How To Build A Retaining Wall
Suggested Tools Checklist:
- Protective gloves|checked
- Safety glasses
- Ear protection
- Spirit level
- Granulated drainage material
- (12-20 cm) to allow free draining|checked
- Agricultural drainage pipe (minimum 90mm diameter|checked
- Course sand for levelling pad|checked
- Lump hammer/Rubber mallet
- String line and pegs
- Garden broom|checked
- Road Base|checked
- Masonry cutting tools (if required)
Preparation and Planning
Locate your wall by marking out the ground where your wall will be built. This can be done by marking with stakes and a string line or by marking the ground with spray paint. Dig a shallow trench approximately 180mm deep and 350mm wide. Fill the trench with crushed rock or road base and compact until it forms a 100mm deep leveling pad. Spread and level approximately 25mm of coarse sand as a bedding layer.
Laying the First Course
Place the blocks side by side on the leveling pad using a string line along the back of the units for alignment. Level each block side by side and front to back using a spirit level. Spend time on making sure the first course is level so that further courses will also be level.
Install a 90mm agricultural pipe at the rear of the wall for drainage and surround with the granulated drainage material, such as blue metal. This should be 300mm wide. Backfill behind the drainage layer. Do not use clay. The agricultural pipe needs to channel water away, so it needs a fall and escape.
Laying Additional Courses
Sweep the top of the previous course to remove all drainage material. Place the next course in a running bond pattern half way across the first course. Place the drainage material and any backfill behind the second course and carefully compact. Continue to stack units placing drainage material and compact backfill for each block height until your wall is complete. On the last course of blocks, place a line of adhesive back and front and place the capping unit. Ensure the wall does not exceed heights as recommended by the manufacturer. For higher walls you may need engineer specifications.