Characteristics and rules for applying roofing mastic

The installation of the roof is an important step in the construction of the house. With the advent of a variety of roofing materials on the construction market, this process becomes more progressive and interesting. One of these materials is roofing mastic. It is used in the repair and installation of roofs not only as a reliable waterproofing material, but also as an independent roofing. It can successfully replace rolled materials for the roof, is distinguished by its affordable price, acceptable characteristics, ease of application. To choose the optimal coating for a particular building, you need to familiarize yourself with the varieties of roofing mastics, their properties, application rules, etc..


  • Roofing mastic – its composition and operational properties
  • Varieties of roofing mastics
  • Basic rules for applying mastic


Roofing mastic – its composition and operational properties

Roofing mastic

Roofing mastic spreads freely in a thin layer on the roof surface, forming a protective monolithic membrane

Mastic for roofing is an artificial material, which consists of a mixture of binders with mineral additives and various fillers (mineral wool, asbestos, cement, ash, quartz, lime). Fillers provide surface hardness during solidification, its stability during temperature fluctuations. Often mastic contains herbicides and antiseptics. A homogeneous viscous mass is easily poured onto the roofing surface, forming after solidification a monolithic membrane that protects the roof from weathering.

The mastic and roll roofs are in many respects identical in their properties, but the priority of the first is its seamlessness. Depending on the composition, roofing mastics are one-component and two-component.

Roofing mastic

One-component mastics are not stored for long – no more than 3 months, so they are delivered in sealed metal containers

One component mastics are solvent based and are ready-to-use products. As the solvent evaporates, they solidify, therefore, in order to avoid premature hardening, they enter the distribution network in sealed containers. Such mastics are not stored for long – about 3 months. The exception is polyurethane mastic (there is no solvent in it) – it is stored for 12 months or more.

Two-component mastics consist of 2 chemical compounds with low activity, which are stored separately for more than a year, so they can be purchased in advance.

Mastic coatings are characterized by the following positive properties:

  • a light weight;
  • high strength;
  • elasticity;
  • weather resistance;
  • resistance to ultraviolet;
  • corrosion resistance.

In order for the mastic to be distributed evenly, the roof surface must be flat, therefore it is used mainly on flat roofs.

It’s important to know! If the angle of the roof is more than 12 degrees, and the ambient temperature exceeds 25 ° C, then you need to increase the viscosity of the mastic by adding thickeners to it.

Mastic roof

The absence of seams and joints is the main advantage of the mastic coating

If necessary, change the color or viscosity of the mastic, you can add special fillers to it. They are also added in order to increase hardness and heat resistance, reduce the fractional consumption of binders, reduce the brittleness of the material at very low temperatures, increase bending resistance.

Roofing mastic

Modern mastics can be given the desired color by adding filler with the appropriate pigment

The main advantage of a roof covered with mastic is the absence of seams and joints on it. Another plus of roofing mastic is its elasticity, which allows you to maintain the tightness of the roofing when the roof is deformed. But in order to create a uniform mastic cover, it is necessary to ensure a perfectly even surface of the base or to increase the consumption of material. But the first and second leads to an increase in the cost of coverage. Sometimes it is impossible to achieve a uniform thickness of the mastic layer, and this fact is considered its disadvantage. But for such cases, there is a special technology for its application in two layers. The first layer is applied in one color, and the second in a different, contrasting color. The second coating layer must be so thick that the first layer is not visible through it..

Varieties of roofing mastics

Mastics for roofing are classified as follows:

  • as intended – anticorrosion, roofing and insulation, gluing, waterproofing and asphalt;
  • in composition – one-component and two-component;
  • by type of binder – bitumen-polymer, polymer, bitumen-latex, butyl rubber, chlorosulfopolyethylene;
  • by the method of use – cold and hot;
  • by curing method – curable and non-curable.
  • by type of solvent – with a water content based on organic solvents or liquid organic substances;

Currently, the most common are hot roofing bitumen mastic and bitumen-latex roofing mastic.

Mastic bituminous roofing hot

Hot bituminous roofing mastic is convenient for the device of tight adjoining of the roofing carpet to pipes, ventilation wells

Mastic bituminous roofing hot  It is an astringent composition of roofing bitumen, modified by polymers and mineral filler. Before application, hot bituminous mastic is heated additionally to + 150 ° C. It perfectly combines with other building materials, creating a durable roofing system with endurance to various influences and is used for waterproofing, repairing roofs, devices for joining a roofing carpet to pipes, funnels, ventilation wells. There are a number of requirements that must be met by hot bitumen mastic – GOST and other current standards define their list as follows:

  • the structure of the mastic should be homogeneous (without extraneous fractions);
  • heat resistance – not less than + 70 ° C;
  • mastic should be environmentally friendly (do not emit toxic substances);
  • in a heated state it must be fluid, so that it spreads freely in a thin layer on the roof surface;
  • have good adhesion to horizontal and inclined surfaces;
  • should not crack upon hardening.

Mastic bitumen-latex roofing It is a mixture of original and synthetic binders, various additives and mineral fillers. The binders in it are latex and bitumen, and fillers – asbestos, mineral wool, various powders. This type of mastic is used in the repair of roofs for gluing various roll materials for roofing, as well as an independent strong waterproof coating.

Note. There are many types of roofing mastics, but in order to choose the right one, you need to take into account the peculiarities of the roof structure and the conditions of its operation.

Basic rules for applying mastic

Application of bitumen mastic

Mastic is applied on a pre-cleaned surface from dust and dirt.

Bitumen roofing mastic is applied without removing the old coating, unless there are a large number of rolled materials on the roof that were laid during numerous repairs. They do not allow the application of mastic even and thin..

The surface of the roof must be pre-cleaned of debris, dirt and dust. Apply mastic in the cold way or with preheating using a roller, brush or spatula. The number of layers will depend on the slope of the ramp and the presence of bumps. The most commonly used two-layer coating.

Attention! If the angle of inclination of the roof slope exceeds 25 degrees, it is not recommended to use roofing mastic.

The thickness of the layer is usually 1 millimeter and it dries in 24 hours. When applying several layers, the drying time will be 1-7 days. If the mastic is applied on a flat surface, the material consumption will be approximately 1.3 kg / m2.

In the cold season, it is recommended to heat the mastic to 50 degrees before application, so that it sticks to the surface better, and in order to give optimal performance properties, the mastic coating is sprinkled with roofing powder.

Reinforcing fiberglass mesh for mastic roofing

The reinforcing mesh improves the strength characteristics of the mastic coating

The best way to increase the strength of the mastic roof is to reinforce with a fiberglass mesh or fiberglass cloth. The use of these reinforcing elements is justified, since they themselves have high strength.

It’s important to know. With additional reinforcement of the mastic roof, its strength increases, but the elasticity of the coating decreases.

Roofing mastic is used to repair roofs of any type – metal, concrete, rolled, asbestos-cement, mastic.

Although the construction of a mastic roof seems simple, it is better to entrust this work to people who have rich experience behind them and who know all the subtleties of this matter. After all, the slightest mistakes and inaccuracies made during the arrangement of the roof with mastic can turn into serious problems in the future.


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