Cracks don’t always mean poor workmanship nor do they always indicate structural defects. As concrete settles and moisture evaporates, shrinkage cracks may occur. This happens when there is excess water in the concrete mix, the coarse aggregates are small and do not provide internal restraint to shrinkage, or the concrete dries too rapidly (less than 7 days) before it gains enough tensile strength as a solid to resist minor cracks.
To minimize shrinkage cracks – as cracks of this type inevitably occur – there should only be just enough water in the concrete mix, coarse aggregates should be bigger sized, and concrete should be water-cured according to standard time frames.
But cracks happen. When they do, you need not be alarmed, as long as you attend to them early.
Shrinkage cracks, which can be as narrow as 1/16 of an inch, are something you can remedy on your own. Even though the public perception is heavily weighed against shrinkage cracks, they are in fact acceptable as long as they do not leak water and do not widen to more than ¼ of an inch. In this case, you can use crack injection resins to fill the void and touch up the concrete for aesthetic purposes and, more importantly, to prevent serious cracks from happening.
When bigger cracks do occur, they are still preventable as long as you take prompt action. Even with vertical cracks of more than 3mm, which many may consider requiring professional attention, you can still fix them as long as there is no significant inward shifting that occurred. There are plenty of injection resins you can use that are easy to apply on your own before the cracks become much more noticeable (where you can insert a No. 2 pencil through) and pose threats to building occupants.
Getting the entire wall repaired can be very costly, so attending to cracks no matter how small they may seem at first is crucial. You can never tell if they will remain harmless or widen over time, creating cracks that go through the center or corner of the wall, or cracks that will shift the foundation inwards and pose hazard. In life as in making building repairs, an ounce of prevention is always better than a pound of cure.