Brick is porous. When water freezes, it expands. Put these two together and you have a recipe for surface spalling and freeze-thaw weathering. Freeze–thaw weathering is caused by moisture freezing inside masonry and then later contracting. Upon freezing, the water expands, causing spall,
Rustication is a range of masonry techniques giving visible surfaces a finish that contrasts in texture with the smoothly finished, squared-block masonry surfaces called ashlar.