Ordering Fabric, Mulch and Gravel for a Planting Bed

One Tape, Three Units on the Quote

The border runs eighteen metres along the drive, bows out to two and a half at its widest and pinches under a metre at the gate. The client wants slate chipping over barrier on that side and shredded bark on the bed across the path, and a price by Monday. Every line of that quote comes off the same afternoon's tape work, and every line leaves the yard in a different unit: fabric in whole rolls, bark in cubic yards or bulk bags, stone in tonnes. Measure once and the three numbers agree. Measure loosely and the error is not one error, it is three, and it surfaces as a bed half-dressed with the truck already gone.

Beds are not rectangles, and a planting plan drawn to fit an A3 sheet is not a survey. The usable field method is offsets: run the tape along the straight side that already exists — the path, the kerb, the fence line — and take the bed's width square off it at a fixed interval, every metre or every two. Average each consecutive pair of offsets, multiply by the interval, and add the strips. On a border of twenty-odd square metres that lands inside five per cent, which is closer than the depth will be spread and far closer than the density figure behind the tonnage.

Then decide what you are not covering. Existing shrubs displace almost nothing at mulch depth and are not worth deducting; a mature root plate you will dress thinly, a boulder, a pond edge or a set of stepping stones are. The opposite trap is more expensive: the area you dress is the area inside the edging, not the area occupied by the planting. On a newly planted bed those two differ by a third, and the third that gets forgotten is always bare soil the client can see from the kitchen window.

Depth Belongs to the Weed, Not to the Budget

Seventy-five to a hundred millimetres of bark is the working band for suppressing annual weed and holding moisture, and it is the band the horticulture extension literature has settled on. Below about fifty, enough light reaches the soil that seed in the top few millimetres germinates straight through; above a hundred on a heavy, slow-draining soil you start trading weed control against root oxygen and against water that never reaches the soil at all because the mulch absorbs it first. Shaving the depth to make a price work does not save money, it converts a three-year dressing into a one-season one and hands the follow-up call to somebody else.

Spread depth is never uniform, and the variations mostly cancel. It thins over the root plate of an established shrub and it pulls back clear of stems and trunk flares — ANSI A300 (Part 2), the soil management part of the American National Standard for tree, shrub and other woody plant management, is the document to point at when a client asks why the bark stops short of the trunk rather than piling against it. What does not cancel is the generosity of a crew working from a full barrow at the near end of the bed, which routinely puts a hundred and twenty millimetres down over the first third and leaves the last third short.

Stone is a different conversation entirely. A decorative chipping over barrier is bedded at forty to fifty millimetres: deep enough that the fabric does not show and the stone does not scatter, shallow enough that a rake still finds the fabric to level against. Beyond that, stone on a bed simply migrates when anyone walks it, and the honest answer to a bed people keep crossing is a stepping course or a path, not another fifty millimetres of chipping to lose.

Settlement decides the difference between the order and the finished surface. Coarse bark consolidates through its first wet season, so a bed spread at a hundred reads nearer seventy-five the following spring — which is what the annual top-up exists to correct, and why the first order and the maintenance order are never the same size. Buy against the depth you intend to have on the ground the day you spread it, and let the settling allowance rather than an inflated depth carry the rest.

Barrier Under Stone and Barrier Under Bark Are Two Different Decisions

Beneath a stone dressing, fabric does real physical work. It keeps chipping from being trodden down into soft soil and it keeps fines from working up into the stone, so the bed still reads as clean slate in year five instead of as gravelly loam. That is separation, the same function an engineered geotextile performs under a base course, and on a planting bed it is the strongest argument the material has.

Beneath bark, be straight with the client. Organic mulch is meant to break down, and what it breaks down into settles on top of the fabric as a fine, fertile layer that makes an excellent seedbed. Within a few seasons weeds are rooting above the barrier rather than under it, where they are harder to pull because the roots knit into the weave, while the fabric itself sits between the decomposing mulch and the soil it was supposed to be feeding. A bark bed at proper depth, topped up annually, generally beats a bark bed with fabric under it — and costs less to build.

It is also worth knowing what a garden-centre roll is not. Separation and filtration geotextiles are bought against AASHTO M 288, Geosynthetic Specification for Highway Applications, which sorts them into classes by subgrade condition and installation severity, and the properties behind those classes come from named index tests: ASTM D5261 for mass per unit area, ASTM D4632 for grab breaking load, ASTM D4833 for index puncture resistance, ASTM D4751 for apparent opening size and ASTM D4491 for permittivity. A landscape roll typically declares ounces per square yard and a lifespan in years and nothing else. That is not a reason to refuse it on a planting bed; it is a reason not to let it drift into a detail — a drive base, a retaining wall drain — where the specification calls for a classed geotextile.

Laying it is mostly about the seams. Standard landscape rolls are three feet wide and a hundred feet long, which is the three hundred square feet most yards quote and the coverage the roll count below is built on. Lap every seam by around a hundred and fifty millimetres, pin the laps and the perimeter rather than pinning the middle of a sheet that is not going anywhere, run the fabric right up to the inside face of the edging and tuck it, and cut an X at each plant with the flaps folded under instead of cutting a generous round hole that becomes a weed port.

The ten per cent overlap allowance most roll calculations carry, this one included, is honest on an open bed and optimistic on a narrow one. A border two metres wide takes the same lap every three feet of width, so the waste fraction climbs well past ten per cent; a curved edge trims material off both sides of every pass. Where the shape is awkward, count the passes on paper instead: bed width divided by the roll width less one lap, rounded up, times the run length. Compare that against the area-based figure and buy the larger of the two, because a roll is a stock item and the second trip to fetch one costs more than the roll.

Bags on a Pallet, or a Pile on the Drive

The crossover between bagged and bulk is an access question before it is a price one. Bags cost more per unit volume and cost labour again at the other end, but they stack on a pallet, go through a side gate, stage across two visits and leave no heap on block paving the client has just had cleaned. Bulk is cheaper and arrives in one movement, in one place, and every metre between that place and the bed is barrow work somebody is paying for. Two cubic feet of bark is around twenty-three kilos and the same bag of damp compost is nearer thirty-one, which is why repeated manual handling on a pallet job belongs in the price and, on a long day, in a look at the Applications Manual for the Revised NIOSH Lifting Equation.

Units are not casual here either. North American bagged bark is commonly two cubic feet; UK and Australian bags run fifty to seventy litres; and a bulk bag is a volume, not the tonne its nickname implies. In adopting US states the method of sale for these products falls under NIST Handbook 130, Uniform Laws and Regulations in the Areas of Legal Metrology and Engine Fuel Quality, whose Uniform Regulation for the Method of Sale of Commodities is what puts mulch and soil into cubic measure rather than weight. Material quality has its own paperwork worth asking for: in the UK, BS 3882 Specification for topsoil and PAS 100 Specification for composted materials are documents a supplier can be held to, and a conformance sheet is the only thing separating a graded product from whatever was in the bay that week.

Stone Leaves the Yard by Weight and Arrives at a Depth

Between the bed and the invoice sits one number nobody on the job has measured: bulk density. The bed gives an area and a depth, which gives a volume; the yard sells tonnes; density is the only bridge. For aggregate it is properly established by ASTM C29/C29M, Standard Test Method for Bulk Density (Unit Weight) and Voids in Aggregate, which is a laboratory procedure on a specific sample — not a figure that transfers cleanly from a table to a bay that has been rained on for a fortnight. Moisture is measured in its own right by ASTM D2216, Standard Test Methods for Laboratory Determination of Water (Moisture) Content of Soil and Rock by Mass, and a ten to twenty-five per cent swing between the published density and the material on the day is entirely ordinary. In Europe, graded aggregate for unbound use carries a declaration against BS EN 13242; decorative chipping frequently carries no such declaration at all, which is worth knowing before promising a client a consistent size.

The table below holds the typical dry loose figures the converter on this page works from, with what a cubic yard of each weighs. Read across two rows and the whole delivery problem is visible: the same body volume of bark and of gravel differ by a factor of four in weight, so the two materials are constrained by completely different things on the way to site.

One more trap sits in the word ton. A metric tonne is a thousand kilograms and a US short ton is about nine hundred and seven, roughly ten per cent apart, and a quote written in one against a delivery note issued in the other is a ten per cent error in whichever direction hurts. Quote the client in volume, order from the yard in the unit the yard invoices, and write both on the paperwork so the weighbridge ticket can be checked against something.

What the Yard Is Prepared to Send, and What the Drive Will Take

Tipper bodies are hired in whole sizes — ten, twelve and fourteen cubic yards in North America, eight, ten and twelve cubic metres in metric markets — and what goes into one is capped twice over, by the volume of the body and by the payload the axles are allowed to carry. Which cap binds is decided entirely by the material, and that is the single most useful thing to understand before phoning an order through.

Fill a twelve-yard body with bark at four hundred kilograms per cubic metre and you have moved something like three point seven tonnes: the body is full and the truck is barely working. Fill the same body with gravel at sixteen hundred and the figure is close to fourteen and a half tonnes, which is past the payload of most single and tandem bodies — so the driver stops well short of the sides and the body goes out part empty. That asymmetry is why bark arrives in one drop and stone arrives in two, and why the same supplier quotes bark in yards and stone in tonnes without ever explaining the switch.

The limits themselves are not the estimator's to set. Gross and axle weights on the public road come from federal and state law in the United States and from the Road Vehicles (Construction and Use) Regulations in the United Kingdom, and the weighbridge that produces the ticket is a device held to NIST Handbook 44, Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices. What matters on the quote is that the yard applies those limits before you do, and a quantity that ignores them turns into a delivery schedule you did not price.

Then there is the last hundred metres, which no calculator can see. Where can the body stand, and can it reverse to there? Is there an overhead line or a low branch, given that a tipping body reaches well over twice its travelling height? Will a loaded axle stand on block paving or a soft verge without leaving a bill? How far is the tip point from the bed, because that distance is barrow runs and barrow runs are the labour line most under-priced on a soft-landscaping job. And most yards carry a minimum bulk order and a delivery charge that does not scale down, so ordering thirty cubic feet short does not save the price of thirty cubic feet — it costs a second delivery.