Wendy sent in photos of a damp patch where recent building work, new plaster and decoration have started to blister and fail.
Roger looks at the clues, including the new studwork, the plasterboard join, the radiator pipework buried in the wall, the outside render detail and possible signs of moisture around the bay.
The key point is that this cannot be diagnosed properly from one photo. It might be external moisture, an air brick or render issue, or it could even be a small leak from the newly installed pipework. Before blaming rising damp, Roger explains the checks he would carry out, including pressure testing the heating system and monitoring water levels in an open-vented system.
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🔑 Key Insights
• Don’t assume every damp patch near the floor is rising damp.
• Recent building work can create several possible causes, including plaster movement, cracked joins, buried pipework and trapped moisture.
• The faint vertical line in the finished wall appears to be where the new stud wall meets the older masonry/plaster.
• Scrim tape can help across joints, but it will not always stop cracking where different materials meet.
• The damp appears to be affecting the masonry side more than the plasterboard infill, which is an important clue.
• The outside wall, render, bay detail and air bricks should all be checked before making a diagnosis.
• Newly installed radiator pipework should be tested, especially where elbows or joints have been buried or plastered over.
• A tiny leak on a heating pipe can create a surprisingly large damp pattern over time.
• For a pressurised heating system, a pressure test can help show whether water is being lost.
• For an open-vented system, checking the header tank level over several cold-system readings can reveal slow water loss.
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