The methods for installing a new DPC are described generally as ‘traditional’ (the insertion of a physical DPC) or ‘non traditional’.  We strongly recommend that you consider only those that have been awarded an Agrement or other third party certificate. Chemical injection is the only method that satisfies this requirement and is the only method which BRE considers suitable where it is not suitable to insert a physical DPC.

Physical DPCs can only be placed in brickwork or coursed stonework, random stone walls or rubble infilled walls are not suitable. Chemical injections systems can be used in most types of structure.

The success of chemical injection systems depends on the efficiency of the fluid penetration of the damp structure. The repellents are injected or transfused into closely spaced holes in brick or mortar courses along the DPC line. Treatment must be carried out at different depths to ensure penetration through the entire thickness of the structure. The transfusion methods, carried out at low pressures with aqueous repellents should, in principle penetrate more effectively than high pressure systems since they depend entirely on diffusion processes which are the only processes that can eventually give complete penetration.

The method is to inject the silicone fluid into the wall under pressure to saturate a horizontal band of masonry to form a damp proof course. With the materials used in the construction of houses in Spain the process is a little different in that the hollow clay pots are flooded and the fluid then soaks into the wall to from the DPC. The silicone fluid lines the pores of the masonry and stops capillary action within the wall. The chemical injected into the wall is classed as an irritant and when in the wall it dries and gives off no vapour and will not leach out so there is no risk to humans or animals.

As with all forms of damp control there is a need to remove all salt contaminated plaster as these walls are hydroscopic and will attract moisture from the atmosphere and always appear to be damp. The re-plastering will contain a salt inhibitor to prevent salts passing through the render during the drying out of the wall.