Introduction

Retaining walls are a popular landscaping feature that can be used to create terraced gardens, level off sloping yards, and even add curb appeal to your property. However, when it comes to safety, it is important to consider the addition of a fence or guardrail on top of the retaining wall. Fences and guardrails provide added protection to prevent falls and accidents. In this article, we will discuss the guidelines for when a fence or guardrail is required on top of a retaining wall and how to install it so that it does not negatively affect the retaining wall.

Regulatory Requirements

The International Residential Code (IRC) and International Building Code (IBC) provide guidelines for when a fence or guardrail is required on top of a retaining wall. According to the codes, a fence or guardrail is required on top of a retaining wall if the wall is over 30 inches in height measured from the bottom of the footing to the top of the wall.

OSHA Requirements

The Occupational Safety and Health Administration (OSHA) requires that employers provide fall protection for employees working at heights over 4 feet. This includes the top of retaining walls over 4 feet in height.

Manufacturer Guidance

It is also important to consult with the manufacturer of the retaining wall for their specific guidelines and recommendations for fences and guardrails. They may have additional requirements or recommendations that differ from the IRC and IBC.

Installing Fences and Guardrails – Poured Concrete Walls

When installing a fence or guardrail on top of a retaining wall, it is important to ensure that the installation does not negatively affect the structural integrity of the wall. The National Concrete Masonry Association (NCMA) recommends the following guidelines for fence and guardrail installation:

Anchoring

The fence or guardrail should be anchored to the retaining wall using approved anchor systems* that are designed for the specific type of wall and fence or guardrail. The anchors should be placed in the top of the wall and spaced at maximum 6 feet apart.

Load Distribution

The load of the fence or guardrail should be distributed evenly across the top of the wall to prevent concentrated loads that can cause damage to the wall.

Allow for Expansion and Contraction

The fence or guardrail should be designed to allow for expansion and contraction of the wall due to changes in temperature and moisture. This can be achieved by using expansion joints or flexible connections between the fence or guardrail and the wall.

Material Compatibility

The fence or guardrail should be made of materials that are compatible with the retaining wall. For example, a metal fence or guardrail should not be allowed to contact the rebar within a retaining wall as the metal contact may cause corrosion.

Proper Drainage

Proper drainage should be maintained around the fence or guardrail to prevent water from penetrating the wall and causing damage. Drainage channels or weep holes should be incorporated into the design to allow water to flow away from the wall.

Segmental Retaining Wall (SRW) Considerations

Segmental Retaining Walls (SRWs) have specific requirements for fences and guardrails that differ from other types of retaining walls. The following are the guidelines for installing fences and guardrails on SRWs:

Fence Post Placement

When installing a fence on top of an SRW, the fence posts should be placed at least 3 feet behind the wall. This is to ensure that the fence posts do not interfere with the structural integrity of the wall and its drainage system.

sonotubes for fence posts behind retaining wall
Use sonotubes* when installing fence posts with geogrid reinforced SRW walls to avoid damaging the geogrid.

Sleeve-it System

Another option for installing a fence on top of an SRW is to use the Sleeve-it system*. This system uses sleeves that are placed in the wall during construction to allow the fence posts to be inserted after the wall is built. This system allows the fence posts to be placed closer to the wall without interfering with the structural integrity and drainage of the wall.

Sleeve-it System
Sleeve-it System* in wall
Sleeve-it System
Sleeve-it System* dimensions

Concrete Slab

A concrete slab can also be added on top of the SRW to support the fence or guardrail. The slab should be designed and constructed to ensure proper load distribution and drainage. Additionally, it should be anchored to the wall to prevent shifting and movement. It is important to consult with the manufacturer of the SRW system for their specific recommendations and guidelines for the slab installation.

SRW blocks are not heavy enough by themselves to hold up a fence. Installing concrete and rebar to create a larger block like the detail above can allow for a fence to be installed on top of an SRW block. Contact an engineer for the concrete*, rebar*, and fence design with your SRW block and fence project.

It is important to note that these guidelines are for SRW retaining walls. If you are installing a fence or guardrail on other types of retaining walls, it is recommended to follow the guidelines discussed in the previous sections of this article and consult with a professional engineer to ensure proper design and installation.

Conclusion

Retaining walls require proper drainage, regulatory requirements and manufacturer guidance when installing a fence or guardrail on top of the wall. It is important to follow these guidelines to ensure that the fence or guardrail does not negatively affect the structural integrity of the wall. By following these guidelines, you can ensure that your retaining wall is safe and secure while providing the desired function. Consult with a professional engineer to ensure the correct design and installation of a fence or guardrail for your specific retaining wall project.

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