The Effects of Water Repellents on Porous Masonry

Like most people who are passionate about their careers I make the effort to stay well informed, upto date and educated. I'm constantly reading new codes of practice, amendments to building regulations and publications. I enjoy social media too, I like interacting with other professionals with whom I share ideas and knowledge. I do however try to ensure that anything I post, practice or preach is based upon a sound foundation. Like many industries I presume ours is no different, there is a lot of information to sift through some of which is scientific and factual, the other simply fabricated based upon opinion. So whenever, i'm presented with new information / opinion i'll always try to establish it's source and level of credibility.

So Peter Ward........ I can just feel the eyes of some my industry friends and colleges rolling to the back of their heads, but here me out! I often see Peters work online and always take the time to watch and listen. Peters an avid sceptic of our industry and dishes out a fair amount criticism. If I'm honest however, I do share some of Peters concerns and also believe there are far too many wallies pretending to be experts. I know this because we follow them around!. I do genuinely believe however, Peter only has his clients and their buildings interests at heart, which is commendable. I also believe however that some of the information he shares is just opinion or outdated knowledge. Our industry has progressed dramatically over recent years with much thanks to training provided by the likes of the Property Care Association (PCA). As such, there are now more than ever, a lot of well educated surveyors providing sound, knowledgeable and credible advice to their clients.

Lately I was watching one of Peters videos about flood resilience in old buildings where Peter and Corey were discussing some of the resilience measures that had been introduced into properties to either defend against or reduce the risk of future flooding. Peter used an example of an old stone building which had been treated with an external masonry water repellent which Corey described as a 'weird and wonderful chemical'. Corey's perspective on these type of treatments was that the cream would cause "bedlam" to the masonry accelerating erosion as it trapped moisture within the structure. An analogy of expecting washing to dry in a plastic bag was used. The so called magic cream, was a bad idea!

Now don't get me wrong, I too struggle to find justification for applying a masonry water repellent to an old stone building particularly if it's listed, I simply believe there are other alternatives that could be considered. A well designed and implemented maintenance regime using sympathetic materials should be all that is required. It is however, not the opinion that I'm concerned with, it's the suggestive effects of the water repellent that causes me concern. As I mentioned before, often we find that peoples perspective or understanding of certain treatments / repairs maybe founded upon previous experience, an outdated view based upon old information or simply a lack of knowledge.

The water repellent was referred to as a magic cream, and there aren't that many water repellent creams on the market so I decided to look into the technical claims of these creams.

I've always been led to believe since the introduction of these new hydrophobic creams that they were in-fact breathable and do not change the dynamics of how the material evaporates moisture once applied. But again i'm relying on manufacturers information here and they would say that, wouldn't they?........

So, I wanted to see if there was any truth in Peter and Coreys claims?.............

Time for another experiment. So, I decided to create my own in house experiment to establish the truth!

So how to do this?.................I'd need some wet material, a masonry water repellent cream and of course a plastic bag. I'd also need some way of measuring the moisture content of the material once the cream had been applied and a programme to establish if the water repellent was in fact inhibiting the materials ability to evaporate moisture like the plastic bag analogy.

Here's my plan.

I'd use three new limestone pillars which have been in our laboratory kept in dry conditions for the past six months. I'd weigh the pillars in the their current dry condition and also take readings from each one using an electronic moisture meter in both surface pin mode and radio frequency mode. These details would be recorded as the pillars established dry condition.

Three new limestone pillars

Each pillar was weighed and test electronically, readings recorded as established dry condition.

I would then coat just one of the pillars in a masonry water repellent cream. I used Safeguards Stormdry as I already had some in stock and I presume this was the cream both Peter and Corey were referring too. I coated just one pillar entirely, all sides and the top except for just one inch of the bottom, where I would stand the pillar in water. The other two pillars I left natural without treatment.

I then stood all three pillars in a plastic container and filled the container with one inch of de-ionised water and left the pillars soak up water via capillary action for one month. I specifically used de-ionised water as I didn't want water bourne salts in the pillars which could possibly influence their weight, especially if I were using weight as a method of measurement to monitor their moisture uptake or loss.

I monitored the pillars visually in the water for a month just topping up the water as and when required. After one month I removed all three pillars.

After re weighing each pillar, I again took readings from each with an electronic moisture meter (i marked the pillars with a pencil so i could be sure i took readings from the same location consecutively as the pillars were stood to dry). I recorded these details as the pillars known wet weight. Finally I placed the third untreated pillar in a sealed plastic sandwich bag and re-weighed.

As expected each pillar gained weight, basically water uptake through capillary action.

Pillar one - dry weight 699 grams / wet weight 744.5 grams / uptake 45.5 grams

Pillar two - dry weight 742.5 grams / wet weight 789 grams / uptake 46.5 grams

Pillar three - dry weight 687 grams / wet weight 739 grams / uptake 52 grams

I now stood the pillars out of the water to dry. The intention was to re-weigh and take new readings from each pillar daily to monitor how effectively the pillars dried, if at all. I would consider the pillars dry when each returned to their established dry weight and equivalent moisture content.

I would therefore have one treated pillar, one natural pillar to compare it too and one other natural pillar wrapped in a plastic bag. Hopefully i'd be able to evaluate if Peter and Coreys claim was accurate, would the treated pillar dry no quicker than the pillar in the sealed plastic bag due to the effect of the water repellent?..................

Fast forward just 7 days, I was amazed at how quickly the pillars dried down even in the normal atmospheric conditions of our office. The bulk of evaporation occurred within just the first two days where the weight and measurable moisture using surface pins dramatically reduced. After this period I was only able to monitor water loss via weight and by using an electronic moisture meter in radio frequency mode.

On day 7, the untreated pillar no: 2 returned to it's prior dry weight (742.5g), with radio frequency readings almost the same. Pillar 1 which had been treated with stormdry wasn't however far behind with just 6 grams difference before it returned to its prior dry weight. On a daily basis however pillar one and two dried down almost simultaneously as can be seen on the graph below.

So what about pillar 3, the untreated pillar wrapped in plastic?

Well, of course it hardly changed. Over the period of one week the pillar lost just 1.5 grams (out of 52g uptake) into the plastic bag. On day 7 we still had a very wet limestone pillar.

The following graph shows the reduction in electronic readings taken from all three pillars during the experiment. You will note the readings taken from pillars 1 & 2 reduce after being left to dry, whilst pillar 3 shows no difference since its initial capillary uptake.

The following graph shows the reduction in weight loss taken from all three pillars during the experiment. When viewing the graph you should observe the trend rather than the difference in weight as not all pillars weighed the same at the start of the experiment. You will see the trend on pillars 1 & 2 is the same, indicating the water repellent coating made no difference to the evaporation of moisture from the pillars. Pillar three shows no loss in weight since its initial capillary uptake. This was the effect of the plastic bag preventing evaporation.

SYNOPSIS

As can be seen from the results of my very basic experiment the application of the masonry water repellent to the porous limestone pillars had no real measurable effect on the stones ability to evaporate moisture. Therefore the analogy of "washing in a plastic bag" I believe i can say is inaccurate. Peter and Coreys view maybe shared by many in the conservation world however, the basis of their judgement i suspect is founded on opinion and out dated knowledge rather than fact. That's fine and they are of course entitled to their opinion, i just wish they would express this as opinion rather than fact.

At the end of the experiment there was a difference of just 6 grams between pillar 1 and pillar 2 and i now must express the likelihood is, that difference is probably due to the application of the water repellent itself. It was only upon sumerising the experiment did i realise that i had weighed the first pillar prior to treating it! A silly mistake, especially when i was trying hard to ensure the experiment was a concise and accurate, but hey, no one is infallible. Its a small error, if that, and one which doesn't detract from the purpose of the experiment.

Finally, i would just like to express that i have not been paid or incentivised to publish this article on behalf of Safeguard the manufacturer of Stormdry. I simply used this product as i had a sample at hand.

If you've made it this far, I hope you found this article useful and somewhat informative and if you have any questions or queries about this subject please don't hesitate to get in touch.

Happy surveying

Russ

If you would like to learn more about damp, moisture mapping or damp diagnosis you may find the following articles useful:

Salt Decay in Masonry

https://www.dhirubhai.net/pulse/moisture-salt-decay-masonry-none-scientific-well-worth-rafton-/

Industry Perception Study

- https://www.dhirubhai.net/pulse/industry-perception-study-russell-rafton-/

Moisture Content Analysis - https://www.dryfix.net/blog/explained-moisture-content-analysis-using-the-gravimetric-process/

Russell Rafton - Dryfix Preservation Ltd Senior Surveyor

Dryfix Yorkshires Leading Damp & Timber Specialists

A 4 x Industry Award Winning Company with the Property Care Association.