Wood house processing: fire protection of wooden structures

Recommendation points

• Purpose of application
• Operating principle
• Composition differences
• Main characteristics
• Famous brands

The service life of wooden structures depends not so much on the quality of the wood itself, but on its correct processing. Unlike surface coatings, impregnations affect the structure of the material, which is especially important for capital structures and facade decoration.

Purpose of application

With its availability, strength and ease of processing, wood has a number of disadvantages. First of all – flammability, which limits the use of wood products in places with a potentially increased risk of fire. Because of this, wooden facades located close to other buildings must necessarily be treated with substances that make them difficult to ignite and burn..

The worst enemy of wood is fire, as wood is highly flammable

Another flaw in wood is that it serves as an almost ideal habitat for insect pests and pathogens. Because of this, there is a high risk that over time, wooden structures will greatly lose their strength and attractiveness of appearance, while damage to the structure of the wood contributes to an even greater acceleration of destructive processes. Such negative effects can be eliminated by treating wood with bioprotective compounds that are poisonous for harmful organic matter, but safe for people and the material itself..

Bark beetles in a wooden house

If we talk about wooden houses and finishing the facade with natural wood, processing with protective compounds is strictly required. Firstly, high durability requirements are imposed on wooden facades, because it is quite difficult to replace such a finish. Secondly, wooden walls are a factor of increased fire hazard and, in addition, serve as an important component of thermal protection, and therefore their condition directly affects the safety of living and the cost of maintaining a house. Thirdly, the elements of the wooden facade have a protective and decorative coating only on the front side, which does not provide the proper degree of resistance to moisture, microorganisms and erosion..

A wooden blockhouse affected by a fungus

Operating principle

All compositions for the protective treatment of wood can be divided into targeted and complex agents. In addition, various impregnations have a different principle of action during not only operation, but also processing, that is, they differ in the rules of use.

Fire protection is the main and obligatory type of processing for wooden facades. The primary effect of such compounds is the absorption of a significant part of the thermal energy, which is spent on the decomposition of chemical compounds. A secondary effect can be the release of gases that displace oxygen, the formation of a non-combustible film or foaming, which blocks the access of fire to the wood. The practical benefit of fire retardant impregnations is that the wood treated by them is charred under the influence of fire, but does not support combustion.

Fire retardant treated wood does not support combustion

Bioprotective compounds are antiseptics that prevent the reproduction of pathogenic microflora in the pores of wood. A separate type of biosecurity ensures the resistance of wood to eating by insect pests. In the simplest case, the impregnation mineralizes the fibers and makes them unfit for food. The addition of insecticides to the composition of the impregnation provides its poisonous effect, which is why such agents can only be used to treat facades and hidden wooden structures that are not in contact with the internal air.

The combined action of protective impregnations simplifies handling, but the effectiveness of multipurpose formulations is often questioned. In turn, the separate use of directional protective agents is hampered by a decrease in the ability of the tree to absorb the composition with each subsequent application. It can be recommended to use penetrating antiseptics at the first stage of processing, and then cover the wood with fire retardants that settle in the surface layers..

Composition differences

All impregnations can be divided according to the type of base into water-soluble and organic solvents. The latter type has a greater penetrating ability, however, such means are used mainly during soaking and autoclaving, where, due to vacuumization, impregnation of products is ensured to the full depth. At private construction sites, it is most preferable to use salt and salt-free water-based impregnations.

Salt formulations have a tendency to re-dissolve and therefore gradually go out of circulation. Due to the tendency to decomposition in the air, such protective agents only work effectively for 3-5 years, after which re-treatment is required. In addition, salt impregnations impair adhesion and make it impossible to apply surface film-forming protective coatings.

Salt-free formulations have organophosphorus substances as active components that have the properties of both insecticides and pesticides, and fire retardants. The main feature of such impregnations is considered to be their tendency to chemically modify wood, due to which stable compounds are formed that provide comprehensive protection of wood for 15-20 years.

Main characteristics

It is rather difficult to establish the real effectiveness of bioprotective impregnations for several reasons: it is difficult to determine the used set of active substances, their concentration, the ability of the composition to penetrate deeply into the structure of the tree. In addition, harmful organic matter is quite diverse, so all compounds work differently with wood of different origins. In this matter, it is better to focus on the manufacturer’s reputation and the real experience of using specific products..

In contrast to bioprotective, the effectiveness of impregnations to increase the fire resistance of wood is determined by specific criteria. There is a concept of a group of fire protection, which is achieved by the use of fire retardants: the first group includes hard-to-burn wood, the second – hard-flammable wood, which, under equal combustion conditions, loses no more than 9% and 25% of the mass, respectively.

The possibility of achieving the qualities of a certain group is indicated by the impregnation manufacturer. In this case, a certain method of application and the number of processing cycles can be set. Also, depending on the consumption rate, the amount of active substances that are applied per unit of covered area is taken into account..

Famous brands

Compounds for biological protection and wood preservation are the most common. Among them, the impregnations “Senezh” and “Zelest” have become very popular, representing a whole series of various water-based formulations, both directed and combined action. These brands belong to budget funds for wood processing, cheaper formulations do not have any pronounced effectiveness..

Among impregnations based on organic solvents, we recommend the series of Neomid and Pinotex products, as well as products from other popular manufacturers of paintwork materials: Dufa, Caparol, Tikkurila and others. These formulations have a high concentration of active ingredients and can be used not only as a preventive measure, but also for treating mold and fungus affected wooden structures..

Among fire retardant impregnations, the largest number of positive reviews are met by the products of Senezh, Caysar, Neomid and WoodMaster. All these compositions are well suited for imparting the first and second groups of fire resistance, the only question is the amount of funds that need to be spent to ensure refractory properties. It is noted that almost all compositions costing from 400 rubles / kg cope well with the task of fire protection for outdoor use. You can increase the resistance of a wooden facade to fire by covering it with fire retardant paint or varnish. Such products are represented by the Pirex and Neomid trademarks, as well as by other manufacturers of paints and varnishes based on liquid glass..