What can we use to waterproof outside pebble dash walls?
We own a detached house which is approximately 100 years old and is part pebbledash and part soft 'red rubber' bricks. It has a damp course. We are looking for a BREATHABLE clear water repellent. The property is rented out and we have had some issues with condensation but have told the tenants that they must not hang loads of wet washing around which they have been doing.
We have been advised that there is a product manufactured by Thompson's and would appreciate your views on this product or anything else which you would recommend. We would initially do the brick and then if necessary/satisfactory do the pebble dash.
Judy Warnett
We have had this response from our expert Michael Holmes:
Soft red bricks are porous and so more likely to be prone to penetrating damp problems, which may be why part of your home (facing prevailing winds and driving rain) is covered in pebbledash to protect it. When temperatures fall below zero, saturated brickwork is prone to frost damage from expanding ice crystals, causing spalling, bricks will gradually crumble away, so you are right to deal with this problem.
First check that the brickwork is in good condition and the pointing is not worn or replaced with cement mortar, as lime mortar is key to helping keep solid walls dry out naturally – acting like a wick. Once the brickwork is repaired you could use one of several breathable (vapour permeable) water repellents that will prevent water saturating the brickwork, whilst allowing the building to breathe – preventing moisture from being trapped in the walls. The product will soak into the wall and chemically bond with it, and will not affecting the appearance of the brickwork in any way.
Well known brands are Waterseal (thompsonsweatherproofing.co.uk) Reno Dry (renotex.co.uk) Stormdry (safeguardstore.co.uk), Superseal (kingfisheruk.com) and Funcosil (remmers.co.uk). Using the wrong type of water repellent - one that is impervious and forms a film over the brickwork - can lead to problems in solid walls, so choose with care. It is also worth checking that the pebbledash is breathable, and not made from a hard impervious cement mix that is trapping damp and moisture in the walls. Painting a cement render with a breathable water repellent will not help – you will need to remove the pebbledash and restore the brickwork or replace with a breathable render or pebbledash.
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