Why Posts Heave Out of the Ground When Installed with Screening and/or Gravel

Welcome back to Digging Deeper with The Post Hole Company! In today's blog, we address a common issue that many homeowners face—fence posts heaving out of the ground. This problem often arises when posts are installed using screening and/or gravel. We'll delve into why this happens, the science behind it, and provide effective solutions to ensure your fence remains sturdy and secure. Read on to learn more about how to prevent post heaving and maintain the integrity of your fencing.

Why Posts Heave Out of the Ground When Installed with Screening and/or Gravel

When it comes to installing fence posts, the choice of materials and methods can significantly impact the longevity and stability of your fence. One common issue homeowners face is post heaving, where the fence posts gradually push out of the ground. This problem is particularly prevalent when posts are installed using screening and/or gravel. In this blog post, we will delve into why this happens and what you can do to prevent it.

Understanding Post Heaving

Post heaving is primarily caused by the freeze-thaw cycle that occurs in colder climates. When the ground freezes, it expands, pushing anything in its way upwards. As the ground thaws, it contracts, but the upward force has already shifted the post. Over time, this repeated cycle can cause the posts to become unstable and eventually heave out of the ground.

The Role of Screening and Gravel

1. Lack of Adhesion: Screening and gravel are often used to provide drainage and prevent water from pooling around the base of the post. However, these materials do not offer sufficient adhesion to hold the post firmly in place. Unlike concrete, which sets around the post and anchors it in the ground, gravel and screening remain loose and can shift during the freeze-thaw cycle.

2. Inadequate Support: Gravel and screening, while good for drainage, do not provide the same level of structural support as concrete. The loose nature of these materials allows for more movement within the hole, making it easier for the post to be pushed out of alignment.

3. Water Accumulation: Although gravel and screening are intended to improve drainage, they can sometimes cause water to accumulate around the post, especially if the soil surrounding the hole is not well-drained. This excess moisture can freeze, exacerbating the freeze-thaw effect and leading to more significant heaving.

Preventing Post Heaving

To prevent post heaving and ensure the longevity of your fence, consider the following tips:

1. Use Concrete: Setting your fence posts in concrete provides a solid anchor that can resist the forces of freezing and thawing ground. Make sure the concrete extends below the frost line to minimize the impact of ground movement.

2. Ensure Proper Installation: When using concrete, ensure that the concrete is evenly distributed around the post and extends deep enough to anchor it securely. Avoid using gravel as a base or for drainage, as it can exacerbate heaving issues.

3. Depth of Installation: Installing posts deeper into the ground can help prevent heaving. Make sure your posts are set at least 3.5 feet deep for fence installations and 4 feet deep for deck footings, as per the minimum requirements in Ontario, Canada.

4. Avoid Gravel Alone: While gravel and screening are sometimes used for drainage, they should not be the sole materials used to set your posts. Relying on concrete alone ensures better stability and reduces the likelihood of post heaving.

Conclusion

Understanding why posts heave out of the ground when installed with screening and gravel can help you make more informed decisions about your fence installation. By using concrete, ensuring proper installation techniques, and setting posts at the correct depth, you can prevent post heaving and enjoy a sturdy, long-lasting fence.