What is parging?
Parging is a thin layer of cement or mortar spread over the interior or exterior of masonry surfaces like chimney flues and foundation walls to seal, smooth, and protect them.
Parging refers to the application of a thin coating of cement or mortar troweled onto the surface of masonry structures. The material fills small gaps, cracks, and irregularities in brick, stone, or block work. Inside chimney flues, parging seals the interior walls to improve draft and prevent smoke and gases from leaking through mortar joints into the home. On exterior foundation walls, it protects the surface from water infiltration and weather damage.
Masons apply parging by hand or spray, working the cement mix onto the substrate until it forms a smooth, uniform layer typically one-quarter to one-half inch thick. The coating bonds to the existing masonry and hardens as it cures. Over time, parging can crack or deteriorate from freeze-thaw cycles, settling, or age. When damage occurs, repointing or re-parging may be needed to restore the protective seal.
Property owners should have chimneys inspected regularly by chimney masonry professionals to catch parging failure early. Preventive maintenance and timely repairs extend the life of the chimney and foundation while keeping the home safe and dry.