Mastic is a liquid-viscous homogeneous mass, which, after being applied to the surface and hardening, turns into a monolithic coating.
The operational quality of mastic roofing largely depends on the correct performance of work on the preparation of mastic directly on the construction site and its application to the base. One-component mastic has some advantage, since the ready-to-use composition is immediately applied to the surface. When using a two-component mastic, you must first prepare the mixture, and only then apply it to the surface. This significantly increases the requirements for compliance with the work technology. On the other hand, the preparation of a two-component mastic at the construction site allows you to change its properties in accordance with real requirements. To change individual properties of the mastic (viscosity, color, hardness, etc.), special additives are introduced into it during preparation. When using one-component mastic, to change its properties, you have to change the brand or type of mastic, which is less convenient.
According to the composition, mastics are divided into bituminous, bitumen-polymer and polymer. The composition of mastics can include a solvent, fillers and various additives.
Bituminous, bitumen-polymer and polymer mastics differ from similar roll materials in that they are formed into a coating (film, membrane) on the roof surface and, in principle, must have the same properties.
Bitumen-polymer and polymer mastics can be applied to various surfaces (steel, concrete, roofing felt) of any, even the most complex configuration (the slopes of the roofs on which the mastics are laid are not limited, up to domes and spiers). But there is one important condition: the surface must be perfectly flat, otherwise it will be impossible to achieve the same thickness of the mastic cover. This is the biggest drawback of mastics..
The mastic is applied to the base in liquid form. After the solvent has evaporated, it hardens to form a continuous, seamless waterproofing film. The thickness of the resulting film depends on the amount of dry residue in the mastic. Solvent-free mastics harden without reducing the thickness of the applied composition..
It is necessary to pay attention to the fact that with roof slopes of more than 12% and an outside air temperature above 25 ° C, special fillers must be introduced into the mastic that increase its viscosity (thickeners, cement, etc.).
Modern types of mastics do not need a protective layer, since colored in the mass they have the necessary decorative properties, and the material itself is sufficiently resistant to atmospheric influences.
If it is necessary to protect the roof from mechanical influences (passages, installation of engineering equipment, etc.), a protective layer is made of fine gravel (10-20 mm), coarse sand (2-5 mm), small-sized asbestos-cement or bitumen sheets, etc. etc. The ideal protective layer is river pebbles.
Mastics can also be used as an adhesive for the installation of roofing carpet from roll materials. They can be used both for new roofs and for repairing all types of old ones..
Modern mastics can be given the desired color. To do this, dyes are added to them, which can be done both in the factory and in the building conditions before using the mastic. The consumer can make the mastic himself, using anhydrous dyes, with the highest possible pigment content.
Modern mastics do not require preheating (the so-called “cold mastics”) and, differing in composition, are divided into one-component and two-component.
One-component mastic (on solvents) is a mastic that is supplied ready for use, and the hardening of its composition occurs when the solvent evaporates, which is prevented by a sealed container. Therefore, its shelf life rarely exceeds three months. An exception is polyurethane mastic, which hardens under the action of water vapor, which is always contained in the air. In the absence of solvent, polyurethane mastic cures (polymerizes) without shrinkage. The shelf life of such mastic in an airtight container is 12 months..
Two-component mastic – This is a mastic that comes in the form of two chemically inactive compounds that can be stored separately for 12 months or more. The long shelf life of two-component mastic is a significant advantage, as it allows you to make a stock of material for the season of roofing. One-component mastic, depending on the base, usually has a much shorter shelf life. However, modern high-quality formulations also do not lose their properties within 12 months..
To improve the strength characteristics of mastic roofs, they can be reinforced with fiberglass or fiberglass mesh. Fiberglass mesh is a woven mesh made of very durable fiberglass threads. Fiberglass nets vary in filament thickness and mesh size. Fiberglass is a sheet of randomly spaced fiberglass. Both materials are characterized by high mechanical strength, and therefore it is customary to use them as reinforcing gaskets. Reinforcement increases strength, but reduces the elasticity of the mastic coating, so it is necessary to understand what is preferable for this roof. Reinforcement can be performed only in individual nodes (usually abutments and mates).
The advantages of mastic coatings include the absence of joints and seams in the roofing carpet.
The manufacturability of applying mastics by a mechanized (air spray) or manual method (brushes, rollers) allows you to simply and reliably perform roofing work on surfaces of almost any shape and slope. This advantage is especially noticeable when constructing a roof with numerous abutments, knots and details. In these places (near mines, pipes, racks, supporting structures), thick roll materials must be cut out according to complex shapes, which significantly increases the labor intensity of the work and reduces the quality. In addition, the use of colored mastics can significantly improve the architectural expressiveness of any roof, especially a complex shape..
Mastics are indispensable for the repair of almost all types of roofs: mastic, roll, metal, asbestos-cement, concrete, etc. In this case, repairs are carried out, as a rule, without removing the old roof, except for cases with roofing material, which has a large number of layers after numerous repairs, when clearing of the old carpet becomes necessary. The advantage of mastics is that the insulating layer is formed from one material in one working cycle using the simplest technological equipment..
Certain brands of modern mastics can be applied to damp or even wet surfaces. At the same time, high adhesion to all types of materials is maintained, which makes it possible to extend the construction season. They are also applied on a rusty metal surface without preliminary mechanical cleaning..
Mastics are especially advisable on combined roofs, because the roofing of such roofs is more susceptible to the action of water vapor rising upward and forcing the roofing to tear off. In this case, the roofing mastic provides increased reliability both due to strong adhesion to the cement-sand mortar of the screed or concrete of the roofing panel, and due to the vapor permeability of the film, which eliminates swelling.
The disadvantage of a mastic coating is that it is difficult to achieve a guaranteed insulation film thickness., especially on steep slopes and uneven surfaces. Therefore, it is necessary either to carefully prepare the surface, or to increase the consumption of material. Both of these lead to an increase in the cost of coverage.
But to date, mastics have been developed that allow you to control the quality and thickness of the coating, as well as minimize material consumption due to the use of an original method – applying mastic in two layers. First, apply the first layer of one color, and then the second one in a contrasting color. Moreover, the thickness of the applied coating of the second layer should be such that the first layer does not shine through.
The most famous mastic manufacturers: Bungalite roofing, Germoplast (Russia), ALCHEMICA (Greece).