Interior water damage have mainly three sources:
1. Interior plumbing
2. Excessive humidity levels
3. Rain water infiltration
Plumbing is one of the major source of interior water damage.
1. Hot and cold water supply pipes are usually buried in the slab. If it is starting to leak you would not realize it immediately. It will spread in the slab and when it gets to a wall you will eventually see the visible water damage. One simple way to check if there is a leak on the supply is to check to watermeter overnight. If it moves overnight without any water being used, you know there is a problem.
2. Bathroom and kitchen drains can also be the source of water damage
3. Waterproofing of the showers and baths. The silicone around the bath and at the base of showers has to be perfect to avoid water infiltration
Supply pipes are usually buried in the ground underneath the tiles. If it is leaking, the water will spread underneath the slab until it meets a wall and visible water damage will appear.