Waterproofing coat before painting?

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Left hand flank wall.jpg


Hi everybody. I am currently collecting quotes for painting the outside of my dormer bungalow. The house was last painted a long time ago and some of the old paint is flaking off the two gable ends, which bear the brunt of the weather (see photo for the worst wall). I am fairly sure that the render itself is sound but they are solid walls and damp is getting onto one or two of the inside walls. I am thinking 1) scrape off flaky paint, 2) apply waterproof coating and 3) apply top coats of paint (Sandtex or similar). Does that sound reasonable? Any advice gratefully received. Thank you.
 
You don't want to seal walls with anything. The paint needs to let moisture through. I have limited knowledge but plenty of information online and paints available. It's worth speaking to the technical department as well
 
Looking at what appears to be a lot of cracking of the render I wouldn't waste money having it painted. Have the old render knocked off and redone.
 
Thanks guys. My information is that the render is fairly sound and it's just the fact that the house hasn't been painted for so long that is causing the flaking and water ingress. I've read a lot about paint made by Emperor, who say their products last for 25 years. Sounds too good to be true to me but it apparently keeps water out and still allows the walls to breathe. No idea how that would work.

There are so many people recommending Sandtex Trade that I'm tempted to just go with that and forget about an intermediate waterproof coating. It's difficult to know how much of the information online is just company blurb. I'm hoping to get a more balanced opinion on this forum by people who have been actually doing the job and aren't affiliated to any particular product or company - recommendations from the horse's mouth, so to speak.
 
The render is the waterproof layer, and if it's not performing as such then it's failed and should be renewed.

Generally, paint won't adhere to common masonry water repellent systems such as silicones, silane and siloxanes, and even if it did, it will likely compromise the very hydrophobicity and porosity that make it water repellant in the first place.
 
Okay then, looks like new render followed by top coat. Help much appreciated everybody.

Well there goes my holiday in the sun... sigh...
 
True enough. And just think of the many happy hours I'll spend staring at the new render, compared to a paltry week of sun, sangria and something else beginning with the same letter that I'm not allowed to say here...
 

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