What is a Retaining Wall?
A retaining wall is a structure designed to uphold the soil behind it. This allows for changes in the grade of a plot and flat areas to be used for building structures or backyard features. Several factors must be considered in order to build the proper retaining wall for your property. For example, property owners will need to determine the properties of the soil, the elevation and slope of the ground, and what the height of the wall needs to be. These factors will determine what type of wall will be needed and how it should be designed.
A variety of wall types, such as poured concrete walls, concrete or masonry block walls, sheet pile walls, and others, can then be designed and built to achieve the desired outcome. For taller walls, it will also be necessary to utilize a soil engineer or geologist to ensure the surcharge of the soil is retained by the proper type of retaining wall and built within standard engineering practices.
What are Types of Retaining Walls?
Retaining walls are popular in both residential and commercial landscaping. Besides preventing soil erosion, retaining walls can physically transform the landscape of a property. The four most common types of retaining walls built in construction are:
1. Cantilevered Retaining Wall: This is the most common type of retaining wall, used in a variety of applications for medium to large heights. Typically, they are constructed of concrete, with the stem (the wall itself) anchored to a concrete footing below that is used to resist the soil weight and prevent tipping. These walls are reinforced with steel rebar to achieve maximum strength.
2. Gravity Retaining Wall: These walls depend on their mass to resist pressure from behind and are good for short landscaping walls. Gravity retaining walls are the most basic, as they allow for the widest amount of variety when it comes to materials.
3. Sheet Piling Retaining Wall: Walls that are usually used in soft soil and tight spaces. A thin wall of steel, wood, or vinyl is driven 1/3 above the ground and 2/3 below ground directly into the soil. They have a vertically corrugated structure to provide additional reinforcement.
4. Anchored Retaining Wall: Often used for structurally thinner walls or where higher loads are expected. This wall allows for a variety of “fronts” of retaining walls to be supported by anchors driven back into the soil and attached by cables or strips. This method can be used in conjunction with any of the other options as additional support.
What are the types of materials used in constructing a Retaining Wall?
There are many types of materials that can be used in the construction of the retaining wall. Common retaining walls are constructed of concrete, while other materials include railroad ties or treated timbers, as well as wall stones, natural stones, bricks, and concrete blocks. While wood is an inexpensive option, it has the shortest lifespan because of its susceptibility to decompose.
Stones, rocks, and boulders on the other hand can help to create an aesthetically pleasing retaining wall, with a slightly higher budget and some maintenance to prevent erosion. Masonry blocks provide a maintenance-free alternative and generally have a variety of sizing and color options.
How to Determining if you Need an Engineer?
There are several factors to consider when determining if you should hire a licensed engineer for the construction of the retaining wall. The first is the height of the wall, as most municipalities require a permit and design plan from a structural engineer if the wall measures over four feet high. Terraced walls require the design and permitting of an engineer as well.
Here’s what you can expect during a permit process.
It is important to consider if there will be a slope at the top of the retaining wall. In the state of California, an engineer will be mandatory if the slope at the top of the wall is 2:1. The engineer can help to evaluate the surcharge placed on the retaining wall and design accordingly. Additionally, if the soil is being excavated or moved, a civil engineer may be needed to provide a grading plan and ensure proper drainage.
Is a Permit Necessary?
If you are considering having a retaining wall built on your property, you’re probably wondering if you will need to file for a permit. As a general rule when remodeling your home or property, a permit is usually required when additions, alterations, or new construction is involved. Most important, when building a retaining wall is to determine if an engineering plan is needed for the project.
However, there are times when property owners can take action without the process of obtaining a permit. You should check with your local jurisdiction to see what their stipulations may be. Either way, it is always good to have an engineer involved to help advise on the structure of the wall.
The exact type of permit required for a retaining wall depends on the scope and scale of the wall, the zoning rules, regulations, and codes of the city you live in, environmental impacts, and the type of structure that is being built. The codes and regulations established in your municipality will determine if the project requires a construction permit and what type will need to be filed. Most cities have specific zoning laws about the size and length of the wall based on the size of the home and property lines. Utilizing a licensed engineer will ensure the codes of your local jurisdiction are researched and followed prior to drawing the plans for your retaining wall.
Specific to building a retaining wall, there are several key features property owners should note, that will almost always require permitting:
· If the total height of the wall exceeds four feet measured from the bottom of the footing to the top of the retaining wall
· If there is any back slope adjacent to the retaining wall
· If surcharge load conditions exist (buildings, roads, vehicle loads, or sloped conditions)
· If solid fences are attached or adjacent to the proposed retaining wall
At Design Everest we are experts when it comes to engineering and permitting services for your retaining wall needs. Want to learn more? Contact us today to learn more about retaining wall installation and our services in your area.