Rising Damp

Whenever rising damp is seen or suspected in a building inspection, it is vital to have the condition correctly treated, as failure to do so can cause a great deal of damage to a building. Covering up the problem by painting or applying a render in the hope that the problem will go away will not work. The only solution is to prevent the damp from rising up the wall in the first place.

What is rising damp?

The movement of moisture up through the brickwork or masonry by capillary action is known as rising damp. It is commonly identified by what is termed a ‘tide mark a darkened area of the base brickwork usually about a meter in height similar to a water tide mark as the term suggests.

Other identifying features are, erosion of mortar, fretting of the brick face and flaking plaster around the base of internal rendered walls. Due the long periods of drought in Melbourne it would be unusual for a building inspection to find a building with rising damp. However, past rising damp may have occurred and left what is known as ‘salt damp’.

Masonry building materials such as clay bricks and poured concrete are very porous and susceptible to moisture. The dampness is caused by the vertical movement of moisture from the founding soils up through the masonry structure by what is known as ‘capillary action’. The moisture contains soluble salts that permeate the masonry materials. The salts cause a chemical reaction causing the bricks and/or mortar to deteriorate, and in some cases the mortar completely disappears causing areas of the brickwork to collapse.

What causes rising damp or salt samp?

The causes of rising damp can vary, however the most common causes are likely to be, poor sub-surface drainage systems such as leaking or dilapidated storm water pipes, leaking sewer pipes and natural seepage issues or the existence of sub-surface water tables. All brickwork should have what is called a ‘Damp Proof Course’ fitted at the base of the wall just below floor level. In older homes however, the material used was a powdered additive mixed into the mortar mix, usually colored black. These typically deteriorate and fail, allowing moisture to creep up the wall past floor level. Current practice is the use of a plastic membrane fitted at time of construction.

What should you do about rising damp or salt damp?

A building inspection may be able to identify the existence or past existence of rising damp but you should have a specialist assess the building to determine the exact cause and appropriate rectification procedures. In some circumstances you may need to have a geo-technical engineer carry out soil inspections to determine the soil make up and drainage patterns.

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