Wood is one of the oldest building materials known to humans – and is currently enjoying a renaissance. Take, for example, the Cedar House project in Stockholm, Sweden. With its 13 stories rising 43 meters into the sky, it will be the tallest building in the world to be made entirely from wood. Its facade of Canadian cedar makes a striking impression in Hagastaden's new high-tech quarter, yet blends seamlessly with the surrounding concrete and glass edifices.
Rediscovering a Construction Material
Theoretically, wood is the perfect building material: lighter than steel, but with the same load-bearing capacity, it is easy to process, has myriad uses and lends itself to industrial pre-fabrication. What is more, wood releases far fewer CO2 emissions than any other building material. Timber designs now account for some 16 percent of all detached and duplex houses in Germany, and they are also becoming increasingly popular for apartment complexes.
“There is nothing exotic about wooden constructions anymore – everything’s high-tech these days,” says German architect Tom Kaden, who has erected a seven-story apartment block with a timber frame and wooden walls in the trendy district of Prenzlauer Berg in the heart of Berlin.
However, the renewable raw material has one arch-enemy: water. “Not only do rain and moisture spoil its appearance, they also promote blue stain fungus, mold and insect attack – which can lead to irreparable damage,” explains Albert Hausberger, jointly responsible for the development of building-protection agents in WACKER SILICONES’ Applied Technology department.
Therefore anybody who uses wood outside should protect it with a suitable treatment. Chemical wood preservatives can be roughly divided into two classes: impregnating agents and film-forming coatings. Impregnating agents contain water-repellent components, such as waxes, resins and oils, as well as, occasionally, fungicides and insecticides. They penetrate into the wood, and due to their impregnating effect, protect it, as it were, from the inside out. Film-forming coatings work differently – they dry to form an intact water-repellent protective film. As well as binders and preservatives, these types of systems also frequently contain biocides, which protect against insect attack and mold. In addition, UV-absorbing pigments ensure that the wood does not turn gray in direct sunlight. Film-forming coatings typically include wood stains, paints and varnishes.