Efflorescence or Rising Damp? Assessor and Treatment Guide

Most likely cause

Rising damp

How each signal scored, and how the three look alike conditions ranked.

What this assessment assumes

Efflorescence is a salt deposit left behind when water moves through masonry and evaporates at the face. The salt is the symptom, the water path is the fault.
New masonry carries its own soluble salts. Blooming that settles within about 12 months and does not return after one clean is cosmetic.
Salt banding between roughly 300mm and 900mm above ground, with a hard upper tide mark, is the classic rising damp signature in Melbourne brickwork.
A retaining wall, slab, paving or tiled area is not assessed for rising damp. Those hold a permanent water source on the hidden face, so recurring bloom there is a moisture path, not rising damp.
Dry brushing comes first because wetting a salt bloom drives it back into the masonry and it returns.
Acidic efflorescence removers are dilute hydrochloric or phosphoric acid. Pre wet, apply, neutralise and rinse. They will etch glazed tiles, burn plants and mark aluminium.
Never coat a wall that has a live moisture source with a non breathable membrane. Trapped moisture blisters the film and can push render off the substrate.
Rising damp is a building repair, not a painting job. A registered builder handles damp proof course injection or replacement, and ground level correction.
This is a guide from what you can see. It does not replace a moisture meter reading or a builder's inspection.

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