A retaining wall is not a fence (although it can serve as a footing for a fence). The law about retaining walls is principally found under the common law of nuisance and, where retaining walls were constructed after 15 January 1994, under the Development Act 1993 (SA).
Who is responsible for a retaining wall?
The most important factor in answering this question is determining the natural state of the land, as land in its natural state needs no support. It is only when the natural land is altered that support is required.
As a ‘rule of thumb’ each owner is responsible for retaining the portion of earth that they (or the previous land title holder) have altered from the natural ground level. This could be ‘fill’ placed on top of the natural ground level or excavation below the natural ground level.
Where both parties benefit from the existence of the retaining wall, then it is reasonable that both parties will contribute to the erection and/or maintenance of the retaining wall.
Where one party fills and the adjoining owner excavates, each party is liable to the proportion that the retaining wall supports the fill or excavation. For example, if one neighbour fills 300mm above the natural ground and the adjoining neighbour excavates 700 mm below the natural ground, then the neighbour excavating is liable for 70% of the cost and the neighbour that fills is responsible for 30% of the 1 metre retaining wall.
Any party can alter the natural state of their land (subject to development controls), but with this ability comes the obligation to support the adjoining natural land.
Classification of retaining walls under the Development Act 1993 (SA)
- A ‘retaining wall’ falls within the definition of ‘structure’
- A ‘structure’ falls within the definition of ‘building’
- A ‘building’ (construction, demolition or removal, including incidental excavation or filling, unless excluded by Regulations [Development Regulations 2008 (SA) Schedule 3 section 4 (1) (i)] falls within the definition ‘building work’)
- ‘building work’ falls within the definition of ‘development’ ( Development Act 1993 (SA), s4)
Under s.32 of the Development Act 1993 no development may be undertaken unless it is approved.
When is development approval required?
Development approval is required under s.32 of the Development Act 1993 (SA) when:
- fill of greater than 200mm high is to be retained and is within 600 mm of the boundary [Development Regulation 75 (2) (c)]; or
- a retaining wall of greater than 1 metre is proposed (Development Regulations 2008 Schedule 3); or
- the proposed excavation or fill [‘prescribed work’ - S60 (1) Development Act 1993 (SA)] may affect the stability of the land.
A retaining wall of less than 1 metre may affect the stability of the neighbours land dependent upon the distance the retaining wall is away from the boundary line [Development Regulations 2008 schedule 15]. For example, if the retaining wall is 200mm from the boundary a retaining wall over 700mm in height will fall within the definition of ‘prescribed work’ under s.60(1) and require approval.
Obligations for the building owner if retaining wall is a development
Once it is determined that the excavation or fill (‘prescribed work’) may affect the stability of the neighbours land the building owner must under s.60(1):
- serve notice of intention to perform the building work and the nature of that work on the owner of the adjoining land; and
- provide this notice at least 28 days prior to the commencement of building work; and
- take precautions as prescribed to protect the adjoining land; and
- at the request of the adjoining owner, carry out such other building work as is authorised by the regulations [Development Regulation 75(3)]; and
- comply with any condition imposed by the approving authority.
A proposer who fails to serve a notice or who fails to carry out work specified after a notice faces a fine of up to $10 000 [s.60(2)].
Building work the adjoining owner can request [Development Regulation 75(3)] includes:
- requiring the owner to shore up any excavation work; or
- underpin, stabilise or otherwise strengthen the foundations of any building as specified by a professional engineer engage by the adjoining owner.
- Payment of the reasonable costs of the professional engineer to provide a report and plans and specifications.
Determining who bears the cost
To determine who bears the cost, following will need to be considered:
- what the natural level of the land was; and
- if there has been any alteration to this level due to fill or excavation by any party; and
- whether one or both parties has benefited from the retaining wall.
Erection of a retaining wall
Where only one party benefits
A building owner that excavates or fills their property for their sole benefit has the following obligations:
- Under the Development Act 1993 (SA) - to obtain approval to perform ‘building work’ that affects the stability of adjoining land; and
- Under common law - to support the natural state of land; and
- To pay for all costs associated with the retaining wall.
Where both parties benefit
Where both parties benefit from the erection of a retaining wall, then it is reasonable that both parties will contribute to the erection or maintenance of the retaining wall. If the parties cannot agree on their contribution to costs then the following guide can be of assistance.
Where one party fills and the adjoining owner excavates, each party is liable to the proportion that the retaining wall supports the fill or excavation. E.g. if one neighbour fills 300mm above the natural ground and the adjoining neighbour excavates 700 mm below the natural ground, then the neighbour excavating is liable for 70% of the cost and the neighbour that fills is responsible for 30% of the 1 metre retaining wall.
If agreement can’t be reached between the neighbours, then, application can be made to the court for determination of each neighbours costs [s. 60(3) Development Act 1993 and Development Regulations 75(3)].
 |
Examples of cost apportionment
a) The retaining wall between A and B
- A is responsible 25% of the cost and B is responsible for 75%
b) The retaining wall between B and C
- The cost is shared equally between them as they equally benefit from the height of the retaining wall.
There is an existing retaining wall my neighbour has erected, but I want to level (‘fill’) on my property (other side of existing neighbours retaining wall).
The neighbour (A) who proposes to fill (after obtaining development approval, if required) is responsible for the retaining wall to hold the fill and also has an obligation to ensure the existing retaining wall is not overloaded. This may require piers to be sunk below the level of the existing retaining wall to maintain its integrity.
 |
There is an existing retaining wall my neighbour has erected, but I want to level (‘excavate’) on my property (other side of existing neighbours retaining wall).
The owner (B) seeking to excavate will be responsible for the cost of the retaining wall to support the excavation they caused and also any costs to ensure that the previous retaining wall erected by the adjoining owner (A) is adequately supported.
The existing fill retaining wall should have been built to allow for some excavation on the adjoining property. Given that after 1994 development approval was required fill if within 600mm of the boundary and greater than 200 mm high [Development Regulation 75(2)(c)], it may be that A may be required to contribute to the costs if an application was made to the court [s.60(3) Development Act 1993 (SA)] .
Encroachment – My neighbour’s retaining wall is on my property or my wall retaining wall is on my neighbour’s property
The Encroachment Act 1944 (SA) addresses matters of this type. The Act provides for the adjustment of boundaries where buildings or walls encroach on adjoining land. Under the Act a ‘building’ includes a ‘wall’ (s. 2), but not a fence [see Encroaching buildings].
An application will need to be made to the court seeking orders rectifying this situation.
Repair to existing retaining wall
Given that a wall structure is classified as a building and the term ‘construct’ in relation to a building includes repairs and/or alterations (s. 4 Development Act 1993), consideration must be given to whether development approval is needed prior to any work being commenced.
Retaining wall is on one party’s property
A retaining wall erected to support excavation or fill is the responsibility of the party that performed that work. This obligation binds all future owners (successors in title) of the property.
Under the common law tort of nuisance, the party which has altered the natural land (due to excavation or fill) will be liable to the adjoining neighbour if the neighbour’s property interest in the enjoyment of land is substantially and unreasonably interfered with or if they disturb someone else’s ordinary and reasonable use of the land they own or occupy.
Retaining wall is on the boundary
If the erection of the retaining wall is due to solely to one neighbour affecting the natural state of the land, then the party affecting the natural state of the land is responsible for repairs and maintenance.
Where both parties obtain benefit from the retaining wall, then each party is required to contribute.
If the erection of the retaining wall is due to the excavation by one party and fill by the adjoining owner, then costs for maintenance are apportioned between the parties to the degree each party altered the natural state of the land.
Retaining wall is built on the adjoining property for the benefit of the neighbouring property
Assuming that retaining wall was built on the wrong side of the boundary, the party receiving the benefit of the support will be liable as they are the sole beneficiary of the support.
Retaining wall is needed but not present
Under common law, the party that has interfered with the natural level of the land (i.e. has withdrawn support) is obligated to remedy the situation.
Subsequent owners (successors in title) assume the responsibility, where a previous owner has built up or removed soil and are also responsible for the repair or replacement of the retaining wall on their property even if they themselves did not erect or alter the retaining wall. Furthermore, the party that is suffering the interference has an obligation to mitigate the damage or else their claim may fail.
In Pantalonev Alaouie (1989) 18 NSWLR 119 Giles J considered the law of nuisance and found “…withdrawal of support from land is an actionable nuisance for which strict liability attaches without proof of negligence.”
Urgent work is required to a retaining wall
The Development Act allows for emergency orders to be made if in the opinion of the authorised officer there is a threat to safety arising out of an excavation [s.69(1)(a) Development Act 1993 (SA)]. This order may require the building owner:
- to evacuate the land or building;
- not to conduct or not to allow the conduct of a specified activity or immediately terminate a specified activity;
- to carry out building work or other work; and
- to prohibit the occupation of a building or land or the use of a building or land.
If the order is not complied with, the council can have the work performed and the cost is recoverable from the owner [Development Regulation (2008) SA 75 (4) & (5)].
An owner can appeal the order within 14 days after the order is received by them or longer if granted an extension by the court [Development Regulation 2008 (SA) 75(10)]. Owners will need to make a separate application if they seek to have the obligations of the order stayed.
In Payne v City of West Torrens [2004] SAERDC 110 an authorised officer identified an unsafe boundary wall and issued an emergency order under section 69 of the Development Act to have the wall demolished. Mr Payne appealed the order and a variation was made to enable the walls to be stabilized and not demolished.
Where the retaining wall was built by the prior owner of the property
In the case of Thynne v Petrie (1975) Qd.R 260, it was determined that an owner who has failed to take reasonable precautions that has resulted in the subsequent soil collapse causing interference, may be responsible, even though they have sold the property.
Subsequent owners (successors in title) assume the responsibility that a previous owner has built up or removed and are also responsible for the repair or replacement of retaining walls on their property even if they themselves did not erect or alter the retaining wall.
It is important to note in this above case, the applicant (Thynne) lost their claim because they were bound to do what was reasonable to mitigate their loss. The applicant initiated the application some 7 years after they first noticed erosion occurring as a result of excavation work previously performed, but they failed to take action to mitigate the damage.
 Prev |
 Up |
 Next
|
| BOUNDARY LOCATION | ENCROACHING BUILDINGS |
Browse Law Handbook
|
Acts and Legislation
|
Search the handbook
|
Glossary
|
Print this page
|
Print whole section
|
