This method has been around for many years and involves drilling holes into the bricks, mortar joints (or both) at regular intervals and injecting a solvent or water-based chemical into the wall under pressure, until the wall material is saturated with the chemical (almost always siliconates) The chemical layer then controls water rising past it by actually ‘lubricating’ the pores and vessels inside the brick. This lubrication physically reduces the friction inside the brick that allows the moisture to be drawn upwards.
Disadvantages of this type of system are that you generally need to inject both sides of a wall (225mm or thicker) for it to be effective, you can inject from one side only BUT you don’t know what your injecting into once your past the first leaf of brickwork. Also you really need to see the whole face of the brick you’re injecting so that you can make sure enough of the product is being injected.
This type of damp proof course system is rarely used by professional users now and its main use is by DIYer’s who purchase the equipment from hire companies.
DPC Cream Systems
There is a much better system of installing a chemical damp proof course and is the primary system we use. It involves injecting a damp-proofing ‘cream’ into pre drilled holes. Ours is called CG one. The cream in injected into the wall from a caulking gun via a long nozzle.
With this type of cream system the injection of the cream is carried out into the mortar layer between the bricks. This is usually at a perpendicular joint to give approximately 2 injection holes per standard brick width.
An advantage of the cream system is that it is designed to treat thicker brick walls and can be inserted from one side only via deep drilled holes (if necessary).
The other big advantage is that because this is a low-pressure system you are guaranteed to get exactly the right amount of active ingredient into each hole regardless of the condition of the wall (of course we only inject walls that are in good enough condition to be treated in the first place!)
Cream-type damp proof course injection has become the standard for the industry, because of the reliability, ease, and quickness of installation.
The height of the new damp-proof course in relation to external ground levels and any floor timbers is also very important to ensure that floors are protected from dampness. Further information about this can be found from British Standard 6576:2005 (not reproduced in these web pages).