Twelve Pins and Two Contracts on One Wall
The wall is twelve metres of solid one-brick party wall on a stepped strip footing 900 mm below the yard, and the temporary works drawing breaks it into twelve bays of a metre, numbered in a hit-and-miss order so that no two neighbouring bays are ever open together. The pins go to 3.6 m. That depth is not a judgement about bearing. It is set next door, where a new basement formation is at 3.2 m, four hundred millimetres above the toe of the pin that is meant to be underneath it.
Price this by volume and you lose money on it. Twelve pits a metre long and 1.25 m wide, taken 2.7 m down from the underside of the existing footing, is a little over forty cubic metres of dig — an hour and a half of machine time if a machine could reach it and if it were one trench. It is not one trench, nothing tracked is going in, and the programme is eight weeks. Every cubic metre on that dig sheet is bought again as a visit: a gang arriving, a bay opened, a bay shuttered, a pour, a strike, and a separate return days later to ram the joint at the top.
The second thing the sequence does is harder to see on a rate. Underpinning hands the wall more depth to bear on and, on this job, takes away nearly everything that was standing in front of it. The soil the neighbour is about to dig out is the same soil a sliding check counts as passive resistance, and the day their excavation reaches formation is the day that term drops to whatever is left below their slab. Both halves of this page follow from that split: what the sequence costs, and what it leaves behind to push back.
What Goes on the Dig Sheet, and What Gets Cast
Pit and pin are not the same object and the takeoff wants both. The pit is the hole — long enough to work in, wide enough to shutter, deep enough to stand a man in with a shovel. The pin is the mass concrete left in it afterwards. Bay length on a hit-and-miss sequence is a temporary works decision about how much of the existing footing may be unsupported at any moment, and that decision belongs to the engineer who signed the sequence, not to whoever is filling in the box.
Width is where the sheet drifts first. It is not the width of the existing footing. It is the footing plus a toe front and back wherever the design projects the pin beyond it, plus whatever the shutter and the arms holding it need. On a party wall you may be permitted to project one way only, which makes the pin eccentric and the pit asymmetric — worth catching before a symmetrical hole gets priced twelve times over.
Depth runs from the underside of the existing footing down to formation. Not from ground level, and not to the top of the pin. Blinding, where the specification calls for it, sits inside that depth. So does the gap deliberately left between the top of the cast pin and the underside of the old footing, which is part of the pit, part of the excavation, and part of nobody's concrete order.
Twelve identical bays is the drawing's fiction. Corners take a different pit shape, a return needs a pin of its own, and any bay crossed by a live drain or an incoming service is dug at half rate or moved altogether. Take the standard bay through the calculator, then carry the exceptions as their own lines. Folding them into an average is how a twelve-bay job becomes a fourteen-bay job with twelve bays paid.
Run the standard bay first — pit length, pit width including the toe projections, and depth from the underside of the existing footing to formation — then put the corners and the service crossings through as bays of their own instead of averaging them into the count.
The total number of underpinning pits in the sequence.
The length of each individual pit.
The width of each pit.
The depth of each pit, down to the new bearing level.
Total excavation volume
13 yd³
Doesn't include temporary shoring, dewatering, or the new underpinning concrete volume itself — this is excavation volume only.
- Volume per pit
- 2.59 yd³
They open the calculator with your figures already in it
Underpinning Pit Excavation Volume Calculator: 12.96 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 bank volume — soil measured as it sits in the ground. It bulks once it is on the shovel, so skip fills, grab loads and barrow runs all count a larger figure than this, by an amount that depends on the soil. None of it is backfilled either: the hole is filled with concrete, so the whole volume leaves site.
- The calculation takes the three dimensions exactly as typed and adds nothing to them. There is no allowance for working space, shutter and strut clearance, over-dig, or the toe projections a pin is designed to make beyond the existing footing — enter the footing width as the pit width and the dig comes out short.
- Every pit is treated as the same box repeated. Corners, returns, stepped footings, eccentric pins where projection is permitted one way only, and bays crossed by a live drain or service are all different shapes, and folding them into one average bay misprices the exceptions. Run the standard bay here and carry the odd ones as their own lines.
- This is a quantity take-off, not a design and not a temporary works check. Bay length, how many bays may stand open at once, how far apart they must be, the excavation support, and the depth needed to reach a stratum that will bear are decisions for the engineer who signs the sequence. Nothing here verifies that the dimensions you entered are safe to excavate beneath a loaded footing.
- The figure is neither the concrete order nor the price. The pin is cast short of the existing footing so the dry-pack joint can be rammed, and any blinding sits inside the same depth, so pit volume overstates the mass concrete — and a sequenced underpin is bought in visits per bay (dig, shutter, pour, strike, return to dry-pack, monitor, stand while the neighbouring bay makes strength), which does not scale with volume.
Everything That Comes Out Leaves, and It Comes Out Bigger
Two things separate underpinning spoil from trench spoil. The first is bulking: soil that measured a cubic metre in the ground measures more once it is off the shovel, and everything downstream of the shovel — barrow runs, skip fills, grab loads — is counted in that larger state. The second is that none of it is coming back. A trench gets backfilled. A pit gets filled with concrete, so the whole bank volume leaves site and an equivalent volume of concrete arrives to replace it.
Swell is a soil property, not a constant. Take it from the ground investigation or from what the local muck-away contractor genuinely sees, rather than a round number from a table — a stiff clay and a sandy gravel do not behave alike in a barrow, and a clay dug wet does not behave like the same clay dug dry. What matters to the price is that the skip count keys off the loose figure while the concrete order keys off the bank figure, and confusing the two moves the number the wrong way at both ends.
Access decides the rest of it. Most underpinning spoil is hand-dug, barrowed and lifted — through a house, along a side passage, up a ramp to a skip standing on the street under a permit. That route carries a rate per cubic metre of its own that has nothing to do with excavation and everything to do with distance, corners and stairs, and it is charged against the loose volume. One unit note before the swell tool is used for any of that: its bank volume field follows the metric and imperial switch at the top of the page, reading cubic metres or cubic yards, so the figure goes in the unit the field names and comes back in the same system.
| Volume state | Where the figure comes from | What it prices |
|---|---|---|
| Bank, in the ground | The pit volume calculator, off the dug dimensions | Concrete for the pin, plus the gap the dry-pack later fills |
| Loose, in the barrow and the skip | Bank volume with the swell the ground investigation gives | Skips, grabs, haulage, and the barrow route out of the property |
| Recompacted | Not reached on a job like this one | Nothing here — it only applies where spoil is reused as fill elsewhere |
Bank volume from the dig sheet, swell from the report rather than a habit, and the loose figure that comes out is the one the skips and the barrow rate are actually charged against.
The undisturbed, in-situ soil volume.
How much the soil expands once excavated and loosened, as a positive percentage.
How much smaller the soil ends up once recompacted, as a negative percentage.
Loose (haul) volume
163 yd³
Swell and shrinkage factors vary significantly by soil type and moisture content — use site-specific values from a geotechnical report or local hauling experience where available, rather than generic averages.
- Bank (in-situ) volume
- 130.75 yd³
- Compacted (recompacted) volume
- 117.68 yd³
They open the calculator with your figures already in it
Soil Swell & Shrinkage Haul Volume Calculator: 163 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
- The swell and shrinkage percentages are figures you supply, not properties this page derives. Moisture content, fines content, how the material is dug and the compactive effort actually applied all move the real factors, and the same soil at a different moisture will not behave like the number you typed. Take the factors from the site investigation or measured local experience, not from a general table.
- This is a volume conversion, not a haulage calculation. It does not size trucks, count loads, or apply payload limits — wet or dense spoil often reaches a lorry's weight limit before it fills the body, and heap, tailgate profile and further bulking during loading all sit between this loose figure and a load count.
- The compacted figure is not a compaction specification. It assumes the placed fill achieves exactly the shrinkage percentage entered, and says nothing about the density the fill must be tested to, layer thickness, the plant used, or material rejected and reworked. It does not replace field density testing.
- One bank volume with one pair of factors. A mixed excavation — topsoil over clay over rock, or a trench through made ground — has different swell and shrinkage per stratum, and running the whole quantity at a single figure misstates both the haul and the fill. Topsoil stripping and unsuitable or contaminated material that leaves site instead of returning to fill are outside the model entirely.
- The loose volume describes material immediately after excavation. A stockpile consolidates under its own weight and with rain, so a survey of a pile that has stood for weeks comes back below this figure. Nothing here addresses waste classification, tipping, or duty-of-care disposal requirements for spoil going off site.
What Is in the Hole Once You Have Finished
A finished pin is short and unremarkable, and most mental pictures of it are wrong in four ways at once. It is not poured up to the underside of the existing footing. It is not reinforced unless the drawing says so. It is not the only thing carrying the wall in that bay. And the last operation on it happens days after the pour, usually by a different pair of hands.
Cast the pin and stop short of the old footing by the gap shown on the temporary works drawing. Mass concrete shrinks as it cures and bleeds water upward; a pin poured hard against the underside would settle away from the very thing it is there to hold, and the wall would find that out before anyone else did. The gap is deliberate and its depth is specified — read it off the drawing rather than working to a remembered number, because it moves with the mix and with the engineer.
The joint is closed later with dry-pack: a semi-dry sand-and-cement mix rammed in from both faces until it will take no more. Semi-dry because it barely shrinks, rammed because compaction is the only thing making the connection. Mix and timing come from the temporary works designer. The return visit to do it is a programme line that estimators leave out more often than any other item on the job.
Underneath, the pin bears on whatever the pit actually reached. Blinding, where specified, is there to give a clean base to cast against, not to spread load. And in front of the pin — on the face that looks toward the neighbour's dig — there is soil doing structural work that appears on nobody's drawing, which is the subject of the rest of this page.
What one completed pin is made of
- Existing wall — the load that has to reach the new bearing level — its own weight plus whatever the floors and the roof hand it
- Existing strip footing — the original bearing surface, which has to span across every bay while that bay is open beneath it Footing Soil Bearing Pressure Checker
- Dry-pack joint — the semi-dry mix rammed in days after the pour; until it is packed the pin below is carrying nothing at all
- Mass concrete pin — cast in the pit and stopped short of the footing above; the pit around it is what the dig sheet measures Underpinning Pit Excavation Volume Calculator
- Founding stratum — whatever the pit reached, which the boreholes were supposed to have described before the depth was priced Shallow Foundation Bearing Capacity Calculator (Vesic Factors)
Deeper Is Not the Same as Better
The pins here go to 3.6 m because the neighbour's formation is at 3.2 m, which is a geometric reason rather than a geotechnical one. Whether the ground at 3.6 m is worth founding on is a separate question, and it is answered from the boreholes: the stratum description and its classification under ASTM D2487, blow counts from a standard penetration test to ASTM D1586, and whatever strength testing the investigation ran. If the logs stop above the proposed formation, the depth is a guess and every rate built on it inherits the guess.
A screening check on the founding stratum belongs before the sequence is priced rather than after, because a stratum that will not take the pressure means deeper pins, and deeper pins mean more spoil, more shutter, more concrete and more visits. The whole ledger moves together. Terzaghi's equation is the usual first pass: bearing capacity factors driven by the friction angle, the cohesion of the stratum, and the overburden already sitting at formation level.
Read what comes back for what it is. It is an ultimate capacity, not an allowable pressure — a real design divides it down by a factor of safety, and the geotechnical engineer picks that factor, not the calculator. It is also written for a strip footing, while an underpinning pin is far closer to a square pad, so the shape and depth corrections a pad check needs are simply absent from it. Its cohesion, overburden and unit weight fields follow the measurement switch like its lengths do, so a report written in psf and pcf goes in as it stands. Use it to learn whether the stratum is in the right order of magnitude for the load coming down. Anything sharper than that belongs to the engineer whose name is on the drawing.
Friction angle and cohesion from the borehole logs for the stratum at pin formation, overburden as the weight of everything above that level, and the pin width as B — a screening figure, before the depth on the drawing is treated as settled.
The soil's cohesion.
The soil's angle of internal friction.
The overburden pressure at the footing's base level.
The soil's unit weight below the footing.
The footing's width.
Ultimate bearing capacity
22,300 psf
This gives ULTIMATE bearing capacity — a real design divides this by a factor of safety (commonly 2.5-3.0) to get the allowable bearing pressure, and applies shape/depth/inclination correction factors for non-strip footings, which this simplified strip-footing calculator omits.
- Nc
- 30.14
- Nq
- 18.4
- Nγ
- 22.4
They open the calculator with your figures already in it
Shallow Foundation Bearing Capacity Calculator (Vesic Factors): 22,324 psf — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
Add the equipment this sizes
This result is a specification — 22,300 psf — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.
What this calculation does not cover
- Ultimate capacity at shear failure, with no settlement check. On sand and on stiff clay the working pressure is usually set by total and differential settlement rather than by bearing failure, so a footing can clear this figure and still move more than the structure above it will tolerate.
- Groundwater is not in the model. There is no water table input, and when water stands at or above founding level both the surcharge term and the 0.5×γ×B×Nγ term have to be built from effective stresses — the unit weight field will not even accept a submerged unit weight, its floor being 14 kN/m³ (89 pcf). Reduce q and γ yourself before entering them, or the capacity reads high.
- Strip footings under a vertical, centrally applied load only. No shape, depth, load-inclination or ground/base-slope factors are applied, so a square or rectangular pad, a circular base, a raft or an eccentrically loaded footing falls outside it; eccentricity also calls for the effective-width reduction B − 2e, which this does not do.
- General shear failure is assumed at every friction angle. Loose sands and soft compressible clays fail by local or punching shear, where these factors overstate capacity, and no reduction to c or tanφ is made for it.
- One uniform soil, taken to extend through the whole failure wedge — roughly one to two footing widths below the base. Layering is invisible to it: a soft stratum under a firm crust, or fill over natural ground, returns the crust's capacity. This is a screening figure against parameters someone else measured, not a foundation design, and it does not replace a site investigation or an engineer's allowable bearing pressure.
The Support Somebody Else Is Removing
Until the neighbour starts, this wall has metres of undisturbed ground standing against the face of its footing. Once their basement is at formation it has whatever sits below their slab and nothing above it. Vertical support has been improved by the pins; lateral support is being removed by a different contract, on a programme nobody has drawn against yours.
That makes it a legal question before it is an engineering one. In England and Wales, excavating close to a neighbouring structure falls under section 6 of the Party Wall etc. Act 1996 — a distance-and-depth test, notices, and an award that generally names the sequence and the monitoring regime. The Act does not extend to Scotland or Northern Ireland, and elsewhere the equivalent duty sits in the building code: the International Building Code covers protection of adjoining property in its chapter on safeguards during construction, as adopted and amended locally. Where people enter the pits, the excavation rules apply on their own terms — OSHA 29 CFR 1926 Subpart P in the United States, BS 6031 with the temporary works procedures of BS 5975 in the United Kingdom.
The engineering follows from the dates. There is a temporary condition — pins cast, the neighbour's excavation open, no permanent prop yet installed — that is usually worse than the finished state, and it is the condition nobody prices because it sits between two contracts. Ask who props the neighbour's excavation, at what stage, and against what. If the answer is that their own base slab and capping beam will do it, then the answer also contains a window before either exists, and somebody needs to have checked this wall for that window rather than for the completed scheme.
What Is Left in Front to Push Back
Passive pressure is the ground in front of a wall resisting the wall's attempt to slide into it. Rankine gives it in two lines: a coefficient Kp = tan²(45° + φ/2) that depends on nothing but the friction angle, and a resultant Pp = ½ Kp γ H² per metre run, which is the area under a triangular pressure distribution over the embedded height H. Because H is squared, the height dominates the answer, and the height is the input people get wrong.
H runs from the final level of the ground in front of the wall down to the underside of the element being pushed — after the neighbour's dig, not before it, and after any allowance the design makes for over-dig, service trenching, or a slab that may one day be broken out and replaced. On this job the honest H is measured from the neighbour's formation to the toe of the pin: four hundred millimetres, not the 3.6 m that separates that same toe from today's yard level. Enter today's ground level instead and the calculator hands back a resistance that will have been excavated away by the time it is needed.
Even the honest figure flatters itself. Passive resistance has to be mobilised, which means the wall has to move into the soil, and the movement required to develop the full value is a serious fraction of the height — far more than a masonry party wall on a strip footing will tolerate before it cracks and tells the neighbour about it. Eurocode 7, BS EN 1997-1, handles this through partial factors and through the requirement to satisfy serviceability as well as strength, and CIRIA C760 is the working reference for how much passive resistance an embedded wall design is entitled to claim. Common practice is to count a fraction of the calculated value, or none of it. A check that only balances with passive counted in full has not been done.
Every field on this calculator that carries a unit follows the measurement switch: the embedment depth and the unit weight both convert what you type, and the friction angle is a plain angle either way. A soil logged at 120 pounds per cubic foot goes in as 120 on the imperial switch, or as about 18.9 kN/m³ on the metric one, and the resultant comes back in the same system it went in.
Run it twice. Once at the passive height you have today, which tells you nothing except the size of what you are about to lose, and once at the height that survives the neighbour's excavation, which is the figure the check has to live with. Then run it a third time with H at its minimum and see whether the wall still stands up without it. If it does not, passive resistance is not a margin on this job — it is the design, and it is a design that depends on soil somebody else has a contract to remove.
- Fix the final level of the ground in front of the wall: the neighbour's formation, not today's yard level.
- Deduct whatever the design gives away below that — over-dig tolerance, a service trench, a slab that may later be broken out.
- Measure H from that level down to the toe of the pin, and use it in place of the retained height behind the wall.
- Take φ and γ for the stratum genuinely in front at that depth, which is frequently not the stratum behind.
- Compute Pp, then apply whatever reduction the design basis allows before it goes anywhere near a sliding sum.
- Repeat with the passive height at its minimum, and read whether the check still passes without it.
Embedment depth measured after the adjacent excavation rather than before it, friction angle and unit weight for the soil actually left in front, and a resultant per metre run that still has to be discounted before it earns a place in the check.
The depth of soil in front of the wall or footing providing passive resistance.
The soil's angle of internal friction.
The soil's unit weight in front of the wall.
Passive pressure resultant
688 lbf/ft
Passive resistance is often unreliable in practice — it requires enough wall movement to mobilize, and can be lost entirely if the soil in front of the wall is later excavated or erodes. Many designers deliberately ignore or heavily discount passive resistance for this reason.
- Rankine passive coefficient (Kp)
- 3
They open the calculator with your figures already in it
Rankine Passive Earth Pressure Calculator: 688 lbf/ft — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
Add the equipment this sizes
This result is a specification — 688 lbf/ft — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.
What this calculation does not cover
- There is no water in this model. Below the water table the soil in front of the wall contributes only its buoyant weight, so the resistance from the soil skeleton is far less than the full unit weight entered here suggests, and the water pressure acting on the same face is a separate term this does not compute. Perched water, seepage and a table that rises after rain are not checked at all.
- Rankine here is the cohesionless case against a smooth vertical wall face with level ground in front of it. There is no cohesion term, no wall friction or adhesion, no allowance for ground that falls away from the toe (which reduces passive resistance), and no layering — a single friction angle and unit weight cannot describe soft clay, mixed fill, or a granular layer over something weaker.
- This is the full theoretical passive resistance with no factor of safety and no mobilisation reduction applied. Passive pressure needs far more wall movement to develop than active pressure does, so the resistance actually available at a deflection the structure can tolerate is a fraction of this figure. Deciding how much of it to count is a design judgement the calculator does not make.
- The whole embedment depth entered is treated as effective passive soil. Nothing is subtracted for a frost-affected or disturbed upper zone, topsoil or paving buildup, or for soil that a future utility trench, re-grade or landscaping in front of the wall would remove.
- This is one force per metre run of wall, not a stability check and not a design. It does not check sliding, overturning, bearing pressure, base heave or global slope stability, does not size or reinforce the wall or footing, and includes no load factors and no seismic case. Passive resistance is one term in a check that a qualified engineer has to complete against site-specific geotechnical data.
Sliding Is a Sum, and Passive Is Its Smallest Term
The resultant that calculator returns is one line of a longer sum, and quoting it as a sliding check is the commonest way this arithmetic gets abused. On one side sits everything driving the wall sideways: active pressure from the retained ground behind it, surcharge from whatever stands on that ground, and water where there is a water table. On the other sits base friction under the pins, adhesion where the founding stratum is cohesive, passive resistance in front, and any prop or slab that genuinely exists at the moment being checked.
Water deserves a sentence of its own, because it is where the arithmetic quietly changes character. Below a water table the soil weight inside every earth pressure term becomes the buoyant weight, roughly half, and hydrostatic pressure is then added separately on both faces. Doing the first without the second, or the second without the first, produces a worse answer than doing neither, and the error has the wrong sign in one of the two cases.
Note also what a per-metre resultant is: a force per metre run of wall. Turning it into a total means multiplying by the length over which that height of soil genuinely exists. Where the neighbour's excavation steps, or where a return buttresses part of the wall that the straight run does not have, that length is not the full twelve metres and treating it as such flatters the result.
Nothing on this site assembles that sum for an underpinned party wall, and the omission is deliberate rather than an oversight. The individual terms are each a defensible piece of arithmetic; the combination is a design decision about which of them may be counted, at what partial factors, in which of several distinct construction stages — and that decision is the engineer's. The stability tool listed below assembles a cut-down version of it for a conventional retaining wall — active pressure, wall self-weight and base friction, with no surcharge, water, adhesion or passive term in it at all — on a different geometry with a different load path, and it is worth opening to see the shape of the check rather than to answer this one.
| Term | Side of the sum | What settles it |
|---|---|---|
| Active pressure behind the wall | Driving | Retained height and soil properties, and whether the wall can rotate enough for the active state to develop at all |
| Surcharge on the retained ground | Driving | What stands there — a building, a road, stored spoil, a crane pad — and whether it is there for the duration |
| Water pressure | Driving on both faces | Groundwater level and drainage; hydrostatic pressure is indifferent to which side of the wall it is on |
| Base friction under the pins | Resisting | Vertical load arriving at formation, and the interface friction for concrete cast directly against ground |
| Base adhesion | Resisting | Cohesion of the founding stratum, normally taken as a fraction of the measured value |
| Passive resistance in front | Resisting | The height left after the adjacent excavation, and how much of the computed value the design basis permits |
| Props, slabs and capping beams | Resisting | Whether they physically exist at the moment being checked, not whether they appear on the finished drawing |
Pricing the Visit
Back to the ledger. The dig is small, the concrete is small, and neither of them is the cost. The cost is the number of times a gang has to arrive, work a hole they can barely turn around in, and leave — and that number is set by the sequence rather than by the quantity.
A hit-and-miss sequence carries a concurrency limit written into it: how many bays may stand open at once and how far apart they must be. That limit, together with the strength a pin must reach before the bay beside it may be opened, is what turns twelve bays into a programme measured in weeks. Both are temporary works decisions under BS 5975, and both should be read off the drawing before a single rate is written, because a one-in-four sequence and a one-in-five sequence are different jobs at identical quantities.
Then count visits per bay instead of cubic metres per bay, and price the ones that normally go unpriced: the return trip for dry-packing, the monitoring readings taken between bays, and the standing time when a bay cannot be opened because its neighbour has not yet made strength. Add the survey monitoring the party wall award will very likely require, which runs across the whole sequence and does not stop when the last pin is cast.
- Open the bay in the order the temporary works drawing gives, never the order that suits the gang's day.
- Trim to formation and have the founding stratum inspected against what the boreholes promised.
- Blind if specified, shutter the face, and pour the pin to the level that leaves the specified gap.
- Strike, and leave the bay alone until the pin has the strength the sequence names.
- Return and ram the dry-pack from both faces until the joint will take no more.
- Take the monitoring reading, then release the next bay in the sequence.
The lines this job is actually bought on
A sequenced underpin splits into three things bought separately: a hole, the visits needed to work it, and the resistance still standing in front of the wall once the neighbour has finished digging.
- Standard bay, dug — Pit length by pit width including the toe projections, by depth from the underside of the existing footing down to formation.
- Exception bays — Corners, returns and any bay crossed by a live service, carried as their own lines and never folded into an average bay.
- Spoil, loose — Bank volume plus the swell figure from the ground investigation; all of it leaves site, because the hole is refilled with concrete.
- Concrete and dry-pack — Pin volume up to the specified gap below the old footing, then the gap itself as a separate return visit days later.
- Passive height after the adjacent dig — Measured from the neighbour's formation to the toe of the pin — the height the sliding check has to survive, not today's.
- Visits, not cubic metres — Dig, shutter, pour, strike, dry-pack and monitor, multiplied by bays and constrained by the concurrency the sequence allows.
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.