Key Takeaways
- Most damp in London homes is condensation, not rising damp.
- The three types are condensation, penetrating and rising damp, each with different fixes.
- Correct diagnosis before treatment avoids spending on the wrong solution.
- Common causes include poor ventilation, blocked airbricks, failed pointing and high ground levels.
- Period solid-walled homes need breathable repairs, not sealing in moisture.
Damp is one of the most common and most misdiagnosed problems in London homes. Spend on the wrong fix and the problem returns. Here is how to tell the three types apart and treat each correctly.
The three types of damp
- Condensation: by far the most common. Moisture in the air meets cold surfaces where ventilation is poor, causing mould in corners, around windows and behind furniture. Worse in winter.
- Penetrating damp: water enters through the structure via failed pointing, cracked render, a leaking roof or blocked gutters. Often patchy and linked to a defect.
- Rising damp: groundwater rising through walls where the damp-proof course has failed or is absent, showing as a tide mark up to about a metre high. Less common than assumed.
Diagnosis comes first
The single biggest mistake is treating before diagnosing. Most damp blamed on rising damp is actually condensation, which an injected damp-proof course will not fix. A proper survey that considers ventilation, external defects and ground levels, not just a damp meter reading, tells you the real cause and the right fix.
The right fixes
- Condensation: improve ventilation (extractors, trickle vents), heat adequately, address cold spots with insulation, and avoid drying clothes indoors unventilated.
- Penetrating damp: repair the source, repointing, render, roof or gutters, then let the wall dry.
- Rising damp: install or repair a damp-proof course, lower high external ground levels and clear blocked airbricks.
Period homes need breathability
In solid-walled period homes, the fix is usually to restore breathability and ventilation, not to seal moisture in with modern renders and paints, which often worsens the problem. We diagnose damp correctly and treat the cause as part of a renovation. For advice, contact us or call 07472 424 226. See also renovating a Victorian terrace.