What is rising damp?
Rising damp occurs when moisture from the ground rises through porous substrate materials (plaster, brick, stone, etc.) via capillary action. This moisture from the ground often contains damaging salts, which affect decoration and plaster internally. The moisture can also produce damp tide marks across the walls. Once effected walls dry down, the moisture will evaporate but the damage from the salts will remain, so rising damp can be quite destructive. Any timbers in contact with the wet walls may show signs of damp like floorboards and skirting boards and can lead to a decay outbreak in these timbers. Rising damp is refined to ground floor walls and can compromise the structural integrity of a property.
What causes rising damp?
Rising damp can be caused by a lack of Damp Proof Course (DPC) where there is no protection measure to prevent moisture from rising which is often seen in older buildings. The DPC may also be damaged, as seen in older buildings, allowing small pockets of moisture to rise through the damaged areas. Rising damp can also be caused by internal wall coverings like plaster bridging the DPC. This is where the walls are plastered down to the floor at the DPC level. This allows the ground moisture to rise up through the plaster, even while there is a DPC.