The job
Modelled, not recorded. Every figure on this page is re-run through the calculator it names whenever the site is built; the estimate is worked, but no job was carried out, so the last section gives the mechanism of each likely error rather than a measured overrun.
A garden wall is usually costed as a number of bricks, and on a slope the brick count is one of the last figures to settle. The fall decides how many times the footing steps; the steps decide how much concrete goes into the laps, how deep the trench runs on average and how many courses stand in each section of brickwork; and the spoil that has to leave is not the trench but the part of it the concrete and the buried brickwork take up, because the rest goes back. This walkthrough runs the calculators in that order, because each one takes a figure an earlier one produced.
The job: a freestanding wall 10 m (32 ft 10 in) long, running straight down a garden that falls 900 mm (2 ft 11 in) along its line. It is one brick thick — 215 mm (8.5 in), two leaves bonded in English garden-wall bond — in UK standard 215 × 102.5 × 65 mm (8.5 × 4.0 × 2.6 in) bricks on 10 mm (0.4 in) joints, standing on an unreinforced concrete strip 600 mm wide and 225 mm thick (23.6 × 8.9 in). Its brickwork stands 1.2 m (3 ft 11 in) out of the ground on average, under a twice-weathered precast coping. The bottom eight courses are engineering brick, which keeps ground water out of the facing work above without the slip plane a sheet damp-proof course puts through the wall. The back garden has no vehicle access, so the concrete is mixed beside the trench and the spoil goes by barrow to a skip at the front.
THE FALL IS THE MEASUREMENT EVERYTHING ELSE HANGS FROM. Nine hundred millimetres (2 ft 11 in) over ten metres (32 ft 10 in) is four lifts of three courses, 225 mm (8.9 in) each, and taking all four as steps turns the trench into a sawtooth: level along each bay while the ground keeps falling, so one end of every full bay is a whole step deeper than the other. Take the fall from a general impression of the garden instead of from levels along the wall line, and the concrete, the dig, the skip and the coursing all move with the error.
ONE BRICK THICK MEANS TWO LEAVES. The brick calculator counts a single leaf laid flat, so this wall goes into it as 20 m (65 ft 7 in) of half-brick face — both leaves laid end to end. Reading its answer for a 10 m (32 ft 10 in) wall as the order is the quickest way to buy half a garden wall. Its mortar line has the same blind spot one level down: it counts the joints of two separate leaves, and not the 10 mm (0.4 in) of mortar between them.
WHAT THIS PAGE IS, AND WHERE THE SITE RUNS OUT. Every quantity to be ordered comes from the calculator linked at its step, fed with figures worked from the job's own geometry in that step's text, and nothing was built: the job is modelled. Five gaps are stated rather than filled. No calculator here checks whether a freestanding wall of this height and thickness stands up to the wind where it is built; the published tables for freestanding walls decide that, and whether it needs piers, and this example assumes they allow a plain one-brick wall at this height. No calculator sizes movement joints in clay brickwork — the masonry control joint page is for concrete block and says so — and a 10 m (32 ft 10 in) run is the length at which the brick maker's movement figure decides whether a joint is needed at all. The mortar calculator works the American ASTM C270 proportions, so its Type S, at the calculator's midpoint lime, stands in for a British 1:½:4½. The coping calculator is written for parapets: its length arithmetic holds, its advice to fall toward a roof does not. And planning is outside all of them: in England the Town and Country Planning (General Permitted Development) (England) Order 2015 allows a lower wall beside a highway used by vehicles — one metre (3 ft 3 in) — than elsewhere, and local conditions and directions can change either figure, so this wall is assumed to stand on a boundary away from the road, with the planning authority asked before the trench is dug.
What was measured, and how
The wall line and its length on plan
10.0 m (32 ft 10 in), running straight down the fall
Pegged at both ends with a string line strung between them at a fixed height, then measured horizontally along the line rather than down the ground. The calculators take plan length; a tape laid on a falling garden reads slightly long and puts the step positions out when they are marked off it.
The fall along that line
900 mm (2 ft 11 in) over the 10 m (32 ft 10 in), an even 1 in 11.1 (9% along the wall)
Levelled with a laser and staff at every metre along the string, not taken from the garden's general fall or from one reading at each end. The steps follow the ground under the wall, and a hump or a hollow between the ends would move them; only readings along the line show one.
The ground and the minimum founding depth
Firm, stony subsoil at both ends; 450 mm (17.7 in) to the underside of the concrete taken as the minimum for this example
A trial hole at each end of the line, dug through the topsoil into undisturbed subsoil. Firm, non-shrinkable ground with no tree within influencing distance is what lets the depth stay shallow; clay or a nearby tree would push it far deeper. The minimum is met at the shallowest point of every bay, not on average.
The strip's section
600 mm wide × 225 mm thick (23.6 × 8.9 in), unreinforced, poured against the trench sides
Width and thickness settled before digging, because the trench is dug to them and the concrete goes in against its sides. On a freestanding wall the width is there to stop the wall rotating rather than to spread its weight, and the thickness is set equal to the step so that no step is taller than the concrete is thick.
Coursing, from a sample of the chosen brick
215 × 102.5 × 65 mm (8.5 × 4.0 × 2.6 in) on 10 mm (0.4 in) joints, a 225 × 75 mm (8.9 × 3.0 in) module; 20 courses, 1.5 m (4 ft 11 in), from concrete to coping in every section
Ten bricks laid out dry with 10 mm (0.4 in) gaps and measured as one run, and a gauge rod marked off at 75 mm (3.0 in) courses. A data sheet gives the nominal size, not what arrives on the pallet, and a module a millimetre or two long moves both the count and where each course meets a step.
Height out of the ground, at both ends of each section
About 1.09 to 1.32 m (3 ft 7 in to 4 ft 4 in) of brickwork clear of the ground along each section, least at its uphill end and most over the lap at its downhill end; 1.20 m (3 ft 11 in) on average, and 1.16 m (3 ft 10 in) at both ends of the wall, with the coping above
Measured from the finished ground beside the wall at the uphill and the downhill end of a section, never at one point. The courses run level while the ground under them keeps falling, so a single reading hides a difference of a whole step between the two ends of the same panel; and the last 450 mm (17.7 in) of each section stands on a lap, where the concrete is a step higher than under the rest of it.
The takeoff, in order
Each step needs something from the one before it, which is why the order is part of the answer.
Divide the fall into steps the brickwork can follow
- Needs
- The 10 m (32 ft 10 in) run on plan and the 900 mm (2 ft 11 in) of fall levelled along the string, with the strip's 225 mm (8.9 in) thickness and a step of three 75 mm (3.0 in) brick courses, so the bricklayer never has to make up height in a thickened bed joint.
- Produces
- Four steps 2.5 m (8 ft 2 in) apart, the fall dividing exactly. The calculator counts the steps; where they go is a choice. Here the run is laid out as a half bay of 1.25 m (4 ft 1 in) at each end with three full bays between, which gives an average dig of the 450 mm (17.7 in) minimum plus half a step, 562.5 mm (22.1 in), and founds both ends of the wall at that depth, so they stand the same height out of the ground. Three steps with four full bays would dig the same average with one lap and one stop end fewer — about 0.06 m³ (2.1 ft³) less concrete — but would found the uphill end a whole step deeper than the downhill one, and the wall's two ends would stand a step apart in height. Each step laps 450 mm (17.7 in) — twice its height, more than both the strip's thickness and the 300 mm (11.8 in) floor in the Approved Document A rule the calculator applies. A garden wall sits outside the Building Regulations in most domestic cases; the rule is borrowed because a step without a lap is where the wall above it cracks, inspected or not.
Result4 steps of 225 mm (8.9 in), 2.5 m (8 ft 2 in) apart, each lapped 450 mm (17.7 in)
Stepped Foundation Calculator (Steps, Bays and Overlaps on a Slope)Quantify the strip, laps included
- Needs
- The four steps and the 450 mm (17.7 in) lap from step one, entered as length: over each lap the lower strip carries on beneath the upper one, and because the step equals the strip's thickness each lap is one more 450 mm of the same 600 × 225 mm (23.6 × 8.9 in) section, so the 10 m run plus four laps is 11.8 m (38.7 ft). The trench is the formwork, which sets the waste.
- Produces
- 1.75 m³ (2.29 yd³) with 10% on a base of 1.59 m³ (2.08 yd³), of which the four laps are 0.24 m³ (0.32 yd³) — concrete the stepping calls for rather than waste, and the line a straight 10 m take-off leaves out. This is the volume to be placed; the next step turns it into what has to be mixed, and the base figure comes back at the spoil step, because every cubic metre of it is trench that never gets its soil back.
Result1.75 m³ (2.29 yd³) of concrete, 1.59 m³ (2.08 yd³) before waste
Continuous Footing / Grade Beam Volume CalculatorBatch the concrete for a mixer beside the trench
- Needs
- Step two's 1.75 m³ (2.29 yd³) multiplied by one and a half, the working allowance the calculator's own help gives for concrete mixed on site, because its ratio divides loose dry material that closes up when mixed: 2.63 m³ (92.8 ft³) of dry batch at 1:2:4.
- Produces
- 23 bags of cement, with 0.75 m³ (26.5 ft³) of sharp sand and 1.50 m³ (53.0 ft³) of 20 mm (3/4 in) gravel. It is a proportion, not a designed mix, and the calculator says so. The 1:2:4 is a lean site proportion for a plain, unreinforced strip — one part cement in seven, against one in six at the calculator's 1:2:3 default — and it carries no strength class; ordered ready-mixed instead, the strip would be specified by designation, and the step guide gives GEN1 as the BS 8500 designated concrete for unreinforced strips in non-aggressive ground.
Result23 × 25 kg bags of cement (14 × 94 lb sacks in US stock)
Concrete Mix Ratio CalculatorCount the bricks for both leaves
- Needs
- Step one's stepping, which lets the top of the wall step with the footing so that every section carries the same 20 courses — 1.5 m (4 ft 11 in) from concrete to coping — and the two leaves of a one-brick wall, entered as 20 m (65 ft 7 in) of half-brick face because the calculator counts one leaf.
- Produces
- 2,045 bricks with 15% on 1,778, at 59 to the m² (5.5 per sq ft) of each leaf. The bottom eight courses of every section are engineering brick and the top twelve facing — two-fifths and three-fifths of the count, ordered as two lines. Its mortar line counts the joints of the two leaves as 42 bags of 25 kg premix (29 × 80 lb bags in US stock) and, by its own limitations, leaves out the collar joint; this job mixes its own mortar, in the next step.
Result2,045 bricks (1,778 before waste)
Brick CalculatorBatch the mortar from the joint volume
- Needs
- Step four's joint geometry, taken past its premix line: each 225 × 75 mm (8.9 × 3.0 in) module less its 215 × 65 mm brick leaves 2,900 mm² (4.5 in²) of joint, and across a 102.5 mm (4.0 in) leaf for 1,778 bricks that is 0.53 m³ (18.7 ft³). The wall is 215 mm thick and its two leaves 205 mm, and the 10 mm (0.4 in) between them is mortar too — the collar joint in the stretcher courses, the same volume in the header courses' full-depth joints — 0.15 m³ (5.3 ft³) over the wall's 15 m² (161 sq ft) of face. Together 0.68 m³ (24.0 ft³), entered before any waste.
- Produces
- 0.75 m³ (26.4 ft³) of building sand — the calculator takes wet yield as the sand volume — with 11 bags of cement (7 × 94 lb sacks in US stock) and 0.068 m³ (2.4 ft³) of hydrated lime. Type S at three parts sand to each part of cement and lime together, with the calculator's midpoint lime, is 1 : 0.375 : 4.1 by volume; its note writes the sand as 3 because it counts it against the binder. The top of the Type S lime band at the same sand is exactly the British 1:½:4½, which takes the same sand and slightly less cement. Its note ties Type S to walls where flexural bond strength matters, which on a freestanding wall is all of it.
Result0.75 m³ (26.4 ft³) of building sand, with 11 × 25 kg bags of cement
Mortar Mix Calculator (ASTM C270 Types M, S, N, O)Turn what the wall displaces into a loose volume of spoil
- Needs
- Step two's 1.59 m³ (2.08 yd³) of concrete before waste, and the brickwork of step four that stands below ground: 215 mm (8.5 in) wide, with the top of the concrete an average 297 mm (11.7 in) down once the laps have raised it a step over 450 mm at each, 0.64 m³ (0.84 yd³) along the 10 m. Together 2.23 m³ (2.92 yd³) of the 3.375 m³ (4.41 yd³) trench — 10 m by 600 mm by step one's 562.5 mm average dig — and the other 1.14 m³ (1.50 yd³) goes back either side of the wall.
- Produces
- 2.79 m³ (3.65 yd³) of loose spoil to leave at a 25% swell — the figure the skip is filled with, and the volume barrowed round the house. Sized on the whole trench instead, all 3.375 m³ would have been bulked and a skip booked a size too big. The share that goes back is heaped on a sheet beside the trench, a quarter bigger than it was in the ground, until it is rammed back in against the brickwork.
Result2.79 m³ (3.65 yd³) of loose spoil to leave, from 2.23 m³ (2.92 yd³) displaced
Soil Swell & Shrinkage Haul Volume CalculatorCheck the skip on weight as well as volume
- Needs
- Step six's loose 2.79 m³ (3.65 yd³) rather than the whole trench, and the waste type — soil — because spoil at 1,500 kg/m³ (2,528 lb/yd³) reaches a skip's weight limit long before the same volume of light waste would.
- Produces
- 4.18 tonnes (4.6 US tons) of soil in 2.79 m³ (3.65 yd³), which fits a 4-yard skip — 3.06 m³ (4.00 yd³) — by volume, with 0.27 m³ (9.5 ft³) to spare. Against the calculator's default 8-tonne (8.8 US ton) limit, kept here as a placeholder, the load is volume-bound. Hire firms set their own limits and often restrict soil to smaller skips or a lower fill, so the firm's figure is the one to enter: below 4.18 t the calculator turns the load weight-bound and counts a second one.
Result2.79 m³ (3.65 yd³) of soil, weighing 4.18 tonnes (4.6 US tons)
Skip & Dumpster Size CalculatorMeasure the coping, with its stop ends
- Needs
- The 10 m (32 ft 10 in) run and the four places step one makes the top step down, since each section takes its own lengths of coping and each higher section ends over the one below it in an exposed end that has to be finished.
- Produces
- 11.0 m (36.1 ft) of twice-weathered coping with 10% for breakage, bedded over a damp-proof course. The length arithmetic is all that carries over from a parapet. The six stop ends — one at each end of the wall and one at each step — are units the calculator leaves out, and they are the pieces most often missing from the order.
Result11.0 m (36.1 ft) of coping, plus six stop ends
Parapet Coping Cap Linear Footage Calculator
The figures
| Step | Calculator | Figure |
|---|---|---|
| Divide the fall into steps the brickwork can follow | Stepped Foundation Calculator (Steps, Bays and Overlaps on a Slope) | 4 steps of 225 mm (8.9 in), 2.5 m (8 ft 2 in) apart, each lapped 450 mm (17.7 in) |
| Quantify the strip, laps included | Continuous Footing / Grade Beam Volume Calculator | 1.75 m³ (2.29 yd³) of concrete, 1.59 m³ (2.08 yd³) before waste |
| Batch the concrete for a mixer beside the trench | Concrete Mix Ratio Calculator | 23 × 25 kg bags of cement (14 × 94 lb sacks in US stock) |
| Count the bricks for both leaves | Brick Calculator | 2,045 bricks (1,778 before waste) |
| Batch the mortar from the joint volume | Mortar Mix Calculator (ASTM C270 Types M, S, N, O) | 0.75 m³ (26.4 ft³) of building sand, with 11 × 25 kg bags of cement |
| Turn what the wall displaces into a loose volume of spoil | Soil Swell & Shrinkage Haul Volume Calculator | 2.79 m³ (3.65 yd³) of loose spoil to leave, from 2.23 m³ (2.92 yd³) displaced |
| Check the skip on weight as well as volume | Skip & Dumpster Size Calculator | 2.79 m³ (3.65 yd³) of soil, weighing 4.18 tonnes (4.6 US tons) |
| Measure the coping, with its stop ends | Parapet Coping Cap Linear Footage Calculator | 11.0 m (36.1 ft) of coping, plus six stop ends |
The waste factors, and why these ends of the ranges
| Material | Applied | Why |
|---|---|---|
| Concrete for the strip | Double the calculator's default, with the laps entered as length rather than as waste | The calculator's 5% default is for a straightforward pour. Here the trench is the formwork, so every scallop the spade leaves, every clod that falls in overnight and the bottom trimmed on the morning of the pour add concrete to a section the arithmetic treats as a clean 600 × 225 mm (23.6 × 8.9 in) prism; 10% carries that. The four laps are kept out of the percentage and entered as 1.8 m (5 ft 11 in) of extra length, because they are concrete the stepping requires and a bigger percentage would hide them from whoever checks the order. |
| Dry batch for the concrete | The calculator's own half-again allowance from placed to batched volume, applied after the waste | The ratio divides loose dry material, and mixed and placed that batch fills roughly two thirds of its dry volume, which is why the calculator's help says to batch about one and a half times the pour. It is a working rule rather than a yield, and it moves with the water the mix takes; applying it after the 10% means the allowance for the trench is batched as well. |
| Bricks | Toward the top of the calculator's range | 15% rather than the 10% default. A garden wall is seen from both gardens, so a chipped face is a reject whichever side it would have faced; the two wall ends and the four places the top steps down are six exposed ends, each taking closers cut from whole bricks in a one-brick bond; and engineering and facing brick are two separate orders, each rounded up to whole packs. |
| Mortar | The calculator's default for droppings and board waste, kept apart from the joints the geometry misses | 10% covers what falls off the board and the end of a batch that has stiffened past use. It is not stretched to cover the bed under the coping or filled frogs, because those are volumes of joint, not waste, and belong on the order as their own lines — which is also why the 10 mm between the two leaves is worked into the joint volume in step five rather than left to the percentage. |
| Coping | Double the calculator's default, for breakage rather than cutting | 10% against the calculator's 5%. Precast copings chip at the arrises and crack if they are carried flat across a rough garden on a barrow, and a unit chipped along its drip or throat no longer throws water clear of the faces, so it is a reject rather than a piece to hide. The stop ends are ordered as counted units on top of this, not out of it. |
| Spoil | The middle of the band the calculator gives for common earth | 25% sits in the 20-30% the calculator quotes for ordinary soil. It is the change from bank to loose volume rather than a waste allowance; a sticky clay would bulk more and a clean gravel less, and trial holes that find either should change it before the skip is booked. |
Where this estimate is most likely to be wrong
Spoil and the skip
usually underThe skip is sized on the designed section: the concrete before its allowance, and the brickwork below ground. The trench a spade cuts is wider and deeper than that section, and every bit of over-dig is soil that leaves and concrete that takes its place. Backfill rammed by hand against new brickwork seldom goes back as tight as it came out, so part of the returned share stays on the surface, and the 4-yard skip has little room for either.
Narrow it by: Measuring the trench as dug in the first bay against its 600 mm width, and asking the hire firm before booking whether a larger skip can be swapped in if the first one fills.
Concrete in the trench
usually underThe calculator measures a clean 600 × 225 mm (23.6 × 8.9 in) prism, and an earth trench is never one. The sides are cut by spade and bulge where a stone came out, the bottom is trimmed on the day and ends up below the pegs, and any soft pocket found in the bottom is dug out and filled with concrete. Each of those adds at every bay, and the allowance was set before any of them were seen.
Narrow it by: Checking the width at the top and bottom of the trench and the depth to the level pegs in every bay the evening before mixing starts.
Mortar
usually underThe joint volume is geometry, and it assumes solid bricks and nothing on top. It leaves out the bed under the coping and any frogs in the bricks, which in a wall laid frog up are filled with mortar course by course, and perforated engineering bricks take some mortar into their holes. Each is mortar the calculation does not see, and none of it is inside the allowance for droppings.
Narrow it by: Checking whether the chosen bricks are solid, frogged or perforated, and adding the coping bed as its own line before sand is ordered.
Brick count
either wayThe count assumes plain panels with nothing added. If the freestanding-wall tables for the site's wind exposure call for piers, every pier adds bricks and a wider footing under it, and neither is in these figures. Against that, the allowance for breakage and closers was set toward the top of the range, and on a wall laid carefully from a clean delivery part of it is never cut into.
Narrow it by: Checking the height and thickness against the published freestanding-wall tables for the site before ordering, and dry-bonding the first course along the whole run.
Cement and aggregate for the footing
either wayThe half-again step from placed to batched volume is a working rule, not a yield test. A wetter mix yields more and a stiff one less, and damp sand bulks, so a shovel of it carries less sand than a dry one. Buying the aggregate as all-in ballast changes the proportions again, because the ballast's own sand content is fixed by the quarry rather than by the ratio.
Narrow it by: Checking how much trench the first few mixer loads fill against the volume they were batched for, and adjusting before the rest of the pour is mixed.
Time and weather rather than material
usually underThe bricks and the concrete are the visible part of the job. Levelling the line, digging a stepped trench by hand, mixing well over a cubic metre and a half of concrete a barrow at a time and laying a wall that has to look right from both sides are all slow, and fresh brickwork with an open top has to be sheeted every night until the coping is bedded.
Narrow it by: Programming the dig, the pour and the brickwork as separate days with a forecast check before each, and having sheets on site from the first day.
Tools this job needs
Frequently asked questions
- How many bricks do I need for a garden wall?
- For this one-brick wall, 10 m (32 ft 10 in) long and 20 courses from footing to coping, the calculator counts 1,778 bricks before waste and 2,045 with 15% added. That is two leaves of 15 m² (161 sq ft) each at about 59 bricks to the m² (about 5.5 per sq ft). A half-brick wall would take half as many, but at 1.2 m (3 ft 11 in) out of the ground a single leaf leans on its mortar bond alone to stay up.
- How much sand and cement do I need for a garden wall?
- Two mixes. The footing's 1.75 m³ (2.29 yd³) of concrete, mixed on site at 1:2:4, takes 23 × 25 kg bags of cement (14 × 94 lb sacks in US stock), 0.75 m³ (26.5 ft³) of sharp sand and 1.50 m³ (53.0 ft³) of gravel. The brickwork's 0.68 m³ (24.0 ft³) of joints, collar joint included, takes with a tenth added 0.75 m³ (26.4 ft³) of building sand, 11 more bags of cement (7 × 94 lb sacks) and 0.068 m³ (2.4 ft³) of hydrated lime.
- How do you build a garden wall on a slope?
- By stepping the footing in whole brick courses and letting the top of the wall step with it. Here 900 mm (2 ft 11 in) of fall over 10 m (32 ft 10 in) is taken as four 225 mm (8.9 in) steps, 2.5 m (8 ft 2 in) apart, each lapped 450 mm (17.7 in). The trench is dug so the shallowest point of every bay still reaches the founding depth, and every section is the same 20 courses.