# Forum Home Renovation Retaining Walls  Retaining Walls - Australian Standards

## Pgmassey

First time poster. 
Sorry if this has been asked before, but is there an Australian Standard governing the design and construction of timber retaining walls? 
Cheers

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## watson

Nearest we can come up with is a Queensland document from our Forum Library at : http://www.renovateforum.com/f221/ti...90/#post812164
Hope that helps.

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## Pgmassey

Thanks Watson. That's perfect. I have used a similar Timber Qld datasheet to rough out a design for a carport.

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## Belair_Boy

> First time poster. 
> Sorry if this has been asked before, but is there an Australian Standard governing the design and construction of timber retaining walls? 
> Cheers

  *AS 4678-2002 : Earth-retaining structures* 
This Standard sets out requirements  and recommendations relating to the design and construction of  structures required to retain soil, rock and other materials. 
Probably more suited to the engineering types amongst us but that can be said for a lot of standards.

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## Pgmassey

Thanks fellas. Very helpful. The Australian Standards from that Timber Qld data sheet are: 
AS1170.1 - SAA Lodaing Code - Part 1 - Dead and live loads and load combinations
AS1720.1 - Timber structures - Part 1 - Design methods
AS2159 - Piling - Design and installation
AS4678 - Earth-retaining structures. 
My next question is about the depth of the post footings. The wall I need is 1.2m high and approx. 10m long (the length will depend upon what size wales I choose). In the Timber Qld data sheet, it recommends a footing depth around the 1.5m mark. To me that seems a little excessive. I would've thought a depth of 1/2 the height of the wall would be sufficient. What do people here recommend?

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## Master Splinter

Height of the wall or 600mm, whichever is the greater.
(think of it this way - sleepers are 2400, so once you have your 1200 high wall and you add [whatever] for the embedment depth, it's not like you are going to do anything really useful with the offcut, is it...)

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## watson

> Height of the wall or 600mm, whichever is the greater.
> (think of it this way - sleepers are 2400, so once you have your 1200 high wall and you add [whatever] for the embedment depth, it's not like you are going to do anything really useful with the offcut, is it...)

  Excellent thought process....just a bit of digging and its all hunky dory. :2thumbsup:

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## Pgmassey

Thanks again Watson & Master Splinter. 
Next question: what fasteners do I use to fix the wale sleepers to the posts? My posts are 200x75 and the wales are 200x50. See the attached sketch.

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## Master Splinter

With that sort of design, I'd be tempted to use no fasteners at all.  Maybe just shoot a 75mm nail in to hold it while backfilling if you have a nailgun handy. 
The area that always looks the dagy-est (to me at least) is the point where you are butting your sleepers together - this is where any change in size really shows.  
I'm assuming that you will be hiding the butt joins behind the uprights...doing this so that you have the whole 200mm width of the upright available for bearing area means you can hide a multitude of 'can't be bothered to accurately cut to length' sins.  Structurally, there is no reason to have the uprights edge on for a 1.2 meter high wall.

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## Pgmassey

Thanks again. I'd originally planned to go with whole 200 width to cover the butt joins. The only reason i've gone with the uprights edge on is because I followed table 4 of the Timber Qld datasheet (see attached). 
I have to get the design certified anyhow, as local council regulations require certification for any retaining wall over 1m. So i'll see what the engineer comes back with. Thanks again for all the advice.

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## Pulse

I'd use gal batten screws to fasten the wales, the treated pine sleepers are not usually seasoned as will tend to twist otherwise, opening up gaps.
Cheers pulse

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## charlie01

I have a question as well regarding the standards of constructing a timber retaining wall. 
I had a timber retaining wall built recently. I noticed that the lowest sleepers are not sitting on the ground but 7 - 10 cm above ground. Is it normal / standard? 
The retaining wall is 1.4m high and 31m long and had engineering design. 
Thanks in advance.

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## shauck

> My next question is about the depth of the post footings. The wall I need is 1.2m high and approx. 10m long (the length will depend upon what size wales I choose). In the Timber Qld data sheet, it recommends a footing depth around the 1.5m mark. To me that seems a little excessive. I would've thought a depth of 1/2 the height of the wall would be sufficient. What do people here recommend?

  And if you put 100mm of concrete under the post, add that to the depth of the hole.

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## Oldsaltoz

> First time poster. 
> Sorry if this has been asked before, but is there an Australian Standard governing the design and construction of timber retaining walls? 
> Cheers

  If you particularly want the timber look, then you might like to look into facing a block wall with timber. 
The big problem with timber retaining walls is moisture causing rot and water leaks. 
With a hidden block wall you have the advantage of being able to fully waterproof and properly drain the face, resulting in a dry outer wll, perfect for fixing a decorative timber structure to. 
Good luck.  :Smilie:

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