Fences and railings are a common sight around retaining walls. At Allan Block we are frequently asked how to properly install various types of fencing along the top of our walls. This question has a variety of answers depending on the fence application. The best way to address installation of a fence is to consider the plan, design, and construction of the fence and wall structure together as one system before the project begins.
Usually what happens is that the fence or railing is overlooked and not discussed until the wall is completed. For anybody that has been associated with projects like this, they know that installing a railing after the wall is constructed is more work and more expensive.
All fences have the ability to withstand some type of load. A typical fence has the capacity to withstand loads from wind, pedestrians, or even vehicles in the case of commercial projects. By installing a fence or railing above the wall you are adding a requirement for the wall to withstand the additional overturning force in the top courses when somebody or something is pushing on the railing.
If the wall has not been properly designed and built, this creates a potential that the load from the fence footing could move, bulge, or even worse, topple the top portion of the wall. The key is to consider the fence during the design phase of the wall project to ensure the retaining wall has an adequate amount of resistance to the additional force that the fence will apply.
More discussion regarding fence installation above a wall and its design impact can be found here.