Many homeowners don't think about either word until a chunk of grey coating falls off the wall by the front steps, or a crack shows up in the basement after a hard winter. Here is how to tell which family your problem belongs to, and what to do next.
Parging is a protective skin, not a structural repair
Parging is the smooth grey layer you see on the part of the foundation above the soil. Under it is usually concrete block or poured concrete. Tarion, Ontario's new home warranty body, describes parging as a cement-based layer, and notes the Building Code only requires it on concrete block foundation walls below grade. Above grade, it isn't a Code requirement: it's a finish that covers and protects the wall.
That's the key point. Parging covers the wall. It doesn't hold anything up. A new coat over a wall that is still moving only covers the problem.
Flaking parging is usually a surface problem
Some parging trouble is close to normal:
- Hairline cracks. Tarion says hairline cracks are normal in parged surfaces.
- Patches that flake or pop off. It's ugly, and every bare patch leaves the wall less protected, but on its own it's a problem with the skin.
One thing to take more seriously: Tarion says parging that is separating from the concrete block behind it is not acceptable. If the coat sounds hollow when you tap it, or whole sheets come away, the bond has failed. Ask yourself why water is getting in there.
Sideways, stepped or growing cracks point below the surface
The cracks that worry the experts are the ones that run through the wall itself, not just the coating. Home repair guide Bob Vila puts it plainly:
- Horizontal cracks and stair-step cracks (the zigzag that follows the mortar joints in a block wall) are serious and should be looked at right away. Horizontal cracks usually come from pressure pushing on the wall from outside.
- Vertical and diagonal cracks typically don't point to a structural problem.
A few other signs are worth noting before anyone visits:
- The crack is getting longer or wider over the months.
- The wall looks bowed or pushed in.
- Water comes through the crack.
Take dated photos of the crack with a tape measure or a coin beside it, so you can see whether it changes.
Underpinning is structural work for an engineer to design
Underpinning means building new support under the existing foundation: deeper footings, or a stronger base for a wall that has settled. Because it removes and replaces the support a house is standing on, the Government of Ontario's guidance on underpinning says bracing is critical and a professional engineer should design the bracing and the method.
What that means for you:
- Don't let anyone sell you underpinning from a single glance. A structural problem deserves an engineer's assessment of what's moving and why.
- Don't let anyone sell you parging as the fix for a moving wall. A fresh coat over a structural crack hides it for a season.
If your foundation is wet but not moving, ask about basement waterproofing as well.
Good photos make any assessment easier
You don't need to diagnose your own foundation. You need someone qualified to look at it. Good photos help whoever does, an engineer or a contractor, before anyone visits:
- One wide shot of the whole wall, to show where the crack sits.
- A close-up of each crack, with a tape measure or coin for scale.
- The outside and the inside of the same spot, if you can reach both.
- Any water marks, white powdery deposits or flaking on the basement side.
Note how long you've seen the problem and whether it has changed. Dated photos show that better than memory.
