This is one of most common and discussed dampness found in building. In recent times, condensation is the most common form of dampness, however positive identification and the right corrective action for both is vital. Rising damp is simply referred to as the flow of water upwards and vertically through permeable wall structure, the water being gotten from the ground. The moisture rises via the capillaries or pores in the masonry, meaning that the masonry functions just like a wick. With rising damp, water rises through the mortar beds and through the bricks. The mortar forms the only continuous pathway for the moisture to rise up the wall. Even if a house is built from impervious bricks then moisture can still rise through the mortar beds, however if an impervious brick is incorporated then water will not rise even if the bricks happens to be quite porous. In other words, mortar beds are an integral element in the chemical treatment for rising damp.
The moisture coming from the ground features small quantity of soluble salt which includes nitrates, chlorides as well as sulphates. These are transmitted with the water up the wall and are deposited and left behind when the moisture evaporation when drying. After some time, the salts will slowly accumulate and form a salt band close to the peak height of the rising damp. Chlorides and sulphates absorb water from the environment. Overall, the higher the quantity of salts, the greater the absorption of moisture from the environment and even more so when under humid conditions. In other words, even if rising dampness has been controlled by the installation of damp proof course, these salts can still make the wall and any affected decorations to remain damp.