Masonry Water repellents have grown up

Before I begin I should admit that in the past, I’ve been a bit critical of water repellent treatments applied to walls. Penetrating damp is usually more to do with ropy pointing and leaking gutters than porous walls and it’s essential to get these fundamentals right first.  Sometimes though, in exposed locations, moisture tracks in, through no apparent gaps or cracks.

The technology is proven and water repellents have been around for decades.  However, messing about with the external fabric of a wall, with chemicals (especially invisible ones), always seemed a bit ‘dodgy’ to me.

Why so, when I’ve specified chemical injection DPC’s all over Yorkshire for years? Well I see spalling bricks and stone all the time and water repellents don’t really penetrate that deep; they are not injected into the wall, they just coat the surface.  What if for some reason, water was trapped behind the surface and pushed it off? Or worse still, water in liquid form freezes just below the surface and we have spalling again. This could be a big problem, particularly on listed buildings, of the type I’m often asked to look at.

With most older treatments, based on solvents (yes – I am that old), I became convinced that washing down a damp wall with this stuff was all a bit ‘wrong’.

Clever formulators developed water based repellents, though some;like Potassium methyl siliconate, reacted with pollution deposits on blackened buildings, turning these white, so I still avoided.

Now though, there’s another innovation. StormDry is a cream formulation and it’s joined several other creams which promise more; all the benefit of silicone water repellency, without the high risk of spalling. Promises are one thing though; what are they based on? A need for sales, or proven testing?

I’m encouraged, because StormDry is manufactured by Safeguard Europe, of Horsham in Sussex.  I know these guys; they are passionate about product performance; rather than solely quick sales figures. I visited their factory a bit back and was impressed by the dedication and detail they apply to research and development.

They’ve worked on the formulation for years and showed me the electron-microscope images of masonry treated with it; there’s no visible residue in the pores at all. Images of other formulations revealed a snotty looking goo, coating the surface and in some cases blocking the pores.  They’ve gradually reduced this problem and now there is no impediment to vapour passage. hence the product launch.

Vapour Permeable

The following is Safeguard’s demonstration of Storm Dry’s microporous nature; it’s breathable and will not ‘seal’ the wall.  Here, a small amount of water is supported on top of a StormDry treated slice of masonry, which does not absorb the water. Air is being gently pushed in the bottom end.  Natural vapour pressure is always from inside a house to the outside, so whilst this is an exaggeration of that pressure, it does illustrate the principle very well.

Since starting my own field trials through Deepshield and Brick-Tie Preservation, I’ve completed about twenty projects and I’ve kept an eye on them all.  It’s too soon to know about any spalling issues but at a year old, the following job has had a very cold winter to cope with.

This is a semi-detached house in Skipton, North Yorkshire, with a problem caused by penetrating damp across mortar droppings on wall ties in the cavity wall.  Skipton is on the edge of the Yorkshire Dales and gets plenty of wind driven rain. The obvious solution is to clear the cavity, so it works as designed, but this is 50M area and made of stone; a hell of an expensive job; finding all the ties and clearing them of mortar; disruptive, time consuming and beyond my client’s budget.

We applied StormDry last year and now I’m back to survey the adjoining house. Not one to miss an research opportunity I took along one of Safeguard’s StormDry gauge kits (a fancy Karsten tube kit).

The kit includes several tubes, which can be sealed against the wall with sticky sealing rope, so that water, injected into the tube, sits against the wall, with nowhere to go,other than be sucked into the masonry by capillary action and a little help from gravity.

With my potential new client in a attendance I carefully sealed the tubes to the front wall; one on the left (treated wall) and one on the right – naked wall.

The video tells it all.  I placed the tube cups over the ‘T’ joints so that the water pressure was presented to the bed-joint and the stone.

The untreated wall drank the water up, particularly the bed-joint – it spread around the patch.

The treated wall was completely resistant; with beading and absolutely no absorption of any of the water.

Bear in mind that the thick creamy consistency means this is an in-depth treatment.  The high loading, which the thixotropic nature of the cream offers, gets right onto the masonry – far more than a quick spray with water-like fluid. It’s a tribute to the Safeguard team that all of this thick cream is absorbed with no residues at all; all the ingredients are essential and the formulation contains no waste contaminants or ‘fillers’.

This means virtually all the water hitting the outside wall as rain, just bounces off; the water molecules being more attracted to each other, than to the masonry.  Water vapour, passing out from the dwelling is unimpeded and evaporates away naturally.

Energy saving water repellent?

A extremely useful by-product is a wall which in keeping dry, loses far less heat after rainfall.  It’s a well known preservation anecdote that “A wet wall is a cold wall”.  The design team recognised this and have had Portsmouth University extensively test these assumptions.

Now they’ve proved that average walls heat loss can be reduced by up to 29% with just one StormDry treatment. At last, an insulation aid for those living in houses with solid external walls, where cavity fill insulation is out of the question. Thus solid walls get a double benefit; no penetrating damp and increased thermal insulation.

This can have additional benefits in fighting mould growth, caused by cold wall surfaces, bringing air in contact with them, down to ‘dew point’. I’m excited by this or I wouldn’t have taken the time to blog it.

Practical Considerations.

This is no magic bullet and a specialist is the person to ask about specification.  Application is easy and anyone can do it, but like any treatment a proper survey by a qualified and experienced surveyor is essential.

Oh; don’t apply it to limestone; the material has no affinity for it and it will not work (nor will any other water repellent). There’s also no point in applying any treatment to a dirty or algae covered wall – clean it first; the North Yorkshire property featured above was jet washed of debris the week before we attended; though a stiff brush is adequate in many cases.

There are some other caveats too…..this is a permanent change in the dynamics of a wall; use a specialist for diagnosis and specification.

My thanks go to Safeguard for the use of the Vapour diffusion video.

Dry Rot.