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Much has been said about the importance of such a structural element of a building as the roof. Here are the features of the architectural appearance, and protection from atmospheric influences, and the durability of the house. Modern approaches to the design of the attic space make it possible to make maximum use of its volume. This makes it possible to save money, but requires, one might say, a scrupulous approach, since the design of a residential attic involves the inclusion of thermal insulation, protective films, etc.
The roof in section has a layered structure. This is the so-called roofing pie, each layer in which performs a specific function, but it is very important that they are placed in the correct order. Any mistake made during their installation can negatively affect the performance characteristics of the roof and its durability.
The correct roofing pie diagram
The roof pie is a multi-layer structure that includes such components as:
- interior finishing of the under-roof space;
- air ventilation gap;
- vapor barrier film;
- insulation;
- waterproofing;
- sheathing;
- roofing material.
It also includes gutters, an anti-icing system, fences, snow guards and decorative roof elements. That is, we can say that the roofing pie is nothing more than the entire roof structure, with the exception of the rafter system.
The presence of all these components is not necessary; the structure of the pie may vary depending on the type of roof and the roofing coverings used.
For example, a flat roof cake does not include snow retainers and decorative elements; for attic spaces for technical purposes there is no need for vapor and thermal insulation of the roof.
The installation of a roofing pie under metal tiles, corrugated sheets, for soft roofing or other materials also has some differences.
- A roofing pie under a soft roof made of bitumen shingles may not have a waterproofing layer, since the bitumen itself ensures the waterproofness of the coating. Only joints, corners and cornices need waterproofing. The film must pass directly under the roofing material.
- For soft rolls, a special waterproofing lining made of polypropylene is required.
- For roofs made of metal tiles or corrugated sheets, sound insulation is additionally required, otherwise noise from rain will create discomfort in the room.
On a note
As you can see, some layers in the roofing pie may be absent, and some, on the contrary, are “dictated” by the characteristics of a particular structure.
Base Layers
Vapor barrier layer
This layer protects the thermal insulation from the penetration of water vapor condensing into the under-roof space from living quarters. This is where the arrangement of the pie begins.
The vapor barrier film is laid along the rafters from the inside of the room with an overlap of at least 10 cm. It is attached to the load-bearing elements using staplers or galvanized nails with a flat head. To ensure the tightness of the vapor barrier, the joints are connected with connecting tape or carefully taped.
roofing pie under metal tiles with an insulated roof and a non-insulated one
Thermal insulation
If it is planned for residential premises, then they should be as warm and comfortable as in the rooms on the main floor. But let's not forget that the ceiling here is the same roof through which heat escapes to the street. Hence the task of particularly high-quality insulation of the under-roof space arises. Its effective solution lies in the correct choice of material for thermal insulation and technology for performing the work.
Let’s first determine what the criteria are that the roofing pie insulation must meet. The following requirements apply to thermal insulation:
- low thermal conductivity coefficient;
- environmental Safety;
- flammability;
- volume weight;
- soundproofing properties;
- vapor permeability;
- form stability.
Insulation has no heating properties at all, it simply traps air in the fibers and thus retains heat.
Attention
Moisture is the first enemy of the thermal insulation layer. Once water gets into the insulation, it stays there and the material loses its effectiveness. This is due to the large difference in the ability to conduct heat between water and air: for water it is two dozen times higher than for air.
The thickness of the thermal insulation layer depends on the climatic conditions of the area: for areas with mild winters, a layer of 15 cm is laid, for frosty ones – from 20 cm.
The range of thermal insulation materials is quite large. Let's note the most common ones:
- often used mineral wool slabs. It has low thermal conductivity, it does not burn, and has a dense structure. However, it is not recommended to use them in the roofing pie of a metal roof: copper, metal tiles or others, since condensation protruding on the back side of the roof can penetrate the insulation and it will lose its qualities.
- Fiberglass- an environmentally friendly material that is larger than a flat roof. The reason is its unstable mechanical structure, which does not allow it to stay on the pitched roof - sooner or later it will slide down.
Mineral wool, like fiberglass, can be used on roof areas of complex construction. The slabs can be easily placed in any space, completely filling the niche between the rafters, thus preventing the occurrence of cold bridges.
- primarily due to its budget cost. In addition, it is moisture resistant. However, one cannot ignore such facts as its flammability and the presence of toxic emissions during the combustion process.
- Expanded polystyrene is different light weight. It retains heat well, is moisture resistant, like polystyrene foam, but unlike it, it is non-toxic. The material is vapor-proof, so in summer there is an increase in the level of humidity in the room. The rigid structure of the slabs creates certain difficulties in the process of thermal insulation of difficult areas.
When installing roofs with slopes, thermal insulation materials with a loose structure are more suitable, while hard materials are needed in the insulation layer of the roofing pie for a soft roof.
The installation of roofing insulation is carried out by reducing the moisture content of the wood of the supporting structure elements to at least 18%. Otherwise, moisture from it will penetrate into the thermal insulation.
Ventilation
The natural roofing pie is ensured by a special gap formed by the counter-lattice and sheathing. In fact, this is an air gasket passing between the insulation layer and the waterproofing. Through it, excess moisture accumulated in the insulation is evaporated. They can form when the humidity outside increases, for example, in the off-season, or get there through possible cracks in the coating, etc. In the absence of such a gap, the moisture accumulated over the season will ruin part of the insulation.
The circulation of air flow from the eaves to the top point of the roof, the ridge, is ensured by special openings on the eaves overhang and. It is especially convenient to arrange ventilation under corrugated sheets.
Forced ventilation is organized by installing ventilated ridges. They can be powered by electricity or by wind movement.
Waterproofing layer
Waterproofing performs two functions simultaneously:
- protects thermal insulation from moisture coming from the roof covering;
- through it, excess moisture is removed from the thermal insulation.
That is why, when installing waterproofing, it is correct to choose the direction of the sides of the film. Otherwise, the multi-layer structure of the cake will not be able to function correctly.
Vapor barrier film is not suitable for these purposes, since moisture does not pass through it.
The roof structure is far from the simplest element of a building. As a rule, it consists of several layers of different materials that provide the proper level of noise, vapor and heat insulation. And, of course, they protect the house from precipitation at any time of the year.
However, different types of roofing require the appropriate types of materials. Experienced builders often know all time-tested options. And in the case of a roof pie under metal tiles, a number of additional nuances must be strictly observed.
In this article
Type No. 1: cheap and cold
A rational option if the roofing pie is calculated for outbuildings, gazebos or for housing in warm regions, where snow and cold are known only by hearsay.
The design of a cold roof is very simple and consists of only five elements:
- Rafter system.
- Waterproofing film. The hydraulic ventilation gap must also be taken into account.
- Counter-lattice (wooden slats, planks or bars).
- Lathing (bars or edged boards).
- Metal tiles.
Easy to install, more budget-friendly. However, at the same time, you will have to forget about heat and sound insulation from the outside.
Type No. 2: minimum noise, maximum heat
An option for most private houses whose owners do not want to hear booming noise during rain and freeze when cold weather arrives.
What is included in the design:
- Vapor barrier, which is installed on the inside of the roof.
- Rafters with longitudinal purlins are the main load-bearing element of the structure.
- Thermal insulation material is installed between the rafters and purlins. Gaps for ventilation must also be provided.
- Waterproofing is installed above the insulation surface - a film/membrane that allows steam to pass through from the inside, but does not allow moisture to penetrate from the outside of the roof. The distance of waterproofing from the insulation should be approximately the same as from the metal tile - 40-50 cm.
- A counter batten is installed parallel to the rafters, pressing the waterproofing. It also serves as a support for installing the sheathing.
- The sheathing is where the metal tiles will be mounted. It is recommended to use beams with a design cross-section of 50x50, the fastening spacing along the slopes is 35-45 centimeters.
- Metal tiles.
Such a metal roof pie will cost a little more, and installation will be more difficult and longer. However, the correct installation of these components will reliably protect against cold and precipitation. Such a roof will retain heat much more effectively than its “cold” counterpart.
Rules for selecting metal tiles
There are different tiles and tiles. Even if the material seems to be the same type. The current market offers customers a wide variety of options with any characteristics, appearance and, of course, price.
One of the main parameters affecting the strength of a material is the thickness of its metal base.. Typically, roofing pies use sheets no thicker than 0.4-0.5 mm. Reinforced options are guaranteed to affect the reliability of the roof, as well as the magnitude of its load on the rafters. Be sure to take this into account when calculating the roof frame.
In addition, any metal tiles must be covered with a protective layer during manufacture.. It provides resistance against aggressive external influences. And how effective this protection will be is determined only by the quality of the layer itself. Which will directly affect the cost of the tiles.
The height of its waves will give additional strength to the material. However, do not forget that galvanized sheets of the same length are used for any tile. Therefore, the greater the height of these waves, the material becomes not only more stable, but also gives less useful width.
Finally, the large length of the sheets greatly simplifies the entire installation process. In addition, the risk of leaks is reduced. On the other hand, this approach increases the chances of longitudinal deformation of the roof.
You need to know this from the very beginning
When assembling the roofing pie, special attention is paid to two points: the correct location of the waterproofing and ventilation gaps.
Many owners try to save on materials by purchasing cheaper mineral insulation, ecowool or glass wool instead of waterproof foam. With this choice, the costs will indeed be significantly lower. But then it is the thermal insulation that will become the most vulnerable point in the entire structure. After all, these materials are highly susceptible to the harmful effects of moisture. By “destructive” we mean the loss of its heat-saving properties up to 80%. Therefore, it is strongly recommended not to skimp on at least waterproofing.
However, not a single roof of a private house can be completely protected from moisture penetration into the roofing layers. For such cases, gaps are provided between the thermal insulation and the upper level of the cake, the dimensions of which are usually 30-40 mm. The air flow should go from the roof overhang to the ridge.
Slightly shorter gaps (10-15 mm) should also be present between the tiles and the waterproofing.
Installation technique
After calculations and selection of all necessary materials, the most important stage comes - installation of the roofing pie. Both types have their own characteristics, so when choosing a “cold roof” you can immediately proceed to the third stage. In the case of a “warm roof” you need to start from the very first point.
- A vapor barrier layer will protect the roof from the harmful effects of steam from a warm room under the roof. Different types of vapor barriers require a certain gap during installation (which may vary from product to product). Therefore, for such cases, a counter batten (thickness - 30 mm) is first installed along the joist. A vapor barrier is attached to it using a construction stapler or counter-lattice. It must be laid along the slope from its lower part to the upper. Each row of the vapor barrier overlaps the previous one (100-150 mm). Exactly the same applies to longitudinal joints.
- On the outside of the frame, insulation is stuffed between the joists. Space for air gaps must be provided.
- A mandatory step not only for a “warm” roof, but also for a “cold” roof. A waterproofing film is attached along the joists using a vertical counter-lattice (beam 30x50x50 mm) with a nail pitch of 30 cm. A ventilation gap is also required here - the material must sag by at least 1-2 centimeters.
- And the sheathing is already installed on the counter-lattice. Its pitch, as mentioned earlier, should not exceed 45 cm. In valleys, ridges and various junctions it is laid completely.
Please note that all wood materials of the pie must be calibrated and dried under natural conditions before installation. Treatment with fire retardants and antiseptics is highly desirable.
Finally, be sure to pay attention to your home's roof at least twice a year.. Regular preventive maintenance and, in particular, monitoring of additional elements, joints and junctions in advance will help to avoid possible problems with the roofing pie.
A little over 30 years ago, a roofing material was invented, which subsequently became widely known and received several names - flexible tiles, soft tiles, bitumen shingles. We will consider the properties of this roofing material, its advantages and disadvantages in other articles, and now we will focus our attention directly on the installation of roofing insulation pie under soft tiles.
Let us pay attention to the climatic conditions of installation; if you are installing tiles at temperatures below +5 degrees, it is necessary that the flexible tiles be stored in your home for some time immediately before installation, or use a hot air gun. Installation in winter is not the best option, and manufacturers do not recommend installing soft tiles at temperatures below 5 degrees Celsius.
The main stages of the roofing cake
Preparing the base. The base for soft tiles is a material with a flat and smooth surface, to which fastening with nails is possible. Moisture-resistant plywood is used as such material; edged boards and humidity should not be higher than 20%. The joints of the boards must be placed at the support locations.
Making a ventilation gap. The ventilation gap should be at least 50mm, the exhaust hole should be located as high as possible, and the air supply hole should be lower. Air access is necessary to remove moisture from the insulation, sheathing and roofing material. Reducing the formation of ice and icicles, as well as reducing the temperature inside the roof in hot weather.
Installing the lining layer. Rolled insulation material is used as a reinforcing lining material under soft tiles. It is laid from bottom to top, parallel to the eaves of the roof, the edges are fixed with nails.
Installing metal curtain rods. To protect the edge of the cladding from moisture, metal cornice beams are mounted on top of the lining material.
Installation of valley carpet. To increase the water permeability of the roof in the valleys, a special valley carpet is laid corresponding to the color of the roof, the edges are fixed with nails.
Installing eaves tiles. We install self-adhesive eaves tiles that run along the eaves overhang. Soft tiles are laid joint to joint and nailed close to the contact points with a subsequent layer of tiles.
We install ordinary tiles. We begin installation from the center of the eaves overhang in the direction of the end parts of the roof. We glue the tiles, having first removed the protective film from the back side, and nail each one with four roofing nails just above the tile groove line. If the roof slope is more than 45 degrees, then each tile is secured with 6 nails. We lay the first row of tiles so that the bottom edge is higher than 1 cm from the bottom edge of the other.
Installing ridge tiles. Ridge tiles are obtained by dividing eaves tiles into 3 parts. Mount it on the roof ridge, nailing four nails so that the nails are under the next tile.
To protect the under-roof and living space from the negative influence of atmospheric phenomena, an important part of the roof is the roofing pie. Each layer performs a specific task and is inextricably linked with the previous and subsequent components of the pie. Correct installation of the roofing pie is the key to the durability and reliability of the roof. How to do it correctly will be discussed in the article.
Components of the roofing cake:
- Internal lining.
- Moisture insulation.
- Ventilation gaps.
- Roof anti-icing system.
- Roofing material.
All these elements will be discussed separately in the article.
Installing a vapor barrier protects the heat-insulating layer from vapor from the room. This layer is installed first. By the way, the layers are counted from the inside of the roof. The vapor barrier is laid from film, overlapping. It is connected to each other using connecting tape. This ensures the tightness of the vapor barrier.
Innovative vapor barrier materials contain a foil layer. Thus, it is possible to increase the thermal insulation properties of the cake, as well as improve the fire resistance.
It is worth noting that there must be an air gap between the vapor barrier and the insulating material. If you make a gap of 2 cm, then the installation work will be more difficult, and in this case you will have to increase the financial costs of the roof.
The next is the thermal insulation layer. Most often, slabs made of mineral wool are used for these purposes. It is important that this material is resistant to deformation. The insulation of the roof depends on the type of its construction. For example, you may need to insulate the roof itself or the ceiling of the upper floor.
The insulation does not heat. Its function is to trap air in its fibers. This is called thermal insulation.
Moisture destroys insulation, such as mineral wool. This is due to the fact that the thermal conductivity of water is 20 times higher than the thermal conductivity of air. This means that the heat insulator must always be dry.
To protect glass wool and mineral wool, these materials are treated with special impregnations. However, such an event does not provide 100% protection against moisture penetration. A more reliable insulation in this regard is extruded polystyrene foam. It perfectly resists capillary and diffuse absorption of water. The only drawback of the material is its high cost in comparison with other more cost-effective heat insulators.
Installation of thermal insulation can only be carried out when the humidity of the wood elements of the roof is reduced to at least 18%. Otherwise, moisture from the wood will penetrate into the thermal insulation layer, which, as mentioned above, will negatively affect the quality of the roofing cake as a whole.
A ventilated roof separates the layer of insulation and roofing material. The ventilation device involves following the sequence of several stages of work:
- If the roofing material is embossed, then making ventilation holes and installing a ridge fan will not be difficult. A sheet that is wavy can be covered with a flat ridge. Today, forced ventilation is also common, providing artificial air circulation in the under-roof space. These processes are ensured by special equipment.
- Cornice boxes and ventilation holes are installed near the ridge. Each soft roof kit includes a ventilated ridge.
- There are special holes in the lower cornice. Special protection prevents insects and small birds from getting into them. After this, ventilated skates are installed.
- If it is impossible to carry out the above actions, then special roofing fans are installed in the ventilated gaps above and below, which ensures forced air circulation.
Roof icing can be a serious problem. To avoid this danger, many owners of private households install systems in the roofing pie that prevent the formation of ice. They are heating cables and other equipment that ensure the roof is warmed up in winter, which minimizes the likelihood of ice forming on the roof.
Stages of work:
- Laying cables in places where snow accumulates and possible icing. This is the area near gutters and skylights, if any.
- Connecting cables to the power supply, as well as to the temperature sensor and control unit. This is a kind of weather station that turns on/off automatically if necessary.
The choice of hydrobarrier depends on the type of roofing material being installed. High-quality waterproofing ensures the long-term preservation of all elements made of wood.
When installing a waterproofing film, it is important to know exactly the correct location of the sides of the material, since one of them should be directed towards the roof, and the other towards the insulation. Otherwise, the roofing pie will be done incorrectly.
There are several types of materials for roof waterproofing:
- Superdiffusion membranes allow water vapor to pass through but retain moisture. This material has a high vapor permeability, which means that with this type of waterproofing there is no need to install a lower ventilation gap. Such a membrane should fit tightly to the insulating layer. Superdiffusion membranes cannot be installed when metal tiles and euro slate are used as roofing materials. The membranes are attached to the rafters using a counter beam, on which the sheathing can be installed.
- Diffusion membranes are films with microholes that resemble funnels. The holes should be directed with wide surfaces into the room. Moreover, for maximum efficiency of such material, ventilation gaps are made at the bottom and top. These membranes can be used when installing tile and bitumen roofs. These membranes allow steam to pass through and retain moisture coming from the roofing material. In this case, the membrane must not come into contact with the insulation, as this will lead to clogging of the micro-holes, as a result of which the membrane will lose its vapor permeability. Membranes are used when installing roofing material that does not deteriorate when in contact with moisture.
- Condensate films are designed to work with tiles and euro slate. In this case, two ventilation gaps are installed. One side of the film is fleecy, which improves its ability to retain condensation deposits. After this, moisture will move into the lower ventilation gap. The other side of the roof will be ventilated thanks to the upper air channel. This ensures the roof is protected from moisture.
The layered structure of the roofing pie when installing a soft roof has almost the same composition as that used when installing hard roofing material.
Made from materials that have high waterproofing characteristics. These include bitumen roll materials and their piece counterparts, as well as mastics and innovative membrane coatings. Nowadays, soft roofing has not only water barrier properties, but also high aesthetic properties. Today it is possible to attach super-thin soft roofing materials to any type of base.
The advantage of a soft roof is that it combines insulating and aesthetic functions, as a result of which the roofing cake has been reduced to only three layers.
During the installation of bitumen shingles, waterproofing is performed along the entire roof plane only when the slope of the slopes is no more than 18º. If this indicator is higher, then waterproofing is laid only along overhangs, along valleys and ridges, at junctions and around pipes. The formation of a roofing pie is influenced by the following factors:
- Type and purpose of the construction project (residential or domestic building).
- Thermal insulation is only used if the building is intended for permanent and not temporary use.
- Roof shape and slope.
- Type of base for roofing pie.
- Attic space - residential (arrangement of the attic) or non-residential.
- Determination of the thickness of thermal insulation depending on the climatic characteristics of the region.
- Compatibility of cake layers. Otherwise, the installation of migration/separation layers will be required, which will entail additional financial costs.
In order for the roofing pie when installing a soft roof to be of high quality and durable, it is important to take into account all the above-mentioned factors.
When installing a flat roof, just like in the other cases mentioned above, you need to make a roofing pie. In this case it looks like this:
- Base.
- Insulation.
- Hydrobarrier.
The first step is to prepare the base. It is leveled, cleaned, the cracks are filled with polyurethane sealant, with a joint width of 5 cm and a depth of 0.3 cm. Priming is carried out with an epoxy primer, which is pre-mixed with a mixer at minimum speed until smooth, and then diluted by ½ with water. The primer is applied with a roller or paint brush. Then the surface is reinforced with mastic.
Polypropylene or polyethylene film is used as a vapor barrier, secured with a binder, nails or glued. The gap for ventilation should be 10 cm. The thermal insulation should fit tightly to the roof, ventilation units and pipes.
Not only reinforced concrete, but also a metal profile structure can serve as the base of a flat roof. The method of mounting the pie and its type are selected depending on the base of the roof. Bitumen or roll material is used as a vapor barrier.
One of these materials can serve as a heat insulator:
- Expanded clay gravel.
- Minvata.
- Cement-sand screed with expanded clay.
- Expanded polystyrene boards.
So, this article looked at the types of roofing pie depending on the roof structure. We can say that choosing the composition of a roofing pie is quite a troublesome matter, since it is important to take into account the compatibility of materials, financial capabilities and type of roofing. However, in skillful hands, everything will work out, so it all depends on the abilities of the craftsman who calculates and installs the roofing pie.
Video
In this video, you can find out other details of making a roofing pie:
Often during construction, owners of private houses try to use even the attic area for living quarters. Some of them plan only summer-type rooms (unheated) on the attic floor, but preference is still given to full-fledged rooms in which you can live all year round. And this circumstance directly affects the arrangement of the roof. If in attic rooms the insulation is usually laid on the floor to insulate the heat coming out of the lower floor, and the empty space of the attic itself serves as an air layer that prevents cold from penetrating from the roof into the rooms, then the attic room is insulated differently. All insulation from the floor must be transferred to the roof structure. Therefore, in attic-type houses, a mandatory element of the roof is a roofing cake - a multi-layer system of different materials that provide heat, hydro, vapor barrier and ventilation.
In a roofing pie, each layer performs a specific function, but subject to the correct order of placement. It is better to entrust the creation of such a pie to professionals, but every owner should be aware of what it is in order to control the quality of the installation, check whether all the layers are laid in the correct order, and know what materials are best to purchase. If the installation of the roofing pie does not comply with the standard, then heat loss will occur through the roof, condensation will form, and in winter - ice and icicles. This means that all the insulation was done in vain.
Each layer has its own purpose and is inextricably linked with the others. An error in the installation of one of them leads to a reduction in the service life and performance characteristics of the roof.
Let's consider the sequence of laying layers, and what materials are best selected for each layer.
Uninsulated roofing pie
It is created in cases where people plan to live on the attic floor only in the summer, and the ceiling of the main rooms is already insulated. In this case, the main task of the roofing pie is to isolate the attic from condensation entering from the outside, and to allow moisture to escape from the house to the outside. To prevent air microcirculation from being disrupted, a waterproofing film with tiny holes (micro-perforation) is laid.
The sequence of laying an uninsulated cake is as follows:
- A rafter system is created.
- A waterproofing film is laid.
- The counter-lattice is being filled.
- The sheathing is attached.
- Roofing material is laid.
Read on to learn more about the installation features of each layer.
Insulated roofing pie
This is a more multi-layered structure, which is used for attics in which it is planned to equip full-fledged residential premises. And its task is not only waterproofing, but also heat preservation. The thermal regime under the roof differs significantly from the climate on the ground floor.
An insulated roofing pie can turn an attic into a living space
In summer, the roof can heat up to 70˚, and in winter it can get very cold. Of course, there can be no comfortable living in such a room. Therefore, the roofing pie must not only retain heat inside during the winter, providing air insulation from contact with the cold roof, but also prevent hot air from coming into the house during hot weather.
The attic loses heat more intensely than the lower floors, since it has a larger total surface of contact with the external environment
Let's look at the structure of an insulated roofing pie in more detail.
Rafters
The total thickness of all layers of the roofing pie is about 35 cm, so the rafter system must take this into account. To know for sure whether the height of the cut rafters is enough, decide what material you will use as insulation. For example, basalt insulation has a thickness of about 150 mm, so timber with a traditional thickness of 100 mm will be too small.
The rafters, which will bear the main load of the roof, are best made from coniferous wood, which has no flaws. Choose wood with a moisture level of no more than 22% and be sure to saturate the entire wood with antiseptic compounds.
The rafter structure must be treated with antiseptics before laying the roofing pie
The thickness of the rafters and their pitch are selected depending on the covering that will be used to cover the roof.
Vapor barrier layer
It is from this layer that the installation of the roofing pie begins, although the last inner layer will be the finishing.
Why do you need a vapor barrier layer?
There is always moisture inside any house, and there is more of it in the warm air, which, according to the law of physics, tends upward, i.e., into the attic floor. Neither natural nor forced ventilation can completely remove excess moisture, and when it gets on the roof structure, it settles as condensation. In our case, the vapor barrier layer must protect the insulation, which is laid as the next layer, from moisture penetration, since the thermal insulation material saturated with moisture completely loses its properties.
What material is used for the vapor barrier layer
- Glassine is an affordable vapor barrier, but its ability to retain moisture is lost over the years.
- Vapor barrier film. As a rule, such a film has several layers and a reinforcing frame made of polymers, which prevents it from sagging.
- Foil material.
Foil as part of a vapor barrier material will increase the level of heat retention, since it does not transmit infrared radiation
This can be a film with a foil side or a material reminiscent of chocolate wrapper, in which one side is paper and the other is made of foil.
Both options, in addition to waterproofing, perform another important function: they do not allow infrared radiation to pass inside. And since it is precisely this that causes heat loss from the premises, then with the use of a foil layer, heat loss is reduced (and this is without insulation!). In terms of price, this waterproofing material is more expensive than others.
How to attach a vapor barrier layer to the rafter system
- The material is rolled out along the rafter legs. As a rule, waterproofing film is sold in rolls, which must be rolled out along the ridge. Laying begins from the bottom, and the rows are laid overlapping, extending 15 cm onto the previous layer.
- The most convenient way to fix the film to the wood is with a construction stapler.
- The places where the rows are laid and the edge adjacent to the wall must be sealed, secured with connecting tape. Instead of tape, you can carefully glue it with tape.
note! There is no need to stretch the film too much. It should sag slightly between the rafters (up to 2 mm).
All rows of vapor barrier film begin to be laid from below, and the joints are tightly sealed with tape
Thermal insulation layer
If you plan full-fledged rooms on the attic floor, then the microclimate and heat level in them should be no worse than in the rooms on the main floor, which means they need to be insulated with the same quality. Moreover, the ceiling (aka pitched roof) has a large surface area in direct contact with the street, which leads to significant heat loss. The thermal insulation layer of the roofing cake will help reduce them.
How to choose the right insulation
There are many materials for insulation on sale. But for a residential building, the thermal insulation material must meet the following requirements:
- be environmentally friendly;
- non-flammable;
- vapor permeable;
- isolate sound.
Let's consider which insulation materials are used most often.
Mineral wool. The most commonly used insulation. The material is based on basalt fiber, does not burn, has a dense structure, and a high level of heat retention. But you shouldn’t buy it for a roofing cake under metal tiles, because the condensation formed on the back side of the roofing can penetrate into the mineral wool and quickly saturate it, causing the insulation to lose its properties.
The soft structure of mineral wool completely fills the volume even in the most inconvenient areas of the rafter structure
Fiberglass. Non-flammable, environmentally friendly material. But the structure of fiberglass is unstable and tends to “slip”. Therefore, it is not recommended to cover pitched roofs with such insulation, but only flat ones.
Both mineral wool and fiberglass should be laid on roofs with difficult areas. They easily fit into any niches, filling the entire volume between the rafters completely, thereby preventing cold bridges.
Styrofoam . Popular due to its low price and good thermal insulation. A big plus is that it does not absorb moisture. But it should be borne in mind that it is flammable, and when burned it forms toxic compounds.
Expanded polystyrene. Demanded due to its lightness and low thermal conductivity. Non-toxic and does not absorb moisture at all. But due to vapor permeability, increased humidity may be observed in the room in summer. But in case of roof leaks, moisture will not get inside from the street. Expanded polystyrene boards have a rigid structure, so they are difficult to lay on difficult areas of the roof.
So, to summarize: for pitched roofs it is best to use insulation with a loose structure, and hard materials are suitable for a soft roof.
What layer of insulation is placed in the roofing pie?
The minimum layer of insulation for areas with mild winters should be at least 15 cm. If winters are frosty, then it is better to lay 20 cm thick.
If one layer of insulation is not enough, apply a second one on top
The ventilation gap serves as an air gap between the insulation and the waterproofing film, which will prevent moisture from entering from the outside. It is needed to ensure that excess moisture is removed from the insulation, which is formed in the off-season, when there is high humidity outside, or that gets through cracks in the roof, etc. In roofs with a roofing pie, it is very difficult to find and eliminate leaks, because entire blocks of mineral wool may get wet in one place, and a crack will appear somewhere near the ridge. And if you do not provide an air gap, then during the season, with such a leak, a large amount of insulation can deteriorate (especially fiberglass and mineral wool, which absorb moisture).
How to create a ventilation gap:
- If a corrugated material is chosen as a roof covering, then passive ventilation will be created in any case, even if the ridge structure is flat.
- For forced ventilation, you need to purchase special equipment that is driven by the wind or powered by electricity. This includes aerators and special ventilated skates.
- On pitched roofs, natural ventilation is sufficient, but on flat roofs, forced ventilation is required.
With roof ventilation, moist air is easily removed from under the roof, either by natural draft or using special ventilation valves
Waterproofing layer
The task of waterproofing is to prevent moisture from the roofing from entering the thermal insulation layer, but to remove excess moisture from the insulation. Therefore, the film that was laid in the vapor barrier layer will not fit here: it does not allow moisture to pass through. For waterproofing, special materials are purchased, including:
- Diffusion membranes
This is a film coating in which there are microscopic holes, shaped like funnels. The wide side of the funnels is laid against the insulation, and the narrow side against the roof covering.
They can only be laid if 2 ventilation gaps have been created. Contact with the insulation is not allowed, because the funnels will become clogged and will not allow steam to pass through.
The moisture in such pies escapes under the roofing material, so diffusion membranes are allowed to be used with roofing coverings that are not afraid of condensation on the back side.
These films introduce vapor so effectively that they do not require the creation of an air gap. This is convenient for those houses where the roofing pie is not created immediately during the construction process, but in an already residential building.
Superdiffusion membranes are the most popular materials for protecting the roof of a house from condensation, leaks and external moisture.
Both membrane options are not suitable for metal tiles and euro slate, because the back side of these coatings is afraid of condensation, but roofing tiles under soft tiles and clay tiles are installed with this type of waterproofing.
- Condensation films
They are used on roofs made of metal tiles and euro-slate, because the films are vapor-tight. Moisture from the insulation settles on the fleecy surface of the waterproofing layer and is carried out with ventilation. The second air gap (under the roofing) prevents condensation from settling on the back side of the roof.
Counter-lattice and sheathing
After laying the waterproofing, the counter batten bars are filled, and the main sheathing is laid over it. The type of sheathing depends on the roofing material. For soft tiles, ondulin, a continuous sheathing is made of oriented strand board, plywood or boards; for slate, metal profiles, etc., the sheathing is made of bars with gaps for ventilation.
The sheathing for metal tiles is made from bars to create an additional air gap that will prevent condensation from settling on the back side of the covering
The roofing covering is laid on top of the sheathing.
Video recipe for “layer cake” under metal tiles
Now that you know all the nuances of the roofing pie, you can safely invite the construction team and observe from the side that the work is being carried out correctly.