This specification covers brick made principally from sand and lime and intended for use in brick masonry. Two grades of brick are covered: grade SW - brick intended for use where exposed to temperature below freezing in the presence of moisture, grade MW - brick intended for use where exposed to temperature below freezing but unlikely to be saturated with eater. The brick shall conform to the physical requirements for the grade specified, as prescribed. All units shall be sound and free of cracks or other defects that interfere with the proper placement of the unit or significantly impair the strength or permanence of the construction.