The clause goes out eighteen months before the tenant does
A speculative distribution unit is specified for nobody in particular. The agent has a floor area, an eaves height and a view about the sort of occupier the estate attracts, and from that you have to write a slab section. Nothing in the pack tells you whether the building will end up holding counterbalance trucks wandering wherever the pallets are, or a wire-guided very narrow aisle fleet running the same two wheel lines to thirteen metres, all day, for fifteen years. Those are not the same floor. The concrete is nearly identical; the surface tolerance is not, and the tolerance is the expensive half.
It is also the half that is only cheap while the slab is still on paper. Bringing a finished twelve-thousand-square-metre floor up to a defined-movement tolerance by grinding costs real money and real programme, and it happens at the worst possible moment, with racking either installed or waiting on a lorry. So the slab section has two jobs at once. It has to commit to a floor that is buildable at a sensible price for the letting the agent expects, and it has to be explicit about what it does not cover, so that when the VNA tenant does appear the conversation is about a priced variation rather than a defect.
Free movement or defined movement is a decision about the truck
The vocabulary trips people up because the same document uses the word movement for two unrelated things. In Concrete Society Technical Report 34, Concrete Industrial Ground Floors, a free movement area is one where the materials handling equipment goes wherever it likes on unguided paths. A defined movement area is a very narrow aisle where the truck is held on rails or on a buried wire and its wheels track the same two lines for the life of the building. Separately, the same report classifies joints as free movement or restrained — that is a detail at the joint, not a regime for the aisle. A specification that writes free movement without saying which of the two it means will be read both ways inside one tender, and the two readings do not cost the same.
What follows from the traffic is what gets measured. Random traffic is measured statistically across a whole placement. American practice does this with F-numbers to ASTM E1155, an FF for flatness derived from curvature over a short interval and an FL for levelness derived from elevation differences over a longer one, with the class recommendations sitting in ACI 302.1R and the tolerance rules in ACI 117 — which is also where the requirement to state both an overall value for the placement and a minimum local value for any single test section comes from. TR 34 does the same job through its free movement classes. Neither system says anything about the two lines a guided truck actually runs on, because neither was built to.
Defined movement is surveyed along the wheel tracks instead. Two quantities matter there and neither appears in a random-traffic survey: the difference in elevation between the two tracks at the same station, which tips the mast sideways and is amplified by whatever the forks are carrying at height, and the rate at which elevation changes along a single track, which is what makes the mast whip as the truck moves. TR 34 handles this with its defined movement classes. American practice splits two ways here, and it is worth knowing which one a specification means: F-min is a proprietary defined-traffic number that has to be surveyed with a profileograph set up for the specific truck, and it is explicitly not obtainable from the F-number method that gives you FF and FL, while ASTM E1486 is the open standard for the same job, setting waviness, wheel path and levelness criteria along the tracks. An FM class and a DM class are not points on one scale, and quoting one against the other is a category error rather than a conversion anybody can do.
The practical move in the specification is to pick the regime per area rather than per building. Most distribution units are a random-traffic floor everywhere except a VNA block, and that block gets a tighter class, usually poured in strips laid out to the aisle grid. Draw the boundary on the slab layout drawing. If the VNA block has not been located because there is no tenant, say that in the clause, state the class the general floor is being built to, and state what would have to happen to lift a defined area later.
| Free movement / random traffic | Defined movement / defined traffic | |
|---|---|---|
| Truck | Counterbalance and reach trucks, unguided paths | VNA truck on wire or rail, fixed wheel tracks |
| Surveyed over | The whole placement, as a statistical population | The two wheel tracks and the difference between them |
| US route | FF and FL to ASTM E1155; classes in ACI 302.1R; tolerance rules in ACI 117 | F-min by truck-specific profileograph, or ASTM E1486 waviness and wheel path |
| UK and European route | TR 34 free movement classes FM1 to FM4, chosen by lift height and side-shift | TR 34 defined movement classes DM1 to DM3, chosen by top beam height |
| Shows up as a problem | A floor that rides rough and wears at every joint | A mast that sways at height and a truck that has to slow |
| Remedy after the event | Grinding, priced by the square metre over a large area | Grinding two tracks, after the racking has fixed where they are |
A class with no survey clause attached is a wish
Say who surveys, by which method, and when. Timing is the item most often dropped and the one that decides the argument, because F-numbers describe a freshly finished floor and are taken within seventy-two hours of the placement, before the slab has had time to lift at its edges. Survey the same floor a month later and it reads worse — that is curling, which is a property of drying concrete rather than a finishing defect, and a specification that leaves the window open invites a dispute nobody can settle with a measurement. A defined-movement floor pulls the other way: the tracks are surveyed for the truck, so they have to be re-checked once the racking is set and the aisle position is final. A perfectly executed survey of the wrong two lines proves nothing at all.
Then say what happens when a placement misses. An honest clause names the remedy, names who carries it in which circumstances, and states whether the corrected area is re-surveyed and to what. Leave that out and the default remedy is a fortnight of correspondence during handover. One more document will arrive without being invited: the racking installer works to BS EN 15620, which sets the tolerances, deformations and clearances an adjustable pallet racking installation has to achieve, and it carries its own expectations of the floor. It will not automatically agree with the flooring class you wrote, and finding that out on site is expensive.
Four loads, and only one of them is on the letting particulars
The brief gives a uniformly distributed load over the storage area and stops. UDL is the least demanding of the four loads a warehouse floor carries and the one least likely to govern anything. The other three are point loads under rack uprights, line loads under back-to-back rack runs, block-stacked goods and mezzanine edge beams, and the wheel loads from the trucks themselves — which are not the static axle load but that load with an impact allowance on it, because a laden reach truck crossing a joint is a dynamic event.
They arrive in incompatible units because they arrive from different desks. The geotechnical report gives an allowable bearing pressure in kPa, qualified as allowable or ultimate and usually tied to a settlement limit. BS EN 1991-1-1 puts storage areas in their own imposed load category with characteristic values in kN per square metre, which is the same unit as kPa written differently. The racking supplier, if the rack or the tenant is American, gives leg loads in pounds, baseplate dimensions in inches and floor loading in psf. Convert each line separately and label what it is, because a UDL, a soil bearing pressure and the contact pressure under a steel plate are all pressures and no two of them can be compared with each other.
One sanity check is worth building into the habit, and it is a check on the unit rather than on the engineering. A domestic floor live load is a couple of kPa. A warehouse UDL is commonly ten to twenty-five times that, so tens of kPa. An allowable soil bearing pressure on a competent formation is larger again but not dramatically so — a hundred to a few hundred kPa is ordinary — which means a UDL and an allowable bearing pressure sitting within a factor of two or three of each other is a normal state of affairs and proves nothing either way. What should stop you is a figure roughly twenty times or roughly a thousand times off its neighbours, because those are the two conversions that get dropped: a kPa value retyped as psf is out by about twenty-one, and a kN per square metre read as an N per square millimetre is out by a thousand.
The geotechnical allowable, the imposed load category and the racking supplier's floor loading arrive from three places in two systems, and the slab section has to state them all in one before any of them can be compared with each other.
The pressure in kilopascals, as written in the geotechnical report or metric load schedule.
Bearing pressure
3,133 psf
Converted using an exact defined factor of 20.88543423315013 psf per kPa. The digits convert; the report's allowable-versus-ultimate wording and its settlement limit do not.
- Conversion factor applied
- 20.89 psf per kPa
They open the calculator with your figures already in it
kPa to psf Bearing Pressure Calculator: 3,133 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 — 3,133 psf — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.
A metric geotechnical report lands on a desk where the footing schedule is worked in pounds per square foot, and 150 kPa has to become something a US spreadsheet can size a pad from — about 3,133 psf. Two things travel badly. First, the report will write kN/m² as readily as kPa; they are the same unit exactly, so that part needs no arithmetic at all. Second, the figure is qualified — allowable or ultimate, net or gross, and usually tied to a settlement limit at an assumed footing width. The conversion carries the digits and none of the qualification, so read the sentence around the number before it enters a design. And keep psf clear of psi: they differ by a factor of 144.
One rack leg, and the three checks it sets off
A loaded upright frame in a high-bay unit delivers its whole share of the bay through a baseplate about the size of a paperback. That concentration is what makes a warehouse floor a different structure from a car park deck, and it triggers three checks that fail in three different ways and are governed by three different things.
The first is punching shear at the perimeter of the baseplate — the leg pushing a cone of concrete down through the slab. It turns on the plate contact area and the effective depth, and TR 34 checks it using the punching provisions of BS EN 1992-1-1 on control perimeters set out from the loaded area. A small plate on a thin slab fails here long before it fails anywhere else. It is also the check most sensitive to a detail that appears on no drawing: whether the plate bears flat, on a grout pad, or on a handful of packing shims. A plate sitting on four shims has a fraction of the contact area the schedule assumed, and the check was never done for that.
The second is flexural, and it is not a single number. TR 34 reproduces the Meyerhof yield-line expressions for a point load on a ground-bearing slab, and the capacity depends on where the load lands: a leg in the middle of a panel carries substantially more than the same leg at a free edge, and more again than one at a corner. Legs also interact, which is why the report treats single, dual and quadruple load configurations separately — two uprights a few hundred millimetres apart share a failure mechanism, and four back-to-back legs share a worse one. This is the arithmetic behind the site rule that a run of uprights sitting along a construction joint can fail a slab that passes everywhere else.
The third check reaches past the slab entirely, and it is the one people forget because it does not feel like a floor problem. To the ground underneath, a block of high-bay racking is a large and extremely heavy pad foundation. The slab spreads each individual leg, but it cannot spread the aggregate load of an aisle-and-rack module over anything wider than itself. Where the formation is soft, or where a piled slab was ruled out on cost early and never revisited, the average pressure that racked footprint delivers has to be set against the allowable bearing in the geotechnical report before any of the local checks are worth doing.
Treat one rack-and-aisle repeat as a pad footing — its plan area and the total load standing on it — and compare the average pressure against the report's allowable value. That is the global check only; the punching and yield-line checks above are separate calculations this does not stand in for.
The total load carried by the footing.
The footing's length in plan.
The footing's width in plan.
The soil's allowable bearing capacity, from a geotechnical report.
Applied bearing pressure
2,660 psf
The pressure this footing puts on the ground is below the allowable bearing pressure shown with it — you entered it from a geotechnical report. Being under the allowable pressure is not the whole ground question: settlement, groundwater and the footings alongside are all untouched here.
- Footing area
- 42.25 ft²
- Allowable bearing pressure
- 3,132.82 psf
- Safety margin (allowable / applied)
- 1.18
They open the calculator with your figures already in it
Footing Soil Bearing Pressure Checker: 2,660 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 — 2,660 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
- BEARING CAPACITY IS NOT SETTLEMENT. A footing can sit comfortably inside the allowable pressure and still settle more than the structure will tolerate, and on a compressible clay the settlement check is usually the one that governs. Passing here is not permission to stop.
- Assumes the load is concentric and the pressure uniform. Any moment or eccentricity tilts the distribution, and once the resultant leaves the middle third the footing lifts along one edge and the peak pressure climbs far above the average this reports.
- The allowable pressure entered must already carry its geotechnical factor of safety. Entering an ultimate bearing capacity instead over-credits the ground by roughly a factor of three, and nothing here can tell the two apart.
- The footing's own structural design is not checked: punching shear, one-way shear and flexure size the concrete and the reinforcement, and a footing large enough for the ground can still be too thin for the column standing on it.
- Takes no account of adjacent footings whose stress bulbs overlap, of groundwater, of frost depth, or of an excavation planned alongside — each of which can change the allowable pressure without changing anything on this page.
What is actually underneath the performance clause
Everything so far is a requirement. Underneath it sits a build-up of about six items, each bought by a different trade against a different quantity, and pulling them apart makes it obvious which argument belongs to which layer. The sub-base argument is about compaction and about the stiffness value the designer assumed, usually a modulus of subgrade reaction taken from a plate bearing test to ASTM D1196 or its British equivalent, or correlated from CBR. The slip membrane argument is about friction and about keeping grout out of the sub-base, not about damp. The surface argument is about abrasion class and the finishing window, not about strength.
Two figures on that drawing set the programme rather than the design. The first is what the slab itself weighs, because pour mass fixes how much a finishing team can absorb in a shift, which fixes where construction joints land, which is the layout argument of the next section. The second is the reinforcement tonnage, which is a delivery and handling problem before it is a structural one. Read both with the assumptions in mind: a combined-mass figure of this kind is built on normal-weight concrete at around 2,400 kg per cubic metre, a bar grid at a stated spacing with a lap allowance added, and US bar sizes. A steel-fibre floor carrying no grid at all takes its steel from the fibre dose instead, and a mesh-reinforced floor takes it from the fabric reference.
A ground-bearing warehouse floor, from the rack leg down
- Rack upright and baseplate — the load the whole build-up exists to carry, arriving as a point through a plate whose size sets the punching perimeter Steel Column Baseplate Concrete Bearing Pressure Calculator
- Power-floated wearing surface — the only layer the flatness survey ever touches, and the one bought against an abrasion class rather than a strength
- Structural slab, jointed — carries the leg by bending and by punching resistance, and shortens as it dries whether or not a joint was cut for it Concrete Slab + Rebar Combined Mass Calculator
- Fibre and edge reinforcement — bought against a residual flexural strength in a jointless design and against a bar schedule in a jointed one Fiber-Reinforced Concrete (FRC) Dosage Calculator
- Slip membrane — cuts subgrade friction so the slab can shrink toward its joints, and stops grout draining into the stone Vapor Barrier Calculator
- Compacted sub-base — placed in lifts and proved against a density reference, because the design took a stiffness value from it Gravel Base Layer Tonnage Calculator
- Prepared formation — proof-rolled and signed off before anything covers it, since every check above assumes it behaves Standard/Modified Proctor Compaction Percentage Calculator
Panel dimensions and a bar grid give concrete and steel tonnage as one figure, which is what the pour programme and the handling plan are built from rather than a volume you then have to weigh separately.
The length of the slab.
The width of the slab.
The thickness (depth) of the slab.
Rebar grid spacing in both directions.
The rebar bar diameter used in the grid.
Total combined mass
9,960 lb
General-purpose slab reinforcement guideline, not a structural engineering design — load-bearing slabs should follow an engineer's specification.
- Concrete volume
- 2.41 yd³
- Concrete mass
- 9,738.76 lb
- Rebar linear length (incl. lap splice)
- 325.45 ft
- Rebar mass
- 217.38 lb
They open the calculator with your figures already in it
Concrete Slab + Rebar Combined Mass Calculator: 9,956 lb — 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
- It models one flat mat of bars at a single spacing. Top mats, chairs and bar supports, perimeter and edge bars, dowels, and trim steel around openings are not counted — a slab detailed with both a top and a bottom mat carries roughly twice the steel this returns.
- This is a quantity estimate, not a reinforcement design. Nothing here checks the bar size or spacing you chose against span, load, subgrade or crack-control requirements, and no minimum steel ratio is enforced. Load-bearing and permitted slabs need an engineer's bar schedule.
- The 15% lap allowance is a blanket figure applied to every metre of bar, not a splice schedule — it is added even on a slab whose sides are shorter than one stock bar, where no splice is physically needed. Bars are also counted running the full slab dimension edge to edge, so end cover, hooks and an actual cut list are not modelled.
- Concrete density is fixed at normal-weight and cannot be changed for lightweight, heavyweight or high-density mixes, and the concrete volume is not reduced for the space the steel occupies. Bar weights are the ASTM #3/#4/#5 figures; the metric sizes shown beside them are customary near-equivalents, and a true 12 mm bar is around a tenth lighter than the #4 weight used. The grid pitches are near-equivalents in the same way: picking "300 mm" spaces the bars at 12 in, which is 304.8 mm, so on a round metric slab the count can come out a bar short of a true 300 mm grid and the rebar rows a few per cent light.
- The result is concrete plus grid steel only. Formwork, welded mesh, macro fibre, vapour barrier, insulation, embedded conduit and pipework, and any topping or screed are excluded — so it is a floor on the mass for a lift or a load limit, not the whole make-up.
The joint grid and the rack grid have to be one drawing
In a warehouse the joint layout is not a concrete decision made by the concrete subcontractor. It is a layout decision taken against a rack grid that may not exist yet, and it comes down to two rules that are easy to state and hard to hold: no joint under or immediately beside an upright, and no joint crossing a guided aisle where a wheel will cross it repeatedly at the same point.
The conventional spacing rule — a maximum spacing in feet at roughly two and a half times the slab thickness in inches, with panels kept close to square — comes from the same shrinkage arithmetic as any other flatwork, and it is a ceiling rather than a target. It is the right place to start and the wrong place to finish on a distribution unit. At two hundred millimetres — near eight inches — it hands you twenty feet, so panels around six metres, and a twelve-thousand-square-metre floor then contains something like four kilometres of joint, every metre of which is an edge that curls, an arris that spalls and a line a wheel drops over.
That count, rather than the spacing, is the argument for the two alternatives large industrial floors are usually built as. Long-strip construction keeps sawn joints running in one direction only and puts the formed joints where the pour breaks were always going to be. Steel-fibre jointless construction pushes free-movement joints out to tens of metres and accepts planned cracking restrained by fibre in between. Both change the flatness picture as well as the durability one, because fewer joints means fewer curled edges for a levelness survey to find. Neither removes the obligation to draw where the joints go before the first bay is poured.
Run the specified thickness through the conventional rule first, not to adopt the answer but to see how many joints a conventionally jointed floor of this area would carry — that count is what makes the case for long-strip or jointless construction.
The thickness of the concrete slab.
Maximum joint spacing
10 ft (maximum spacing)
This is a general rule of thumb — actual joint layout should also follow the slab's panel shape (aim for roughly square panels, not long narrow strips), re-entrant corners at any cutouts, and any project-specific structural engineering requirements.
- Slab thickness
- 4 in
They open the calculator with your figures already in it
Concrete Control Joint Spacing Calculator: 10 ft (maximum spacing) — 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
- Thickness is the only input. What comes back is a spacing ceiling, not a joint layout: the calculator never sees the slab's plan dimensions, so it cannot count the cuts, place them, keep the panels near square, or flag that an inside corner or a block-out for a bollard or column base needs a joint run out of it.
- The multiplier is fixed at the middle of the cited range and does not move for the conditions that decide where in that range a slab belongs. A high-shrinkage mix, small maximum aggregate, a hot windy pour, or restraint from a rough sub-base, thickened edges or footings all argue for tighter spacing than this returns.
- This is a rule of thumb for a plain slab on ground, not a design. It does not apply to a structurally reinforced slab, a post-tensioned slab, a suspended or elevated floor, or a steel-fibre jointless floor, and where a project specification, a standard drawing or a local authority sets a spacing, that figure governs and this one has no standing.
- Spacing is all it returns. Cut depth — the joint has to remove enough section to force the crack at that plane, traditionally about a quarter of the slab thickness — and the sawing window after finishing are both outside the calculation, and a joint at perfect spacing cut too shallow or too late controls nothing.
- Control joints are one of three joint types and the only one modelled here. Isolation joints where the slab meets columns, walls and footings, and construction joints at pour breaks, are separate decisions with their own positions; a construction joint that lands off the control-joint grid gives the slab two competing instructions about where to crack.
Load transfer, and the millimetre that ruins a wheel
A joint with no load transfer is two slabs pretending. A wheel crossing it drops onto an unsupported edge, the edge deflects, the arris breaks away, and within a year the joint is a trench the drivers slow down for and the maintenance contractor patches every quarter. Load transfer is what prevents that, and in a warehouse it has to survive movement in two directions, because the joint opens as the slab dries while the wheel crosses it at whatever angle the aisle geometry dictates.
Round dowels are the pavement solution and they work where a joint opens along the dowel axis and nowhere else. In a jointed industrial floor whose panels shrink both ways, a round dowel restrains the joint transversely and can crack the very panel it was installed to protect — which is why plate dowels in compressible sleeves, square or diamond plates that free the joint in the plane of the slab, are so common on this kind of work. The sizing variables are the same either way: slab thickness, the run of joint to be doweled, and the load that crosses it. The highway rule of thumb, a diameter near an eighth of the slab thickness at twelve-inch centres, is where the first pass comes from, and it belongs to a road rather than to a floor with a plate dowel system on it.
Then the arris itself. On a floor taking heavy handling equipment a sawn edge does not survive on its own, and steel-armoured joints with the edge protection cast in are the standard answer at construction joints in a free-movement layout. Sawn control joints in the field get filled rather than armoured, and ACI 302.1R is explicit that this is a filler and not a sealant: a semi-rigid epoxy or polyurea at a minimum Shore A hardness of 80, taken to the full depth of the saw cut, installed as late in the programme as the schedule allows so that the joint has done most of its opening before anything goes into it.
- Fix joint positions against the rack grid before the pour sequence is agreed, not after the concrete subcontractor has planned their bays around a crew size.
- Decide how many directions the joint has to move in, because that decides round dowel against plate dowel in a sleeve and nothing later in the programme can change it.
- Size and count from slab thickness and joint run, then round to a commercially available bar or plate rather than ordering a calculated diameter nobody stocks.
- Set dowels parallel to the surface and to one another; a dowel out of parallel locks the joint it was installed to release, and the crack turns up somewhere you did not plan.
- Specify armouring wherever trucks cross, and detail how the armour is fixed and levelled, because it is a flatness item every bit as much as a durability one.
- Fill as late as the programme permits, full depth of the cut, and record the date so the retained shrinkage argument has a paper trail when the filler is inspected.
Thickness and joint run give a first-pass diameter and count off the highway rule; treat that as the floor of the specification and check it against a plate-dowel system wherever the joint has to move in two directions.
The thickness of the concrete pavement slab.
The length of the transverse joint needing dowels.
The on-center spacing between dowel bars.
Dowel bars needed
12 dowel bars
The calculated diameter is a raw guideline value — round up to the nearest commercially available dowel size (commonly 3/4, 1, 1-1/4, or 1-1/2 in) rather than ordering a non-standard size.
- Calculated dowel diameter
- 0.97 in
- Standard dowel length
- 18 in
They open the calculator with your figures already in it
Concrete Pavement Dowel Bar Calculator: 12 dowel bars — 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 bar count is a spacing tally along the joint, not a layout. It assumes a dowel sitting at each extreme end of the joint, while real joint details set the outer bars in from the pavement edge and the longitudinal joint, and some omit dowels near the edges entirely. Set the bars out from the governing standard drawing and treat this figure as a check on the total.
- This sizes bars by proportion, it does not design load transfer. Traffic volume and axle loading, base and subgrade support, joint opening from thermal movement, and the load-transfer efficiency the joint has to achieve are all outside the calculation. The diameter it returns is a rule of thumb, not an engineered dowel design.
- The 18 in (457 mm) length is a fixed constant, not a calculated result, and nothing here covers the detailing that decides whether the joint works: epoxy or stainless coating, the bond breaker or lubricant on the sliding half, embedment each side of the joint, or alignment tolerance. A bonded or skewed dowel locks the joint and cracks the slab no matter how right the count is.
- The result is one transverse joint. It does not total the joints across a pour or a job, add spares for damaged or rejected bars, include basket assemblies and chairs, or cover tie bars at longitudinal joints, which are deformed, bonded on both sides and sized by an entirely different rule.
- This is highway and industrial paving guidance only. Airfield, port and heavy industrial pavements are designed to separate standards with different dowel rules, and none of this replaces the specifying agency's standard joint detail or a pavement engineer's design.
Fibre is two products sharing one word
A specification that says fibre-reinforced and gives a dose in kilogrammes per cubic metre has said almost nothing. Micro-synthetic fibre at around a kilogramme per cubic metre controls plastic shrinkage cracking in the first hours after placing. It is cheap, it is worth having, and it contributes nothing at the ultimate limit state. Structural macro fibre, steel or polymer, is dosed an order of magnitude higher and is the material that replaces bar in a jointless design. Naming a dose without naming the performance it must deliver leaves the supplier free to satisfy the number with entirely the wrong product.
The performance is a residual flexural strength measured on a notched beam. BS EN 14651 is the European test, and it is what TR 34's design equations consume; ASTM C1609 covers the third-point loading equivalent in American practice. Specify the residual values the design actually used, name the test method, and let the dose fall out of the manufacturer's data for the product supplied. ASTM C1116 classifies the fibre types, BS EN 14889 covers steel and polymer fibres as products, and ASTM A820 is the steel fibre specification. Those are the documents a clause should point at. A bare dose is not a specification, it is a purchase order that escaped into one.
Fibre also changes the finishing, which is where this section meets the flatness class two headings back. Higher doses reduce workability, can bring fibre up at the surface, and move the window in which a power float can be run. Any floor being finished to a tight class has a finishing window that both the fibre and the admixture regime will shift, and that is a conversation to have with the flooring contractor and the ready-mix supplier while the class is still being chosen, rather than after the first bay has gone down and read short.
This sizes the shrinkage-control line only — pour volume against a rate around one kilogramme per cubic metre — so price the micro-synthetic dose here and take any structural steel-fibre dose from the design's residual strength requirement, which sits well above the range this covers.
The total volume of concrete being placed, in the unit shown.
The fibre dosage rate, as mass per unit volume of concrete.
Fiber needed
26.3 lb
Fiber dosage varies significantly by product and intended use (shrinkage control vs. structural reinforcement) — always follow the specific fiber manufacturer's technical data sheet for your project.
- Equivalent in pounds
- 26.29 lb
They open the calculator with your figures already in it
Fiber-Reinforced Concrete (FRC) Dosage Calculator: 26.29 lb — 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
- Only the dosage rate carries any information about the fiber itself. Length, denier, geometry and whether the product is monofilament, fibrillated or macro all change what a given kg/m³ actually delivers, and none of them are inputs. The rate has to come from the data sheet for the fiber being supplied.
- This is a purchase quantity, not a reinforcement design. It does not look at residual flexural strength, joint spacing, slab thickness or subgrade, and it cannot tell you whether fiber substitutes for bar. A jointless or structural fiber slab is designed against a residual-strength requirement measured on notched beams, and the dose falls out of that design rather than out of a volume multiplied by a rate.
- The answer is an exact mass for the exact volume typed: no waste allowance, no over-batching margin, and no rounding to whole bags. Fiber ships in pre-weighed bags sized to a batch, so what you actually order is bags per truck — round the mass up yourself against the bag size.
- The dosage rate is capped at 9 kg/m³ (0.56 pcf). That range covers micro-synthetic and structural synthetic macro fiber, but steel fiber doses used in jointless industrial floors sit well above it, and a rate typed above the cap is clamped down to 9 rather than refused.
- Nothing here covers what the fiber does to the pour. Mixing time and drum speed decide whether the fibers disperse or ball up, higher doses cut slump and can bring fiber to the surface, and the power-float window moves with them. Those sit with the ready-mix supplier and the finishing crew, not with this number.
The clauses that quietly decide who pays
Most warehouse floor disputes are not about concrete. They are about a specification that named a class and left out the four sentences around it, so that when the survey comes back short there is no agreed method, no agreed timing, no agreed remedy and no agreed re-survey. The same gap opens on abrasion, where a clause that says power-floated finish has said nothing measurable, while a clause pointing at an abrasion resistance class in BS 8204-2, or at a test procedure in ASTM C779, has. It opens again at anchoring, where every upright has to be fixed to the slab, the anchor design is governed by the anchoring provisions of ACI 318 or the equivalent European rules, and edge distance from a joint or a slab edge is a real constraint that a racking layout drawn without the joint layout will breach.
Write the exclusions with the same care as the requirements. State the traffic regime the floor was designed for and the areas each class applies to. State that a change of occupier's handling equipment is a change of design basis. State whether the floor is designed to receive a coating or a covering later, because that brings a moisture criterion with it that has nothing to do with either flatness or strength. And state, in one line, what the floor was not designed for — because the sentence that saves the argument two years from now is almost always the one that says what is out of scope.
- Surface regularity: the class, the area it applies to, the survey method, the survey window, the remedy and who carries it.
- Loading: UDL, rack leg load with baseplate size and position tolerance, line loads, and the handling equipment the dynamic allowance was based on.
- Ground: the stiffness value the design assumed and the test that will prove it, plus the compaction standard for the sub-base and formation.
- Concrete and reinforcement: strength class, the residual flexural performance if fibre is structural, and the test method for each.
- Joints: layout responsibility, load transfer type, armouring extents, filler type and hardness, and the earliest date filling may start.
- Surface: abrasion class and its test, curing method and duration, and any moisture criterion for a covering that may follow.
What should be in the file at handover
The floor is only as defensible as its record: the flatness survey with its date and method, the concrete test results, the compaction records for formation and sub-base, the fibre delivery tickets against the specified dose, the as-built joint layout with the filling dates against each run, and the anchor pull-out results if any were called for. Hand that over with one honest sentence attached — that the floor is fit for the traffic regime it was specified against and for no other — and the next tenant with a different truck starts a conversation about a variation instead of a claim.
Settle these before the slab section is issued
None of these are concrete questions, which is why they are usually still open when the specification goes out. Each one changes a clause rather than a rate, and each is far cheaper to answer now than after a bay has been poured against an assumption.
- Traffic regime, drawn as areas on the slab layout — Random traffic everywhere, or a defined-movement block. If the block is not located yet, the clause has to say so and say what lifting it later would involve.
- Rack leg load, baseplate size and the position tolerance — From the racking supplier if there is one, or an assumed envelope stated as an assumption. The plate size drives the punching check as hard as the load does.
- The stiffness the design assumed, and the test that proves it — A modulus of subgrade reaction from a plate bearing test, or a CBR correlation, named in the clause so the ground investigation scope actually covers it.
- Joint strategy and who owns the layout — Jointed, long-strip or fibre jointless, and whether the joint drawing is the designer's or a subcontractor design that has to be approved against the rack grid.
- Survey method, window and remedy — The three sentences that turn a class into an obligation. Include whether a ground area is re-surveyed and against which value.
- What happens to the surface afterwards — Coating, covering or bare power-floated concrete, because a covering brings a moisture criterion and a coating brings a surface preparation the finishing method has to allow for.
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.