White cement is not recommended for such applications since it is not flexible. You may need to remove the existing white cement and fill the joints with a product, which contains polymer, is best suited for such applications. FAIRFIX TG contains polymer, which makes it very flexible, doesn?t crack and adheres to the surface effectively. It is available in different shades to match your tiles. FAIRFIX TG is powder form and had to be mixed with water to achieve a paste consistency (3 part FAIRFIX TG: 1 part water)

Seepage through parapet wall occurs due to improper slop of the top surface or cracks. Remove old plaster /coping from the top surface of parapet wall. Clean the surface thoroughly. Add FAIRCRETE RMW into the cement mortar @ 150 ml per 50 k of cement and apply on the top surface of parapet wall giving a proper slope towards terrace slab. The next day fix a cudappa stone with FAIRFIX TA on the top surface of the parapet wall.