What post distance for retaining wall?

RubyH

Hi all,

Im wanting to replace an existing retaining wall which is currently 1.5m high with one that will be 1.8m high. Im wanting to use 175SED x 3600 strainer posts spaced out at 2mc/c dug down 2m into the ground. The retaining timber will be 150x50. I had spoken to a friend who is a builder and he said 2m was fine but wouldn't recommend going any wider. The current posts are much smaller than what im wanting to use and the retaining timber is narrow half rounds, not sure when it was built but the current spacing is 2.4m. Whats everyone's thoughts on 2m c/c using 175SED strainer posts with 150x50 retaining timber? 

Thankyou for your suggestions and time

JacobZ

Hi @RubyH,

Welcome to the Bunnings Workshop community, it is wonderful to have you with us.

In Australia, retaining walls generally require council approval and engineering once they are over 1 metre high, or lower if they are supporting a surcharge such as a driveway, building, or fence. Requirements vary slightly between states and councils, but anything above 1 metre should always be checked with the local council and usually needs an engineer’s design.

In New Zealand, retaining walls can usually be built without consent up to 1.5 metres high, provided they are not supporting extra loads. Once a wall is over 1.5 metres, like in your case, where you are increasing from 1.5 m to 1.8 m, it typically requires building consent and an engineered design based on the relevant building code.

While you are improving the standard of the wall from what was there before, this doesn't necessarily mean that it is up to the current building code. 

The only suggestion I can offer is that you speak with your local council about your requirements in terms of building approval. Unfortunately, I am pretty certain that you're going to need to speak with an engineer for this one.

Let me know if you have any further questions.

Jacob