SCHMUTTERTAL GRAMMAR SCHOOL
Schmuttertal Grammar School’s four buildings stand in the landscape like large barns. The im- pression is reinforced by the simple facades made of rough sawn boards that seem to be untreated. But in fact, the silvery-grey wooden surface conceals plenty of work and know-how. The intention was for an appearance that looks as natural as possible. Treatment with a common wood coating was therefore out of the question. Most varnishes form a film on the surface which conceals the structure and grain of the wood. On the other hand, the wood should not be left completely up to its own devices because the natural greying process is usually very irregular, with sections below roof overhangs or window sills starting later than the rest of the facade. And so the decision was taken in favour of a glaze that would anticipate the greying process. Lignosil-Verano by KEIM seemed appropriate for two reasons. Firstly it is so hydrophylic and permeable to vapour that it leaves the natural characteristics of the wood almost unchanged better than any other glaze. This is a mineral system that forms a unit with the hygroscopic wooden substrate. As a result, the structure absorbs moisture. Together with UV radiation, this is an important prerequisite for triggering the natural greying process. In time, the grey in the glaze will diminish and be gradually replaced by the natural grey of the wood. Architects and product developers tested more than 50 different samples to find a colour shade that came as close as possible to this natural grey. The shade that was eventually chosen was still mixed individually at that point in time. It is now available as standard product number 4861. It has been used to cover the facade of spruce boards measuring roughly 5,000 m² in size. Furthermore, an absolutely biocide-free wood preservative was needed for the panelling. The glaze is designed as a sacrificial layer which is washed out little by little over time. Given the proximity of the building to a nature conservation area and the fact that the Schmutter (a stream) flows past just a few yards away, it was out of the question to use any glazes containing toxins, such as those added to numerous facade paints to prevent algae growth. During the planning phase, KEIM Lignosil-Verano was the only grey glaze available on the market that fulfilled the strict environmental requirements. Other reasons in favour of this product included its matt look and colour stability with no fading. It was the right decision: even after the building has been standing for three years, the facades show absolutely no signs of wear and tear. They are ageing gracefully.
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