Typical signs of structural instability include:
Another indicator is the age of your house. If your house was built before 1970 then there is a good chance it will be due for reblocking or underpinning soon. Don't wait too long to reblock your house as it can be dangerous to leave your house's foundations in poor condition.
Reblocking and restumping are terms that describe replacing the old 'block' or 'stump' foundations of a home with new concrete stumps. Reblocking and restumping is applied mostly to older weatherboard homes which are slight raised off the ground with their foundations. The terms can be used interchangeably.
Underpinning is the process fixing a properties foundations and returning the home to it's original level if that property's foundations are a concrete slab. This mostly applies to brick veneer homes. Typically a concrete slab will, over time crack and sink into the earth at one spot or another. We prop up the slab (or underpin the slab) with a number of 20 tonne jacks where it has sunk and fill the space with concrete to return the slab to it's original flat level.