Penetrating Damp vs Rising Damp: What's the Difference?

Damp is damp, right? Not exactly. Getting the diagnosis wrong leads to wasted money on the wrong treatment. Here's how to tell these two common types apart.

Rising Damp - Travels upward from the ground through the wall - Affects the base of ground-floor walls - Usually stays below 1 metre high - Shows tide marks, salt deposits, and plaster damage - Caused by a failed or absent damp-proof course (DPC) - Treatment: chemical DPC injection + replastering

Penetrating Damp - Enters horizontally through the building fabric - Can appear on any floor, including upper floors - Often associated with specific weather conditions (heavy rain) - Concentrated around windows, roofs, gutters, and external walls - Caused by defective pointing, cracked render, failed seals, or blocked gutters - Treatment: repair the external defect causing entry

How to Tell Them Apart Rising damp leaves staining that stops at a fairly consistent height. Penetrating damp tends to form patches that get worse during or after rain and may appear in multiple locations. If damp appears above the ground floor, it's almost certainly not rising damp.

When in doubt, call a professional. A thorough damp survey by Shadbolt Plastering will give you an accurate diagnosis and a clear treatment plan.