Roof underlay. The use of corrugated board as a roofing material

In order for the roof to be airtight and to serve flawlessly for many years, it is necessary to choose the right roof covering. But for greater reliability, it is necessary to adhere to the technology of laying the material and the correct compilation of the roofing cake, the layers of which mutually complement each other, thereby increasing the service life of the entire roof. One of the components of a quality coating is waterproofing.

Appointment of a waterproofing layer for corrugated board

An important part of the roofing cake on a warm or cold roof made of profiled sheet is the waterproofing layer, which is attached with a construction stapler directly to the rafters. For waterproofing the roof of the house under the corrugated board, a special material is used that does not allow water to pass through, which ensures reliable protection of the wooden truss structure from moisture.

As part of a corrugated roof, waterproofing is designed to perform the following tasks:

• Ensuring the protection of the inner side of the corrugated board from the formation of foci of corrosion. In contrast to the front surface, the lower part of the material has only a paint-and-lacquer coating, which is the weakest point. Wetting damaged areas leads to inevitable corrosion.
• Preventing the insulation from getting wet. Wet heat-insulating material loses some of its performance characteristics, and they are not restored even when the material dries completely. The waterproofing laid on top of the insulation serves as an excellent protection against moisture penetration. It is worth noting that this function is relevant only for a roof made in a warm version, since a cold roof does not need insulation.
• Protection against wetting of the roof truss system. The main material for the manufacture of the roof frame is wood, on which rot can form from constant contact with water. Moreover, this phenomenon is observed even in elements treated with antiseptic agents.

Roofers recommend installing waterproofing on both cold and warm roofs. Ignoring this rule leads to the fact that the condensation formed due to the temperature difference from the outside and inside of the roof, contributes to a reduction in the service life of the roofing material.

Quality waterproofing material for the roof of the house

Waterproofing under the corrugated board on the roof is exposed to various aggressive factors, therefore, special requirements are imposed on the quality of this material. The main features showing the high quality of the material are vapor permeability, a stable attitude to various temperatures and high humidity.

When choosing a waterproofing material for a roof under a corrugated board, you should carefully study the following characteristics:

• Density indicator. High-quality waterproofing, capable of retaining a certain amount of water in the event of a leak and receiving minimal damage during installation, has a density of 0.04 kg / m 2.
• Vapor permeability coefficient. Efficient removal of warm air, in which there is a large accumulation of water vapor, provides a material with a vapor permeability of more than 0.75 kg / m 2.
• Waterproof. High quality waterproofing is capable of withstanding a water mass pressure of 10 MPa for 10 minutes.
• Possible operating temperature limits. High-quality roof waterproofing for corrugated board can be flawlessly operated at temperatures from -73 to +100 0 С.
• Resistant to fire. One of the properties of corrugated board is high thermal conductivity, therefore, the waterproofing of such a roof is best done with non-combustible materials.
• Relation to ultraviolet radiation. Despite the fact that the waterproofing is covered with a topcoat, exposure to sunlight can still damage this layer. A high-quality waterproofing material must flawlessly withstand exposure to ultraviolet rays for more than 4 months.

Rules for choosing waterproofing for the roof

The materials used for waterproofing under the profiled sheet are presented on the construction market in a large assortment. They come in a variety of costs, weights, and strengths. However, the first material that comes across cannot be used for the metal profile. Before laying the corrugated board on the roof with your own hands, you must choose the right waterproofing material. It must have good vapor permeability, appropriate density and elasticity, and moisture-proof.

Therefore, waterproofing materials are divided into three categories:

• Film waterproofing under the corrugated board is represented by thin polyethylene films, which are of low weight and high moisture-protective properties. The cost of such materials is insignificant, but they are easily damaged during installation or operation.
• The diffuse membrane is made by analogy with a film material, but made of more durable polymers. In addition, the structure of the membrane, consisting of microscopic holes, provides good vapor permeability to the material.
• Bitumen based roll waterproofing is widely used for cold roofs. This material is bitumen-impregnated cardboard or fiberglass. Such waterproofing is notable for its low cost, but does not allow the roof to "breathe" at all.

Features of waterproofing roofing cake

Waterproofing a cold and warm roof has its own characteristics:

• Cold roofing involves the use of materials with high strength characteristics to withstand high water pressure in the event of a leak. The recommended materials in this case are roofing felt, roofing felt, glass mat.
• When installing a warm roof, it is better to use a waterproofing material under the corrugated board on the roof with good vapor permeability.

The metal is absolutely waterproof, but this does not mean that waterproofing the roof of the house for corrugated board is not needed. Even when the sealing of the roof joints and attachment points is done correctly, and the roof does not leak in these places, there is still condensation on the inner surface of the metal sheet. And it appears almost daily due to daily changes in temperature, atmospheric pressure and humidity. And although the waterproofing does not protect the seamy side of the profiled sheet from moisture (according to some authors), it takes it outside the roof, does not allow the insulation and elements of the roof supporting structure to get wet. From the article you will learn about materials for waterproofing, the rules for their selection and use.

The abundance of condensation is a characteristic sign of a roof made of profiled sheet Source decorexpro.com

Waterproofing device for different types of roofs

Decking as a roof covering is used in two types of pitched roofs:

uninsulated;

insulated.

You can also talk about flat roofs, but there the profiled steel sheet is used as an overlap on which the entire roofing cake is laid. And in this case, according to the scheme of such a roof, bitumen roll materials and mastics (coated or sprayed), which are on top of the corrugated board, and not under it, are responsible for waterproofing. And in order to move the "dew point" from the inner surface of the sheet, such a roof is insulated from the outside, protecting the insulation from vapors from the side of the room with a vapor barrier, which is spread over the ceiling.

Waterproofing is supplied and combined into one "whole" with the drainage system Source projject.ru

In pitched roofs, multilayer polymer films are used as waterproofing, which have almost completely displaced roofing material and its more modern analogues (rubemast, stekloizol and others) from this sphere.

In the "upper" part, the insulation scheme for corrugated roofing is the same:

Rafter legs.

Waterproofing.

Counter rail(distance rail).

Lathing.

Corrugated board.

Important! In this scheme, a special place is given to the distance rail. It "sets" the air gap in the under-roof space, due to which vapors are eroded out of the roof, be it evaporating condensate or excess moisture from the insulation.

Standard ventilation scheme for the under-roof space, cold attic and premises Source erp-mta.ru

But the features of the installation of the "lower" part of the scheme, as well as the choice of materials for corrugated boarding on the roof, depends on the nature of the operation of the attic and even the angle of inclination of the slope. And first of all it concerns the vapor-permeable properties of waterproofing.

On our website you can find contacts of construction companies that offer the service of designing and carrying out roofing works of any complexity. You can communicate directly with representatives by visiting the Low-Rise Country exhibition of houses.

Materials and features of waterproofing installation

There are two main types of roof waterproofing films for corrugated boarding:

with limited vapor permeability;

waterproof but with a high vapor diffusion capacity.

Manufacturers refer to the first type as vapor barrier, the second to membranes.

The breathable membrane has microperforation Source stroymoda-nk.ru

The choice of the type depends on the presence or absence of insulation.

Uninsulated roofs

A metal profiled roof (profiled sheet and metal tile) in an uninsulated roof behaves completely differently than slate, ondulin or soft tiles. Waterproofing may not be laid under these materials at all - condensation does not form on their inner surface. Although the manufacturer of ondulin advises to lay the Ondutis film to improve the tightness of the roof (and this is understandable - he is an interested person).

As a waterproofing of a cold roof made of corrugated board, films with limited vapor permeability are used, that is, vapor barrier. This allows you to "cut off" most of the moist air in the attic from contact with the roof.

For waterproofing a profiled sheet in a cold roof, it is better to choose a vapor barrier with an anti-condensation surface Source housetopgid.ru

Note! The cold roof attic must be well ventilated with its own natural ventilation system.

Installation of waterproofing looks like this:

Laying begins from below horizontal stripes. The film should sag a little between the rafters, but no more than 2 cm. The sagging is necessary for collecting and "transporting" condensate to the cornice.

Preliminary fixation film passes with a stapler.

If necessary build up strip in length, the next segment is overlapped. The overlap of the strips is more than 15 cm. The joint should lie on the rafter leg, and additionally it is sealed with a tape with a double-sided self-adhesive strip.

The tape is also used to glue joints with adjacent surfaces, chimneys and pipes of the ventilation system. Source hobbymaniya.ru

Bottom edge of the first strip get on a drip drainage system and secure with tape.

The next strip from the cornice rolled out with an overlap relative to the previous one. The size of the overlap is more than 15 cm. The joint is additionally glued with tape.

Finally consolidate the film using a rail, which is nailed along the outer end of the rafter leg. The rail must be treated with an antiseptic. On the side of the rail facing the waterproofing, a sealing tape is glued.

On reiki mount the crate for corrugated board. The step of the battens depends on the slope of the roof and the type of profile.

This is an algorithm of work for one slope - for example, for waterproofing the roof of a balcony under corrugated board.

For gable and hip roofs, there is also a ridge zone, where the laying of the waterproofing of each slope is finished before reaching it 5-10 cm. This gap is necessary for ventilation of the entire attic and the gap between the roof and waterproofing.

The crevice in the ridge is then closed with an additional element Source rabotayouth.ru

For multi-gable roofs, valleys are waterproofed separately:

film roll out in the direction of the valley axis;

fix a film with a stapler to the valley boards and adjacent rafter legs (but not further than 30 cm);

the edge of the waterproofing of the right slope is turned on for the far left

the edge of the waterproofing of the left slope is turned on for the far right a 15 cm valley board (cut off the excess);

the edges glued connecting tape and secured to the rafter legs.

This is how the valley waterproofing scheme looks like Source krysha-expert.ru

Important! Laying of the vapor barrier film is carried out with the smooth side to the profiled sheet. The rough side (with anti-condensation properties) is turned towards the attic.

If the cold attic is planned to be later converted into an attic, then a membrane is chosen for waterproofing.

Insulated roofs

For waterproofing insulated roofs, diffusion or superdiffusion membranes are used.

Diffusion membranes have "average" vapor permeability. And they may not "cope" with the load of weathering excess moisture from the insulation. Especially if it is a metal roof. And with small slopes of the roof, due to the small difference in height and pressure between the eaves and the ridge, the ventilation intensity may not be high enough to weather the condensate. Therefore, for a metal roof, a laying scheme with two gaps under the roof is recommended:

Insulation stack between the rafter legs so that a gap of 4-5 cm remains to their end.The second option is that the insulation is laid to the entire height of the rafters, and a distance rail 4-5 cm thick is stuffed on them.

Over the distance rail roll out membrane with a slight sagging (no more than 2 cm), and fastened with a stapler.

The scheme of waterproofing a metal roof with two ventilated gaps Source domaleto.ru

On the spacer rail over the membrane fix the counter rail with glued sealing tape.

The first gap is needed for ventilation of the insulation, the second - for ventilation of the “wrong side” of the roofing (condensation weathering).

Important! A scheme with waterproofing with a "normal" diffusion membrane and two ventilated gaps is recommended for roofs with a slope of more than 35 °.

Superdiffusion membranes are laid in a different way - without a gap on the side of the insulation. They can be used on all pitched roofs covered with corrugated board with a slope of 5.5 °. In addition to the absence of a distance rail, sagging of the membrane and the presence of one ventilated gap, the rest of the installation of waterproofing is similar to the previous options.

Two schemes of a mansard roof: with full insulation and waterproofing up to the ridge, with its own small "cold" attic Source gid-str.ru

Main manufacturers and prices

“Intraspecific” choice often depends on cost. And the price of waterproofing for corrugated roofing is influenced by the density of materials, the number of layers, strength to ultimate loads in the transverse and longitudinal direction, water and vapor permeability.

The most "simple" are waterproofing films. They consist of two, three or four layers. The more layers, the more expensive the material.

Diffusion membranes, in contrast to vapor barrier films, have microperforation. "Holes" are capable of letting in steam, but retain water due to the surface tension of the water. If we talk about the differences between "ordinary" membranes from superdiffusion, then the difference lies in the number of holes per unit area and their diameter - the smaller the hole diameter, the greater the "height of the water column", the more holes, the higher the vapor permeability. Naturally, superdiffusion membranes are more expensive than conventional membranes.

The domestic brand Izospan has one of the largest assortments of films and membranes Source erp-mta.ru

The ultimate load strength depends on the density of the waterproofing and the presence of a reinforced polypropylene mesh layer. Such materials have three or four layers. In addition, they may include as one of the layers:

for vapor barriers and membranes - fire retardant fillers(for roofs with increased fire safety requirements);

for membranes - an additional anti-condensation layer or thread soot-soaked(with increased ability to retain and drain condensate).

Video description

For the choice of diffusion membranes, see the following video:

Below is a list of some of the main brands of roof waterproofing for corrugated board that can be bought on the domestic market:

Steam and waterproofing for cold roofs. Izospan D (two-layer, unreinforced) - from 1500 rubles. per roll 70 m 2. Izospan DM (three-layer, reinforced, with anti-condensation surface) - from 3000 rubles. per roll. Ondutis RS (reinforced) - from 2190 rubles. per roll 75 m 2. Yutafol H 110 Standard - from 2470 rubles. per roll 75 m 2. Yutakon (four layers, reinforced, with an anti-condensate surface) - from 4500 rubles. for 75 m 2.

Waterproofing diffusion. Izospan A - from 1500 rubles. for 70 m 2. Ondutis A 120 (with double self-adhesive tape) - from 2070 rubles. for 75 m 2. Yutafol D 96 - from 1560 rubles. for 75 m 2. Yutafol D 110 - from 2470 rubles. for 75 m 2.

Superdiffusion membranes... Izospan AM - from 2070 rubles. for 70 m 2. Izospan AS - from 2900 rubles. for 70 m 2. Izospan AQ proff - from 3890 rubles. for 70 m 2. Ondutis Smart SA115 (with self-adhesive tape) - from 3100 rubles. for 75 m 2. Yutavek 85 - from 3050 rubles. for 75 m 2. Yutavek 115 - from 4000 rubles. for 75 m 2. Yutavek 135 - from 5000 rubles. for 75 m 2.

Video description

For a visual overview of waterproofing materials, see this video:

Conclusion

Even such a concise description of different options for waterproofing a roof for corrugated board allows us to conclude about the complexity of its device. Taking into account the nuances of the choice of materials of the required characteristics and properties, only professionals can design and carry out installation. Errors lead to wetting of structural elements, insulation and floors. And this is fraught with the loss of the load-bearing properties of the rafter system, not to mention such "trifles" as the loss of the thermal insulation qualities of the roof and overlap.

- a fairly common material in recent years, since it is of high quality, durability and practicality, along with an affordable price.

However, for the correct and durable laying of such material, several important rules must be observed: choose the size you need and choose the right substrate for it.

Without knowing the basic rules for installing metal tiles, it is impossible to lay it efficiently and efficiently.

The sequence of the correct laying of metal tiles:

• must be installed before installation;
• then lay a layer of hydro and sound insulation on them;
• mount and counter crate;
• only after carrying out the previous points can the metal tile be laid.

The metal tile has few flaws in comparison with other roofing. The main ones are high conductivity of external noise and poor thermal insulation. It is the correctly selected substrate that will help to cope with these disadvantages..

The substrate will protect against external environmental influences, give the structure additional strength and durability, prevent roof leaks and blowing, give a comfortable atmosphere in the house and significantly reduce the level of street noise transmission.

Different materials can be used as a substrate for metal tiles. Usually for this you will need a crate, waterproofing film, rafters and insulation.

There are two main types of roofing underlays, which differ in the type of space heating.

When choosing insulation for the roof, you must first of all start from the room in which you plan to block the roof. For residential buildings, it is better to choose a heater that is safe for health. such as mineral wool, cork board or fiberglass. Any type of material is suitable for industrial or non-residential buildings.

Insulation is laid under the metal tile in a certain way - the plates are staggered in several layers, this layout allows you to overlap the seams of adjacent slabs, which contributes to maximum protection against heat loss.

The thickness of the insulation sheet should be 5 cm, in this case, laying sheets in several layers will allow you to achieve a thickness of 15-20 cm, which is considered the best option.

Creation of ventilation space

Ventilation under the roof- an obligatory element, since it serves several purposes at once:

• removes moisture accumulating under the roof;
• prevents the formation of icy areas and evens out the temperature over the entire surface in winter;
• prevents the penetration of street heat in hot weather.

A special ventilated roof ridge is intended for air outlet, and air inflow occurs through the eaves overhang. Without properly installing the ventilation system, you will soon encounter a problem of high humidity, and as a result, the structure will quickly deteriorate.

Metal roofing on roofing material

Roofing material is considered a common option for a substrate for metal tiles. Such material can be used for an insulated attic..

This scheme has a lot of advantages:

• roofing material - inexpensive substrate, which will significantly save your repair costs;
• installation of the substrate does not require special skills and abilities;
• roofing material - popular building material so you can buy it everywhere.

However, for high-quality installation of metal tiles on roofing material, you need follow certain rules:

• in no case should the sheets be laid directly on the roofing material, this creates favorable conditions for the displacement of the structure. It is necessary to make a crate in two layers: 1 - over roofing material, 2 - under the wave of metal tiles;
• alternatively, you can fill regular slats along the installed rafters;
• to prevent fires and simplify ventilation of the room, it is worth building ventilation openings.

It is best to entrust the installation of the roof to professionals. However, if you are determined to independently perform all the work, then carry out them in accordance with the established requirements. Only in this case, you can get a durable and reliable design.

Decking is by far the most popular and demanded material in the construction industry. With its help, fences, outbuildings, garages are erected, interfloor ceilings are made and the roof is covered. And these are far from all areas of application of the material. Let's figure out how the corrugated board is laid on substrates, what the latter are for and what purposes they serve.

Today, corrugated board can be found in two types - galvanized and polymer-coated. Each of these types has a number of advantages. Which one to choose is up to you; a consultant can help in this matter. By the way, our advice to you: if you decide to cover the roof with roofing sheeting, entrust the calculations to a professional. Let the company from which you order the corrugated board will make an accurate calculation of the required material, but you can easily do the installation yourself - there is nothing complicated about it. The main thing is that you have all the tools you may need at hand.

So, remember the basic rule: transport and, accordingly, load the material only on a solid and flat surface. And the packs should be so long that the edges of the profiled sheet do not bend.

It is imperative to take care that during transportation the roof covering does not move around the machine, which can lead to mechanical damage to the material. To avoid this, observe the maximum speed when transporting no more than 80 km / h, do not accelerate or brake too sharply.

We load and unload profiled sheets

The profiled sheets (which, by the way, are packed in bundles) are loaded and unloaded with a hoist with soft slings. Traverses are used if one package is more than five meters.

If it is impossible to use equipment, as many people as possible should load and unload the corrugated board (the approximate calculation here is as follows: one person can lift a maximum of one and a half meters of the professional sheet). All manipulations with the material must be carried out carefully, try not to bend the profiled sheets, otherwise this may cause deformation of the material. The transfer of corrugated board always occurs only vertically!

In no case do not throw the corrugated board on the floor, do not drag it along the ground! Doing this is strictly prohibited.

How to fold corrugated board correctly

We raise the corrugated board to the roof

Before starting work, the material is delivered to the roof. This can be done, for example, by applying lags. They are installed in advance from ground level to the roof. Lifting should be unhurried, and no more than one sheet at a time.

If the weather is too windy, the rise of the material is delayed until the wind calms down, otherwise you will deform the corrugated board and it will become unusable.

After the corrugated board is raised, control measurements are made. When installing the rafter legs, measure the roof slopes, because you can involuntarily deviate from the working project.

Therefore, it is better to play it safe once again: measure the diagonals of the slopes, which will help to measure their squareness) the permissible difference in the diagonals is no more than 2 centimeters). Also pay attention to the pitched plane. Measurements are made by level. In case of deviations from the planes, there is a possibility that the corrugated board will not dock.

The corrugated board should be tilted at least 12 degrees!

Safety engineering

Before starting the installation, the corrugated board should be treated with special enamel, which is intended for coatings treated with polymer.

Naturally, you cannot avoid moving along the corrugated board. But be extremely careful, the sole of the shoe should be soft, walk along the wave deflections, or in places of the sheathing.

The fastening of the corrugated board is carried out with self-tapping screws, they are screwed into the wave recessions. By the way, screwing in the bolts, you will definitely have shavings, it should be carefully removed with a brush, if this is not done, you risk that the screws will rust over time. If there are cuts, chips or damage, be sure to treat them with a special enamel coating, otherwise corrosive phenomena cannot be avoided.

When carrying out roofing work, use gloves, this will avoid injury from corrugated board, because the edges of this material are sometimes very, very sharp.

Before starting the installation of the corrugated board, be sure to remove the protective film from the material, otherwise over time it will sinter with the polymer that covers the material.

A categorical prohibition on the use of a grinder in relation to profiled sheets! This tool is capable of damaging the profile so much that irreversible corrosion processes will begin on it.

We cut professional sheets

Of course, roofing works involve. As already noted, it is strictly forbidden to use the grinder for these purposes. However, there are many other tools to help you. For example, cut the corrugated board with cut-through scissors, they "take" steel, the thickness of which is up to 0.6 mm.

If no scissors are available, use a drill bit. This method helps to cut sheets up to 0.8 mm thick.

You can also use lever scissors, they cut metal sheets in any direction, however, if their thickness does not exceed 0.6 mm.

The fastest and most efficient way to cut corrugated board, of course, is to use electric shears, they are able to cut metal up to 1.2 mm in thickness.

How to arrange a drainage system

The device of the drainage system requires certain tools. First, you can't do without a strip bender. It is designed to bend the gutter holders up to 4 mm. The need for the “corrugation” pliers is to create corrugations at the ends of the gutter pipes. These ends provide docking.

Another tool is a hermetic gun, it is necessary during the installation of profiled sheets. Gun with staples No. 10. With their help, the hydro and vapor barrier is fixed.

A special attachment for the screwdriver allows you to easily and efficiently screw hex head screws into wooden bases.

Sheathing template, it is organized to carefully mark the sheathing steps.

Also, a hammer, tape measure, drill, cord, rail and marker will come to your aid.

Underlay for profiled sheets

When installing profiled profiled sheets, as a material for the roof, the technology of work assumes that a heat-insulating roofing layer will be arranged under it. Along with the waterproofing layer, these two slabs form the base of the roofing cake under the profiled sheet. Such peers have a very important protective function.

It is extremely important to choose the right thickness of the thermal insulation. It is equally important to protect it from moisture. When the heat-insulating layer gets wet (even by 5%), its thermal performance is more than halved. Because of this, the roof will freeze through, the decoration of the premises will freeze and be damaged. Footprints will start to form on the outside of the roof. And after that, not far from the appearance and spread of the fungus, rotting of the crate, and so on.

Insulation of the roofing system

The substrate is laid on the rafter system. The frame is covered with a hydro-retaining film. By the way, thermal insulation is also placed under it.

A layer that retains heat, under the reliable protection of a film or membrane that isolates vapor emissions. Sheathed attic perimeter is done with OSB or timber. In order for the mixing of air flows (which, by the way, occurs under the ridge) to be effective, they usually install the so-called. "Cold triangle".

Attic underlay

Use a cold roof to make the underlayment. What does it mean? We lay out the farm with waterproofing. The thermal insulation is placed horizontally on the ceiling. From the side of the room, the waterproofing is protected by a special vapor barrier film or membrane with glued joints.

Roof insulation

Roof waterproofing

To arrange a thermal roof, waterproofing membranes are used. They are opened in the valleys even before the main level of waterproofing is arranged.

The main waterproofing is opened horizontally along the length of the rafters (avoid sagging). It is better to start from the eaves to the ridge, make an overlap of one and a half centimeters.

We make the crate

The lathing is usually installed on a material designed to contain moisture. It is made of wooden beams 50 × 50 mm in size. They are treated with antiseptic agents before use. Also, edged boards 32 × 100 mm are used in the lathing device. The main board (it is usually run along the cornice) is always larger than the rest. By the way, in the place of the outlet of the chimney, fire hatch or ventilation hole, it attaches additional boards.

Only after the moisture limiters are installed and the ventilation in the roof space is ready, the installation of the sheathing begins. Its thickness is in direct proportion to how high the profiled sheets and the length of the fasteners.

The steps are applied at least half a meter. By the way, this distance also depends on how thick the material is and what section the profile has. Wind boards are installed at the ends, they are slightly higher than the crate, but they are installed at a distance equal to the height of the profile.

The profiled sheet is attached to the crate with self-tapping screws with rubber washers on the bottom of the sheet, from five to seven screws per square meter of material are used. The sheets are connected with rivets.

If the corrugated board is installed correctly, the roofing weight is evenly distributed, the roof will not be afraid of any weather conditions.

Even the use of such a reliable and durable coating as corrugated board for the roof cannot absolutely exclude the possibility of moisture getting into the under-roof space. This can be caused by slanting rain with strong winds or a winter blizzard. Sometimes moisture can penetrate under the roof in the places where the corrugated board is attached to the crate. This can happen due to the destruction of the sealing rubber washers or the weakening of the self-tapping screws as a result of thermal deformations of the corrugated sheets.

The ingress of even small amounts of moisture under the roof negatively affects the reliability and durability of not only the roof, but also the building structures of the entire building. To create such conditions for the operation of the roof, in which the penetration of moisture under the roof is simply impossible, high-quality waterproofing will help.

Waterproofing film for corrugated board

The question stands apart: "Is waterproofing necessary for corrugated boarding when installing a cold roof?" The answer is unequivocal - no, since there is no roofing pie. In the case of an insulated roof, waterproofing is indispensable.

It is on the waterproofing device and materials for it that will be discussed in this article.

Film waterproofing for corrugated roofs on pitched roofs

In the very recent past, glassine or roofing felt were used for waterproofing pitched roofs. But both of them have a number of disadvantages, therefore, waterproofing of a roof made of corrugated board using these materials is not performed.

Glassine is not strong enough and short-lived, and roofing felt under the corrugated board cannot be laid at all without an obligatory device between it and the roof covering of the ventilation gap. This is due to the fact that the bituminous impregnation of roofing material has a very low melting point, and the roofing from the profiled sheet in the sun can heat up to very high temperatures. Moreover, these materials are highly flammable.

Waterproofing for corrugated board is carried out on the basis of modern film materials, which are of very high quality and excellent characteristics. The requirements imposed on them are mainly reduced to the following:

• moisture resistance;
• resistance to mechanical stress (strength);
• elasticity;
• resistance to temperature influences.

Waterproofing films have a very wide range of applications. They can be used for both waterproofing and vapor barrier, and for both at the same time.

The existing films can be divided into three main groups: these are polypropylene and polyethylene films, as well as special diffuse membranes.

Waterproofing of profiled sheet using polyethylene films

To increase strength, polyethylene films are always reinforced with a fiberglass mesh and laminated on both sides with a special polyethylene coating. They are mainly used for waterproofing cold (non-insulated) roofs. In addition, waterproofing under a profiled sheet using polyethylene films is performed if it is necessary to create a waterproofing layer between the roofing and a diffuse vapor-permeable membrane, which is laid on top of the insulation layer.

Also, polyethylene waterproofing is used to protect the building structures of the insulated floor from condensation. In this case, the waterproofing film is laid under a layer of insulation.

Waterproofing for corrugated board using polypropylene films

Polypropylene films are used for the same purposes as polyethylene films, but they have greater strength and, besides, they are also more resistant to ultraviolet radiation. Polypropylene films can have a special anti-condensation layer. In this case, their upper surface remains smooth, which contributes to good drainage of moisture drops, and cellulose-viscose fiber is applied to the lower one. This layer is very hygroscopic and easily absorbs excess moisture. As the temperature rises, the absorbed condensate gradually evaporates.

Waterproofing under the corrugated board on the roof is laid on top of the rafters parallel to the eaves with an overlap of 100-150 mm. It is not recommended to stretch the film too much to avoid rupture due to compression at very low temperatures. The optimum is the sagging of the film between the rafters by 20-30 mm. Waterproofing joints in the overlap areas are sealed with special adhesive tape.

To create a ventilation gap, over the waterproofing film along the rafters, slats are stuffed, the so-called counter-lattices, having a thickness of 40-50 mm. A frame is then attached to these slats for the installation of the roof covering.

Diffuse membranes

Diffusion membranes have appeared on the construction market relatively recently. This modern material has the unique property of letting steam through from the inside of the building and preventing moisture from entering the under-roof space from the outside.

In addition to diffuse membranes, there are also so-called superdiffuse membranes. They have a higher vapor permeability - from 1000 g / m2 versus 400-1000 g / m2 for conventional diffuse membranes. This feature allows you to effectively remove excess moisture from the insulation, which is especially important in very humid climates, heavy snowfalls or frequent showers. In addition, the super diffuse membrane is indispensable in case you are converting an uninsulated attic into a living space and do not want to deal with the reconstruction of the entire roofing pie, including the rafter system.

Unfortunately, with all their advantages, both diffuse and superdiffuse membranes cannot be used as waterproofing under corrugated roofing. This is due to the greatly increased risk of corrosion of metal roofs due to condensation. This problem is solved with the help of special volumetric diffuse membranes, which were developed specifically for waterproofing roofs made of corrugated board, metal tiles and other materials with high thermal conductivity.

Volumetric diffuse membranes protect the metal roof from condensation using a special grating, which has an uneven height. Due to this, there is no tight fit of the membrane to the coating and the necessary ventilation is provided.

However, this material has a significant drawback - cost. In the case of using volumetric diffuse membranes, the price of waterproofing for corrugated board will be several times higher compared to the use of a conventional film.

Waterproofing mastics for flat roofs

Waterproofing of flat roofs is most often done with bitumen-based materials. If earlier it was roofing material and waterproofing material, now they are being actively replaced by bitumen-polymer roll materials. These so-called "fused" materials are based on fiberglass or polyester fabric.

Modern bitumen-polymer materials are very reliable, durable and guarantee a long service life of the roof covering. Such waterproofing for corrugated board can be laid both on top of the sheet, if it plays the role of overlapping the building, and under it as additional waterproofing.