Architects call the roof the fifth facade - it is one of the most expressive elements of the house. However, here it is necessary to maintain a balance between the design solution and the functionality of the roof. From an engineering point of view, the simpler the roof, the less hassle it will cause during construction and subsequent operation. When designing a roof according to a budget option, you should, if possible, avoid a large number of valleys, height differences in the ridge, turrets and arched forms.
In Fig. 1 shows the main types of simple roof structures, but this is just a sketch. To properly build a roof, a roof plan and main sections must be developed, taking into account the linear dimensions of the building and elevations.
How to build a roof plan? Let's look at this with examples (Fig. 49). Modern country houses rarely have a rectangular plan; most often they are built in the form of the letters G, T or in the shape of a cross. There are other planning solutions; now it is more important for us to understand the basic principles of constructing a roof plan. The layout of the house can be mentally divided into rectangles. We will conditionally call the largest rectangle the main room, and the smaller rectangles - extensions.
Rice. 49. Building a roof plan
Having drawn a plan of the walls, step back from the wall lines by 50 cm (normative roof overhang) and draw the outer perimeter of the roof to scale. Then we draw a purlin on the main roof ab, perpendicular to it we draw purlins on the extensions CD. Now if we connect the closing angles of the main roof and the extensions, we will get a valley line - the internal corner of the intersection of the roofs. Here the slanted rafter legs will be made.
With the same height of the roof ridges, the sloped rafters are installed along the entire length of the valley and will rest on the Mauerlat and purlin of the main roof; the angles of the slopes of the main roof and extensions will be different. The slopes will only be of the same slope if the width of the extensions is equal to the width of the main room.
Shortening purlins CD from the point side With changes the valley lines. Its location in plan at an angle of 45° leads to the fact that the slopes of the main roof and extensions will have the same slope, but the ridge of the extension will be lower than the ridge of the main roof. By changing the angle of the valley (in plan), you can change the height of the ridge of the extension to the required value. The sloped rafter installed in the valley, in this case, will rest on the mauerlat and the extension girder.
Shortening a purlin from a point A or b or on both sides leads to the formation of hips on the roof. The same can be done with the run CD, shortening it from the point side d we will get a hip on the extension. By the way, you can lengthen the purlins, then on the roof you will get triangular roof overhangs, enlarged at the ridge. If you completely “drive” a run, for example, a run ab, to one point, we get a hip roof, in which the slanted rafters will converge and rest on a single post.
In attic roofs, at any ridge height, the purlins of the extensions are connected to the racks of the sub-rafter structure of the main roof and rest on the grooves (Fig. 50). The nail connection of the nails with the racks is calculated by cutting the nails, or the nail is made to the entire height of the rack.
rice. 50. Option for joining two roofs. Endovy The roof racks, as in the case of hip roofs, rest on a diagonal rafter, onto which support bars are first sewn. The rule for installing splices is the same: they should be installed staggered, and not converge at one point on the rafter.
The slanted rafter leg in the valley, like all other rafters, can be made in a non-spaced or spaced version. The ridges, connected to each other in a ridge knot, rest against the sloped roof rafter at the bottom and transfer their compressive stress to it. At the same time, the slanted rafter leg, resting at the bottom against the Mauerlat, and at the top against the ridge assembly, gives a thrust to the Mauerlat, trying to straighten the joining angle of the Mauerlat beams. This spacer can be removed by tightening the tie located between the slanted rafters and the fixed post, and in the case of an L-shaped roof, between the slanted rafters of the valley and the hip, located on the other side. When changing the lower node of the sloped rafter leg of the valley from support to support, the thrust will not go to the walls, and the tightening (in this case it would be more correct to call it a contraction) will then be an element that will intercept the thrust that occurs in emergency situations, for example, when the ridge subsides.
In other words, diagonal roof rafters (hip or valley) are no different from ordinary rafters. If we stand frontally to them and look along a row of ordinary rafters, we will see in them all the same ordinary rafters, only loaded a little differently. Consequently, they need to be designed and installed according to the same rules as ordinary rafters, only consider their vertical projection and install the contractions accordingly.
Quite often, it is necessary to build an extension to an already built house, which will serve for household needs or as a site for summer recreation. Further in the article we will talk about how to make a roof on an extension to a house, what tools and materials may be needed, as well as in what order the construction work should be carried out.
Calculation of the slope of a pitched roof
In terms of design, the simplest roof is considered to be a pitched roof. However, even this type of extension roof requires some preparatory work. The first thing you will need to do is complete the roof design. At this stage, a drawing is drawn up indicating the planned slope of the slope.
It is worth noting that the slope of the roof directly affects the efficiency of its functioning, as well as the durability of the roofing covering. Of course, competent calculations will significantly simplify and speed up construction. The amount of roofing material used for an extension with a pitched roof will increase as the angle of the slope increases.
The calculation of the slope will depend, first of all, on the climatic conditions in a certain region. This angle will be steeper the more precipitation expected in winter in a particular region. A correctly selected value will allow timely and complete removal of rain and snow from the roof surface. At the same time, if a particular area is characterized by strong gusty winds, the slopes should not be made too steep.
The roofing material that will cover the extension to a house with a sloping roof also affects the slope:
- for slate or tiled roofs should be from 22º;
- roofing material laid in 2 layers requires a minimum slope of 5º, and in 3 layers - from 15º;
- The slope of the corrugated roof must be at least 12º;
- metal tile roofs can have slopes with an angle of 14º;
- ondulin, like roofing felt, is laid on slopes with a minimum slope of 6º;
- soft tiles are mounted on roofs with slopes inclined at least 11º.
Common practice shows that the maximum roof slope for an extension to a hipped roof is 45º. It is worth noting that the choice of roof slope angle will be largely influenced by the expected loads on the rafter system caused by wind and precipitation. A design error can result in additional costs if the extension falls due to excessive loads.
Necessary materials for the roof of a house extension
The rafter system of an extension with a pitched roof is made of wooden beams, on top of which the roofing covering is laid (read: ""). The frame is made of hardwood, which has been thoroughly dried, treated with antiseptics and primer. Additionally, it is worth opening all wooden elements with fire retardant substances. Such treatment can significantly extend the service life of the rafter system.
So, to create a roof over the extension you will need:
- beams for rafters, supports and other structural elements;
- edged board for cladding ends and sheathing;
- waterproofing and insulating material;
- roofing covering.
As for roofing coverings, as a rule, a gable roof with an extension is covered with the same type of material. At the same time, each owner proceeds, first of all, from his own material capabilities. If you are looking for an inexpensive way to cover a barn roof, you should pay attention to budget roofing materials.
The thickness of the beams will depend on the expected loads of rain and snow, as well as the total mass of the roofing material. In this case, beams with dimensions between 120×120 mm and 150×150 mm can be used.
Required tools:
- electric saw or hacksaw;
- drill;
- axe;
- screwdriver;
- hammer and furniture stapler;
- nails and screws;
- roulette and level.
The consumption of screws or nails is 8-10 pieces per 1 m2. As for the material for insulation and waterproofing, a margin of 10-15% is added to the total surface area for joining, trimming and overlap. The rafters are calculated based on the maximum distance between them of 1 m.
Installation sequence
If the preliminary design did not provide for the arrangement of a house with an extension under one roof, it is worth making sure that there is a gap of at least 5 cm between the roof of the main building and the additional room. In addition, it is important to correctly link the extension to the wall of the main house, so that rain or snow does not seep into the gap.
In order to attach the roof of the extension to the house as reliably as possible, construction must begin with laying the Mauerlat. It should be thicker, the steeper the slope and the heavier the roof covering.
This beam should be fixed to the walls as firmly as possible, since rafter legs will later be attached to it where the walls of the main house and the extension will connect. In this case, the installation of the rafters is carried out in pre-made grooves in the Mauerlat. Between adjacent rafters there can be a distance of 60-80 cm, but not more than 100 cm.
Please note that the slope of all rafter legs must be the same. Otherwise, due to distortions, water will flow under the roofing material and destroy wooden structures.
Upon completion of the construction of the rafter system, insulation work begins. In cases where the length of the rafters is too long, additional supporting elements are placed between them. On top of them, perpendicular to the rafters, a polyethylene film, roofing felt or other material for waterproofing is spread. To ensure tightness, the insulation is laid with an overlap and the joints are taped with construction tape. The roofing material is fixed to the rafters using a stapler.
How to join the roof to the wall
The junction of the walls of the house and the roof above the extension is additionally sealed to prevent water from flowing into the cracks. When planning the connection of the roof to the wall of the building, you should decide how to connect the roofs of the house and the extension. First, the top layer of roofing material is rolled out over the surface of the roof of the extension and heated with a blowtorch. After this, the material is glued to the main wall.
At the next stage, the sheathing is attached over the waterproofing layer. It is fixed perpendicular to the rafters from a 5x5 cm batten. The pitch of the sheathing is selected based on the type of roofing. If it is a solid material, then each sheet should be supported by at least two bars. For soft roofing coverings, a continuous sheathing is made of particle boards or edged boards.
The final stage of building a roof over an extension is the installation of the roofing covering. The method of laying it depends on the type of material. Be sure to make sure that the coating is laid in a continuous layer without gaps. Finally, the side parts of the roof are covered with edged boards.
Is it necessary to insulate the roof of the extension?
Work on insulating the roof above an extension can reduce heat loss, as well as increase the efficiency of heating, if it is provided in such a room. In order to carry out insulation work, it is necessary to make a rough ceiling before installing the waterproofing layer. The selected insulating material is laid on it, covered with a layer of waterproofing, and then all other installation work is carried out.
The inside of such a ceiling can be covered with plasterboard or moisture-resistant plywood. Don't forget to also insulate the ends of the roof to reduce heat loss due to side winds. In this case, any available material can be used
The external decor of the end parts of the roof above the extension can be made with any finishing materials as desired.
Good afternoon My question is this: I built a garage for a truck, length 9 m, width 6 m, wall height 4 m. I threw 10 half-beams of 180 mm across the walls, then on them rafters from two boards of 50 mm, each 6 m long. Next is the sheathing and corrugated sheeting with a thickness of 0.45 mm. In general, the result is a gable, equilateral roof, the height from the half-beam to the ridge is about 3.5 m. Then difficulties begin for me, namely: I want to build a one-story house close to the left side with dimensions: width 8 m, length 6 m, height 2.8 m The roof is similar to a garage, only both roofs will be perpendicular to each other, that is, the end of the roof of the house should dock with the left side of the garage roof. Now the question itself: is this possible, since the wall of the garage is 4 m, and the wall of the house is about 3 m, if possible, then how? I am sending you a photo (in the photo there is a garage with a brown roof, to the left is an empty area where I want to build a house).
Multi-gable roof
Unfortunately, I didn’t find a photo, but the question is clear. I don’t really understand why you made such a high roof in the garage? With a height of 3.5 m and a width of 6 m, it is quite possible to make a warm attic over the garage. What kind of roof are you going to make for the house?
The fact that the two buildings have different wall heights, of course, complicates the roof design. But in order to simplify the joining of two perpendicular roofs as much as possible, I would advise providing the ridge of both roofs at the same level. First, you will mount the ridge of a residential building, install the main rafters, and then proceed to install the valley. This is usually the most vulnerable point of a multi-gable roof and must be done very carefully. Here, as in a tray, two water streams meet. If you are going to use corrugated sheeting as a roofing building material, then a continuous sheathing must be made in this place. Then a special waterproofing carpet is laid, and then the roofing covering. Read more about the construction of the valley, wind boards, and ridge in the manufacturer's instructions for the specific type of roofing material. Since the height of the roof of a residential building will be large, you should immediately consider the possibility of constructing it as a residential attic with an insulated roof, especially since you indicated the width of the house to be 8 m. Good luck to you.
On a variety of buildings you can see a roof with two slopes. They choose it for a reason - it is a relatively simple and comfortable way to build a roof, reliable and beautiful to look at. But there are many subtleties that both builders and customers must take into account when creating it.
Advantages and disadvantages
The stability of the walls and the strength of the foundation, the elegance of the design of the designers can bring joy only in one case - when there is no “drip” from above. Technologists and engineers have put a lot of effort into inventing many roofing options. But in terms of the ratio of pros and cons, the classic pair of stingrays still takes one of the first places. These are two surfaces placed at an angle and having support points on load-bearing walls. The use of a gable roof is equally good for a shopping pavilion, a country cottage, or an ordinary canopy over a car or the entrance to a house.
Rainfall flows down from such a roof almost instantly. The snow doesn't stay on it. And even the wind will not be able to expose the underlying parts of the roofing pie of cabins, sheds, and outbuildings.
Below there can be a comfortable attic or even a full-fledged residential attic with large rooms. Consumers can choose different designs, modify the length of the slopes and the steepness of each of them.
Country houses are equipped with gable roofs most often not only because of their resistance to weather conditions and comfort. The anti-vandal properties of such structures also set them apart from others. Disadvantages are revealed only during the construction of attics. It is necessary to install dormer windows and strengthen the rafters. But even taking these problems into account, this format can still be considered a universal type of roofing.
Varieties
It is important to understand that a gable roof is not something single and monolithic; in fact, this name hides a number of subspecies.
- Traditional symmetrical design(base is an isosceles triangle, slope exactly 45 degrees). It withstands the pressure of snow and rain flows well, but cannot be used for the attic.
- Broken type increases the efficiency of using attic space. At the top the slopes are relatively flat, but at the bottom they are sharply inclined. An inevitable consequence of this choice is the complication of the rafter system.
- Roof without symmetry(such a “double slope” makes it possible to create only an attic of limited area). The main motive when choosing is an extremely unusual appearance.
- Asymmetrical multi-level(with different slopes) roof - in it the ridge is moved away from the center. The roof can serve as a canopy for a veranda or even a terrace located near the house.
Most practically used structures have inclination angles of at least 11 and no more than 45 degrees, because they are the most practical. In dry and warm climates, you can make the roof as flat as possible.
If the frequency and intensity of precipitation are very high, then you will have to build a steeper roof. But again, it has its own weak point - increased susceptibility to wind pressure.
Equipment of different slopes not only increases the area of the attic or attic, but also allows you to make their walls as straight as possible.
Asymmetry, if thought out properly and implemented technically competently, can become an attractive design solution. It has also long been noted that the difference in the parameters of the slopes increases the snow and wind resistance of the house. There is slightly less pressure than usual on the walls, rafters and foundation. And solar panels work much more efficiently on asymmetrical roofs. There is only one minus - the design and work will have to be entrusted to professionals.
Many gable roofs are equipped with dormer windows, which increase the attractiveness of the structure. The image of the house as a whole becomes more cheerful, the building acquires unique features. In a gable roof, windows in the shape of a quadrangle are often installed, although the number of shapes is simply impossible to count. Dormer windows are designed to replace doors for access to the roof during repair, finishing and emergency work, and in case of emergency.
A gable roof with short and long slopes requires the most careful measurement of all parameters and calculation of the necessary properties of the system. A hydraulic level can provide the necessary accuracy.
A roof with three gables is installed mainly on houses made in the shape of a square or rectangle. When equipping an attic, a separate roof is placed on it, and you can choose any type you like, including a broken one. Please note: the presence of three gables allows for enhanced lighting of the attic floor.
Quite a lot of roofs are made with a protrusion - this element helps organize canopies, awnings and cornices. A roof with a valley is equipped in cases where it is necessary to ensure that slopes forming a negative angle are connected to each other.
Such roofs can be made:
- in the shape of a cross;
- in the shape of the letter T;
- in the shape of the letter G.
Preparing a roof plan involves assessing its top view, in this case, all attic and dormer windows and points of connection of surfaces must be taken into account. Reflected in the plan of the roof over the terraces and verandas, for each surface and detail you need to write down the size. The master plan is divided into elementary figures; it must indicate where the main premises and extensions will be located. Only if this condition is met can it be guaranteed that all nodes, valleys, and protrusions will perfectly fulfill their tasks. If the size of the purlins changes, the angle at which the valley slopes is also adjusted.
Where such parts are located, the connecting slopes are covered with a continuous sheathing. When laying out waterproofing, it is recommended to place it in two layers, and then attach the valley to self-tapping screws. When the joints of the part are in a horizontal plane, the overlap is at least 10 cm, and ideally 30 cm. If the slope has only a slight angle of inclination, it is advisable to use an additional layer of waterproofing. A valley with a self-expanding seal is placed under the metal tiles.
A gable roof with a bay window can be quite inexpensive and quite beautiful. This element is placed on a reinforcing belt; to make it, they usually do not put one of the rows of bricks or blocks during construction. The belt will not only support the rafter beams, but will also strengthen the wall and reduce the pressure on the window lintels. The formwork can be made from old boards, and for the reinforcement itself a welded network with 5x5 cm cells is used.
The off-center shape is often chosen due to its increased energy efficiency. This valuable property is harmoniously combined with external attractiveness. Architects use a variety of tricks; original designs were especially popular in the middle of the last century. The most radical experiments, of course, did not justify themselves, but solutions in which one slope is directed to the south, and a different angle or length to the north. It is important not to forget in this kind of search that no one has yet canceled the careful calculation of wind and snow loads and the determination of the composition of premises.
The overall level of efficiency of a home, if everything is done correctly, is much higher than that of an ordinary house covered with a standard gable roof. Accurate calculations by the architects showed that if you introduce one angle steeper than 45 degrees, the unused space in the house will sharply decrease.
The original step is to imitate the roof of an ancient Russian tower. Moreover, it is much easier for modern builders than for their predecessors several centuries ago. Mathematics and effective computing programs come to the rescue, allowing you to calculate parameters as accurately as possible.
It is much more pleasant to install an attic under a pitched roof than under a regular one. A semi-dark nook almost right next to the ridge brings joy to few people, especially since sharply inclined slopes and sharp corners located inside and outside do not contribute to visual comfort. Instead of following the lead of designers who creatively play with a simple type of gable roof, it would be more correct to solve the problem radically. Roofing material with cut corners helps to cover those places where it is not possible to lay full sheets or rolls.
A popular type of gable roof is the gable form; it would be more accurate to say that this is an assembly of several roofs, each of which covers individual parts of the house and is mechanically connected to the others. The advantage of this solution is that it allows you to create both dormer windows and balconies. “Pliers” in the terminology of roofers are, of course, not a metal tool with sharp gripping edges, but pediments. The radical complication of the rafter system is justified by its external aesthetic appeal. To imagine what it all looks like, you need to look at any image of an ancient castle.
A gable roof can be not only steep, but also flat. The increased steepness of the slope strengthens the structure and makes its sophisticated strengthening less relevant. The need for lumber is reduced, and therefore overall costs increase. But if in a particular area there is a high probability of storms and hurricanes, or simply strong winds, it is better to choose a more flattened option. At the same time, a completely flat roof (angle of inclination 10 degrees or less) is also impractical - maintaining it and clearing snow often becomes a painful task.
It is important to consider that when choosing heavy finishing materials(corrugated sheeting and metal tiles) it is not recommended to make an angle steeper than 45 degrees. Then conventional fastening will be unable to prevent their rapid sliding along the diagonal slopes. And you will need to strengthen the fasteners and install additional elements. As a result, unnecessary expenses will appear - and this is not one, or even two thousand rubles (if you also take into account the work and complicated design).
You won’t be able to save money on building a completely flat roof either – you will have to create a particularly strong rafter system underneath it.
Device
Once the required level of roof pitch has been assessed, you need to understand its basic elements. And primary attention should be paid to such a detail as the Mauerlat. Builders use this word to describe a stable structure laid around the perimeter of the walls and used to secure the rafters. The Mauerlat ensures that the loads created by the roof overhang are distributed evenly to the limit. It also prevents various mechanical influences from tearing the roofing system away from the walls.
The protective characteristics of the Mauerlat are especially important when it comes to resisting gusts of wind. Some craftsmen and even architects consider it acceptable to construct roofs without this element, with direct connection of the rafters to the ceiling beams. But the simplicity of such a design results in the fact that 100% of the load is collected monolithically on the rafter supports. If everything is done correctly, these impulses are dispersed over a much larger area.
The Mauerlat can be made from:
- I-beam;
- channel;
- softwood timber.
The standard cross-section of the timber in such cases is 80x180, 100x100, 100x150, 150x150 or 200x200 mm. It is very simple to use; you just need to place a beam under the legs of the rafters.
When assessing the quality of wooden raw materials, one cannot ignore knots, which make up 2/3 of the thickness of the tree or more. Such defects threaten not just the release of resin outward, but also a weakening of tensile strength.
A gable roof over a lightweight frame house, which will not have to endure excessive loads, can be placed on a mauerlat made of joined boards. Some developers add steel pipes attached to the ends of the support part. The structures used must have a maximum cross-section that allows them to be passed through the rafter holes. Increased strength is no less important; it is even better to lay it in reserve. And you should not take pipes if you are not sure that they are made of high-quality steel.
The connection of the Mauerlat to the wall is carried out in strict accordance with technology that has been proven over decades. It is extremely rare to refuse a reinforced belt. And even if the building itself is strong and stable, it is still necessary. When there are aerated concrete walls below, it is worth spending time laying bricks or pouring plain concrete. These materials are less fragile and will avoid damage to the main part of the wall.
The size of the sealing belt is selected individually, taking into account the level of loads, including variable ones. But its width is always equal to at least the load-bearing walls.
A cornice (eaves overhang) must be present on any roof, and a gable roof is no exception. The purpose of such an element is to block water, which, when precipitation occurs, tends to penetrate into the space under the roof. Importantly, the cornice is one of the finishing elements, and when it is hemmed, the internal components of the rafters are covered.
The frame (box) for the construction of the cornice is made of a flat board that does not contain even single traces of bark and knots. An alternative to the cornice is the use of rafter extensions. You also need to think about covering the gables by at least 50 cm.
Please note: the internal structure of the cornice on the slope and on the pediment has little in common. If you do not want to delve into such subtleties, it is better to seek help from professionals.
Unlined overhangs have found their main application in the process of working on hip roofs; the hemmed type is most often used in combination with a hip roof with two slopes. The shortened format is compatible with absolutely any type of roofing structure.
The visor also extends beyond the main contour. Such a solution will reliably cover the wall and base from precipitation. It’s easy for people to hide there too: even if the rain pours like a storm, it’s always dry and comfortable under the forward part of the roof.
Calculations by architects and engineers show that a projection of 150 cm allows the wall to remain dry, regardless of the intensity and duration of the rain. But this is not the limit: the technical capabilities of modern builders allow them to build canopies twice as large. Such structures are used mainly as terrace organizers. On the hottest and hottest day, the overhang casts a shadow that protects the plants from the heat. You should not try to make such long visors yourself, the responsibility is too great.
The cross-sectional structure of a gable roof cannot be considered thoroughly studied., if we don’t mention the inclined elements of the rafter system. The slopes have struts that are firmly attached to vertically placed racks. It is not recommended to take boards for rafters with a cross section of less than 5 cm, and the width of the material is determined by its length. When calculating each part, attention is paid to how great the risk of its deflection under the influence of standard load is. An insulated gable roof implies an arrangement of rafter legs that requires a minimum number of cuts on the heat-insulating material.
Materials
Despite the availability of a wide range of roofing materials, a considerable part of developers unconditionally trust structures made from corrugated sheets. No wonder: it is he who combines those two qualities that many centuries have painfully tried to combine - high strength and aesthetic perfection. Russians especially value corrugated sheeting for its resistance to snow and ice, and for the minimal accumulation of solid sediment on the surface. Additionally, choosing blocks of two different colors will help to improve the design characteristics of a roof made of corrugated sheets.
It should be noted that even quickly falling raindrops still make a fair amount of noise. So that those living in the house do not feel like the inhabitants of a giant drum at such moments, they will have to shell out some money to purchase sound insulation. When the clouds go away and the sun comes out, another problem appears - extreme heat. To sunbathe, you need to take a pad of soft fabric with you and wear shoes everywhere. And if the corrugated sheet is damaged, corrosion will spread inside at amazing speed.
Typical fastening of a sheet involves screwing it to the substrate using 7 - 8 screws. These fasteners are placed in a checkerboard style, so the roof structure is held more firmly. It is prohibited to use nails to attach the corrugated sheeting, otherwise at the first strong wind it will go flying. The skates are pressed with screws to the tops of the corrugation every 3.5 - 4 cm. The ends must be covered with wind strips, screwing in the same screws in increments of 50 cm.
Important: you will have to work very carefully with a gable roof; this is an extremely dangerous type of repair. Even if the slopes are not steep, and the weather forecast indicates complete calm, you cannot climb up without a safety belt tied to stable parts of the buildings. All manipulations with the profiled sheet are performed exclusively with gloves; you cannot press it towards yourself or others.
Prohibited:
- throw damaged sheets from above, even after warning about this (scattering is unpredictable);
- leave the tool unattended;
- touch the profiled sheet and carry out any work with it without special clothing and safety glasses;
- bend sheets.
Gable roofing made of polycarbonate is installed almost exclusively over greenhouses and other secondary buildings. But even this circumstance and the high transparency of polycarbonate do not give the right to take its installation lightly! The advantages of this coating are ease of machining, excellent strength, and a variety of design elements. The absolute exclusion of corrosion and bacterial contamination will also please you. For installation, you will have to take self-tapping screws of a special type, which are able to compensate for the intense thermal expansion of polycarbonate.
The monolithic type of coating with a thickness of 1.2 cm is recognized as anti-vandal: the impact of a large hammer with great force does not leave visible damage. Resistance to snow and wind will also be a tangible advantage.
The cellular variety cannot boast of such mechanical parameters, but it is much lighter. The rafter frame under both types of polycarbonate is created mainly from wood.
Honeycomb sheets are used for arched and dome structures, and if you need to make an arch of a significant radius, you will have to additionally install:
- supports;
- struts;
- profile stiffeners.
Straight polycarbonate roofs are built over open terraces, gazebos and small garden houses. The rafters for them are made of boards 4 cm thick. It is mandatory to treat the wood with an antiseptic composition and fire retardants. But painting in one way or another is left to the discretion of the homeowners themselves.
Much more often than from polycarbonate, roofs are built from wooden beams. The most popular sizes of its blocks are 5, 8, 7-meter options. It is logical to use similar structures on houses that are generally made of timber - this will provide an ideal combination. It must be remembered that the high mechanical stability of such a material does not mean that it is permissible to load it with excess weight. Therefore, the first step when calculating a structure is to find out what the level of overloads may be. The side beams are pulled together on the top row - due to this, the pressure from the rafter joists is reduced.
The screed will have to be made in pieces measuring 15x10 cm. Siding is also used in finishing gable roofs (more precisely, their gables). Metal profiles are actively used as the main finishing material. When choosing it, you need to check the ratio of the width of the bottom shelves and the ridge (if the ridge is smaller, the water flow will be more active). You should also evaluate how correctly the side gutters are positioned and whether they are broken. Another important point is the marking: the profile for walls and fences is not suitable for riding work.
When working with a gable roof, it is imperative to use additional elements.
When metal tiles are used, they solve three main problems at once:
- formation of a single whole instead of isolated blocks;
- prevention of penetration of moisture and foreign substances into the gaps of profile sheets;
- improving the decorative qualities of the coating.
The most important detail of a modern tiled roof is the ridge strip, which ensures the joining of slopes directed at an angle to each other. If there is no such strip, they are in different planes and a gap appears through which precipitation and wind can penetrate. On metal tiles, skates are most often placed in the form of a semicircle with a radius of 7-12.5 cm. A more universal solution is to use a trapezoidal or figured structure. In the last two cases, you can extend the wing by 15-30 cm, focusing on the shape of the roof and the slope of the slopes; The skate itself has a length of 200 cm in any configuration.
In addition to the ridge, you will need other parts to help complete the construction of the upper roof assembly. Plank caps (flat, conical or tent-shaped) are used exclusively for semicircular ridges. With their help, birds are blocked from visiting the under-roof space and it is possible to avoid its clogging.
The sealing underlay under the metal tiles helps ensure that the profile is pressed particularly tightly against the base of the roof. Thanks to this, both rattling sounds and the penetration of water into the under-roof space are excluded.
On a sloping gable roof, valley strips must be used, placed in negative angles. They will receive precipitation flowing from nearby slopes and direct it into the drain. The internal strip is placed under metal tiles or other profile sheets. The outer one is placed on an already formed roof, and this part must be elegant in appearance - otherwise it will not fulfill its function. The end or wind strip usually looks like a profile sheet bent in length; it is attached to the ends of the gable units.
The drip tray and the cornice strip are closely interconnected and act as additional parts of the drainage system. The adhesive strips provide a connection between the roof covering and the elements protruding beyond its contour. Even if there are no chimneys, there will definitely be antennas, intersections with walls, and so on. In Russian conditions it will not be possible to do without snow guards. Saving on any roofing components results in serious losses.
A metal roof with lightning protection is the only practical option. Protection against lightning damage is achieved by using special lightning discharge receivers made using pin or cable technology. It is advisable to consult with specialists to ensure reliable electrical contact of the roof along its entire length. The rafter system as a whole and each wooden fragment individually are always treated with fire-resistant reagents. The costs of such treatment are relatively low, and it allows you to minimize the likelihood of a roof fire.
Gable roofs are often created from profile pipes.
For the most part, such elements are awnings over:
- car parking place;
- outdoor recreation area and barbecue;
- swimming pool;
- terrace.
The pipe allows you to create an impeccably strong frame, and a corrugated sheet or polycarbonate is mounted on it. It is recommended to choose a flat piece of soil as a working platform. Covering the area with concrete or tiles will improve the decorative qualities, and placing it on an elevated area will help eliminate drainage problems.
The cross-section of the profile pipe is determined by how significant the structure is formed. If you take a 6x6 cm profile, it will no longer support canopies wider than 4 m and longer than 6 m. It is not at all necessary to choose round pipes for columns - if the parts are connected at right angles, square blocks will be even more practical. In addition to bolts and welding, clamps and threads can be used to mechanically connect parts. Do-it-yourself dyeing is no worse than branded dyeing, but 30-40% cheaper.
Some home craftsmen and even professionals believe that it would be best to cover the attic roof with clapboard. The advantages of this material are its environmental safety, comfortable price and excellent appearance.
Cedar wood has an excellent visual texture, in addition, it is also extremely beneficial for health.
Solid pine is strong and reliable, somewhat cheaper than cedar blanks.
It is also worth considering pine, oak, spruce or larch - each of these options has its own advantages.
Dimensions
Calculating the height of the roof is very important, and if you make a mistake in determining the dimensions of the ridge, you may encounter problems during use.
Whether the roof will be low or large depends on many subtleties and nuances:
- climatic parameters of the area;
- organization of the attic under the roof or its absence;
- type of laying material.
The heavier the coating being created, the steeper its installation should be. As the size of a single element decreases, the ridge rises higher. But we must not forget that raising the ridge inevitably entails costs, and the amount of costs increases rapidly. According to sanitary standards, a residential attic or an actively used attic cannot be less than 150 cm in height and 120 cm in length. An exception is made only for very complex structures.
- The rafter frame with hanging rafters (truss) should be supported on the Mauerlat. The connection of the rafter frame with the Mauerlat in the horizontal plane must be movable. The rafter frame must be able to slide along the surface of the Mauerlat within certain limited limits.
- In a rafter system with layered rafters, to ensure the necessary mobility, the layered rafter must be able to slide along the surface of the Mauerlat. The layered rafter is often nailed to the mauerlat, using a limited number of nails, literally 1-3 nails. Due to the weakness of such a connection, the rafter will be able to move along the Mauerlat under the influence of a small thrust, preventing its further growth. A larger number of nails will lead to the transfer of an unacceptable amount of thrust to the wall and destruction of the wall.
- In a rafter system with layered rafters, you can reduce the transfer of thrust to the walls in another way. To reduce the thrust, the rafters rest against the Mauerlat, but make the connection of the rafters in the ridge movable. The layered rafter in this version should be able to slide already along the ridge run.
In short, a rafter frame with hanging rafters must be able to slide according to the Mauerlat, and the layered rafter must have a movable connection either with a mauerlat at the bottom, or with an opposite rafter and a ridge girder at the top, so as not to lose support for the stand there.
There are few experienced builders, weak connection between the rafters and the mauerlat often causes confusion. Contrary to the instructions in the project, they decide to “do it the best way” and do not spare rough nails or, when using metal corners to attach the rafters to the mauerlat, install more screws than indicated in the project.
As a result, the roof of the house will push apart the walls and the owners will receive a collapsing house. Visible damage may not appear immediately, but after several years.
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| Non-thrust connection of layered rafters with mauerlat and ridge girder. Sliding connection option with run. During the run, the rafters do not rest against each other, but lying nearby. Notching (notching) on the rafters does not rest against the run. Rafter rests on the mauerlat. Attaching the rafters to the purlin secures the rafter to the purlin during installation and allows the rafter to slide along the purlin. |
The same situation awaits if, unfortunately, the improvers decide to change the profile of the connection of the rafters to the mauerlat and the ridge girder. The layered rafter should not rest against two points at once - both the mauerlat and the purlin. The connection at one of these points, as indicated above, must be movable, sliding.
The hanging rafter should rest against the tie, but not against the mauerlat. The connection between the tightening and the Mauerlat must be movable.
The modern construction market offers special connectors made of galvanized steel - “sleds”. The connector parts are installed on the rafter and mauerlat (or purlin) and provide guaranteed sliding connection of parts.
To prevent the roof from being blown off the house by the wind
According to building codes the roof must stay on the house and not fly off the walls during hurricane winds, which happens at the construction site once every 50 years (see the map of wind load areas).
To prevent the roof from being blown off the house by a strong hurricane wind, the roof rafter system is fastened to the walls of the house. When choosing a fastening method, take into account the need to prevent the transmission of thrust from the rafter system to the walls of the house. How to do this is written above.
In buildings with masonry walls, the rafters are held together with wire ties with metal spikes embedded in the underlying layers of masonry, as shown in the figure. Instead of crutches in the masonry, wire ties are attached to the attic floor beams or to the reinforcement outlets of the reinforced concrete floor.
Fastening rafters to walls using wire ties provides some freedom of movement of the rafters along the mauerlat. This is necessary so that the thrust of the rafter system is not transferred to the walls.
To ensure the stability of a roof with hanging rafters to wind loads from below, from the attic side, The rafters of one slope are connected by a wind board. Without a wind board, the wind will cause the roof to shake. A wobbly roof can even gradually destroy a gable wall.
A wind board is not needed if a continuous flooring is installed along the rafters, for example, for a roof made of soft bitumen tiles.
In roofs with layered rafters Instead of a wind board, struts are usually made to the racks, placing them along the run.
Types and shapes of roofs of a private house
Shed roof usually has a slope of 14-26 degrees. ends layered rafters pitched roofs rest on load-bearing walls.
If the span covered by rafters is more than 6 m. That
A pitched roof is a technologically simpler design.
Gable roof a private house can have slopes up to 60 degrees. To cover the span between external walls up to 6 m. use rafter system with hanging rafters.
For longer spans or roofs with a small slope angle in the rafter system use layered rafters or roof trusses.
Hip roof It can also have an inclination angle of up to 60 degrees. The roof is more difficult to install than a gable roof, but due to the absence of gable walls has a lower construction cost.
For a hip roof layered rafters or roof trusses are used.
allows you to increase the area of the attic. The span between the external walls covered by such a roof is recommended to be no more than 10 m. The lower part of the roof slope can have an angle of inclination of more than 60 degrees.
You can make a broken roof shape for both a gable roof (in the picture) and a hipped roof. Broken roofs are more complex in design and installation, especially hipped roofs. For installation of broken roofs It is beneficial to use roof trusses.
What kind of wood are rafters made from?
The rafter system in private housing construction is most often made of wood. For strength, rigidity and durability It is recommended to use well-dried wood humidity 18 - 22%.
Well-dried lumber is noticeably more expensive. If the parts of the rafter system are made from wood with natural moisture, the wood will dry out during the operation of the house. As a result, the dimensions of parts will change, fastening points will weaken, and loads will be redistributed. Impregnation of raw wood with antiseptics and fire retardants is not very effective. All this will undoubtedly worsen the stability, reliability and durability of the roof.
For the manufacture of rafter system parts they use boards and beams made from 1-3 grades of coniferous wood. Material of the specified grade may have up to three knots with a diameter of no more than 30 mm per 1 meter of length. Non-through cracks of limited length are allowed.
Allowed to use well-dried hardwood- oak, beech, birch, subject to mandatory treatment of parts with an antiseptic.
Smoothly planed wood is more resistant to rotting and fungal attack.
Thickness of rafter system parts must be at least 50 mm and cross-sectional area at least 40 cm 2.
The cross-section of the rafters is determined by the project. Accurate calculation of the rafter system by a specialist designer, as a rule, allows you to save on the cost of materials.
If you rely on the advice of builders and contractors, they usually play it safe and overestimate the cross-section and number of rafters for the roof, which is natural leads to overexpenditure of materials and construction budget.
And the filly is better!
A filly is a board or block, attached to the rafter leg to create a roof overhang (see picture at the beginning of the article). The roof overhang is the lower part of the slope, located outside the outer wall - the part of the slope that hangs from the wall.
Applicable another way to install an overhang- when the length of the rafter leg extends beyond the Mauerlat.
- The rafter leg with fillies rests on the Mauerlat with its entire cross-sectional area, which increases the stability, reliability and durability of the connection of the rafters to the Mauerlat.
- The filly can be made of any required length, up to 1 m. The total length of a rafter leg made from a whole piece of lumber is limited and does not exceed 6.5 m. This is often not enough to extend the rafter beyond the wall to the required length.
- The fillies have a smaller cross-section, which provides some savings in material.
How to correctly connect the parts of the rafter system
Connections of rafter system parts must:
- Ensure the transfer of forces and loads in a certain direction.
- Withstand dynamic influences that change forces and loads in magnitude and direction (loosening).
- Ensure stability of characteristics when the properties of wood change - drying out, cracks appearing.
In modern house construction, the following is used to connect parts of the rafter system:
- Nails are regular and rough.
- Bolts and studs.
- Metal perforated galvanized plates with fastening to wood using nails or self-tapping screws.
- Multi-tooth plates, the teeth of the plates are simply recessed into the wood.
For joining parts made of raw wood more reliably use bolts or studs. Other types of connections weaken after the wood dries, which can lead to unacceptable deformations, loosening and destruction of the roof structure.
Roof ventilation
From the heated rooms of the house through the ceiling into the attic there is a constant flow of water vapor, which condenses on the cold surfaces of the roof. Condensation moistens the wooden parts of the rafter system and the attic floor, and the insulation also suffers from moisture.
To protect against moisture from condensation, install attic ventilation— the space between the heated room and the roof.
In the attic, water vapor penetrating from rooms in the house freely escapes through gaps in the roofing and special ventilation holes in the roof ridge, as well as through windows in gable walls. In flat roofs and residential attic roofs, a ventilated space (gap) is left between the roof and the insulation layer.
Flat roof ventilation. Water vapor entering the ventilated space escapes through ventilation holes in the walls. In the attic roof, the gap between the roof and the insulation must be ventilated through ventilation holes located below, on the overhang of the slope, and above, in the ridge of the roof.
Laying the roof covering
The roof covering on pitched roofs can be hard (ceramic, metal or polymer tiles, metal corrugated sheets, asbestos-cement sheets, etc.) or soft - bitumen shingles.
Rigid roofing sheets are usually laid on a sheathing made of wooden blocks.
Attic roof with rigid roof covering over sheathing To lay a roof covering made of rigid sheets, sheathing and counter battens are placed along the rafters. A vapor-permeable membrane is laid between the rafters and the sheathing. As a result, a ventilated gap is created under the roofing.
Drops of condensation from the roofing, snow and atmospheric moisture penetrating into the gaps of the roof fall onto the membrane and roll down it into the gutter. The membrane protects the insulation and rafters from moisture.
The ventilated gap reduces the formation of condensation on the surface of the roof covering.
To cover the roof slopes with soft roofing material, it is necessary to make a continuous hard flooring.
Attic roof with soft roofing covering on hard flooring. The size of the ventilated gap is set by galvanized wire stretched between the rafters. A backing made of roofing felt or other rolled waterproofing materials levels the surface of the flooring and reduces the mechanical load on the soft roofing covering.
Air outlets from the ventilated gap must be provided at the roof ridge.
In a house without an attic, if the attic is not in use, there is no need to lay thermal insulation, vapor barrier film and drywall. But vapor permeable The membrane and under-roof ventilated gap must be left.
Roof. Roof. Rafters. Rafter truss. Lumber. Board. Vapor barrier. Mineral wool. OSB boards
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