Just because they are outside and appear incidental, home buyers should not overlook the condition of retaining walls on any property they are considering buying. Apart from the physical condition of retaining walls, what makes them so crucial to property owners is that they are often on or close to a property boundary and can become a costly legal battleground between neighbours.
A collapsed boundary retaining wall can have a major impact on the value of a home and can cost tens of thousands of dollars to fix, with many retaining walls having been constructed on steep slopes as part of the establishment of a level housing site.
Archicentre Australia architects conducting assessments for home buyers – or providing advice to home owners who have observed their retaining walls cracking – sometimes find construction shortcomings and no relevant paperwork or approval evident in relation to the design of the retaining wall. Paperwork can become vital to protect home owners in the case of a retaining wall failing, both in terms of having it fixed and also against legal action by a neighbour who may have had their home damaged or devalued by the failure of the retaining wall.
The integrity of a retaining wall can be compromised by a variety of factors that include:
- The location of large trees close to the retaining wall.
- Poor drainage allowing the structure to be weakened by hydrostatic pressure. Heavy rain is a major cause of the retaining wall failure as the moisture causes reactive clay to expand and exert pressure onto the retaining wall which then can crack and fail.
- Poor construction through use of the wrong materials for the site.
- Lack of proper and approved construction.
- Weakening of the retaining wall by changing levels at the top or bottom of the wall.
Any movement of a retaining wall close to a home can have a dramatic impact on the existing building causing severe structural damage and in some cases leading to a home having to be pulled down. Foundation movement transmits to the footings which can result in cracks appearing in exterior/interior walls and pressure being placed on the building frame.
The use of retaining walls to support land higher than the footpath is common which can present major problems if they collapse and injure a pedestrian.
Homeowners noticing a crack in their retaining walls should take immediate action and obtain professional advice to manage the issue and avoid a major problem. Anyone considering the construction of a retaining wall should seek advice as to whether an engineer’s design and building approval is required.