Retaining walls can be a dramatic and beautiful addition to any landscaping project, whether residential or commercial. These structures are essential for providing flat, even ground on slopes, but as you can imagine, the stress of holding up the weight of all that soil can test even the most durable of materials. As such, choosing the right material before your project begins will save you a lot of maintenance, expense and general headaches in the future.
A common sight in parks and gardens, wooden retaining walls are among the cheapest options, as well as being comparatively quick and easy to install. However, most woods are not capable of dealing with the pressure of tons of earth, and wooden retaining walls should not be expected to last forever before bulges and cracks begin to form. There are, however, a number of ways you can increase the durability and serviceable lifespan of a wooden retaining wall:
- Use woods that are pressure-treated to resist moisture, mould and insect infestation (railway sleepers are heavily impregnated with anti-rot chemicals and are commonly used for retaining walls)
- Limit the height of your wall, introducing a multiple-tier system if dramatic ground grade changes are required
- Fitting sturdy braces to walls and attaching them to deep anchors
An excellent choice for complementing period features, brick retaining walls are attractive and enormously durable, and can expect to stand up to years of weight and pressure. However, they are a particularly labour-intensive choice of material that almost always require professional landscaping services and bricklayers to install. To reduce installation costs, consider applying a 'veneer' of brick to a core made from strong and more easily laid materials, such as reinforced concrete. You should also make adequate provisions for soil drainage through your wall (with gutters, sluices etc.) as brick retaining walls tend to have poor drainage.
An unusual and remarkably cost effective choice, gabions are simply wire cages filled with rocks that can nonetheless be used to create a very sturdy retaining wall. These structures are often seen used as sea defences against erosion, so gabions make a particularly apt choice for coastal landscaping projects -- this is particularly true when it comes to making a waterside retaining wall, as gabions are not anchored in place and can therefore deal much more effectively with land erosion, shifting to meet the new contours of the earth.
However, most gabion cages are made from steel and should not be expected to hold out against rust forever. Aluminium cages are available, but are more expensive and considerably less durable.
Concrete retaining walls come in two varieties; block and poured.
- Concrete blocks are cheap and easy to install, making them a popular choice for residential projects or other retaining walls built to a tight budget. The versatility of concrete blocks means that they can be used to create artfully curved walls, and if you are not fond of the look of bare concrete they can be covered with more attractive materials (such as natural stone or brick) relatively easily. However, because they are made from individual blocks they cannot be cantilevered like poured concrete walls, and tend not to be quite as durable.
- Poured concrete is an excellent choice for contemporary or modernistic projects, and can be crafted into sleek lines and smooth curves. They are even stronger than concrete blocks, and can be poured with cantilevered footings to provide excellent strength. However, they require professional skill (and a lot of hard cash) to lay and install, and need to be immaculately designed in order to avoid bulges and waves appearing at weak points of the wall.