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MultiGips Putzuntergründe

Assessment and pre-treatment of backgrounds 

Generally it applies: the background must be absorbent, firm, dry and free of frost. the temperature of the rendering base and the ambient temperature my not be below + 5°C. Before the start of work in every case dust, loose or brittle parts of the background, lime precipitation, blistering, remains of shuttering as well as a possible sinter skin are to be removed. 


It many cases a dry, brisk brushing with a broom or steel brush suffices When wet cleaning is necessary it must be waited until the background has dried out again before applying the plaster. If, despite these preparations, no suitable background conditions can be produced, no rendering work may be carried out If required considerations of this problem are to be communicated to the building owner or his representative in writing. This applies in particular with:

  • severely contaminated backgrounds, e.g. sooty or oiled-up surfaces 
  • extremely uneven backgrounds, whose tolerances to not meet DIN 18202 
  • absence of load carrying capability of the background 
  • frost in the background or in the structure generally  
  • too high structural moisture in the background or in the structure generally.

Absorbent capacity of the background

Central significance for the bonding strength of the plaster is the absorbent capacity of the background. It may be neither to great or too small in order that the process of scratching, which is responsible for the particularly high bonding of all MultiGips plasters, can take place without hindrance.

Scratching

A too heavily absorbent background removes the water too rapidly from fresh gypsum mortar which then is no longer available for the bonding process. The so-called deflagration of the gypsum takes place which is associated with loss of strength. Extremely absorbent backgrounds are therefore pre-treated using MultiGips Grundiermittel or MultiGips Aufbrennsperre which provide for an optimum absorbent behaviour of the rendering base. Extremely absorbent wall creators can be, for example, porous concrete or porous brick.

Weakly absorbent background  

A weakly absorbent background has no or only very few pores in which the gypsum plaster can claw into. The case which occurs most often in practice are very smooth weakly absorbent concrete surfaces. The mechanical bonding of the plaster is improved here through a pre-treatment using MultiGips Betonkontakt. With wet concrete surfaces the pores of the background are filled with water which is why the gypsum cannot penetrate and claw in there. Therefore, for an optimum bonding with rendering work, one has definitely to wait for a sufficient drying.