There are a number of circumstances that arise in construction projects that require retaining walls. The most typical occasion will be to retain earth banks that either stops the earth from sliding or in order to protect a building or an object. There are various methods and materials that are used to construct these walls that usually include concrete, metal or wood.
Using concrete sleeper retaining walls or wooden-crib walls are typically used for the domestic purposes as they are easier and more affordable to handle. Domestic uses tend to be smaller and will have a lighter load that is placed upon them. In addition there are aesthetic requirements particularly for the purpose of garden walls.
Concrete has long since been regarded as one of the best products to use when it comes to constructing a retaining wall. This is due to the fact that it has exceptional structural properties as well as being able to repel most of the elements.
When using concrete sleeper retaining walls, the concrete product is designed with steel reinforcement encased inside the concrete that stops rust from occurring. Once the concrete has cured it offers outstanding protection to the steel along with a strong structure.
Reinforced-concrete retaining walls are easily constructed on a site with steel cages that offer reinforcement along with wooden shuttering that forms the structure. Another alternative would include using precast concrete-sections that have been previously manufactured that assists in reducing construction time.
Other methods include precast blocks that typically interlock in order to produce a gravity type retaining wall. These types of retaining walls often require a gradient sloping back. These can be extremely useful when an end product is required to suit a specific environment.
Installation Guide For Using Concrete Sleeper Retaining Walls
This guide is based on the installation of a wall that is 1 meter in height using 2 meter sleepers. For walls that require a different height, the figures will need to be adjusted accordingly.
Step One – The right position
When setting up a retaining wall, the correct alignment will need to be established, especially when the retaining wall is situated along a boundary. The person that alters the natural level of the ground is held responsible for the wall. However, it is advisable to always first check with the appropriate local council because every region has different laws.
Step Two – Setting up the layout
This involves the layout, string will need to be placed along the exact line of the retaining wall. Pegs should be set 500mm past every end of the proposed retaining-wall to avoid the end-holes from disturbing the string line. Now a mark will need to be used for where every hole will be dug and the holes need to be 2015mm apart when using 2m sleepers.
Step Three – Cutting Steel
As an estimated guide the steel must be cut at the double height of the proposed wall that means that a wall that is 1m in height requires 2m steel lengths.
Step Four – Digging the post holes
This step involves digging the holes. These holes need to be dug to the same height of the wall with an additional 100mm. The diameters of the holes should be around 450mm.
Step Five – Concrete the posts
The next step involved in using concrete sleeper retaining walls. Now the steel-uprights should be concreted in place making sure to leave a gap of around 2010mm between each. The upright should be checked using a spirit level. The holes should never be overfilled with the concrete mixture and the distance from the top part of the upright to the top portion of the concrete must not exceed 1010mm.
Step Six – Placing the concrete sleepers
Once these posts have been allowed to set for a minimum of 24 hours, the sleepers can now be slotted. It is always advisable to start with the bottom sleeper and proceed to check on the measurement that lies from the top part of a sleeper to the top part of an upright. On a 1m wall the measurement should be around 800mm. If this measurement goes over 800mm, packers can be used under the sleeper until the correct height is reached.
The packers will need to be made out of materials that do not disintegrate. Even though the sleepers can be slotted 24 hours after uprights have been installed successfully, the wall should not be back-filled until the concrete has cured completely. An I Beam should be used for the intermediates and a C channel should be used for the wall ends.
Step Seven – Backing the sleepers
Once the sleepers have been slotted, a plastic membrane will need to be placed behind the retaining wall along with a pipe placed along the bottom of the plastic membrane. The pipe should be covered with around 200mm of gravel in order to provide sufficient drainage.
Step Eight – Back-filling the concrete sleeper retaining wall
Back-filling concrete sleepers have been created with the purpose of taking the pressure of the soil that is behind them. However, this does not mean that the soil should be compacted behind this wall. As a rule of thumb the soil should not be compacted closer than the actual height of the wall.
The instructions mentioned above are a basic recommendation. It is also advisable to contact a structural engineer in the cases of larger walls. The structural engineer is used to ensure that the wall has structural integrity. For further queries it would be best to get in touch with the local council.