The implementation of a flat roof can be carried out without the use of rolled materials, using various mastics for this, such as hot bituminous roofing mastic - GOST allows this. This article will discuss the main types of roofing mastics and how to use them.
Bituminous roofing mastic is an artificially prepared mixture of astringent organic substances and various mineral additives and fillers.
If we consider the physical characteristics - hot bituminous roofing mastic is a waterproofing plastic material in the form of a dispersed system with mineral filler particles of different sizes.
Classification of waterproofing and roofing mastics
There are the following types of mastics in accordance with the type of binder: tar, bitumen, bitumen-polymer and rubber-bitumen.
The filler for such material as bituminous mastic for roofing can be:
- Asbestos and asbestos dust;
- Mineral short-fiber wool;
- Fine sheet pulverized powders of limestone, quartz, brick, etc.;
- Combined ash or resulting from pulverized coal combustion of mineral fuels.
Fillers are used to improve the following characteristics that cold bituminous roofing mastic should have:
- Density;
- Hardness;
- Reduced brittleness under the influence of low temperatures;
- Reducing the specific consumption of the binder.
In addition, fibrous fillers make it possible to reinforce the material, increasing its resistance to bending.
Bituminous roofing mastic can be cured and non-cured according to the method of its curing.
In addition, roofing mastics are distinguished by the type of thinner:
- Mastic bituminous roofing containing water;
- Mastic containing organic solvents;
- Mastic containing organic liquid substances.
In the air, all types of mastics harden within an hour, forming an elastic, smooth surface that is resistant to various atmospheric influences. The positive characteristics of roofing mastics include water resistance, good adhesive ability and, in some cases, biostability.
There are also certain requirements that bituminous roofing mastic must comply with - GOST and other regulatory documents regulate the following standards and requirements:
- The structure of the mastics should be homogeneous, it should not contain filler particles and impregnation with binders;
- Roofing mastics should be conveniently applied without releasing harmful substances into the environment in quantities exceeding the permissible ones;
- The heat resistance of mastics should be at least 70 degrees;
- Bituminous mastic roofing hot or cold must be waterproof and biostability;
- Bonding of rolled materials with mastics must be strong enough.
In addition, according to GOST, roofing mastics must have a sufficient service life and stable physical and mechanical parameters when operating in the declared temperature range.
The procedure for applying mastics to surfaces subjected to insulation is carried out in several stages:
- The surface is coated with thinned emulsion bituminous paste as a primer;
- Cover the surface with the main layers of emulsion bituminous mastics, while the number of layers is selected depending on the angle of the roof;
- On top of the reinforcing mastics, an additional layer of mastic is applied, which reinforces the mastic carpet in those places where moisture most often accumulates;
- A layer of protection is applied, for which cladding, coarse sand, gravel or surface painting is used.
Composition and characteristics of bituminous mastics
In the manufacture of bituminous mastics, artificial bitumens are used as binders, for the production of which oil and its resinous residues are processed. Petroleum bitumens are black or dark brown substances, the viscosity of which changes when heated.
According to the degree of viscosity in construction, the following types of oil bitumen are used:
- In the manufacture of materials for roofing and construction work, such as roll materials, bituminous varnishes and mastics, semi-solid and solid petroleum bitumens are used;
- Liquid petroleum bitumen is used to impregnate roofing roll materials.
Before using bitumen, you should correctly choose its brand, which is set in accordance with its main properties, such as:
- Viscosity;
- Extensibility;
- softening temperature;
- Flash point.
Bituminous mastics consist of filler, solvent and various additives. The main difference between polymer, bitumen and bitumen-polymer mastic for the roof from roll materials is that mastics form a coating in the form of a film or membrane on the roof surface, which has the same properties.
In addition, various types of mastics, for example, bitumen-latex roofing mastic, can be used as an adhesive when laying rolled roofing materials, both during the construction of a new roof and during the repair of an old one, regardless of the type of roof structure.
It is also important that bituminous mastics can be painted in any desired color by adding dyes both in the production process and directly in the process of applying them to the roof.
Bitumen-latex roofing mastic can be painted in the color most suitable for the overall style of the house. For this, anhydrous dyes are used, the pigment content of which should be as high as possible.
Most often, modern mastics can be used without preheating them (cold bituminous roofing mastic).
Depending on the composition, there are two main types of bituminous mastics:
- Solvent-based one-component mastics are ready-to-use products that cure by volatilization from the solvent mixture. These mastics are supplied in sealed containers to prevent premature curing of the material, and their shelf life is quite limited, usually no more than three months, with the exception of polyurethane mastics, which require airborne water pores to cure. Due to the absence of a solvent, the curing (polymerization) of polyurethane mastic is not accompanied by shrinkage, and its shelf life in a sealed container is 12 months.
- Two-component mastics are supplied in the form of two low-residue chemical compositions, which separately have a shelf life of more than 12 months, which is a significant advantage, allowing you to stock material in advance for roofing work.
Useful: despite the fact that one-component mastics have a much shorter shelf life, modern formulations retain proper quality also for a fairly long period of at least 12 months.
The operational characteristics of the roof, which was covered with bituminous roofing mastic, largely depend on how correctly the work was done to prepare the mastic directly at the construction site, as well as on the quality of its application to the base.
In this case, one-component mastics have a certain advantage, since they are already ready for use and can be used for coating immediately after opening the container.
If a two-component bitumen-rubber roofing mastic is used, it is necessary to first prepare the mixture, and only then proceed with its application to the surface to be coated, which requires much more careful adherence to the technology.
At the same time, the use of a two-component mastic also has its advantages: in the process of its preparation, the composition and properties of the resulting material may vary depending on the specific situation.
Various properties of two-component mastic, such as hardness, color, viscosity, etc. can be changed during preparation by introducing special additives, unlike one-component mastics, the properties of which can only be changed by changing the type or brand of mastic used.
The strength of mastic-covered roofs can be further increased by reinforcing with glass mesh or fiberglass:
- Fiberglass mesh is a network woven from high-strength glass fibers. For reinforcement, fiberglass meshes with different thread thicknesses and mesh cell sizes are used;
- Fiberglass is a panel made of randomly arranged fiberglass.
Both materials are characterized by high mechanical strength, which made them so popular in the manufacture of reinforcing gaskets.
Important: when reinforcing, not only the strength increases, but also the elasticity of the mastic coating decreases, so you should choose the most optimal option for a particular roof. In addition, only individual nodes should be reinforced, most often these are mates and junctions.
Also, a rather important positive characteristic of such roofing materials as hot bituminous roofing mastic is that there are no various joints and seams in the resulting roofing carpet.
Applying mastic
Roofing bituminous mastic can be applied both mechanically with an air sprayer, and manually - using rollers or brushes.
Both methods of application are quite technologically advanced and allow you to perform roofing work quite quickly and simply, regardless of the configuration and angles of the roof slope. This is especially evident in the construction of roofs, which have many elements such as various nodes and junctions.
For covering pipes, shafts, load-bearing structures, etc. with rolled materials. on the roof you have to spend time cutting pieces of material of rather complex shapes, while mastics are applied to them in the same way as on a regular flat surface.
Mastics can be used to cover almost any type of roof:
- mastic;
- Roll;
- metal;
- Asbestos-cement;
- Concrete, etc.
When repairing with mastic, removal of the old coating is not required, except for roofs with a large number of layers of roofing material. In addition, one working cycle is sufficient to form an insulation layer using this material.
The main disadvantage that the mastic coating has is the difficulty in obtaining the required thickness of the insulation film, which is especially noticeable at significant slope angles and on uneven surfaces.
In this regard, the cost of coating increases, since the surface must either be carefully prepared or the material costs increase.
Nevertheless, modern mastics make it possible to apply a high-quality coating of the required thickness, and the consumption roof material can be reduced by applying two layers of mastic, the colors of which contrast with each other. In this case, the second layer should be applied so that the first layer of the coating does not shine through it.
The use of bituminous mastics for roofing can significantly simplify and speed up the work and give the roof the appearance that was intended during its design. The most important thing is to choose and apply the mastic correctly and it will last a long time and reliably.
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