Fosroc Renderoc CS Non-Shrink Crack Sealer for Concrete and Masonry Walls (1 Box-12 Pcs)

A crack in a concrete or masonry wall isn't the same problem as a hairline in soft plaster. It sits in a hard, structural surface, and whatever you seal it with has to bond to that surface, resist shrinking back as it cures, and hold without sagging even on a vertical or overhead face. Plenty of fillers shrink a little as they set, which opens a fresh hairline along the edge of the repair within weeks. Fosroc Renderoc CS is a single-component cementitious crack sealer made for this exact work, curing non-shrink so the seal stays tight instead of pulling away from the crack.

It comes as a powder you mix with clean water on site into a smooth paste, so you set the consistency for the job in front of you. The crack is opened into a shallow V-groove first, then the mixed material is worked into the groove by hand and brought flush with a putty blade or a damp sponge. It sets quickly, bonds firmly to the substrate, and once it has cured you can paint over it with normal coatings.

Because it's non-sagging, the same material handles horizontal, vertical and overhead cracks, which makes it practical for wall crack repair anywhere on a structure, including the awkward overhead and vertical faces a sagging filler can't hold. It seals cracks in plaster, masonry and concrete, so it covers everything from a settlement crack in a plastered wall to concrete crack repair on a structural surface.

When a crack in a wall needs a proper cementitious seal, Fosroc Renderoc CS fills the groove, holds without shrinking, and takes paint cleanly afterwards.