"Rising damp is widely misdiagnosed in existing buildings, based on the incorrect interpretation of visual evidence and the readings of moisture meters. Because of a highly successful sales campaign for over 30 years by specialist remedial contractors installing injected 'chemical dampproof courses', this misdiagnosis of rising damp has also become synonymous with a diagnosis of a lack of an 'injected chemical damp-proof course'. Although this has been very good for business, it has often resulted in a waste of the clients' money and resources; original plasters and finishes have been destroyed in the process of installation, and unnecessary damage has been caused to original structures by the drilling of irrigation holes. In addition, money that might have been spent on more cost-effective maintenance or repair works has been wasted.
Whilst injected chemical damp-proof courses may provide some protection for certain types of structure if properly specified, their general application is rarely the most cost-effective way of controlling damp problems in buildings, and may be wrongly specified and ineffective. In particular the more generally available water based products may only form an effective ‘hydrophobic band’ if applied to a dry wall after it has dried out. This can prevent their effective installation in damp walls.
" ...Took this from the building conservation site.
It's widely proven that this type of, so called, damp proofing is seldom 100% effective, indeed if it achieves n% it's regarded by the companies touting them to be a success (read the small print) only a fool and his money, oh! and the misled, would buy this nonsense. Your own case is a perfect example, ye gads, injection course, crumbling bricks, covers popping off, what next?
http://www.heritage-house.org/pages/managing-damp-in-old-buildings.html
I think filling the holes with a coloured to match pointing mix, lime (if the walls are stone) cement if brick, will enhance your buildings look, it most certainly won't damage it, then let's try and figure out what's really causing the problem!
Start with the fact that the effected walls are around a fire hearth, could it be that the hearth has had no insulating against the structural wall, heating natural stone, or bricks not made to be refractory, over time could make them crumble, hmm! not likely. On the other hand acidic seepage mixed with damp, through to the wall might be the problem.
All of this is conjecture of course, what we need to do is establish the facts, like what age is the building? what is it's build i.e. What kind of fire is in the hearth now? and what preceded this?? Is there any other abnormality i.e. drains, sewers, lack of drainage and the like that you can ascertain??? ...pinenot
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