Blown Rendered wall + paint flaking

I have a rendered blockwork retaining wall in the garden which I build about 6 months ago. I painted it using some expensive 'self-cleaning' paint in the hope it would stay clean.
Needless to say the paint has been so effective it has all flaked off and also some of the rendering has blown as well. The wall is in a sheltered area of the garden and doesn't get a lot of sunlight so it does remain fairly damp especially as it retains a load of earth.


I need to repair the rendering and paint the wall again. Should I use a membrane behind the wall to stop it getting damp?
Also should I use an additive in the rendering and what type of paint shall I use? I don't want to use the self cleaning paint again if it will all flake off.

its the damp coming from behind, as most paints (even exterior ones) are solvent based and create a seal, not allowing moisture thru' so will continue to blow render off. render is of course concrete which is also none breathable. Try and find some lime render, pre-coloured and breathable.