A retaining wall is required to be provided when a lot owner changes the level of the ground on or near the boundary and that level change affects the adjoining lot. The person who changes the level is required to provide a retaining wall of a size and construction within their lot that is suitable for the intended purpose. For example should there be a building adjacent, then the erection of the retaining wall should not compromise the stability of that building before, during or after the works are finished.
A practicing structural engineer may be required to certify the type and design of the retaining wall and its particular location.
Information pertaining to constructing retaining walls:
Retaining walls are required to be constructed wholly within the subject lot and not trespass the boundary (even for thickenings or footings) as issues relating to maintenance and ownership may result.
Consideration of the design and type of retaining wall to be constructed adjacent to boundaries may depend on the type of dividing fencing proposed – mass limestone (or similar retaining walls) may not have sufficient space to allow a Hardifence (or similar) to be placed in the ground behind the retaining wall. Colorbond type fences may require posts to be drilled into the stones of the retaining wall, the retaining wall needs to be constructed to allow for this and the effect the wind loading on the dividing fence may have.
All retaining walls greater in height than 450mm requires the issue of a Building Permit prior to works commencing.
Vegetation may have a detrimental effect on retaining walls. Palms and large trees may, over time, grow and push against retaining walls. Select vegetation/plantings that are appropriate for the situation.