Retaining walls might seem simple at a glance, but there's more going on than first meets the eye. A typical residential retaining wall must hold a considerable amount of soil while allowing for adequate drainage and resisting hydrostatic pressure. An improperly constructed wall may work well for a while, but will eventually fail due to poorly managed stresses or underlying construction issues.
Two key components of any retaining wall are its support design and foundation. Understanding the difference between these two elements will help you decide on the type of wall best suited for your particular application.
Understanding the Foundation
Like any structure, the success of a retaining wall depends on its foundation. The foundation serves several roles, each of which is critical to avoiding early and catastrophic failure. The primary role of the foundation is to provide a smooth and level base that can resist erosion. Without this, the soil under your retaining wall will eventually wash away, leading to collapse.
You may occasionally see retaining wall foundations referred to as "footings." A structure's footing is the portion of the foundation that physically connects it to the ground. In other words, the footing is typically the lowest part of the foundation. The footing is typically coarse gravel or a concrete slab for retaining walls.
The appropriate footing for your retaining wall depends on several factors, including height and overall construction. Low retaining walls that utilize dry stack (non-mortared) construction methods only require relatively shallow gravel footings. On the other hand, taller or rigid masonry retaining walls utilizing mortar will usually need a concrete footing pad.
Understanding Retaining Wall Support Design
Your retaining wall needs to resist a surprising amount of force. The taller the wall, the more earth it must hold back. A low wall can often rely on its own mass to resist the force of the soil behind it. As walls get taller, they may require additional support to avoid breaking or toppling. Several retaining wall designs exist to address these issues.
For example, two common options are cantilever and counterfort designs. Cantilevers connect the wall ("stem") to a solid concrete base. The direct connection between the wall and footing can allow for taller walls without concern that the wall will topple forward. A counterfort wall adds additional concrete supports to the rear of the wall, generally allowing for taller and stronger walls.
Ultimately, the best wall for your project will depend on your budget, required height, and aesthetic considerations. Whatever your needs, the correct combination of support design and foundation will help ensure your retaining wall will perform reliably for many years to come.
For more information, contact a professional retaining wall installation service in your area.