Gabion Retaining Wall Installation: Gabion Basket Assembly Guide

Which gabion you are building

Most walls are woven double-twist steel wire, welded steel panels, or polypropylene composite mesh. Woven wire is the hydraulic habit. Welded panels are stiffer and show up in landscape walls. Polypropylene mesh is the non-metallic cage, used where the steel-wire rust path is the problem.

Read the connection for the one you have before you start. The steps below are shared. The callouts say where the polymer basket is different. A fuller note on that joint is the polypropylene assembly page.

Foundation and setting out

Excavate to the formation on the drawing. Take out soft soil, roots and anything sharp enough to bear on one rib or one wire. Compact what the specification calls for. If the ground is not the ground the design assumed, stop and ask. Do not 'make it up' with an extra gabion basket.

Set the line, the base width and the batter from the drawing. A batter leaning into the fill is common. The slope is not 1:6 or 1:10 unless the drawing says so. If a geotextile is shown under the wall and up the back, lay it before the baskets cover it. The mesh is not the filter.

Send surface water away from the crest. A wall that collects the hillside into its backfill is a drainage failure waiting for the first wet week.

Assemble the gabion baskets

Open the panels on clean ground. Fold on the folds provided. For steel wire, lace or clip the way that basket's sheet says, along the joint. For polypropylene composite mesh, use the polymer strips. Do not use steel ties. They can cut the ribs.

Square the box before you commit the base. Fit diaphragms where the drawing shows them. A one-metre spacing is often drawn on long units. If it is not drawn, ask, do not invent it. Keep polypropylene panels off sharp aggregate and off rebar while you drag them. Check steel wire for coating damage at cuts before the basket goes into the wall.

Place the courses

Set the first course to the line and to level before you fill it. Connect baskets to their neighbours along the shared face, not with a tie at each corner and a gap between. The wall is meant to act as one mass. A row of loose boxes will not.

Step the courses to the batter on the drawing. Do not copy a setback in millimetres from this page. Overturning is checked by the designer, not by an installation habit.

Stone, bracing and the lid

Use hard, sound stone that cannot pass the mesh opening. For the polypropylene mesh, the nominal opening is 65 ± 3 mm, so the stone has to be comfortably larger than that. A trial basket is the check. Angular stone packs better than rounded gravel. Do not quote a single 80 to 250 mm range as if every wall used it.

Fill in layers. Do not drop rock from a height that cuts the mesh or knocks coating off the wire. Keep the stone even across the cell. Fit braces as the filling rises, where the drawing shows them, rather than after the face has bulged. Hand-place the visible face. Leave the top so the lid shuts flat. A lid that sits on a mound of stone will not connect to the next course.

Close every edge of the lid. Connect the new course to the one below before you fill it. On the top course, decide how surface water is kept out of the backfill. A capping detail is a drawing item, not an afterthought.

Drainage behind the wall

The stone in the gabion is open. The soil behind it is not. Water that cannot leave pushes the wall. A geotextile or a graded filter on the back face is what stops silt filling the voids. Choose it for the soil, not from a garden-fabric roll.

A collector at the heel, and a ditch above the crest, are there when the drawing says the water needs them. The longer drainage note is separate. Changing from steel wire to polypropylene mesh does not delete either of them.

Where polypropylene differs from steel wire

Empty polypropylene panels are lighter to carry than a steel gabion box of the same size. That helps on a bank. Ask for the empty weight if the crew is planning the lift. Do not turn it into a claimed saving on labour.

The joint is strips, not lacing wire. The rib cuts if you drag it on steel. The wire loses coating if you cut it and leave the end bare. Polypropylene has no steel-wire rust mechanism, which is why it is used on wet walls. It does not like a flame or a hot exhaust during storage. And it is newer in many specifications, so confirm the approval before you substitute it on a wall that was drawn as galvanized wire.

Before you backfill

• Formation, bearing and the filter are in place and continuous.
• Basket-to-basket connections run along the joint, not as spots.
• Diaphragms and braces match the drawing.
• Stone suits the opening. No soil or rubbish in the fill.
• Batter and step match the drawing at each course.
• Lids are closed on all edges.
• Cut mesh and broken joints are repaired or the panel is rejected.
• Line and level are written down before the backfill hides them.