Rising damp, penetrating damp or salt contamination? Why is that wall damp?
A month of so back I had the great pleasure of Graham Coleman’s company for two days here in Yorkshire. Regular visitors will know Graham, from past posts which he either contributed or featured in. For those that don’t know Graham, he is the Chief examiner for the Property Care Association; a career scientist with particular skill and knowledge of damp diagnosis and timber infestations. He’s the damp proofing industry’s technical guru…
He’s also become a good friend, as we have so much in common and he’s great fun to be with. Graham offered to come to Leeds, to spend time in my new gravimetric testing and salt analysis lab, which was set up with his help. Whilst this testing is not rocket science (nothing in damp diagnosis is), it is a little more complicated than normal and using a big chemistry set to search for ground salts in masonry and separate out hygroscopic moisture from capillary moisture is not something I do every day. (Graham’s been doing it for decades).
Our first session was spent extracting salts from plaster and masonry samples for testing and then using the chemicals in the lab, to cause reactions, which indicate the nature of the salts present (if any). There are test strips and such, including tablet test kits but these tend not to be as accurate and I wanted to see the reactions for myself, to gain full understanding of the techniques described in past technical papers.
This went well and Nitrate’s and Chlorides were detected to various levels in some of the samples. This was expected because my work with gravimetric testing of these samples earlier in the month (see this recent post on this method of damp diagnosis) had indicated that some had high hygroscopic moisture present. As hygroscopic levels were high, this implied contamination, but the salts testing Graham has schooled me in sealed the deal and confirmed the suspicions…. Great stuff.
Why bother? Well there are times when a damp situation needs to be dissected down into the components of the moisture, so that the source of the damp, which may have been indicated with visible or moisture profile work, can be further refined. It’s a great additional tool for me and my customers. Rising damp, penetrating damp and condensation usually look different (see my very basic guides on damp here, here and here), but sometimes these may overlap or there could be a dispute and more accuracy is called for.
Later sessions included spread sheet work, to produce workable data sets from the damp readings; separating ‘free water’, such as rising damp, from the salt derived hygroscopic moisture, and develop graphs to help clients understand the data too.
The combined techniques of gravimetric damp testing, to establish moisture profiles, along with salt analysis is the most powerful tool available in accurate damp proofing diagnosis. Though it is just a tool and needs to be combined with on-site visual inspections and a good knowledge of damp in buildings and building technology. As a damp proofing specialist it also helps me to check my own damp survey findings, against the lab results. Fortunately so far, the gravimetric damp testing has confirmed my conclusion reached on site during damp surveys, which is some comfort but, actually I am looking forward to getting ‘caught out’ it’s the best way to learn.
I must stress that anyone using this method should always profile the wall in question and take control samples from unaffected areas too. ‘One off’ sampling using this method or a carbide meter is prone to mislead.
My thanks go to Graham Coleman for his great generosity in sharing his many years of experience. He’s an honorary member of the Property Care Association, which is a well deserved tribute to such an important contributor to the knowledge of scores of PCA members, their staff and the care of our customers in turn.
Please visit Graham’s web site and contact him for training services and damp and timber consultancy.
For advanced damp diagnosis in Yorkshire please visit my main web site below, where you can check out my little firm. We can help with damp proofing, woodworm, wet rot dry rot and all damp related building defects. All my staff are highly qualified and as enthusiastic as I am, so do please check us out.