Unless you can confirm each of these three conditions then to be frank, your diagnosis is based on guesswork. On the upside, due to the use of waterproof renovating plasters no one will ever know you got it wrong! It is a fact that the application of renovating plaster provides the perfect cover up for bad surveying practice.
Do physical DPC's fail?
How has the Damp proofing industry changed in the last ten years?
It’s fair to say that that the process of retrofit DPC injection has been taken out of specialist hands over the last ten years. In the past expensive equipment and specialist training was required for injecting siliconate and stearate fluids into brickwork. These are still used but the market has moved more towards the use of aqueous silane creams injected into mortar bed and perp joints. The process is so simple that anyone with a reasonable degree of DIY skill can successfully carry out chemical injection. All that is needed is a hammer drill, a tube of your chosen water repellant cream and an application gun.
The cream is applied into 12mm holes drilled at 120 mm intervals which will then diffuse into the wall via the mortar course to form a damp course to BS 6576. The drillings are simply made good with re-pointing rather than being sealed with plastic plugs, as used to be the case. Moreover, aqueous silane creams are far safer to use than the old types of injection fluids and come with far less chance of user error; anyone who ever used these fluids will tell you how they burned in contact with the skin.
Retrofit DPC injection has always been a two part management solution with the internal re-plastering being as, if not more important, than the injection work. Plaster becomes defective when chronic damp dissolves the calcium sulphate within the plaster, which make it extremely porous but salt contamination is the primary reason to hack off and replace the plaster. These salt contaminants are hygroscopic and will continue to absorb moisture from the atmosphere causing the wall to remain damp. In the early days in was common for plaster to be hacked off and replaced with sand & cement render containing a waterproof additive that was then finished with a coat of Carlite finish. These days waterproof renders are rarely used with most contractors and specifiers opting for one in a range of waterproof renovating plasters that have become available. For the record, I am neither anti damp proofing industry or anti retrofit injection; I simply believe that the vast majority of damp buildings can be cured at source using nothing more than minor building works and the damp proofing industry would be best served by accounting for this fact.
I have both specified retrofit dpc injection and used it personally because pragmatically occasions do arise when you can do little else. What if a neighbour's yard has higher ground levels than yours and is draining against you gable wall? It is unlikely that lowering your neighbour’s ground levels will be an option. A truly independent and competent damp surveyor will not hold with extremist views that rising damp is a myth but will also understand that rising damp is incredibly rare. It is this reasoned and pragmatic approach that will leave him/her best placed to appropriately specify works to achieve a cure or a management solution. Wherever possible, a cure should always be the preferred option and retrofit dpc injection falls firmly under the heading of management solution.
Joe Malone BSc (Hons) ICIOB - Head of Asset Management - ALMO Business Centre Leeds
The writer of this article is an advocate of paid independent damp surveys and in no way endorses any damp proofing advertisement (PCA affiliated or otherwise) linked to this article.
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