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Cross-market term

Spalling and scaling

Material breaking away from the face of masonry or concrete. What separates the cases is DEPTH and cause: a thin surface loss, a flake off a brick face, or a piece dislodged by something expanding behind it.
  • 4Markets
  • NoSame thing everywhere
  • 3Calculators

What it is called, by market

One concept, four markets. Where a name means something else locally, the card says so rather than leaving you to find out on site.

  • United Kingdom

    Close, not identical

    spalling

    also frost damage, blown brick, delamination, popping

    A BLOWN brick is one whose fired face has come away leaving the softer body exposed, which then erodes quickly — a specific and common case rather than a general term.

  • Australia

    Same word, different thing

    spalling

    also concrete cancer, salt attack, fretting

    CONCRETE CANCER is the common Australian term for spalling driven by reinforcement corrosion, and FRETTING names the crumbling loss of mortar and soft masonry, which is erosion rather than spalling.

  • United Statesyours

    Same word, different thing

    spalling

    also scaling, delamination, pop-out, flaking

    SCALING is a distinct defined defect: loss of a thin surface layer of concrete, graded by depth and typically from de-icing salts and freeze-thaw. A POP-OUT is a small conical loss over a single unsound aggregate particle.

  • Canada

    Same word, different thing

    spalling

    also scaling, pop-out, delamination

    As the United States, with scaling a routine concern given salt use and the freeze-thaw cycle count.

The governing standard, by market

  • United Kingdom

    BS EN 771-1 / BS EN 1504-9

    Clay masonry units including freeze-thaw durability categories, and the principles for protection and repair of concrete structures.

  • United States

    ASTM C672 / ACI 201.2R

    Scaling resistance of concrete surfaces exposed to de-icing chemicals, and guide to durable concrete.

Calculators for this

Each works in either measurement system, and the terminology on the page follows whichever market you have selected.

Brick Calculator →Tuckpointing Mortar Repair Volume Calculator →Concrete Calculator →

Frequently asked questions

What is the difference between spalling and scaling?
Depth and mechanism, and the American standards separate them because the repairs differ. SCALING is the loss of a thin surface layer — the mortar skin comes away and the aggregate is exposed, usually graded by how deep it has gone. Its typical cause is freeze-thaw acting on a surface saturated with de-icing salt, and it is a surface durability problem. SPALLING is a piece of material coming OFF, often several centimetres deep, and its typical cause is something behind it expanding: corroding reinforcement, a corroding steel lintel, ice in a saturated brick, or a hard repair restraining a soft substrate. So scaling is about the surface's resistance and spalling is about what is behind it — which is why probing the depth is the first thing to do and why a surface treatment fixes one and hides the other.
Why does reinforcement corrosion spall concrete rather than just weakening it?
Because rust takes up several times the volume of the steel it came from, and that expansion happens inside the concrete. Reinforcement is protected by the alkalinity of the surrounding concrete, which passivates the steel — and that protection is lost either when carbonation reaches the bar, or when chlorides do. Once corrosion starts, the expanding rust exerts pressure on the cover concrete from within, and since concrete is weak in tension the cover cracks and then breaks away in a piece, exposing the bar. The exposed bar then corrodes faster. That is why COVER is specified so carefully, why spalling on a concrete structure is treated as urgent rather than cosmetic, and why patching the face without treating the steel simply relocates the same failure to the edge of the patch.
Why does a brick face blow after decades of being fine?
Because something changed the water, not the brick. A fired brick has a denser skin and a more porous body, and the skin is what resists frost. It blows when the brick becomes saturated and then freezes — so the trigger is almost always a change in how wet that brick gets: a failed gutter above it, ground level raised against the wall, a cement render or a sealant trapping moisture in, a repointing in a mortar harder than the brick so the wall now dries through the face instead of the joints, or a bed against the wall being watered. That is why blown bricks cluster rather than appearing at random, and why replacing them without finding the water source produces the same failure in the new ones within a few winters.