Painting External Rendered Wall - PROBLEMS!!!

[Trinity1832]

I painted the whole of my houses exterior walls last year (May / June). The house was built in 1832 and has quite thick solid masonry walls with an exterior render which is painted white. The house has very limited / no ventilation i.e. opening windows, wall vents etc. and therefore naturally breathes (or so I'm told).
The house was un-occupied for 2-3 years prior to us moving in and subsequently damp was present in some rooms! I painted the house exterior after approx. 15 months of moving in.

I cleaned off the old flaking paint the best I could and applied 2 coats of a water based masonry paint (nothing particualr fancy, Wickes own brand I think). Following avery cold winter in 2010-11, I noticed in Jan 11 that the paint had blown in certain areas with large sections falling away / blowing off in the wind. It is mainly the lower sections of the wall which has flaked off - the upper section is partially protected as the roof over hangs by approx. 1.0m.

I was planning re-painting the walls but am not sure on the best course of action (preparation, products etc.) Does anybody have any advice for a novice painter? Thanks

 

[TheDec]

Trinity,

Tell me please before you you decided to to re-paint your house, did the existing paint work appear in any way chalky to the touch. In simple terms if you were to rub your hand over the surface did it leave a chalky residue.

Dec

 

[Trinity1832]

Dec, thanks for your response. I'm new to the forum thing so not sure if I have responded properly?

Yes, there was a chalky texture when rubbed. Any thoughts / suggestions?

 

[TheDec]

Trinity,

Houses built in that era were often painted with a Limewash, this as you have mentioned allows the property to breathe. It in fact acts as a natural ventilation system within itself.

Limewash like distempers are a very unstable surface to apply any form of water or oil based masonry coatings, and sadly the cure to your problem will be both time consuming and expensive. To be honest it will all need to be removed in order for you to achieve any form of stable surface.

For the time being you could scrape off the now failing masonry paint and apply a stabiliser, and then when dry repaint those areas. Yet in time the entire paint system is prone to fail.

Dec

 

[misterhelpful]

Going by the age of your house, and the fact that you say you've been told it 'breathes naturally', I may be wrong, but it sounds as though you may have a lime mortar render.

Is this correct/possible?

If so, you should really use a limewash or EarthBorn type paint which allows the moisture held within stone walls to escape. Most standard masonry paints don't allow this, so when the moisture tries to escape it ends up flaking the paint off.

If this is not the case then you will probably need to dust off and use a stabilising solution before re-painting.

EDIT

Two similar opinions within minutes Dec - might be something in that!

 

[Trinity1832]

Thanks Dec, I think for now I opt for the simple fix. Would you recommend a stabilizer?

 

[Trinity1832]

misterhelpful,

Yes I think your right and I 'll probably need to stabilizer first before re-painting as Dec suggested.

Would applying a stabilizer seal the render and therefore restricting the breathablity of the walls?

 

[TheDec]

Trinity,

I would go for Dulux, yet all available will tend to work fine.

Dec

 

[misterhelpful]

As Dec says, it's possible that the whole masonry paint coat will fail(hopefully not!) so I don't think applying a stabiliser will cause much more of a problem if used only on the patchy areas. You shouldn't use it on any sound paint as this will lead to the new paint flaking - stabiliser should only be used for powdery and chalky surfaces.

Sandtex masonry paint claims to be breathable so it may be worth checking if their stabiliser is too.

 

[TheDec]

Mr h,

Yes there is always the possibility of a Lime render, but the fact remains that the op has applied a masonry paint to a very unstable surface.

This in due course will cause the entire paint system to fail, Lime mortar was very much used in that period yet so was cement.

With regard to a breathable stabiliser that would be unlikley as the binder would be Oleoresin.

Sorry for the very late reply, blame my dogs.

Dec

 

[Trinity1832]

Thank you all for your responses which I have found very helpful and more coinfident in addressing the issues even if they may be a short-term solution, thanks again.

 

[misterhelpful]

Mr h,

Yes there is always the possibility of a Lime render, but the fact remains that the op has applied a masonry paint to a very unstable surface.

This in due course will cause the entire paint system to fail

Which is why I said:

As Dec says, it's possible that the whole masonry paint coat will fail(hopefully not!)

Lime mortar was very much used in that period yet so was cement.

But as Trinty has been told it is naturally breathable it would suggest lime, although not a certainty.

I wouldn't expect a stabiliser to be breathable either, hence my suggestion that:

Sandtex masonry paint claims to be breathable so it may be worth checking if their stabiliser is too.