Repair of plaster with widespread hairline cracks.

Structure type

Existing plaster based on hydraulic binders with widespread “spider-web” hairline cracks caused by a heterogeneous and/or discontinuous substrate and/or differing thermal expansion of the substrate, by plastic or drying shrinkage of the mortar, or by uneven applied thickness.

Detail

Interior or exterior skim coat over plaster.

Application cycle

1. Standard plaster, class CS I – CS III according to UNI EN 998-1. Check its cohesion, strength and bond to the wall, and that it is clean and free of moisture, dust, residues of old poorly bonded paints or finishes, salt efflorescence, organic substances, oils, mold, etc.
2. If needed, RALLK Primer K as a surface fixative or consolidant on poorly cohesive existing plasters.
3. Skim coat over the whole wall surface with the all-purpose skim coat RALLK Rasante K or RALLK K OttO, with embedded 150 g/m² glass fiber mesh, laid from top to bottom with the vertical strips overlapping by at least 10 cm.
4. Finish with RALLK Raso K, through-colored on request, or alternatively with RALLK Marmo K troweled mineral finish, a finishing coat, powder mineral finish, acrylic, siloxane, lime or silicate paste finish, or lime, siloxane, acrylic or silicate paint, as set out in the specifications.

Additional information

1. Based on current site experience, a reinforced skim coat over cracked base plaster is an effective way to prevent the cracks from reappearing in the medium and long term as a result of minor settlement, vibrations or thermal expansion.
2. See the individual product data sheets for application methods and precautions.