A bit of a headline I admit, however, there are a number of very common situations where the recommended damp proofing techniques just don’t work. So the * is there for qualification purposes, as some damp proofing works, however it depends on a number of factors – the wall, the damp proofing system and the skills / quality of the installer.
The most common area where conventional damp proofing does not work is when dealing with older rubble filled solid walled houses. Sounds very specific, but actually this encompassed virtually all the pre-1919 houses in Wales and the UK. The common terrace is built from a mix of stone, brick and rubble. The walls are generally stone, with brick used where a clean finish was required (doors, windows, chimneys etc.) with the construction technique being to create two reasonably faced edges for the walls and then infill the middle with any old stuff and some lime mortar.
The stone used was a mix of whatever was available locally. Sometimes this meant the local stone, but in port towns and their environs, it was often ship ballast so this could have come from almost anywhere. These stones have different properties and this complicates the picture, however the main point is that the walls were a right mix of materials all held together by lime mortar.
This construction technique means that the walls are full of cavities, fissures, voids, so pumping a load of waterproofing liquid under pressure into them just means that the fluid travels the easiest route, whether this be up, down, across, whatever. So the treatment is not contained / localised where you want it to be. Consequently the damp proof line that is being attempted just will not be achieved.
Creams suffer the same fate, though to not such a great extent, as at least these stay where they are put, but you could find yourself using a lot of silicon cream and still leaving some gaps for the damp to travel up.
For rubble filled walls there are a number of solutions that will work (as long as they are specified and fitted correctly). These include
1. Electro-Osmosis damp proofing
2. Using the right renders, pointing, paints etc on the exterior walls
3. Correct drainage and heights of external floor finishes
So for individualised advice please contact the Eco Home Centre. Builders, damp proofing companies and building societies are generally wrong on damp and will just use damp proofing that at best only working in part and at worse can cause even more damp and insulation problems.