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How to build a timber retaining wall

If you have a sloping block that you want to level out, and you need a retaining wall 600mm or under to do it, a timber retaining wall could create loads of extra space. It could give the kids a level play area, or give you a new entertaining area or veggie patch.

There are a number of different options you can choose and that can be built by a confident DIYer including timber, logs and sleepers.

This is a step-by-step guide to building a simple timber retaining wall. It’s not that hard. Preparation is the key – and maybe another set of hands on the day.

Remember, if you have any more questions you can ask one of the expert associates in your local Masters Home Improvement store.

Before you start

Before building any type of retaining wall it is best to check with your local Council.  

Each Council is different and may require building approval or engineering certification.

Be sure where you’re going to build the wall

Lay out where you are going to build it. Run a string line between two stakes as a guide for building your retaining wall.

How to build a timber and post retaining wall

Retaining walls made from timber, logs or sleepers not only look good, they’re quite simple to put up. As long as you follow a few basic rules, you’ll have a great looking wall that’ll last for years .

Some retaining walls higher than 600mm may require building approval or engineering certification.

Where to start

Choose your timber.

Rectangular hardwood sleepers, or round logs are a great economical choice for low load applications like garden beds.

They are natural, low cost and low maintenance.

Lay it out

Use a string line to mark out where you are going to build your wall.  

Mark your post spacing according to timber length.

Timber must be treated to hazard level H4 or better.

Posts should be spaced at 1.2m intervals apart if your sleepers are 2.4m long, or 1.5 metres apart if you use 3 metre sleepers.

Dig your postholes 700mm deep x 300mm wide.

Fill the bottom 100mm of each hole with coarse gravel for drainage.

Cut your posts to length (1200mm for a 600mm high wall).

Tops of posts should be cut with a slight slope to shed water. Seal all cut ends with an appropriate timber preservative.

Place the end posts in the holes and fill with concrete to ground level.  Leave concrete to set according to manufacturers’ instructions.

Make sure you lean the posts about 5 degrees towards the bank. Once the load of the dirt or rubble is applied, this will help the wall take the strain.

Tie a string between these posts and use that to align the other posts.

Place your first horizontal timber and mark where the upright posts are. Remove, and drill a slightly undersized hole in the horizontal timber where it meets the upright.

Once the horizontal timbers are in place, you’ll be able to secure them with a galvanised spike or nail into the upright post.

Replace your horizontal timber – lining the hole behind the posts.

Make sure the timber is level.

Simply stack additional logs or sleepers on top to reach the desired height securing with nails/spikes as you go.

Sleepers must be placed behind posts.

Behind the second layer of timber, lay slotted agricultural pipe for drainage. Surround this pipe with course gravel.

To prevent excess soil loss through the timber, line the inside of the wall with porous geotextile. This is a permeable fabric used to filter seepage prior to drainage and helps reduce soil erosion.

Do not use plastic sheeting as this could cause water build up and possible wall collapse.

Back fill behind the wall creating a spoon drain on top to help with run off.

Stand back and admire your work.

Important - Please read: All information and tips in this publication are of a general nature only and Masters does not warrant the accuracy or completeness of the information and tips in this publication.  This publication is not intended to be a substitute for expert advice.  Masters advises you to always consult an experienced and qualified person when undertaking jobs of this kind (including consulting a qualified tradesperson such as an electrician or plumber where relevant expert services are required).  You should also consider any safety precautions that may be necessary when undertaking the work described in this publication (including wearing any necessary safety equipment such as safety glasses, goggles or ear protectors or hard hats).  The information and tips in this publication are provided on the basis that Masters excludes all liability for any loss or damage which is suffered or incurred (including, but not limited to, indirect and consequential loss or damage and whether or not such loss or damage could have been foreseen) for any personal injury or damage to property whatsoever resulting from the use of the information and tips in this publication.  Masters also notes that there may be laws, regulations or by-laws with which you must comply when undertaking the work described in this publication.  You should obtain all necessary permissions and permits from council and/or any other relevant statutory body or authority before carrying out any work.  Masters Home Improvement Australia Pty Ltd ABN 21 066 891 307.

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