• Measure the height and length of the proposed wall and multiply these two numbers together to calculate the square meter surface area. Multiply this number by 12 to obtain the number of blocks required for the wall.
  • Retaining walls must comply with local building regulations.
  • A rule of thumb is, where the wall is less than 1,2m built to a batter of 70° (from horizontal) and where soil and drainage conditions are good and well compacted, there should be no need for an engineer. Where however, the height of the wall exceeds 1,2m, or if problem soils (clay) or a high water table exists, or where a structure is to be erected on top of the retained fill close to the wall, or even load bearing walls, then the services of an engineer or competent person are required. In such cases, the local authorities should insist on a design and stability certificate from the engineer

Typical Installation

  • Measure the wall layout and mark the course using string and stakes.
  • Dig a trench 400mm deep, 600mm wide and create either compacted gravel or a concrete base 200mm deep. (Gravel foundations are usually sufficient for walls less than one (1) meter in height.) It is imperative that the foundation is level in all directions.
  • Place the first row of blocks on the foundation ensuring that the concave and convex interlocking ends of the blocks mesh as closely as possible. The blocks must be placed level in all direction on the foundation. If need be and to level the first block row perfectly, one can embed the first block row in a mortar bed.
  • Each marker (inset dimple) on the block represents a 10º (ten degree) change in angle. For a twenty degree curve, line up the second marker with the main marker. A maximum turn of 105º can be achieved. The seven markers on the large circumference of the block represent an angle of 45 ° between each marker.

What is the “OFF SET”
One measures the OFF SET at the beginning of each block row. It is the dimension measured from the edge of the first block of the first row to the edge of first block of the second block row laid and so on.
For the visual effect of a retaining wall it is important to note that the distance / dimension of the OFF SET at the beginning of each block row should always be the same. Even if curves, circles or soft angles are integrated into a wall, this rule applies. For instance if one chooses to lay the first block of the second row of blocks exactly halfway over the joint of the first block row, then each subsequent row should be laid the same way. The GreenLock 12 series is 380mm long the OFF SET dimension would then be 180mm.
It is not important what the OFF SET dimension is, as long as it always the same dimension with each row laid. If one follows this advise the finished wall will look stunning, aesthetically pleasing and important for the eye, with evenly fluted joints. If one does not follow this rule, the wall will not be weaker but it will visually look untidy and create a “dizzy” look.

Important Note:
If a sharp corner, like 45 or 90 degrees corner is integrated into the wall this rule does not apply. For sharp corners and after the first block row has been placed and laid including the corner, the second row of blocks should start with the corner block placed exactly over the bottom corner block using the chosen Set Back dimension. The next blocks are then laid in both directions away from the corner block. The joints between the blocks of each block row will automatically form an evenly distributed fluted pattern over the whole length and height of the finished wall.

The 45° marker on the back block lines up with the centre marker on the front block, means that there is a 45 ° angle between the blocks.

The 45° marker on the back block lines up with the 10° marker on the front block giving an angle of 35° between the blocks.

The 45° marker on the back block lines up with the 10° marker on the front block giving an angle of 35° between the blocks.

The 90° marker on the back block is lined up with the middle marker on the front block giving a right angle turn to the wall.

For steep and/or high walls the first layers can be filled with concrete and/or steel bars for extra stability.
Place a flexible perforated drainage pipe, 75-110mm in diameter, behind the first row of blocks, wrap this in filter fabric. Ensure that 19mm gravel is wrapped in filter fabric around the drainage pipe. The gravel layer should be at least 400mm wide and 220mm deep. Please note that for proper drainage the drainage pipe assembly must be placed slightly higher than the ground surface area of the front of the retaining wall. Drainage outlet pipes, connected to the main drainage pipe, should be installed intermittent and in accordance to the length of the wall, allowing any accumulating seepage water behind the wall to escape freely.
To achieve the desired angle and setback of the wall, refer to the supplied setback table. (The setback distance is measured from the outermost part of the block. A setback of less than 21mm will allow soil to fall through the block and a setback of 63mm will align the concave and convex sections of alternative layers.)
Remember to fill consecutive blocks with topsoil if these are to be planted up and remember to compact blocks and backfill. Behind all layers there should be a layer of minimum 300mm wide of compacted drainage material, such as free draining sand.
Your wall is now ready to be planted up or left as is.