The crack is can happen to any building irrespective of the quality of the materials used. The crack is as result of agent of denudation (rain, water, wind and waves ). Continous wetting and drying of concrete wall will one day create cracks.I agreed that building materials needed to be improved on,I could remember some one asked me this question,'please can you tell the reason every houses is with a crack or more' I told her it could be vibration of large automobile which she diagree and told me it is due to the materials used.