CSLB C-33 Painting & DecoratingSurface PreparationMedium
A painting contractor is preparing an exterior brick wall that has significant amounts of efflorescence. After removing the efflorescence, which of the following is the most important step to prevent its recurrence before painting?
- AApplying a breathable acrylic sealer.
- BApplying an oil-based alkyd primer.
- CHosing down the wall daily for a week.
- DIdentifying and addressing the source of moisture intrusion.
Show answer & explanationAnswer & explanation
Correct answer: D. Identifying and addressing the source of moisture intrusion.
Efflorescence is caused by soluble salts migrating to the surface with moisture. While cleaning removes the visible salts, preventing recurrence requires identifying and stopping the source of moisture intrusion (e.g., leaky gutters, cracks in masonry, rising damp). Without addressing the moisture source, efflorescence will almost certainly return, compromising the paint job.
Why the other options are wrong
- A. While sealers can help, they are often not sufficient if the moisture source is not addressed, and some can trap moisture if not breathable.
- B. An oil-based alkyd primer does not address the underlying cause of efflorescence and will not prevent its recurrence.
- C. Hosing down the wall daily would introduce more moisture, exacerbating the problem rather than solving it.
Efflorescence Recurrence Prevention
To prevent efflorescence recurrence after removal, it is crucial to identify and eliminate the source of moisture intrusion that brings soluble salts to the surface.
- Efflorescence is moisture-driven.
- Removal is temporary without source control.
- Common sources: leaks, rising damp, faulty drainage.
Memory trick: Efflorescence's return means moisture's deep concern.