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Compaction and settling

That's why you order 15–30 % extra — and avoid hollows

2026-06-14·4 min reading

Loose soil and gravel settle when compacted. Here's how to account for settlement and compaction in your order, and why it prevents low spots and later damage.

Introduction

When a layer of gravel or topsoil is laid loose and then compacted with a plate compactor or roller, it takes up less space than the loose material. If you order only the finished, compacted volume, you will end up short of material.

Loose goods(what you order)vibrates/drumCompressed(finished layer)sentence15–30 %order additional: gravel 15–35% · topsoil 20–30% (advisory)
Fig. Loose material takes up more space than the compacted layer — the difference (settlement) is the extra amount that must be ordered.

Factors (indicative)

  • 01Stabilised gravel for the sub-base: order about 15–35 % extra to allow for compaction.
  • 02Loose topsoil: can settle 20–30 %, so order correspondingly extra.
  • 03Density for conversion to tonnes: crushed-stone base/sand/aggregate approx. 1.5–1.6 t/m³.

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