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 that is suitable for the intended purpose. That is, should there be a building adjacent, then the erection of the retaining wall should not compromise the stability of that building during or after the works are finished.
A practising structural engineer may be required to certify the type and design of the retaining wall and its particular location.
Retaining walls are generally 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, however, the Building Act 2011 allows some encroachments in some circumstances.
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 of the wind loading on the dividing fence may have.
All retaining walls greater in height than 500mm require the issue of a building permit prior to works commencing.
Retaining walls less than 500mm high also require a permit where they encroach beyond the boundary of the works land, adversely affect the adjoining lots by reducing the bearing capacity of the land, damage or reduce the structural adequacy of a building or structure on the land, or change the natural site drainage in a way that reduces the effectiveness of the drainage of the land or existing or future buildings on the land. Where either an encroachment is to occur or a retaining wall will adversely affect the adjoining lot, permission from all of the adjoining land owners is required prior to applying for a building permit.
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 carefully and appropriately for the situation.
Existing subdivision retaining walls
These retaining walls are constructed, generally speaking, wholly within the confines of the "high side lot". They become the responsibility of the owner of that lot to maintain. Adding courses or fill greater than its design limit may cause the retaining wall to fail. Do not raise the level of the retaining wall unless with the specific approval from our Building Services.
The lot owner on the low side is to note that the removal of any soil (foundation material) from the toe of the retaining wall may render the retaining wall unsafe. Do not remove soil from the base of the retaining wall unless with the specific approval from our Building Services or from an appropriately qualified engineer.
Dividing fences/issues with neighbours
A dividing fence is defined as a fence situated on or about the boundary separating two lots. We define a “sufficient fence” for the purposes of the Dividing Fences Act 1961 (WA) by detailing the following:
- fencing materials
- heights of fences.
In residential, commercial and rural lots, however, we have no jurisdiction on the Dividing Fences Act 1961 (WA).
The State Government Department of Commerce provides advice on:
The Building Act 2011 has introduced new procedures that must be followed by a person responsible for work prior to the removal of a fence, gate or other barrier to land on or beyond the boundaries of work land. Generally speaking, the person responsible for the work must ensure that no fence, gate or other barrier to land on or beyond the boundaries of the works land is removed unless each owner of the land that shares, or on which it is located, consents to the removal; or the removal is in accordance with a court order; or the removal is required as a matter of urgency to prevent the imminent collapse of, or damage to, any land including a building or structure on the land.
For further and more specific requirements, please refer to the Building Commission website, email the Building Commission on BCinfo@dmirs.wa.gov.au or call them toll free on 1300 489 099.
A "Rights and Responsibilities" pamphlet outlining dividing fence issues is available at our Administration Centre, Civic Boulevard, Rockingham or it can be downloaded from the Building Commission website.
Disputes related to dividing fences should be referred to the Building Commission.