The pitched roof of a house consists of a large number of parts, each of which is connected to the others in a special way. This connection is called a roof joint. In this article we will talk specifically about connection nodes, how they are carried out, what technologies are used, what fasteners are used.
Main parts of the roof structure
Before moving directly to the analysis of the topic of the article, it is necessary to indicate what elements (parts) the roof structure consists of. Let's list all the main parts and indicate their purpose.
Mauerlat. This is a beam that is laid on the walls of the house located along the perimeter of the building. The purpose of the Mauerlat is to evenly distribute the loads coming from the rafter system. After all, if there is no Mauerlat, then each rafter will put pressure on the wall pointwise. And it is in this place that the destruction of the wall structure will occur.
Rafter legs. They are made either from boards with a thickness of at least 50 mm, or from timber. Rafters are the basis of the roof; they form the slopes and bear all the loads acting on the roof structure.
Ridge run. This is the topmost beam, installed horizontally. Its purpose is to support the upper ends of the rafter legs. It is this that forms the ridge of the roof.
These are the three main elements of the roof, which will be discussed further. Of course, these are not all the details of the roof, and we cannot say that others are less important. It’s just that these three elements form the structure itself. The only thing that needs to be added is that some roof designs do not have a ridge girder. The rafters simply rest against each other with their upper ends. This type of rafters is called hanging, and with a ridge girder, layered.
So that the roof structure is as reliable as possible, it is necessary that the roof components are correctly connected. In this case, it is necessary to take into account the strength effective loads and their direction.
How to connect elements of a roof structure
More recently connection of wooden roof nodes carried out using cuts. That is, they cut the elements of the roofing structure in order to connect them along one fairly wide plane. Therefore, so that the roof parts do not reduce their strength characteristics, as well as bearing capacity, they were selected with a sufficiently large cross-section. And this is not economical. That is, the larger the cross-section of lumber, the more expensive it is.
Today, technologies for fastening components and parts of roofing structures have changed dramatically. To do this, use bolts, dowels or perforated metal profiles. The latter are made of galvanized steel, which makes it possible to use fasteners for a long time without losing their quality. At the same time, manufacturers offer a fairly wide range of them for each type of unit. The photo below shows some of these fasteners.
It should be noted that perforated profiles gradually replaced all other types of fasteners due to their strength, reliability and ease of fastening operations. After all, to do this, you just need to install the profile in the required place and fasten it to various parts with wood screws or ruff nails.
Let's now look at how to fasten parts roof structure to each other. In principle, there are two types of connections: Mauerlat-rafters, rafters-ridge girder. The remaining parts are connected parallel to these joints. He will also talk about them.
Connection of Mauerlat and rafters
There are actually a huge number of fastening options, from ordinary nails to perforated profiles. For example, the photo below shows an option where ordinary wire is used as fasteners. That is, a through hole is made in the rafter itself, into which a wire with a diameter of 6 mm is inserted. A hole is also made in the Mauerlat or in the floor beam.
Then the ends of the wire are pushed into this hole and twisted, pressing the rafter leg to the Mauerlat. The connection is actually strong and reliable, but the process is labor intensive.
Instead of wire you can use metal tape 3 mm thick. It is simply wrapped around the two elements being connected and secured to them through the strip with self-tapping screws, often with nails. In the latter case there is no need to drill through holes in metal. note that in the lower photo the fastening is carried out to reinforced belt anchor, which increases the strength and reliability of the connection.
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The next type of fastening is a perforated corner made of galvanized steel. Most convenient option, but as reliable as possible. To do this, the corner is simply installed so that with its mounting shelves it is pressed tightly against the plane of the Mauerlat and the rafter leg. Fastening is carried out with self-tapping screws or nails.
Attach corners It is possible not only with self-tapping screws or ruff nails. There is another more reliable option where bolts are used. True, holes will have to be made for them, which increases the time required for this type of work. But in in this case quality is paramount. The photo below shows just such a mounting option. Please note that the corner is attached to the mauerlat with self-tapping screws, and to the rafter leg with a bolt. In this case, one bolt is used to connect two corners located at opposite ends of the rafters.
And another mounting option - on the slider. This is a special kind fastener, consisting of two parts. One is attached to the mauerlat, the second to the rafter leg. In this case, both parts are not tightly connected to each other. This was done specifically so that the rafters could move relative to the Mauerlat during thermal expansion of the lumber. This means that there will be no loads that act on the junction of two roof parts. The photo below shows this connection option.
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Connection of rafters with ridge girder
Second main node wooden roof – joint between rafter leg and ridge beam. Actually a ridge knot rafter roof very complex, because it joins two rafter legs and timber. In this case, all elements are located in different planes, meaning rafters and beams. This means that to connect them you will have to use more than one fastening element.
To connect rafters to each other they use perforated plate. There are two of them, installed on different sides of the rafter legs to increase strength and reliability.
Perforated corners connecting the rafters to the Mauerlat. There are four of them, two for each rafter leg, installed on different sides.
It should be noted that fastenings can be carried out not only with self-tapping screws or nails. Often masters use bolts for connection paired fasteners.
Pay attention to the different type of fastening. Only corners are used here. This option is used if a 50 mm thick board is installed as a ridge beam.
Another interesting option fastening the rafter legs to the ridge span, for which special perforated profiles complex shape . Essentially, these are brackets into which the rafter leg is inserted. The bracket not only holds the parts together, it supports the rafter, reducing the load on its end.
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Pay attention to all of the above options for connecting the rafters to each other. They clearly show that the ends of the rafter legs are joined tightly to each other, for which they have to be filed at a certain angle. You can do without filing if you use a complex fastening lock consisting of several plates that are connected with bolts. In the photo below this connection option is clearly visible.
Connection of hanging rafters
The rafter system of this type differs from the layered one in that it does not have ridge girder. That is, the rafter legs in the upper part (ridge) rest against each other. To prevent them from leaving different sides, the rafters are connected to each other by horizontal tightening. The latter is a board located at any distance in height: above, below or in the middle.
It should be noted that hanging rafters They are not assembled separately on the roof. Of these, farms are assembled on the ground, which in finished form installed on the roof of the house. In this case, all elements of the truss are connected to each other by perforated plates.
Video description
In the video, the master explains how to assemble a roof truss using perforated plates and nails:
Other types of knots
As mentioned above, there are many details in a roof structure. Therefore, we will tell and show a few more important connection points.
If the span of the house is more than 6 m, then a rack is installed under each rafter, which itself must rest either on the concrete base or on the floor beam. In this case, the connection of the rack with the rafter leg is carried out using ordinary boards, as shown in the photo below. Although you can use perforated metal plates.
They are also installed under the ridge beam vertical support posts , which are fastened together with perforated plates. But some roofing structures use a completely different approach to solving the installation of a ridge girder. Under the beam, jibs made of bars are mounted, which are secured to the ridge with special fasteners made of metal. The photo below shows one of the options for this type of fastener.
Very often, when constructing a rafter system, it becomes necessary to lengthen the rafters themselves. This is not difficult to do, and craftsmen use several technologies where they use various additional fasteners.
Video description
The video shows one of the options for lengthening the rafters:
Roofing structures come in several varieties of their forms. Almost all models contain a large number of identical elements. But among them there is one design that differs significantly from the others. This hip roof . Its distinctive feature is that the rafters are connected by their upper edges to one point, which is called a ridge knot.
So, in order to connect the rafter legs to each other, you need a support to which they are attached. There are several ways to ensure high node reliability. The photo below shows one of them, which uses perforated mounting metal profiles U-shaped.
Conclusion on the topic
In fact, we have considered only a small part of the connecting nodes for fastening the roof truss system. But even with their example, the variety of parts and components becomes clear. That is, the roof structure is a complex system, consisting of a large number different elements and parts that are connected to each other in different ways.
Thinking about construction own home, developers are often quite lenient when it comes to flat roofs. Even in comparison with a single-pitched roof, not to mention a gable roof, and even more so a multi-pitched roof, it seems too “simple”.
But professionals know that it is not the one or the other that matters. architectural element or building materials, but how they fit into the architect’s plan. A house with a flat roof can look no less elegant than with any other roof arrangement!
Device flat roof
Moreover, among the undeniable advantages of a flat (soft) roof:
- Relatively low cost and available materials;
- Easy to install roofing;
- Ability to fully utilize the space under the roof and the roof itself;
- Safety in operation;
- Unlike roofing work, which uses other materials, installation of a flat roof can be done in the cold season using special technologies.
Types of flat roofing
Soft roofing can be of two types: non-exploitable and exploitable. The first is the usual flat roof(For example, multi-story building), which only builders climb to repair and maintain.
Operable roofs are used in industrial or civil buildings and structures where permanent or regular access of people to the roof is provided (observation platforms, solarium, etc.), placement of heavy equipment or objects, open and winter gardens, arrangement of parking for cars, helipad and so on.
Design Features
In contrast pitched roofs, when installing a flat roof, roofing piece and sheet materials are not used. The second name for this type of roofing - soft roofing - was given precisely by those types of insulating coatings that involve laying them with a continuous carpet: bitumen, polymer, bitumen-polymer. The roof must be elastic so as not to deform under the influence of temperature changes, moisture and mechanical deformations of the base.
All these properties are possessed by a membrane flat roof, which is a kind of multi-layer “pie” of layers of heat, steam and waterproofing, laid on a prefabricated or monolithic reinforced concrete slab, metal corrugated sheets and sometimes on a wooden base.
Pie flat roof
Depending on the purpose of the roof and the materials used roofing pie can be different. For example, when laying an existing roof on a reinforced concrete slab, it can consist of many layers, for example:
- Roofing technoelast layer;
- Leveling screed made of DSP;
- Vapor barrier layer;
- Thermal insulation layer (extruded polystyrene foam);
- Two layers of waterproofing;
- Leveling reinforced cement screed;
- Polyethylene film;
- Expanded clay layer (along the slope);
- A layer of glass insulation;
- Reinforced concrete slab.
In such cases, the fastening has to be done not through the entire roof, but by connecting the screeds and the layers of insulation lying above them.
When installing an unused roof covering, the quantity upper layers will be smaller, but the principle of the roof structure and the materials used remain unchanged: base - vapor barrier - insulation (mineral wool slabs) - waterproofing from roofing roll materials.
Since the top waterproofing layer is exposed to aggressive influence external environment(temperature changes, moisture, wind), and if it is damaged the entire roof suffers, experts have developed an inversion one, that is reverse order placement of layers: base - waterproofing - thermal insulation - protective material (for example, so-called geotextiles). The top of the roof can be filled with monolithic concrete.
What are “roof nodes”?
Flat roof nodes are all joints of the roof structure: connecting corners, places where the roof covering adjoins the walls (parapet) of the building or encircles chimneys, ventilation pipes, lightning rods, etc., interfaces with external drains.
In such places, installation is done especially carefully and carefully - if the tightness of the joining seams is broken, moisture penetrates inside. Therefore, roof components are usually additionally waterproofed (for example, using bitumen mastic).
Most often, leaks and destruction occur in the area where the flat roof adjoins the wall. It is this unit that requires special attention - both during its design, and during the installation of the roof, and during the operation of the roof. When the tightness of a joint is broken, even if water does not flow down the walls after rain or during a thaw, fungus or mold often appear on them.
The tightness of joints and assemblies is achieved through strict adherence to technology, as well as through the use of special sealants, also used auxiliary materials and components (construction parts): they make it possible to provide the roof with the necessary operational parameters, and therefore reliably protect the building from the vagaries of the weather.
Mounting points
Basic layers of a flat roof
An approximate diagram of the attachment point for a flat roof to the base may be as follows:
- Roofing technoelast layer;
- Technoelast lining layer;
- Top layer of insulation;
- Bottom layer of insulation;
- Vapor barrier layer;
- Concrete base or base made of metal corrugated sheets.
For fastening, a roofing disc dowel with a diameter of 20 to 190 millimeters and a long screw (FBD; FBS) or concrete screw are used. The length of the dowel is taken 10-20% less than the thickness of the roofing. The screw must penetrate into the corrugated sheet or concrete base by at least 20 millimeters, and the covering must be fastened only to the crest of the wave of the corrugated sheet.
When carrying out work, you must adhere to certain rules:
- The distance between the dowels should be< 20 см.
- When mounting a roofing pie to a corrugated sheet or to wooden slabs, it is pierced with a dowel assembled with a self-tapping screw. IN concrete base need to drill in advance mounting hole under a dowel or concrete screw.
- The mounted dowel must fit tightly to the surface to be attached.
Mount the coating to the base through its penultimate layer using a screwdriver without shock loads (rotation speed - 1500-2000 rpm). After fastening, the final layer of coating is fused to cover the dowel head.
Junction nodes
Roofing device
Areas where the roof meets walls, chimneys, etc. require particularly careful isolation.
At the junction of the roof and the walls, transition sides are installed and the roofing carpet is attached to the base in the same way as described above. For concrete and reinforced concrete foundations, you can use mechanical fastening with screws and fusing (gluing) an insulating layer, or combine these methods for reliability.
To seal the joints, a special universal polyurethane mastic is used. After application, it hardens under the influence of air, turning into an elastic, rubber-like waterproof mass.
Unlike some other sealants, its volume does not change. This mastic can be used for all types of flat roofs. It is applied with a brush or paint roller in two layers, the colors of which are different, and this makes it possible to control the thickness of the layer and its uniformity. In addition, it adheres well to all surfaces and is resistant to direct sunlight.
In addition to mastic, pastes based on bitumen, lime and special plastic clay are used to seal joints.
Auxiliary parts for roof assemblies
Roof waterproofing
Since embedding chimneys into a flat roof, ventilation pipes and other parts - a responsible process for assembling units soft roof Special materials and parts are used. For example, this is a special polymer (butyl) tape coated with aluminum. It is easy to stick to any base, and the gaps are sealed with polymer sealant or mastic.
Profiled sheet (profiles) in the best possible way has established itself as a roofing material due to its functionality and low price. Thus, the roof is made of profiled metal sheets is a fairly acceptable solution even for a beginner who decides to deal with this on his own not an easy task. Profiled sheets are a coating that is sufficiently resistant to any mechanical and atmospheric influences, they are quite practical, durable and have an aesthetically pleasing appearance. appearance. Of course, the numerous advantages of the material in themselves are not grounds for considering the issue of its mandatory use in roofing, however best material for quick installation and long-term functioning of the roof it is impossible to find. Moreover, even to properly prepare and strengthen the roof components from corrugated sheets, it will not require too much special effort. Taking into account the need to ensure a reliable connection between components of this building material, it should be understood that special attention in this process should be given to roofing units made of corrugated sheets.
Features of corrugated sheet roofing
Before you start covering the roof with this roofing material, you should consider its main characteristics and methods of organizing the roof connection. So, the main advantages of corrugated roofing are:
- high level of load capacity with a relatively low weight of the sheets themselves;
- corrosion resistance;
- long life of high-quality coating service;
- relatively easy installation the main types of corrugated sheets that are offered on the construction market.
Photo 1. Pediment unit.
They are sheets with a wave height from 8 to 44 mm, with a trapezoidal or sinusoidal profile shape. Lightweight corrugated profile sheets with a height of 35 and 44 mm are often used for roof construction. Wall and frame profiles are also actively used as a roofing material, the wave height of which varies from 57 to 114 mm, which adds additional rigidity to it.
Before you start installation roofing sheets, builders must take care of acquiring the necessary tools for their work:
- hacksaws;
- screwdrivers or hex drills;
- screws or self-tapping screws;
- waterproofing material;
- directly professional sheet;
- Preparation for work on installation of corrugated roofing.
Before purchasing the necessary construction material, experts advise preparing a platform on which the brought sheets can be placed.
After all, they should under no circumstances be deformed. Otherwise, it will be almost impossible to achieve a reliable connection of the roof to the roof rafters. Think in advance about the process of feeding sheets onto the roof; most often, devices such as winches are used, or you can install lumber rails. Most often, builders use logs.
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Main joints of material
Photo 2. Plank of the valley assembly.
The roofing material is laid on a sheathed truss system, which is created from bars with a cross-section of 50x50 mm, with a pitch selected according to the dimensions of the profiled sheet used. Roof insulation is usually carried out using thermal profiles and a gasket made of thermal insulation materials. To waterproof the roof, you will need waterproof coatings, for example, special membranes or hydrophobic films.
When laying the roof you should Special attention pay attention to the places where several sheets are joined or to those sections of the roof where it adjoins the wall of the building. These points are called nodes, and if you treat them carelessly during installation, then in the future, such roofs are unlikely to reliably protect the building and the people living or simply staying in it from adverse external influences. The sheets themselves are very easy to lay, because they are light in weight and do not require special skills from builders. But roofing units made of galvanized iron are quite difficult moment. Therefore, although roofing and occur quickly, joints take the longest amount of time.
It is especially important to properly handle the transition areas sheet material roofs from a horizontal plane to a vertical one. This unit is carried out according to the following scenario: a strip is installed at the junction, which will protect the roof from moisture and dust getting inside, before that a sealant is installed under the strip. At the level where the plank adjoins the wall, you will need to make a groove in it and install it in the groove. Then use dowels to attach the strip and seal all joints with sealant. It is recommended to connect the bar to the profile using self-tapping screws, which are screwed into the most protruding point of the wave.
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Main components made of corrugated sheets and materials necessary for their proper processing
Photo 3. Wall diagram.
There are several types of roofing units. These are pediment, end, cornice, and ridge units. Plus, the connection point to the wall.
The gable assembly (photo No. 1) is arranged using the following tools and materials:
- Profiled sheets.
- Screws - roofing self-tapping screws.
- Pediment strip.
- Waterproofing film.
- Wind board.
Nodal elements of the pediment are mounted on wooden frame, which must be treated with an antiseptic solution. Then lay a waterproofing layer, which is necessary to provide ventilation and protect the frame from condensation. A layer of insulation is laid on top of the waterproofing layer. Then proceed to covering the frame with bars. They need to be installed in increments of up to 40 cm. And only after that the entire pediment can be covered with corrugated sheeting. Secure the sheets with self-tapping screws, which should be screwed into the deflection of the sheet, using electric drill. The sheets are fastened together with self-tapping screws and rivets.
Photo 4. Correct organization of the ridge knot.
A dense flooring is made of edged boards, at the level of the existing sheathing, retreating a distance of 60 cm from both sides of the groove. Then install the valley bottom strips, with an overlap of at least 20 cm. When constructing joints of flat roofs, you need to use sealing mastic. Bottom bar attach first from the edges with nails, and complete strengthening must be done simultaneously with the final installation of the entire roof.
High-quality ridge unit device.
One of the most difficult and important points coatings gable roof is proper organization ridge unit (photo No. 4). In this case, the ridge strips should be laid so that the overlap is at least 10 cm. The corrugated sheets are fastened to the sheathing roofing screws, which are recommended to be installed after approximately 30 cm.
Installation of the junction strip.
The length of the junction strip is most often 2 meters. Lay these planks with an overlap of 20 cm. In those places where the plank will join the profile sheets, it should be reinforced with self-tapping screws. A suitable step should be 40 cm. The area where this plank is attached to the wall can be hidden under decorative cladding.
Currently, due to the emergence of not just new materials, but entire SYSTEMS of enclosing structures (consisting of heterogeneous materials), great attention should be paid to understanding the physical processes occurring in the upper enclosing structures - roofs. Without this, their competent design and construction is impossible.
Rice. 1. External and internal factors affecting the roof
Roofs are subject to a range of forces that are closely related to processes both outside and inside the building (Fig. 1). These factors include, in particular: precipitation; water vapor located in the external and internal air building; wind; solar radiation; temperature changes; chemically aggressive substances contained in the air, as well as some other components of the processes.
Influence atmospheric precipitation and wind
The wind throws water or snow onto the roof with force, which, if the design of the roof and the roof as a whole or its individual components is not well thought out, can lead to a leak in the roof as a result of water or snow getting into the joints of the roofing materials. In addition to rain, melting snow also affects the roof. The most vulnerable places on the roof for leaks are the frames of chimneys and ventilation pipes and the junction of the roof with various vertical surfaces: walls, gables, dormer windows.
The traditional technical solution for connecting roofs to walls and parapets, both frontal and lateral, involves making niches and grooves in the walls (parapets) along the entire length of the connection and installing galvanized steel roofing aprons in them. It is permissible to install aprons made of black roofing sheet, twice treated on both sides with hot drying oil and painted at least twice. Installing an apron without a niche or groove by pressing it tightly against the wall does not provide a proper connection, and the unit leaks. There are at least two reasons for this: firstly, the walls are not so smooth that it is possible to press the apron tightly against them; secondly, the sun will heat the apron and, due to thermal expansion, it will lengthen and bend between the fasteners, moving away from the wall (Fig. 2).
rice. 2. Traditional solutions for connecting roofs to walls and parapets Installing the upper part of the apron in a niche or groove eliminates this problem; here the leaks are covered from above with wall material, which reliably closes them from rainwater, but does not protect them from snow. Therefore, when installing an apron in a niche, it is recommended to make the upper part at least 100 mm high, and when installing it in a groove, it is advisable to seal it cement-sand mortar. It must be added right away that simply filling a high niche with mortar is practically useless, the mortar from there will crumble over time, winter frosts and wind will help, but it will still last 5–10 years. Protecting the apron with a solution will not allow the wind to blow snow into the groove, where it will melt and melt water will flow under the iron. The aprons are fastened with nails to antiseptic wooden plugs, previously laid in the wall, for example, during the construction brickwork. The installation pitch of the plugs is about 1 m. If you attach the apron to the plugs before installing wooden blocks triangular section, then plugs can be installed less frequently, and the edge of the apron will be pressed tighter. Securing the apron with a second triangular block will make the knot practically waterproof. You can plaster the groove and forget about it until the iron of the apron rots.
Along the length, the apron elements are mounted overlapping in the direction of the water flow. The overlap is made at least 10 cm. If the joining of the aprons is done not with an overlap, but with a lying seam, the knot will be more reliable.
To protect the junction of the roof and the parapets, a “roof” made of roofing steel, equipped with drip edges (curved “hook” edges), is installed on the latter. A parapet apron with drips extended beyond the walls protects the parapet from rain: water is diverted from the walls through drips, drops break off and fall directly onto the roof or onto the apron of the junction unit. There is less water flowing directly down the walls. The parapet apron is secured by pulling it onto T-shaped spikes, installed in increments of about 1 m and attached, in turn, with nails to antiseptic wooden plugs. In order to prevent the parapet apron from being torn off by a strong wind, it is allowed to fasten it from above with screws (with self-tapping screws into a wooden plug) through the roofing sheet with the installation of rubber washers under the screw head.
The junctions of roofs to chimneys and ventilation shafts. Brick pipes framed with aprons made of galvanized or treated black tin. The lower and side parts of the apron are laid on top of the roof, and the upper part is placed under it. The aprons are covered from above with an overlap of brickwork. When making an apron, it is recommended to adhere to the dimensions shown in Fig. 3, They provide protection from melted snow. During heavy winter snowfalls, the snow falls under inner side iron, the specified dimensions of the apron will prevent melt water from penetrating under the roof. It will simply dry out after traveling a long way.
rice. 3. Traditional solutions for pipe cutting units (dimensions in mm) In pipes, especially chimneys, the installation of wooden plugs is unacceptable, so the apron is fastened on lying seams, connecting all the roofing iron around the pipe into a single whole. If roofing is being done around ventilation shafts, then the apron can be fastened with nails to antiseptic wooden plugs. The grooves around round pipes, for example, asbestos-cement or PVC pipes, are clamped with another pipe of larger diameter. The gap between the pipes is filled with molten bitumen mastic or some other sealant. A large gap, before pouring the sealant, is caulked with a fibrous material, for example, linen strands or rope, impregnated oil paint or bitumen primer. After caulking, the gap is filled with sealant or covered with a greasy cement-sand mortar.
When installing roofs from piece materials, for example, slate, ondulin and the like, the amount of lateral and frontal overlap of adjacent sheets should be as recommended by the manufacturer of the material. An increase in the size of the overlap leads to unreasonable excess consumption of roofing material, and a decrease leads to possible roof leaks. Short overlaps can create a ventilated joint into which snow or rainwater, driven by the wind, or melt water as a result of capillary suction of the joint gap.
The free overhang of the roof should also be as recommended by the manufacturer of the roofing material. A short overhang does not ensure water drainage from the roof. Part of the water, rolling over the edge of the roofing material, will be torn off by the wind and thrown onto the wall, and the other part, as a result of the surface tension of the water, overcoming the force of gravity, will flow up the lower plane of the roof and will wet wooden sheathing and rafter fillies. A long overhang drains water well, but can be cut or bent (at flexible roofs) snow sliding from the roof (Fig. 4). And it’s good if the roof breaks off in a place where there is a free overhang; more often it happens the other way around, roofing material breaks much higher, right above the room that the roof is supposed to protect.
rice. 4. The roof of this house was laid in the summer of 2008, the photograph was taken in the spring of 2009. As one would expect, in March 2011, sliding snow broke off the roof overhang, breaking the slate above the middle of the sheet. There are no photographs of the destruction (I did not have a camera with me). Result: a roof with a free overhang of 20–25 cm was able to “survive” without losses, only two springs Rainwater and melted snow bags are dangerous on valleys - internal corners intersections of two perpendicular slopes. Here two streams of water meet, flowing into the corner, and the valley becomes a tray for water. To prevent roof leakage in valleys, in all cases and for any type of roof, a continuous sheathing is made and sheathed with roofing tin (Fig. 5), and the roofing covering is laid on them. Or a special waterproofing carpet is laid in this place, provided for such units by the manufacturer of the specific roofing material.
rice. 5. Traditional solution roof valley assembly devices Infrequent hurricanes passing through central Russia rarely destroy rafter system roofs, but they are capable of removing dilapidated or poorly secured roofing from a house. Tangential wind forces acting along the roof slope can tear off its individual elements. To prevent this from happening, install anti-wind brackets for roofs made of corrugated roofing sheets, T- and L-shaped brackets for metal roofs (Fig. 6), tie special type tiles to the sheathing. A wind board is installed on the gable side of the building (Fig. 5). Anti-wind staples can perform a dual function: to keep the roofing material from being torn off by the wind and to resist lifting from the action of sliding snow. This is especially true for attic roofs with a large slope, where there is no snow, and the roofing material is fixed almost vertically, its weight can be partially transferred to the brackets. To hold pieces roofing elements on the steep mansard roofs The staples must be pre-treated with hot drying oil and painted at least twice.
Effect of water vapor and air temperature
The topic of ventilation of the under-roof space is discussed in the section “Roof insulation”.
Solar radiation and temperature changes
Different materials have different sensitivity to solar radiation. For example, solar radiation has virtually no effect on ceramic tiles, as well as on metal materials without polymer coatings applied to them. On the other side, paints and varnishes are subject to significant destruction, which manifests itself in the form of cracking of paint on metal roofing. A number of materials do not change their physical properties, but loses its visual appeal - for example, it fades (paints and some polymer coatings). When choosing a roofing material, you should make sure that it has sufficient light resistance.
As enclosing structures, roofs operate in a rather harsh mode, experiencing the influence of temperature changes. As is known, all materials are subject to thermal expansion and compression to one degree or another. Therefore, in order to avoid deformation and destruction, it is very important that materials operating in a single structure have similar coefficients of thermal expansion, or that appropriate technical solutions. In other words, when installing the roof, you must follow the instructions offered by the roofing manufacturer.
Chemically aggressive substances contained in the air
A number of materials can be seriously endangered by frequent, sometimes daily, temperature changes from plus to minus. This tends to occur in areas with mild and wet winters. Therefore, in such climatic zones it is necessary to pay close attention to such an important characteristic of materials as water absorption. With high water absorption under positive temperatures, moisture penetrates and accumulates in the pores of the material, and at negative temperatures it freezes and, expanding, deforms the very structure of the material. As a result, progressive destruction of the material occurs, leading to the formation of cracks.
As a rule, in large cities or near large enterprises in the atmosphere there is a fairly high concentration of chemically aggressive substances, for example, hydrogen sulfide and carbon dioxide. Therefore, for all elements of building envelopes in such areas, it is necessary to use materials that are resistant to chemicals present in the air.
