Gabion and retaining walls in Bali

A gabion wall is a gravity structure — coated mesh baskets filled with hand-packed rock, stacked and stepped, tied to one another and set on a prepared base. Water passes straight through, so hydrostatic pressure never accumulates. The wall flexes slightly with ground movement instead of cracking, roots knit into it over a couple of seasons, and it reads as part of a hillside above a river rather than as a bunker facing your garden.

Mesh specification is the line nobody reads on a quote and the one that sets the lifespan. Ordinary galvanised wire in Bali's humidity — and in salt air anywhere near the coast — is a fifteen-year proposition at best. Galfan-coated wire moves that considerably further, and Galfan under a PVC sleeve is what river banks and beachfront work deserve. We put wire grade, diameter and coating on the quotation, because two gabion walls at different prices are usually two different walls.

Why retaining walls fail in the rainy season

Saturated soil is heavier and pushes harder. During a Bali downpour the water entering ground behind a wall has to go somewhere, and where the drainage layer is missing, clogged or was never built, pressure rises against the back face until something gives. The sequence is visible all over the island every February: a bulge in the middle of a rendered wall, a crack stepping up from the toe, then a leaning section with soil spilling out at its base.

Three details prevent it. A free-draining zone behind the wall, wrapped in geotextile so fine soil cannot wash into the voids and block them. Weep holes or a perforated collector pipe with a genuine outfall, rather than a pipe that ends in the same soil it is meant to drain. And surface water intercepted above the wall so runoff never reaches the backfill in the first place. Gabions deliver the first two by their own construction, which is why they suit this climate so well.

Gabions or concrete — choosing honestly

Gabions win on drainage, flexibility and appearance, and they need no formwork, no curing period and no crane. They suit slope stabilisation, garden terracing, river banks and any wall where a slightly battered, stepped profile is acceptable. Their limits are geometry and land: a gravity wall needs depth as it gains height, roughly half its height at the base, so a tall gabion structure eats ground you may have wanted to build on.

An engineered reinforced concrete wall holds the vertical line where space is tight, carries surcharge from a building or driveway above, and can be tied back where geometry turns difficult. It costs more per square metre of face, needs a designed footing and its own drainage system behind it, and it has to be calculated by an engineer rather than copied from the neighbour's job. On steep plots we regularly use both: concrete where the building sits close, gabions wherever the slope simply needs holding.