Chemical Dampproof Cours


Over the past 20 years, a wide range of systems have been used to prevent rising damp. These include both practical and obscure methods, some which have been short lived, due to difficulty in installation, dubious effectiveness and in some cases, detrimental effects to the treated building.

Pressure injection chemical dampproof courses have been successfully used for over 25 years and is a nominated method on restoration projects throughout the world.

The Westox Injection System has consistently been used by Restoration Bodies on many of Australias oldest buildings, ranging from Victorian Terraces to major conservation projects. The advantage of this injection system includes the level of installation which may be lower than some other commonly used methods. This provides protection to the skirting boards and can avoid dampness bringing through new plaster. Speed and cleanliness of installation are two other factors in arriving at an objective choice.

Approved applicators of the Westox Chemical Dampproof Courses carry out a careful survey of the problem and provide a written report and quotation. Enquire today to contact our Approved Applicators.

As an accurate diagnosis is critical in making an appraisal of any dampness problem, an electronic meter is used to assess moisture content and to identify it’s source. It is not uncommon to see properties treated at great expense for rising damp when the problem could be as simple as a broken down pipe or other minor repair.

After the installation of the new damp course, the walls will gradually dry out. Depending on the moisture content and the thickness of the walls, this could take in excess of one year. The replacement of all damp affected plaster is essential to prevent secondary dampness.

Salt contamination of the old plaster is caused by the moisture containing salts, rising up through the capillaries of the brick work from the ground below. These salts build up in the plaster over a period of time and attract airborne moisture. It is the expansion and contraction of these salts which cause the familiar rising damp symptoms of eroding and blistering paints and plaster. The major proportion of the salts are removed with the old plaster. The new render is designed to allow the passage of water vapour, so that the residual moisture can dissipate from the wall. With the use of a special formulated cement additive called Westox Salt Retarder, the old plaster can be replaced soon after the installation of the new dampproof course.


Westox 50 is a low molecular structure alkoxysiloxane solution formulated to provide maximum penetration in both brick and stone

 Colour                                      Clear

 Volume Solids                       6/7%

 Components                          One

 Package Size                          20 Litre Drums

 Notes              For specialised applications, we have alternative injection fluids available


The rate of fluid used will be relative to the porosity of the materials and the thickness of the walls. As a general guide the fluid requirements are in the region od 1.5 – 2 Litres per 110mm thickness of wall per lineal meter.


On the commencement of a typical rising damp project, the applicator removes the skirtings. Skirting may be refitted after the installation of the chemical dampproof course and the completion of replastering. In some cases the skirtings may be rotten and require replacement.

The damp affected plaster is then removed to expose the brick stone.

After selecting the course of brick or stone which will become the new dampproof course, as series of 10mm holes are drilled at an appropriate depth and spacing.

The injection lances are then introduced into the holes and a seal is formed by a rubber expansion washer which holds the lance firmly into the brick or stone.

The selected Westox Injection Fluid is then pumped via flexible tubing into the brickwork and the fluid, now under pressure is forced through the cappilaries of the brick or stone until is is visually evident that saturation has taken place.

The lances are then removed and the procedure repeated progressing along the wall to be treated. The injection fluid continues to penetrate through masonry and mortar joints by capillarity for approximately 24 hours.

After the full thickness of the wall is injected the continuous saturated section of masonry will become the new dampproof course. After a short drying period, the walls may be replastered to complete the job.


After the ‘drying out’ period (minimun 7 days), the walls are to be replastered to the following specification:


40 parts fresh water to 1 part Westox Salt Retarder (eg 20 Litres of water to 500mL Salt Retarder).


1 Part OP Cement

3 Parts washed sharp plastering sand.

IMPORTANT: do not add lime, plasticiser or any other additives.

Mix to a workable consistancy and apply at a minimum thickness of 10mm.

After overnight drying the wall may be set finished with a mixture of hard wall plaster and hydrated lime. Should a sponge finish of render be required, a second coat of render may be applied on the same day as the salt retarding coat. This finish coat is to be of 6 sand, 1 cement, 1 lime.

After adequate drying, either the original or replacement skirtings may be fitted.


Store in a cool, dry place