GLAREUM.NET›Chapter 9›Garden walls and gabions

9.2 Choosing gabion fill stone

What to put in the baskets: stone size against the mesh, crushed or rounded, and how to tell good stone from stone that will crumble.

Two gabion faces side by side: on the left crushed, angular stone that packs tight; on the right rounded field stone. Both are larger than the 75 mm mesh. Crushed packs tight, locks Rounded softer look 75 mm mesh stone 100–200 mm
The same basket filled two ways.

At a glance

Difficulty
1 of 4
Time
An hour to choose and check the stone
Tools
Tape measure, a few sample stones, hammer, bucket of water
Parts
  1. 1  Face stones, hand-picked
  2. 2  Core stones
  3. 3  Mesh

What you need per m³ of basket

MaterialSizeTypeAmount
Fill stone 100–200 mm Crushed or rounded, hard, frost-proof, clean 1.7–1.8 t
or 75–150 mm For thin baskets up to 150 mm and mesh under 75 mm
Extra for the top – Overfill, so the stone can settle 25–50 mm

Why bigger than the mesh, and crushed or rounded?

100–200 mm

The usual size for 75 mm mesh and baskets 300 mm or thicker. Every stone must be bigger than the openings, or it falls out. One specification asks for the smallest side of each stone to be at least 1.5 × the mesh.

crushed · rounded

Crushed stone has flat faces that lock together, so the basket stays square and bulges less. Councils ask for it in retaining walls. Rounded field stone is allowed in US federal specifications and looks softer. Use crushed stone where the wall holds back soil.

Step by step

  1. 1

    Measure the mesh opening.

    The specifications use welded mesh of 75 × 75 mm; garden baskets vary, so measure yours. On rectangular mesh, use the short side. The smallest stone you order must be bigger than this, better 1.5 × bigger.

    A small stone slipping through the mesh
  2. 2

    Pick the size for the basket thickness.

    Baskets 300 mm thick or more: 100–200 mm. Thin baskets of about 150 mm: 75–150 mm, with a smaller mesh. Aim for at least three stones across the basket.

    Stones of different sizes laid out
  3. 3

    Check that the stone is hard and sound.

    Reject stone that is layered, cracked, crumbles at the edges or soaks up water. It will split in frost and the basket will sag. Ask the yard for stone with a frost or weathering test, and keep dirt and fines to a minimum.

    Splitting a test stone
  4. 4

    Choose the face stones by eye.

    The face is all anyone sees. Keep the best-shaped stones, with a flat side, for the visible faces and put the small and odd ones in the middle, never on the face.

    Face stones placed by hand
  5. 5

    Order by weight.

    Multiply the basket volume by 1.7–1.8 t/m³. A 1 × 1 × 0.5 m basket is 0.5 m³ and takes about 0.9 t. Add a little for overfilling and for picking face stones.

    A load of gabion stone delivered
Specifications
BasketMeshFill stoneSource
Thin, about 150 mmsmall75–150 mmAnne Arundel County
230–450 mm≤ 100 mm100–175 mmAnne Arundel County
300–900 mm75 × 75 mm welded100–200 mmNRCS, Iowa DOT, Hertfordshire
500 mm and over–100–200 mmUFGS
Gabions in general≤ 75 × 75 mm100–250 mmAustralian councils

Size and mesh

Every stone bigger than the mesh opening (UFGS, Kansas DOT). Newfoundland and Labrador asks for the smallest dimension of each stone to be at least 1.5 × the mesh and the largest at most 300 mm. UFGS allows up to 5 % oversize or undersize stone; undersize stone goes inside, never on the face, and oversize stone must still leave room for three or more layers per compartment.

Quality

Hard, dense and durable; free of cracks, layers and weathering; does not break down in water, weather or frost. US federal specifications call for freeze-thaw testing; Iowa tests freeze loss and abrasion. At most 5 % dirt, sand, clay and fines (UFGS). Australian councils ask for at least two broken faces. One Canadian city rules out limestone in its park walls; check local practice for your stone.

Shape

UFGS accepts angular to round stone. Retaining wall specifications from councils ask for angular stone or a degree of angularity.

Weight

A filled gabion weighs about 1.7–1.8 t/m³ (FHWA design values of 105 and 110 lb/ft³), so the stone for one cubic meter of basket weighs the same.

Sources

  1. US Department of Defense, UFGS 31 36 00 Gabions: rock 100–200 mm for gabions 500 mm and taller, large enough not to pass the mesh; at most 5 % oversize or undersize, undersize only inside, never on the face; room for three or more layers of rock per compartment; hard, angular to round, durable rock that does not break down in water or weather, with freeze-thaw testing; at most 5 % dirt, sand, clay and fines; 300 mm lifts, no cell more than 300 mm higher than its neighbour; stiffeners at ⅓ and ⅔ of the height; hand-placed visible faces; drop height at most 0.9–1.2 m; overfill 25–50 mm; no foundation work on frozen ground
  2. USDA NRCS Construction Specification 464, Wire mesh gabions and mattresses: baskets 300–900 mm thick: rock 100–200 mm, at least 85 % in that range; welded mesh 75 × 75 mm, woven 83 × 114 mm; no cell more than 300 mm deeper than its neighbour; two crossties per 300 mm of depth in cells over 450 mm tall; welded baskets braced across the corners 300 mm from each corner; outer stones placed by hand; last layer level with the top edges; no crowbars to close lids; foundation free of mounds and dips
  3. Iowa DOT §4130, Gabion stone: stone 100–200 mm (4–8 in) for gabions, 75–125 mm (3–5 in) for mattresses; tested for freeze-thaw loss and abrasion
  4. Newfoundland and Labrador Transportation and Infrastructure, Specification 601 Gabions: the least dimension of every stone at least 1.5 × the mesh size; the greatest dimension at most 300 mm; at least two layers of overlapping stone; clean, hard and durable stone; exposed stones hand-picked to keep voids small
  5. Kansas DOT Standard Specifications §1711, Gabions: mesh openings smaller than the gabion rock
  6. Anne Arundel County (Maryland), Section 02294 Gabions: stone by basket thickness: 150 mm baskets 75–150 mm, 230–450 mm baskets 100–175 mm, 900 mm baskets 100–300 mm; mesh opening at most 100 mm; hard, angular, weather-resistant stone; at least two courses; drop height at most 0.9 m; subgrade smooth and firm
  7. Hertfordshire County Council, standard drawing HST-0600-001 Typical gabion retaining walls: fill graded 100–200 mm; welded mesh 75 × 75 mm; retained height 350–550 mm with one 1.0 × 1.0 m gabion, up to 1.5 m with a 1.5 m wide gabion under a 1.0 m one; gabions buried 300–500 mm; face batter 6°; foundation of compacted well-graded granular fill or concrete, at least 50 mm wider than the basket on each side; bracing wires after ⅓ and ⅔ of the height, end units braced both ways; no compartment more than 300 mm higher than its neighbour; exposed faces hand packed; vertical joints staggered; slight overfill where gabions are stacked; geotextile behind the gabions and on all buried faces
  8. Wyndham City Council (Victoria), Technical Specification 715 Gabions and rock mattresses: gabion rock 100–250 mm with at least two broken faces, free of laminations and cracks; welded mesh at most 75 × 75 mm; braces at about 330 mm after filling ⅓ and ⅔; refill where bulges exceed 50 mm; perforated drain pipe at least 100 mm at the base of the rear of a gabion retaining wall
  9. Cessnock City Council (NSW), AUS-SPEC 0294 Gabion walls and rock filled mattresses: rock sized for at least three layers in a gabion; 1 m gabions filled in three layers with bracing after the first and second; 500 mm gabions in two layers of 250 mm; bracing wires at 330 mm; exposed faces placed by hand; overfill 25–50 mm; prepared foundation sloping at most 1 in 10; geotextile between gabions and retained soil; heavy plant kept 1 m from the units
  10. South Australia Department for Infrastructure and Transport, Master Specification ST-RE-C3 Gabions: gabion rock 100–250 mm with a range of sizes and some angularity; backfill in loose layers of at most 200 mm; only hand-operated plate compactors within 1 m of the back of the gabions
  11. FHWA Federal Lands, standard drawing E253-01 Gabion retaining wall: rock-filled gabions weigh 110 lb/ft³ (about 1.75 t/m³); front face battered 1:12; underdrain at the back with outlets
  12. FHWA Federal Lands, standard drawing W253-3: filled gabions weigh 105 lb/ft³ (17.6 kN/m³, about 1.7 t/m³)
  13. City of Winnipeg, park landscape detail drawing L6 (tender 475-2016): freestanding park wall of 2.0 × 0.5 × 1.0 m baskets with 75 mm mesh, top 600 mm above ground; fill 100–200 mm field stone, no limestone; 200 mm of compacted 0–19 mm crushed base on non-woven geotextile; gabion seat of 0.5 × 0.5 m baskets on the same base with a timber top bolted to a steel plate; playground baskets set 50 mm below ground
  14. Tennessee Erosion and Sediment Control Handbook, Gabions: clean 100–200 mm stone without fines, sized to stay in the baskets, preferably placed by hand; geotextile behind all gabion structures; gabions keyed into the foundation

Amounts: a filled gabion weighs 105–110 lb/ft³ in the FHWA drawings, about 1.7–1.8 t/m³, so 1 m³ of basket takes 1.7–1.8 t of stone. Order a little extra for picking face stones and overfilling.

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