practical and durable. Their task is to make the house warm.

The ridge bar is the top bar to which the roof rafters are attached. The installation of a ridge bar is considered a special skill in the work of builders: they must make a special calculation of the dimensions of the room, the attachment point, the attic.

The ridge wooden beam and the rafters attached to it are designed to perform the following tasks in the construction of housing:

Create a stable structure for the truss system.
Distribute the pressure force and area evenly along the lateral perimeters.
Distribute the correct weight of the roof onto the gables.
Maintaining roof geometry longer than 4.5 m. This allows rafters to be installed without using a template. If the dimensions of the roof are large, then a rafter (with the upper part) is placed on the ridge wooden beam, and the lower one is attached to the Mauerlat.

An important condition for installing a ridge bar is to calculate the correct cross-section of such a support, which will make it possible to make a stable structure.

Let's figure out how to calculate and fix the timber. The cross-section of the purlin is calculated very simply: all the load data are added from the horizontal projection of the roof. The dimensions of the ridge bar depend on 2 main parameters:

Beam girders.
Building dimensions.

The calculation of the parameters of the timber provides that for large buildings a powerful, heavy and rather weighty run is needed. But it should be borne in mind that such dimensions of the ridge bar will require the use of a crane. The average length of a regular beam is approximately 6 m, so to make a larger purlin, you will need to look for a tree or a so-called glued beam.

The fixed ends of the ridge, pretreated with an antiseptic, rest against the wall into which they are embedded. Additional processing is carried out with roofing felt and roofing felt, which perfectly protects the wood from decay. The solid wood beam is installed differently:

The butt end is chipped at an angle of 60 °.
The ends remain open so that the ends do not come into contact with the walls.

As a result, when building a house, 2 tasks are solved at once. First, the end area becomes larger. Secondly, moisture exchange processes are normalized.

Then they calculate the size of the ridge beam, which must be installed in the wall and go through it, you need to take into account the contact with the wall. Therefore, the end of the run must be well treated with an antiseptic and wrapped in roll material. A similar design is used to make the unloading console.

With a properly selected section for an all-wood beam, it must be borne in mind that the beam in the ridge at any time is capable of bending under its own weight. Experienced builders recommend installing a construction truss so that the fixed ridge wooden beam does not break.

Calculation of the section of the ridge bar

The calculation of the section requires taking into account the following parameters, according to which the calculation of the required size will be carried out:

deflection data;
strength to destruction.

To determine the cross-section, it is necessary to apply special formulas in which each indicator is important. A separate calculation determines such data as:

Internal stress (Σ = M: W).
Deflection of the purlin (according to the formula f = 5qL³L: 384EJ).
The dimensions of the beam section are determined by the formula h = √¯ (6W: b).

The data for each formula is indicated below:

Σ = M: W (definition of internal stress), where Σ is the quantity to be found. M is the ultimate bending moment, calculated in kg / m. W is the resistance to deflection of the set section.

The calculation of the deflection of the purlin is carried out using other data that must be substituted into the formula f = 5qL³L: 384EJ. The letter J means the moment of inertia, for which you need to know the dimensions of the cross-section of the purlin (height and width, denoted by the letters h and b). Then the exponent h must be cubed and multiplied by b. The resulting value is divided by 12. The parameter E is the elasticity of the modulus, which is taken into account and is individual for each type of wood.

The bending moment must be calculated by the formula h = √¯ (6W: b), where b is the beam width in centimeters, W is the bending resistance of the run. You can get W by dividing M (largest bending moment) by 130.

The values of the width and height, which are obtained after the calculation, must be rounded up. If the builder is afraid to make a mistake, you need to contact the specialists who will calculate the parameters, determine what the fixed beam and the run should be.

Installation of a ridge bar

Let's consider how to attach the ridge bars. They are made only from high-quality sawn timber, which is due to the importance of the structure, which must fulfill the functions of long-term and reliable operation, bear the load, and be safe for the residents of the building. It is important that the girder does not increase the weight of the roof, otherwise the strength of the structure will be in question. Rafters should serve for a long time, performing their assigned functions. For this purpose, pine lumber is often used for the ridge beam, the cross-section of which is 20x20 cm.

Fastening the rafters to the ridge beam is selected depending on the type of building: residential or utility purpose. Depending on this, the material of the ridge, its section and dimensions will be selected. For example, well-dried larch is usually used for a bath, which is heavier and more durable to stress. Also, larch copes well with steam, retains heat and keeps tiles. Residential buildings are built from pine, since the roof is usually covered with so-called flexible tiles.

Larch for the manufacture of timber is used if the house will be covered with heavy tiles, which require a strong and strong building frame structure. It is important that the rafters not only support the roof itself, but also do not become overweight for the walls. They should perfectly hold the girders, not bend under them.

In order to make the rafters a central support, you need to install a bar. Its ends will abut against parallel bearing walls. Correct installation of such a structure requires the calculation of data such as:

The average annual rainfall that falls in a particular area.
Whether there are strong winds in the region or not.
The design width of the house.

The ridge beam allows you to avoid such processes in the construction of a house as hammering nails, drilling with a drill. As a result, it is possible to avoid the formation of cracks, maintain the integrity of the timber and ensure the reliability of the entire rafter system.

A gable roof also requires the use of a ridge girder, which subsequently acts as a ridge of the roof. In order to build a 6x6 m residential building, it is recommended to take a run made of a log or a solid bar. The run will rest on 2 gables, and no supports are needed. If the length of the house is more than 6 m, then it is allowed to use construction trusses and a compound ridge girder. It is important that the timber rests on the outer gables.

Fastening of the ridge bar is carried out in different ways, which allows you to connect the bars in the right way. The main goal of each joint is to make the structure strong and reliable. Modern technologies make it possible to connect the beams to each other so as not to use any additional materials for insulation. If the project documentation is drawn up correctly, then the house will turn out not only to be strong, able to hold the roof, but also become environmentally friendly and reliable for housing.