Chemical Damp Proof Course

A chemical damp proof courses was initially, installed using high or low-pressure injection (40-150 psi) of water-repellent silicons or aluminium stearate into injection holes drilled into ether brick, stone and mortar of a wall in a specific pattern specified by the installer.

The use of high pressure injection of the 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 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.

injection of cream chemical damp proof course without pressure
injecting a cream to create a DPC
chemical damp proof course high pressure injection pump and lances
Injection pump with lances for a traditional chemical DPC

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 to be framed and lined do not need to be plastered on the hard as there is no salt transfer to the d├ęcor finish.