Retaining walls are one of the most dramatic and effective ways to improve the appearance of your home landscape while increasing the amount of useable space in your yard. If you want to expand the area for a patio project or create raised planting beds, a retaining wall is often your best option. There are a number of precast blocks suitable for retaining wall construction. While the appearance and colour of blocks you select are a matter of personal preference, there are other considerations that will affect your choice of wall material, in particular, the height of the wall.
Why is Wall Height Important?
Retaining walls are designed to hold back soil and earth. The taller they are, the stronger they need to be. Soil, particularly wet soil, will exert pressure on the back of the wall. For low retaining walls, approximately two feet tall or less, there are many options for wall materials. Once the wall height reaches the two to three foot range, look at retaining wall blocks that are specifically engineered for more demanding situations.
Low Retaining Wall Materials
For retaining walls that are two feet tall or less, consider using natural wall stone or concrete interlocking blocks. The wall stone can be guillotined or random and comes in a variety of colours: beige, brown, charcoal and shades of gray. The size of wall stone varies, but about 4-8 inches high and 6-8 inches deep is typical. The interlocking blocks also come in a range of colours and textures and also with similar dimensions. Two or three rows of stacked wall stone is enough to create an attractive, natural looking retaining wall. Low walls also work well as places to sit and can add a lot of potential seating spots to your outdoor patio.
Medium Height Retaining Walls
For walls that are two and half feet or taller, it is best to use an interlocking retaining wall block or armour stone. Interlocking wall blocks have grooves and beads that keep the blocks in place, protecting against shifting due to soil pressure. There are several manufacturers that make this type of product. You can choose from a variety of styles and colors. The blocks are designed to make installation relatively easy.
Armour stone also works well for the medium to tall wall. Most armour stone is approximately 20-30 inches high by 24-36 inches deep and 2 or more feet in length. Its large size makes it a good option for a medium to tall retaining wall with beautiful, natural looking results.
Tall Retaining Walls
Once your wall reaches a height of four feet, special considerations may be called for. The type of soil you have and the conditions behind the wall become more important. Talk to your landscape supply company to see if additional assistance for the design of your wall is needed.
Additional Materials for Retaining Wall Construction
As with other types of landscape construction, the parts of retaining walls you don’t see are crucial to the success of the final product. Retaining walls should be built on a compacted base of drainage stone or clear stone. The stone layer is usually 10 – 12 inches deep; taller walls need more stone. This reduces the amount of water pressure on the wall. Perforated drain pipe should be added as part of this base construction, behind and below the wall to carry water away.
Due to the size and weight of retaining wall blocks and stone, site access is an important consideration. Interlocking wall units are somewhat easier to move than large natural stone and armour stone. If you have a backyard that heavy machinery cannot get to, interlocking units may be your best choice.
Regardless of your site conditions and design style preference, there are numerous retaining wall materials to choose from. Talk to your landscape supplier and visit their display yard to see your options in person. It’s the first step in making a long-lasting, functional and attractive improvement to your home landscape.