Rising damp occurs when moisture creeps slowly from the soil under a structure and up into the base of the walls.

This commonly occurs in buildings made of brick or stone, as the moisture follows the capillary nature of the masonry. This moisture carries dissolved salts, nitrates, phosphates and other naturally occurring elements. Damage occurs as the salts expand and contract within the wall through on-going seasonal wetting and drying cycles.

Signs that your home may have a rising damp problem include stained walls, blistering or flaky paint on walls, curling or stained wallpaper, salt residue, disintegrating mortar, and rotting timber skirting boards or door frames but no mould.

Traditional methods

The traditional way of combating rising damp is to put in what’s known as a "physical" damp course. This involves taking mortar out of the walls and inserting a membrane continuously along a horizontal mortar joint. However, beware – this method can cause structural damage to the house.

Injection method

Another method employed to fix rising damp in Australian houses is called an "injection" damp course. This involves drilling into the middle of the bricks at the base of the wall and inserting a silicone-based product that spreads throughout the walls, coating the sides of the pores and capillaries. This creates a "repellent" layer to combat capillary rise without blocking the pores, which would inhibit natural vapour transfer.

Electro-osmosis

Electro-osmosis is a modern execution of an ancient principle to cure rising damp. John Geraghty, an expert in this treatment, explains.

"Essentially, electro-osmosis creates a means of repelling moisture. We install a series of platinised titanium anodes into the affected masonry at one meter intervals and introduce a very small, regulated and perfectly safe electrical charge into the wall just above ground level."

This ‘constantly-on’ system prevents water from rising, thus avoiding any recurrence of rising damp.

Some not-so-reputable companies may tell you that you have a rising damp problem when in fact it’s something else, like condensation or penetrating dampness. If possible, get an independent body to do an assessment of the problem before committing to a course of action to fix rising damp in your home.

The CSIRO stipulates that any physical damp course should be effective below suspended timber floors.  You can read their report here.

This should also be the case for injection/chemical damp courses. Put the damp course below floor timbers around the outside of the house approximately 150 millimetres above ground; inside, it should be put under the existing floor bearers.

To cure the dampness in your home, talk to a professional with experience fixing damp houses. You can find and expert, here.