Moisture Protection

Higher moisture content in the wood is a crucial factor inducing mold that shape and dimensional changes. Reducing the tendency of the wood to absorb water from rainfall or humid air can indirectly prevent such fungus.

Wood impregnated with protection agents can be surface-treated in the same way as non-impregnated. One exception is the creosote-treated timber, which is unsuitable for painting surface.

Moisture protection can be carried out partly to provide a temporary, short-term protection, and with methods that give a more long-lasting and effective protection.

Short term moisture protection

Water repellent treatment - with wax in Sweden has a certain, very limited use of structural timber for building. Treatment rejects splashes and brief rain but does not prevent absorption from humid air. The purpose is mainly to reduce the risk of excessively damp timber built into the structures of houses. Sale of sawn timber in Canada with similar treatment is regarded as "rain-guarded".

Some wood products such as panel boards, laminated wood and windows are treated in the factory with a so-called transit protection. This is mainly aimed to provide a temporary shelter for humidification during transport and storage. The treatment may consist of a base oil or base color. It does not replace full priming.

Surface treatment with tung oil gives a temporary water repellent finish. Wood outdoors as we do not intend to paint like the exterior stairs and decking can be regularly treated with tung oil to prevent drying, water absorption, cracking and discoloration. The treatment should be done as soon as possible when the wood is new. The most common type of wood oil for exterior wood is based on alkyd oil, usually the solvent cage. Different fungicides can be added to counter the superficial fungus.

Long-lasting moisture protection

Most finishes for exterior wood gives a more or less lasting moisture protection. Finishing with solid color usually covers a system of different treatments where each has its function. Priming is to reduce moisture absorption, stabilize the surface of the wood and provide good adhesion for the next step in the treatment system.

By adding large amounts of wood oil, a much more long-lasting and effective moisture protection can be achieved with superficial coating. Most commonly, any vegetable oil, primarily linseed oil, is added undiluted. Heating lowers its viscosity and gives the oil greater penetration and a high uptake. Impregnation with vacuum or pressure provides further higher uptake. Wood raised its own weight equivalent to the penetraed oil can hardly absorb any water at all, but the appearance is also greatly changed.

Try with pine oil impregnation has for years been running in Finland but has not led to any real commercialization yet. A corresponding treatment, enhanced with the addition of fungicides, is conducted on a larger scale in a new factory in Denmark, the impregnation with supercritical carbon dioxide as a carrier. Another combination therapy known as the Royal impregnation is a two-step process. The wood is first impregnated with a salt-medium preservative against rot, then with oil, usually pigmented. The method has since the 1970s been used mainly for timber windows.

Pine tar is extracted from the stumps and is used in some contexts as a vapor barrier on exterior wood surfaces, such as shingle roofs.


 
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