How to fix plaster cracks and Causes.

The little cracks on your wall can get so big if not quickly fixed, and it
may totally deface your building.

Plaster cracks are caused by the following reasons--

(i) Inadequate use of cement-When the mixture ratio of cement with soft
sand is not of a standard proportion, you'll see notable cracks on
building after curing /drying of the wall.
To save money foolishly,some masons use poor sand with so much impurities
and some that contains too much of clay. Fine sand with a good percentage
of cement will give a well bonded plaster surface with little or no
cracks.

(ii)Handling of the job by incompetent and impatient masons can also
results to plaster cracks. When the mortar/plaster mix is pasted on wall
you are supposed to use trowel and range(longwood) to get a vertically
blended surface ,after that a foam is applied which helps to smoothens the
surface.
The foam is wet with water and then used to gently rub the surface of
plaster. But the surface is left for a while or a time frame from when
trowel is used to initially smoothens the surface and when to finally use
foam to smoothens it.

(iii) When water is not enough in the mix, then plaster cracks will also occur.

(iv) Post usage cracks can occur if a portion of plaster surface is
continully exposed to water, that portion will eventually crack.

To fix, there are different methods you can apply.
First, scrape out the scale or the exposed surface, wash and clean the
surface with water and remove other dirts and growths like algae which
may affect the bonding strenght. Try to find out the cause of the crack
and see if the problem can be fixed. Vibrations from machines around can
cause cracks too in a building.

After that depending on how large the surface area, put wire mesh (small
tiny iron) in the surface and apply the mortar to cover the portion, the
wire mesh is to make sure the plaster does not fall off from a large
surface area with thick plastering.
Sprinkles water and carefully smoothens the surface with foam.