How to paint exterior facades

Since the beginning of building practice up to our days, the facing of the exterior facades has gained an important role for its protective and aestetic functions. First of all, the exterior coverings, gives the aestetic looks of the building, by capturing the sight or, on the contrary, by giving value the nearby context; furtherly they protect the building. The mural coverings satisfy the strong duty to preserve, within a long period of time, the characteristics of the supports to which they have been applied, by furnishing "a shield" to wet weather and natural and artificial external agents. It is commonly accepted that the quality of mural coverings is strictly linked to the compatibility between mural structure and coating solution: in order to find the best solution for your needs, it's important to value surface characteristic and way to apply primer and covering, following painting cycles suggested.

Characteristics of support

Who takes care to paint external facades, could find different problems, connected to type of support. In "Painting Cycles" we introduce supports, phenomena, problems, products and suggested treatments.

Preparation of underpainting

In order to improve the result of the work, it is essential to prepare the support with an underpainting, which places as interface between the support and the mural coating. It is useful to remind that you have to choose accurately the product you are going to use as underpainting: you have to know precisely the type and the composition of the support on which you are going to work and further, you have to decide previously the type of finishing you want to adopt; so you create compatibility within the logic of painting cycles, to which you have to conform.

Characteristics of a good external covering

The covering must adhere perfectly to the surface on which it is to be applied; moreover it must appear sufficiently elastic in order to resist to the expansions and the movement of the same support. Coverings have to sustain the minimal quantity absorption of water and, at the same time, they have to allow the evaporation of the water already penetrated previously. The most damages suffered by a covering are caused by water penetration. Water is rich of atmospherical pollutants, like acidic axide, carbon monoxide sulfur and nitrogen. Such chemical substances by becoming hard acids, react with a lot of alchaline elements which are present on the exterior facades of buildings. These reactions damage greatly the external surface of buldings, as well they cause erosion to the same surface. The presence of water, moreover, causes volumetric expansion, variations in diffusive capacity and flow of inner vapor, crackings and cleavages. The main characteristic of mural coverings is the ones fixed by DIN 4108/3 code: to be water-proofing and at the same time transpirant agents, as well to obtain dry surfaces and a great energetic saving. According to such code, the capillary absorption of water must be inferior to 0,5 Kg /Mq, (A factor), the resistence to vapour diffusion must be minor or equal to 2 m equivalent of air (B factor) and at last AxB must be inferior to 0,1.