The most common and easiest method of NDT is visual inspection. A trained eye can easily find out any apparent visual aberrations in a structure.
Be it a crack, a stress mark, a damp spot or an unusual touch up on a surface, when carefully observed, these apparently minute indicators can sing a song to an expert, revealing the health of a building.
The best part of the visual inspection method is that even a novice can, at least, surmise that there is some aberration in the structure.
Unless a building sustains a serious damage due to a natural calamity or due to some unusual incidents, its deterioration often starts from seemingly innocuous damages and assumes monstrous proportions if these tell-tale signs are ignored.
A periodic visual inspection can reveal these defects and can help us in nipping these problems in the bud. But this type of inspection has its own draw backs.