Pressure impregnated wood is used outdoors in terraces, garden furniture, garden construction and as a fence post because of its durability. In pressure impregnated wood, the preservative has penetrated through the surface layer prone to rot. The treatment with the protective agent is carried out under reduced or high pressure.
Nowadays, pressure impregnated wood contains only copper-containing wood impregnants, as wood treated with arsenic and chromium impregnants is no longer sold to consumers. Impregnated wood lasts 3-5 times longer in outdoor use than unsaturated wood. However, impregnation does not protect the wood from greying caused by the sun’s UV radiation, so tinted oil is recommended for better UV protection. Impregnated wood is usually greenish, but there is also brown-dyed wood on the market.
In terms of durability, the treatment of pressure impregnated wood is not necessary. However, treatment with oil, for example, enlivens the surface, reduces wood sticking and cracking and facilitates surface cleaning.
The new pressure impregnated wood is usually too wet for treatment in the first summer (when installed), so it is recommended to wait until next spring. The moisture content of the wood must be max. 20 %. Re-treatment should be done every 1 to 3 years, depending on the utilization rate and location.
If you are looking for a grey finish, it is a good idea to allow the wood to turn grey for 1-2 years without treatment. You can then treat the wood with transparent wood oil or wood preservative. In any case, the most important maintenance is regular cleaning of the surfaces. This helps wood remain beautiful and smooth for a long time.