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Blog - Technical Corner: Efflorescence

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Technical Corner: Efflorescence

Commonly known as 'salts' efflorescence is a phenomenon that can affect all products that incorporate stone or cement products. You may have seen it on the outside of brick buildings coming out like a white bloom, especially on cold but sunny days. In its most harmless form, the slats essentially do no harm to your building whatsoever and may just be a bit displeasing cosmetically, but efflorescence or 'salt contamination' to plasterwork internally can be a source of great frustration and very frequently be the start of a proverbial goose chase. I've lost count of the times I've visited a property to be shown a suspected roof leak, normally around a chimney stack on a top floor bedroom, only to explain the real cause is linked to salts. It's no wonder why so many people look at me like I have two heads; one woman actually asked me to leave after I ruled out her roof and explained I believed it was salt contaminated plasterwork; in fairness I had wanted to leave from the moment she opened the door dressed only in her nightie! I did duly leave and the anecdote goes some way to explaining how confusing and frustrating the problem can be.

The cause of salt contaminated plaster lies not in the plaster, but in the cement behind it. When the wall is constructed, the cement (and in some cases the bricks) can contains salts that lie inertly within the wall. The trouble comes when these materials get wet or contaminated with other chemicals, for example, like the chemicals in smoke from a fireplace. This can activate the underlying salts which are then drawn to the surface via the plaster. The salts will generally appear as bubbled or damp paintwork as it tries to escape from underneath. The confusing element is that the salts, just like table salt or any other salt, attracts moisture. Often before salts even appear on your wall or ceiling you have a damp patch which is commonly mistaken as a leak. My favourite example of this is when one client's 'roof leak' continued even after the chimney had been removed. To further confuse matters, there's normally been a leak of some kind to start the process off, so you can dutifully appoint a roofer to fix your roof (or completely remove your possibly redundant chimney) but still find the problem persists. Understandably, many people blame the roofer accusing them of not curing the leak but that's not always the problem. Salts in plaster can be cured via a combination of methods but all inevitably mean replastering (incorporating specialist blocking layers) and redecorating the affected area. The key thing as always is to get good advice. At CRB, we always carry damp meters and myself and Scott are both trained in how to diagnose damp problems and resolve them, be it rising damp, failed damp proof courses, roof leaks or salt contamination. This level of expertise in both roofing and building allows us to expertly pin point the areas of concern and can save you thousands of pounds in unnecessary repairs. If you have a problem with damp or salts, give us a call and we'll give you a free damp report with conclusions to specific repairs that will offer you long term, trouble free success. 

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