Waterproofing the roof of a house under corrugated board: the importance of choosing materials. Types of vapor barrier materials for corrugated board

Decking is a popular and really justifying material for roofing, wall covering and other construction purposes. However, if you want the profiled sheet coating to perform its functions at 100%, and its validity period matches or even exceeds the declared one, it is important to take care of the hydro, steam and sound insulation of the corrugated board.

Do I need waterproofing under corrugated board - a question with a definite answer, the most important method is waterproofing the roof from corrugated board, and what it will be, it is advisable to decide at the stage of drafting the building project.

Any material for corrugated board, the purpose of which is its waterproofing, must be characterized by the following properties:

1. Waterproof
2. Resistance to mechanical stress
3. Thermal insulation qualities
4. Elasticity

Also, what is laid under the corrugated board should be well attached to the base of the roof in order to guarantee the safety of the material even with strong gusts of wind. In addition, a desirable, albeit optional, property of corrugated sheet insulation is heat saving, because the combination of corrugated board insulation and its moisture protection in a single material is an ideal solution for a home. Consider which types of substrates for corrugated board meet the above requirements and are best suited as a coating.

Exist several types of waterproofing under corrugated board:

• Mastic waterproofing
• Film waterproofing
• Gluing waterproofing
• Tiled waterproofing
• Sheet waterproofing
• Plaster waterproofing

Mastic waterproofing

Waterproofing roofing mastic is perfect for flat roofs. To apply such a coating under corrugated board, it is enough to treat the roof surface with a polymeric viscous mastic product, which, after hardening, forms a continuous elastic membrane similar to monolithic rubber.

Polymer mastic is notable for its perfect adhesion to concrete, metal and bitumen. The waterproofing roofing polyurethane mastic applied by a simple pouring method is highly resistant to oxidation, corrosion, temperature changes and aggressive environments.

An unprecedented advantage of the mastic coating is the absence of seams as such. In addition, minimal preparatory work is required before applying the mastic, because the coating is created directly on the roof. The use of roofing mastic is equally justified when waterproofing the roofs of residential and industrial buildings, but this insulation is especially relevant in the case of various building structures passing through the roof, such as braces for antenna stability and equipment supports.

Film waterproofing

The waterproofing film under the corrugated board is a laminated polypropylene fabric that is difficult to stretch and tear. Some types of film waterproofing provide for the presence of a special perforation that serves to drain condensate and steam, being, in fact, a vapor barrier for corrugated board. If water and snow get under the roof of a building, they are discharged together with water vapor into the outer space.

With proper operation of the waterproofing roofing film, there is no increase in thermal conductivity and excessive moisture; in addition, such insulation has a fairly good resistance to temperature fluctuations.

Laying steam and waterproofing roll material Izospan under corrugated board in non-insulated pitched roofs protects the attic from the effects of adverse weather phenomena, being an excellent example of modern film waterproofing. We offer you to watch a video about this interesting and easy-to-use material:

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Gluing waterproofing

Underlay waterproofing is the most popular protection against unwanted moisture penetration and includes roofing material, polyester, glassine, roofing felt, fiberglass and similar materials. The main reasons for the widespread distribution of varieties of gluing waterproofing are its affordable cost and ease of installation.

For example, roofing material for corrugated board is attached to the roof sheathing with screws or nails, although recently this type of waterproofing has been increasingly replaced by new construction market innovations - polymer-bitumen waterproofing materials that do not contain components prone to rotting.

Insulation works with mastic and roll materials are carried out on roofs with a slope not exceeding 60 degrees. The value of the slope angle determines the number of required layers of waterproofing, in particular, layers of reinforced mastic. Insulating roll materials can be laid on bases of different nature - wooden, metal and concrete. Sometimes it is allowed to lay insulation on the previous coating.

Tiled waterproofing

Some tile materials can also provide good waterproofing and insulation for corrugated board. The best of them is considered flexible shingles. Installation of such a substrate under corrugated board is very simple, while the material itself is quite durable and does not need special care.

Tiles made from a mixture of cement and quartz sand have the same properties, only gaining strength over time. But ceramic tiles are considered not very popular, because, despite their advantages, over time, such material can begin to absorb moisture.

In the following video, you will learn how the flexible bituminous tiles are installed:

Sheet waterproofing I

Sheet material for corrugated board is attached to the roof by welding or using dowels and screws. Plastic or metal waterproofing sheets are made of lead, copper, aluminum, stainless steel, as well as synthetic materials - vinyl plastic or plastic compound.

Plaster waterproofing

Plaster roofing waterproofing is carried out by applying polymer cement plaster - a waterproofing material for roofing based on building mixtures and various fillers. Such a coating for corrugated board is environmentally friendly, but over time this insulation can crack.

The roof protects the house from the rain. But how to protect the roof? The first thing that comes to mind is the finish. But its functions are slightly different, due to the fact that moisture can still penetrate through the roofing material. In the way of moisture, a real barrier and, in fact, the only protector of the roof from getting wet and the harmful effects of water is waterproofing.

The need for waterproofing a cold roof

The main task of roofing is to protect buildings from wind loads and precipitation. If without fail there must be three layers under the roof of an insulated attic (insulation, vapor barrier and waterproofing), then there may be nothing at all under the roofing of an unheated attic. However, in practice, on the other hand, a waterproofing layer is still mounted.

If the water sources were only outside, then you could basically do without waterproofing a cold roof, while hoping that the quality of the roof itself would guarantee the absence of 100% wind, snow, rain and any leaks. With proper installation of some types of roofing, this is true.

But the problem lies not in the precipitation itself, but in their condensate, that is, drops that fall from the inside of the roofing. The likelihood that condensation will appear increases if, for example, engineering equipment passes through the attic. These can be fireplace pipes, chimneys, as well as various elements of heating and hot water systems.

No matter how effective the insulation is, heat is always released, which is why a significant temperature difference occurs in the attic. Depending on the different temperatures, different amounts of moisture form in the air, and when warmer air is transferred to the roof, it reaches the “dew point”, which leads to condensation.

Therefore, there is no doubt about the need for waterproofing a cold roof made of metal, which makes it possible to facilitate the process of converting an attic into a residential attic, if you have such a desire. Therefore, it is not necessary to neglect the waterproofing of the roof, which protects the roofed space from condensing and atmospheric moisture.

In principle, in cold attics, all types of materials can be used for roof waterproofing: anti-condensation films, diffusion membranes and ordinary films. The owners most often choose anti-condensate films, they are cheaper than diffusion membranes. And their advantage over conventional films is that they have a fleecy layer on the inside, thanks to which they can retain condensate for a certain time, until conditions for moisture evaporation are created.

In a cold roof, a waterproofing film is installed under the profiled sheets at a distance of 5 centimeters (an additional structure is made for this purpose). With this, the temperature will equalize on the inside and outside of the sheets. A properly installed cold roof insulation system will provide just as much benefit in terms of structural integrity as the roof covering itself.

Roof waterproofing materials

For a variety of roofs, various materials are used as waterproofing: from common roofing felt in rolls and various mastics to superdiffusion membranes. What material to buy depends on the roofing pie and operating conditions. First of all, you need to decide on the roofing cake, and the choice of waterproofing material for a cold roof will happen on its own.

Coating insulation

Mastics are used as an independent type of waterproofing for flat and self-leveling roofs. But usually coating insulation is used as an auxiliary measure. Namely, for the purpose of repairing various rolled roofs, sealing displaced joints and cracks in rolled material, sealing dormer windows, pipe outlets, additional insulation of the ridge part, valleys, end parts and gluing bituminous tiles.

For the installation of a mastic roof, it is necessary to thoroughly clean the base from exfoliating parts, dust, and dirt. It is also recommended to additionally impregnate the base with a degreasing compound or a bituminous primer. But mastics cannot be used for sloped roofs as independent waterproofing.

Ruberoid

A very common and popular material for cold roofing, as it is relatively inexpensive. It is used for roofs with an angle of inclination from 0 to 25%. But still, he is rapidly losing his fans. The fact is that the roofing material has a low durability, and after some time of operation, all its shortcomings appear: the bituminous material is destroyed under the influence of UV, the cardboard base rots, integrity is broken, and leaks begin. In addition, it is based on exclusively combustible materials.

Its new analogue with some shortcomings eliminated is euroroofing material, which is based on a non-rotting material (polyester, fiberglass, fiberglass), which is covered with a special modified bituminous composition. Such euroroofing material has a greater durability and, accordingly, a higher price than its predecessor, but is still combustible and not environmentally friendly. From this it follows that the use of euroruberoid for roofing in small areas is often not profitable. But if these are flat roofs, then this option is suitable.

glassine

Glassine was once a fairly popular roofing waterproofing agent used in cold roof installations. It was he who replaced the roofing material, but also lost his popularity. The reason for this is rapid aging, low strength, loss of thermal insulation characteristics, and environmental friendliness. This insulation option is the cheapest, but at the same time short-lived. It follows from this that glassine can be used exclusively for temporary protection of roofing.

Membranes and films

Waterproofing films also include membranes made of polypropylene or PVC. Such materials are gaining popularity for several reasons: high waterproofing performance, high base strength, vapor permeability, durability (up to about 50 years).

Membranes are divided into the following types: diffusion, pseudodiffusion, superdiffusion and anticondensate. Each type has its own characteristics of application and its own purpose. Well, the price of membranes, unlike other waterproofing materials, is quite high. Moreover, their cost is often proportional to the characteristics of a particular material.

Pseudo-diffusion membranes are a film with a rather low level of vapor permeability - up to 300 g / m2 / 24 hours. Such a film can be used to protect a cold corrugated roof. In this case, there are no restrictions on its adaptation. If it is used in an insulated roof pie, then it is necessary to make a ventilation gap between the insulation and the film. For its device, an additional crate should be made. Because of this, the cost of such insulation may increase and amount to an amount equal to a conventional diffusion membrane.

Superdiffusion and diffusion membranes are called perforated film with high (more than 1000 g/m2/24 h) and medium (equal to 400-1000 g/m2/24 h) vapor permeability. For waterproofing a cold roof, this vapor permeability is sufficient. A ventilation gap is not required with this film. Such membranes have many advantages: they can be installed directly on the insulation; removes steam from the inside and at the same time does not let moisture in; it is a wind protection for the insulation, it retains heat in the under-roof space; in a dusty environment does not lose performance.

However, such material forms condensate on the upper plane when steam is removed, therefore it cannot be used under the roof due to the fact that it can corrode. If the finish coating is made of metal (zinc, steel, aluminum, copper), volumetric diffuse membranes are used. The layer that comes into contact with the roofing material acts as a kind of separator, which absorbs and thereby removes condensate from the metal roofing.

Anti-condensation membranes are also used for seam and metal roofs. The fleecy "carpet" is on one side of the film. With this side, it is turned outward to the finish coating, as shown in the video about the cold roof of metal. It is necessary to arrange a ventilation gap under the insulation, since with such protection the vapor permeability approaches zero.

Do-it-yourself cold roof waterproofing

Waterproofing that is properly built should be like a layer cake that needs a backing. Its composition depends on the type of substrate itself. Under a cold roof, this layer is performed as follows. The frame is laid on the truss structures from the counter-lattice and the crate. A waterproofing material is laid on the crate and pressed against the counter-crate.

For a counter-lattice, the best material is a rail impregnated with a flame retardant solution or an antiseptic, 4-5 centimeters wide and 2-3 centimeters thick. It is necessary to lay the boards of the crate horizontally, and vertically - the boards of the counter-batten. In this case, channels should be formed between the slats of the counter-lattice, which have a height of 2-3 centimeters. They are needed for ventilation of the roof. Maintain such a distance between the rails that the entire area of ​​\u200b\u200bthe channels is equal to 1/100 of the roof area.

Steam moisture can be removed by ventilation. With a roof slope of one hundred square meters, the area of ​​\u200b\u200bcommon ventilation ducts should be one square meter. Ventilation ducts must run all the way to the roof ridge so that moisture vapor can escape freely through the holes in the upper part of the roof.

The procedure for waterproofing a cold roof structure is as follows. Lay the overlapping waterproofing film along the roof eaves in successive rows. Lay the material horizontally, moving from the eaves to the roof ridge. The width of the overlap depends on the degree of slope of the roof, which is in the range of 10-20 centimeters.

The film is fixed using galvanized nails with a wide hat or staples of a construction stapler. The place where the film is joined is glued with adhesive tape to obtain complete tightness of the attic waterproofing. The subsequent layers of the waterproofing film are laid in exactly the same way. Their number is determined independently.

Between the rafters, the sagging of the film should be about twenty millimeters. There must be an air pocket of 40 millimeters between the thermal insulation and the film. In order to ensure ventilation of the under-roof space, a ridge air should be made on the ridge, that is, a gap between the axis of the ridge and the edge of the film. The required indent distance is 50 millimeters.

In areas where pipes, antennas and other communications are installed, the waterproofing film is attached to closely spaced lathing bars, having previously cut it. Use a construction stapler or double-sided tape. When roof windows are made out with a film, you should always follow the special instructions from the manufacturer of the material. A counter-lattice is nailed over the film with an interval between the bars of 10-15 centimeters.

Thus, with properly installed waterproofing, the overall service life of the insulation, roofing, and, of course, the entire roof will be extended. Therefore, it is necessary to be responsible for the choice of protective material from moisture and strictly follow the technology of laying waterproofing.

Waterproofing is a necessary element of the roofing pie, regardless of how the corrugated roof is equipped: according to the principle of a warm or cold roof.

No matter how well the roof is made of corrugated board, moisture can penetrate into the under-roof space through the joints of the roofing sheets and at the points of their attachment to the crate, causing damage to the supporting structures and ceiling finishes.

The reasons why waterproofing is installed under a cold roof from corrugated board

Precipitation

Decking cannot 100% exclude the possibility of moisture getting into the under-roof space of the house. Heavy rain or snowfall combined with intense wind can cause moisture to enter under the roof, which in turn will provoke corrosion.

Wear of fasteners and roofing modules

The peculiarity of the corrugated board is that its sheets are subject to thermal deformation, as a result of which the roof can pass moisture along the junction line of the roofing modules. Often, water penetrates under the roof and at the points of attachment of the corrugated board to the truss system, since over time the tightening of the screws weakens, and the rubber sealing washers are destroyed. The ingress of water into the under-roof space is fraught with wetting of the truss system with its subsequent decay, and as a result, the destruction of the roof frame.

Condensation

With a high-quality installation of a corrugated roof, when the roofing reliably protects the house from atmospheric moisture and leaks, theoretically, you can do without waterproofing.

But sources of moisture are not only rainfall from the outside. It is also condensation that forms on the inner surface of the roof due to the temperature difference inside and outside the house.

The likelihood of condensation becomes even higher when utilities pass through the attic: heating and hot water pipes, ventilation ducts or a fireplace chimney. Liquid and gaseous media circulating through such pipelines usually have an elevated temperature and heat up the air in the under-roof space, contributing to a more intense appearance of condensate.

What is suitable for waterproofing a cold roof under corrugated board

The main conditions that a hydrobarrier for a cold roof made of corrugated board must meet are moisture impermeability, mechanical strength, and resistance to temperature effects.

The most budgetary, but short-lived version of waterproofing is plastic film. Reinforced polyethylene membranes have slightly better strength characteristics. But against their background, polypropylene films and anti-condensate membranes, equipped with a non-woven viscose-cellulose layer, which actively absorbs excess moisture, win significantly.

As an under-roof waterproofing for non-insulated metal roofs made of corrugated board or metal tiles, the waterproofing membrane Ondutis D (RV) is optimally suited.

Conclusion

The ingress of even a small amount of moisture under the roof negatively affects not only the reliability of the roofing, but also the durability of the building structures of the whole house.

Properly selected waterproofing film is the key to a long service life of the roofing and interior decoration of the attic or attic space.

If earlier slate was widely used to cover the roof of a house, then nowadays there are much more materials that look great, are practical and durable. One of them is corrugated board - a universal metal profile used for various purposes. You can choose corrugated board of any color and cover the roof with it without any problems. It is a reliable and durable material, suitable for both warm and cold roofs. But, corrugated board cannot completely exclude the ingress of moisture into the attic. After all, even oblique rain with a strong wind or blizzard will penetrate under the roof. In addition, the attachment points of the corrugated board itself can let moisture through when the sealing washers are destroyed over time or they are weakened by the tightening of self-tapping screws during thermal deformation of the sheet. This phenomenon negatively affects not only the insulation material, but also the entire structure of the cold roof. So the coating will not serve you for a long time and may collapse. To eliminate this problem, waterproofing of the roof of the house under corrugated sheets is mandatory.

But a number of questions arise: what kind of waterproofing is needed? What functions does it perform? Do I need a waterproofing layer under the cold roof corrugated board? How are the works performed? Let's look at the answers to these questions.

The functionality of the waterproofing layer

What is waterproofing for corrugated board? This is a rolled material with which the roof is sheathed. If it is warm, then the material is attached directly to the heat-insulating layer, and on a cold roof, the waterproofing is attached to the crate. In this case, the waterproofing material is laid first, and only then the roof can be covered with corrugated board.

Note! The waterproofing film is often a special membrane that is not affected by ultraviolet radiation, temperature changes, etc.

Waterproofing performs many tasks that are very important from a technical point of view. The main one is the protection of materials inside the roof from the harmful effects of moisture. If the roof is insulated, then the insulation will rot and lose its properties. And what about the installation of a cold roof? After all, there is no insulation, so there is nothing to rot. Is it then possible to make a roof from corrugated board without waterproofing? Not recommended. Indeed, in addition to insulation, the roof also has other structural elements, such as rafters, crates, etc. If moisture enters, the material will also deteriorate. Wood will rot and metal will rust. Waterproofing is done so that precipitation does not penetrate inside, and the condensate that forms on the inside of the corrugated board is removed through special gaps.

Advice! If, however, you decide to make a cold roof without waterproofing, it is important to ensure good ventilation in the attic. This requires holes in the gables of the wall or in the filing.

To understand how much waterproofing is needed for the roof of a house, we will give a simple example. Without it, the entire roof structure and its elements will serve you half as much. Therefore, if you want to extend its life, its device is necessary. But, before doing waterproofing under corrugated roofing, it is important to choose the material. What should be considered when buying?

material requirements

You should know in advance what you are taking, since the assortment in stores is large enough, you can get confused. The product must meet the following requirements:

• resistance to various influences, both physical and weather;
• the ability to withstand heavy loads without loss of original properties;
• have an elongation at break of at least 10%;
• do not fall under the weight of the liquid, which may accumulate on the surface;
• do not emit harmful substances when heated;
• strength, reliability and stability, material density from 0.04 to 0.06 kg/m2;
• the material must meet standards and be environmentally friendly;
• have a long service life;
• so that it can be easily laid;
• be fireproof (according to GOST 30244–94), water and vapor tight (not less than 0.75 kg/m2 per day).

If the waterproofing meets all these requirements, then you can be completely sure that the roof of the house will be reliably protected and will last you much longer. It is clear that the price of the material will be rather big, but still, the quality is above all. Now, let's look at exactly what materials are used to waterproof a cold roof under corrugated board.

Materials for waterproofing works

To perform waterproofing, two types of materials are most often used - polypropylene films and membranes. If your budget is limited, you can be content with plastic wrap. It has a high hydro and vapor barrier, it protects both the structural elements and the insulation (if any) with the highest quality. The material is made of polyethylene fiber, and to give the film greater strength, it can be additionally reinforced with a special fabric or mesh. There are non-perforated and perforated polyethylene films. Some are intended for vapor barrier, others for waterproofing.

Nevertheless, if you want to have high-quality sheathing that can last 30–50 years, then use membrane materials. This is a modern waterproofing material that meets all the requirements in terms of its technical properties and parameters. The material easily releases steam, which is formed during the convection process, prevents corrosion of the corrugated board, rotting of the crate and rafters, and absorbs noise. The membrane film is made of a synthetic fiber with a microstructure that has a high vapor permeability. There are two types of material - diffusion and superdiffusion. The former have characteristic small holes. But if the material is pressed tightly against the insulation, then they will overlap. Therefore, it is important to provide a ventilated gap. The latter have a higher coefficient of vapor and waterproofing. They can be mounted without ventilation gaps. The price of the material is slightly higher.

Now, let's look at how you can install waterproofing under a cold roof.

Step-by-step instructions for roof sheathing

So, if you bought the material, you can proceed with its installation. The rolled material is laid on top of the crate even before the corrugated board is fixed. There is a special instruction on the package, where you can find out which side to attach the film to. It is necessary to move horizontally in the direction from the ridge to the eaves or from the bottom up in overlapping layers. What kind of overlap is needed depends on the slope. If the roof has a slope of less than 30˚, then overlap at least 15–20 cm, and if the slope is 12–30˚, then it should be 25 cm.

Note! If work is carried out on the waterproofing of a four-pitched roof of a hip type, then the overlap of the film on the ridges must be added by 5 cm.

It is better to connect the edges of the waterproofing with a special adhesive tape so that the joints do not let moisture through. How is the film fixed? With the help of metal brackets directly to the crate.

To ensure high-quality fastening, slats are stuffed with galvanized nails over the film to the crate. So the technology is:

1. The first strip of film is laid, starting the process from the bottom. The roll rolls across the rafters.
2. With the help of a construction stapler, the film is fixed on the roof of the house. Alternatively, you can use galvanized nails with a wide hat.
3. Lay the next strip higher, moving in the direction of the ridge. Do not forget to overlap, in accordance with the slope of the roof.
4. After the two sheets are ready, reinforce them with a counter rail, the width of which is 2–4 cm.
5. So cover the entire area until you reach the ridge.

The same must be done on the other side. When everything is ready, you can start waterproofing the roof ridge of the house from corrugated board. Find out exactly how this can be done in the following video.

As a result, we can say that roof waterproofing is very necessary and must be done both with a warm and cold roof. Then you will significantly extend the life of the entire roof.

• Vapor barrier on the roof under corrugated board
• Colored corrugated roof
• How to make a roof from shingles
• Weathercocks - spiers on the roof

The roofing pro-thinned-out metal sheets - one of the most widespread roofing materials. The popularity of corrugated board is due to the democratic price, ease of installation, low weight. However, along with the obvious advantages, this material has no less noticeable disadvantages. One of them is increased condensation. Under certain conditions, heavy dew falls on steel sheets, both outside and inside. Because of this, at times a little rain literally drizzles under the roof. Wooden structures and insulation have to be protected from condensation. The authors of some articles posted on the Internet argue that a waterproofing layer should be located under the steel sheets and even allow themselves to give advice on the choice of material. However, in fact, waterproofing under corrugated board is not needed, and sometimes it is contraindicated.

• What moisture insulating materials are used in construction
• Waterproofing
• vapor barrier
• Windproofing

What is a roofing film (membrane) Roof over a cold attic Roof over a warm attic Video: why waterproofing is needed What moisture-insulating materials are used in construction

It should be understood: by no means all materials designed to protect against moisture are waterproofing.

Waterproofing

Absolutely waterproof, withstands a fairly large water pressure (continuous flow of water), is very durable and resistant to atmospheric influences, ultraviolet radiation, which allows it to be used outdoors. Waterproofing is arranged during the construction of hydraulic and underground structures, building foundations, flat roofs. Waterproofing materials include bitumen and bitumen-polymer roll insulation, mastics, polymer membranes, special cement-polymer penetrating compounds, and bentonite clay slabs.

When installing a flat roof, the waterproofing layer can simultaneously serve as a roof covering

vapor barrier

As the name suggests, it does not let water vapor through. Both rolled waterproofing materials and polymer membranes cope with this task, but they are inconvenient for use in light wall and roof structures. It is much easier to attach thin and light reinforced polyethylene vapor barrier films to the frame. And yes, they are much cheaper. The vapor barrier is also waterproof and can protect from rain. But it does not have sufficient mechanical strength and resistance to ultraviolet radiation, which does not allow the use of vapor barrier in the open, but only under the protection of roofing, wall cladding.

For the installation of roofs, mainly reinforced polyethylene and polypropylene vapor barrier films are intended. Mounted roof structures in the warm season can be left uncoated for a couple of months, under the protection of vapor barrier alone. It will protect the wood from precipitation. But not longer, the resistance of the film to ultraviolet is limited, it may also not withstand the snow load

Windproofing

Wind and moisture insulation for a roof is able to protect the fibrous insulation from being blown by the wind, retains liquid water to a certain extent, but at the same time freely passes water vapor. Due to such selective properties of moisture transmission, wind-insulating films are also called diffusion membranes. They can be made of polymer fibers (non-woven canvas) or perforated film, there are also combined options.

Due to the presence of pores, the diffusion, wind and moisture protective membrane allows water vapor to pass through. But the size of these pores is so small that water drops that have fallen on the surface do not penetrate the film. The force of surface tension does not allow this to be done. However, if the membrane is moistened for a long time and abundantly, it will sooner or later get wet, “leak”. The windshield is not suitable as a protection against heavy rain; immediately after its installation, the roof should be covered with a roof covering

What is a roofing film (membrane)

It is clear: if the film is roofing, then it is placed directly under the roofing. One of its main functions is to protect the rafter system and insulation (if any) from condensate, which can fall abundantly on profiled metal sheets. Any of the above insulating materials will cope with it: hydro (steam) insulation, diffusion membrane (wind insulation). However, these are not all the tasks that the roofing film is designed to solve. What exactly is required of it and how to choose the right roofing film (membrane) directly depends on the type of roof. Consider two types of roofs: cold attic and warm attic.

Recently, there has been a tendency to call vapor barrier a roofing film, and wind and moisture insulation - a roofing membrane. This is not quite the right use of terms, but it just so happened. The main thing is the difference in the physical properties of these materials.

It is important to know: unfortunately, the Internet is full of confusion on this topic, and ignorant sellers of building materials, illiterate builders also contribute. Often, wind and moisture insulation and vapor barrier are called waterproofing. This is wrong, you need to understand that this is not the same thing, the materials have different physical properties, they are designed for different types of roofs.

Roof over a cold attic

There is no need to insulate the attic roof, but you can ventilate it by arranging holes in the gable walls or filing.

In our case, the fundamental difference between a cold attic and a mansard (combined) roof is how they are ventilated, how excess moisture is removed from wood and insulation

Thus, moisture from the inside of the attic is removed thanks to good internal ventilation, it is only necessary to protect the structures from condensation that forms on the underside of the roofing. Installation of a waterproofing under a professional flooring is possible. Once upon a time they did this, they rolled roofing material under wavy asbestos-cement sheets (slate). Theoretically, you can use old linoleum, plastic sheets, tin and other unnecessary trash that does not let water through. However, a special vapor barrier film will last longer, it is easier to fix it, and it is very inexpensive. You can also use a diffusion membrane, but it doesn’t make much sense: it will cost more, and its properties to pass water vapor will be unclaimed.

The cold attic roof structure must include a vapor barrier film

Important to know: for a cold attic roof, the best roofing film is a vapor barrier, but any type of moisture-wicking material will do.

Roof over warm attic

The mansard roof has to be insulated, and the insulation and wooden structures have the ability to absorb moisture from the air. It will not work to ventilate them from below, from the side of the premises, the air there is more humid than on the street. On the contrary, from the inside, the roof must be protected from moisture by covering the rafters with a vapor barrier film. The only way to prevent the wood and mineral wool from dampening is to ensure their ventilation from the outside, be sure to leave a ventilated air gap of at least 4 cm high between the roofing and the roofing film. (diffusion membrane).

The correct design of the mansard roof and the walls of the frame house. From the inside, the structure must be protected by a vapor barrier, from the outside, wind and moisture protection. But not vice versa!

Important to know: the only suitable version of the roofing film (membrane) for a standard mansard roof construction is a diffusion membrane.

There is a variant of the combined (mansard) roof, in which a vapor-tight hydro or vapor barrier is used as a roofing film. But in this case, it is necessary to ensure effective ventilation of the space both above and below the film, the total height of the ventilation gaps will reach 10 cm. This solution is effective, but complicates the design and is rarely used. Please note that the under-roofing film (4) closer to the overhang is brought out over the steel apron (15), and that one - into the gutter of the drainage system. This should always be done, this is to ensure that condensate drains outside the roof structure.

In conclusion, we say that not only the comfort of living in the house, but also the durability of the building depends on how correctly the roof structure is selected and the materials for its installation are selected. If you do not have sufficient knowledge in the field of construction, do not have the time or desire to delve into the intricacies of modern technologies, the best solution would be to entrust the execution of responsible work to experienced professionals.

Video: why waterproofing is needed

Today, more and more developers are asking this question. The fact is that a cold roofing system allows you to build a residential building for relatively little money, when an insulated roof requires enormous costs both financially and in terms of time and effort. Realizing that such a system is in a sense better, many developers have wondered if a vapor barrier is needed under a cold roof?

Many developers who want to save some money on construction tend to purchase the cheapest materials, but at the same time, so that the quality of the entire building does not suffer much from this. This is possible if primitive two slopes are used as a rafter system, corrugated board as a covering, and the roof is made cold.

The design features of such a roof can be listed on the fingers, since there is no need to lay heat-insulating material, a vapor barrier layer and other components that are often found on insulated roofs. If you all doubt the savings, then it is safe to say that the cold version will cost 50-60% less than the insulated design. In addition, the work can be carried out independently, therefore, the savings will increase even more.

A cold roof pie, in most cases, includes the following products:

• rafter legs
• waterproofing material
• Control lathing
• crate
• Profiled metal sheet

Do I need waterproofing under the metal roof of a cold roof?

It is worth noting that all metal surfaces have one similar feature, they collect condensate. Waterproofing, which is part of the roofing pie with a cold roof, will correct this problem and protect the room from incoming moisture, both from the outside and from the inside. Many developers, when building an insulated roof, advise their friends not to lay a vapor barrier layer if they are building a building with a cold type of roof. They think that the cold will remove the condensation that is visible on metal products, but they are greatly mistaken.

Condensation occurs due to the temperature difference between the roof space and the external environment. Naturally, when the attic is not heated and not insulated with anything, the difference will be small, but still it is sufficient to provoke the release of moisture from the air. As you can see, condensate will form regardless of the type of roof, therefore, the question posed at the beginning of the paragraph can be answered unequivocally: yes, it is needed.

An example is outbuildings, the owners of which do not care much about their service life. In such buildings, the roofing cake is the most primitive and even violates building codes and regulations. Most often, a roofing cake consists of rafters, discharged lathing and roofing. All layers of vapor barrier and waterproofing were simply thrown out. Despite this fact, this building can stand for a significantly long period, or vice versa, fall apart after a couple of years. Here you are already lucky, but why take risks if you can do everything in a quality way?

Risks cannot be allowed on residential buildings, as someone's life may depend on it. I am not exaggerating, because if the condensate affects the rafter system and other roof elements for a long time, it will simply destroy them, which can lead to the fall of the entire roofing pie.

IMPORTANT: If at the beginning of construction you decided to build a cold roof, but later on after a certain period you will insulate it, then it is best to lay a microperforated film as a waterproofing product. Its properties are practically no different, but according to the price tag, it is much lower than membranes.

Waterproofing and ventilation of a cold roof

If you are laying a micro-perforated product, then such a layer will block moisture from the outside, but water vapor can pass through this area without problems. It can be said that the installation of vapor barrier products on roof slopes is not necessary in this case. After the steam penetrates inside, it is between the waterproofing material and the metal coating, from where it is removed by natural ventilation.

IMPORTANT: When a dense waterproofing film is used that retains water vapor, this leads to a significant increase in air humidity and, as a rule, dampness in the room.

With increased air humidity, condensation processes begin, so moisture accumulates on the reverse side of the film and penetrates into all roofing materials. In connection with this fact, it is not recommended to use materials such as polyethylene and polypropylene, roofing felt, and glassine for the construction of a cold roof.

The ventilation system of cold roofs is quite simple. To create it, gaps are left, which, as a rule, are located along the cornice overhang. Air masses pass through them, collect all the humidified air and remove it through a cold triangle located in the ridge part of the roof.

The counter grille is a design to provide additional ventilation. Most often it can be found on complex roofing systems, where products with a high degree of waterproofing are used as a coating, for example, metal, shingles and others. The gap that is created by installing a counter-batten allows fresh air to dry the roofing pie from both sides, so structures with such a pie last much longer than the others.

Cold roof. Do buildings need waterproofing?

First of all, it should be noted that outbuildings differ significantly from residential buildings both in their structure and volume. The vast majority of developers are trying to save on the construction of secondary structures, so the issue of waterproofing is more relevant than ever. Before answering the question posed, let's deal with the coverage. To date, corrugated board is one of the cheapest materials, so I will talk about buildings covered with it.

Manufacturers from different countries are striving to produce such products so that the whole world begins to use it. If you are a fan of corrugated board, then today, such material is a sheet of metal with an anti-condensation coating.

In its appearance, it practically does not differ from its counterparts. A synthetic composition is applied from the inside, it looks like felt. Due to the large number of pores, this material is able to retain up to 1 liter of water per square meter. After the surface has been saturated with moisture, ventilation comes into play and if it is done in accordance with all the rules and regulations, then the drying process will not take much time.

Thanks to the laying of such a “cunning” coating, the need for laying a vapor barrier and waterproofing layer is removed, but it should be understood that the weight of such a coating will vary depending on weather conditions. When making the necessary calculations, it is very important to take into account these parameters and use them in the calculations. It is worth noting that the finished roof will be much cheaper, because it will not have almost half the roofing cake.

Installation of waterproofing for a cold roof

So, based on the information obtained above, you realized that the waterproofing material is laid regardless of the type of roof and the functional purpose of the building. However, if you want to save money, you can use roofing with an anti-condensation layer, but not all people like metal coatings, so I will now tell you the general principle of laying waterproofing.

• First of all, an inexperienced roofer must repeat the safety precautions and the principle of working at height. After that, he puts on a special uniform, which should include the following: personal protective equipment, good shoes with non-slip soles and a mounting belt.
• After the rafter legs are fixed in place, you can start laying the vapor barrier layer. It is attached to the rafters with a construction stapler and pressed against the crate. With a small slope, the strips of material are placed across the slope, and along the strongly sloped slopes. To improve the quality of laying this layer, the joints are smeared with bitumen or glued with double tape.

IMPORTANT: Before installing the crate, it is very important to treat its elements with special protective solutions that will increase the degree of ignition of the wood and protect it from decay.

• Next, the counter-lattice is laid. It creates the necessary air gap, thanks to which moisture will be removed from the roofing cake.
• A waterproofing material is laid on top of the konroblattice.
• After that, proceed to the installation of sheets of corrugated board.

Most developers strive to cover as much length as possible with one strip of profiled sheet. This is justified by the fact that in this way fewer joints are obtained, therefore, the waterproofing qualities of the entire roof increase significantly. You can do all the work yourself, but to increase efficiency it is better to invite 1-2 partners.

Roof construction is a crucial stage of construction work, which needs special attention. As soon as it comes down to it, the following questions immediately arise: what kind of roof to make, what is its design, what to use as a flooring, insulate it or make it cold? These questions are up to you. We would like to draw your attention to the fact that there are plenty of materials for roof sheathing. All of them have their pros and cons. One of these popular materials is corrugated board. It has a lot of advantages, which is why it is so appreciated by builders. What about vapor barrier? Is it necessary if you use corrugated board? What materials are best suited for this purpose?

Let's take a closer look at the answers to these and other questions.

A bit about the cold roof

It is known that when constructing a roof, work is carried out to insulate it. This is done so that heat does not leave the building, and cold does not get inside. It is especially important to make insulation when the roof is an attic. But, there is another concept, the so-called "cold roof". At the same time, insulation work is not carried out, it is enough to make a crate and lay the material. The use of this type is advisable if the roof does not need to be insulated. The advantage of a cold roof is high efficiency, ease of operation and high speed of construction.

When is a cold roof suitable? For example, in a country or private house there is an attic that you will not use as an attic. Or, you need to close off a building that is not intended for permanent residence. In this case, it is rational to make the roof cold. At the same time, it is important to insulate the ceiling inside the building itself, and block everything using corrugated board. But the question arises: what to say about the vapor barrier, is it needed under the corrugated cold roof? Let's first understand what vapor barrier is generally needed for.

It performs the most important role - it protects the heat-insulating material from moisture penetration. After all, warm and humid air will accumulate in the upper part and on the roof. If the vapor barrier is not done correctly, it will lead to early repair of the roof and reduce the life of the building. Yes, and wooden structures under the influence of moisture will rot. But, there is one nuance here. All this is rational when the attic or attic is insulated, as for the cold roof, everything is not so simple here. Is a vapor barrier necessary in this case? After all, we learned that its main goal is to protect the insulation layer. It is necessary, and there are reasons for that.

Although the room will be well ventilated, it will still suffer from precipitation. Profiled 100% cannot exclude the fact that moisture will penetrate under the roof. Snowfall, heavy rain along with the wind can do their job, and the liquid will get inside. This is fraught with the fact that the metal elements inside will rust and fail. The same applies to wooden products (built, crate, etc.), which will rot and deform.

So, we learned that vapor barrier under corrugated board is still needed, even with a cold roof. But what to do? Let's look at the main vapor barrier materials that can be used under corrugated board.

Glassine as a vapor barrier

All vapor barrier materials are made in the form of films. The material consists of several layers that perform their role or task. One such material is glassine. This, one might say, is a classic for both warm and cold roofs. This material has been used for decades. It is quite reliable and does its job well. In addition, such a vapor barrier will cost you the cheapest. However, it is better not to use material for residential buildings.

If there is a dwelling immediately under the roof, then it will suffer from the properties of glassine. We are talking about the fact that when the material is heated, it emits a not very pleasant aroma. For life, it is not dangerous, just like a pair of roofing material, but for permanent residence it is not quite an ideal option. Moreover, corrugated board is used as a roofing material, which, like all metals, will get very hot under the influence of the sun, especially in summer.

Another disadvantage of glassine is its heavy weight and narrow rolls, so installation will be quite problematic and inconvenient. Summing up, we can note all the pros and cons of the material.

• strength;
• reliability;
• flexibility;
• durability;
• low cost.

• when heated, an unpleasant odor appears;
• has a lot of weight;
• installation complexity.

We can conclude: for a living space, the material is not the best option, but it may fit for a summer residence with a non-residential attic or a bath.

Polyethylene film

Ordinary household polyethylene is also suitable for vapor barrier roofs made of corrugated board. It is quite famous and has been used for many years. Polyethylene is able to perfectly retain moisture, water vapor, protecting and isolating the structural elements of the roof from the inside. One of its main advantages is that it is cheap, so you will need less money to install a roof. Polyethylene is able to provide good vapor barrier, no worse than specialized films and various membranes.

But, these are all the advantages of this material. Cheapness is fraught with complexity and impracticality. As you know, polyethylene is not the strongest material, so during installation it can be easily damaged. To avoid this, experts recommend using a thicker whip. This leads to the fact that it will be difficult to fix it without outside help. And yet, such a weight becomes an obstacle in that it will be difficult to attach it to corrugated board in standard ways.

When you are limited in funds, then polyethylene is quite suitable for a vapor barrier layer. It is attached with a construction stapler to the crate inside. The step of fixing the film depends on its thickness. Usually it is about 1–1.5 m. To prevent condensate from getting inside, it is important to seal all places with punctures and joints with construction tape.

Note! In order for the vapor barrier layer to be reliable and fully perform its functions, it is better to fix it in two layers.

Now let's summarize and understand the advantages and disadvantages of polyethylene.

• low cost;
• very low permeability.

• insufficient strength;
• short service life;
• big weight;
• complexity of installation;
• a lot of condensate forms, it drains and does not linger on the surface.

Polyethylene is not the best option, but in the absence of funds, you can resort to it.

Reinforced polyethylene vapor barrier film

Roof vapor barrier films, as already mentioned, consist of several layers. It is based on polyethylene, which is reinforced with auxiliary materials. The most budgetary of them is reinforced film. It consists of several layers of polyethylene film, and is also necessarily supplemented with an additional reinforcing mesh made of polypropylene or fabric. Thanks to this structure, the material is strong, it will be difficult to tear it with your own hands. In addition, an accidentally dropped tool will not damage it either, which is quite practical.

In addition to everything, such a film has a greater rigidity than conventional polyethylene. But, despite the large number of layers, its weight is not so great. Therefore, it will be easy for you to install the material on the roof of corrugated board. And you can fix and connect the film with special self-adhesive tapes.

• high strength;
• light weight;
• several layers provide reliability and durability;
• relatively low price;
• ease of installation;
• has low vapor permeability.

• as in the case of ordinary polyethylene, a lot of condensate forms, it drains and does not linger on the surface.

If you need to make a good vapor barrier, but you do not have huge funds, then reinforced film is the best solution. This is an ideal option in terms of price-quality ratio for your residential building.

Polypropylene film

It is made exactly according to the same scheme as multilayer reinforced polyethylene. Polypropylene is used to increase the strength of the film. Its installation is also simple. A feature of polypropylene films is the presence of an additional relief layer. What is it for? A lot of condensate forms on the foam, which negatively affects the structural elements.

So that moisture does not harm the insulation (if any) or structural elements, an additional anti-condensation layer is applied on the polypropylene film, which consists of a mixture of cellulose and viscose. The layer easily absorbs condensate, preventing the formation of drops of condensate. This layer is rough, and during installation it should be placed towards the room, with the smooth side outward.

Advice! Before starting work, read the instructions from the manufacturer.

• light weight;
• high strength;
• reliability and practicality;
• ease of installation;
• low vapor permeability.

• material without an anti-condensation coating spoils the insulation and structural elements.

Vapor barrier film with foil

This is one of the types of previous films. But, the material not only has an additional reinforcing layer, but is also equipped with an aluminum layer that reflects heat. What does it give? This layer reflects infrared rays, preventing them from leaving the house. This creates a kind of "thermos effect". Foil film is intended for baths and greenhouses, but it began to be used as a vapor barrier for a roof made of corrugated board and other materials. It is highly efficient, reducing heat loss through the roof by 10–15%. This allows you to significantly save energy that is spent on heating. For example, the use of Izospan under corrugated board increases the temperature in the room by only 2˚, while the costs are the same.

Note! The reflective effect is possible only in the air, so when mounting a film with foil, it is important to make a gap of 4–5 cm.

• light weight;
• high strength and reliability;
• durability;
• low vapor permeability;
• not harmful to humans;
• reflects infrared radiation, retaining heat.

• high price.

Foil film is one of the best, but as they say, you have to pay for quality. If you have enough funds, then it is better to make a vapor barrier under corrugated roofing from it. However, it is up to you which choice to make.

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The roof plays a key role in protecting the home from rain and other adverse effects. To preserve heat and maintain a comfortable microclimate, a number of materials are used. Together they make up a roofing pie. So that the heated air does not leave the room during the cold season, heat-insulating materials are used under the corrugated board. Maintain a low degree of thermal conductivity will allow vapor barrier.

Why do you need a vapor barrier under corrugated board

Vapor barrier (as well as waterproofing) is arranged under corrugated board to achieve two goals:

1. Protect the thermal insulation layer from moisture. When wet, its thermal conductivity increases. Also, the penetration of liquid leads to the gradual destruction of the insulation.
2. Prevent the accumulation of moisture in the thermal insulation layer and direct the water vapor to the outside.

Water vapor is always present in the air of a residential building. Partially they leave through the ventilation system, a certain proportion of them remains in the room. Warm air, saturated with vapor, rises up to the ceiling. There it cools, while moisture is given to roofing materials.

Due to its porous structure, the insulation absorbs moisture. As it gets wet, its thermal conductivity increases, and it retains heat in the room worse. To prevent the penetration of moisture into the pores of the insulation, use a vapor barrier film under the corrugated board. It is laid from the side of the room and is needed to protect the insulation and other structural elements from water vapor.

What to consider when choosing a vapor barrier

Many types of vapor barrier films for the roof are available in hardware stores - both cold and attic. To make the right choice, you need to be aware of the following factors:

• price;
• efficiency;
• expediency.

Before purchasing materials for corrugated board, you need to decide on the amount allocated for construction. If the price of the material is decisive, you need to choose from economical materials.

The second point is efficiency. Vapor barrier films have different performance characteristics, which are important to familiarize yourself with before buying.

It is worth choosing the material appropriate to the characteristics of the room. For a residential heated house, a foil film would be the best option, while for a cold roof of a country house, inexpensive glassine is quite sufficient. If the roof of a rarely visited mansion is being built, which is not heated for a long time, you need a simple vapor barrier made of polyethylene or polypropylene.

What materials are used for vapor barrier

The vapor barrier layer for corrugated board or any other roofing material is made in the form of a film. The following are the most common types of it, which are presented in hardware stores.

Polyethylene film. Household polyethylene has long been used as a vapor barrier material. He does not let the steam rising from the living quarters. Polyethylene is a cheap material compared to reinforced films or membranes. Its significant disadvantage is the lack of strength. It is easy to damage the film during installation. For reliable vapor barrier, it is laid in two layers and fixed on the inner crate with a construction stapler. Mounting step - from one to one and a half meters. If the film is still damaged, a patch is needed. The puncture site should be covered with construction tape. Tape must be fixed and joints. Given the above, plastic film is quite acceptable and cheap, but at the same time not the best option for vapor barrier.

Reinforced polyethylene film. Also inexpensive, but high-quality material for vapor barrier under corrugated board. It is made of several layers of polyethylene and reinforced with a polypropylene mesh. Such a film, with a low weight, has sufficient strength, it is more difficult to damage it during installation. Due to the reinforcing mesh, the material has greater rigidity. The film can be fixed with a special tape. This is the best combination of low price and good quality material, suitable for vapor barrier of residential buildings.

Glassine. This material has long been used for vapor barrier. It reliably retains moisture, is durable and has a long service life, but has a rather large weight. Although glassine is a cheap material, it is not recommended for living spaces. When heated, an unpleasant odor emanates from it, and under the corrugated board its temperature will often rise, especially in the warm season. Therefore, glassine should be used only for a bath or a cold roof of a non-residential attic. It is more convenient to use it as a waterproofing - then it will need to be laid on top of the crate.

Polypropylene film. Durable material for vapor barrier under corrugated board. It is made similarly to a multilayer polyethylene film. The two main differences are the use of polypropylene and the presence of a relief layer. The fact is that condensate accumulates on smooth plastic films, which collects in drops and periodically drips onto the floor. Rough anti-condensation coating is made on the basis of viscose and cellulose. It absorbs moisture and prevents it from collecting in drops. Subsequently, with a decrease in air humidity, the collected condensate evaporates. As a rule, a polypropylene film has an anti-condensate surface down towards the room. To clarify the installation procedure, you need to refer to the instructions from the manufacturer. This type of vapor barrier film is one of the best options for arranging a roof for corrugated board.

foil film. In fact, it is a kind of polyethylene or polypropylene film. In addition to the reinforcing mesh, it has a thin aluminum layer. It reflects infrared rays and helps keep the heat in the house. Although at first this material was used in the arrangement of the bath, it was also used for vapor barrier in residential buildings. After laying the foil film, heat losses are reduced by 10 percent or more. Its price is higher than other types of vapor barrier films, but it justifies itself by saving on heating costs. The foil film is laid with an aluminum layer towards the room. Be sure to make a gap between the material and the wall finish: you need a gap of about 5 cm. A small distance should also be left to the insulation. The film is fixed with self-adhesive tape, all joints are closed with aluminum tape. Then the vapor barrier layer will be airtight.

Features of a cold roof

Although the space directly under the cold roof is not heated, the temperature inside will still be different from the temperature outside. Therefore, condensation will begin to appear on the underside of the corrugated board. In view of this, a waterproofing layer is needed to prevent moisture from entering the wooden rafters and other structural elements of a cold roof.

Important! The waterproofing layer is laid on top of the rafters. Then the material is fixed with a counter-lattice, followed by the crate and the profiled sheet itself.

If the waterproofing layer does not prevent steam from escaping to the outside, a vapor barrier for cold roof slopes is not required. Water vapor, having risen, will penetrate through the film under the corrugated board, and there it will be dried under the action of air currents.

It is important to choose a material for waterproofing a cold roof that will not trap steam. In this case, polyethylene, polypropylene, roofing material or glassine will not work. For a cold roof, a non-woven vapor permeable membrane is recommended.

As you can see, vapor barrier is arranged only for a warm roof in order to protect the insulation from water vapor. There are a few tips to help you get the job done right.

1. It is better to place panels of vapor barrier material with an overlap of about 15 cm.
2. It is necessary to select a suitable connecting tape for the selected film or membrane.
3. Planks for vapor barrier can be made of both wood and metal. They must be small.

When arranging a warm roof, vapor barrier is an important component of the roofing pie. The material is chosen on the basis of financial and practical considerations, as well as guided by its feasibility.

The so-called roofing "pie" consists of many layers. Each owner of a private house decides for himself what should be present in it and what will be a waste of money. For example, roof insulation may not be installed if the room is not used as. What about waterproofing? Is it worth installing it, especially if the roof is covered with such reliable material as corrugated board? And if so, how is it done? This will be discussed in the article.

Is this extra layer needed?

Before proceeding to consider how the roof is waterproofed from corrugated board, it is worth understanding whether it is needed at all. If you are going to build a cold roof, in the attic space of which there will be no living space, then the roofing "pie" can be greatly simplified. In this regard, many people have a question, why spend extra money on installing waterproofing under corrugated board.

But such an opinion is erroneous. This extra protective layer is still needed. There are several factors that confirm the need for waterproofing even a cold roof. We list the main ones:

1. Precipitation. No matter how well the roof is made and the profiled sheet is securely laid, there is no guarantee that moisture will not get under the cover in case of heavy rain or snow combined with wind. Water will always find even a small gap through which it can seep.
2. Wear of attachment points. Decking during operation is exposed to temperatures and other factors. As a result, the attachment points may loosen. As a result, water will begin to seep under the roof of the house.
3. Condensation is another reason to make waterproofing under a profiled sheet. Due to the fact that the roofing is constantly exposed to temperature changes, moisture droplets can form under it. If water gets on the truss system, the tree will begin to rot and the entire roof structure of your house will quickly fail.

As you can see, it is better to waterproof the roof from corrugated board. Of course, you will have to spend money, time and effort, but with such additional protection, your roof will last much longer. In this case, small damage to the coating of corrugated board will not cause you problems.


What should be waterproofing

The additional layer in question is part of the roofing "pie". No matter how reliable the corrugated board is, a lot depends on this multilayer structure. Therefore, special requirements are imposed on waterproofing, namely:

• the selected material must have a high density. It is best that this indicator be at least 0.04 kg per square meter. In this case, waterproofing under corrugated board will be able to withstand high water pressure;
• ability to withstand a wide range of temperatures. Waterproofing a cold roof made of corrugated board should easily withstand cooling down to -50 and heating up to +100 degrees. The selected material should not change much in size from heating and cooling. Plus, there should be no damage from frequent (temperature during the day and night can be very different) drops;
• fire resistance. The corrugated board itself does not burn. This is one of its advantages. But other roof components, such as the truss system, are made of material that can catch fire. Therefore, it is desirable to choose a material for waterproofing under corrugated board that is safer;
• Another condition is resistance to ultraviolet radiation. Of course, the corrugated board will cover everything that is under it from the sun. But small gaps may still be present. Therefore, the material chosen for corrugated roof waterproofing should easily withstand exposure to direct sunlight.

There is also a requirement for vapor permeability. But it is more related to the option when a residential attic will be made from the attic. For the option of a cold roof made of corrugated board, this parameter is not so important. In this case, there will be little water vapor in the attic, so the waterproofing layer may not let them through.

What material is better to use

We found out whether waterproofing is needed under the corrugated roof of a cold roof, now it’s worth finding out what materials are suitable for this. Modern industry produces a wide range of similar products. It is quite easy to choose an option that will satisfy you both in terms of its qualities and cost.

Among the most popular materials used for waterproofing a roof made of corrugated board, the following can be distinguished:

If you have enough funds, then it is better to choose the last of the listed options for waterproofing the roof under the profiled sheet. But no matter what material you choose, the most important thing is installation. If the waterproofing under the corrugated board is done correctly, then the house will be reliably protected.

How the work is carried out

And how to properly waterproof the roof of a house with corrugated board? What are the nuances of this work? Here you should take advice from experts. The work on waterproofing under corrugated board is carried out as follows:

• the selected material must be laid on. You can cover both from top to bottom (from the ridge to the eaves), and across the roof. Experts recommend using the second option. In this case, waterproofing will be more reliable. Although the first laying option is much easier to perform;
  
• for any type of laying, the layers of waterproofing are overlapped. It will depend on . The steeper the roof, the less overlap is made. Experts recommend that at an angle of inclination of more than 30 degrees, go with the top layer to the lower minimum of 15-20 centimeters. If the roof is flatter, then the overlap is at least 25 centimeters. Another separate recommendation concerns the hip version of the roof. Here the overlap must be increased by five centimeters;
  
• the material itself can be fastened to the crate with brackets. It is better to choose another option. Waterproofing is fixed with rails and nails. It turns out a counter-lattice. In this case, a small space is formed between the corrugated board and the film. It will serve for underlayment. This will ensure less condensation on the corrugated board;
• all joints between layers of waterproofing must be sealed. To do this, it is convenient to use a simple or construction adhesive tape;
• it is very important to correctly treat the tension of the waterproofing, it should not be at all. The film or membrane should lie freely, with a slight sag of two centimeters. Only in this case will this additional protective layer work effectively;
• if a film or membrane is chosen for waterproofing the roof under the corrugated board, then all installation work should be done with caution. These materials can be easily torn, which means that the protection will be unreliable.