Pier and grade beam foundations are commonly used for homes built on challenging terrain or areas with poor soil stability. This foundation type involves drilled piers that extend deep into stable soil layers, connected by grade beams, which provide structural support and distribute loads. However, voids can sometimes form beneath these grade beams, especially in hillside settings. While these voids are generally not a structural concern, managing them can prevent excessive erosion and maintain the foundation’s longevity.

Grade beams in pier and grade beam foundations do not need to rest directly on the ground. In fact, they are intentionally designed to span between piers without requiring direct soil support. This allows the foundation to remain stable even if the soil below shifts slightly. Over time, minor erosion or soil movement beneath the beams may create visible gaps, or voids, between the beams and the ground surface. These voids are typical and usually harmless, but on a hillside or in areas prone to erosion, they can grow larger and create additional maintenance needs.

For minor voids, a straightforward solution is to periodically fill them with soil or an expanding foam material. Expanding foam is especially useful because it fills the void tightly and is resistant to erosion. This maintenance task helps limit excessive soil movement and discourages water accumulation around the beams, protecting the foundation from erosion effects over time. Soil compaction is also important to ensure the fill material doesn’t wash away too quickly, providing a more durable solution.

On a hillside, erosion can be more severe, so building a small retaining wall to create a terrace can help limit soil movement and prevent future void formation under grade beams. A retaining wall stabilizes the soil by creating level areas, reducing the downward pressure and flow of soil caused by gravity. While this approach requires more upfront investment, it’s effective for hillside properties where erosion is a persistent issue. Retaining walls also help to redirect water away from the foundation, providing further protection against moisture-related erosion.

Regular inspections of the area beneath grade beams can help detect any significant changes in the size of voids. If you notice the gaps widening over time, it may be time to refill the voids or consider erosion control options. Water management is another critical factor: keeping water away from grade beams by ensuring proper drainage and avoiding excessive runoff near the foundation will reduce erosion risk. If you’re unsure about the severity of voids or soil movement, consulting with a foundation specialist can provide guidance on the best maintenance approach.

Voids beneath grade beams in a pier and grade beam foundation are common and usually not a cause for concern. However, managing them with periodic refilling or, on hillsides, installing a retaining wall can help maintain foundation stability and minimize erosion. By proactively addressing minor erosion, homeowners can protect their foundation, avoid costly repairs, and ensure the long-term stability of their structure.