What is concrete parging and when does it need replacing in NB?

Parging is a thin coat of cement-based mortar applied to the exterior face of a foundation wall, typically 1/4 to 3/4 of an inch thick, that provides a smooth, weatherproof surface over the rougher substrate beneath — whether that's poured concrete, concrete block (CMU), or stone. In New Brunswick, parging serves both an aesthetic and a protective function, but it has a finite lifespan and NB's climate is particularly hard on it.

Original parging on older NB homes was typically applied over stone or block foundations as a sealer to shed water and protect the masonry beneath from weathering. On poured concrete foundations, parging is sometimes applied to smooth the surface and create a base for dampproofing or waterproofing coatings. When you see a grey cement coat on the visible above-grade portion of a foundation wall, that is parging.

NB's freeze-thaw cycle is parging's primary enemy. Parging is a thin, relatively rigid coating bonded to a substrate that expands and contracts at a slightly different rate. Over 10 to 20 years of NB winters — 150+ freeze-thaw cycles per year — that differential movement causes the parging to develop micro-cracks. Water enters the cracks, freezes, and forces the parging away from the substrate in a process called delamination. You start to see chunks falling off, hollow-sounding sections when you tap the wall, cracks that follow the mortar joints of the block beneath, and eventually large sections failing entirely.

Signs your NB foundation parging needs replacing:

• Sections that sound hollow when tapped with a knuckle


• Visible cracks wider than a hairline, especially horizontal or diagonal cracks


• Pieces that are lifting, bulging, or have already fallen off


• Staining or efflorescence (white mineral deposits) appearing through the parging


• Any section that has been patched multiple times with visible colour differences

Parging that is only hairline-cracked and still firmly bonded can be patched and painted with a masonry sealer to extend its life another few years. But parging that is delaminating, hollow, or actively falling off needs to be removed completely, the substrate beneath cleaned and prepared, and new parging applied.

New parging in NB costs $5 to $10 per square foot fully installed — for a typical exposed above-grade foundation perimeter, that's often $500 to $2,000 depending on the size of the home and the amount of wall exposed. Parging should be done during the May to September window in NB — applying parging in cool or wet conditions dramatically reduces adhesion and longevity.

For parging replacement on your NB home, New Brunswick Concrete can connect you with masonry and concrete professionals in your area.