Sand-lime brick

What properties should a lime brick wall have–sand, if it is intended to be covered with a permanent coating?
The substrate should be firm, clear, with no scratches, seek, free of efflorescence and foreign bodies.

For which defects of a masonry facade made of sand-lime bricks, it is necessary to formulate the conditions in writing prior to the commencement of facade works?
If there are any reservations about the condition of the substrate or the method of execution, it should be in writing. These comments may relate to increased substrate moisture, large surface efflorescence, chipping of the brick surface, larger scratches in the joints and cracks of dynamic origin.
In case of heavy soiling, the occurrence of eruptions, moss, lichen and fungus, it is necessary to perform a wide range of preparatory works. The related additional costs should be specified and agreed in a supplementary contract prior to the commencement of work.

When renovating external walls made of sand-lime brick, defects in the mortar in the joints and / or deformation of the joints due to damage to the cladding are a common disadvantage.. What disadvantages should be given special attention here?
The mortar in the joints should not have scratches, neither do I have any efflorescence. Of course, the mortar should be dry. In the joints, it should tightly adhere to the bricks' edges.