This question refers to a retaining wall/fence in an

Both owners will be responsible for the fencing work.

In South Australia, the owners of adjoining land not divided by an adequate fence may be liable to contribute to the construction, replacement or maintenance of a such a fence: Fences Act 1975 (SA). An owner of land who proposes to erect, replace or repair a fence dividing that land from the land of an adjoining owner may serve a notice of that intention on the adjoining owner specifying a proposal for how the work is to be carried out and seeking contribution to the cost: s 5 of the Fences Act 1975 (SA). If the adjoining owner objects to the proposal, he or she may serve a cross-notice setting out counter-proposals: s 6 of the Fences Act 1975 (SA). If a dispute arises, either party can seek an order from a Magistrate prescribing the kind of fence to be constructed and the proportions in which the parties are to contribute to its construction: s 12 of the Fences Act 1975 (SA)

The forms of “Notice of Intention to erect a fence” (Form 1), “Notice of intention to perform replacement, repair or maintenance work” (Form 2) and “Cross-notice” (Form 3) are set out in the Schedule to the Fences Act 1975 (SA).

A person carrying out authorised fencing work may enter upon land at any reasonable time and do anything that may be reasonably required for the purposes of the fencing work: s 18 of the Fences Act 1975 (SA).

You have a legal right to protect your interests in this situation.

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