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Select Proper Drainage Aggregate

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How to Build a Retaining Wall and 6 Reasons they Fail

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What happens here

The type and depth of drainage material used as backfill behind a retaining wall are critical for its long-term stability. Avoid using pea rock or sand as backfill, especially in the drainage zone. Instead, opt for a 'clear rock' material, such as 3/4 inch angular aggregate. This angular material interlocks, creating a stable mass that resists ground movement behind the wall. Unlike rounded pea rock or sand, which can shift and become saturated, angular rock allows water to flow through freely without transferring excessive pressure or movement to the wall's face.

Goal: Ensure effective and stable drainage behind the wall with appropriate aggregate

Tools and materials

  • 3/4 inch Clear Rock — Ideal angular aggregate for backfill in the drainage zone behind retaining walls
  • Pea Rock — Avoid using as backfill due to lack of interlocking properties
  • Sand — Avoid using as backfill due to lack of interlocking properties and potential for saturation

What they say

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of most structural retaining walls. Here's another myth for you. Pock or sand makes great back fill material. Nothing could actually be further from the truth, especially in the drainage zone. You want a dedicated material that is angular in nature, can lock together, and doesn't have a lot of fines in it. The stone of choice I use is 3/4 in clear rock. The reason that's important is because as water flows through it and through the base of the wall, it's not going to move. it can resist all types of ground movement behind the wall and not transfer that into the actual face of the structure. Today we covered six

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