During a masonry repair project on an older building, a contractor discovers significant efflorescence on a brick wall. Which of the following is the most effective long-term strategy to mitigate efflorescence, assuming the source of moisture has been identified and addressed?
- AApplying a hydrophobic sealant directly over the efflorescence.
- BReplacing deteriorated mortar joints and ensuring proper flashing and drainage.
- CAggressively sandblasting the brick surface to remove salt deposits.
- DWashing the wall repeatedly with a high-pressure water sprayer.
Show answer & explanationAnswer & explanation
Correct answer: B. Replacing deteriorated mortar joints and ensuring proper flashing and drainage.
Efflorescence is caused by soluble salts migrating to the surface with water and precipitating. Replacing deteriorated mortar and ensuring proper flashing and drainage addresses the pathways for moisture ingress and the source of soluble salts, which are often found in mortar or the masonry units themselves. Simply removing surface salts without addressing moisture will lead to recurrence.
Why the other options are wrong
- A. Applying a sealant directly over efflorescence will trap the salts and moisture, potentially worsening the problem or causing subsurface damage.
- C. Sandblasting is too aggressive for historic brick, can damage the surface, and doesn't address the underlying cause of efflorescence.
- D. High-pressure washing can drive water deeper into the masonry and doesn't address the source of moisture or salts, leading to recurrence.
Efflorescence Mitigation
Efflorescence is a crystalline deposit of salts that appears on masonry surfaces, typically white, caused by water dissolving soluble salts within the masonry and transporting them to the surface where the water evaporates.
- Requires three conditions: soluble salts, moisture, and a pathway for moisture.
- Long-term mitigation focuses on eliminating moisture ingress.
- Surface cleaning is temporary if the source is not addressed.
Memory trick: Find the Flow, Fix the Flaw, Forget the Frosting.