How to Build a Railway Sleeper Retaining Wall

How to Build a Retaining Sleeper Wall

Railway Sleepers are an ideal material for creating retaining walls and garden dividers, providing a quick and simple alternative to rendered concrete or brick walls, and popular in both traditional and modern garden landscaping for their architectural and long-lasting qualities.

The design of sleeper walls is also incredibly versatile depending on the wall's function - use sleepers horizontally or vertically, self supporting or with support posts, stacked on the long or short side, with an added seating surface or integral steps.

How to Build a Retaining Sleeper Wall

Hardwood or softwood sleepers?

Reclaimed sleepers will give your garden a more rustic or vintage look. Due to their creosote content and old fixings they're not suitable for gardens with small children or for retaining vegetable beds.

How to Build a Retaining Sleeper Wall

Softwood sleepers are uniform in their dimensions, giving a clean modern appearance. They're lighter to handle than reclaimed sleepers and are easier to cut. When regularly treated or painted they should last at least 20 years.

How to Build a Retaining Sleeper Wall

Hardwood oak sleepers are also uniform in their dimensions, and are more durable and a great deal heavier than softwood. Because of oak's natural durability it is not necessary to treat or paint them, and they will naturally weather to a natural silver colour. An oak sleeper would be expected to last at least 40 years.

Do I need a foundation for my sleeper wall?

How to Build a Retaining Sleeper WallWhen using railway sleepers vertically then your wall will always need to be solidly fixed, however for horizontal sleepers it depends on the size and position of the wall. Sleepers can be laid directly onto firm ground, however it's recommended that at the very least a bed of sand or aggregate is used to assist drainage and provide a firm footing.

Purists will always insist on a concrete bed, however if the wall is additionally supported by posts then this is not always necessary.

Retaining walls with horizontal sleepers

Using sleepers horizontally is the traditional way to build a sleeper wall, with the sleepers positioned on either their long or short side. 

Laying sleepers on their long side will give a stronger construction, but you will need more sleepers to achieve the required height of wall. However, because the wall is heavier and more stable you are less likely to need additional support posts.

Lay out the first row of sleepers horizontally and then the next layer on top, overlapping the joints like brick laying. Use 150mm landscaping screws to fix these two rows together and then continue until you have the height of wall you want.

How to Build a Retaining Sleeper Wall

When using sleepers on their short side you will definitely need additional support for the wall in the form of posts set at regular intervals along the wall. The greatest support will come from posts positioned on the outside of the wall (i.e. not the soil filled side), however for lower walls these can be hidden on the 'soil' side. Always use UC4 treated fencing timber or posts, and treat any cut surfaces with brush on endgrain treatment.

Set your support posts at regular intervals using a sleeper to judge their position, and set in postmix concrete as you would for a fence post (that is to a depth of 1/3 of the post). Then fix the sleepers to the posts using 150mm landscaping screws, drilling from the post into the sleeper.

Metal posts can also be used as support posts, the sleepers being fixed to the posts with brackets.

To extend the life of the retaining wall, a waterproof membrane can be attached to the soil-facing side before back-filling.

How to Build a Retaining Sleeper Wall

Retaining walls with vertical sleepers

Using sleepers vertically is a great solution when building a retaining wall on sloping ground, creating a curved wall, or even building a freestanding feature wall within a garden. Achieving a perfectly uniform top to the wall is more challenging, however deliberately staggering the tops of the sleepers at different heights can be used as a design feature.

Dig a trench to follow the path of your wall, one third the depth of the sleepers. Line the bottom of the trench with a layer of shingle, followed by a shallow layer of dry postmix concrete, then position your sleepers and backfill with dry postmix. Finally add the desired amount of water to the postmix, allowing you to reposition the sleepers as the postmix sets.

Once the concrete is set, you can provide additional support if necessary by fixing the sleepers together on the 'soil' side using lengths or UC4 fencing timber or metal brackets. A waterproof membrane can also be applied if required.

How to Build a Retaining Sleeper Wall

Does my retaining wall need drainage?

Adequate drainage is essential to avoid building a pond rather than a retaining wall. For larger walls it may be necessary to install a dedicated drainage pipe at the base of the wall, however for most garden applications or smaller walls the retained area should drain naturally with a little help.

A simple method is to create a drainage tube with a length of permeable membrane and gravel. Before back-filling the soil behind your retaining wall, lay a length of permeable membrane at the base of the wall then cover half the width next to the wall with a 20cm wide and 20cm deep layer of large gravel or ballast. Fold the remaining membrane over the top of the gravel then cover with earth. This will stop the earth washing into the gravel over time and blocking the drainage.

How to cut railway sleepers

A circular saw is the best method for cutting railway sleepers, although a hand saw can be used for softwood sleepers. However a circular saw blade may not completely cut through the thickness of a sleeper in one pass - cut through one side, then turn the sleeper over and recut to finish the job.

Always remember to treat any cut ends of softwood sleepers with End Grain Treatment to preserve the weatherproofing of the timber. Watch out when cutting reclaimed sleepers for any nails or screws that may still be embedded in the sleeper.

Alternatively,  your local AVS Fencing & Landscaping Supplies branch may have the ability to cut your sleepers to size for you.

For information on the wealth of other uses for railway sleepers in garden landscaping, read our article on How to use Railway Sleepers in Your Garden.

For instruction on how to build a raised bed from railway sleepers, read our article here.

Ask the experts

For further advice about your railway sleepers project don’t hesitate to speak to our experts at your local AVS Fencing & Landscaping Supplies branch. Our ranges of sleepers are all available from stock, click and collect from your local AVS Branch or home delivery within our AVS Branch delivery area.

How to Build a Retaining Sleeper Wall

6th May 2021 AVS Fencing & Landscaping Supplies