When you build a retaining wall you add visual structure to your garden and increase the usability of sloping ground surfaces. It’s one of the larger DIY tasks, but by following the steps below, and with adequate planning and adherence to sound construction techniques, it can be accomplished by the dedicated DIY enthusiast.

Building Your Own Retaining Wall

  • Begin by determining the position, layout and size of your retaining wall and mark it with string and pegs.
  • Excavate your site. Retaining walls are generally built against a bank or slope of earth and enough of the bank-face will need to be cut away to allow the wall to be set vertically.
  • Cut a trench the width of your blocks into the ground along the length of the excavated bank face – use string and pegs to ensure a straight line. The trench should be deep enough to accommodate a layer of base material and allow the first course of blocks to be set three quarters of their thickness below ground.
  • Once the trench is cut, lay your base material. This is perhaps the most important part of the retaining wall building process as a firm, well-laid base will contribute greatly to the strength and stability of your wall. Base material should consist of a 10cm–15cm layer of crushed stone and should be compacted thoroughly until a surface that does not shift when walked on is achieved. Use a spirit level to ensure the base is level.
  • Set a string line as a guide for straightness and lay your first course of blocks. The edges of the blocks should touch and they should be level with each other on all sides.
  • Continue laying blocks until the desired height is reached. How the blocks are fixed will depend on the material you are using for the construction of the retaining wall. Segmental blocks, for instance, simply slot together and need no mortar. More conventional blocks will require the use of some form of adhesive.
  • Finish your wall with retaining wall caps. These produce a more finished look and prevent weeds from growing between the joints on top of the wall.
  • At this stage your retaining wall will still have a cavity between it and the excavated bank face. Before filling this cavity, provision must be made for drainage. Do this by laying a 15cm deep layer of gravel behind the base of the wall. Place a slot drain on top of this and ensure that its ends protrude beyond the wall.
  • Complete the backfilling of the cavity with compacted earth.

Following these guidelines will help you create an attractive, functional and long-lasting addition to your property. Ensure your success by keeping them in mind when you set yourself the challenge of building a retaining wall.

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