Boundary Retaining Walls - Issues & Responsibilities

Whether building new or dealing with an existing boundary retaining wall there are important issues that need to be understood which we attempt to clarify here.

boundary retaining wall responsibilities — unfortunately too many people use old fences as a guide to the boundary location

In this article we’ll attempt to provide some clarity around such questions as the need to gain various approvals when building a retaining wall, where exactly can a retaining wall be built in proximity to the boundary and the question of responsibility. We’ll also discuss existing boundary retaining walls.

Important issues to understand first

Before we delve into this in detail, we must point out some important issues that need to be understood first.

This article is specifically about retaining walls on or near the property boundary – not building other items such as carports decks or extensions near to the boundary, some of which we explore in other articles.
It is useful to know exactly what constitutes a retaining wall. A retaining wall is a structure erected to support soil in an excavated, cut or filled embankment. It is classified as a ‘class 10b’ (non-habitable) structure and as such it needs to comply with certain building and design requirements including drainage and engineering design which vary dependent on the individual circumstances. ‘Australian Standard, AS4678 – Earth Retaining Structures’ deals specifically with retaining walls that are between 800mm and 15M in height.
Retaining walls are frequently confused with ‘dividing fences’, something they are not. This means that disputes relating to retaining walls do not come under the legislation that deals with dividing fences [Neighbourhood Disputes (Dividing Fences and Trees) Act 2011 (Qld)].
There is no specific Act that deals with neighbourhood disputes relating to retaining walls. What this means, and therefore leads to, is that disputes are settled either in Court or by private negotiation outside Court. They can be long, protracted, stressful and expensive, so the lesson is to take all reasonable precautions and discussions early, before building, if possible, with neighbours.
Lastly, it must be understood that it is not the Surveyor’s professional remit to decide or judge or give advice on such things as the law forbids that – we simply provide accurate detailed information in the form of a boundary ID survey that is critical for use in deciding the wide and varied issues, many controversial, that arise in this area.

boundary retaining wall - who is responsible — Notice that the wall is inside the boundary but the fence is on the boundary

Council Approvals

Remember here that we are not simply discussing retaining walls as such but retaining walls on or near to the boundary. Therefore, it makes sense to know exactly where that boundary is. You cannot rely on fences.

Generally, retaining walls that are up to 1 metre in height above natural ground level do not require engineering design or Council / Building approval, however this may vary dependent on which Council area you are in as well as the zone of the property and whether or not it is on a property boundary or near to it, remembering that it’s a class 10b structure under the building code.

Other issues which can influence this requirement are proximity to other structures on your or your neighbour’s property such as house foundations, sheds, or swimming pools. In some instances, it may be necessary, a Council requirement, to obtain written consent of neighbouring landowners.

So, to the question of ‘do I need approval’? best you speak with a Council building department officer or building certifier. There are two other important people to speak with if you are contemplating building a retaining wall on the boundary. They are your neighbour and a licenced Surveyor.

Can I Build on the Boundary?

Best practice for constructing a new boundary retaining wall is that it be wholly built, inclusive of footings, within the uphill property whose ground is being retained and that it is structurally designed to withstand the pressures generated against it and further accommodates drainage to capture groundwater seepage enabling that water to escape to a legal point of discharge and not into the downhill neighbour’s property. Such a wall should be treated with an impervious coating prior to being backfilled and drainage channels be located below natural ground level.

boundary retaining walls - who is responsible

It is generally considered that it is the uphill property that gains the actual benefit of the retaining wall. This consideration can become muddy, or less clear when it is the downhill property that excavates an existing embankment, as in the picture below, to facilitate improvement, access, or enjoyment of use of that downhill property.

This is where full and frank discussion between neighbours is advised resulting in a fair agreement detailing all responsibilities, all of which should be documented. A boundary identification survey clearly identifying the common boundary line dividing the neighbouring properties, should be considered an essential requirement of such discussions and documentation.

And, always remember, you cannot rely on fences to be on the boundary!

Responsibility

So far, we’ve been talking largely about building a retaining wall. Most of our work involving boundary retaining walls involves existing walls. Sadly, many of those walls are old, poorly constructed, and poorly located in relation to the boundary. Frequently they are involved in a dispute between neighbours and on many occasions those neighbours did not own the properties when the wall was built.

Failing Walls

The disputes are varied and can range from the wall failing to its location, to drainage, to repair etc. There is rarely a clear understanding of where the responsibility lies and it’s not uncommon where a proportion of responsibility can fall on both parties.

We have a series of diagrams that may assist in determining likely responsibility and may be useful in discussions between neighbours in assisting them to ascertain answers to such questions as

In which owner’s property is the retaining wall located?
Is it located squarely along the common boundary line?
Is it located substantially in one property and partially in the other?
Is one neighbour causing damage to the retaining wall due to issues emanating from their land such as tree branches, underground tree roots, stormwater overflow, drainage, and other issues?
For what purpose or for whose benefit was the retaining wall constructed?
Do the neighbours receive an equal benefit from the retaining wall?

Love Thy Neighbours

Central to any sensible discussions unfortunately is the need to invest in a Boundary Identification Survey.

Remember, there is no specific Act of law relating to retaining walls. What law that exists is not simple and will involve cases that have already been decided previously in past legal Court actions. We strongly recommend conducting amicable constructive discussions with your neighbour to try and come to some agreement over the issues because having others make the decisions for you in Court will likely be very expensive and stressful.

Ultimately, if you do end up in Court, each case will be determined by its facts considering the sorts of questions we raise here, as to which neighbour has responsibility to maintain, repair or replace the retaining wall and to what extent as they may decide to apportion the responsibility. This might have been something that could have been done between yourselves earlier saving expensive legal fees and Court costs.

Remember, Surveyors must not provide property owners with legal advice or commentary on the rights of affected property owners. The law forbids that. It is up to the property owners [with the help of a lawyer if need be] to consider factors such as who built the retaining wall, who benefits from the retaining wall and who is responsible for the repair of a retaining wall.

If you need survey advice regarding boundary retaining wall please don't hesitate to call us or ask for a quote