A cautionary tale!
Most initial the diagnoses of dampness are undertaken using an electrical moisture meter (qualitative method of moisture measurement) - and quite understandably so: they are quick, clean and non-destructive.
Perhaps, as a result, high readings and a suitable pattern of readings are obtained and rising damp is diagnosed following which a chemical injection damp-proof course is installed. Fine.
But several years later a damp problem recurs (not condensation) which appears remarkably like the original problem. The contractor returns to site and initially checks with an electrical moisture meter and obtains readings and similar patterns of readings as in the original survey. But now he introduces the Carbide meter (quantitative analysis), takes a sample and declares the moisture levels are 'acceptable' and there is no problem with the damp-proof course, etc.
The question must now be asked is that if electrical moisture meter readings are now similar to those obtained originally and the actual moisture levels are deemed to be acceptable using the carbide meter, how then how was it determined originally that similar electrical moisture meter readings didn't reflect the same 'acceptable' moisture levels???
The moral of the story? If high readings are obtained after work has been done (that assumes leaving a reasonable time for drying, and that other factors such as condensation are not interfering) then it suggests something is wrong, or perhaps not as it should be. This may need to be investigated further, and in more depth (See 'Evaluating the performance of Chemical Damp-proof Courses')
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