Are you buying an existing home in Brisbane or Ipswich? Does it have existing retaining walls? Don’t miss out on a prime opportunity to negotiate a potential $10,000 plus on the list price, saving you money on the purchase.
If your financier is required, you must ensure you have money available to perform a building inspection. A professional building inspector’s report can be invaluable to your investment, saving you a lot of financial strain in the future. Also, Educate yourself on the basic standards of retaining wall building code and local Council laws. (refer to Brisbane City Council, Ipswich City Council).
Here are our top 6 defects to look for in an existing retaining wall structure:
Termites
Don’t be fooled; these little buggers don’t discriminate between types of timber. Whether hardwood or pine timber is used, they will make a meal out of any wood retaining wall, and once they’ve started, it’s only a matter of time until they compromise the structural integrity. Yes, timber can be treated with chemicals to prevent termite inundation, but this is merely a delaying process as these chemicals don’t last forever.
Weather Damage & Rot
Although weather damage can be evident to even the untrained eye, it can also be hidden. Be sure to check for gaps between the timber posts and concrete footings. These gaps can act as a reservoir for water. Once water trickles into the hole, it will remain there for some time as it’s not subject to sunlight and doesn’t evaporate as quickly. This, over time, can cause the retaining wall posts to rot and eventually fail.
The Direction It’s Leaning
A retaining wall should lean, but not just in any direction. Your wall should lean into the side of the hill it is being built against. Australian Building Code requires a retaining wall to have a 30mm lean back towards the cut land. This prevents bulging and cracking of the structure and subsequent failure should the drainage behind the retaining wall be inundated with water.
Drainage
No matter what material is used to build a retaining wall, the drainage system installed behind the wall is the most critical aspect of the entire structure. This is also the most overlooked aspect. Because you cannot see the amount of drainage gravel, geo-textile fabric, or type of drainage pipe installed, Brisbane contractors will skimp on these to save a buck.
The law states that despite the height of the retaining wall it should, as a minimum, have behind it a 65mm slotted agi-pipe running the full length of the wall and protruding 300mm out each exposed side. It also must have geo-fabric laid along the entire length and height of the wall to prevent seepage between the sleepers or boulders and finally, the drainage gravel must be 20mm in size and be installed at a depth of 200mm from the top of the retaining wall and at a width of 300mm.
Does the Retaining Wall Comply with Building and Council Laws?
It is across all Council regions in Queensland that any retaining wall, tiered or not, that exceeds a ground-to-top sleeper height of 1 metre must be engineered, built by a QBCC Licenced Builder, Certified, and have Council Building Approval. Furthermore, suppose the retaining wall is located on a boundary line and doesn’t exceed 1 metre in height but has a fence attached to the top that exceeds 2 metres in combined height. In that case, it also must be engineered, certified, and approved by the Council.
Before you sign any new home contract, we highly recommend requesting a copy of the current building approval for that structure. Should the structure not be approved by the Council, then it is an illegal structure that should not be included in the home’s value. It also leaves you open, as the new homeowner, to be fined by your local Council and given 30 days to rectify the illegal structure.
Don’t Underestimate The Signs of Failure
If only one or a few retaining wall posts are failing/leaning in the wrong direction, it’s not a matter of just replacing those posts or bays. This indicates that the retaining wall is on its last legs. Yes, you can patch the problem by replacing those parts, as so many Brisbane contractors do, but you are merely delaying the soon-to-be failure of the rest of the structure. You are far better off financially replacing the entire retaining wall all at once than having trades return repeatedly. Brisbane contractors are happy to perform a retaining wall repair job.
As a fully licensed QBCC retaining wall builder, Rycan Retaining and Earthworks have performed hundreds of earthmoving and retaining wall projects for residents of the Brisbane West and Ipswich region for over ten years. We’ve seen it all. 70% of all inquiries we receive are to replace failed retaining walls. Unfortunately, most people underestimate the cost, value a retaining wall adds to their property, and risks associated with a fallen retaining wall once it’s too late.