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Forensic and structural engineers servingServing VIC, TAS, QLD, SA, NSW and the ACT

What is Efflorescence and How to Prevent it (simplified)

This post looks at efflorescence, a problem found even in new Melbourne buildings. It explains how water-soluble salts create white stains on masonry and concrete surfaces. The content covers the three main factors contributing to efflorescence and outlines practical prevention strategies. Property owners will find valuable insights on maintaining their building’s appearance and structural integrity.

Salt stains on walls: More than just an eyesore

We’ve seen efflorescence on many old buildings over the years. But when we found it on a new Melbourne apartment just one year after it was built in 2023, we realised there’s a gap in understanding this issue in the Australian construction industry. That’s why we’ve written this blog post. We want to explain what efflorescence is, why it happens, and how to prevent it. Our goal is to help property owners and builders better understand and address this common problem.

Read about a real case of a leaking basement of a prestigious apartment building here.

Wet efflorescence on dark brickwork indicating moisture problems.

The Science Behind Efflorescence

Efflorescence is the result of water-soluble salts surfacing on masonry or concrete. Its formation is contingent upon three factors:

  1. Presence of water-soluble salts within the masonry or concrete.
  2. Sufficient moisture to transport these salts.
  3. A pathway for this moisture to move and evaporate, leaving salt residues behind.

Efflorescence will not occur if one of these conditions is not present. Therefore, to prevent the formation of Efflorescence, it is simply required to control the three factors mentioned above.

Close-up of efflorescence streaks on a concrete wall.

Strategies to Prevent Efflorescence

The battle against Efflorescence starts with the materials used. Opting for low-alkali Portland cement, ensuring sand is clean and washed, and using potable, salt-free water can significantly reduce the potential for Efflorescence.

During construction, limiting water use to only what’s necessary for mortar and grout preparation is crucial. Excess moisture can seep into the masonry, catalysing Efflorescence. Implementing effective drainage systems can prevent water accumulation around the structure, further mitigating risk.

Additionally, achieving a denser grout through mechanical vibration can minimize voids in the material, making it harder for moisture and salts to navigate through the masonry.

Efflorescence formation on a concrete ceiling next to a rusty pipe.

Taking Action

Today’s construction practices and materials offer no excuse for Efflorescence in new structures. If you’re facing Efflorescence on your property and seek removal advice or further guidance, professional engineering services can provide the expertise needed to address this issue effectively.

Efflorescence isn’t just a cosmetic concern; it’s a sign of water movement within structures. Addressing it not only preserves the aesthetic appeal of a building but can also pre-empt more serious damage caused by unchecked moisture.

For detailed solutions and personalised advice on tackling Efflorescence in your building, reaching out to structural engineering experts can ensure your property remains beautiful and structurally sound.

Understanding Efflorescence: Key Points

  • Efflorescence occurs when water-soluble salts surface on masonry or concrete.
  • Three factors contribute: presence of salts, moisture, and a path for evaporation.
  • It can appear in both old and new buildings, signalling potential moisture issues.
  • Prevention starts with proper material selection and construction practices.
  • Professional assessment can help address existing efflorescence and prevent future occurrences.

About the author

Sara Khani - Senior Forensic Structural Engineer at MFS Engineering
Sara Khani

Forensic Structural Engineer

Sara Khani is a Senior Forensic Structural Engineer at MFS Engineering Australia, with more than 20 years of engineering experience, approximately 15 of them in Australia. She investigates structural failures and building defects where the cause or the remedy is unresolved or disputed, and acts in rectification, multi-party building dispute and expert-witness matters.

Credentials. Sara Khani holds RPEQ registration in Queensland (RPEQ 26271), professional engineer registration in Victoria (PE0005122) and professional engineer registration in New South Wales (PRE0002683), and is listed on the Engineers Australia National Engineering Register (EA ID 4312538). She is a member of the Forensic Engineering Society of Australia, the Association of Consulting Structural Engineers Victoria (ACSEV), and the Building Dispute Practitioners’ Society.

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