Why Is My Parging Cracking or Falling Off? How to Read It

Your parging is the grey band of cement around the bottom of the house. When it starts to crack, flake or drop off in chunks, it is easy to think the foundation is failing. Most of the time it is not. Parging is a thin coat that takes the weather so the wall behind it does not have to. But how it fails tells you a lot, and the signs are worth reading before anyone puts a new coat on. This page helps you match what you see on your wall to what is usually behind it. For the full background on what parging is and how a repair is done, read our guide to cracked and failing foundation parging.

Start with the sound test

Walk the wall and tap it with the handle of a screwdriver. A hollow, drummy sound means the coat has let go of the wall even where the surface looks whole. Mark those patches. They matter more than the cracks you can see, because hollow parging is on its way off and anything loose has to come off before new mortar goes on.

What the signs usually mean

Sheets or large pieces coming off. This is the classic Ontario failure. Water gets between the coat and the wall, freezes, and pries the coat off. It is why so much parging fails in its first or second winter. Water behind the coat is the cause, and the coat that comes off was often not bonded well to begin with.

Crumbling, sandy or powdery surface. The mortar itself is breaking down. Road salt spray off the driveway lands on the lowest band of wall, which is exactly where the coat is, and it holds moisture against the surface. The band closest to the driveway is often the first to go. A coat troweled too thin, or put on too late in the season and frozen before it cured, crumbles the same way.

A crack that runs in a straight line, or steps along the joints. A parge coat cracking over a structural crack means the wall behind it is moving. On block and stone, soft or crumbling joints do the same thing: the coat cracks along the failing joints. That is a foundation repair question, or a repointing job before the coat, not a parging problem. New parging over an active crack just cracks again.

White chalky bloom, damp patches or bulging. These point to moisture in or behind the wall. Parging sheds weather above grade and does nothing for water coming through the wall below grade. If you have water in the basement too, start with basement waterproofing and parge after.

Failure in one concentrated low spot. A coat letting go in one place often means water collects there, usually from a downspout discharging beside the foundation or grading that sends runoff to one corner. Fix the coat without fixing the water and the new coat fails in the same place.

Painted parging that is peeling. Paint on a crumbling coat seals moisture in instead of out. Painted-over parging costs more to fix later, because the paint and the coat under it both have to come off before new mortar will bond.

Why it happened in the first place

The weather is the same for every house on the street, so whether a coat lasts comes down to water and prep. Common causes:

• Freeze-thaw cycling pushing water in and out behind the coat all winter.
• No bonding agent, or a dusty, damp or painted wall, so the coat never gripped.
• A coat that is too thin, or a single thick pass that slumps and cracks.
• A late-season job that froze before it cured.
• Road salt and moisture sitting against the lowest band of wall.
• A wall that is moving or wet behind the coat.

If your parging failed in the first winter or two after it was done, that points to workmanship, not age. Done with proper prep in the right weather, parging should last decades, not one winter.

What a proper fix looks like

The fix follows the cause. If water is collecting at a corner, that gets dealt with. If the wall is moving or the joints are rotten, that is repaired first. Then the parging itself:

• Every hollow or loose patch is stripped back to solid material, and old paint comes off.
• The wall is cleaned and a bonding agent goes on, because fresh mortar will not hold a dry, dirty surface.
• Fibreglass mesh goes over patches, filled voids and material changes.
• The coat goes on at about 1/4 to 3/8 of an inch, in two passes where the wall is rough, and is kept damp while it cures.

That prep is also what decides the cost of the job, which is why a number cannot be read from a photo. The factors are laid out in our parging cost factors guide.

When to get it looked at

Get it looked at if the parging sounds hollow, comes off in sheets, cracks in a straight or stepped line, or sits over damp or white bloom. A crack that keeps reopening after a patch is the wall telling you something. Do not paint over any of it.

We take parging jobs of every size, including a single wall, with the same written quote and the same lifetime warranty on labour as a full foundation. Tell us what the wall is doing and we will come look. You get the prep spelled out in writing, and if the problem is water or the wall behind the coat, we will tell you that before you spend money on a coat that would only hide it. See how we handle parging repair, or request a free written quote.