Salt contamination in masonry and plaster is a major contributor to damp problems in buildings. While rising damp is often blamed, it is not the only cause. One of the most common sources of salt contamination is chimney breasts, where decades of exposure to combustion gases lead to the accumulation of salts. This contamination can appear not just at ground level but also on upper floors, making it a widespread issue in older properties.

Other potential sources of salt contamination include:

• Chimney flue gases – Acids in combustion gases form chlorides, nitrates, and sulphates, which migrate into the masonry, causing damp staining and degradation.
• Plumbing leaks – Prolonged leakage from tap water or central heating pipes introduces salts into walls and floors.
• Soil and animal waste contamination – Salts from soil water or urine, especially in barn conversions or former stables, can lead to persistent damp problems.
• Direct rain penetration – External walls exposed to driving rain can absorb moisture and salts, leading to damp patches inside.

Since many of these salts are hygroscopic (moisture-attracting), damp patches may appear and disappear depending on humidity and weather conditions—often leading to false assumptions about leaks. Because of this, a professional survey is essential to correctly diagnose and treat salt-related damp issues