Ceresit CR 90 adheares to load-bearing, solid and clean surfaces, free from any substances that decrease adhesion (such as grease, bitumen, dust), namely: – Concrete with a minimum class of C 12/15 (over 3 months old), – mineral plasters (cement, cement-lime) with the thickness of >10 mm and cement screeds (strength >12 MPa, over 28 days old) – brickwork with full-joints, and the strength of >6 MPa (over 3 months old). Surfaces must be smooth, absorbent and porous. Dirt, existing layers of low resistance and all previous paint coverings, lime plasters, and substances that impede adhesion must be carefully removed . Corroded joints should be removed up to the depth of 2 cm and refilled with cement mortar. Deep holes and uneven substrates should also be repaired with cement mortars or concrete. The edges should be chamfered to approx. 3 cm, whereas corners should be rounded (with the cement mortar or CX 5 mixed with sand) to a radius of least at 4 cm. CR 90 requires the pre-wetting of the substrates before application to the mat-wet conditions (without puddle formation).