As a rule, bricks have grooves in the surface so that plasters find sufficient adhesion. Since brick basement exterior walls must be waterproofed on the outside, these surfaces must be smooth to ensure a long-term bond with the waterproofing. In the case of brick masonry with plaster grooves, a thin or levelling plaster or a waterproofing slurry must be applied before the waterproofing is applied. In the case of basement flat bricks with smooth surfaces, the waterproofing can be applied directly to the brick wall.
Source: bauwion
