No matter what part of the world you live in you are going to find foundation problems. The following info- is just as relevant in Australia as it is in the USA for home owners, buyers and sellers.
WHAT BUYERS NEED TO KNOW ABOUT FOUNDATION PROBLEMS AND REPAIRS
Common reasons for foundation problems
The purpose of a helical pier is to transfer the load of the structure through the unsuitable soil to a stronger, more suitable soil deeper in the earth. Helical piers are a deep foundation solution. Helical pier applications operate equally well in tension and compression
Permanent new structural foundations under continuous foundation grade beams or column bases, compression and/or tension loads. Typical ultimate capacities for single piles can range from 30 tons to 100 tons . In groups, column design loads of 1,000 tons application would be for new single and multiple story buildings, including high-rise structures, bridges.
Permanent battered piles to take lateral loads including wind and seismic. Lateral loads are taken as axial compression and/or tension loads. Examples of this application would be those listed immediately above but also including sound walls, water towers, communications towers, bill boards, etc.
Permanent new structural foundations under new concrete slabs. Permanent retrofit foundations in existing structures and additions loads are being added to the structure. An example would be where a new mezzanine level is being added inside a building or where new, larger and heavier machines are being installed in a factory. Permanent retrofit structural foundations under existing concrete.
Permanent retrofit foundations for seismic upgrade purposes.
Permanent new foundations under heavy artwork/signs.. Permanent underpinning of any settled or heaved existing foundations, heavily or lightly loaded. Steel brackets are used to transfer existing loads from the structure to the new helical screw piles.
These are piers used to resist movement, vertically or horizontally. They can be of metalo wood or concrete and can be used to support directly off a solid bed or to provide resistance through frictional force. The piers appear to float in the soil.
These are piers which support the foundations of a structure. They may be fixed in place before the foundations are placed of maybe poured as an integral part of the foundations. Common practice for a new house on a cut and fill site is for 300mm diameter piers to be drilled every 1.8m along the length of the footing to a depth of soil showing the same bearing capacity as the deepest cut area of the site, so that all footing will have the same bearing capacity due to the uniformity of soil at the bottom of each pier.