WHAT IS RISING DAMP?
Rising damp is the term used to describe the upward movement of moisture through porous masonry walls.
The moisture rises through capillary action, saturating the wall to a height of around 1m before evaporating. It can damage brickwork and mortar, damage internal decorations and leave a strong, musty smell. It can also cause damage to timber by creating the perfect environment for rot and wood worm.
In addition, the moisture brings with it soluble salts from the ground. As the moisture evaporates it deposits these salts in the masonry, leaving a visible tide line on internal decorations. These crystalized salts tend to block the pores, reducing evaporation and increasing the levels of dampness. These salts are hygroscopic, meaning that they can absorb moisture from the air in conditions of high relative humidity, leaving surfaces wet during periods of rainy weather.
CAUSES OF RISING DAMP
Most buildings have a physical damp-proof course (dpc) of slate, bitumen felts, or plastic membrane.
These materials are very robust and have a long life-span, but can in some cases fail, allowing moisture to rise through the masonry.
Most causes of rising damp are, however, caused by the dpc being bridged by one of the following;
- External rendering or internal plastering over the dpc
- Raised external soil levels, of paths or patios
- Mortar droppings within a cavity wall, allowing moisture to cross the void between the brickwork
In all cases, it is vital to correctly diagnose the source of any dampness, avoiding unnecessary and costly work.
GHA Environmental provide specialist rising damp solutions, backed by our 30-year guarantee.
The treatment of rising damp is a 3-part process;