Foundation parging and repair in Moncton

This page covers the mortar coat on poured concrete and concrete block foundations. Fieldstone and brick foundations need a different, lime-based approach; see stone restoration. Parging is not basement waterproofing (see the questions below).

What parging does

Most houses in Greater Moncton have a poured concrete or concrete block foundation with a strip showing above the ground, usually somewhere between a few inches and a couple of feet. Parging covers that strip. It gives the foundation a finished look, hides form marks and block joints, and adds a layer of protection against water, splash and salt. It is not a structural repair and not a waterproofing membrane, but it is the first thing weather hits.

Why parging fails

Parging is one of the most common masonry repairs in New Brunswick, because the foundation strip takes punishment from every direction: rain and roof runoff from above, snow piled against it all winter, salt from the driveway, and moisture coming up from the soil. Common causes of failure:

• Poor bond. Parging applied to smooth, dusty or oily concrete, or without a bonding agent, never grips properly. Water gets behind it, freezes and pops it off in sheets.
• Applied too thick in one coat, or allowed to dry too fast, which causes shrinkage cracks.
• Frost and moisture from behind, especially where soil, mulch or snow sits against the wall above the bottom of the parging.
• Water from above: downspouts dumping at the foundation, missing gutters, or siding and flashing that drain onto the parging.
• Cracks in the foundation that telegraph through the parging.
• Salt from driveways, walkways and steps.

Signs it’s time to redo it

• Parging that sounds hollow when tapped, even where it still looks intact
• Pieces falling off, exposing bare concrete or block
• Spiderweb or map cracking across the surface
• Bubbling, blistering or flaking paint on parging
• Crumbling along the bottom edge near the soil line
• Rust stains or exposed rebar on poured walls, which should be looked at

Patching small areas is possible, but if large parts sound hollow, the rest usually isn’t far behind. Removing all the loose material and redoing the wall gives a more even, longer-lasting finish.

How we parge a foundation

1. Dig down. We dig back a few inches below grade so the new parging extends slightly below the soil line rather than stopping at it.
2. Remove failed parging. Loose and hollow material is chipped off down to sound concrete or block.
3. Repair the wall. Cracks are routed out and filled; spalled concrete is patched; exposed rebar is cleaned and treated.
4. Prepare the surface. The wall is cleaned, roughened where it’s smooth, dampened and coated with a bonding agent.
5. Apply in coats. A first coat is scratched to give the second coat something to grip, then a finish coat is applied and floated or brushed to the texture you want. Two thin coats hold far better than one thick one.
6. Cure. New parging is misted and shaded as needed so it doesn’t dry too fast, and protected from frost.
7. Backfill and grade. Soil goes back with a slope away from the house.

Materials

Most parging here is a Portland cement and sand mix, often with lime and an acrylic or polymer additive for better bond and flexibility. Pre-bagged polymer-modified parging mixes are also common and consistent. On old fieldstone or brick foundations, a lime-based parge is usually the better choice (see stone restoration), because a hard cement parge over old masonry tends to trap moisture and come off. Finishes range from smooth float to sponge or broom texture. Parging can be left natural grey or coated with a breathable masonry coating.

Why parging fails so often here

Most houses built in Dieppe, Riverview and Moncton over the last few decades sit on poured concrete foundations with a strip of parging showing above the soil. A lot of the soil around Greater Moncton is clay-heavy, so it holds water against the foundation. Add snowbanks piled against the wall all winter and the spring melt, and the bottom edge of the parging stays wet for months at a time.

On many newer homes the parging was applied quickly, in one thick coat, during construction. Those are the walls where we see whole sheets coming away after a few winters. The fix lasts much longer when it comes with a downspout extension or a little regrading so water runs away from the house.

What affects the cost

• Linear feet of wall and the exposed height
• How much old parging has to come off
• Foundation repairs needed underneath: cracks, spalls, exposed steel
• Access: decks, steps, plantings, and tight side yards
• Digging and regrading along the wall
• Finish and coating choices

Parging questions