Types of cracks
B.
Cracks originating from the plaster base
B.1
Cracks in way of vertical and horizontal joints
B.2
Cracks due to the change of shape of different wall materials

The cracks pass through the entire plaster thickness down to the masonry joints and are discernible from the course of the crack that is almost identical with the masonry joints.

 
Causes for cracks
Causes for cracks

Insufficient drying of the masonry.

Extremely deviation properties of the masonry construction material (mixed masonry).

Masonry not solidly filled.

Extremely deviation properties of the masonry construction materials and joint mortal.

Thermal stresses origination from the wall material.

Volume changes due to temperature and humidity effects.

For instance in case of mixed masonry and light wood-wool building boards.
Source of the pictures and texts: BSF note no. 19, January 1997
Cracks in exterior plasters, coatings and reinforcements, editor:
Bundesausschuss Farbe und Sachwertschutz e.V., Hahnstraße 70, D-60528 Frankfurt am Main