Foundation parging repair for Jersey City homes and rowhouses

Parging is the thin coat of mortar troweled over the part of a foundation wall that shows above the ground. On a block wall it covers the joints and gives the face a smooth, even surface that sheds rain. On a poured wall it hides tie holes and rough casting marks. On older stone it evens out an irregular face. Its job is protecting that exposed band of masonry from splash, sun and frost, and giving the base of the house a finished look.

Parging fails mostly because water gets behind it. Rain splashing off a walkway, a downspout dumping at the corner, or soil and mulch piled against the wall keep the bottom edge wet. Water wicks into the masonry and freezes through the winter, pushing the coat off the wall from behind. It goes hollow first, sounding like a drum when you tap it, then it cracks, then it drops off in sheets.

Poor bond is the other cause. Parging troweled onto a dusty, painted or bone-dry wall never grips properly, and a coat laid on too thick in one pass cracks as it shrinks. Across the Heights and Greenville, two- and three-family frame houses often sit on block or poured foundations with a strip of parging that has been patched over the years. Each patch is a different mix, and the edges between them are where the cracks begin.

We start by tapping the whole parged band with a hammer to find every hollow spot, and we mark each one. Loose and hollow parging is cut back with a saw and chisel to a clean, solid edge, so the new coat butts against parging that still grips the wall. Where the coat is failing along most of a wall, stripping the band completely and starting fresh usually costs less over time than patching dozens of separate spots.

Then the wall gets prepared. Cracks in the block or concrete behind are opened and filled, spalled block faces are rebuilt, and the surface is cleaned and dampened so the new mix won't dry too fast. On poured or block walls we apply a bonding agent, then a scratch coat, then a finish coat once the first has firmed up. The new parge is damp-cured for several days, because cement-based mortar that dries quickly cracks.

The top and bottom edges matter as much as the coat itself. At grade we carry the parge a little below the soil line with a clean edge and pull the soil back so the wall can dry. At the top, where the foundation meets the sill or siding, we shape a small wash so rain runs off rather than into the joint. Where downspouts empty against the wall, underground leader drains remove the splash that started the damage.

Foundations under older rowhouses and brownstones, and under many frame houses built a century ago, are brick or rubble stone laid in lime mortar. Those walls move moisture out through the joints and let it evaporate from the face. A hard cement parge sealed over them traps that moisture. Salts collect behind the coat, the coat pops off, and it often pulls the face of the stone or brick away with it. Much of the flaking parging on old walls failed exactly this way.

On those walls we use a lime-based parge, mixed softer and more vapor-open than the masonry, applied in thin coats and finished with a breathable mineral paint or left natural. Before it goes on, washed-out joints are repointed, the same way our stone foundation work treats the wall from inside. The finish lets the wall keep drying outward, which is how it has stayed sound since it was built.

Parging is a finish for the exposed face, and it works alongside the below-grade side rather than replacing it. If your basement is wet along the same wall, the part under the soil needs drainage or a membrane, which our exterior foundation waterproofing page explains. On designated historic blocks the foundation face is part of the facade, and we tell you when a job will likely need Historic Preservation Commission review.

Most foundations in the city show on only one or two sides. On attached rowhouses the exposed band is often just the front wall under the stoop and the rear wall facing the yard, while the side walls of detached frame houses can sit a few feet from a fence or the house next door. We work those narrow strips by hand, stage mixing on the sidewalk or in the yard, and protect the stoop, areaway and plantings as we go.

Timing matters too. Cement and lime parge both need temperatures above freezing while they cure, and lime sets slowly, so we schedule exterior parging from spring through fall and cover fresh work against hard sun, wind-driven rain and early frost. On blocks facing the bays, such as much of Bayonne, salt air and steady wind dry a fresh coat quickly, so we mist it and keep it covered for longer there.