Sentence:  When more than one unit thick of brick or tile is used in the wall, the back of the face brick or tile may be covered with mortar. This <WSD>parging</WSD> will substantially increase the waterproofing of the wall. Basement walls usually are parged. 
Meaning of the word marked with <WSD> tags:  A coat of cement mortar on the face of rough masonry, the earth side of foundation and basement walls; a parge.