Drainage done right: 20mm gravel, sand layers and smart garden design

Drainage done right: 20mm gravel, sand layers and smart garden design

Drainage done right: 20 mm gravel, sand layers and smart garden design for heavy rain

When the wet sets in on the Fraser Coast, good drainage keeps paths firm, plant roots healthy and the house surrounds dry. A few smart material choices handle the big downpours without turning your yard into soup.

This guide walks through where 20 mm drainage gravel shines, when a sand layer helps, and how to pair decorative stones with planting for better runoff and good looks. We include a simple French drain you can build in a weekend, easy downpipe dispersal tips and a quick checklist to diagnose soggy spots.

Why 20 mm drainage gravel is a backyard essential

Twenty millimetre drainage gravel offers void space that lets water move quickly. It resists compaction, making it ideal for:

  • Trench and edge drains beside paths, driveways and garden beds
  • Around footings and along slab edges to discourage ponding
  • Behind retaining walls to relieve hydrostatic pressure
  • Under and around downpipe outlets to spread flow before it hits soil

Decorative pebbles suit visible areas where appearance matters. Think dry creek beds, mulch-alternative top dress, and courtyard borders.

Do you need a sand layer beneath drainage gravel?

A sand layer is useful for levelling, but it is not a drainage layer. Keep it thin (10–20 mm) and protect it with geofabric. In pure drainage trenches, skip sand and go straight to fabric and gravel to maximise water flow.

A simple French drain you can build

  1. Plan the route toward a lawful discharge point. Aim for 1–2% fall.
  2. Dig a trench 300 mm wide and 400–600 mm deep.
  3. Line with geofabric, overlapping the sides.
  4. Spread 100 mm of 20 mm drainage gravel, lay slotted drain pipe (perforations down), backfill with gravel to 100 mm below surface.
  5. Fold fabric closed, cap with soil, turf, or a decorative pebble layer.

Materials that stop paths turning to mud

  • A-grade Road Base, compacted in layers, builds a dense platform that resists rutting.
  • Crusher Dust tightens soft spots and creates a smooth, compacted surface for pavers.

Quick checklist to diagnose soggy spots

  • Mark standing water 30 minutes after rain stops.
  • Probe 150–300 mm down — if clay is close, you need surface collection and a positive outfall.
  • Watch flow paths. Dirty streaks trace natural runoff lines for swales or French drains.
  • Check downpipes — add a gravel splash pad and pipe to a dispersion trench if needed.

Local know-how and delivery

We deliver bulk drainage gravel, sands, A-grade Road Base and Crusher Dust across Howard, Hervey Bay and Maryborough.

FAQ

Do I use 20 mm drainage gravel or decorative pebbles? Choose drainage gravel for trenches, behind retaining walls, around footings. Use decorative pebbles in visible beds and borders.

How do I design a basic French drain? 300 mm wide trench, geofabric, 100 mm gravel, slotted pipe perforations down, backfill, fold fabric, cap with soil or pebbles.

What stops paths turning to mud? Compact A-grade Road Base or Crusher Dust in layers. Add pavers or a decorative pebble topping over separator fabric.

Wrap-up

Use 20 mm drainage gravel where flow matters, keep sand as a levelling aid, stabilise paths with Crusher Dust and A-grade Road Base, and finish visible zones with attractive pebbles. Get in touch with Burrum Landscape Supplies for volume estimates and delivery planning.

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