painting rendering

[colmol]

Hi - am new to the site and hope I can get some advice. I need to paint part of the outside of my house which is finished in render - since moving in I have had to paint it every year because despite whatever paint I use, however much preparation I make, the same thing happens - the paint bubbles and then cracks and then flakes. I have been reading about pliolite based paint and this sounds like it might do the trick - my question is would I have to remove all of the old paint (that hasnt cracked or flaked) first? I would be really grateful for any advice. I am fed up of painting this every year!
Thanks

 

[TheDec]

Did you thin the first coat prior to application.

Dec

 

[colmol]

Thanks, I have only used water based paints previously, have always made sure the surface was clean etc (apart from the remaining paint)and followed instructions for drying times etc - but have never thinned the first coat. Would be grateful for your comments about pliolite paint - (is it any better than the water based) and if by thinning the first coat of any type of paint, this might solve my very long standing problem

cheers

 

[TheDec]

Thinning your first coat is important this allows the paint to be absorbed by the render which in turn forms a bond between paint and in your case cement render. If you apply it without first thinning the paint will tend to just sit on the surface and the render won't be able to absorb enough to provide that all important bond.

Pliolite paints are solvent borne and are extremely hard wearing, yet you should always thin the first coat before you apply it to a porus surface.

Dec

 

[Growler]

Hi - am new to the site and hope I can get some advice. I need to paint part of the outside of my house which is finished in render - since moving in I have had to paint it every year because despite whatever paint I use, however much preparation I make, the same thing happens - the paint bubbles and then cracks and then flakes. I have been reading about pliolite based paint and this sounds like it might do the trick - my question is would I have to remove all of the old paint (that hasnt cracked or flaked) first? I would be really grateful for any advice. I am fed up of painting this every year!
Thanks

When you first painted it when you moved in, what was on the render

 

[colmol]

Thanks to TheDec - Thats some great information - would I need to try to get all the old paint off before repainting with the first thinned coat? Am I right in thinking after looking at other posts on this site that with water based paints it should be thinned about 20% and about 15% for pliolite paints?

Thanks growler - this part was already painted when we moved in but was in need of re-doing - and I have been redooing it basically every year for the last 20 years! I'm hoping the info Ive got from here will help solve the problem.

Thanks

 

[TheDec]

I took it by your original post that the render was not painted and this is now not the case, you should remove all of the existing paint and start from scratch, then use a water based masonry paint such as Sandtex thinning your first coat around 10%. The existing coating whatever it was may have been unstable and the continued application of an albeit un-thinned paint would not have helped.

Dec

 

[colmol]

The Dec - Sorry I didnt make myself clear in my original question. I will take your advice and remove the existing paint and apply a thinned first coat water based paint before applying a normal second coat. Thanks very much for your advice - it's very much appreciated!

Cheers

 

[TheDec]

No worries, it would'nt hurt to add around 5% water to future coats either this will help the paint to flow and cover better.