Project Description

It is common that a new house or addition will be over or adjacent to a sewer.  The Sydney Water rules around this are always changing.  But typically when building over the sewer, concrete encasement is required as is piering below the “zone of influence”.

If building adjacent to the sewer, within the zone of influence, piering below the zone of influence will be required.  The zone of influence in clay soils is 1:1, therefore, if the sewer is 2 meters deep and you are building within 2 meters of the sewer, building over sewer details will be required.  In sandy areas such as Bondi and Ramsgate for example, the zone of influence becomes 1:2, therefore if the sewer is 2 meters deep and you are building within 4 meters of the sewer, building over sewer details will be required.

The requirement for this is flagged during the DA process.  We can provide the details for a cost in addition to that of designing the slab, upper level framing etc of around $350 + GST.  Contact Gilcon for a quote.

Building Over Sewers - Gilcon Structural Engineer