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Published on 28 September 2016 00:00

Render Choice Depending on the Environment Conditions

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Key Learning outcomes
  • Introducing the importance of appropriate render choice.
  • Identyfying the factors which impact the buildings façades in the city center or on the city outskirts.
  • Understanding the correlation between wall structure and possible wall finishes.
  • Recognizing the difference between old and newly constructed buildings in terms of render use.
  • Matching the render colour to the particular building.
Introduction

Let’s be honest – there is no perfect render. A feature which forms an advantage of one render, in a different situation may be a serious drawback.
In order to select an appropriate render type one should consider numerous data. As long as there are no remarks on the use of a definite render type, the client can use any product they can afford. The most advanced thin-coat renders currently available on the market are the silicone and silicate ones. These products and their hybrids are most often 'general-use' and will do good in almost any conditions. Naturally, there are some limits which cannot be crossed even with the most advanced materials. The best example is the external insulation with mineral wool panels, where the rendering coat must be characterized by high vapour permeability similar to the whole partition and where only the mineral or silicone-silicate renders can be used. But, as long as the investor treats the appropriate cost level as the main selection factor, the supplier should select the materials providing the best solution for the best price. Please note that it is not advised, on the basis they meet the financial expectations of the buyer, to choose technologically improper products.

1.0 In the city centre or close to forests and water reservoirs

The house location influences the render choice significantly. If a house is placed close to a busy street or other source of dirt, then we recommend the use of ACRYLIC, ACRYLIC-SILICONE or SILICONE renders. These materials are the easiest to keep clean. Although, paradoxically, they get dirty faster than mineral and silicone-silicate ones (negative potentials attracting dirt and dust form on their surface), dirt does not penetrate their structure and is easily washed off. In case of acrylic-silicone and silicone renders minor contamination cleans itself with rain. This phenomenon results from their low absorptiveness commonly known as the “self-cleaning ability”. But, even if the dirt does not wash off itself, it is much easier to clean the acrylic or silicone renders, as their surface is scrub resistant. In comparison, mineral and silicone-silicate renders are absorptive and here not only surface, but also structural contamination occurs. This dirt type cannot be cleaned with standard procedures as they may lead to surface damage and the need for re-painting of the façade. If a house is located close to a busy street of significant heavy load traffic, the use of acrylic, acrylic-silicone and silicone renders is additionally justified - these render types contain polymers. They make the renders elastic and indirectly support the transfer of shakes resulting from the road traffic (the render will not crack).

If a house neighbours a forest or any other green zone, it is subject to organic contamination and façade greening. For such cases we recommend the MINERAL and SILICONE-SILICATE renders, which are strongly alkaline (pH~12) and effectively block microorganism development. Acrylic and silicone renders, although characterized by natural low absorptiveness, also contain organic ingredients which might support the development of fungi and moss. Of course, some of the renders on the market contain appropriately selected biocides limiting the microorganism growth, but still they might not be fully effective in case of large amount of fungi spores and high air humidity typical for green areas. Please note, that even the use of mineral or silicone-silicate renders does not eliminate the risk of organic contamination completely – constant contact with damp resulting, e.g. from improper flashing installation, will always lead to the façade greening. So, only proper façade maintenance and regular inspection can identify the potential problem and enable eliminating its effects at an early stage.
If a house is in a forest neighbourhood, or any other green zone, it is subject to organic contamination and façade greening. For such cases we recommend the mineral and silicone-silicate renders.
If a house is in a forest neighbourhood, or any other green zone, it is subject to organic contamination and façade greening. For such cases we recommend the mineral and silicone-silicate renders.
 
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