Rendering has detached

[daba]

Hi, 4 year old rendering to outside brick walls has become detached in large areas, sometimes bulging out as much as 1 inch. It'll probably be dropping off in big plates by spring.

In other areas there are horizontal hairline cracks, whch I assume match up with the underlying mortar courses.

I have been told there was "too much salt" in the bricks, causing the delamination.

Obviously the walls need completely re-doing, so whats the best way to ensure proper adhesion for the new render, to ensure this doesn't happen again?

 

[memor maplin]

The horizontal lines sound like sulphate attack.

Its caused by a reaction by sulfates in a solution and a constituent of ordinary Portland Cement. It usually takes about 2-3 years to develop.