Nothing on the delivery note is the structure
A gabion job arrives as two unrelated deliveries: a pallet of folded mesh panels that two people carry off the tail lift, and twenty or thirty tonnes of quarried rock tipped wherever there is room. Only the second one is the wall. A gabion resists earth pressure the way a dry-stone wall does — by being heavy, and by being wide enough at the base that its mass sits over the toe — and the mesh contributes nothing to that except stopping the mass spreading sideways as it settles.
Getting that the right way round sorts the decisions into two piles that barely touch. Mesh type, wire diameter and coating are a durability question answered against exposure — buried, atmospheric, immersed, salted, abraded by bedload. Stone type, size and density are a structural question answered against retained height and what sits behind the wall. The classic value-engineering mistake here is a PVC-coated basket filled with whatever was loose in the quarry yard: sixty years of container around twenty years of wall.
It also explains a failure mode people do not expect. A gabion built from soft, rounded or undersized fill does not topple. It slumps: the stone works down through itself, the faces belly out between the diaphragms, and the top of the wall drops fifty or eighty millimetres across a couple of winters while the mesh stays perfectly intact. Whoever inspects it finds nothing wrong with the baskets, because nothing is wrong with the baskets.
Basket size, mesh type, and the aperture that fixes your stone
Standard baskets are a metre deep and either a metre or half a metre high, in run lengths of one, one and a half, two, three and four metres, with internal diaphragms every metre so no panel spans more than a metre unsupported. That grid is why a run length is worth settling before the setting-out pegs go in: a wall finishing at 7.4 m takes either a cut basket or a redesigned end. Mattresses are the flat relatives — a couple of hundred millimetres thick, two metres wide, three to six long — meant for facing a slope or lining a channel bed rather than for retaining anything.
Depth is the one genuinely structural dimension, because the depth of the bottom course is the wall's base width. Manufacturer design charts for stepped gravity gabions commonly open near half to two thirds of the exposed height and then check it; the check is what you build to, not the opening figure. Everything above is the same depth or stepped back, and a stepped face is normally cheaper because the upper courses do less work.
Mesh comes in two families and they are not interchangeable. Double-twisted hexagonal mesh is built so a cut or corroded wire cannot unravel the fabric — that is the entire point of the double twist — and it deforms with the fill rather than fighting it, which is what you want wherever settlement is expected; it is specified against ASTM A975 or BS EN 10223-3. Welded mesh panels give the flat, sharp-edged face specified for boundary and architectural work and are stiffer, but a broken wire opens a hole that grows; those go against ASTM A974 or BS EN 10223-8.
Whichever family you pick, the mesh aperture sets the fill gradation and not the other way round. Manufacturer installation literature for basket systems generally puts fill between the aperture dimension and roughly twice it, with nothing in the load smaller than the smallest opening — because anything that can pass through the mesh eventually does, usually at the base of the face where nobody looks. That single line eliminates most of what a builders' merchant will offer you, and it is worth taking the aperture to the quarry rather than taking the quarry's gradation to the wall.
Durability of the rock is a separate question from its size, and the one that gets skipped. Sound, angular, low-absorption material is tested under ASTM C88 for soundness and ASTM C535 for abrasion, with BS EN 13383-1 covering armourstone where the work is hydraulic. A quarry that can produce a sheet against those can also give you the particle density, which is the number everything below runs on.
| System | Where it belongs | Written against |
|---|---|---|
| Double-twisted hexagonal basket | Retaining work and anywhere settlement is expected; a cut wire will not unravel the fabric | ASTM A975 or BS EN 10223-3 |
| Welded mesh panel basket | Flat architectural faces, boundary features and short walls on firm ground | ASTM A974 or BS EN 10223-8 |
| Gabion mattress | Slope facing, channel beds and launching aprons — not for retaining height | Same mesh standards; thickness comes from the hydraulic design |
| Wire coating class | Chosen against immersion, salt spray and abrasion, never against price | ASTM A641 or ASTM A856 for the wire coating |
| Fill gradation | Between the mesh aperture and roughly twice it, nothing smaller | Quarry gradation sheet, with durability from ASTM C88 and ASTM C535 |
Bulk density, voids, and the tonne you actually order
There are two densities in play here and confusing them is worth about forty percent. The first is the particle density of the rock — the figure a quarry gets from ASTM C127 or its European equivalent, near 2,600 to 2,700 kg per cubic metre for sound limestone, granite or basalt. The second is the placed bulk density inside the basket, that figure less the voids between the stones, and it is the only one with anything to do with your order or the wall's weight.
How big the voids are is a workmanship variable, not a material constant. Stone hand-placed along the face with graded hearting worked in behind it settles to something near thirty percent voids; the same stone tipped from a bucket and raked level runs to forty or more, because uniform angular rock dumped loose bridges against itself. On rock at 2,650 kg per cubic metre that spread puts the placed bulk density roughly between 1,550 and 1,850, and both the order and the stability check come off wherever you land in it.
The arithmetic from there is short. A one-metre cube of basket holds a cubic metre of gross volume however it is packed, so the tonnage per basket is the placed bulk density expressed in tonnes — around 1.7 for well-packed sound rock, which makes thirty baskets fifty tonnes and change. Face area times basket depth gives the gross volume, the density turns it into an order, and a modest allowance covers the overfill each lid closes onto. Do not add more than that: oversize goes into the hearting and undersize should never have been on the lorry.
The trap in the other direction is worth naming. Because the tonnage is fixed by how tightly the crew packs, a crew that dumps rather than packs uses less stone than the estimate and leaves site with material spare — which reads on the day as a good result and is in fact a lighter wall than the one that was checked. Reconciling delivered tonnes against baskets filled, course by course, is the cheapest quality check available on a gabion job.
Choose the basket your supplier sells and the voids your crew will actually leave. The count comes out in whole baskets, course by course, and the stone comes off the solid rock less those voids — so the density it asks for is the particle density, not a bulk figure that has the voids in it already.
The length of the wall along its face.
The height of the whole stack of baskets, including a bottom course set below ground.
How deep the wall is from its front face to its back, at the base.
The basket your supplier sells, in the sizes of the measurement system you have chosen.
The share of a filled basket that is air between the stones.
The density of solid rock — not the loose bulk density on a delivery ticket.
Extra stone for overfilling each basket before its lid closes, and for what stays in the heap.
Gabion baskets to order
3 baskets (6 × 3 × 3 ft)
The basket count is exact for the wall and basket entered. The stone is the solid stone less the voids between the stones, so it moves with how the baskets are filled: a hand-packed face leaves fewer voids than stone tipped in by machine.
- Baskets along the wall, in each course
- 3 baskets
- Courses up the wall
- 1 course
- Rows through the wall, front to back
- 1 row
- Stone to order, with the overfill allowance
- 9.15 tons
- Stone that fills the baskets
- 8.71 tons
- Volume of the filled baskets
- 6 yd³
- Density of a filled basket — the stone and its voids together
- 107.53 pcf
They open the calculator with your figures already in it
Gabion Basket and Stone Calculator: 3 baskets (6 × 3 × 3 ft) — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
Estimated cost — your price
This site holds no price list for this material — local prices vary too much to publish honestly. Enter your supplier's price and the result is costed with it.
What this calculation does not cover
- A QUANTITY, NOT A DESIGN. A gabion wall holding back earth is a gravity wall: whether it slides, tips or overloads the ground under it depends on its base depth, its batter, the soil behind it and any slope, drive or building above it — none of which appears here. Get a wall retaining more than about 1 m (3 ft) of earth designed, and check what your local authority requires, which can be less where there is a load above.
- Every basket is counted whole, lengthways along the wall, with one depth from base to top. A wall that steps back as it rises — as most gravity walls do — is counted by entering each course as its own wall one basket high and adding the results; baskets turned across the wall as headers are not modelled.
- The stone rests on the voids figure. Design guidance usually takes 30 to 40 per cent of the basket, and the stone at 30 per cent is about a sixth more than at 40 — which also changes the wall's weight, the figure a stability check is built on.
- Lacing wire or spiral binders, and the internal bracing ties that stop a face bulging, are supplied and scheduled by the basket maker. Woven and welded baskets are joined differently and makers' schedules differ, so they are not counted here: use the maker's assembly instructions.
- The levelled and compacted bed the wall stands on, the filter fabric behind a retaining wall that stops soil washing through the stone, drainage, excavation and backfill are all outside this count. Gabion mattresses laid flat on slopes and channel beds are sized by area and thickness, not by this page.
Bedding, not footing, and the places concrete does belong
Every gabion job produces the question of whether it needs a concrete base, and for the ordinary case the answer is no — for a reason worth understanding rather than repeating. A gabion is flexible and free-draining: ground that would crack a rigid wall makes a gabion lean a degree and carry on. Casting the stack onto a slab throws that away, putting a hard impermeable plane at the one level where water collects and leaving the bottom course hanging off its edge when the ground beside it settles.
What it does need is a bed. Excavate to competent material rather than to a fixed depth, place and compact a couple of hundred millimetres of well-graded angular crushed stone, and carry it wider than the basket on both hands so the bottom course never bears on a disturbed shoulder. Compaction is specified as a percentage of maximum dry density from ASTM D698, and on soft subgrade the answer is a separation geotextile under the bed rather than more stone above it.
Embedment belongs to the same operation. The bottom course sits below finished grade, deeper where the ground falls away in front of the wall, and deeper again in anything that carries water — there the governing depth is the anticipated scour depth, which is a hydraulic calculation and not a rule of thumb. Burying a course means the exposed height a client describes and the retained height the wall is checked for are two different numbers, so settle embedment before anyone counts baskets.
Concrete does have three honest places on this job. It levels a rock foundation so the bottom course beds evenly instead of rocking on high points. It forms a toe kerb where a wall lands on an existing hard surface with nothing to embed into. And it forms a cut-off in a watercourse where scour has been designed against. In all three the concrete is beneath the wall or in front of the toe, and everything above it stays flexible and drained.
Batter is fixed last and changes the setting-out. Either the whole stack leans back a few degrees into the bank, which needs the bed cut to the same angle, or the face is stepped course by course — usually the choice on a stone-filled wall, since stepping also drops the upper courses' depth. The step dimension comes from the design literature for the system in hand.
What the stack is actually made of
- Mesh baskets, lids and diaphragms — the packaging: it stops the mass spreading sideways and contributes nothing to holding the bank back
- Hand-packed stone and its voids — the actual structure, bought by the tonne against a placed bulk density rather than against the solid rock figure Gabion Basket and Stone Calculator
- Geogrid tails between courses — laid across a completed course and laced under the next, turning the baskets into the facing of a reinforced soil mass Geogrid Reinforcement Layer Count Calculator
- Filter fabric and drainage zone — keeps the retained soil out of the stone while letting the water through, which is the whole reason a gabion face stays dry Geotextile Riprap Fabric Overlap Calculator
- Compacted granular bed — carried wider than the basket on both hands, on subgrade proven competent rather than dug to a nominal depth Gravel Base Layer Tonnage Calculator
From tonnage to self-weight to a check that means something
The density figure comes straight back in the stability work. Self-weight per linear metre is base depth times height times bulk unit weight, and bulk unit weight is that same placed density converted to force: 1,700 kg per cubic metre is about 16.7 kN per cubic metre. A wall a metre deep and two high therefore carries roughly 33 kN per metre of run, and that is the entire resisting side of the gravity check — which is also why a crew that tips rather than packs has quietly redesigned the wall.
Against that sits the active thrust from the retained soil, which grows with the square of retained height and pushes hardest when the backfill is fine-grained and slow-draining rather than the granular material the design assumed. The preliminary check weighs resisting moment against overturning moment and base friction against driving thrust, looking for a comfortable margin on each rather than a bare pass. Bearing pressure under the toe and overall slope stability are separate questions a hand calculation does not reach, and BS 8002 or BS EN 1997-1 is what the real design answers to.
Two features of gabions move the numbers in your favour and one moves them against. In your favour: the underside of a stone-filled basket on a compacted granular bed is a genuinely rough interface, so base friction beats what a smooth footing gives, and the wall is drained by construction rather than by detail. Against: there is a horizontal joint every course, each its own sliding plane, so the check runs at every level. Where it comes out marginal, the cheap fixes are geometric and happen before the order — a deeper bottom course, more step, more embedment, or two terraces instead of one tall wall.
Self-weight per metre is base depth times height times the bulk unit weight you just settled, so the tonnage work feeds straight into this one — and it is worth running both the packed and the dumped density to see how much the crew is holding.
The height of soil being retained, measured from the base of the wall.
The soil's angle of internal friction — get this from a geotechnical report if available.
The soil's unit weight (density x gravity).
The weight of the wall itself (and any soil locked above its heel), per linear meter of wall.
The width of the wall's footprint at its base.
The friction coefficient between the wall's base and the soil beneath it.
Governing safety factor
1.68 (safety factor)
The governing safety factor is 1.68, at or above the 1.5 these checks are commonly taken against. This is a simplified preliminary calculation on the assumptions entered, not a design. Being under the allowable pressure is not the whole ground question: settlement, groundwater and the footings alongside are all untouched here.
- Rankine active pressure coefficient (Ka)
- 0.33
- Active pressure resultant
- 305.56 lbf/ft
- Sliding safety factor
- 1.68
- Overturning safety factor
- 2.52
They open the calculator with your figures already in it
Retaining Wall Preliminary Stability Check: 1.68 (safety factor) — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
What this calculation does not cover
- Bearing capacity of the soil beneath the footing is not checked — a wall can pass sliding and overturning and still settle or rotate.
- Assumes fully drained backfill. Hydrostatic pressure from saturated soil is an additional load not modelled here, and is a leading cause of real-world wall failure.
- No seismic loading. In seismic design categories this omission is significant and a Mononobe-Okabe (or equivalent) analysis is required.
- No surcharge from vehicles, structures or slopes above the wall.
- Global/deep-seated slope stability is not assessed.
Water pressure is not in this calculation at all, and a wall inside the margin on paper still comes apart early if the backfill and the drain are not built. Budget for the compacted granular backfill and the drain whatever the factor says.
When the mass runs out: geogrid between the courses
A gravity gabion stops being economic somewhere in the low metres, and where exactly depends on the soil, the surcharge and the slope above rather than on any published height. The signal is the base course: when the depth the check demands puts three or four baskets front to back at the bottom, you are paying for stone whose only job is to be heavy, and reinforcement gets cheaper than mass.
The reinforced version keeps the baskets as facing and moves the structure backwards. Geogrid layers are run out across a completed course into the retained fill and the next course is laced down onto them, so what resists the earth pressure is the reinforced soil block rather than the stone in the crates. That is a mechanically stabilised earth wall with a gabion face, and FHWA-NHI-10-024 is the design reference the engineering will be built on. Some proprietary systems extend the basket's own mesh backwards as the reinforcement, which removes the connection from the list of things site can get wrong.
Where the grid is a separate product, the connection is the detail to be careful about. It is developed by friction and bearing between the grid and the mesh with the weight of the next course on top, which means its capacity is a tested value for that specific basket and grid pairing, not a property you can assume from the grid's own strength. Substituting a grid because it was on the shelf changes a number nobody re-checks.
Spacing is where gabions differ from block walls in a way that reaches the take-off. Layer spacing cannot be finer than the coursing allows: metre-high baskets give layers at one metre unless part of the height switches to half-metre baskets, which roughly doubles the lacing labour. Length is set by where the failure surface runs, since a layer terminating inside the moving wedge is anchored to the thing it is meant to hold; preliminary work often starts near seven tenths of the height before the stability checks refine it.
Put in the spacing your coursing can actually deliver rather than the spacing you would like: with metre-high baskets the layer count and the course count are the same number, and a finer spacing is a different basket order.
The total height of the reinforced soil structure.
The vertical spacing between geogrid layers.
The horizontal length each geogrid layer extends into the reinforced soil mass.
Geogrid layers needed
10 layers
Layer spacing and embedment length shown here are general starting points — final design requires an internal (tension/pullout) and external (sliding/overturning/bearing) stability analysis specific to your wall height, soil, and surcharge conditions.
- Total geogrid length (per linear unit of wall face)
- 130 ft
- Lift between geogrid layers, as built
- 1.95 ft
They open the calculator with your figures already in it
Geogrid Reinforcement Layer Count Calculator: 10 layers — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
What this calculation does not cover
- This is not a wall design. Nothing here reads soil strength, backfill type, groundwater, surcharge or seismic loading, and nothing reads the grid's rated strength — the layer count is only the height you entered divided by the spacing you entered. Internal stability (tensile overstress, pullout, facing connection) and external stability (sliding, overturning, bearing, global slip) still have to be checked, and a reinforced soil wall of any real height is engineered, permitted work.
- The embedment length is a figure you supply, not one the calculator derives from pullout resistance. It applies the same length to every layer, so it does not model longer lower layers, stepped or tapered layer lengths, or the extra length a design adds where the wall carries a surcharge or founds on weak soil.
- One spacing runs the full height. It does not tighten spacing in the lower part of the wall where reinforcement tension is highest, and it does not add the short intermediate (secondary) layers that segmental block facings and steepened slopes commonly need between primary layers behind the face. That grid is extra to this count.
- The material figure is per linear unit of wall face — per metre of wall run when you work in metres, per foot when you work in feet, because it is an area per unit of run and so converts by the same factor as a plain length. There is no wall run length input. Multiply by your wall length yourself, then add for roll overlaps and seams, grid wrapped back at the face, and offcuts at corners, curves, steps and returns. None of that is in the number, and neither are the roll widths and lengths a manufacturer actually supplies.
- Height is taken as the full height of the reinforced mass. There is no separate input for the portion buried below finished grade, for the levelling pad, for face batter, or for a slope or upper tier above the wall, so entering only the exposed face height leaves the buried zone uncounted.
The back of the wall: two fabrics doing two different jobs
A gabion face is the most permeable wall anyone builds, which solves the water pressure problem and creates a different one. Water arrives at the back of the stack and leaves through the front, and unless something stops it, it brings the retained soil with it. The fines wash through the fill, out at the face, and the void they leave behind the wall becomes a hollow that shows up at the surface as a strip of settled ground running parallel to the top of the wall.
The fabric that prevents it is a filter, set between the retained soil and the drainage zone at the back of the baskets, with an opening size that holds that particular soil while staying permeable enough not to become a dam. That is a different property set from the second fabric on the job, the separation layer under the granular bed, which is there to stop bedding stone punching into a soft subgrade. AASHTO M 288 splits geotextiles into those functional classes with their survivability requirements, and it is what a submittal is sensibly written against.
Ordering fabric is roll arithmetic, and people get it wrong by measuring the wall instead of the rolls. Rolls run down the cut face and adjacent ones overlap, so the overlapped strip counts once for coverage and twice for cost and every roll's effective width is its manufactured width less the lap. The pieces that never appear on a wall elevation are the ones to remember: the crest anchor trench, the tail under the bottom course, and what a stepped or curved run eats at every change of direction.
Run length across, cut-face height down the roll, and the lap your spec calls for — then add the anchor trench and the toe tail by hand, because roll arithmetic does not know about them.
The width of the slope to be covered, measured across the direction the rolls will be laid.
The slope length in the direction each roll runs (e.g. down-slope distance).
The manufactured width of the geotextile roll.
The minimum overlap required between adjacent rolls.
Fabric needed
3,680 ft²
Doesn't include extra fabric for anchor trenches at the slope crest/toe or for irregular slope shapes — add a margin for those if applicable.
- Number of roll widths needed
- 5 rolls
- Effective coverage width per roll
- 14.02 ft
They open the calculator with your figures already in it
Geotextile Riprap Fabric Overlap Calculator: 3,675 ft² — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
Estimated cost — your price
This site holds no price list for this material — local prices vary too much to publish honestly. Enter your supplier's price and the result is costed with it.
What this calculation does not cover
- Roll length is not an input. The total assumes every roll runs the full slope length in one continuous piece, so if the run is longer than the rolls you are supplied you also need transverse end laps, and the real fabric requirement is higher than this figure.
- Nothing is added for anchor trenches. Fabric keyed into a trench at the crest, at the toe, or along the outer edges consumes extra length and width beyond the area being covered.
- The two slope dimensions are used exactly as entered. The model does not convert a horizontal or plan measurement into the longer distance measured down the face, and it adds no cut waste for curved, benched or irregular slopes.
- This is a material take-off, not a filter or erosion-control design. It does not check the fabric's opening size, permittivity or survivability class against the soil and the stone, it does not size the riprap or the bedding layer, and the lap width it uses is whatever you type rather than a value it verifies against a specification.
- It assumes plain shingled laps. Sewn or heat-bonded seams, and the pins, staples or ballast used to hold fabric on the slope while stone is placed, are not counted.
Water at the toe
On a watercourse, gabions rarely fail from behind. They fail from underneath: the flow takes the bed out in front of the bottom course, the face loses its support, and the wall rotates into the hole. Two answers, usually used together. Found the bottom course below the depth the channel can be expected to scour to — a hydraulic assessment, with FHWA HEC-23 on countermeasure selection and CIRIA C683 the general reference for rock in hydraulic works. And give the toe something that can launch: a mattress or loose rock apron that drops into a scour hole as it forms and armours it rather than resisting it.
Sizing a loose apron is plan area times placed thickness, with the thickness a multiple of the stone's median size rather than a round number picked off a drawing. Place it in a single operation to full depth instead of dumping and spreading, keep the gradation well graded and the pieces angular so they key rather than roll, and put a filter beneath it for the same reason there is one behind the wall. An apron placed straight onto the bed without a filter pumps its own foundation out through the voids and settles into the hollow it made.
The apron is bought as bulk stone by volume and judged by its placed thickness, so settle the area and the layer depth here rather than after the first delivery has been spread thin to make it reach.
The slope surface area to be covered with riprap.
The average thickness of the placed riprap stone layer.
Riprap volume needed
47.78 yd³
They open the calculator with your figures already in it
Riprap Slope Protection Volume Calculator: 47.78 yd³ — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
Estimated cost — your price
This site holds no price list for this material — local prices vary too much to publish honestly. Enter your supplier's price and the result is costed with it.
What this calculation does not cover
- This is a quantity take-off, not a riprap design. It does not size the stone or set the blanket thickness, and it makes no check against flow velocity, wave exposure, bank height or slope angle. Both numbers you type have to come from a design or a project specification.
- Toe keys, launch aprons and crest anchor trenches are not included. Those sit outside the slope face you measured, and on a bank or channel job the toe trench is often the largest single extra over the blanket itself.
- The answer is the stone blanket alone. Bedding, a granular filter course or geotextile underlayment called for beneath the riprap is separate material and separate volume.
- No allowance is made for stone lost into a soft or over-excavated subgrade, or for the thickness overrun that comes from placing rock on a rough graded slope. Placed riprap generally takes more stone than the nominal blanket.
- This is volume, not weight. Converting to tonnes or tons needs the placed density of the specific gradation from your supplier, not a solid-rock density, and the difference is large enough to change a delivery count.
When a basket wall is the wrong container
Three signals say the job wants something other than gabions. There is no rock locally above the mesh aperture at a price that makes sense, and the haulage on a hundred-mile stone is larger than the rest of the job. The thing being held is a slope rather than a wall, so the whole exercise of standing rectangular crates up is fighting the geometry. Or the line is tightly curved or terraced, and whole-metre baskets with rigid diaphragms cannot follow it without a cut basket every second unit.
Cellular confinement answers the first two. A geocell layer confines a much smaller and cheaper infill — the granular material a quarry sells by the lorry-load rather than by gradation sheet — and the layers stack into a battered gravity face, the cells doing what the mesh does in a basket. Quantities take the same shape as before, face area times expanded cell depth. The design is proprietary, so the manufacturer's documentation governs panel layout, tendons and anchorage, and an exposed cellular face raises an ultraviolet durability question a buried one never has to ask.
The third option is the honest one where the client says wall but means bank: graded rock placed directly on the slope, no container at all, no lacing labour, and nothing to keep tidy. It takes more room at the toe, it cannot be built vertical, and it looks like exactly what it is. Where those three things are acceptable it is usually the cheapest durable answer on the list, and it is worth putting on the table before a gabion quote goes out rather than after it comes back too high.
Cell depth is the sensitive input here: the same face area against a shallow cell and a deep one produces two very different lorry counts, which is the comparison worth making before the basket order is placed.
The total face area of the geocell wall (height × length).
How deep the wall is from its face back into the slope — the dimension that gives it its mass.
The depth (front-to-back dimension) of the geocell cells, which sets how thick the infill layer is.
Geocell infill volume needed
63.7 yd³
- Geocell panel area across all courses
- 3,440 ft²
- Infill in a single geocell course
- 7.96 yd³
They open the calculator with your figures already in it
Geocell Gravity Retaining Wall Infill Volume Calculator: 63.7 yd³ — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
Estimated cost — your price
This site holds no price list for this material — local prices vary too much to publish honestly. Enter your supplier's price and the result is costed with it.
What this calculation does not cover
- A GRAVITY WALL'S THICKNESS IS WHAT THE STABILITY CHECK SIZES, and this page takes it as given rather than deriving it. Thickness comes out of sliding, overturning and bearing checks against the retained height, the backfill's friction angle and any surcharge — run retaining-wall-stability first and bring its thickness here, rather than the other way round.
- Face area times one thickness is a prism. Battered and stepped walls are not prisms, so enter the average thickness or work each course on its own face area — the error runs in the unsafe direction if you enter the base thickness for a wall that steps back.
- This is the compacted in-place volume of the infill. Granular fill bulks on delivery and loses volume again under compaction, so order against the supplier's loose density and the specified compaction rather than against this figure directly.
- Nothing here covers the facing, the geogrid, the drainage aggregate behind the wall or the base preparation beneath it. Those are separate quantities and, in the case of the drainage layer, one that gets left out of geocell take-offs particularly often because the infill is granular too.
Filling and closing the baskets
Filling is where the design either arrives on site or quietly does not. Two crews with the same drawing, the same baskets and the same stone will build walls whose mass differs by close to a fifth, and neither wall looks wrong from the road. Everything below is about closing that gap.
The face is what gets judged and the hearting is what does the work. Face stones are hand-placed flattest side outward, long axis into the basket, and the smaller graded material falls in behind to fill what they leave. Keep both zones honest all the way up rather than hand-placing the first course and tipping the rest — the height at which the crew stopped packing shows in the face two winters later as the height at which the wall starts to belly.
- Assemble each basket flat, stand the sides and ends, and lace the vertical corners before it goes anywhere near its final position.
- Set the empty basket to line and level on the bed, then lace it to its neighbours along every contact edge, top and bottom, so a run behaves as one unit.
- Brace the row against a temporary frame or straining bar so the faces stay flat while the first stone goes in and the basket cannot pillow outward.
- Fill in layers of roughly a third of a metre, hand-placing the face stones and letting the hearting fall in behind them.
- Fit internal bracing wires face to back between each layer, at the frequency the system's own instructions give — they are what keeps a full basket square.
- Overfill the top layer by twenty-five to fifty millimetres so the lid closes down onto stone rather than into a hollow that will settle later.
- Lace the lid on all four edges, drawing it down with a bar rather than by standing on it, and carry the lacing continuously instead of tying at intervals.
- Place and compact the backfill behind each completed course before starting the next, in lifts thin enough that the plate reaches the bottom of them.
Coating, design life, and what actually finishes a gabion
The design life of a gabion is the life of the wire coating, not of the steel. Once the coating has gone, the remaining section is small enough that there is no corrosion allowance to spend, and the wall is on a short clock from that point. So the coating class is a design decision made against the exposure, and it is the one place on this job where paying more is usually right.
Plain zinc coating to ASTM A641 is the baseline for atmospheric and buried work in benign ground. Zinc-aluminium-mischmetal alloy coating to ASTM A856 lasts materially longer than plain zinc in the same exposure and has become the default for anything with a long design life. Over either of those, a polymer or PVC sleeve is what gets specified for immersion, splash zones, de-icing salt runoff, and acidic, saline or contaminated ground. The gabion standards themselves call up the coating classes; the exposure decides which one you call up.
What actually finishes these walls, in rough order: abrasion in a channel carrying bedload, which strips the coating off the upstream face while the rest looks new; chloride from carriageway runoff, which is why a highway gabion and a garden gabion are not the same specification; permanent contact with damp fine soil, worth remembering before anyone soil-fills the top course to plant it; and cut wires on a public boundary, which on double-twisted mesh is a repair and on a welded panel is a hole.
The compensation is that a gabion is repairable in a way a monolithic wall is not. A bellied face can be opened, re-packed and re-laced. A course that has settled can be topped up. Inspection is a walk along the face looking for stone lost at the base, wires parted at ground level, and a top line that has stopped being straight — and any of those found early is a morning's work rather than a demolition.
Settle these before the first basket is laced
A gabion wall is cheap to change on paper and expensive to change once thirty tonnes are inside it. These are the figures that fix the job.
- Placed bulk density of the fill — Particle density from the quarry less the voids the crew will actually achieve — roughly 1,550 to 1,850 kg/m³ for sound rock, and both the tonnage and the self-weight come off it.
- Depth of the bottom course — This is the wall's base width, so it comes from the stability check rather than from what the pallet happens to contain; steps above it reduce the upper courses.
- Bed and embedment — Compacted granular bed on proven subgrade, carried wider than the basket both sides, with the bottom course buried below finished grade — deeper again where water can scour in front of it.
- Mesh system and coating class — Double-twist where settlement is expected, welded where the face must be flat; coating chosen against immersion, salt and abrasion rather than against price.
- Filter and separation fabric — A filter between the retained soil and the drainage zone, plus a separation layer under the bed on soft subgrade. Add the crest anchor trench and the toe tail to the roll count by hand.
- Gravity or reinforced — If the gravity check fails, choose between a deeper base course and geogrid between courses before ordering — the two produce completely different basket schedules.
Opens the calculators above on one screen with the dimensions from this article already filled in. Quantities only — this site publishes no price list, because local prices vary too much to publish honestly.