Concrete is porous, which means different contaminants penetrate to different depths and require different treatments. Using the wrong approach — or just water pressure — often produces disappointing results.
Thrives in shaded, damp areas. Black or dark green in appearance. Requires biocide treatment — not just pressure washing — to prevent rapid regrowth.
From vehicles, BBQ grills, and machinery. Hot-water extraction with degreasers removes most staining. Deep oxidized stains may leave slight shadowing.
Orange staining from metal furniture, planters, irrigation systems, or fertilizer. Requires oxalic acid treatment. Not removable with standard pressure alone.
High-pressure steam or focused pressure at the correct angle shears gum from concrete. Chemical softeners may be used for heavy accumulations.
Tannin staining from organic matter is common in Bay Area courtyards and patios. Alkaline cleaners and surface washing restore most concrete fully.
White, chalky mineral deposits that bleed from within concrete. Requires acid washing to dissolve the mineral salts. Common on new concrete and retaining walls.
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