render finish peeling off

[ij21]

I had a 2 storey extension built on my house 22 years ago. It was built with 215 mm thermalite blocks rendered externally to finish. The render was sealed with a proprietary product and then coated with masonry paint. It was repainted seven years after. Over the years the old paint has been blistering and peeling off, leaving a poor sandy and friable surface. As a scaffold will be needed it is critical that the repairs are done correctly. I tried to repair it by grinding it back and filing with a render of cement, building sand, plastering sand but it will not adhere. Can you advise me please?

Untitled

• ij21
• 11 May 2011
• 1

Untitled

• ij21
• 11 May 2011
• 1

 

[joe-90]

Try soaking it with SBR then with an SBR slurry. It's the suction that is stopping your render from going on. The wall sucks out the moisture and then it won't stick. Try putting your render on newspaper for a few minutes and you'll find it crumbles between your fingers - the dry wall is doing the same thing as the newspaper.

 

[ij21]

Thank you for your advice.

However, I need to have a definitive answer if I am going to pay a grand for scaffolding etc whether I do it my self or get a builder to do it. It needs to be right first time. I am not familiar with SBR, but from what I have read it needs to be mixed with cement and not applied neat.