Underpinning in Thirroul
A heritage conservation area named the Illawarra Escarpment Landscape Area is mapped as intersecting Thirroul, and a University of Wollongong inventory records a landslide site here with repeated movement since 1950. Neither says anything about your footings, and both are reasons to ask before a dig.
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Underpinning around Thirroul
The state's soil-landscape map returned the Illawarra Escarpment unit at three of our five sample points in Thirroul and the Gwynneville unit at two. The report for the Illawarra Escarpment unit names Thirroul's urban fringe on its foot slopes, lists mass movement and rock fall hazard and reactive, low wet bearing strength subsoils among its limitations, and adds that special foundation designs may be required in areas of mass movement hazard.
The University of Wollongong's landslide research pages describe a documented site in Thirroul, number 113, with sixteen recurrences after a first recorded movement in March and April 1950, and say Illawarra landslides have damaged houses by moving slowly and intermittently. It is one recorded site on undated pages, not a finding about the suburb. We found no source that says landslip movement damages, undermines or calls for the underpinning of house footings.
Permits and Wollongong City Council rules
Wollongong's Development Control Plan Chapter E12, dated 19 July 2021, applies to land the council records as known or suspected to be subject to land instability. For development on it the council requires a geotechnical impact assessment report from a chartered geotechnical engineer or engineering geologist, unless it is satisfied the risk is acceptable, and a report over two years old needs re-certifying on form M11. The chapter does not list the land the council has recorded, and it does not say whether underpinning needs consent, so ask the council or a certifier. Separately, the local plan lists the Illawarra Escarpment Landscape Area as a heritage conservation area, and the state's planning layer shows it intersecting Thirroul. Clause 5.10 requires consent to alter a building's exterior there unless the council has advised in writing that the work is minor or maintenance, and the state's exempt entry for repairing foundations does not apply.
Source: Wollongong DCP 2009 Chapter E12 (footer dated 19 July 2021); Wollongong Local Environmental Plan 2009 cl 5.10 and Schedule 5 Part 2 (version published 28 August 2026); NSW Planning Portal heritage layer; Codes SEPP cl 2.53; University of Wollongong Landslide Research, Scope (undated page); NSW soil-landscape report, Illawarra Escarpment unit; read 24 September 2026. — confirm current requirements with Wollongong City Council.
Our Thirroul service area
An enquiry from Thirroul is passed on to an independent provider, who gets in touch to look at the house.
See all Underpinning in Wollongong. We also work in Woonona, Bulli and Austinmer.
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