Constant erosion and high moisture causes problems.
Conventional repair methods can cause further problems.
Brickwork can be treated, but cavities cannot be successfully filled. Repointing is often necessary.
Textured renderings can be repaired but blemishes remain.
Other renderings need extensive patching, also leaving blemishes.
All surfaces can be repaired - but although sound - ugly scars and blemishes remain which have to be covered cosmetically. Conventional painting is unsuccessful as blemishes will still show through - and once you start painting you are committed to repainting every 3-4 years!