Roofing profiled metal sheets are one of the most common roofing materials. The popularity of corrugated sheeting is due to its affordable price, ease of installation, and low weight. However, along with 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 there is literally a light drizzle under the roof. Wooden structures and insulation have to be protected from condensation. The authors of some articles posted on the Internet argue that under the steel sheets there should be waterproofing layer and even allow themselves to give advice on the choice of material. However, in fact, waterproofing under corrugated sheeting is not necessary, and sometimes is contraindicated.
It should be understood: not all materials designed to protect against moisture are waterproofing.
Absolutely waterproof, withstands quite high water pressure (continuous flow of water), very durable and resistant to atmospheric influences, ultraviolet radiation, which allows it to be used in open form. Waterproofing is carried out 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 flat roof the waterproofing layer can simultaneously serve as a roof covering
As the name suggests, it does not allow water vapor to pass through. Both rolled waterproofing materials and polymer membranes cope with this task, but they are inconvenient for use in lightweight wall and roof structures. It is much easier to attach thin and light reinforced polyethylene vapor barrier films to the frame. And they are much cheaper. The vapor barrier is also waterproof and can protect against rain. But she doesn't have enough mechanical strength and resistance to ultraviolet radiation, which does not allow the use of vapor barriers in an open form, but only under the protection of the roofing and wall cladding.
Reinforced polyethylene and polypropylene vapor barrier films are mainly used for roofing. Mounted truss structures V warm time It is allowed to leave it uncoated for a couple of months, under the protection of only a vapor barrier. It will protect the wood from precipitation. But not longer, the film’s resistance to ultraviolet radiation is limited, snow load she may also not be able to stand it
Wind and moisture insulation for roofing can protect fiber insulation from wind blowing, retains liquid water to a certain extent, but at the same time freely allows water vapor to pass through. Due to such selective properties of moisture transmission, wind and moisture insulating films are also called diffusion membranes. They can be made of polymer fibers (non-woven canvas) or perforated film, and there are also combined options.
Due to the presence of pores, the diffusion, wind and moisture-proof membrane allows water vapor to pass through. But the size of these pores is so small that drops of water falling on the surface do not penetrate the film. The force of surface tension prevents this from happening. However, if you wet the membrane for a long time and generously, sooner or later it will get wet and “leak.” Wind and moisture protection is not suitable as protection against heavy rain; immediately after its installation, the roof should be covered with a roofing covering
It’s clear: if the film is under-roofing, it means that it is placed directly under the roofing covering. One of its main functions is to protect the rafter system and insulation (if any) from condensation, which can fall abundantly on profiled metal sheets. Any of the insulation materials listed above can handle it: hydro(vapor) insulation, diffusion membrane (wind insulation). However, these are not all the problems that under-roofing film is designed to solve. What exactly is required of it and how to choose the right under-roofing film (membrane) directly depends on the type of roof. Let's consider two types of roofs: cold attic and warm attic.
IN Lately There has been a tendency to call vapor barrier a roofing film, and wind and moisture insulation - a roofing membrane. This is not an entirely correct use of the terms, but that’s the way it is. 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; ignorant sellers of building materials and illiterate builders also contribute. Wind and moisture insulation and vapor barrier are often called waterproofing. This is wrong, you need to understand that these are not the same thing, the materials have different physical properties, intended for different types roofs
There is no need to insulate the attic roof, but you can ventilate it by making holes in the gable walls or sheathing.
In our case, the fundamental difference between a cold attic and an attic (combined) roof is how they are ventilated, how excess moisture is removed from the wood and insulation
In this way, moisture from inside the attic is removed thanks to good internal ventilation, you just need to protect the structures from condensation that forms on the underside of the roofing. It is possible to install waterproofing under corrugated sheets. They once did this, they rolled out roofing material under wavy asbestos-cement sheets (slate). Theoretically, you can use old linoleum, sheets of plastic, tin and other unnecessary rubbish that does not allow water to pass through. However, a special vapor barrier film will last longer, is easier to install, and is very inexpensive. You can also use a diffusion membrane, but there is little point in this: it will cost more, and its properties of transmitting water vapor will not be in demand.
The roof structure of a cold attic must include a vapor barrier film
It is important to know: for a cold attic roof, the best under-roofing film is a vapor barrier, but any type of moisture-wicking material will do
The attic roof must be insulated, and insulation and wooden structures have the ability to absorb moisture from the air. It will not be possible to ventilate them from below, from the side of the premises; the air there is more humid than outside. On the contrary, the roof needs to be protected from moisture from the inside by covering the rafters with a vapor barrier film. The only way to prevent wood and mineral wool from becoming damp is to ensure their ventilation from the outside, be sure to leave a ventilated area between the roofing covering and the under-roofing film air gap height of at least 4 cm. Hydro(vapor) insulation will not ensure the release of water vapor, therefore for attic roofs only vapor-permeable wind and moisture insulation (diffusion membrane) is used.
Correct design mansard roof and walls frame house. The structure must be protected from the inside by a vapor barrier, and from the outside by wind and moisture protection. But not the other way around!
Important to know: the only suitable option roofing film (membrane) for standard construction mansard roof- diffusion membrane.
There is an option for a combined (attic) roof, in which a vapor-tight hydro or vapor barrier is used as an under-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 not used often. Please note that the under-roofing film (4) closer to the overhang is placed on top of the steel apron (15), and that is placed in the gutter drainage system. This should always be done to ensure that condensation drains beyond the roof structure.
In conclusion, we will say that not only the comfort of living in the house, but also the durability of the structure 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 modern technologies, the best solution will entrust the execution of responsible work to experienced professionals.
On the market building materials seasonal lull. Only the assortment for interior work and roofing materials. Among the latter, there is no equal in demand to the popular, for some time now, corrugated sheeting. Having replaced the slate, due to its environmental unreliability, he immediately painted the new roofs in all the colors of the rainbow. Practicality, safety and economic expediency became its distinctive features.
Later, not everything turned out to be so rosy. Being absolutely vapor-tight, it has the ability to condense drops of water on its inner surface. In addition, water can get into the under-roof gap as a result of poor fastening of the corrugated sheeting to the sheathing, damage (aging) of the rubber washers of the screws, or deformation of the roofing sheets.
These drops, regularly collecting under the roof, increased humidity and caused the growth of harmful fungi on wooden roof structures. Moreover, when they got on the insulation layer, they significantly reduced its thermal insulation properties. The roof becomes cold. In extreme cases, they caused leaks into living spaces.
The main task of waterproofing under corrugated sheeting is to collect all condensate and divert it away from the roof. This is especially true when the under-roof space is residential. It is then that the roofing insulation cake especially needs protection from moisture.
Such protection looks like this:
The amount of overlap depends on the angle of the roof. If its value is more than 30 0, the overlap must be at least 150 mm; if the value is less than 30 0, the overlap cannot be less than 250 mm. At smaller roof angles, the use of corrugated sheeting is not recommended.
Important ! In order to avoid rupture of waterproofing at cold temperatures, it is necessary to spread it with a sag, between the bars of the conro-lattice, up to 3 cm. In this case, it should be strictly avoided from touching the thermal insulation.
Otherwise, the process may be disrupted natural ventilation roof space. Organizing such ventilation is the main task of professional roof installation.
The spreading process must be carried out across the counter-lattice, starting from the very bottom to the top.
The waterproofing sheets are fixed using fastening brackets to the counter-lattice bars. On top of it, in the future, a transverse sheathing will be mounted for attaching corrugated sheets.
Important ! The sheathing is done with edged, antiseptic boards in increments of 300 to 1000 mm. The pitch of the sheathing depends on the load-bearing capabilities of the corrugated sheet. When the wave height is less than 20 mm, the sheathing is made of a continuous carpet of boards with a possible thickness of 25 mm.
The long-term service of the entire roof will depend on how carefully and accurately all installation work is carried out.
The time when bitumen paper (glassine), waterproofing or roofing felt was used as waterproofing is long over different varieties. The slate, which was replaced by corrugated sheeting, prevented the appearance of both condensation and high temperatures in the spaces between the roofs. On sunny days, corrugated sheeting heats up to temperatures exceeding the melting point of bitumen. With a large roof angle, it simply began to flow.
The problem was solved by new waterproofing materials, the physical and mechanical properties of which fall within the following parameters:
In addition, when choosing a waterproofing material, you need to pay attention to its resistance to various mechanical and chemical influences, and the release of harmful gaseous elements when heated. Waterproofing materials meet all these requirements.
Polyethylene films. Polyethylene polyethylene films have proven themselves well as waterproofing for cold roofs. They can also be used as a vapor barrier.
Diffuse and superdiffuse membrane waterproofing at the same time they have increased vapor permeability and good waterproofing capabilities. The disadvantage is excessive vapor permeability, which can lead to corrosion of the corrugated sheet if there is insufficient ventilation.
Volumetric diffuse membranes. The presence of a volumetric mesh contributes to better ventilation and thereby eliminates the disadvantage of conventional, diffuse membranes, high price limits its use.
Important ! Reinforced polyethylene film has proven itself well on warm roofs as an additional waterproofing between corrugated sheeting and a vapor-permeable diffuse membrane
From the school physics course we know that warm air can contain more vapors than cold air. As the warm air cools, it releases some of its moisture to surrounding objects in the form of condensation. This is how the warm air from the heated stove rises up, under the roof, collides with the cold insulation and leaves its water marks on it. Having become wet, such insulation ceases to perform its functions of preserving heat.
Having solved the problem of preventing moisture from entering the insulation from above - from under the corrugated sheeting, it is necessary to solve a similar problem of moisture in the insulation from below, from warm room. If the entry of moisture from above was prevented by the creation of waterproofing, then its entry into the insulation from below was prevented by the creation of a vapor barrier layer.
The materials for such a layer can often be the same ones that were used for waterproofing:
Important ! The choice of material for vapor barrier depends entirely on the functional significance of the room. If this is a home for permanent residence- foil material. If this is a room for periodic, seasonal use, then it is better to use inexpensive plastic film.
Cold roofs are relevant for non-residential buildings, utility blocks and most garages. They are made cold out of purely economic relations:
Vapor barrier in in this case not needed since there is no internal heat source. And since it is not there, there is nothing for moisture to condense from. Condensation on inside corrugated sheeting will definitely be formed. The daily fluctuations in its temperature are very significant. In this case, only antiseptic treatment and good waterproofing under-roof space.
Important ! The organization of a ventilated roof ridge covered with corrugated sheets is a mandatory procedure during its construction.
The last operation when organizing a warm roofing cake is the selection of corrugated sheeting and its fastening. When the roof is almost ready and all that remains is to choose the main sheathing, then a certain skill is required. Will it be solid or made with a gap, and what size should the boards be? The outer cladding will depend on the choice of corrugated sheet parameters.
There is no special roofing sheet. Their markings are completely different:
Important ! When choosing corrugated sheeting for the roof, first of all, you need to pay attention to its specifications and load-bearing capacity.
In any case, no matter what corrugated sheeting is chosen for a specific roof, pedantry and accuracy in work will be the main criteria for the impeccable service of a roof covered with this modern and high-quality material
The roof of any building is one of the most important architectural elements of each structure. Not only the comfort of living, but also the operating time of the house depends on its reliability and durability. Repair work can often exceed the cost of building a new roof, so experienced builders We strongly advise you to strictly follow all building codes and regulations. Economically, it is much more profitable not to save on the cost of materials and adherence to technology than to then deal with forced emergency roof repairs.
This question worries many inexperienced developers, especially since some unscrupulous builders always install waterproofing under roofing materials, regardless of the type of roof. In some cases, such actions not only increase the overall estimated cost of work, but also have a negative impact on durability wooden structures.
Currently, there are two types of roofs - cold and warm. The first traditional for our country, attic spaces are not used as residential spaces. The second ones appeared relatively recently and are used during the construction of attic houses. In what cases is it necessary to waterproof a roof under corrugated sheeting?
Complex multilayer structures that can significantly reduce heat losses and provide favorable conditions in attic rooms. Heat loss is reduced through the use of insulation materials; there are currently quite a lot of them. They all have approximately the same density and thermal conductivity, but are fundamentally different in terms of hygroscopicity.
For example, polystyrene foam and expanded polystyrene do not completely absorb moisture, but mineral wool and ecowool have a high ability to increase humidity. The presence of water not only critically increases thermal conductivity, but also has an extremely negative effect on all wooden structures of the rafter system.
Conclusion - it is necessary to take measures to protect hygroscopic insulation from moisture and not interfere with its removal if wet. This means that to waterproof warm roofs, you need to use only modern multilayer membranes; they allow steam to pass through perfectly, but are completely sealed against water. Such membranes must be installed on warm roofs on which mineral wool or other hygroscopic material is used as insulation.
Regarding insulation options polymer materials, then waterproofing is desirable, but not necessary. For them, you can use not only expensive membranes, but also cheap films. The task of waterproofing is simplified; it can be impermeable to both water and steam, and it serves as an additional roofing material.
PVC membrane for roofing
Some builders install waterproofing for them too. This is explained by the appearance of condensation on metal coatings, additional protection against leaks, etc. But conscientious specialists It is not recommended to install waterproofing for cold roofs. Why?
Conclusion - the benefits of waterproofing for uninsulated roofs are very doubtful. And this despite the fact that Additional materials and work always increases the cost of the property.
Corrugated sheet
All requirements can be divided into two large blocks.
| Type of requirements | Short description |
|---|---|
 | Waterproofing materials must be resistant to chemical compounds, not stretch under static loads, and meet environmental and fire safety standards. The materials must be easy to install and have a long warranty period. |
 | Density in the range of 0.04–0.06 kg/m2, maximum elongation before breaking is at least 10%. For corrugated sheeting, the vapor permeability of the membrane must be at least 0.75 kg/m2 per day, and the water resistance for 10 minutes must be at least 0.5 MPa. physical characteristics must remain stable within the temperature range -60°С…+110°С. |
For waterproofing, you need to purchase only modern membranes that do not retain steam and provide optimal conditions operation of wooden structures and insulation.
Decker range of waterproofing membranes
| Illustration | Name |
|---|---|
 | Roofing membrane Decker 120. |
 | DEKER 135 membrane is a product of increased strength. Can be used on continuous sheathing. |
 | Decker Wind Facade (roofing) super-diffusion wind-moisture-proof membrane. |
 | Waterproofing membrane Decker Extra 165. Has a grid-like marking that simplifies cutting the membrane when installing complex areas of the roof. It is used without a gap with insulation or on continuous flooring. |
Before the beginning roofing works you need to prepare all the tools, equipment and materials.
Waterproofing membranes
Stopping installation for organizational or technical reasons always has negative consequences. It is better to draw up a preliminary plan for your actions and think through each stage.
For example, consider the option of waterproofing under corrugated sheets on a warm roof. Attic spaces will be used as residential. On the roof there are several attic windows and a large brick chimney. Such objects significantly complicate the installation process and require increased care and responsibility of roofers.
Important. Some sections of the roof have a continuous sheathing, this is due to the peculiarities of the installation of roof windows and other special structures. The membrane should be slightly raised above the continuous sheathing, this facilitates the process of removing steam from the elements.
For these purposes, slats approximately one centimeter thick are placed on such areas of the roof. Fastening is done with small nails.
If you have an electric or pneumatic nailer, great, the work will be much faster and easier. On a mechanical hammer, you can precisely adjust the impact force depending on the length and diameter of the nails, it is lightweight and has a replaceable hardware magazine.
Screwdrivers
Step 1. Reinstall the drip. The installation of all roofs with waterproofing begins with these elements. Droppers perform several functions: protect wooden elements from getting wet, improve the appearance of the roof and drain condensation into the gutter. There is an option when the drip pipes are far from the elements of the drainage system, and water drips onto the facade walls.
The drip tip is made of galvanized steel sheet approximately 0.45 mm thick. Galvanization is done by hot galvanizing, the layer thickness is 20–30 microns. The front and back surfaces are covered with protective decorative polymer paints, the color may vary and is selected depending on the characteristics of the metal profile.
The dropper is fixed with nails in a checkerboard pattern, the distance between the hardware is approximately 30–40 cm. Do not forget to make an overlap of 5–10 cm wide.
Step 2. Glue a special tape at a distance of approximately 1–2 cm from the edge of the drip. It has a very strong adhesive with high adhesion parameters to painted metal surfaces and waterproof membranes. The drip tip must be clean, dry and always free of grease.
Practical advice. Never use ordinary double-sided tape; its technical characteristics do not meet the requirements. The membrane will come off and wind will get under it, which greatly reduces the actual efficiency warm roof. In addition, there is a possibility of snow or rain getting into the resulting cracks. Because of this, the wooden elements of the rafter system or sheathing will get wet, and they will begin to rot with all the very unpleasant consequences.
Step 3. Lift the first roll onto the roof and start rolling it out. Constantly check the position of the edge in relation to the drip edge. The line should be perfectly straight and parallel. Cut off the excess and secure the ends of the membrane with a stapler, the distance between the staples is 20–30 cm.
Inexperienced builders are trying to drive in a large number of staples with a minimum pitch in the hope that in this way they will significantly increase the strength of the fastening. In fact, everything happens exactly the opposite. A huge number of holes noticeably reduces the strength of the membrane; the staples seem to cut it. Because of this, even minor tensile forces tear the waterproofing away from the base. Keep this in mind and follow the recommended fastening spacing for hardware and staples.
Step 4. Remove the protective paper strip from the tape and glue the edges of the waterproof membrane. Press the materials firmly, do not leave gaps, and do not allow wrinkles to appear.
Step 5. Nail the vertical slats of the counter-lattice. They fix the membrane to the rafters and do not allow it to mix during mechanical loads.
Practical advice. There is no need to stretch the waterproofing too much, this can have two negative consequences. First, slight vibrations of the rafter system due to wind and snow loads can tear the material. Three times - drops of condensate fall under wooden slats and provoke their accelerated decay. If the membrane sags a little, then water flows down the hollows.
The pitch between the nails is approximately forty centimeters; the slats can be impregnated with antiseptics. Step 6. If the cornice board will be fixed to the slats, then their ends must be prepared. This is done in several stages.
Step 6. Attach a special mesh that protects the under-roof space from birds and large insects.
Nail the first counter batten, position it as close to the eaves as possible. Why? The closer the self-tapping screws fastening the first metal sheet to the edge are screwed in, the stronger the roofing. The leverage of the effective breakout forces is reduced, and the breakout moment is automatically reduced. As a result, the reliability of fixation of roofing coverings increases.
Important. Nail the first rail very precisely to the level; it is considered a reference element and all the remaining ones are installed on it. This is exactly the case when you need to measure seven times and nail once.
Step 7 On the outer slats, mark the distance between the counter-lattice, use a special beating rope to mark the lines and continue to assemble the structure along it.
Continued installation of the counter-lattice
Step 8 Nail the cornice board to the ends of the vertical slats.
These works must be done carefully and in strict accordance with the recommendations of the manufacturers of waterproof membranes.
Step 1. Glue special double-sided tape around the perimeter of the chimney; it is sold complete with a membrane. The height of the hem is approximately 10 cm; apply tape at the same distance.
If the surface of the chimney is finished with decorative plaster, then the adhesive tape is difficult to stick to it. To make the process easier, use a rubber mallet and protective paper. Attach wax paper to the tape and hit it with a hammer, the tape will be strongly pressed and glued over the entire area of the decorative plaster.
Step 2. Roll out the membrane on the slope until the roll rests against the chimney. Look carefully at what length and on which side you need to cut the material. It is necessary to make a decision so that the membrane has a minimum number of cuts and fits snugly around the entire perimeter of the chimney. Don’t rush to cut, try to foresee the consequences of each action. Remember that no tape will provide the same reliable water protection as material without cuts. Use only a very sharp knife.
Step 3. Remove protective film from the tape and stick the material tightly to it.
This must be done in the following sequence:
Fakro XDP - salary dormer window, which is based on a vapor-permeable waterproofing membrane
Installation of FAKRO waterproofing around a window
Step 4. Continue laying the waterproofing using the usual technology until the slope is completely finished. Make a bend at the ridge and install the membrane on the other side of the roof.
Next, when installing profiled sheets, do not forget to leave holes to ensure effective natural ventilation. Otherwise, the service life of the roof will be significantly reduced, and very complex and expensive repair work will be required.
Be sure to follow safety rules when working at height; no roof is more expensive than your health. Safety ropes do not restrict movement, as it may seem, and do not interfere with work. On the contrary, with insurance, workers move more confidently and quickly on the roof, which increases labor productivity.
Construction boards
We hope that laying waterproofing under the corrugated board will no longer create problems. You just need to choose the right type of coating. Comparative characteristics various types there is corrugated sheeting
Comfortable living in a house is impossible without a well-equipped roof. In order to reduce heat loss during the cold months of the year and create a favorable microclimate for people staying in the house, various materials are used, including corrugated sheeting.
Thanks to the multi-layer roofing cake containing a layer of thermal insulation, heated air does not leave the room in cold weather conditions. Installing a vapor barrier under corrugated roofing helps maintain low thermal conductivity.
Many homeowners are interested in whether it is possible to cover the roof with corrugated sheets without waterproofing, and why it is needed.
In this case, the vapor barrier layer is equipped to achieve certain goals:
There is always water vapor in the air of residential buildings. They are partially removed from the premises by the ventilation system, while the rest remain. Steamy warm air rushes towards ceilings, where it cools and the resulting moisture penetrates into the roofing materials.
The insulation has a porous structure and therefore absorbs moisture vapor. When wet, the thermal conductivity of the material increases, and it retains heat in the house less well. To prevent moisture from penetrating into the porous structure of the insulation, a vapor barrier is installed under the corrugated sheeting.
The film for arranging a vapor barrier layer is placed on the side of the premises to protect the thermal insulation material and elements roofing structure from vapor penetration.
Let's think about which vapor barrier to choose for the roof so that its efficiency is at the proper level and the cost is affordable. The building materials market offers a wide range of special films for attic and cold roofs used to install a vapor barrier layer.
To accept correct solution regarding whether a vapor barrier is needed under corrugated sheeting, it is necessary to have information regarding a number of factors:
Before purchasing materials for profile flooring, you need to understand financial side construction. If price is the determining factor, then economical products are chosen.
As for efficiency, vapor barrier films differ performance characteristics and should be familiarized with them in advance.
When selecting materials, the characteristics of a particular room are taken into account. For a heated building, foil film will be the best purchase, but for cold roof from corrugated sheeting, inexpensive glassine will suffice. When erecting a roof on a building that is visited occasionally, a vapor barrier made of polypropylene or ordinary polyethylene film will be required.
To lay a vapor barrier layer under corrugated sheeting or other roofing, films are used.
The following most popular types are presented on the construction market:
The space under a cold-type roof is not heated, but the temperature inside is always different from the outside. For this reason, condensation collects at the bottom of the profiled sheets. Therefore, the answer to the question: “When a cold roof is built, is waterproofing necessary?” unambiguous Of course it is needed. Properly installed waterproofing on the roof under the corrugated sheeting will prevent moisture from entering the under-roof space.
This layer will prevent wet fumes from reaching the wooden elements of the rafter system and other parts of the roof structure. The waterproofing is laid on top of the rafters and then secured with a counter-lattice. Next, install the sheathing and corrugated sheet.
When the waterproofing layer does not prevent steam from escaping outside, then there is no need to install a vapor barrier for a cold roof. Having risen upward, water vapor gets through the film under the corrugated sheet and dries out in that place due to the movement of air currents. In this case, roofing felt, polypropylene, glassine and polyethylene are not suitable. For a cold roof, experts recommend using a non-woven vapor-permeable membrane.
Do you need a vapor barrier for a cold roof? No, because it is installed only for warm roofs, so that moisture does not get into the insulation.
The vapor barrier layer panels are laid with an overlap of approximately 15 centimeters. A connecting tape is selected for the selected type of film. Small planks for it can be wooden or metal.
When installing a roofing structure, the waterproofing, thermal insulation and vapor barrier properties of the roof are provided. Purposes of waterproofing and thermal insulation materials obvious, they are necessary to maintain heat in the room and protect against moisture penetration under the roof. But for many, the question of the need to form a vapor barrier layer remains open. What is a vapor barrier and why is it so important to use it when installing a roof?
Condensation, regardless of the type of roof, clearly negatively affects the practicality and durability of roofing materials. At the same time, it reduces the thermal insulation properties of the insulation materials used in the roof and reduces their service life.
For example, with a relative air humidity of 1%, the thermal conductivity of materials used for insulation increases by approximately 30%, and with an increase in air humidity to 5%, the level of thermal conductivity doubles.
Vapor barrier under corrugated sheeting is definitely necessary. She will give additional protection for metal roofing from the effects of condensation and will maintain the functionality of thermal insulation materials.
The use of expensive thermal insulation materials will not lead to the desired result without good protection of the roof from steam penetration and condensation formation. The protection of the roof structure from the penetration of cold into the room must be and, in total, have waterproofing, thermal insulation and vapor barrier properties.
For information on how to deal with snow blowing under the ridge, see the article “How to choose the right sealant for corrugated sheeting and roof ridge.”
The choice of vapor barrier materials depends on the result that is necessary for high-quality improvement of the structure and the budget allocated for protecting the roof from moisture.
Glassine is one of the classic materials that is used as a vapor barrier for roofing structures.
Advantages:
Flaws:
For vapor barrier of roofing metal profile In residential premises, glassine would not be the most suitable option.
Polyethylene film is divided into two types - perforated and non-perforated. For waterproofing roof structures, experts recommend using non-perforated polyethylene film.
Advantages:
Flaws:
Reinforced polyethylene film is not a bad option for multilayer vapor barrier materials for buildings with a good supply and exhaust system. Polypropylene fabric or mesh is used to reinforce the material. The main function of reinforcement is to ensure the strength of the vapor barrier structure. Most often, the installation of such vapor barrier occurs using self-adhesive films.
Advantages:
Flaws:
Polypropylene differs from polyethylene vapor barrier in structure. That negative property described in the above-mentioned vapor barrier material is eliminated due to the additional relief layer. The anti-condensation fabric layer does not allow liquid to accumulate in the form of drops on the material.
Advantages:
Flaws:
Important! Polypropylene film is installed with the porous structure facing down. It is the porous structure that has anti-condensation functions, retaining moisture in uneven areas.
Experienced craftsmen recommend, when forming a vapor barrier layer, to take into account small ventilation gaps, which must be evenly distributed over the entire area. The holes are made carefully and small in size so as not to cause the vapor barrier material to delaminate and deteriorate.
Foil vapor barrier film is one of the types of vapor barrier using polypropylene or polyethylene as the main material. This multilayer film is distinguished by reinforcement and a reflective aluminum layer, which creates a thermal effect that prevents infrared radiation from leaving the room.
Foil vapor barrier material was originally intended for use in bathhouses and greenhouses, but is now often used for ordinary residential premises. Its efficiency is quite high - on average, heat loss is reduced by 10-15%, which allows you to significantly save on heating your home.
Important! The foil vapor barrier film is installed with the reflective element down and the joints of its connection are glued with a special foil film.
Advantages:
Flaws:
An excellent option for those who are willing to spend a little more money on roof vapor barrier than when purchasing budget materials. Such an overpayment will definitely pay off in the future operation of the house due to heat conservation.
Choice vapor barrier material is determined by several criteria:
The characteristics of films can be divided according to the following criteria:
Of course, in addition to all the above criteria, many are also based on the cost of materials. Each case is a personal decision, but you shouldn’t save much on thermal insulation.
Important! When building a house, it is better to reduce the cost of materials that will not be difficult to replace during the operation of the premises.
If we are talking about vapor barrier of a roof in a residential building, then it can be divided into several different sections. If the garage of a residential building is not a basement room, but an extension to a residential building, then it is not necessary to use expensive materials to vapor barrier the roof above it. The situation is similar with the bathhouse, the gym and other premises not intended for full-time living.
