I recently bought a house, in Aussie, and have found a crack from front to back of the house ( only found when pulling carpets up to put down wooden flooring ). It appears to be hairline crack less then 1/16 inch wide, but again the length worries me ( or should it ). There are signs of damage to walls or anything else in the house, probably why the building inspector didn't find it. Should I be concerned ? I have scoured the internet and it seems some cracks in house slabs are NORMAL. The house is 10 years old.