White powder on brick is not one problem — it can be efflorescence, paint residue, or biological growth, and each needs a different treatment. Cleaning before you identify it can make it worse.
Efflorescence
Efflorescence is a mineral deposit left when water moves through the brick and evaporates, carrying salts to the surface. It is a sign of moisture moving through the wall, not just a surface stain. Removing it without addressing the moisture means it returns.
Paint or residue
A white film can be leftover paint, caulk, or construction residue. Pressure will not dissolve it; the right remover for the material will.
Biological growth
A powdery or fuzzy white growth in damp, shaded areas can be mold or lichen. Soft washing treats live growth at the root.
Five-minute self-check
- Does the powder brush off easily (efflorescence) or is it bonded (paint)?
- Is the area damp, shaded, or near a water source?
- Look for signs of moisture movement through the wall.
- Test a small spot with water — does it react or stay put?
- Note whether it returns after rain (a sign of efflorescence).
Related reading
See our soft washing page.