A Chemical damp proof course were Initially, installed via high or low-pressure injection pumps (40-150psi) of water-repellent silicones or aluminium stearate into injection holes drilled into ether brick, stone and mortar of a wall in a specific pattern.
The use of high pressure injection pumps to install a chemical damp proof course has declined over the years, also the water or organic solvent-based damp chemicals have been mainly replaced with silane/siloxane creams using a low pressure using Skeleton gun or pump applicator, the damp-proofing cream is inserted into a pattern of drill holes in the appropriate mortar bed joint rather than into brick or stone etc. The type to be used will be suggested in the inspection report.
These hydrophobic chemicals form a non-wetting surface within the capillaries, this makes the capillary wall slippy and controls upward creep of water and thereby controlling rising damp.
In addition to the installation of a chemical damp proof course, the issues of residual moisture and hygroscopic salt contamination have to be addressed. This process has two stages: firstly, the contaminated plasterwork on the hard is removed, thus alleviating the initial problem; secondly, the plasterwork is reinstated using a specification render designed to prevent hygroscopic salts and residual moisture in the underlying masonry wall from affecting the plaster wall surface.
Reinstating plaster on the hard is typically undertaken using low-permeability cement renders or a vented cavity drain membrane. Walls that are framed and lined do not need to be plastered as there is no salt transfer to the décor finish.