Term: efflorescence

Efflorescence is a crystalline, powdery deposit of salts that appears on the surface of masonry, concrete, brick, or other porous building materials. It typically manifests as a white or greyish residue and occurs when water within the material carries soluble salts to the surface. As the water evaporates, it leaves the salts behind.

Causes of Efflorescence:

• Moisture intrusion: Water enters the substrate through rain, groundwater, or construction moisture.
• Soluble salts: Present in the building materials (e.g., cement, sand, bricks).
• Evaporation: Water migrates to the surface and evaporates, depositing salts.

Common in:

• Brickwork
• Concrete walls and floors
• Rendered surfaces
• Tiled areas

Implications for Painters and Contractors:

• Efflorescence must be removed before painting or sealing, as it can cause poor adhesion and paint failure.
• Indicates moisture issues that may need to be addressed (e.g., waterproofing, drainage).
• May require treatment with acid-based cleaners or mechanical removal, followed by proper surface preparation.

Prevention:

• Use low-alkali materials
• Ensure proper drainage and waterproofing
• Apply breathable sealers or coatings
• Allow substrates to fully cure and dry before painting

Efflorescence is not usually harmful structurally but is a sign of moisture problems that can affect the longevity and appearance of coatings.