Scaling: thin flakes across an outdoor slab
Scaling is the top skin of an exterior slab giving up in thin, gritty flakes over a wide patch, most often on a driveway or a walk that already has a winter or two behind it. The flakes come off shallow, and the scaled area feathers out at its edges instead of ending in a clean line, so the patch tends to creep outward season by season rather than stopping where it started. Under the flaking, what is left still looks and feels like concrete.
The cause is water sitting in that top layer, freezing, expanding, and working the surface loose over repeated winters, with de-icing salt putting the slab through more of those cycles than the weather alone would have. A mix that went in without enough air entrainment leaves that water nowhere to expand into, and that is decided at the plant rather than something added later.
Delamination: sheets lifting off a crust
Delamination looks nothing like scaling once you know what you are looking at. The pieces are bigger, sometimes whole sheets a few inches across, and they lift away clean, leaving a shallow depression with a defined edge and a bottom that reads as smooth rather than torn. It shows up on floors that are indoors or still new, and a garage slab is the usual place to find it.
It traces back to the day of the pour. Bleed water and air keep working their way up out of fresh concrete for a while after it is placed, and closing the surface with a trowel before that has finished seals a thin layer of it under a dense crust. That crust has nothing bonding it to the slab underneath, so traffic pops it loose weeks or months later. Tapping across a floor like that will often sound hollow in the spots that have already let go but have not lifted yet.
Sorting out which one you have
Where the slab is and how old it is answers most of this before anybody looks closely. An outdoor slab with more than one winter behind it, salted every year, reads as scaling. A covered or indoor floor in its first year or two, flaking in patches rather than everywhere at once, reads as delamination. When those two signals disagree, go by the pieces themselves. A thin gritty flake and a lifting sheet are hard to confuse once you have both in front of you.
- Fine, gritty flakes over a broad outdoor area, after winters of freezing and salt: scaling
- Larger sheets lifting off a newer or indoor floor, leaving smooth bottomed depressions: delamination
- A hollow sound under a tap on a floor that has not started lifting yet: delamination getting ready to
What the difference changes about your next step
The split matters because the two are at different points in their life. Scaling is still going. Every winter that slab gets salt on it, it takes another bite, so the first useful thing you can do is stop salting it and switch to sand for traction. Delamination is already finished. The harm was done in the hours after the concrete was placed, and while more crust may still pop where it was never bonded, nothing you do or stop doing this winter changes how much of it is out there waiting.
It also shapes the repair. Delamination usually stays inside that thin crust, so it takes a resurfacer more often than scaling does. Scaling that has worked down far enough to show the stone in the mix is past what a resurfacer can honestly cover, and our tear out and replacement page walks through what that leaves you.