If you are just going to build your house and are looking for an unusual and energy-efficient project, then it's time for you to think about a pitched roof, which is also called asymmetric or asymmetrical. This differs from a conventional roof in that its two slopes have different lengths or slopes.
Most often, a gable roof with different slopes is implemented when it is necessary to create a single complex from a house and an extension, although recently the classical canons of roof construction have begun to be forgotten about ordinary architectural tasks. Want to know why? It is interesting!
The American architect Frank Lloyd once said: "Great architecture is a testament to the greatness of mankind." Indeed, the evolution of the roof from ancient times to the present time is amazing. What architects of different times did not do with the roof of a residential building!
And what kind of forms they did not create. Although the architecture of the last century is especially surprising with its diversity, where in the pursuit of uniqueness, originality and madness of ideas, simple residential buildings in projects and implementation turned into real space objects.
Sometimes the designer's violent imagination did not have a single more or less recognizable architectural element - there is no roof, no walls in their classical sense too ... And at the turn of the century, the fashion for such structures sharply declined - rather due to the irrationality of the design decisions themselves.
But humanity has gained a lot from this: for example, with a light heart, it moved away from the unchanging classics of roof construction, taking note of new rational ideas. As a result, they began to build really beautiful, albeit unusual, roofs of private houses. For example:
- placing one slope to the south;
- the second at a different angle, or longer, to the north;
- correctly calculating all the loads from wind and snow;
- wisely organizing the interior of the house,
Such a builder achieves much more efficiency from his creation than if he had built an ordinary two-story house under a gable roof. Those. all the minuses were reclassified into pluses, and the originality remained at its best:
As modern architects have calculated, having just one corner above 45 degrees significantly reduces the unused floor space of the home. And it costs a lot.
Surprisingly, the asymmetrical roof isn't all that new. Even the ancient builders did not have in their arsenal modern computer programs and precise measuring instruments, as well as sufficient knowledge of stereometry. Therefore, they did not think too long about how perfectly flat the roof should still be.
They used a long slingshot as the main measuring tool, and tied a cord and a plumb line to its ends. The slingshot was raised so that the plumb line pointed exactly to the middle of the end wall of the building. Then the ends of the cord were stretched to the corners of the house. If necessary, the slingshot was raised higher or, conversely, lowered lower. Once the overhang was chosen, a special board was nailed to the wall of the house. A cord was attached to these bundles. So it turned out a clear visual border of the future roof slopes.
Difficulties arose just with the second roof slope. The fact is that it was difficult to place the second plank at the same height as the first one because houses in Russia were built from round wood for a long time. It is almost impossible to distribute such walls in one plane to the horizon. Therefore, transferring the size of one board to a second case was hopeless.
For more accurate measurements, a water level was already needed. Only with the help of this tool the horizon of the future roof turns out to be relatively even, and the ridge is placed in the center. But in most cases, especially when construction took place in remote rural areas, local residents were not spoiled with such tools, and therefore almost everything was done by eye. And yes, the roof slopes were often really different.
What is even more interesting, a truly asymmetrical pitched roof was found in Ancient Russia as a separate specific type of architecture. Most of these could be seen in wooden chambers and palaces that belonged to wealthy people. Then it was with the help of architecture that the significance of the wealth of the owners of such buildings was conveyed:
Therefore, local architects of this time were looking for all the ways to make the same tower different from a simple hut. It was already decided here to cover each log house with a separate roof, even if the buildings were built by a friend from a friend.
Each ramp was guided and wrapped in a different way, with a variety of possible endings. Moreover, the log cabins themselves were built of different heights, from which the roofs were often noticeably sloped.
But note that the often encountered pitched roof, in which the slopes do not converge in one ridge from above, cannot be called gable. These are rather two separate single-pitched roofs, which are built separately and each according to its own rules.
Advantages and disadvantages of pitched roofs
What is so good about an asymmetrical roof that for the sake of its benefits many are willing to risk both the strength of the house and the durability of the roof over their own heads? Let's list them.
Uniqueness and design
The asymmetrical roof always looks stylish in any location. In our country, after so many centuries of unchanged construction of gable gable skates, any such projects are already striking, cause surprise and leave an indelible impression.
Moreover, if you want to create an absolutely unique architecture at home, then it is easiest to realize your crazy idea just with the help of such a solution as different slopes.
Advantageous architecture
Note that working with an asymmetrical gable roof is more enjoyable and interesting for any architect. After all, now he does not need to first draw the outlines of the house - a typical rectangle, and only then can he contain everything that he and his customer had planned. Now there are no frames: first, you design the interior space of the house, make it the way you want, and such a form as your fantasy suggested to you.
Now you place a garage, a veranda, and any gazebo near the house, and you will not need to worry about building all this on more than one foundation and attaching different roofs. Now that your project is ready on paper, you simply draw the roof from above so that it covers everything.
And many more valuable pluses:
Most often, an asymmetric roof is built when the second floor of the house is planned to be incomplete. For example, the area of the first floor is 120 square meters, and the second - only 60. In this case, the roof covers only two or three rooms of the upper floor, and the rest of the space remains open.
Why is such a construction good, and why is such a project attractive? First of all, the fact that there is already much less pressure on the foundation of such a house than on a full-fledged two-story building. And at the same time, the foundation itself no longer needs to be built too wide, designed for extra square meters.
Often, an asymmetrical roof is also used to install any necessary equipment, for example, solar panels.
Resistance to the elements
The pitched roof is good in that with the help of such a structure, problems with strong winds and snowfalls are solved. The fact is that if in a certain area almost the same direction of winds prevails, then it makes sense to build a pitched roof so that it has a gentler slope on the windy side, and steeper on the quieter side.
This approach solves the problem with the distribution of the load from wind and snow at once, while it is usually difficult to decide whether to make the roof pointed, thus getting rid of tons of snowflakes, or shallow so that it does not break off in the first storm.
Real “salvation” for the attic
The fact is that a typical attic under an ordinary gable roof is the most losing one and looks unpleasant, even psychologically pressing. It's all about the geometry of the interior: an incomprehensible dark space under the very ridge completely deprives the impression of the attic as a living space, and the sharp slope of the slopes and sharp corners certainly do not give comfort.
Of course, modern designers are enterprising and cunning, and have already learned how to use all these shortcomings for the good, arranging wardrobes, and organizing such a space as something profitable and stylish. If you look at such a ready-made interior design for such an attic, the so-called "wow-effect" immediately arises and it seems that living in such an attic is a sheer pleasure.
But in fact, all this is mostly beautiful - only in a glossy picture, but in life such an attic, as it turns out, has too little usable area. Therefore, a gable roof with different slopes is a much more optimal solution. Especially the roof, which has an offset ridge.
In this case, the geometry of the attic is no longer so unusual, and one of the walls may well even be vertical, if you lose without regret some half a meter of sharp space under this slope:
Some architects even recommend building asymmetric roofs for attic houses, namely, gable roofs with different slopes. So that the cornice was carried forward and was a separate expressive architectural device. But, note, a gable roof with different slopes in 90% of cases is actually built without an attic.
To make or not to make such a roof?
Basically, you have two aspects on the scales:
- First bowl: uniqueness, design and some functional benefits.
- On the second side: the complexity of the execution of such projects.
Therefore, decide for yourself what is more important to you: uniqueness or simplicity, and are you ready for many long hours to make a detailed drawing, calculate every little thing and risk, in fact, a whole building if you do not have enough experience. But in order to be proud of yourself and have extra comfortable space in the house. Let's just say: in this regard, modern developers are becoming bolder and bolder!
Types of pitched roof structures
Note that the classic gable roof is the simplest design solution. Let's highlight the main types of pitched roofs:
- Asymmetrical. In this roof, the slopes are connected in the ridge and are located at the same angle of inclination. But at the same time, one slope can be much longer than the other, due to which such a roof is perceived as original and unusual. And sometimes the difference between the slopes is not great, and in such a roof, even at first glance, asymmetry is not visible.
- Partially broken. Such a roof differs from the classic gable roof only in that one of its slopes has a break - to cover an extension, for example. But, in spite of the similarity of the design with the usual one, the calculation of the loads is done differently.
- Asymmetrical roof. This is the most original and unusual roof, it is such a roof that is built when they want the room on the second floor or in the attic to be spacious, more familiar and not have dark sharp corners. In this case, one slope has a different angle of inclination and length. There are many advantages to this design, believe me.
- Asymmetrical center offset. This roof has almost the same construction as the standard one, but its ridge is now located in the center with some offset. The length of the slope and the angles of inclination of such a roof, of course, will already be different. As a result, this design is most surprising, but at the same time it has the most valuable advantages in terms of attic space, which does not have to be modest or uncomfortable.
For example, modern houses of the "Solomon" project differ, first of all, in that they have a gable roof with different slopes. And the very design of residential buildings of the "Solomon" type is good because here you can make your own changes, refine the design and architecture of the house.
Review of the most successful projects and examples of construction
As you may have guessed, if you build a gable roof with different slopes, the architect does not have a lot of choice: the same slopes, but different angles, slopes different in length, but at the same angle, their variations and a variant with an offset ridge. And each of these projects has its own advantages and disadvantages, which we will discuss separately.
Different angle of inclination, but equal length of slopes
In this example, the ramps are the same length, but at different angles: one higher, the other lower. This was conceived in order to place a spacious terrace on one side of the house, and a small utility block on the other. If the entire roof was as flat as one of its slopes, then the owners of the house would have problems with the accumulation of snow. But the utility block usually does not require a high ceiling.
Note that this option is the most gentle for designing a pitched roof and it almost does not exert different pressure on the foundation. And here's how to build a gable roof with different slope angles of the same slopes along the length:
The only disadvantage of this option is design. Believe me, it is much easier to calculate the slopes that are at the same angle of inclination, and much easier to attach them to the ridge.
Different lengths of slopes, but one angle of inclination
In this embodiment, one of the slopes is slightly or significantly longer than the other. As in this example:
Here one of the slopes is much longer than the other, thanks to which the roof covered not only the house, but an attached veranda next to it. And at the same time, the long slope itself rests not only on the house, but also on the extension, due to which the balance in the load from the roof is maintained.
Here is another good example of the construction of such a roof, however, the longer slope here no longer covers the extension, but part of the house itself:
Another project:
But in this project, the roof of the house on one side has the same slopes, and on the other, they are different:
Slopes of different shapes and lengths
But this option is more rational in terms of even distribution of the load on the walls of the house, because thanks to the break, there is no longer one expanding force of the rafter system:
Please note that under refraction such a roof has additional supports. And keep in mind that any kinks are always the most problematic places in the roof.
The most unusual gable roofs
Such projects of pitched roofs no longer belong to those listed above due to their non-standard nature. But these are also rare:
In this project, the whole point was to make a stylish and unusual room on the second floor instead of a typical corner attic. An interesting idea, won't you agree? Such cut floors exert half the pressure on the foundation, and therefore much less money must be spent on its construction (as well as on heating the whole house). And the foundation, as you know, costs at least 30% of the cost of building the whole house in the estimate.
And one more project as an example, with a broken one ramp:
Gable roof with offset in the center of the ridge
It's already more difficult to figure out the skate, but everything is doable:
But it is especially necessary to design the load from the displaced ridge on the building from a bar. After all, the walls sag quite strongly in the first year, up to 15%, and therefore it is important not to allow the entire roof to be skewed later:
How to build a gable roof with different slopes
So, as you already understood, a roof with different slopes is quite complex in its structure. Why is that? The fact is that with such a roof, the ridge is rarely in the center and, as a result, the slopes do not transfer the load evenly. That is why the architect, when working with such projects, has to carefully calculate the rafter system, and according to completely different formulas than usual.
So, for example, the central load will no longer come from the ridge itself, and therefore the subcortex will have to be placed a little to the side. But, at its core, the asymmetrical gable roof still consists of two triangles - only not the same this time.
But this roof geometry also has your formula. Therefore, if you want to change something in one of the triangles, changes will occur in the entire asymmetrical roof. Keep in mind that when building such architectural delights, you will not be able to try everything on by eye. And even more so, then you will not make any changes.
So how can you independently calculate and build an asymmetric gable roof? You will be helped by modern computer programs that are able to calculate the required rafter pressure on the Mauerlats and the exact location of the required central support. It will be difficult to calculate all this on your own, although it is possible.
So, if we are talking about a symmetrical roof, which simply has different lengths of slopes, then keep in mind that the slope that is longer exerts more pressure on the entire rafter system and on the wall of the building. Due to the fact that it took more building material and more roofing. Usually, for strong walls of the house, this does not play a special role, but if you are building a frame structure or walls from blocks, create an additional support for such a slope, for example, almost at the very eaves.
Just remember that roofs with different slopes are calculated using different formulas. In fact, here you will need to make two whole calculations of two pitched roofs, which are simply connected together with one ridge.
Distribution of loads on ramps
What we have listed is not the only option for the construction of pitched gable roofs. In fact, today architects no longer adhere to strict rules about such design and more give free rein to imagination. For which they are valued as specialists.
Our main task is to ensure that your home is reliably sheltered from precipitation and cold. And all this is achieved with the help of a well-thought-out design, and it does not have to be standard at all, like a hut or a teremok. Despite the fact that the pitched roof is a little far from the design of the classic gable roof, its rafter system must also be carefully calculated.
Particular attention should be paid to loads and their correct distribution on the walls of the building. After all, the most important mistake in private construction, when the roof is designed is unusual, and even its ability to withstand wind and snow is calculated correctly by home craftsmen, but the roofing is not included in the load.
What is the threat? There are still not so many completed projects with pitched roofs in our country, and therefore it is difficult to track what exactly happens to such houses in 20-30 years. There is simply no such experience yet. But we can assure you that in world practice there have already been cases when the load from the roof was calculated incorrectly, and as a result, the building simply collapsed over time, not to mention serious distortions. We don't want that, do we?
And this is work with drawings and computer calculations. After all, it is important to make sure that the new roof perfectly withstands any loads and is stable both during heavy snowfall and during winds.
If your architect is against
Note that today some architects are categorically opposed to the construction of a gable roof with different slopes. This is due to the fact that for more than one century, a gable roof in Russia was almost the only form. Today, for many professionals in their field, what concerns the roof, symmetry is the defining element.
In the roof, they want to see unambiguous shapes and clear lines that unite at the top. Note that such a smart classic gable roof is also perceived as more comfortable and more familiar, which is why the customers themselves often refuse non-traditional projects.
But for the more advanced architects of our time, modern roofs are, first of all, new technical solutions. They are designed to improve such indicators of private construction as reliability, durability and functionality. Therefore, today the priority in terms of roof construction is not tradition and ideal geometry, but saving building materials, originality, which is now so lacking, and the most efficient distribution of useful living space.
At the heart of each roof is a large number of beams, rafters, uprights and purlins, which are collectively referred to as the rafter system. Over the centuries-old history of species and methods of its organization, a lot has accumulated, and each has its own characteristics in the construction of nodes and cuts. We'll talk in more detail about what the rafter system of a gable roof can be and how the rafters and other elements of the system should be attached.
The structure of the gable roof truss system
In section, the gable roof is a triangle. It consists of two rectangular inclined planes. These two planes are connected at the highest point into a single system by a ridge bar (run).
Now about the components of the system and their purpose:
- Mauerlat - a beam that connects the roof and walls of the building, serves as a support for the rafter legs and other elements of the system.
- Rafter legs - they form the inclined planes of the roof and are the support for the lathing under the roofing material.
- Ridge girder (bead or ridge) - unites two roof planes.
- Tightening is a transverse piece that connects opposing rafter legs. Serves to increase the rigidity of the structure and compensate for bursting loads.
- Beds are bars located along the Mauerlat. Redistribute the load from the roof.
- Side Girders - Supports the rafter legs.
- Racks - transfer the load from the girders to the benches.
Filly may still be present in the system. These are boards that lengthen the rafter legs to form an overhang. The fact is that to protect the walls and foundations of the house from precipitation, it is desirable that the roof ends as far as possible from the walls. To do this, you can take long rafter legs. But the standard length of lumber of 6 meters is often not enough for this. Ordering a non-standard is very expensive. Therefore, the rafters are simply grown, and the boards with which they do it are called "filly".
There are quite a few constructions of truss systems. First of all, they are divided into two groups - with layered and hanging rafters.
With hanging rafters
These are systems in which the rafter legs rest only on the outer walls without intermediate supports (load-bearing walls). For gable roofs, the maximum span is 9 meters. When installing a vertical support and a system of struts, it can be increased up to 14 meters.
The hanging type of gable roof rafter system is good because in most cases there is no need to install a Mauerlat, and this makes the installation of rafter legs easier: you do not need to make cuts, it is enough to mow the boards. To connect the walls and rafters, a lining is used - a wide board, which is attached to studs, nails, bolts, and crossbars. With such a structure, most of the bursting loads are compensated, the impact on the walls is directed vertically downward.
Types of rafter systems with hanging rafters for different spans between load-bearing walls
Gable roof rafter system for small houses
There is a cheap version of the rafter system when it is a triangle (photo below). Such a structure is possible if the distance between the outer walls is no more than 6 meters. For such a rafter system, you can not do the calculation by the angle of inclination: the ridge must be raised above the puff to a height of at least 1/6 of the span length.
But with this construction, the rafters experience significant bending loads. To compensate for them, either rafters of a larger section are taken or the cut of the ridge part is made so as to partially neutralize them. To give greater rigidity in the upper part, wooden or metal strips are nailed on both sides, which securely fasten the top of the triangle (also see not the picture).
The photo also shows how to extend the rafter legs to create a roof overhang. A cut is made, which should go beyond the line drawn up from the inner wall. This is necessary in order to displace the notch and reduce the likelihood of the rafter breaking.
Ridge knot and fastening of rafter legs to the backing board with a simple system version
For mansard roofs
The option with the installation of the crossbar is used for. In this case, it is the basis for filing the ceiling of the room below. For reliable operation of this type of system, the crossbar cut must be non-hinged (rigid). The best option is semi-rotten (see the picture below). Otherwise, the roof will become unstable to loads.
Please note that a Mauerlat is present in this scheme, and the rafter legs should extend beyond the walls to increase the stability of the structure. To fix them and dock with the Mauerlat, a cut is made in the form of a triangle. In this case, with an uneven load on the slopes, the roof will be more stable.
With such a scheme, almost all the load falls on the rafters, therefore they must be taken of a larger section. Sometimes the raised tie is reinforced with a suspension bracket. This is to prevent it from bending if it supports the ceiling sheathing materials. If the tightening is short, it can be secured in the center on both sides with boards nailed to the nails. With a significant load and length, there may be several such belayings. In this case, too, planks and nails are enough.
For large houses
With a significant distance between the two outer walls, a headstock and struts are installed. This design has high rigidity, since the loads are compensated.
With such a long span (up to 14 meters), it is difficult and expensive to make an integral tightening, therefore it is made of two beams. It is connected with a straight or oblique cut (figure below).
For a secure fit, the joint is reinforced with a bolted steel plate. Its dimensions should be larger than the dimensions of the cut - the extreme bolts are screwed into solid wood at a distance of at least 5 cm from the edge of the cut.
In order for the circuit to work normally, it is necessary to make the braces correctly. They transmit and distribute part of the load from the rafter legs to the tightening and ensure the rigidity of the structure. Metal pads are used to reinforce the connections.
When assembling a gable roof with hanging rafters, the section of lumber is always larger than in systems with layered rafters: there are fewer load transfer points, therefore, each element has a large load.
With layered rafters
In gable roofs with layered rafters, their ends rest on the walls, and in the middle part they rest on load-bearing walls or columns. Some schemes burst the walls, some don't. In any case, the presence of a Mauerlat is required.
Spreader-free schemes and cutting units
Houses made of logs or beams do not respond well to spacer loads. For them, they are critical: the wall can fall apart. For wooden houses, the rafter system of a gable roof must be non-thrustable. Let's talk about the types of such systems in more detail.
The simplest spreader-free diagram of the rafter system is shown in the photo below. In it, the rafter leg rests on the Mauerlat. In this version, it works for bending without bursting the wall.
Pay attention to the options for attaching the rafter legs to the Mauerlat. In the first, the support area is usually beveled, while its length is no more than the cross-section of the beam. The depth of the cut is no more than 0.25 of its height.
The top of the rafter legs is laid on the ridge beam, without fastening it to the opposite rafter. The structure turns out to be two pitched roofs, which in the upper part adjoin (but do not connect) one to the other.
It is much easier to assemble the version with rafter legs fastened in the ridge part. They almost never give space to the walls.
For this scheme to work, the rafter legs at the bottom are attached using a movable joint. To secure the rafter leg to the Mauerlat, one nail is hammered from above or a flexible steel plate is placed from below. See the photo for the options for attaching the rafter legs to the ridge girder.
If the roofing material is planned to be used heavy, it is necessary to increase the bearing capacity. This is achieved by increasing the cross-section of the elements of the rafter system and strengthening the ridge assembly. It is shown in the photo below.
Reinforcement of the ridge knot for heavy roofing material or with significant snow loads
All of the above gable roof schemes are stable in the presence of uniform loads. But in practice, this practically does not happen. There are two ways to prevent the roof from sliding towards a higher load: by installing a scrum at a height of about 2 meters or with struts.
Variants of rafter systems with scrapes
Installation of scrapes increases the reliability of the structure. In order for it to work normally, in the places where it intersects with the drains, you need to fasten it to them with nails. The cross-section of the timber for the fight is used the same as for the rafters.
Attached to the rafter legs with bots or nails. Can be installed on one or two sides. See the figure below for attaching the scrum to the rafters and ridge girder.
In order for the system to be rigid and not "crawl" even under emergency loads, it is sufficient in this version to provide a rigid fastening of the ridge bar. In the absence of the possibility of its displacement horizontally, the roof will withstand even significant loads.
Systems of layered rafters with struts
In these options, for greater rigidity, rafter legs are added, which are also called struts. They are installed at an angle of 45 ° to the horizon. Their installation allows you to increase the length of the span (up to 14 meters) or reduce the cross-section of the beams (rafters).
The brace is simply placed at the required angle to the beams and nailed from the sides and bottom. An important requirement: the brace must be cut accurately and fit tightly to the uprights and rafter leg, excluding the possibility of its deflection.
Systems with rafter legs. Above the spacer system, from the bottom - non-spacer. The nodes of the correct felling for each are located next to each other. Below - possible schemes for attaching the strut
But not all houses have the middle load-bearing wall in the middle. In this case, it is possible to install struts with an angle of inclination relative to the horizon of 45-53 °.
Strut systems are necessary if significant uneven shrinkage of the foundation or walls is possible. Walls can sit in different ways on wooden houses, and foundations on layered or heaving soils. In all these cases, consider the device of this type of rafter system.
System for houses with two internal load-bearing walls
If the house has two load-bearing walls, install two truss beams, which are located above each of the walls. Benches are laid on the intermediate bearing walls, the load from the rafter beams is transferred to the benches through the racks.
In these systems, the ridge girder is not installed: it provides thrust forces. The rafters in the upper part are connected to one another (they are cut and docked without gaps), the joints are reinforced with steel or wooden lining, which are nailed.
In the upper non-thrust system, the tightening force is neutralized by the tightening. Please note that the tightening is placed under the purlin. Then it works efficiently (top diagram in the figure). Stability can be provided by uprights, or jointing - beams installed obliquely. In the spacer system (in the picture it is at the bottom), the cross member is the crossbar. It is installed over the purlin.
There is a variant of the system with racks, but without the rafter beams. Then a stand is nailed to each rafter leg, which rests on the intermediate load-bearing wall with the second end.
Fastening the rack and tightening in the rafter system without a rafter girder
For fastening the uprights, 150 mm nails and 12 mm bolts are used. Dimensions and distances in the figure are in millimeters.
21.02.2017 1 Comment
The rafter system of a gable roof is a simple design, available for a do-it-yourself device even for a novice developer. You just need to make preliminary calculations, familiarize yourself with the details and stages of roofing, calculate the materials needed for installation. When calculating, it should be borne in mind that the bearing capacity of a gable roof depends on the effect on it of loads from wind, snow, and the weight of materials.
In order for the process of building a gable roof rafter system to be given to you as easily as possible, below are detailed step-by-step instructions for installing the rafter system with your own hands.
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Requirements for building materials
For the device of the rafter system, the best option would be to use sawn timber from coniferous wood - pine, spruce or larch, I - III grade.
The material for the rafters is taken at least grade II, the Mauerlat is made from boards or timber of the II grade, for the racks and girders, the material is taken from the II grade, the lathing is made of lumber of the II-III grade, it depends on the roof. Crossbars, tightenings are made of Grade I material. On linings, linings, you can use grade III material.
Note! The lumber must be dry with a moisture content of no more than 20%. Before installation, it should be treated with fire retardants and antiseptics against fungal diseases.
You need to store lumber under a canopy, providing protection from the sun and moisture. Level the storage area, shift the lumber with spacers for ventilation.
For installation, you will need fasteners: ties, plates, pins, bolts with washers and nuts, self-tapping screws with EPDM gaskets, 2.8 mm thick, mounting tape, galvanized brackets.
Brackets are used when attaching the Mauerlat, fasten them with nails or self-tapping screws.
KR corners are used to attach the rafters to the Mauerlat, prevent the rafters from moving.
All fasteners must be made of high quality material and protected against corrosion.
Tools for the construction of the rafter system
To install the gable roof rafter system, you will need the following set of tools:
- tape measures of various lengths 5, 10, 20 meters;
- markers, pencils;
- cord for stretching;
- hammers, various purposes, nail puller;
- scissors for cutting;
- roofing knife;
- putty knife;
- Scotch;
- hacksaws, electric saw, electric drill with various drills and attachments;
- screwdriver with nozzles;
- markings, horizontal and vertical levels;
- slats, rulers;
- mounting foam;
- safety strap and rope - for safe work.
All tools on the roof should be kept in a tool bag for safety reasons.
Types of rafter systems for a gable roof
Sent rafters
They are supported by a Mauerlat and racks installed on the inner wall, with an equal pitch to the rafters. To give rigidity with spans of 6 m, braces are additionally installed.
Diagram of layered rafters of a gable roof
Hanging rafters
If the building is small in width, you can arrange a rafter system when the rafters rest on the Mauerlat or walls, without intermediate supports. The maximum span is 9 meters. Sometimes such roofs can be arranged without a Mauerlat. The rafters are installed on the wall, using spacers, on the rafters in this version, a bending moment acts.
To unload, wooden or metal plates are placed. They securely reinforce the corner. For hanging rafters of a larger span, a headstock and struts are installed. For hanging systems, the rafters are arranged with a larger section, and the lumber is chosen at least I II grade.
Diagram of hanging rafters of a gable roof
Calculation of the rafter system
You can determine the cross-section of a gable roof beam required in the rafter system by collecting all the loads acting on it: the weight of the coating, lathing, snow, wind pressure, precipitation.
Constant loads can be determined by the weight of 1 m 2 of roofing, lathing. It is important that the weight per 1 m 2 of the roof is in the range of 40-45 kg.
Variable loads from snow, wind are calculated according to the tabular values of the SNiP normative documents, depending on the height of the building, the temperature zone. The load from the snow is equal to its weight multiplied by a factor depending on the slope of the slope. All these calculations are carried out in the project.
And if there is no project, and the roof is being erected on a small building? You need to look at the construction of a house in the neighborhood, which is being carried out according to a project, the roof area is the same as your building. The gable roof rafter system will serve as a model.
Sizes of timber for rafters
At the top point, a ridge is laid, which connects the rafters. The height of the ridge depends on the slope of the roof. The slope is influenced by the choice of coating material. The minimum dimensions are:
- for tile roofs, slate 22 gr .;
- for metal tiles - 14 g.;
- ondulin - 6 gr.;
- corrugated board - 12 gr.
The optimal angle is 35-45 degrees. slope, provides a quick discharge of water and snow. In regions with strong winds, the roofs are made flat and then the angle of inclination is within 20-45 degrees.
You can determine the height by the formula: H = 1 / 2Lpr * tgA. Where A is the angle of inclination, L is the width of the building.
The task is simplified when using a ready-made table. The coefficient depends on the width of the building and the angle of inclination. Factor multiplied by 1⁄2 the width of the building.
The rafters are made from pine or spruce bars, with a section of 50 × 100 mm, 50 * 150 mm.
The size of the rafters depends on the pitch. The step of the rafters is smaller, a larger number is installed, the section will decrease. The distance between the rafters at a gable roof is in the range from 600 mm to 1800 mm, it all depends on the structure of the roof and the materials used for its construction.
|
Length rafters, mm |
Distance between rafters, mm | The size of the cross-section of the rafter beam, mm |
| up to 3000 | 1200 | 80 × 100 |
| up to 3000 | 1800 | 90 × 100 |
| up to 4000 | 1000 | 80 × 160 |
| up to 4000 | 1400 | 80 × 180 |
| up to 4000 | 1800 | 90 × 180 |
| up to 6000 | 1000 | 80 × 200 |
| up to 6000 | 1400 | 100 × 200 |
The roof does not end at the level of the walls, it is extended outward by 500 mm. The rafter leg can protrude, or a board or block is built up. In this case, moisture does not get on the wall, the foundation is not poured.
Step-by-step installation of the gable roof truss system
The rafter system of a gable roof consists of the following elements:
- Mauerlat.
- Beds.
- Racks.
- Rafters.
- Braces.
- Puffs.
- Lathing.
Mauerlat installation
Mauerlat fasteners to a monolithic reinforced concrete belt
Mauerlat evenly distributes the load on the walls of the building, its installation can be done in several ways:
- to be attached to the wall through a reinforced concrete belt with studs;
- studs are inserted into the masonry;
- a simple and common method for simple roofs, wire rod fastening.
For him, take a bar with a section of 100 × 100 mm, 150 × 150 mm or 200 × 200 mm. Which section to choose depends on the size of the roof and its coverage. The Mauerlat is joined along the length, for this, make a wash down of 100 mm, 500 mm long, fold the bars and fasten with pins.
In the corners, the Mauerlat is tied with cuts into the floor of the timber, fastened with staples or bolts. At wooden buildings, this is the Mauerlat, the last crown. On brick walls, make a monolithic reinforced concrete belt with a section of 400 × 300 mm. Along the waist, place pins with a thread of 12 mm in diameter, every 120 mm, for fastening.
Drill holes with a diameter of 12 mm in the Mauerlat, lay them so that the pins go into the holes. Tighten with nuts from above. First, we put two layers of roofing felt or roofing felt under the block. On the outside of the wall, lay the Mauerlat with a brick. Lay the Mauerlat on a horizontal and vertical base. It is necessary to check the level of the horizontal surface. Check the diagonals. Align with shims if necessary.
Installation instructions for beds, racks, rafters, struts and puffs
The device of the rafter system of a gable roof with your own hands is performed in the following order:
- Install the bed, with the rafters sent.
- Mark the step of installing the rafter legs.
- Prepare to fit the rack.
- Install them, if necessary, unfasten with spacers.
- Lay the purlin. Check geometry. Install the hardware.
- Try on the first rafter leg, mark the trim points.
- Make a marking of the points and install the rafters at the beginning and end of the roof, pull a cord between them in order to align the rest of the elements along it.
- Having installed the rafter leg, we first attach it to the Mauerlat, then to the ridge run, to each other.
- Wire every other leg to the Mauerlat.
Fastening the rafters to the Mauerlat is done using cuttings, persistent corners and a hemming support bar. Reinforce with nails or staples.
Methods for attaching the rafters to the Mauerlat
Place the support legs on the beds or pads and strips. Lezhen is a beam of 50 × 100 mm or 50 × 150 mm, laid on the middle wall along a roofing felt gasket. Lay brick columns under the lining, 2 bricks high.
The rafter legs are connected to each other on a skate. Consider the common joints of the rafter system:
- They make cuts at one leg and washed down at the other. Insert one leg into the cut with the other and fasten it with a bolt.
- Install lining, wood or metal.
- With the help of cuttings in the girder, they are fixed with nails or bolts.
Methods for connecting rafters on a ridge
For the stability of the roof to wind loads, puffs, struts and girders are installed. Tightening is a bar of 100 × 150 mm, purlins and struts are made of a bar of 50 × 150 mm or 100 × 150 mm.
With the installation of contractions, the reliability of the rafter structure increases. The cross-sections of the timber are the same with the rafters. Attached to the legs with bolts or nails. The device of struts adds rigidity to the structure. They are installed tightly, to the surface of the rafters.
The lumber has a standard length of 6 m. The rafters can be longer. Then you need to dock them. There are several ways to connect:
- Fasten by putting the bars on both sides at the junction, connect them with nails in a checkerboard pattern.
- Overlap, one part of the rafter to the other, at a distance of 1 meter, fasten with nails in a variable order.
- Cut obliquely, cut out part of the rafter legs, connect them, fastening them with bolts.
Sheathing device
A crate is arranged along the roof rafters. It serves to distribute the load from the roofing material, snow onto the rafters. Plays the role of an air gap between the roof and the rafter system.
The design of the lathing depends on the adopted roofing material:
- under the soft tiles, the sheathing should be made solid, an anti-condensation film is laid on the rafters, the counter rail is pressed on top, the sheathing is nailed onto it, then OSB boards and a lining carpet, we put the tiles on the top.
- under the roof of the corrugated board, the crate should be sparse. The step of the lathing depends on the brand of the corrugated board, its thickness and the angle of inclination of the roof.
- the crate for standard slate should be made with a step of 500 mm from a bar of 75 × 75 mm or 50 × 50, as well as boards from 30 × 100 mm. The design features of the roof should be taken into account when making the final choice of a suitable option.
The lumber from which the crate is made is pine of the first or second grade. It is advisable to take the width no more than 14 cm. When the width is more, the boards can warp and damage the roofing. The length of the nails should be three times the thickness of the sheathing. Lay the boards along the ridge. Install the first board with a greater thickness to the height of the roofing.
Arrange a continuous crate along the roof slope.
With the first layer, lay a board along the ridge at a distance of 500-1000 mm from the next one, and so on. With the second layer, lay the crate along the rafters. Arrange the joint between the boards only on the rafters in a run. Insert the nail completely with the head into the pulp of the wood.
Eaves overhangs
They are installed to protect from atmospheric precipitation, play an aesthetic role. Eaves overhangs are arranged tightly without cracks. The final stage of roofing.
Diagram of the device for the eaves overhang of a gable roof
Gable
The gable roof has two gables. They have the shape of a triangle, with an apex at the ridge and the sides coincide with the roof slopes. The gables support the rafters and enclose the attic space. Protect from wind and precipitation, give stability to the roof.
In wooden buildings, the pediment is made frame. In brick buildings, frame or brick. The gables are made of brick or aerated block, erected before the roofing device. They require very precise execution.
The frame gables are inserted into the finished opening when the rafter system is already assembled.
The frame is made from bars or boards. The elements of the frame are connected on thorns or in the floor of a tree, all fastened with nails. Sheathed by nailing boards, lining or siding, maintaining the color scheme in the decoration of the facade of the building. For the device of a window opening, an additional frame is made for it according to the size of the window. If the attic is insulated, then the pediment also needs to be insulated. The insulation is laid in the middle of the frame. Mineral wool insulation with low combustibility is used. From the outside, the frame is upholstered with a hydro-windproof film or a windproof membrane, from the inside, a vapor-proof film or a vapor-proof membrane is nailed under the finishing material.
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When constructing one-story houses, a roof with two slopes is very popular. This is due to the speed of construction. According to this parameter, only a single-slope roof can compete with a gable roof. In the device, the gable roof rafter is not too complicated. And you will successfully master this work yourself.
The structure of the rafter system of a gable roof
The gable roof consists of two sloping surfaces that have a rectangular shape. Due to this, precipitation, which is represented by rain and melt water, flows down from the roof in a natural way. The gable roof has a rather complex structure. It consists of the following structural units: Mauerlat, rafter system, filly, ridge, roof overhang, bed, struts, puffs, lathing and racks:
- Mauerlat. This element performs the functions of transferring and distributing the load created by the rafter system on the load-bearing walls of the house. For the manufacture of Mauerlat, a bar is used, which has a square section - from 100 to 100 to 150 to 150 mm. It is better to use softwood. The beam is placed around the perimeter of the building and fixed to the outer walls. For fastening, special rods or anchors are used.
- Rafter leg. The rafters form the main frame of any roof. In the case of a gable roof, they form a triangle. The rafters are responsible for the uniform transfer of loads to the Mauerlat. First of all, those that arise from precipitation, wind and the weight of the roof itself. For the manufacture of rafters, boards are used that have a section of 100 by 150 or 50 by 150 mm. Choose a rafter pitch of about 60-120 cm, depending on the type of roofing material. When using heavy flooring, place the rafter legs more often.
- Skate. This element connects the two ramps at the top of the roof. The ridge is formed after connecting all the rafter legs.
- Filly. They are a continuation of the rafters and form the overhang of the gable roof. It is customary to install fillets if the rafter legs are very short and do not allow the formation of an overhang. For the manufacture of this structural unit, take a board that has a smaller section than the rafter. The use of fillies facilitates the construction of the rafter system, as it allows the use of short rafters.
- Eaves. This part of the structure of the gable roof rafter system is responsible for draining water from the walls during rain, while preventing them from getting wet and rapid destruction. The overhang usually protrudes 400 mm from the wall.
- Sill. It is located on the inner wall and serves to evenly distribute the load from the roof pillars. For the manufacture of a log, a bar is used, which has a section of 150 by 150 or 100 by 100 mm.
- Racks. These vertical members are responsible for transferring the load from the ridge to the interior walls. To create this element, prepare a timber that has a square section of 150 by 150 or 100 by 100 mm.
- Braces. They are needed to transfer loads from the rafters to the load-bearing walls. The braces and braces form a solid structure called a truss. Such a device is designed to withstand loads at large spans.
- Tightening. This structural unit, together with the rafters, forms a triangle. It does not allow the rafters to part in different directions.
- Lathing. This construction consists of planks and beams. They are attached perpendicular to the rafters. The lathing is necessary to evenly distribute the weight of the roof covering and the loads caused by weather events on the rafters. In addition, the lathing is required to fasten the rafters together. When arranging a soft roof, to create a lathing, you should use not boards and bars, but moisture-resistant plywood.
Varieties of gable roof truss system
There are gable rafter systems with hanging and layered rafters. Ideally, the design contains a combination of both. It is customary to install hanging rafters if the outer walls are located at a distance that is less than 10 m. Also, between them there should no longer be walls that divide the space of a residential building. The hanging rafter design creates a bursting force that is transmitted to the walls. It can be reduced if you arrange a puff of wood or metal and place it at the base of the rafters.
At the same time, the rafters and the tightening form a rigid geometric figure - a triangle. It is not capable of deforming under loads that are in any direction. The tightening will be stronger and more powerful if it is positioned higher. Floor beams act as braces. Thanks to their use, the hanging rafter system of the gable roof acts as the basis for arranging the attic floor.
The rafters in their design have a support beam, which is located in the middle. It is responsible for transferring the weight of the entire roof to an intermediate pillar or middle wall located between the outer walls. It is recommended to install layered rafters if the outer walls are located at a distance of more than 10 m. If columns are present instead of the inner walls, you can alternate the layered and hanging rafters.
Diy gable rafter system
The roof must be strong to withstand various loads - atmospheric precipitation, gusts of wind, the weight of a person and the roofing itself, but at the same time it must be light, so as not to exert much pressure on the walls of the house. A properly constructed gable roof rafter evenly distributes the load on all load-bearing walls.
Calculation of a gable roof
The choice of slope for a gable roof will depend on the material you choose to install on the roof and the architectural requirements:
- When erecting a gable roof, remember that it must slope at an angle greater than 5 degrees. It happens that the slope of the roof reaches 90 °.
- For areas with heavy rainfall, and when the roofing does not fit tightly, steep slopes are made. In this situation, the angle should be 35-40 ° so that precipitation does not linger on the roof. But such an angle does not allow building a living space in the attic. A broken roof structure will be the way out. It will have a shallow upper part, and there will be a sharp slope at the bottom.
- In regions with strong gusts of wind, flat roofs are arranged. If constant winds prevail in the area, then make a slope of 15-20 ° for high-quality protection of the roofing.
- It is best to choose the middle option. Equip a gable roof that is not too steep. But also the slope should not be very gentle.
- When choosing a large roof angle, its windage increases, and, accordingly, the price of the gable roof rafter system and lathing. Indeed, such a slope entails an increase in the area of the roof and, accordingly, the amount of required material - building and roofing.
When buying materials for the construction of a gable roof, it is useful to calculate its area:
- Find the area of one slope of the structure, and then double the result.
- Ideally, a ramp is a tilted rectangle that runs along a long load-bearing wall. To determine the area of the ramp, multiply its length by width.
- The length of the slope is equal to the length of the wall. In addition, the length of the roof overhang above the gable is added to the length. Remember that there are tabs on both sides.
- The width of the ramp is the length of the rafter leg. The length of the roof overhang above the load-bearing wall is added to it.
In order to properly design the structure, it is recommended to carry out an accurate calculation of the rafter system of a gable roof, including determining the loads and characteristics of the rafters:
- When erecting a roof for a standard building, which has one floor, the design load on the roof will consist of two values. The first of them is the weight of the roof, the second is the load from external factors: precipitation and wind.
- Calculate the weight of the roof by adding the weight of each layer of the "pie" - heat insulation, vapor barrier and waterproofing materials, rafter system, lathing and the roofing material itself. Calculate the weight per m2.
- Increase the result by 10%. You can also take into account the correction factor. In our case, K = 1.1.
- If you plan to change the roof structure over time and increase the angle of its inclination, then consider a safety factor. Take immediately higher load indicators than those that you received at the time of calculation. It is recommended to start from the value, which is 50 kg per 1 m2.
- When calculating the load exerted by atmospheric phenomena, take into account the climatic features of the area where the structure is located. In this calculation, take into account the slope of the slope. If a gable roof forms an angle of 25 degrees, then assume a snow load of 1.
- If the roof is equipped with a greater slope - up to 60 degrees, the correction factor reaches 1.25. Snow load for an angle greater than 60 degrees is not considered.
- The rafters transfer all the load from the created structure to the load-bearing walls. Therefore, their parameters must be taken accordingly. Select the cross-section and length of the rafter leg, depending on the current load on the roof and the slope angle. Increase the obtained values by 50% to ensure a high safety factor.
Mauerlat installation methods
The construction of any roof begins with the installation of the Mauerlat:
- If logs or beams were used to erect the walls, then the upper beam will act as a mauerlat, as shown in the photo of the gable roof rafter system.
- If you used brick to build the walls, then brick the metal rods into the masonry. They must have a pre-threaded thread for attaching the Mauerlat. Install rods every 1-1.5 m. Choose rods with a diameter of at least 10 mm. Lay waterproofing between the masonry and the Mauerlat.
- For walls made of ceramic or aerated concrete blocks, pour concrete on top. Be sure to make the layer reinforced. It should have a height of approximately 200-300 mm. Be sure to attach metal rods that are threaded to the reinforcement.
- For the Mauerlat, use a bar that has a cross section of 15 by 15 cm.It will act as a kind of foundation for the rafter system.
- Place the Mauerlat on the top edge of the wall. Depending on its design, the Mauerlat can be laid along the outer and inner edges. Do not place it close to the very edge, otherwise it could be blown away by the wind.
- Mauerlat is recommended to be placed on top of the waterproofing layer. To connect all parts into one whole, use bolts and metal strips.
- To avoid sagging, make a lattice of uprights, struts and crossbars. To do this, take boards 25x150 mm in size. The angle between the brace and the rafter leg should be as straight as possible.
- If using a rafter leg that is too long, install another support. It should rest on the beds. Each element is associated with two adjacent ones. The result is a stable structure around the entire perimeter of the roof.
Fastening the rafter legs
The best version of the gable roof rafter system is a combination of inclined and hanging rafters. This design allows you to create a reliable gable roof and reduce the cost of building materials. Consider the following recommendations when working:
- Use only the highest quality wood as material. Beams that have cracks and knots cannot be used.
- The rafters have standard dimensions - 50x150x6000 mm. When the beams are longer than 6 m, it is recommended to increase the width of the board so that the beams do not break under their own weight. Take boards 180 mm wide.
- First, make a rafter leg template. Place the plank against the floor joist and the end of the ridge bar. Having outlined two lines, saw off the board along them. The template is ready.
- Cut the rafters using this pattern. After that, make the upper wash on them.
- Take the resulting workpiece, bring it to the floor beam to mark the bottom cut in place.
- Install all rafters. At the same time, remember that after installing one leg, you must immediately install the opposite one. This will quickly relieve the side loads on the ridge bar.
- If the slope is too long, then standard boards are not enough to make a rafter leg. In this case, two boards can be spliced together. To do this, wash a piece of wood of the same section on them. It should be 1.5 - 2 meters long. According to the scheme of the gable roof rafter system, the joint should always be at the bottom. Install an additional stand under it.
- Attach the rafter leg to the ridge bar with nails. Use self-tapping screws to fasten the rafters to the floor beam. Metal mounting plates are also suitable. In addition, a few nails are added.
- If you are building a structure exclusively from hanging rafters, then skip the next step. When erecting a structure with layered rafters, you need to think about the supports that are installed on the floor of them. To reduce the amount of deflection of the rafters, correctly calculate the location of such supports.
- If you are building a gable roof attic, the spacer pillars will frame the side walls.
- When doing this work, maintain a certain spacing of the beams. Set its size at the design stage.
- After installing the rafters, attach the ridge. It is placed on their top edge. For fastening, metal corners or staples are used. Bolts are the most popular.
Stiffening the structure
After installing the gable roof rafter system, strengthen it using the technology below:
- For small buildings, which are saunas, summer cottages, outbuildings, and roofs with the simplest hanging rafter system, connect each pair of rafters from the bottom using a tightening, and from above using a crossbar.
- For large buildings that are lightweight at the same time, install a lightweight roof. The walls have to withstand it.
- If the house is 6-8 m wide, then the structure should be tightened. Install in the middle of the support. Such racks are called headstock. Place them at each pair of rafter legs.
- If the span of the walls reaches 10 meters, then reinforcing beams will be needed. The struts act as additional support for the rafter legs for tightening. They are attached to each rafter - closer to the ridge or in the middle of the rafter leg. Fasten them to the lower end of the headstock and to each other, as shown in the video on the gable roof rafter system.
- In situations with long roofs, the gable beams should be relieved. This is done by mounting braces. The upper end should rest against the corner of the pediment. The lower one is attached to the central floor beam. For fasteners, use a bar that has a large section. This will prevent them from kinking in the event of strong gusts of wind.
- In an area dominated by wind, the rafters must be resistant to such influences. Strengthen them by installing diagonal ties. Boards are nailed from the bottom of one rafter to the middle of the next.
- For greater rigidity when creating the most critical fasteners, it is better not to use nails. Use pads and metal fastening methods for this. Nails will not be able to provide high-quality fastening, since the wood can dry out after a while.
Roofing system lathing
The final stage of the device of the gable roof rafter system is the creation of the lathing. It is on it that you will lay the roofing covering. Carry out the work in the following sequence:
- Select dry timber for the lathing. It should be free of cracks and knots. Nail the beams from the bottom. Attach two boards near the ridge so that there are no gaps. The battens must be able to withstand the weight of the roofing material and not bend under the weight of the workers.
- If you will be equipping a soft roof, make two layers of sheathing. One is sparse, the second is solid. The same applies to roll roofing. To begin with, parallel to the ridge beam, place boards that are 25 mm thick and no more than 140 mm wide. A small gap is allowed - no more than 1 cm. Lay a continuous layer on top. For this, it is better to use roofing plywood, slats or boards of small thickness. After that, check that there are no errors on the crate - irregularities and knots. Also check that the nail heads are not sticking out.
- Lay one layer of timber under the metal tile. It should have a cross section of 50 by 60 mm. Proceed in the same way when using slate or roofing steel sheets. Maintain a step between the timber, depending on the roofing chosen by you - from 10 to 50 cm. Drive nails closer to the edges of the board, and not in the middle. Drive the hats into the depths. So they will subsequently not be able to damage the roof. If you are making a crate for a metal tile, then remember that the connection of the timber at the same level should fall on the rafter.
When you have installed and reinforced the gable roof rafter system, you can start installing the roofing pie. Place a thermal insulation material, a vapor barrier and a waterproofing layer between the rafters. When using insulation in slabs, calculate in advance the pitch of the rafters for laying it. At the final stage, fix the roofing material.