Understanding Efflorescence

THE SHORT EXPLANATION

Water dissolves naturally occurring salts in mortar ingredients. The salt-bearing water moves through the brickwork. When the water reaches the surface and evaporates, the salts remain behind.

1  SOLUBLE SALTS

Often associated with mortar ingredients—cement, lime and sand—but they may also be present in bricks, backing materials, soil or other materials in contact with the wall.

2  MOISTURE

Rain, wet mortar, rising damp, leaking pipes, sprinklers, poor drainage or unprotected wall tops can provide the water needed to dissolve the salts.

3  A PATH TO DRY

The solution travels through pores in the brick or mortar. Evaporation at the surface leaves the salt deposit visible.

Ordinary surface efflorescence is generally harmless and often diminishes as new masonry dries and the available salts are exhausted. Persistent, heavy or recurring deposits are different: they can be a useful warning that excess moisture is entering the wall and the source should be investigated.

Common contributors

• Wet mortar. Excess mixing water increases the volume of water available to dissolve and transport salts.
• Inconsistent or rich mortar. Poor batching or excessive cement and lime can increase the potential for deposits and colour inconsistency.
• Construction exposure. Uncovered wall tops, wet pallets and brickwork exposed before copings, flashings and sills are completed can absorb substantial water.
• Rising or bypass damp. Missing, bridged or incorrectly positioned damp-proof courses allow ground moisture to move into the masonry.
• Defective water management. Leaking gutters or pipes, failed flashings, blocked weepholes, sprinklers, poor falls and soil or paving held against the wall can keep masonry wet.
• Reclaimed masonry. Reclaimed bricks may carry residual calcium sulfate, lime or mortar from their previous use. A harmless white residue can therefore be present before or after laying.

• Store bricks off the ground and protect them from rain while allowing ventilation.
• Cover unfinished wall tops and complete copings, flashings and sills promptly.
• Batch mortar accurately and avoid making it wetter than necessary.
• Keep cavities, weepholes and drainage paths clear; direct roof water and surface runoff away from brickwork.
• Install the damp-proof course correctly and keep it visible—generally at least 150 mm above finished landscape surfaces. Do not bridge it later with soil, mulch, paving or concreting.
• Where appropriate and compatible with the mortar system, consider a purpose-made efflorescence-control additive. Follow the additive manufacturer’s dosage and pH requirements.

LET THE WALL DRY

Wait for a period of dry weather and allow the brickwork to dry thoroughly. On new work, do not rush to clean while moisture is still migrating through the masonry.

TEST AND IDENTIFY

Choose a small, inconspicuous area. Confirm the deposit is loose and powdery. If it is hard, glossy, coloured, greasy or unaffected by brushing, it may be a different stain.

DRY BRUSH FIRST

Use a clean, stiff, non-metallic brush. Work from the top down and collect or vacuum the dry residue where practical. Wear eye protection and a suitable dust mask.

MONITOR

Allow the wall to remain dry and observe it. A light new-build bloom may recur once or twice and then stop as the available salts are depleted.

ESCALATE CAREFULLY

If deposits persist, first find and correct the moisture source. Then obtain product-specific advice from the brick supplier or use a Think Brick-accredited masonry cleaner. A proprietary cleaner matched to the identified deposit and brick type is safer than improvised chemistry.

What not to do

• Do not start with hydrochloric acid. Acid is not the default treatment for efflorescence and may damage mortar, alter brick colour or intensify other stains.
• Do not use a turbo nozzle or concentrated pressure stream. It can erode brick faces and mortar joints and drive additional water into the wall.
• Do not seal a damp or actively efflorescing wall. A coating does not correct the moisture source and may trap moisture or move the deposit elsewhere.

BEST RESULT

Remove the dry deposit, but solve the water problem. If the moisture source remains, efflorescence is likely to return.

• Elephant Brick Co — Expert Brick Facade Construction
• Elephant Brick Co — Damp Proof Courses
• Elephant Brick Co — Reclaimed Brick Guide
• Think Brick Australia — Technical manuals and brick cleaning guidance
• Brick Industry Association — Technical Note 23A: Efflorescence, Causes and Prevention
• Brick Industry Association — Technical Note 20: Cleaning Brickwork