Getting Excavated Spoil Off a Small Site: Four Streams, Two Ceilings and One Test Booked Early

The turf goes first and it must not go with the soil

Before any of the arithmetic there is a strip: the lawn across the footprint, the border along the boundary, the shrubs in the way of the barrow run, and the root mat under all of it. It is a trivial volume next to the dig — a few cubic metres here — and the easiest way on the job to turn a cheap load into an expensive one, because a soil load with green material in it stops being clean soil the moment somebody at the tip looks into the skip.

Measure it as any other strip is measured, area times an average depth, but take the depth honestly rather than calling it 100 millimetres because that is what topsoil is supposed to be. Under an old privet hedge the fibrous mat runs deeper than under a lawn, and the access strip you are about to barrow down for three weeks is different again from the border nobody has touched. Two or three small patches with a measured depth each beat one figure for the garden.

Where a strip covers real ground rather than a back garden the vegetation becomes the dominant stream and the job changes character; that version — brush volumes, stump tallies, what a green waste facility will and will not take — is worked through in the clearing and grubbing guide rather than here. On an extension this quantity has one job: stay in its own pile from the first hour, because it is the cheapest stream on site and it is standing next to the most expensive one.

One hole gets replaced, the other gets refilled, and only one of them is a haul

Not every trench on this job produces spoil that leaves. The footing trench does, completely, because concrete goes in behind the bucket and there is nothing to put the clay back into. The drain run out to the existing inspection chamber does not, or rather it does and then something else has to arrive to fill the void, because a 110 pipe wants a granular bed and surround and the specification for that comes from BS EN 1610 and Approved Document H, not from what happened to come out of the hole.

So the drain trench is a double movement, and it is the one people net off to zero in their heads. Nine metres at 500 wide and 800 deep is 3.6 cubic metres out. The pipe displaces less than a tenth of that, so the void is close to 3.5, and filling it needs more than 3.5 of loose stone because granular material consolidates as it is punned in layers. Around four cubic metres of shingle arrives on the same twelve metres of kerb a spoil wagon needs. Two movements, opposite directions, and if they are not sequenced somebody spends an afternoon shovelling stone off the pavement.

Run each trench with the pipe you are actually laying and read both halves of the answer: the excavation line in the breakdown is what leaves, and the headline is what has to arrive. On a job with a drain run, a water service and a duct to the garden room that pair repeats three times at three different sections, and the arriving side is the easy one to under-order, because it appears on no muck-away quote at all.

1. Measure the footing trench as designed and treat all of it as leaving — concrete is replacing it, so nothing goes back.
2. Measure each service trench separately with its own width, depth and pipe, because a 110 drain and a 25 water service do not share a section.
3. Decide per trench whether the specification lets the arisings go back or calls for imported granular, and put the import on the delivery schedule the day you book the removal.
4. Book the two movements on different days where there is only one place on the street to stop.

Twenty-seven cubic metres in the ground, thirty-four in the side return

Add the streams as they sit in the ground and the job makes about 26.8 cubic metres: 11.2 from the footings, 8.4 from the reduced level, 3.6 from the drain run and 3.6 from lifting the old patio and the sub-base under it. Nothing on this site will ever see 26.8 cubic metres of anything. The moment a bucket lifts it, that material occupies a quarter more space than the hole it came from, and the number that matters for the side return, the skip, the wagon and the bit of lawn you were going to keep clear is the larger one.

The factor is not a constant and it is not shared across the four streams. A broken sub-base, already loose, gains little. Topsoil off a lawn gains modestly. Firm clay from the bottom of a 1.1 metre footing trench comes out in lumps with voids between them and gains most, and clay lifted from real depth behaves more dramatically again — the deep trench-fill case, and the reason a quarter to a third is the working range, is set out properly in the guide on founding near trees. Run each stream on its own factor, taken from your ground data or from whoever hauls muck in your area rather than from a default.

The third column of the same conversion is worth a look even where there is nowhere to put anything. Recompacted, this material occupies less than it did in the ground, which is the arithmetic behind every decision to raise a garden level or backfill a soakaway surround with what you dug rather than what you bought. On a terraced infill the answer is usually that none of it stays — but it should be reached rather than assumed, because a cubic metre kept is a cubic metre never lifted, weighed, tipped or taxed.

One practical warning about the space itself. Thirty-four cubic metres of loose spoil in a side return 900 millimetres wide works out at a wall of muck three metres high running the length of the house — which is to say it will not stand there at all. What it does instead is spread across the ground you need for the scaffold, the mixer and the brick stack. Either the wagon arrives as the dig proceeds or there is a plan for where the heap lives, and dig-and-load is nearly always cheaper once double handling is counted.

The stripped soil is the only stream that is worth something

Screened topsoil is a material people buy. The 3.6 cubic metres coming off the top of the reduced-level dig is roughly four and three-quarter cubic yards, and at the planning density this catalogue publishes for topsoil — about 1.2 short tons per cubic yard, near enough five and a bit tonnes here — it is a small delivery's worth of something the landscaping phase of this very job is going to order back in at the end. Tipping it in August and buying it in November is a fairly common way to pay twice for the same soil.

Whether it can be kept is a space question and a quality question, in that order. It needs somewhere flat, off the working area, off the ground you will later lay a slab on, and covered if it is sitting through a wet autumn — and it needs to actually be topsoil rather than the top of an old flowerbed with half a patio underneath. The weight is worth knowing even when it leaves, because soil holds water: the same cubic metres off a garden in February and in July are different tonnages, and where you pay by the tonne, part of what crosses the weighbridge is rain.

Weight is what a wagon runs out of first

The clay is the stream that fills the lorry, and it fills it long before it fills the body. Nineteen and a half cubic metres of it in the ground — footings, the subsoil half of the reduced level, the drain trench — is about 25.6 cubic yards, which at the catalogue's planning figure of roughly 1.5 short tons per cubic yard is near 38 short tons, call it 35 tonnes. Add five for the topsoil and something like six for the patio slabs and their sub-base, run through a rubble density rather than a soil one, and this modest extension is moving around forty-six tonnes off a terraced street.

One rule governs the conversion and it is the rule people get wrong: put the bank volume through the density, never the bulked one. Bulking adds air, air has no mass, and multiplying a swelled volume by a soil density invents a quarter of the tonnage out of nothing. The full working of that trap sits in the near-trees guide. The short version is that volume and mass need different inputs from the same takeoff, so carry both columns side by side and nobody has to remember which was which at eight in the morning.

Holding the tonnage rather than the volume matters because almost every commercial term downstream is expressed in it. Disposal is charged by weight. Landfill tax, where it applies, is charged by weight. The vehicle's legal ceiling is a weight, set by its plating and by the axle and gross limits in the Road Vehicles (Authorised Weight) Regulations 1998 — the haulier's compliance problem right up to the moment it becomes your programme problem at a weighbridge. A firm quoting per load is quoting against a payload they know and you do not, so ask for it in tonnes and do the division yourself.

Grab or skip is decided at the kerb, not on the spreadsheet

There are three ways this material leaves a terraced house, and the geometry at the front picks between them before any arithmetic does. A skip stands on the drive or, with the highway authority's permission under section 139 of the Highways Act 1980, on the road — permitted, lit and marked to the Builders' Skips (Markings) Regulations 1984. A grab lorry stands in the road and lifts over a wall or hedge, so it never enters the property, but it wants clear airspace and a stable place to put its legs down. A tipper loaded by an excavator needs machine and lorry in the same place at once, which past a 900 millimetre side return means a conveyor, a dumper through the house, or a great deal of barrow.

Cube and weight give two different load counts and you want both. At around 33.5 cubic metres loose against a typical twelve-cubic-metre body, this job is three loads. At roughly forty-six tonnes against the payload an eight-wheel grab is plated for, it is four. The larger answer is the real one, and on soil it is nearly always the weight answer — which is why haulage firms will not put dense inert muck in their biggest containers, and why a skip on a drive full of wet clay is a conversation with the skip company rather than a delivery.

So the constraint is not cubic metres per day, it is stops per day. Each stop occupies the road, needs the neighbour's car gone, needs a banksman if it is reversing past a school run, and carries a cycle time back to wherever the tip is. Booking four loads for a day the site can absorb two of is how a machine ends up standing. Overloading is the costlier failure and it is invisible from the pavement: a grab body two-thirds full of saturated clay can be at its limit, and the driver stopping short is not being awkward. Fill to a line agreed with the operator rather than to the rim, and keep the wettest material for the loads with payload to spare.

When the street will not take an eight-wheeler

Some jobs have no eight-wheel option: a weight-restricted lane, an unadopted road the residents' association will not have heavy vehicles on, a bridge with a plated limit, or simply a turning head that a rigid cannot get out of. What replaces it is a 3.5 tonne tipper, and the arithmetic changes shape completely because that vehicle's usable payload is a fraction of its gross weight once the body, the crew and a full tank are counted.

This is where the load-count box has to be filled in with a de-rated capacity rather than the body's cubic capacity, and it is the most common estimating error on a restricted street. A small tipper body might hold a cubic metre and a half heaped. It cannot carry a cubic metre and a half of loose clay, because loose clay at roughly 1.4 tonnes per cubic metre would put that vehicle well over its limit. Divide the legal payload the operator confirms by the loose density of the stream and enter that figure — for this job something nearer 0.8 cubic metres than 1.5. The 33.5 cubic metres then comes out at forty-two loads rather than twenty-three, which is a fortnight of vehicle movements past the neighbours instead of a week, and it changes the price, the programme and the conversation with the council in one step.

The spread between the rates is the argument for testing

Classification is worth money, not merely worth doing, because of the size of the gap it sits on. Inert, non-hazardous and hazardous soil are three gate rates at three facilities, and on top of the facility's own charge sits the disposal tax the jurisdiction applies — in England and Northern Ireland, Landfill Tax under the Finance Act 1996, charged per tonne at a standard rate with a lower rate for the qualifying materials listed in the Landfill Tax (Qualifying Material) Order 2011, and in Scotland and Wales the devolved taxes that replaced it on the same shape. This site publishes no rates, because they are local and they are revised, but the shape is stable: across forty-six tonnes the distance between the top and the bottom of that range dwarfs the cost of a sample.

So run the disposal twice. Take the tonnage the streams actually produced, price it at the clean-soil rate you have been quoted and again at the contaminated rate, and look at the difference. That difference is the exposure you carry on a plot with a history that nobody has tested, and it is the number that turns a testing schedule from an expense into an insurance premium in front of a client. It is also what justifies segregating at the dig face, because a small quantity of bad material in a good load prices the whole load at the bad rate.

Two things to confirm before entering anything. The unit the facility quotes in, because a rate per short ton and a rate per tonne differ by about a tenth and both are spoken aloud as a ton. And what sits inside the quoted figure: whether tax is included or added, whether a minimum charge makes a part load cost the same as a full one, and whether the material has to be tested to the facility's own schedule before they will take a booking at that rate at all.