Retaining walls are required where it is necessary to have an abrupt change in ground levels. This situation arises where the general level of your yard is lower than the adjacent plot, the land is sloping, and you need to maintain a level in your garden that is substantially lower than the level at the edge of your plot. You can, of course, use the slope of the land to your advantage and allow it to remain so, but this can cause problems in landscaping.
A better solution is to construct a retaining wall at the edge of your property so that you have ground at the level that is convenient to your landscape. Stone is a very popular material to build retaining walls though they can also be constructed in concrete, brick, wood, or with steel sheets. Stone retaining walls can be built using cement mortar to bond the stones or using just earth as a filler in what is known as dry wall construction.
Retaining walls have their stability decided by the weight of the materials that make up the wall, especially if they are of stone or brick. For concrete and other materials advantage can be taken of the tensile strength of the materials to design slimmer walls. The earth behind a wall only exerts pressure from a triangular wedge of the earth immediately behind a wall, and the weight of the stone or brick has to be at least twice the weight of the soil wedge, for a retaining wall to do its work of supporting the earth.
It is best if retaining walls are given a foundation that is below the frost line and can be of concrete or any other layer that gives it a horizontal base. The width of walls are kept at least one fourth of the height of the wall, and the wall width can reduce to one-quarter of the base at its top layer. The earth behind retaining walls can retain water, which can increase pressures, and to reduce this. It is customary to leave drainage openings in the wall, with pipes at regular intervals, which will allow the wall to bleed and allow the water to drain away.
The wall needs to slope back from the soil that is being retained by it. This increases the strength of the wall. In case a slope construction is not possible you can reduce the width of the wall after every foot of height. Retaining walls can add to the landscape and give a certain elegance to them. They can be made still more attractive by having creepers planted at the base of the wall and allow them to cover the wall as they grow.
It is essential that the top of the wall be capped with a layer of concrete or plaster, so that no erosion can be caused by rain or other reasons, which can cause the various layers to deteriorate. Metal sheet piling is easy to construct as retaining walls, and will require lesser width, which can be an advantage for your landscaped area.