What could be more difficult than a repair, and not even a current one, but a major one? That's right, building a house. There are much more problems here, and the various solutions and forks, when you have to choose one thing, cannot be counted at all. So you will have to work hard so that the house stands for a long time, and during the entire period of its operation it does not leak, the windows are not blown through, and the foundation does not collapse under the weight of the building. But today we will talk about something else - about one of the final stages, in fact, of construction. That is, the roof. More specifically, about how to lay the vapor barrier on the roof.
What is a vapor barrier?
As a matter of fact, the technology of production and use is simple to the point of impossibility - one more additional layer of material is put into the roof, which does not allow moisture to pass through. A vapor barrier layer is usually a film made from several types of materials, which will be discussed a little later. So, as you can see for yourself, there is nothing super complicated about it.
Why do I need a vapor barrier?
A little above, a few words were said about the long operation of the house.
So, in order for the roof to serve for a long time, you should think about its vapor barrier. This is not done to prevent moisture from entering the house from the outside, as you might think, no, it's all about the water vapor that rises up from the inside. Modern materials that are used for roofs are quite capable of retaining heat well and not allowing water to enter the house, but nothing protects them from getting wet from the inside. For these purposes, it is necessary to use an additional layer of material that does not allow water vapor to reach the upper layers of the structure and prevents them from spoiling. That's why you need a roof vapor barrier.
Roof space
In the construction "jargon" you can find such a thing as a roofing pie. This is due to the fact that the roof is just something like a pie. That is, many layers of different materials are superimposed on each other - they all play different roles, and therefore none of them should be excluded. It can cost you anything, up to an early full roof replacement, and you certainly don't need it. There is no pleasure in such works, especially completely meaningless ones.
Vapour barrier for the roof of the house is installed as the lowest layer of the roof. From top to bottom, the diagram will look like this:
- roofing;
- crate;
- waterproofing;
- insulation;
- rafters;
- vapor barrier.
That is, this layer is vital to protect everyone else - in case it is not in place,mold will form inside the roof, the materials will begin to deform and collapse. All this can even lead to the collapse of the erected structure.
Roof vapor barrier. Materials
Today, the construction market is extremely developed, and therefore it is almost impossible not to find the right material for anything. Plus, it doesn't require anything too special. The same materials that are used for waterproofing are quite suitable. So you can just buy more plastic wrap and use it not only in the middle of the "pie", but also at the bottom. This method is much easier than others. In addition, you can also buy a polypropylene film or even a membrane. These three types are discussed below and separately. In addition to them, there are others, but not so common, for example, isospan, although it is quite promising.
Plastic films as a vapor barrier
This is the most readily available component that can be used as a roof vapor barrier. In addition, as already mentioned, it is universal. True, for greater structural strength, due to the lack of special qualities of rigidity and density, it will be necessary to use films with reinforced fabric or mesh.
Such films are produced in two different types - perforated and non-perforated. The former are used only for waterproofing the roof, but the latter are for your current purpose. The fact is that perforated films are produced with holes, which makes them unsuitable forvapor barrier. At least theoretically. In practice, even such a film can be used as an insulator.
Polyethylene films are produced in rolls, and this is how you will lay them - for this reason, you should take care of buying a sealant in advance. This is absolutely necessary to create a vapor barrier, which this film will take on.
Polypropylene films
This type is mainly used for waterproofing work. It is still sometimes used for vapor barrier, but only when there is nothing else at hand. Otherwise, it is better to purchase a different kind.
By design, they consist of two layers. One of them is a combination of viscose and cellulose, which is used to absorb excess moisture and then dry.
Membranes. Feature
This material is quite expensive, but it is understandable - it is much more modern. In fact, membranes are closest to perfection, that is, to complete vapor barrier and protection of the roof from external influences. However, it would be rather unwise to use them for this purpose - waterproofing is much more suitable for them, especially for two-layer specimens. These models (not only two-layer, but they are more) are interesting in that they do not let water through, but let steam through, which then lingers in the upper layer and evaporates.
Vapour barrier for the roof with your own hands
Of course, it's always much easier to call the experts and let them do everything. This givesa sufficient guarantee of quality, and besides, you don’t have to work hard for an invisible after result. But if you still want to make a house from top to bottom yourself, then the tips given here should come in handy.
It is best to disassemble using isospan as an example - laying films is quite easy, and instructions can be found almost everywhere. In addition, the technology for laying the vapor barrier here is almost the same, the differences are only in small details.
Required tools
Of the tools that are needed to install the vapor barrier, you only need a construction stapler. If it is not at hand, do not worry. It is quite possible to get by with a hammer and a certain number of nails. The latter, by the way, are best taken galvanized.
Materials
In addition to isospan, the properties of which are described above, you will need the following materials:
- Adhesive tape - for sealing seams and various joints.
- Sheathing - used as a decorative element so that the vapor barrier layer of the material is not visible. You can make such a sheathing from OSB boards, drywall, lining, MDF, etc.
Installation process. Diagram
Vapor barrier for the roof is laid according to a certain scheme. As you remember from the previously submitted information, it is located at the very bottom and is attached to the rafters. For this first step, a construction stapler or nails will be used.
Izospan is produced in the form of rolls, therefore, in the corners, as well as at vertical and horizontal joints, it is necessarymake an overlap. This will help prevent steam from leaking into the insulation layer.
The last installation step is to secure the resulting layer with the previously mentioned adhesive tape. All joints, corners, places where the material adjoins the walls must be carefully glued with such a tape. Such a careful approach is needed to seal any possible passages.
In addition, if you sheathe the vapor barrier on top with decorative material, you must leave a gap of about five centimeters. This will allow ventilation.
Overlappings: Do I need a vapor barrier film?
In fact, the vapor barrier of the floors is the same necessary process as the vapor barrier of the roof, especially if your structure is made of wood. This is where humidity becomes critical. In addition, this is necessary if there are bathrooms and bathrooms below - there will always be more moisture there than in the rest of the house. This also applies to kitchens. Also, the ceilings between the basement and the first floor are often equipped with a vapor barrier - especially if the premises are heated. The accumulation and evaporation of condensate in this case is inevitable, which makes the installation of a vapor barrier mandatory.
Vapor barrier: to do or not to do?
Here the answer is unequivocal - to do. The second option is fraught with serious consequences. In fact, there is nothing particularly complicated in this process, and therefore you should not neglect it, just as you should not pay attention to small details that can subsequently becomedefining.
It should also be noted that the vapor barrier for the roof, the price of which is not so high, especially compared to other things and materials needed during construction, is available to many. So, films will cost you about one and a half thousand, but these are the cheapest (from 660 rubles per roll). The better the material, the higher the price will be. For example, the most expensive membranes already cost about seven thousand rubles.
The price shown here corresponds to 75m2 film, which is enough for one average home.
