Boundary Retaining walls - Who's Responsible?

Why there's a problem - some history:

Over the last forty years many retaining walls have been built with timber or constructed without engineering design or with insufficient strength. Today we are experiencing lots of calls from owners with retaining wall repairs and replacement problems.

Who should foot the bill?
We understand that these projects can often be an expensive and complicated construction. Usually, the person who first recognises the problem is the lower neighbour – who looks on to the wall. The neighbour on the higher ground may be unaware of any problem unless notified by their neighbour or perhaps they see a fence start to lean over.

There may be some discussion between neighbours about the condition of the wall and the costs of repair.
At this time people start questioning ownership of the wall - and responsibility for repair and costs. One of the neighbours will call us (usually the lower property) and request a survey to find out where the boundary lies and ownership of the wall. 

Some important and realistic points to consider:

The wall should be built wholly on the owner’s land. This is not always the case however and we often see instances of people who get the full benefit of a wall built on their neighbours’ property.

A retaining wall is built for a purpose. Generally, it's the property owner who gets a benefit from the wall’s existence who is responsible for the wall.

Unfortunately it's not always that clear cut or simple.

Quite often there is a benefit to both parties. If the land was originally sloping and both blocks now have flat land, we can assume that there has been some cut and fill.

It then becomes an exercise in determining how much the lower property has been cut. Often however, developers and builders will cut and bench the whole estate to provide flat building pads to facilitate slab on ground construction.
The best (and sometimes only) way to determine cut and fill is to dig or drill a hole in the top section to determine the depth of fill behind the wall. If its all fill to the base of the wall there is no benefit to the bottom neighbour. It becomes clear who is responsible.

Do both neighbours get benefit and share costs?
Sometimes a landowner gets no benefit, did not build the wall, and is asked to pay for the repairs simply because a previous owner or builder managed to build the wall on their property.

The way forward:

There is an information gathering stage for any building project. Assess the issues and repairs, determine who gets benefit and if necessary, determine the boundary location. Discuss the result and try to come to a reasonable plan of action. This will usually involve Survey.

Types of Surveys:

Partial Site Plan
A plan showing the retaining wall levels and surrounding structures relative to the boundary. We show an area to demonstrate any difficulties with access to repairing the wall. Sometimes there is no room for machines and all work is done by hand. This plan is best for general information for discussions and construction. It does not include marks on the ground.

Identification Survey (Partial property)
This is a formal survey that marks the boundary line. These marks may be pegs in the ground or any other type of mark that is placed on a structure. The plan shows any encroachments or structures close to the boundary. The plan is lodged with the Queensland Government as a public record and if there are issues with the boundary, a formal notice is sent to all
property owners.
This plan is best to show all parties and builders where the boundary lies on the ground and is good for discussion and when construction is on one property only. 

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