Four things you need to know before building a retaining wall

Four things you need to know before building a retaining wall

Make a plan

Before you get started, you’ll need to design your wall. If it’s over a metre high, you should check with your local council first. You may have to have an engineer design and certify the wall.

Once you’ve got a design, you can work out all the materials you’ll need.


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Timber walls are a very DIY-friendly option. Treated pine sleepers are popular as they are easy to work with and good value for money. Hardwood sleepers are another option. To build your wall, dig holes and insert vertical supports using thicker sleepers, at least 75mm thick. Space the supports every 1.2m for 2.4m long sleepers, and 1.5m for 3m long sleepers. The horizontal sleepers can be 50mm thick. Place them against the vertical supports, make sure they’re level then bolt the two together. To finish off you can paint or stain the wall to match your garden or outdoor area.

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Concrete blocks

A great DIY option for a masonry wall are interlocking blocks that don’t need any mortar. As a bonus the blocks come prefinished so once you lay the wall there’s no more work needed to make them look good, saving you time and money. Dig a footing then lay roadbase in the trench and compact it, making sure it’s level. All you do then is simply lay out the blocks, locking them together as you go. It’s that easy.

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Go natural

To create a natural feature in your garden that’s less formal than timber or blocks, use a natural rock such as sandstone or granite. Building the wall is like doing a vertical jigsaw puzzle as you try to find bits of rock that lock together. Mortar the first rocks down then lay a bed of mortar between the rocks as you build it up. Finish off by filling the joints at the front of the rocks with more mortar, wiping with a sponge for a smooth finish.

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Water can build up significant pressure behind a retaining wall so it’s important you provide for drainage behind it. Lay a slotted ag drain at the base of the wall and fill above it with a free-draining material such as gravel. Encase the whole lot in geotextile fabric which allows water through but prevents soil from washing in and clogging up your drain.

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