A gabion wall is a row of wire or woven baskets filled with rock in place, and its build rate is set by the mesh and the lifting, not by skill. A wall 10 m long, 1 m high and 1 m thick needs about 51 m² of mesh and roughly 17 tonnes of rock, so one day for 4 people is possible only if the mesh is already made and the rock is stacked beside the line. The wire rusts, and wire cutters open a basket.
Gabions are cages of wire mesh or woven branches filled with rock or rubble and stacked into walls and banks that are fast to build and flex with the ground.
Gabions Are Fast Only If The Cages Exist
The parent article calls gabions among the fastest wall types and says a team of 4 can build 10 m of gabion wall, 1 m high, in a day if the materials are nearby. The figure is unsourced. The arithmetic below shows what it assumes.
Inputs: a wall 10 m long, 1 m high and 1 m thick, built from baskets 1 m x 1 m x 1 m (the parent article’s typical size). Rock of 2,600 kg/m³ solid with 35% voids when packed (the figures used in Gabion Walls). Steel wire in a 10 cm x 10 cm grid, 2 to 3 mm in diameter, as in that article.
Worked Example: What The Day’s Work Contains
Mesh. The wall is a single long box 10 m x 1 m x 1 m divided into 10 baskets by 9 internal diaphragms:
- Top and bottom: 2 x 10 x 1 = 20 m².
- Front and back: 2 x 10 x 1 = 20 m².
- Two ends: 2 x 1 x 1 = 2 m².
- Nine diaphragms: 9 x 1 x 1 = 9 m².
- Total: 20 + 20 + 2 + 9 = 51 m².
Wire. A grid at 10 cm spacing has 10 wires per metre in each direction, so 20 m of wire per square metre of mesh: 51 x 20 = 1,020 m, without allowing for twists, laps and tie wire. Wire of 2 mm has a cross-section of π x 0.001² = 3.14 x 10⁻⁶ m², and at the textbook density of steel (about 7,850 kg/m³) weighs 0.0247 kg per metre; 3 mm weighs 0.0555 kg per metre. So the mesh is about 1,020 x 0.0247 = 25 kg to 1,020 x 0.0555 = 57 kg of wire. That is a small mass but a very large amount of drawn wire; see Iron Wire for how slow it is to make by hand. Salvaged welded mesh, chain-link or reinforcing mesh is the realistic source.
Rock. Fill is 0.65 x 2,600 = 1,690 kg/m³. Ten cubic metres is 10 x 1,690 = 16,900 kg, about 17 tonnes.
Lifting. Among 4 people that is 16,900 / 4 = 4,225 kg each, about 211 lifts of 20 kg per person. At one lift every two minutes that is 7 hours of lifting by each, with no breaks and no mesh work. A day is therefore the best case: cages ready, rock stacked at the line, stones hand-sized. It is not the usual case.
Method: Build And Fill In Place
Step 1: Level the bed. Compact and grade it, as in Gabion Walls. A basket on a slope slumps.
Step 2: Set the baskets. Place them side by side and tie them together along every edge with tie wire.
Step 3: Fill where they stand. A basket of 1 m³ holds about 1.7 tonnes and cannot be moved once filled. Use rock larger than the mesh opening so it cannot fall through; put the larger stones on the face by hand and pack the middle behind them. Overfill slightly, since the rock settles.
Step 4: Tie and close. Tie across the basket front to back at a few points so the face cannot bulge, fold the lid over and wire it down.
Step 5: Stack by stepping back. Offset each course and set it slightly back from the one below. A stepped wall is stable; a vertical stack of cubes is not.
Woven alternative. Where there is no wire, baskets woven from willow or other flexible branches serve the same purpose for a season or two; they rot faster than wire rusts.
Where It Fails
- Rust. The parent article gives 5 to 15 years because the wire rusts; galvanizing protects it for a time, and acid or salty water attacks it sooner.
- Wire cutters. A gabion face can be opened with bolt cutters. The fill then spills. It is a barrier to those without tools.
- Voids and fragments. The fill is loose stone; if it is struck the stones move and can fragment.
- Protection claims. The parent table rates gabions “good to excellent” ballistically, and Perimeter Defense Design says earth-filled gabions are “effective against small arms”. Neither names a cartridge or range and there are no tests in this corpus. A 1 m basket filled to 1,690 kg/m³ is 1,690 kg/m² of mass, which supports comparing it with earth and stone, not claiming protection.
Cut wire and heavy rock
Cut mesh ends are sharp; wear thick gloves and cover cuts at once, since wounds from rusty wire are a tetanus risk (keep tetanus protection current if you can). Rock slides and crushes hands when loading baskets: lift with a partner, keep fingers out from under stones, and never stand below a stack that is being filled. A filled basket weighs about 1.7 tonnes and cannot be adjusted by hand.
What’s Next
- Learn next: Window and Door Hardening — hardening the openings of an existing building
- Combine with: Riprap — rock sizing and placement on slopes