Rising Damp: An Update for 2015

Rising Damp: A Salty Problem

A positive test for Nitrates using the Protimeter salts analysis kit but is it fit for purpose?

A positive test for Nitrates using the Protimeter salts analysis kit but is it fit for purpose?

Following on from my articles on rising damp written in 2013 I thought it was time to provide a further update on one problem in particular relating to the diagnosis of rising damp. In my update for 2013 I wrote that, ‘you need to confirm that three conditions are present to definitively confirm a case of rising damp.’ These are:

1. You must have a rising damp moisture profile. That is a profile that is wetter at the wall base but gradually decreases with height to a theoretical maximum height of circa 1.5m.

2. You must prove that moisture is present at depth in the masonry and it is not enough to take surface readings from the plasterwork. You will need deep wall probes or a calcium carbide (speedy) meter to confirm this on site.

3. You will need to confirm that nitrates are present in the damp apex of your moisture profile. This will involve doing on site analysis or sending a sample off to the labs. You might have noted that I’ve ignored chloride salts because these can be present in tap water or building materials. A positive test for nitrates confirms that the moisture has leached up from the soil.

The Academic Description for Rising Damp is Wrong!

My academic research into rising damp led me to the conclusion that most text books are wrong in their description of rising damp since they state that it is caused by capillary action. Since we know that the major moisture pathway for rising damp is the mortar perps and since we also know that the moisture transfer mechanism in mortar is diffusion then clearly the generally accepted cause by capillary action is incorrect. It is probably worth reprinting my own updated description at this point…

‘Rising damp is an upward migration of groundwater in masonry walls. It will act in combination on the masonry units and their separating mortar joints or it will act primarily on the mortar joints. The moisture transfer mechanism in masonry is capillary action whilst the moisture transfer mechanism within mortar is diffusion. The major moisture pathway for rising damp is the mortar perps so it can be stated that there are dual moisture transfer mechanisms for rising damp, diffusion and capillary action’

The purpose of this article is to right another wrong with regard to the academically accepted principle for salts analysis. If you note again the requirement to prove the third condition, the need to prove that Nitrates are present in the damp apex of your moisture profile. This requirement stems from the fact that Nitrates are present in the soil so if moisture is leached up from the soil then it stands to reason that the moisture contains Nitrates. Personally I have always used the chloride test very little since it has extremely limited value in the course of most damp investigations and it is a test that has always been of zero value for the diagnosis of rising damp, simply because we know that chlorides are present in tap water so a positive test for chlorides does not help us determine the source of moisture.

The Nitrates Anomaly

When testing for Nitrates we do so on the assumption that Nitrates are not present in tap water and therefore a positive result moves us to conclude that moisture in the masonry has been drawn from the ground. I’m only aware of one salts analysis kit sold by Protimeter and indeed this is the one I use. Interestingly, Protimeter do not make their own salts analysis tablets and these are sourced from a company called Palintest. However, we know that Nitrates can be present at very low levels. World Health Organisation guidelines stipulate a guideline for 50mg/l or less. So this raises a key question… Do we know that the tablets supplied by Palintest for the Protimeter salts analysis kit are discriminatory enough to give a positive test result only when Nitrates levels are above 50 milligrams per litre? If not, then the source of moisture cannot be determined using this test since a positive result may also be obtained when the source of the wall base damp is a leaking incoming water main containing Nitrates at low levels of 50mg/l or less? If you have used the Protimeter kit you will know that a positive test for Nitrates turns the water cherry red and there is no colour chart to match against your sample to help determine the approximate quantity of Nitrates present. The practice of matching the sample colour obtained against a colour chart is a principle that may be familiar to a lot of freshwater fish enthusiasts since they have to regularly check Nitrate levels in their fish tanks to ensure levels do not become so high as to become dangerous for their fish

Colour chart to determine nitrates level

Colour chart to determine nitrates level

The Protimeter test for Nitrates appears to be less discriminatory than the test used by freshwater fish enthusiasts since it will turn cherry red and give a simple positive result with no clue as to the level of Nitrates present.
I was uncomfortable with this and decided to contact the technical team at Palintest to ask them how discriminatory the Nitrates test was?
They were incredibly helpful in providing the following response…

‘Your question is a good one. I’m afraid you won’t ever be able to be certain that the nitrates don’t come from the tap water. The test doesn’t know the source of the water, it’ll just react to any nitrates present.

You’re also correct that the limit for nitrates is 50mg/l.

What I would recommend is to test the tap water on the site to test the ‘baseline’ nitrate level. If your ‘real test’ is higher than this, you can be sure that some nitrate is coming from the rising damp. If it’s less or equal to the baseline though, you aren’t going to be able to tell.

You could expand your test protocol to include other minerals (sulphate, chloride etc) which would be able to give you some more confidence that the water is from the ground as opposed to the tap but you would need more equipment and would be a bit more complex than your current method.’

Screen Shot 2015-09-20 at 09.58.06Before I even asked the question of Palintest I was already experimenting with a Nitrates test kit manufactured by Salifert. I chose this particular kit since I’d read on most forums that this was generally thought to be the most accurate kit. The kit is supplied with a colour match chart and is significantly cheaper than the Protimeter test kit. In fact I had been doing precisely what was recommended by Palintest… I was and am testing the tap water to establish a baseline Nitrates level according to my Salifert colour chart before I take a sample from the wall. The advice given by Palintest is good but of course ignores the issue relating to the absence of a colour chart in the Protimeter kit. It would seem that I was being advised to use another kit since the Protimeter kit can not discriminate and will simply, ‘just react to Nitrates present.’


Nitrates Test result of 25mg/l

Nitrates Test result of 25mg/l

In this image you can see where I have obtained a positive test result for Nitrates at a level of around 25mg/l but this was for a tap water sample.

My trials and research with this alternative test method are still ongoing since rising damp is incredibly rare and to date I have only obtained negative results from walls and positive results from tap water. I will need substantially more time to evaluate the effectiveness of my alternative Nitrates test but what is clear is that an alternative test is needed or some refinement is needed in the Nitrates test kit currently used by most building surveyors or damp investigators.

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External Wall Insulation Defects

External Wall Insulation Defects Being Built in

External Wall Insulation Defects Being Built in

Wherever possible we try to take the time to monitor ongoing external insulation schemes and we are currently monitoring two Midlands schemes to add to our knowledge base. The picture of the high rise block clearly shows that EWI defects are being built in and this is fairly obvious even to the casual passer-by. The insulation panels have been bonded with adhesive to the block but this does not mitigate for the reduction or complete omission of mechanical fixings. This is a high rise scheme and it is our opinion that premature failure is inevitable. The second scheme is a low rise scheme so on the upside, if things do go wrong then it is easier to inspect and access costs are not prohibitive for remedial works. However, this is a scheme using EPS insulation boards. We have to assume that the boards have been fixed with adhesive but again this does not mitigate for the lack of mechanical fixings; in this case only one fixing per board has been applied and there are no additional fixings around window and door openings. Generally these need to be placed at a maximum of 300mm centres around window and door openings.

Previous Research


Low rise scheme using EPS boards. Note lack of hammer fixings

We had a paper published in the Construction, Research and Innovation Journal in December 2013, entitled ‘The Risky Business of Covering Up.’ This paper heralds an early warning with regard to our belief that we will see a glut of external wall insulation failures, particularly on high rise blocks. These systems are often supposed to have a 30 years design life but very few clients will achieve these life spans unless they understand the requirements of their individual system BBA certification and stringently monitor site works to ensure that the BBA certification is being complied with. In our experience, there is often a complete failure to adhere to the BBA certified installation process.

EWI Installers are Getting Nervous

There was an extremely interesting development to this blog that I have been meaning to deal with… In fact I was contacted by the constructor concerned and requested to take the blog down. I’m not prepared to do that, it’s an academic blog that is aimed at continuous improvement so I do not feel that it serves the industry well to keep these issues hidden. The point I particularly wanted to deal with was the claim that pinnings to the insulation boards were only temporary and the intention was always to go back and install the required amount of hammer fixings once the adhesive had dried. Of course to try and confuse the issue with this claim is akin to admitting that you are putting the general public at risk… These systems are load and wind tested according to the number of hammer fixings installed and adhesive bond does not form part of the load test assessment. If a system insulation board is required to have 5 hammer fixings then this is required to satisfy structural adequacy. If you then claim that a reduced number of temporary fixings have been installed then you have actually installed a system that is structurally unsound (albeit temporarily) and at risk of falling from the building until the required number of permanent fixings are installed. I do hope that this is not a common approach for installing EWI but I really don’t believe it is since the process of installing ‘temporary’ pinnings would neither save time or serve any useful purpose.

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