They say that the roof of a house is the fifth facade. Any owner country cottage knows well that the overall perception of the building depends on how well the roofing covering is chosen.
We have already told users of our site about the features of choosing a roofing covering.
But the roof is only visible part a complex system called a roof. The basis of any roof is a reliable and properly designed rafter system.
In this material, FORUMHOUSE experts will talk about the main nuances of constructing a rafter system for a wooden and stone house.
From this article you will learn:
General principles for choosing a rafter system for a stone and wooden cottage
Often, novice developers believe that the choice of rafter system design can be left “for later,” when the walls have already been erected. Practice shows that this is fundamentally wrong. The roof even country house is a complex system consisting of many elements. The design of rafters must begin at the design stage of the house.
Company Manager "DDM-Stroy" Vera Vavilova, Moscow:
– The rafter system is the basis (skeleton) of the roof of the house. The quality and durability of the roof directly depends on how well it is done. The manufacture of this structure, especially complex ones, must begin with its design. This is the only way that will allow you to take into account all the nuances and install it efficiently.
The service life of the roof largely depends on how well this structure is chosen and installed. It is also necessary to maintain a balance between functionality and design delights.
Director of company " Smart-Stroy" Pavel Orlov:
– Designing a rafter system begins with choosing the type of roof - attic or cold attic. For mansard roofs, the angle of the rafters is 35 degrees and above. For a cold attic, the base angle of the rafters is 25 degrees.
The simpler the roof shape, the simpler design, the faster it is to manufacture, and the less likely builders are to make a mistake. Therefore, it is cheaper to build and easier to operate a roof that has simple form. Big square roofs, the presence of bay windows, and the complex polygonal shape of the building significantly complicate and increase the cost of the design of the rafter system - it requires competent design and calculation.
The most cost-effective rafter system is the simple one gable roof with an inclination angle of at least 25 - 30 degrees.
The main factors that influence the complexity of manufacturing and the final price of the design:
The design of a rafter system (especially a complex one) should be carried out by a person with relevant experience. This design is always calculated for a specific building. The common approach – “I’ll make a rafter like my neighbor’s” – leads to disastrous construction results. The rafter cannot withstand the loads, which ultimately leads to expensive alterations.
Design begins with collecting the expected roof loads.
1. Constant values, including the total weight of the roofing covering, thermal insulation material and fastening elements;
2. Temporary quantities. These are the loads that are exerted on the roof climatic conditions, especially snow and wind.
Designers set the design pitch of the rafters in accordance with the expected load. Let's see how true this is.
Pavel Orlov:
– In my opinion, it is better to choose the pitch of the rafters for attic, well-insulated roofs based on the size of the insulation - so that the distance between the rafters is 1 cm less than the width of the insulation. This will make it easier to install.
The main load for which the rafter system is calculated is snow. Usually all such structures are designed with a margin, but if there is any doubt (it is intended to install a heavy roofing covering - natural tiles etc.), you can slightly reduce the pitch of the rafters.
Although the snow load is variable, the rafter must be calculated taking into account the totality of all loads acting on it. The calculation must be carried out not “back to back”, but with some reserve in case of heavy precipitation (prolonged snowfall) or increased wind load.
The “work” of the rafter system is significantly influenced by the choice of material for the walls of the house.
Features of the rafter system in a wooden and stone house
The main difference between the rafters of a stone house and a wooden one is that stone walls have a structure that is not subject to shrinkage and deformation.
Pavel Orlov:
– The rafters of a stone house do not need deformation elements, since stone house practically does not shrink. main feature rafter system of a stone house is the need for reliable fastening of the Mauerlat. IN wooden houses The role of the Mauerlat is played by the wall.
Mauerlat is a roofing element (paired boards 50x150, timber sized 100x150 or 150x150), which is laid along the entire perimeter of the upper wall of the house. The lower part of the rafters rests on the mauerlat. Thus, the Mauerlat redistributes the point load transmitted from the rafters to the entire area of the upper part of the wall.
Also, when designing the truss system of a stone house, it is necessary to take into account the thickness of the walls.
Pavel Orlov:
– The design requires calculation of the permissible lateral load of the rafters on the wall with a fixed Mauerlat.
A thin and high wall can withstand a smaller one lateral load. This requires the use of rafters for the load-bearing structure additional elements– supporting posts and purlins.
Wooden houses also have their own nuances that must be taken into account when manufacturing the rafter system.
Vera Vavilova:
– The main feature is that the walls, which are the basis for the rafters, shrink and change their geometry as the weather, temperature and humidity change outside and inside the house.
The main element that compensates for the shrinkage of the walls relative to the rafters is a sliding support (also called a sliding support). A sliding support is necessary in order to compensate for distortions of the rafter structure resulting from shrinkage of wood due to natural moisture.
A sliding support is a composite fastener that includes a bent plate and an angle with a guide.
When the house shrinks, the rafter slides along the guide, thus compensating for all distortions in the overall structure of the house's rafter system. The sliding part of the support is attached to the rafter beam so that there is a gap between it and the rafter. And the corner with the guide is screwed to the beam.
The slide must be installed strictly perpendicular to the rafters, with a notch in the timber for installation of its base. In order to ensure that during shrinkage wooden structures to ensure maximum travel of the slide; when installing it, it is installed in the most extreme position.
The degree of shrinkage of a wooden house (and therefore the amount of movement acting on the rafters) depends on the material used in the construction of the walls. Timber with natural moisture shrinks more, dry profiled timber shrinks less, and laminated veneer lumber gives minimal shrinkage, etc.
The walls of a house made of dry timber can shrink by 6% of their total height. If we are talking about the walls of a house made of timber with natural moisture, then the shrinkage can be even greater. Our article explains in detail what are the pros and cons .
Construction of a roof on a log house
In addition to timber, wooden houses are built from so-called hand-cut logs. Practice shows that the rafter system of such a house has its own characteristics.
Dmitry Filippov, company specialist "Traditional carpentry technologies":
– In log houses based on a log frame, a male-slat roofing system is used plus a “sliding” rafter part.
Roofing in a house made of logs, installation.
The roof for a log house has its own design features. Lay down – horizontal logs, cut into the log gable (the upper one is the ridge) - they sit together with the log house. Afterwards, a board lining (aka ceiling) is laid on the logs (lay down). Next, the rafters are mounted (in gable roofs they are attached to each other at the ridge with sliding fasteners). Then a roofing pie is formed - vapor barrier, insulation, waterproofing, counter batten, sheathing, roofing material is laid on top.
Dmitry Filippov:
- Thus, the rafter part with roofing pie are not tied to the log house, but seem to “lie” on it, which allows the roof to retain its shape and integrity when the log house shrinks.
From our article you will learn about the types of structure and roof shapes of log houses.
Materials going to the rafters
In addition to taking into account the characteristics of wooden and stone houses, when designing a rafter system, it is necessary to understand the requirements for lumber.
Vera Vavilova:
- Pine and spruce will do. These are inexpensive wood types that meet the basic strength characteristics of rafters.
It is important to ensure that the lumber meets grade 0-2 according to GOST 8486. The rafter elements should not contain large falling knots, rot, wane and cracks. These vices weaken bearing capacity rafter system.
Pavel Orlov:
– Edged coniferous wood with a moisture content of up to 20% is used for the rafter system. All lumber used must be treated with certified fire-retardant impregnations.
If you place freshly sawn, raw wood on the rafters, then during the drying process the already installed rafters will move. This will cause deformation of the roof and roof covering.
To avoid this, it is better to make rafters from chamber-dried calibrated lumber.
Another option for materials used to make rafters can be trusses and glued beams.
The use of these materials is determined by the project, based on the size of the spans and the expected load on the structure.
Vera Vavilova:
In this case, the elements of the rafter system are manufactured at the factory and delivered to the site in the form of parts ready for assembly.
This neutralizes the so-called “ human factor" It also saves time, because such a structure is assembled faster than one made on site with inevitable sawing and fitting of parts on site.
Factory rafter systems are manufactured strictly according to the design and technical specifications. Thanks to this, a high quality of the base of the future roof is achieved, because the wood has already been treated with antiseptic agents, and the entire rafter system is assembled according to the principle of a designer.
Another material used in the construction of rafter systems for a stone or wooden house can be light steel thin-walled structures (LSTS). Such rafters do not need to be treated with antiseptic agents; they are light in weight, have a long service life and are highly fire resistant. Let's consider the main features of the rafter system built using this technology.
Deputy Commercial Director of the company "Polymetal-M" Andrey Usachev:
– The roof truss system, made using LSTK technology, includes galvanized rack and guide profiles. If necessary, devices warm roof a thermal profile is used (a profile with perforations along the entire length), which will remove the cold bridge and avoid heat loss.
The thickness and cross-section of the profile used in the design depends on the load expected on the rafter system.
Each element of the system has strictly specified dimensions according to the project.
This significantly reduces assembly time and also avoids waste on the construction site.
Each profile is marked in accordance with the drawings and assembly instructions.
Andrey Usachev:
– Markings make assembly easier. Each profile is marked with a punch (extrusion). Because the metal frame is fastened together with self-tapping screws, then thanks to the extrusion it is clear where the connection should be. The dowel increases the rigidity of the assembled assembly, reducing the shear force on the self-tapping screw.
In the FORUMHOUSE topic you can find out what begins. Also here you will find all the information about. Read on to learn how to build it yourself.
Watch our video about roofing in Russian wooden architecture.
Ratings: 0
Reading time: 5 minutes
In recent years, the popularity of log houses has been growing, and this is no coincidence. Such buildings, be it a house or a bathhouse, amaze with their unique atmosphere, which brings people closer to their origins. Natural wood is environmentally safe, and this is not its only advantage. The microclimate in such houses is always healthy and pleasant, but we must remember the characteristics of the logs. Structures made from them are characterized by dimensional instability.
Fluctuations in humidity can lead to certain linear movements that will be observed even after construction is completed. It must be said that the greatest activity in the movement of elements of a wooden structure is observed in the first few years. Then it decreases significantly, but the shrinkage does not disappear completely. After construction, the forest can sink by 20%, and when designing the house itself, as well as its individual elements, this must always be taken into account. Basically, the size changes across the logs, but the length of the trunk itself shrinks slightly.
Building a roof over a built log house is not as easy as it might seem at first glance. Such work requires enormous skill, knowledge of materials and carpentry skills. Before you get started, you will need to practice. In this article we will look at methods for installing roofs over a log house and talk about important stages installation Let's hope that the information will be useful for craftsmen and those who are taking on such work for the first time.
Flawless installation can only be achieved by taking into account the shrinkage of walls made of logs. You may need knowledge of ancient roofing technologies and modern installation methods. You need to understand that taking into account the characteristics of the material is not enough to correctly build a roof. There are components to which it is important to pay special attention so that the roof does not deform over time. It is necessary to choose the most rational method of construction. To do this, you should take into account the forces acting on each log and choose the right ways to dampen the action of these forces. Our company’s employees will develop taking into account all the features of this material and project.
It's no secret that log houses go well with a roof that has two slopes. Knowing what technologies are usually used, it is quite possible to carry out high-quality installation of a gable roof rafter system on a log house. Typically, the roof slope angle chosen is from 45 degrees and even up to 65. The figures below clearly demonstrate the types of roof angles for log houses. The roof can be:
It is noteworthy that construction from logs retains ancient traditions, but also includes new technologies that allow wood to move freely without the risk of destruction of the structure. The fact is that installing a gable roof rafter system on a log house involves two methods:
In some cases, the rafter and male system are combined. In the middle of the roof of the male type in in this case a hanging truss is installed. Often the beam of the ceiling-type log house itself - the translation - can act as the basis for the installation of inclined rafters, and in some cases it acts as a tie that combines the elements into a triangle called a hanging triangle. The principle of the device can only be understood by familiarizing yourself with the classic installation options. Let's look at some important points, which should not be overlooked.
When it comes to the male scheme, you can take advantage of the enormous benefits provided by chopped boxes. They can be assembled and also disassembled without difficulty, like a constructor. To do this, you need to remove the crowns from their places and install them on a platform that is ideal for these purposes. The area must be level.
When work takes place on solid ground, it is much more convenient. Spacers made of aspen chocks are mounted under the crown itself. They will reproduce the previous rows of the logs themselves. The result is the top of a house made of logs, which converges like a wedge. It is built as usual, but the width of the end walls becomes much thinner. The edges of the gables will resemble steps. It is not long logs that are laid on the walls of the existing box, but rather logs. They should not be inserted into all rows, but only after 2-3 rows. The sheathing will then be mounted on the floor, then roofing type material will be used.
A slightly ridged type will unite the tops of the existing males. The log that completes the pediment is always cut exactly at 2 edges. In this case, the protrusions resembling steps that the male has obtained must be sawed off or hewn into the shape of a triangle. The remaining open areas at the top are filled with shorties. Few people know, but the old craftsmen, when carrying out fastening, never used fasteners when installing the presented roof. This greatly extended the life of the wood, since there were no metal rods inside it that were prone to rust. Such structures could last for several hundred years.
In some cases it is not possible to construct a male roof. This can occur when the excess has been cut off from the legs or males too much, and the cut-in joints have suffered. In such a situation, the usual option on top should be supplemented with rafters, thereby eliminating the need to cut off the humps.
Alignment should occur along the very edges on top of the existing rafter legs. The rafters themselves should be created strictly according to the established template; notches, as well as the lengths of the legs, are always marked in it. Not too important high accuracy felling of future connections. It is better that the bowls are 5 cm larger than the arbis itself, since the log house will sag significantly for a long time and lose its former height. Behind the settling frame, the bottom of the existing rafters near the roof will sag, and the connection angle will decrease.
It is the wide notch that can guarantee complete safety during displacement. It is important that there is a small gap between the tops of the legs of the rafters resting on the ridge beam. When the rafters begin to gradually move apart from below, they will gradually move closer at the top. After the moment when shrinkage occurs, the tops must be connected with an overlay or a special tightening. Sometimes they are connected using a hinge joint and do not wait for shrinkage to occur.
In order for the roof to be reliable and not to be demolished from the house, it is necessary to tie the rafters through one, this happens in the 2nd crown from the top, into which the pins are driven, and wire twists are used for connection. Gradually the twists will weaken as they shrink, then they need to be tightened.
The fastening is similar to the previous one, but this option does not require slugs. The legs of the rafters are called layered for the reason that their top and bottom rest on supports that are completely independent. In this case, the heels from below rest on the crown, and it serves as a power plate. If we consider resting the top, then it must be said that in such a situation there are several options.
The legs of the rafters were called hanging ones, since they seem to hang over the box itself. They rest on the walls. A part of the rafter will serve as a support for the top. And the heels from below are connected using the tightening method. As a result, the rafters begin to resemble a triangle with equal sides. It is often called a truss, or called an arch. It is the tightening that is ready to accept the thrust that is transmitted to the walls.
The expansion is compensated, and this is a huge plus. A beam called a ceiling beam may well act as a tightening. It is impossible not to note one more advantage of the hanging or layered option. The roof is assembled at the bottom; it is not necessary to go upstairs. Under safe conditions, all rafter triangles can be adjusted and joined together. But such a system is not suitable for buildings with large spans. If the spans are more than 5 m, then the tie rods for them will bend from their own weight.
You must understand that the rafter system of a gable roof on a log house is installed taking into account all the important points, otherwise it may collapse. The presented diagrams and examples will help you choose the best option for construction. Whatever option you choose, it is better to turn to professionals in your field.
The InterCity company is ready to offer you best projects log houses and high level professionalism to implement on such a design. Any of the main versions the best specialists companies will adapt to individual conditions. By collaborating with us, you do not have to come to the site in order to supervise the work. InterCity is a team of professionals who can implement any project you choose.
Construction of a roof over log building- a difficult job that requires the master to have the skills of a skilled carpenter and knowledge of materials science. The performer will need to first practice making connections. He must take into account the traditional shrinkage of walls made of wood.
In order for a gable roof on a log house to be built flawlessly, you need information about the methods of its construction, including ancient roofing technologies. The information we offer will be useful to both independent craftsmen and service customers. construction crews for meaningful control.
The popularity of log baths, dachas, and residential buildings is justified by the amazing atmosphere that returns to folk origins. Buildings made from natural wood are distinguished by excellent thermal technology and an attractive price. A significant advantage is the ability to spontaneously allow excess evaporation to pass through. One cannot help but pay tribute to the solid environmental advantages.
However, the popular natural building material has an impressive list of disadvantages. In addition to flammability and sensitivity to waterlogging, carpenters-builders and future owners must be concerned about:
Without taking into account the above circumstances, the wooden roof will definitely “move away”. Gaps will appear between the foot of the house and the roofing system, allowing raindrops and melt water to pass through. The wood will then begin to rot, resulting in the complete destruction of not only the upper enclosing structure, but also the house as a whole.
Taking into account the specifics of the material is not enough for the competent construction of a wood roof. You need to familiarize yourself with all possible ways construction in order to choose an option that is rational in terms of cost and effort. You need to understand what forces will act on walls made of logs or timber, and what method can be used to extinguish their effect.
Roofs with two slopes are ideally combined with chopped feet. Two steep slopes create the impression of a fairy-tale hut. The most suitable tilt angle is 45º-60º, but there are variations in both directions every right to exist.
A rival in the field of arranging log houses for a gable structure can be one that has a similar or pentagonal cross-sectional configuration. Gable roofs over log houses can be insulated or cold, attic or non-attic. As finishing coating All types of roofing materials are applicable, including shingles and reeds.
IN wood construction Ancient technologies for constructing roofs at an angle have been preserved, and new methods have emerged that allow wood to move freely without the threat of destruction of the building. According to the method of installation, gable roofs of wooden buildings are divided into two fundamental categories:
In fact, roof manufacturers rarely follow just one technology. The rafter structure can be combined with the male system. A hanging truss can be installed in the middle of a male roof so that it does not sag under its own weight, coupled with the roof and snow.
There are schemes that are generally difficult to classify into a specific category, because their decisive design features can be classified in different ways.
For example, the ceiling beam of a log house, matrix or transfer, can play the role of a basis for installing layered rafters or serve as a tie that combines elements into a hanging triangle. The tightening of the truss can be moved higher, as was proposed, describing the construction of the roof over the attic half. There are a lot of options, but to understand the principle of their design, you need to familiarize yourself with the classic schemes.
It would be a sin for roof builders using the male scheme not to take advantage of the invaluable advantage of chopped boxes. They can be disassembled and reassembled many times like a children's construction set. Therefore, the upper crowns are simply removed from their proper places and installed on a suitable flat area.
It is much more pleasant to work on solid ground without risk; there is no need to move along shaky scaffolding and walkways. Under the crown, linings made of aspen chocks are installed. They imitate the previous rows of logs, thanks to which there is no slightest difficulty with leveling to the horizon and fitting nodes.
If we conditionally divide a log house into three horizontal parts, then the lower 2/3 will be on the walls, and the upper third will be on the frame of the gable roof. Essentially, this is a wedge-shaped top of a log house. They build it almost the same way, but gradually reduce the width of the end walls so that the edges of the gables resemble stairs with steps. Instead of long logs falling on the walls of the box, the logs are laid in a notch. They are not installed in every row, but after two or three.
Males, after being erected to full height, are filed down to form a clear triangular shape. Then the sheathing is mounted on the base, with roofing material on top.
The tops of the males are connected by a ridge strip, which can be laid in two different ways:
To make slugs, take the smoothest logs Ø 18-20cm. They are fastened with simple notches “in the paw” or complicated analogues “with a notch” or “spike”. Because the edge of the pediment is trimmed or sawed off, notches with horizontal parts of fastening units of the “in-a-pan” type are not suitable. After all, part of the load-bearing element of the connection will be removed during processing.
The length should form the gable overhang of the roof. Usually it is 0.5 m. If it is decided to increase the width of the overhang, the legs are laid in pairs or three in each “step” of the male to increase the load-bearing capacity of the structure. Upon completion of the construction of the roof frame, its geometry is checked by installing the board on an imaginary slope.
The bulges revealed by the board are trimmed off, the recesses are filled with wooden overlays. However, experienced carpenters advise not to sew on “patches”, but rather to trim more.
The old craftsmen did not use fasteners at all when making roofs on males. Structures of this kind are called nailless roofs. There were no gradually rusting rods in the body of the wood, so the structures lasted for hundreds of years.
It happens that the construction of a traditional male roof is not possible. For example, as a result of diligent cutting of excess from the legs and males, the cut-in joints can be significantly damaged. IN similar situations classic version simply complemented with layered rafters on top. The need to trim the humps then automatically disappears. The final alignment is done along the upper edges of the rafter legs.
The production of rafters is carried out according to a template with marks of notches and leg lengths. They are simply chopped with bowls. Accuracy in cutting the connections between the rafters and the beams is not necessary; on the contrary, the bowls should be 3-5 cm larger than the outline of the beam. The frame of the house will inevitably settle, losing height. The rafters will remain almost the same size except for a few mm. The settling box will drag the bottom of the rafters with it, causing the angle of connection between the bottom of the rafter and the top crown to decrease. Those. The rafters resting against the upper logs or floor beams will gradually move apart.
A relatively slight displacement of the rafters that is safe for the roof will be ensured by a wide notch. There should be a gap between the tops of the rafter legs resting on the ridge beam. Moving apart at the bottom, the rafters at the top will come closer together during a period of intense shrinkage. After shrinking, the tops are connected with a wooden overlay and/or a tie installed just below. Without waiting for shrinkage, you can connect them with a hinge unit, which allows the wooden parts of the system to move without creating gaps between the frame and the roof.
The lower heels of the rafters in the described scheme rest against the upper crown, which works like a Mauerlat, or against the edges of the mats - ceiling beams. The joints are made with tongue-and-groove notches, and the eaves overhang is extended with fillets. To prevent the gable log roof from being blown off the log house, the rafters are tied through one to the pins hammered into the second crown from the top with wire twists. In areas with high wind loads, you need to tie each rafter leg. After active shrinkage of the wooden structure, loose twists should be tightened.
The scheme is similar to the previous type, only the slugs are not needed at all. Rafter legs get their name from the fact that at the top and bottom they rest on independent supports. The lower heels rest on the upper crown, which serves as a mauerlat, or on beams ceiling. There are several options for supporting the top of the gable roof rafter system elements over the log house:
The eaves overhang of a slanted roof over a log house is most often provided by sewn fillies. Although it can be formed by extending the rafter legs, if they are fastened not with notches, but with sliding connecting devices. Sliding fasteners allow you to build roofs over chopped piles without waiting for shrinkage.
Hanging rafter legs got their name because they seem to hang over the box being built. They only have walls as lower supports, and the same part of the rafter located opposite serves as the upper support. The lower heels are connected by a tie, thanks to which the hanging rafters turn into an equilateral triangle, also called a rafter arch or truss. The tightening “takes on the chest” the thrust transmitted in a layered pattern to the walls.
Compensating for the effect of thrust by tightening is a significant plus of the hanging system. It was happily borrowed by builders of layered roofs, trying to minimize the forces that push the walls of the house when the load on the slopes increases. The role of tightening can be successfully played by a ceiling beam. And then it really will not become clear whether it will be necessary to classify it as a layered or hanging category. rafter frame gable roof.
The invaluable advantage of hanging systems is that for production With The roof sides of the log house do not have to go up. All rafter triangles fit together perfectly according to the template and are adjusted in safe conditions.
The first place on the list of disadvantages is taken by restrictions on overlapped spans. Systems without a central support do not cover long span buildings. When arranging a house up to 5 m wide, a simple rafter arch is used without additional parts that increase the rigidity of the structure. Tightenings for larger spans may bend from their own weight. To eliminate sagging, a headstock is installed in the center of the rafter triangle.
To understand the essence of constructing a hanging rafter system, let’s consider the technology of installing arches over a small log house. The lower heels of the rafters will rest on the ceiling beams; the connection of the upper edges will be reinforced with a wooden overlay and tie. We will entrust the formation of the eaves overhang to fillets, and we will entrust the responsibility of ensuring the rigidity of the structure to small supports. Males will not breed. The gables created by the slopes after installation work Let's sew it up with a board.
To mark the lines of the slopes, we find the centers of both ends and mark them on the upper crown. Focusing on the mark, we will vertically install a board, any longitudinal edge of which will repeat the imaginary central axis.
We equip both ends with boards and mark the height of the roof on them using a water or laser level. You need to stretch a construction cord between the boards to mark the ridge line of the roof.
The procedure for installing a hanging roof:
From the inside, the rafter triangles should be connected with diagonal wind ties. From the outside, the rigidity of the structure will be supported by lathing, the type of which is selected according to the type of finishing coating.
Those wishing to install a warm roof will need to install thermal insulation between the rafters. Waterproofing is laid on top of the rafters before installing the sheathing, regardless of whether the structure will be insulated.
The examples and diagrams of gable roofs over log boxes we have given will help you decide on the best construction option. Any of the basic versions can be modified and adapted to individual technical conditions. Information about the specifics of the device is useful both for those who are going to equip their property with their own hands, and for those who need to control the work.
The roof is the most important part of any house... Well, you already know this, so let’s skip the introductory overflows from empty to empty. The article will focus on roofs for log houses, and especially on roofing options for log houses with chopped gables.
By the way, speaking in strict terminology, the roof is the entire structure that crowns the house. And the roofing is the roof deck itself - slate, tiles, etc. Also: what is commonly called a pediment is, strictly speaking, a gable - continuation end wall house, that part of it that is limited by the slopes of the roof. The pediment is an architectural decoration, and it is usually separated by a cornice from the main facade.
And here is the pediment. Log houses, as a rule, have pitched roofs various forms. The most typical and simplest one for private houses is a gable (or gable) one. This is exactly what we will talk about in this article.
also in low-rise construction Attics, and accordingly mansard roof shapes, are popular. However, for the attic it is not necessary to construct a broken-shaped roof. You can make a so-called “half-attic” if you raise the walls by approximately 1/3 or half of the floor and install a regular gable roof. You can even get by with a regular gable (triangular) roof if it is wide and high enough.
In principle, you can cover the sheathing with slate, and you’re done. And to insulate the ceiling - the ceiling between the attic and the living floor. This is, of course, the simplest and most brutal option. Many people prefer to tinker more thoroughly with a roof, even a cold one - especially now, when so many materials have appeared, and according to the assurances of their manufacturers, you cannot take a single step without all kinds of steam, hydro and other insulation and insulation. But the key idea is that it is constructive to insulate attic floor(ceiling) is much simpler than the roof itself. Especially if we are talking about a log house with chopped pediments, and then it will be clear why.
On the other hand, you can make an insulated roof - for the attic, or in order not to make a separate ceiling (for example, in a bathhouse - in a relaxation room).
The rafters can be rigidly connected to the frame of the house, or they can be sliding (“floating”) - an independent rafter structure. Hard ones are traditionally divided into:
In a pure version hanging rafters are rare, they are often reinforced with crossbars, additional racks, jibs and other structural elements. The entire structure of a pair of rafters with other elements is called a truss. In addition to suspended and layered structures that are assembled on site, there are roof trusses that are assembled in a factory and delivered ready-made.
For a log house roof with chopped gables, only the option with sliding rafters is suitable.
All this is due to significant shrinkage of the log house. Now we are talking about gable roofs. It's simple: if some part of the frame is higher than another, then the geometry between these parts will change after shrinkage. Each log loses up to 15% of its diameter in the process of shrinkage, but this is a fairly large amount. For rounded logs the standard is 6-8%.
A chopped pediment is like this:
The logs in the gable (gable) part are called “males.”
If the log house is a flat box, then all its walls will settle equally. But if some parts (gables) are higher than others (longitudinal walls), then the difference in height between them will change, and if you build a roof on rigidly fixed rafters, then it will literally be torn off the frame, the males may fall out... In general, this is fraught with a serious emergency situation.
Here's how the chopped pediment shrinks:
For which log houses are rigid rafter structures suitable? For those without tongs! When the roof is placed on a flat frame box - for example, hip roof. Or you can make a frame pediment (with boards, a blockhouse, etc.) ... But this will not be quite a log house in its pure form.
A full-fledged log house with a gable roof can only have a chopped pediment. Why? Because the pediment is also a part of the house, and a considerable one at that. If you make it frame, it turns out that half the house is a frame assembly. Maybe this is practical - because it’s simpler - but in this case, it’s practical to build the whole house according to frame technology. Log houses are erected for their special merits, and if they are to be done, then do it sensibly and without half-measures.
Immediately after the walls are erected and before installing windows and doors. Sometimes there are recommendations: wait until the shrinkage takes place, or make a temporary roof. It's all nonsense. A house without a roof is not even a house yet. The geometry of the log house is formed during the shrinkage process with all the loads, that is, the house must be completed and the roof too. It makes sense to do temporary roofing only if you have difficulties with the construction of a permanent roof.
Technologies that make it possible to build a log roof that will survive shrinkage exist. There are no objective reasons to postpone construction.
It is clear that the attic is a living space, but the attic is usually not. The attic requires major roof insulation, the attic does not.
If we talk about the construction of a load-bearing roof structure in log houses with chopped gables, then it is much easier to make an attic. More precisely, an uninsulated roof. However, this does not mean that the attic space cannot be used as a living space. There you can arrange a summer attic.
In the old days in Rus' they didn’t make “warm” roofs, but they built them in the attic summer rooms. This part of the house was called “terem”.
To create a warm, all-season attic, you will have to tinker a lot with the roof. In this case, if there is a need and opportunity, wouldn’t it be better to build another full floor?
What are the advantages of a house with an attic:
What are the advantages of an attic? The living space of the house increases, but it’s not for nothing that you get it! Setting up a spacious attic will not cost much less than building another floor.
There are two fundamental solutions:
There is also a slab-rafter system, but these are the same sliding rafters, only with the addition of side flaps.
Essentially, this is butter, because in the first version load-bearing beams are located horizontally, and in the second vertically. Both designs are powerful enough to withstand the heaviest, for example, tiled roof. There is no point in duplicating them.
Another thing is that in addition to holding the roof, the sleds also rigidly connect the gables. And when rafters are added to such a structure, they do this in two cases:
It is likely that engineering solutions for arranging a warm roof on a slab base are quite possible, but they have not yet been developed, since for now developers have enough rafters. Therefore, if you plan to build an attic, you cannot avoid installing rafters if you do not want to experiment.
The rafters are attached above the ridge beam (in the old fashioned way: “prince’s slega”, “knes”) to the upper crown of the longitudinal walls by means of sliding joints, the so-called “sliding joints”. It looks like this:
This mount has two parts:
The length of the guide strip can be different, the maximum will allow the rafter leg to move down by 16 cm. This is more than enough to shrink the highest roof.
It is recommended to attach the guide bar along the axis of the rafter, and this is correct. However, then one wonderful nuance arises. In most photos found on the Internet, you can see that the corner is installed and secured perpendicular to the plank. Moreover, the top of the angle loop is located close to the top edge of the guide. It is not right!
The fact is that when shrinking, the rafter will not only move down, but also the angle between the rafter and the horizontal line between the top points of the walls will change (see above for the dynamic shrinkage diagram). If the rafter rests on a log, then the part of it that goes down to the plumb roof will rise relative to the wall, and the lower part of the fastening guide bar will rise up. But the position of the corner will not change, and the bar will cut into the corner with one edge. As a result, the movable connection unit is deformed.
True, if you cut out grooves for the rafters in the upper crown with a margin for the angle at which the rafter is lowered, then there will be no distortion, the plank together with the rafter leg will simply fall a little lower and will slide normally. But this point must be remembered when installing the rafters, and cut out the groove with a margin so that the rafter fits, or do not adjoin the support corner at the top closely to the guide strip, but it is better to do both.
Description of the dynamic scheme: One more thing: attach the corner to the supporting log closer to the inside of the log house - so that there is room for the board, which you will then use to cover the space between the rafters.
And the third important point. As a result of shrinkage, the rafters will not only move down, the angles of the roof will also change, not by much - by 3-5 degrees - but this is enough to create problems. One problem - in the sliding fastening - has already been noted. The second is in the connection of the rafters at the ridge. It must be hinged.
In many photos on the Internet you can see this:
And this is an example of fastening a rafter pair in a sliding structure! A slope angle of 3° with a shoulder of about 4 meters (the length of the rafters of a not very wide roof) can seriously affect the geometry of the roof. Rigid fastening of rafters in the ridge is unacceptable! Otherwise, the slippers will be of no use!
You need to fasten the rafters on the ridge either with an overlap, like this:
or this way:
Watch this video to, as they say, “see once” what we’re talking about:
Slegs are horizontal log beams that connect and rigidly fix the gables of the log house; are not only a natural constructive, but also an architectural element. For example, long logs (pomochi) protruding from the gables fit elegantly into the design of a “wild log house” - you can put a wide console on them.
A slab roof structure looks something like this:
What's good about this decision?
Generally speaking, the slab structure appeared much earlier than the rafter structure.
All of the above advantages of slugs are valid if nothing is rigidly attached to them so that this fastening prevents shrinkage. That is, if you nail the sheathing on the legs, then shrinkage will become a problem - the purlins will sink along with the males, but the sheathing and everything that you nailed to them will not.
But! You can lay boards on the beds without fixing them rigidly. Thus, we get either lathing or wooden - for example, plank roofing.
How to do it? It is possible, in principle, to nail the edges of the boards to the ridge beam (knes) along one line parallel to the axis of the knes - so that with a slight change in the angle at which the boardwalk will lie, it will not be torn off. But even this is not necessary.
The old technology of Russian wooden architecture suggests a solution.
The chickens cut into several side slugs. The chickens themselves were cut down from spruce trunks, and the hook was made from the root system. The hens supported the stream - a hollowed out log, against which rested the boardwalk - the roof plank. The upper part of the plank was laid freely on the ridge beam in such a way that during shrinkage the upper ends of the gables could freely converge. For this purpose, space was left during installation. The ridge beam (knes) was hewn on both sides so that the gorges would fit more tightly.
If you leave 10 cm for lifting the gorges along the Knes, then this will be more than enough, because when shrinking, the chicken will also fall, and therefore the gorges lying on the beds. From above, the gorge was pressed against the ridge beam with an ohlupnik - a heavy hollowed out log. In this way, the gorges were fixed both at the top of the roof and on the plumbs.
Of course, now no one forces you to meticulously follow the ancient technology; where appropriate, you can use nails, screws, etc. The main thing is to grasp the principle. What is it?
Here's what:
In the same way, today you can attach a continuous sheathing to a slab roof. If you don’t want to bother with chickens (although this is no more difficult than with a rafter system), then you can rest the boards against a hollow hollowed out in the upper crown. Moreover, you can do the opposite - attach the boards to the ridge beam, so that they then fall into the hollow in the upper crown. This is exactly how they work when installing a warm roof using “Norwegian” technology, which I will briefly discuss below.
This is a very conditional “disadvantage”. The point is that since the rafter system is now in fashion, no current engineering solutions have been developed for arranging a warm roof on slabs. Although such solutions are undoubtedly possible.
However, if you are interested in a roof with a “cold” attic, or a summer attic, then a slab roof is best option. The roof in this case is better - traditionally - planked.
It would seem: wooden roof? she'll rot!
This is wrong. A roof made of aspen (similar materials are shingles, ploughshares), or planks can last 40-50, or even more years. An additional advantage is that such a roof is easy and cheap to repair - you only need to replace the damaged elements. In the case of a major renovation of a plank roof, only the top layer of the gorges will have to be changed; the underlay, as a rule, remains intact.
What is a plank roof? This is the first layer of hewn boards, on top of which is the second layer. Birch bark (“rock”) can be laid between them for additional insulation, waterproofing and an antiseptic effect. Birch bark has powerful antiseptic properties, and extends them to those materials that come into contact with it. Soak something like this wooden roofs It’s not worth it - the rain will quickly wash it away anyway, and there won’t be much effect.
I recommend a very high-quality video about roofing in Russian wooden architecture :
As for the “warmth” of such a wooden roof, think for yourself. This, of course, is not 20 cm of some “Rockwell”, but two layers of tightly fitted wood covered with birch bark. In any case, it is warmer than bare slate, tiles, or metal tiles, etc. That is, for an attic or summer attic that is completely protected from severe cold and moisture - excellent. Yes, such a roof does not allow water to pass through. It does not need a vapor barrier (after all, it breathes, just like the walls of a log house!). Therefore, by the way, there is no need to fill wooden roof bitumen, or shove roofing felt there, as some strange people sometimes advise. Due to such attempts at “modernization”, the roof may, on the contrary, rot – because natural ventilation will be disrupted.
Similarly, a shingle roof has the same properties.
Simple and to the point about aspen shingles:
The difference between a gorge and a regular one edged boards The problem is that when cutting logs into boards, the natural structure of the wood is disrupted - the fibers are torn. During the production of planks and shingles, splitting occurs along the fibers, making these building materials better resistant to aggressive environmental influences.
In this case, the point is not in this specific technology - I won’t explain it in detail now - it’s in the principle of constructing such roofs. The general principle is the same everywhere.
As I already said, if you want to make an attic, then you will have to tinker with the slab-rafter structure of the roof. Moreover, the broken line mansard roof and the chopped pediment of the log house is a bad combination. If there is a log house and male tongs, then it is better to build a semi-attic.
Let me briefly highlight the main points of the general scheme:
So far, everything looks very much like a wooden roof on slabs, doesn’t it?
Get the basic idea: in this whole scheme, sliding rafters appeared only because it was necessary to put insulation, for example. In order to get a “warm” roof for the attic. In any other case, the roof could be laid directly on the first sheathing, or even immediately on the bottom!
This is the general principle:
For the construction of log house roofs with chopped (male) gables, if it is possible and even necessary to install powerful massive slabs, the installation of rafters is only necessary in the case of arranging an attic.
In general, you need to think creatively so as not to do bad, unnecessary work. And now many people have a strange and irrational belief that no matter what kind of roof there is, rafters are a must! But this is far from true.
A normal roof will also have a slope of 18-20 degrees. For shingles and planks - from 28. The lower the slope, the less materials and work will be required on the roof.
Finally, a video about making chickens - the structural elements of a “roof without nails” - is not so difficult:
Existing materials are varied both in technical characteristics and operational properties, as well as in texture and color.
The roof, more than other elements of the building, is exposed to the elements. It must withstand the weight of snow cover and prevent moisture penetration. All year round, the roof is tested by nature for strength. And also the roof is a very important architectural element of the building, which plays a big role in its appearance. What is the difference between the roofs used when building a log house? The appearance and functionality are determined not only by the features of the roof. After all, the condition of the roof during operation also depends on how competently the project was chosen and how it was implemented.
