Why is the concrete flaking off my foundation walls?

Flaking or crumbling concrete is usually caused by spalling, which occurs when internal steel rebar rusts. As moisture enters microscopic cracks, the rebar corrodes and expands, creating internal pressure that blasts the surrounding concrete outward, severely compromising the wall’s structural load-bearing integrity.

Concrete is heavily reinforced with steel rebar to provide tensile strength. Under ideal conditions, the high alkalinity of the concrete protects the steel from rusting. However, when water breaches the concrete through hydrostatic pressure or capillary action, it introduces oxygen and chlorides into the matrix. This process, known as concrete carbonation, lowers the alkalinity and allows the embedded steel to oxidize (rust).

When steel rusts, it can expand up to four times its original diameter. This expansion generates immense internal tensile stress within the wall. Because the concrete cannot stretch to accommodate the swelling steel, it fractures and violently ejects the surface layer of concrete—a process known as spalling. You will typically see large chunks of concrete falling away, exposing the heavily rusted rebar underneath.

Spalling is not a cosmetic blemish; it is a rapid degradation of the foundation’s structural skeleton. If left unchecked, the rebar will disintegrate completely, leaving the foundation with zero tensile strength and highly susceptible to shear failure. The professional restoration protocol requires excavating the damaged concrete to expose the healthy steel, treating the rebar with an anti-corrosion inhibitor, applying structural-grade patching mortars, and permanently addressing the external water source that caused the oxidation in the first place.

Stop internal structural decay before it leads to total wall failure. Contact us for Foundation Crack Repair in Everett, WA