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The natural look, strength and versatility of timber makes it an ideal choice for inexpensive garden edges, steps and walls to terrace sloping sites. Walls up to one metre in height can follow a basic design and can usually be constructed using standard timber products. An engineer will be required to plan and design walls greater than one metre, including the footings and drainage.
Treatment

Timber sleepers and round (or half-round) poles and logs are ideal for creating a retaining wall up to 1m high. However, all timber components need to be treated to Hazard Level 4 (H4) or better.

For further advice on timber treatment and hazard levels, refer to the link below:

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Posts

The base of the post hole needs to be filled with a minimum of 100mm of gravel (to effectively drain moisture).

Walls up to 400mm may have concealed posts, with sleepers fixed to the outside of the posts (with hot dipped galvanised batten screws, coach screws or bolts). Walls above 400mm must have the sleepers fixed behind the posts.

Drainage

The top of timber posts should be shaped for water runoff and be sealed with a suitable fungal resistant preservative treatment.

Drainage needs to be provided behind a wall above 400mm high, in the form of a polyethylene drainage pipe draining to a suitable outlet.

To prevent backfill material from flowing through the gaps in the wall, and to assist with drainage, a geotextile should be placed to the inside face of the sleepers, and between the drainage pipe and backfill.

Backfill should be a free flowing material for example ashes, sand or gravel and should be installed no sooner than three days after concreting posts.

Maintenance

To ensure the ongoing structural stability and safety of your wall, regular monitoring is essential - especially after weather events like heavy rainfall. Your inspection should detect any cracks or ruptures, excessive movement, drainage issues and physical or environmental changes, all of which should be attended to immediately.

Safety

Working with timber produces dust particles. Protection of the eyes, nose and mouth when sanding, sawing and planing is highly recommended. Refer to tool manufacturers for safe working recommendations for particular items of equipment.

As with all treated timber, do not burn offcuts or sawdust. Preservative treated offcuts and sawdust should be disposed of by approved local authority methods.

More Information
Download the Timber Queensland Technical Data Sheet (TDS) 08 - Timber Garden Walls here:
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