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.


Vapour diffusion through StormDry treated masonry


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.


StormDry test in Skipton, North Yorkshire


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.


  1. The Grim Reaper says

    The passage of air through a water repellent silicone based material is old hat, as are the Karsten tubes.Dunk a piece of silk/nylon in a water repellent and you will get the same result.

    Wacker used similar advertsiing in their brochures in the 1970/80’s

    • Dry Rot says

      Showing your (and my), age again eh?

      Old hat to you and me Graham, but still a great demo for surveyors, homeowners and Architects, some of whom still think that pure water repellent products somehow ‘seal’ the surface and stop vapour transmission. The problem is of course that there are many wall coating that do seal the wall, but these are not water repellents.

  2. Interstitial says

    Safe guard LS ? For limestone

    • Dry Rot says

      Ha, Hello Interstitial!

      Well done – In the past twelve months my good pals at Safeguard have developed and marketed their Limestone water repellent – It’s called Raincheck LS. This is a very specialised product and comes in a solvent base. Best used by specialists and preparation work is critical for success. The above post is accurate for its time – August 2011 🙂

      If you fancy applying it yourself here’s a link for this limestone water repellent.

  3. Nigel Anness says

    Interesting, I have a few questions.
    Does it change the appearance of stone, ie looks shiny?
    How do you know it lasts for 30 years?
    Is it possible to re point using lime?

    • Dry Rot says

      Hi Higel,

      Thank you for looking in. I’ve completed quite a few applications of various masonry surfaces and have yet to see it make a wall shiny. It doesn’t form a visible coating at all. That said, it will slightly darken or lighten the wall, depending on conditions. Of course when it rains in future the wall will look much lighter tan any adjoining houses as they darken with absorbed water.

      Stormdry has a British Agrement Board certification for 25 years. Siloxanes are know to be very durable and for year these have shown lasting water repellence at 20 years and longer. Stormdry penetrates deeply so will be much more durable. I have just treated my brand new house with it. I did this to protect the cavity fill insulation the house came with on the South and East facing elevations. I sent a brick to Safeguard first and the treated that and then cut the brick in half later. The product had penetrated 20mm deep in the stock clay brick! Remember that there is little point paying a good sum for a pure product like StormDry then applying it to dirty masonry. A good clean is crucial. or the cream will become a dirty paste, which will block pores in the masonry and reduce vapour permeability – a bad thing.

      If I was applying lime pointing I would do that first and do the Stormdry later so that the aggregate in the lime gets treatment. It will not harm the vapour permeability but will massively reduce rainwater wicking into the masonry units and bed-joints. Of course, I wouldn’t apply any water repellent unless there was a reason for it. Get your methodology right so that anything you do naturally follows on from your survey findings.


  4. Mark Arbuthnott says

    Hi there. Considering buying a listed building in NE Scotland constructed of sandstone,which has clearly taken a battering. Whilst I am not prevented in treating the stone I am advised against it due to the effect treatments have on the stone’s permeability. I am interested in the storm dry product because it claims to allow vapour diffusion. In your experience is this claim supported? Thank you very much.

    • Hi Mark,

      I’m sorry I missed your comment – hope this is still useful.

      The trick is to make sure the masonry is clean before you apply stormdry. It doesn’t leave any residue to block th epores so it will remain vapour permeable. If you apply to dirty surfaces you in effect make a ‘paste’ which will block the pores. Great for use in this application. Talk to Safeguard’s local sales rep – they are very good.


  5. Lorne Stoddart says

    This has been reccomended to me to be applied to ‘damp’ walls in my basement, once they have been extensively dried out.

    Being porous it will allow the hydro-static pressure / vapour to pass through the brickwork and not allow the bricks to blow.

    Would you use it in such application ?

    • Hi Lorne,

      No I would not use it. It is not designed for this purpose and is merely a rainwater repellent. It’s good but you will not see any benefit in this application.


  6. This product is amazing. I have a 105 year old house, we had one wall repointing with lime cement. It was then treated with storm dry.
    It’s like water off a ducks back, remarkable.
    Personally I can’t recommend this product enough.

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