Completely 100% no roofing guarantees you protection from moisture. There are always weak points at the joints, places of contact with pipes, walls. All this is the potential for leakage, so the "layer cake" of the roof is a necessity, not a whim. Waterproofing is no less important than the finishing roofing material, and today we will talk about such a variety as a waterproofing film. The choice for the roof and the installation of this coating is in our review.
Read in the article
- 1 Why roof waterproofing is needed: the obvious facts
- 2 Roofing films: features and characteristics
- 2.1 Types of waterproofing films
- 2.1.1 Polyethylene waterproofing
- 2.1.2 Polypropylene film
- 2.1.3 glassine
- 2.1.4 Diffuse membranes
- 2.1 Types of waterproofing films
- 3 How to choose a waterproofing film
- 4 Features of installation of roofing film
Why roof waterproofing is needed: the obvious facts
A multi-layer cake of high-quality roofing consists of several components. Finishing external coating, corrugated board or soft roof, thermal insulation that retains heat in the under-roof space, vapor barrier and, finally, waterproofing. With a competent approach to construction, the waterproofing layer not only does not let moisture in, but also reliably isolates the elements of the roof structure from condensate, which is formed due to daily temperature fluctuations air.
Waterproofing also protects the roof insulation. Usually it is mineral wool, and it tends to accumulate moisture, including from the air.
Thus, roof waterproofing performs the following important tasks:
- prolongs the life of the roof structure;
- retains the properties of the insulation for as long as possible;
- provides an optimal level of humidity in the under-roof space;
- protects wooden and metal structural elements.
The lack of waterproofing is fraught with many troubles, at least - a banal leak.
Roofing films: features and characteristics
Roof waterproofing today can be performed in a variety of ways.
There are general requirements that are important for any waterproofing material. In addition to fulfilling the main task, this is the longest possible service life, ease of installation, environmental friendliness and maintainability.
If we consider waterproofing taking into account these necessary requirements, then the following types of coating can be distinguished:
- coatings based on polyethylene and polypropylene;
- anti-condensation protection with roll perforation;
- membranes made of polymeric material reinforced with synthetic fibers;
- coating materials with bitumen, polyurethane, polymer base;
- spray rubber;
- built-up compositions with a polymer base;
- deep penetration impregnations with moisture-proof components.
Moisture protection of the roof needs a professional attitude and strict adherence to materials handling technologies. In addition, experts recommend the use of complex waterproofing, combining protective materials for maximum effectiveness.
Types of waterproofing films
Waterproofing films have a fairly wide range, so you need to figure out what characteristics certain varieties of this material have.
Polyethylene waterproofing
This is a very common and one of the most inexpensive types of waterproofing, which is familiar, if not to everyone, then to very many. We are talking not just about ordinary polyethylene, its varieties are used for roof waterproofing.
It can be an ordinary polyethylene film of high (at least 200 microns) density. The material does not pass water, steam, air.
Another type is perforated film. In it, unlike simple polyethylene, there are microscopic holes that allow the material to be vapor-permeable. Such a film in building materials stores can be sold under the name "hydrobarrier" or "anti-condensation membrane". Due to its excellent vapor permeability, this type of polyethylene film is suitable for waterproofing metal roofs and can last a quarter of a century.
Polyethylene film waterproofing also includes reinforced polyethylene film. This is a three-layer material, in the middle of which there is a fiberglass mesh, which makes the film extremely durable. The two outer layers are dense polyethylene. Such a waterproofing material is more often used for the installation of greenhouses, but it is also very successful for the roof. option, because thanks to the light reinforcing frame, it does not sag and freely removes moisture.
Polypropylene film
Polypropylene, unlike polyethylene, is more resistant to the ultraviolet spectrum of solar radiation. If the installation of the roof requires some time before laying the roofing finishing material, then it is better to use polypropylene film, as it will not become brittle under the scorching sun. Thus, you can not worry about the protection of the under-roof space.
Until recently, a polypropylene membrane for waterproofing could only be purchased complete with Finnish metal tiles, but modern manufacturers today have already appreciated the popularity of this material and offer polypropylene films separately.
The polypropylene film is sealed, which leads to the formation of condensate. To eliminate this problem, manufacturers apply an absorbent layer of cellulose to one side of the membrane. This approach will avoid the formation of drip condensate. When the temperature regime changes, the viscose layer dries up and the reasons for the formation of condensate are eliminated.
glassine
Despite the wide range of different membranes, many builders prefer glassine waterproofing. In fact, this is cardboard impregnated with a composition of bitumen and a plasticizer. Glassine is one of the oldest waterproofing materials that was used long before the advent of synthetic membranes. He has proven his high efficiency with vast experience, so such a choice is fully justified.
Glassine on sale can be found with different markings: P-250, P-300, P-350. Accordingly, P-250 is a material of a lower, economy class, P-350 is glassine with powerful impregnation and good vapor permeability.
Diffuse membranes
This type of roofing waterproofing is perhaps the most expensive, but it is also called the most practical. On the one hand, "breathing" membranes prevent the penetration of atmospheric moisture under the roof, on the other hand, they do not are an obstacle to the evaporation of the same moisture formed due to temperature changes in the roofing pie.
To achieve the effect of vapor permeability, the membranes are perforated. The canvas itself is made of non-woven material, but it has a feature: it is vapor-permeable and non-permeable side, so it is very important not to make a mistake when laying, otherwise the result will be accurate to the opposite.
The disadvantage of breathing membranes is only one - the high price compared to other waterproofing materials.
According to the level of permeability, diffuse membranes are divided into three categories:
- pseudo-diffuse, having a minimum vapor permeability. Such a membrane is laid only with a mandatory gap between it and the insulation;
- diffuse, with medium vapor permeability;
- super diffuse films with maximum efficiency.
How to choose a waterproofing film
The waterproofing film must meet certain basic criteria. These include :
- maximum ability not to pass moisture;
- resistance to the damaging effects of ultraviolet radiation;
- resistance to significant temperature changes from +80 degrees to at least -40;
- the material must have the highest possible mechanical strength and at the same time remain elastic in order to cope with the loads during installation and operation;
- the waterproofing film must have anti-condensation properties.
An important factor in the choice is the service life of the waterproofing coating. Installation of a roofing "pie" is a costly and not a quick matter, repeating this procedure for the sake of updating waterproofing is still a pleasure. So, when choosing a material for waterproofing, you should give preference to one that will provide protection for the longest possible time. Pay attention to the manufacturer of the film and its warranty. The absence of a guarantee in itself should raise doubts.
Ideally, the membrane coating should not allow moisture to pass through, but at the same time it should not interfere with evaporation from under the roof. In this regard, all budget film options will not give you the desired effect.
Features of installation of roofing film
Installation of a waterproofing film is complicated by only one circumstance - the fact that it is necessary to carry out work at height. Of course, it is important to observe all safety measures when working at heights. In principle, even no specialized tool is required here - just a construction stapler with staples.
There are uniform installation rules. Film waterproofing is laid on top of the insulation laid on the rafter system. If the film is not breathable, it is necessary to provide a ventilation gap of 3 to 5 cm. This issue is especially important if the final roofing is metal tiles, since due to the heating from the sun there will always be large temperature drops in the under-roof space.
Film waterproofing is laid in strips, starting from the bottom of the roof, from the eaves. The material is straightened over the rafters, straightening all the folds and fixing the canvas with a stapler on the rafter legs. A feature of laying anti-condensation films is leaving a small, 1–2 cm, sag in the space between the rafters.
After the film takes its place, all seams are additionally reinforced with moisture-resistant tape.
Is it possible to fix the waterproofing film not horizontally, but vertically? In principle, if the roof is low, it is possible, but it is imperative to provide for an overlap when joining parts of the canvas and carefully glue it with adhesive tape. Lastly, the skate is covered with a separate canvas, placing it on top of other canvases. Complete coverage of the ridge is made only by superdiffuse membranes that allow air to pass through. If the waterproofing is made with a vapor-tight film, a gap of about 20 cm is left on the ridge for normal ventilation and elimination of condensate.
After fixing the waterproofing, a counter-lattice of thin laths is laid on top of it, which are fixed on the rafters with nails or self-tapping screws. On top of the counter-lattice, the finishing roof is already laid directly.
Separately, you should pay attention to the system for removing condensate from the waterproofing film. This moisture has nowhere to go, so you need to give it the opportunity to drain into the drain. If this point is left unattended, condensation will penetrate under the cornice boards and inevitably cause them to rot.
You can skip the film waterproofing directly along the cornice board and lower it into the gutter.
A problematic place for waterproofing is a slope fracture. At this point, the valley is completely covered with a waterproofing film. Then, prior to the installation of the main waterproofing, a single sheet of material is laid on the valley, from the ridge itself to the cornice board, and fixed with waterproof tape. Only after such a procedure, the waterproofing sheets are fixed in the usual manner from the bottom up.
It turns out that a double layer of a hydrobarrier is formed in this area. After that, a metal element of the valley is placed in the gutter to drain water.
If we are talking about vapor barrier, but impervious films, then the installation principle will be somewhat different. In this case, the film can be mounted in two ways - either from the outside of the roof, or from the attic. Preference is usually given to installation from the attic side, as it is simpler and avoids mistakes, since the entire rafter system is visible.
If you decide to mount from the outside, you need to follow a certain algorithm.
In this case, a small thickness insulation is mounted on the base from the outside, which will then protect the waterproofing film from the sharp tips of the self-tapping screws. Then material is laid from the eaves. To straighten it from the folds, use the rule - a long, even rail.
Such work must be carried out quickly and during the day, so that unexpected precipitation does not spoil the whole thing.
The procedure for installing a vapor barrier is detailed in this video:
Remember that it is important to choose high-quality material with guarantees from the manufacturer, only in this way your roof will be reliably protected. What waterproofing film can you recommend based on your own experience? Share your opinion in the comments!
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