SiLOSSiLOS

Fixing flaking concrete steps without a rebuild

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1The short version

The corner comes off in your hand like stale bread, and the step underneath is usually fine, it's the surface having a chemistry problem. Most surface flaking on concrete steps is spalling: dissolved salt carried through the concrete crystallizes near the surface as the water evaporates, and the expanding crystals shear small fragments off, exactly the mechanism de-icing salt triggers every winter. Freeze-thaw cycling does the same kind of damage from trapped water expanding as ice, which is why entrained air is mixed into concrete meant to survive winters, to give that expansion somewhere to go.

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2Patch, resurface or rebuild

A patch fills a small chipped corner or shallow spall with a bonding agent and a cement-based repair mortar; it is a same-day fix for cosmetic damage that hasn't gone structural. A resurfacing overlay covers the whole worn tread and riser in a thin new layer when the surface is generally worn but the step underneath is still sound. A full rebuild is for a step that has cracked all the way through, settled unevenly, or lost enough material that a thin patch has nothing solid to bond to.

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3What goes wrong

A crack that runs all the way through, changes width with the season, or comes with one side of the step visibly lower than the other is settlement, not surface wear, and no patch fixes settlement. Chemical degradation can also come from corroding rebar inside the step: as the steel corrodes it expands and cracks the concrete around it from the inside, which shows up as a crack that keeps returning after every patch.

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4The first hour

Chip away anything already loose with a hammer and chisel until you hit solid concrete, not just the flaking layer; patching over loose material is the single most common reason a repair fails within a year. A wire brush and a rinse come next, and the actual patching material only goes on once the surface is clean, damp and free of dust.

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