The " Subsidence " Issue !

There are many areas surrounding Sydney where new homes are being built on land that is immediately above tunnels where coal has been extracted.  In many cases, these are tunnels that may have been abandoned a century ago and building now is only permitted under very restrictive conditions.

The problem is natural subsidence.  The land surface is prone to shrink as those tunnel supports age and consequently the specification for homes above insist that they sit on a reinforced concrete slab and are constructed of lightweight material which will not contribute weight pressure on the cavity below.   Owners who experience damage are reimbursed from a bond required of developers when these building sites are approved.

The city of Sydney is experiencing  an unprecedented  construction phase to deliver a modern road system and to install a public transport system involving both extension of the present urban rail system and new transit lines, and much of this involves creating new underground tunnels.  Giant boring machines are creating these tunnels through the sandstone rock on which Sydney sits.

As they are finished, these tunnel walls are encased in reinforced concrete and it is not envisaged that there will be the subsidence problem associated with abandoned coal mines, but during the construction process vibration and the use of heavy machinery is affecting the inner and outer walls of the existing homes situated above.  The issue worrying owners concerns who pays to fix the problems this is causing ?

There is a particular concern in the suburbs of Strathfield, Concord and Homebush which have a great many Federation style homes constructed of brick and with inner walls that are often lath and plaster construction.  Such construction methods react badly to even slight movement and when owners contact the builders they are told that the cause is an unusually dry winter or a host of other causes. There is a reluctance to accept blame.  The matter is being shifted to when work is completed and a proposed " dilapidation " report will be carried out to determine the extent of damage.

This is a further worry to owners. The onus of blame will depend on the report of engineers engaged by the construction firms and will use their own data to refuse claims.  Where claims are proven, the degree of compensation will go to arbitration.

The NSW government has set up an independent assessment panel to review condition reports and  resolve property damage disputes but the final outcome is far from certain.  It seems likely the sheer age and the type of building materials used in an earlier time may be deemed to contribute to some degree and the rectification cost awarded proportionately.

It seems likely that many claims for rectification may end up being decided in a courtroom.