Protection of wood from decay

Wood as a material of organic origin is a breeding ground for fungi and insects. The damage from the latter is significant, but incommensurate with the damage caused by mushrooms – the main “defendants” for the processes of wood decay that cause a lot of trouble.

Rotting wood can only occur when certain conditions are created: temperature – from 0 to 50 degrees. C, oxygen access, air humidity – 80–100%, the moisture content of the wood itself – at least 15–20%. The disclaimer when mentioning the temperature is not accidental: there are mushrooms that do not stop their growth even at a few degrees below zero.

Ideally, the fight against possible rotting of wood begins at the stage of production and storage of lumber. The moisture content of freshly cut wood varies from season to season, but on average is 60–80%, so it must be dried. The most affordable option is natural drying, which means not less than a year’s aging.

Special attention should be paid to constructive measures that prevent the joint effect of excessive moisture and freezing of wooden structures, a sharp change in temperature, moisture condensation, and insufficient air circulation. The protection of wood from atmospheric moisture is provided by a waterproof roof and painting with waterproof paints and varnishes, from capillary moisture – by appropriate waterproofing. Condensation humidification can be avoided by correctly placing heat and vapor insulating layers (the first is closer to the outer, i.e. cold surface, the second, on the contrary, closer to the inner, i.e. warm).

Of course, wooden structures must be based on foundations and located above ground level. Do not forget about groundwater drainage (drainage) and the installation of a blind area. Good ventilation of the wood contributes to the increase in biostability, which ensures its natural drying during operation. Therefore, it is advisable that large trees not grow near the house, creating shading and preventing aeration. A significant contribution to the prevention of putrefactive lesions of wooden walls can be made by covering them with boards. Especially from the ends, since the end cut is the “weakest point”, and moisture penetration occurs here much faster and deeper.

Thorough annual inspections of wooden structures contribute to the timely detection of decay. The best time for this is spring. The signs that determine the beginning of the destructive activity of fungi are: a change in the appearance of wood, the appearance of a characteristic odor and deformation of the building. If decay is detected, samples of damaged wood should be taken in order to find out its moisture content and density, as well as the type of fungus-destroyer.

As a result of decay, the physical and mechanical characteristics of wood change markedly. At 15% humidity, the density of rotten wood is 2–3 times less, and its hardness is 20–30 times lower than that of healthy wood. The ability of wooden elements to cope with the role of supporting structures depends on the density. And if foci of decay are found on the rims and at the same time there are distortions of window and door openings or movements of the outer and inner walls, it means that these rims no longer fulfill their functions..

Depending on the size and degree of damage to wood, a decision is made either to carry out a complete replacement of damaged structures, or to localize damaged areas in order to prevent further spread of the “infection”.

Localization means:

• opening of structures, if they were lined with any finishing materials;
• removal of the destroyed part of the wood using a carriage, scraper or hacksaw (all rotten wood is carefully collected and burned);
• antiseptic treatment.

The following antiseptic methods are available at home:

• diffusion (coating with pastes);
• superficial, i.e. antiseptic solutions applied by brushes or by spraying.

Antiseptic pastes consist of an antiseptic, glue and filler that provides the required consistency of the paste. So, bitumen paste is obtained by adding green oil, sodium fluoride and peat powder to molten bitumen. Silicate paste is a mixture of sodium silicofluoride, water glass and coal oil. Also used are extracts and clay-extract pastes based on sodium fluoride or fluorosilicate. When the moisture content of the wood is more than 40%, the antiseptic included in the paste dissolves and intensively penetrates (diffuses) into the wood. When humidity decreases, diffusion stops.

For antiseptic treatment of healthy wood, a 5% solution of potassium dichromate in 5% sulfuric acid is often used. They are advised to process not only wood, but also the ground to a depth of 0.5 meters. An effective means for impregnating beams and lower rims is an aqueous solution of potassium dichromate. The resulting chromium oxide reliably protects the wood not only from rotting, but also from damage by insect larvae.

In addition, a variety of off-the-shelf preparations are available on the market. The Senezh trademark is well-known, for example, Senezh Bio and Senezh Ognebio. The latter is a biopyrene, that is, it acts in a complex way, providing protection from both biological damage and fire. Antiseptics-fire retardants Antibiokor-S, VIM-1, Pirilaks have the same qualities. Biodecor, Kram, Biosept, Biotonex, Tecotex, Novotex, Biocron, Quintol, Actitox, VAK-48D, a mixture of boric esters Aquabor, an analogue of the famous Pinotex – Novotex, also prevent the occurrence of putrefactive processes. In the arsenal of the same Pinotex – a number of antiseptics: primer PINOTEX BASE, wood preservative based on alkyd binder PINOTEX CLASSIC, water antiseptic for indoor and outdoor use PINOTEX AQVA PLUS.