What do white salt marks on Algarve walls mean?

Start with the pattern, not the product

Photograph the mark dry and after rain. Note whether it sits below a coping, beside an irrigation line, near ground level or around a crack. New masonry can show temporary bloom; a local mark that returns later may indicate ongoing water entry.

• Record the date and recent weather
• Check the same area inside and outside
• Look above the stain for joints, pipes and edges

Test gently and protect the substrate

Dry brushing may remove a loose deposit, but natural stone, render and painted walls do not tolerate the same treatment. Acidic products can damage calcareous stone, and a strong wash can spread moisture or scar a finish. Identify the surface and test a small hidden area first.

Fix the route before repainting

If the deposit returns, inspect drainage, coping, seals, cracks, irrigation and contact with damp soil. Let the assembly dry and confirm that the cause is controlled before sealing or painting; otherwise the new finish can blister or peel.