The main reason that lime render fails is that it is painted with unbreathable paint. This causes lime render to fail because it traps the moisture and cannot allow it to get out. The lime render has to be painted with lime wash – a breathable paint.
When moisture is trapped between the render and the wall, it can cause cracking and bulging. It won’t necessarily cause a large crack but a hairline crack which, if left untreated, can cause a bigger problem and more damage. Moisture that has penetrated the render and got trapped could cause the render to start breaking away from the wall and would leave the brick walls exposed to the elements.
By using lime wash, you are not only allowing the lime render to breathe but you are also adding extra protecting to the wall and giving it a decorative finish.