The letting particulars gave you two numbers and both are the wrong shape
A unit is marketed on clear internal height to the haunch and a floor loading in kilonewtons per square metre. Neither survives contact with a racking layout. The haunch height is not usable height: the sprinkler main hangs below the purlins, the deflectors hang below that, the high-bay fittings hang somewhere near them, and the top pallet has to sit clear of the lot with air to spare. The floor loading is a uniformly distributed figure, and an upright does not distribute anything — it hands five or ten tonnes to a baseplate roughly the size of a paperback, four hundred times across the floor.
What is genuinely fixed on the day you get the keys is short: the column grid, the slab and the joints already cut into it, the dock positions and door heights, the sprinkler system and whatever it was designed to protect, and the roof. What is still yours to choose is shorter but far more expensive: which trucks you run, how wide the stack aisles are, how long the bays are, how the beam levels are pitched, and which way the runs face. Almost every fit-out gets those in the wrong order, because the racking quotation arrives before the truck decision has been made and the layout on it is drawn to fill the shell.
Aisle width is the dimension that costs the most and gets the least thought. Take twelve stack aisles at sixty metres. One hundred millimetres added to each of them is seventy-two square metres of floor gone — call it forty-five ground-level pallet positions, permanently, for a decision nobody wrote down. The same hundred millimetres taken off the wrong truck is a mast that clips an upright at eight metres, which is a repair, an offload, and an insurer who wants to know what changed.
Start at the pallet you actually receive, not the one in the standard
The dimensions everyone quotes are ISO 6780 for the principal international sizes and EN 13698-1 for the 800 by 1200 mm EUR pallet; in North America the GMA 48 by 40 in pallet does the same job. Knowing which one your suppliers ship is the first decision, because the pallet's presented face is what sets the bay, and the pallet's depth is what sets the frame. A 1200 by 1000 mm pallet racked with its 1200 face outward gives you a 1000 mm deep position; the same pallet turned through ninety degrees gives you 1200 mm deep and a different bay length entirely. Both are legitimate; running both in the same building without deciding which is not.
Then stop measuring the pallet and start measuring the unit load. What arrives is timber plus goods plus stretch wrap plus whatever the last handler did to it, and it is routinely wider, deeper and taller than the pallet under it. Cases overhang. Wrap bulges. A shrink-wrapped stack of drums leans.
So measure fifty received loads across your deepest, tallest and heaviest lines and work from the tail of that spread rather than the average. The layout has to accept the load that turns up on a bad Friday, not the mean of a spreadsheet.
Pallet construction matters as much as pallet size once it is off the floor. A perimeter-based pallet lands on beams along its whole bearing edge; a three-stringer pallet with the stringers running parallel to the beams is bridging on nothing but deck boards, and that is the arrangement that drops loads through a bay. Where the receiving mix cannot be controlled, the answer is support bars or mesh decking in every bay, specified at the outset. Mesh against solid is also a fire question, because solid shelving blocks water and the sprinkler scheme may have been designed assuming it is not there.
Last comes weight, and it wants two numbers rather than one: the heaviest single unit load, and the heaviest realistic total in a bay. Those two are inputs to the rack's structural design under EN 15512 or ANSI MH16.1, and they are what the load notice on the finished run will state. A layout that quietly assumes a tonne a pallet, in a building that receives 1,400 kg of tinned goods on the ground floor lines, has already spent the margin the designer thought they had.
The truck's type sheet already contains your aisle width
Industrial trucks are published on a common type sheet — the format set out in VDI 2198 — and two of its lines are the layout. One gives the turning radius. The other gives the aisle width for right-angle stacking, quoted separately for the two standard pallet orientations, because the load swinging round in front of the truck is part of the geometry. That published figure already has an operating clearance built into it, so read which clearance the manufacturer used before comparing two trucks: the sheets share a format and not always an allowance. The bands below orient a first layout and nothing more, and every one of them has to be replaced by the figure for the specific truck with the specific pallet before anything is ordered. If the fleet is being renewed as part of the fit-out, get the shortlist's type sheets before the racking quotation rather than after — the aisle is bought once and the trucks are bought every seven years.
The narrower classes are not free. Reach trucks and articulated trucks recover floor from the aisles and hand back time at the ground level, where a counterbalance truck is quicker in and out of a trailer. Man-up turret trucks in very narrow aisles need guidance — rail or wire — an end-of-aisle transfer system, a floor built to a defined-movement tolerance, and a plan for what happens when one fails mid-aisle with four hundred positions behind it. And every one of them assumes an operator who is comfortable. The aisle you can just about turn in on a Tuesday afternoon with your best driver is not the aisle an agency driver turns in at three in the morning in November.
| Truck family | Indicative right-angle stack aisle | What it demands elsewhere |
|---|---|---|
| Counterbalance, sit-down | About 3.6 to 4.2 m for a 1200 mm load | Nothing special from the floor, and it can go outside to a trailer; it costs the most floor of any option |
| Moving-mast reach truck | About 2.7 to 3.1 m | A flatter floor, indoor duty only, and clearances that grow with placement height as the mast deflects |
| Articulated counterbalance | About 2.0 to 2.5 m | Trained operators and a tight discipline about aisle housekeeping; it will still work a trailer at the dock |
| Man-up turret truck, very narrow aisle | About 1.6 to 1.9 m | Rail or wire guidance, a defined-movement floor tolerance, end-of-aisle protection, and a rescue plan |
| Powered pallet truck or low-level order picker | Narrower again, but it does not stack high | Only useful for ground and first-level work; it does not remove the need for a stacking truck somewhere |
The gaps around a pallet are the design
A bay is not two pallets wide. It is two pallets and three gaps, and then the upright section on top of that. Take two 1200 mm wide unit loads with 100 mm between them and 100 mm to each upright: 2700 mm clear between the frames, and with a 100 mm deep upright section the bay pitch on the floor becomes 2800 mm. Twelve bays is a 33.6 m run before the closing frame. Change those gaps to 75 mm and the same twelve bays come in at 32.7 m — nearly a metre back, which is exactly where the temptation lives, and exactly the change EN 15620 will not let you make at height.
EN 15620 governs this, and its logic is worth understanding rather than looking up. Clearances are graduated by how high the load is placed, because mast deflection, floor tolerance, the truck's own free play and the operator's sightline all grow with height. A clearance that is generous at the ground level is optimistic at eight metres and reckless at twelve, which is why fixing one figure for the whole elevation is the commonest mistake on a layout drawn by someone who has only worked the bottom beam.
Depth works the other way round. The frame is usually shallower than the pallet, so the load overhangs the beams front and back by fifty to a hundred millimetres each side. That is deliberate and correct, and it means the rack footprint on the floor is not the pallet footprint — a point that matters the moment somebody sets out the baseplate positions from the pallet dimension. Back to back, two runs need a spacer between the frames to hold them apart and tie them together, and that gap is a fire dimension as well as a steel one.
That brings in the other governing document. NFPA 13 treats rack storage as a geometry, not just a commodity: the flue spaces between pallets across a bay and between the two runs of a double row are the routes water and hot gas travel, and they are specified as nominal dimensions rather than left to the layout. FM Global Data Sheet 8-9 is the insurer's equivalent and can be stricter. Where the building has an existing system, the flue geometry and aisle width it was designed around are constraints you have inherited, and narrowing an aisle after the fact can put the storage arrangement outside what the system was designed for. That is a conversation with the sprinkler designer before the racking order, not after the first inspection.
| Gap | Between | What governs it |
|---|---|---|
| Side clearance | Unit load and upright | EN 15620 placement class — it grows with the height the load is placed at |
| Between-load clearance | Two unit loads in the same bay | The same placement class, plus the flue the sprinkler scheme requires |
| Lift-off clearance | Top of a load and the beam above it | The truck and the placement height; it is what the operator needs to withdraw without dragging |
| Front and rear overhang | Pallet edge and beam face | Frame depth against pallet depth — chosen, not accidental, and it sets the baseplate line |
| Run spacer | Two frames of a back-to-back double row | The rack supplier's spacer plus the longitudinal flue NFPA 13 or FM 8-9 asks for |
| End clearance | Last frame and a wall, column or downpipe | Access for inspection and damage repair, and whatever the column guard needs |
One bay in section, slab to deflectors
Vertical arithmetic is simple and unforgiving. Beam pitch is the loaded height of the unit, plus the lift-off clearance, plus the depth of the beam itself. Take a 1.35 m loaded pallet, 100 mm of lift-off and a 100 mm beam and the pitch is 1.55 m. The ground position sits on the slab, so the levels above it stack from there: first beam at 1.45 m, second at 3.00, third at 4.55, fourth at 6.10, fifth at 7.65 — and the load on that fifth beam tops out at 9.10 m, because the beam's own hundred millimetres sit under it before the pallet does.
Now bring the survey in. Say the deflectors over the aisle nearest the eaves come in at 9.50 m, and NFPA 13's clear space above the top of storage takes 460 mm off that in the common case — the 18 in the standard asks for, more where the scheme demands it, and a different rule again where the system is ESFR. The top of storage is therefore capped at 9.04 m and the fifth level wants 9.10 m. It misses by sixty millimetres, which is small enough to argue about and quite large enough to fail an inspection. You get four beam levels above the ground position, or you re-pitch the whole elevation, or the top level takes only the shorter lines and is set as a half-height level from the start.
Two further caps sit behind that one. Lift height is quoted to the fork face and the load stands above it, so a truck with 7.5 m of lift does not serve a beam at 7.65 m whatever is on the pallet. And residual capacity falls with height: a truck badged at 1.6 tonnes may be rated well under a tonne at full lift, which is on its load chart and nowhere on its badge. Check the top level against the load chart with the actual attachment fitted, because a fork-mounted clamp or a side-shifter takes capacity off the chart before you start.
What one rack bay is made of, bottom up
- Clear space to the sprinkler deflectors — the air NFPA 13 requires above the top of storage, surveyed over the aisle rather than assumed from the eaves height
- Unit load on its pallet — goods, wrap and timber together — measured as received, because this height is what the beam pitch is built from Timber Pallet Stack Storage Capacity Calculator
- Beam level — a pair of beams whose clear length is the bay: two loads and three gaps, with the connector locks fitted
- Braced upright frame — two uprights and their bracing, depth chosen so the pallet overhangs the beams front and back
- Baseplate, shim and floor anchor — where the whole bay load becomes a bearing pressure on concrete, over an area the size of a paperback Steel Column Baseplate Concrete Bearing Pressure Calculator
- Ground-bearing slab and its joints — the sawn joint pattern decides where a baseplate may land, because a joint behaves as a free edge Concrete Control Joint Spacing Calculator
The turn at the end of the aisle, and the ground outside the door
A stack aisle is only half the movement problem. The truck has to get into it from a cross aisle, and entering an aisle square is a different manoeuvre from stacking in it — on some trucks it needs more room, not less. Cross aisles also carry through traffic, pedestrians and the pallet trucks working the ground level, so they are sized for two things passing rather than for one thing turning. In a guided very narrow aisle installation the end transfer aisle is its own piece of engineering, because the truck has to come off guidance, turn, and pick up the next aisle's rail or wire cleanly.
At the dock face the constraint changes species again. The transfer aisle across the doors has to be deep enough that a truck coming off a leveller can turn out of the trailer's line without reaching into the first stack aisle, which usually makes it the widest aisle in the building and the one most often eaten by staged pallets. Outside it, rigids at a side door, tow tractors and whatever has to reach the compactor each sweep their own ground — and the one that catches people out is the vehicle nobody planned for because it only comes on Thursdays.
The two outlines that matter for any of those vehicles are the path the inside rear tyre cuts and the path the outer front corner sweeps, and they are not the same curve. The first one shears kerb noses and crumbles the edge of a slab; the second one takes mirrors off column guards and clips the canopy. Model them for the road vehicles and the tow tractors, and take the lift trucks' own aisle figures off their type sheets instead — a counterbalance truck steers at the rear, so a front-steered single-unit model is the wrong shape for it, and its manufacturer has already published the answer.
Run it on the yard vehicles — the rigid at the side door, the tractor unit on the apron, the tow tractor through a cross aisle — and read both radii, because the band between them is the ground that has to stay clear of columns, bollards and the first rack frame.
Front axle centre to rear axle centre on the design vehicle.
How far the front wheels can be turned at full lock.
From the front axle centre forward to the foremost point of the body.
Overall width across the body, mirrors excluded.
Added outside the body envelope for driver variation and kerb faces.
Swept path width
17.2 ft
A single-unit bicycle-model turn at steady full lock. It does not model a combination vehicle's trailer off-tracking, a transition into or out of the curve, or superelevation, and it is a check on a published template rather than a replacement for one.
- Inside rear tyre path radius
- 28.26 ft
- Outer body envelope radius
- 45.48 ft
- Turn radius at the rear axle centre
- 32.26 ft
They open the calculator with your figures already in it
Design Vehicle Swept Path Calculator: 17.22 ft — 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
- Swept path has height as well as width. A container being tipped, a raised tailgate or an aerial device needs vertical clearance this page says nothing about.
- Trailer off-tracking on a combination vehicle is additional and can be well beyond the tractor's own inside path.
Everything above is standing on somebody else's slab
Work out what an upright actually delivers before you trust a floor. Five beam levels at two 1,000 kg pallets each is ten tonnes in the bay, and an interior upright in a continuous run carries a share of the bay either side of it. Push five tonnes through a 150 by 100 mm baseplate and the bearing pressure on the concrete is a little over three newtons per square millimetre — which is a check against ACI 318's allowable bearing on concrete for the plate itself, and separately a punching and flexural check on a ground-bearing slab, which is what the Concrete Society's TR34 exists to do.
Where the baseplate lands matters as much as what it carries. TR34 works internal, edge and corner load cases separately because a slab loaded beside a free edge has markedly less capacity than the same slab loaded mid-panel, and a sawn joint behaves as a free edge. Get the joint layout from the construction records or scan for it, then set frame lines so baseplates sit within panels rather than straddling cuts. On an existing slab take cores for thickness before promising anything: the last tenant's anchor holes tell you where their frames were, not how thick the slab is.
The anchor is its own small design. EN 15620, EN 15635 and the SEMA code all treat fixing every upright to the floor as normal practice rather than an option, and the anchor has to reach an effective embedment while keeping its edge distance from joints, slab edges and existing holes. ACI 318's anchoring chapter is where concrete breakout comes from, and a joint sitting eighty millimetres from your setting-out line will quietly halve what the anchor can do. Check the drilled depth against the slab thickness too — a 150 mm slab and a deep-set anchor is a conversation about drilling through into the sub-base.
Finally, flatness, which is the decision that cannot be reversed. Wide-aisle work on counterbalance and reach trucks lives comfortably with a free-movement floor tolerance — TR34's classification in the UK, or FF and FL numbers measured to ASTM E1155 and specified through ACI 302.1R elsewhere. Very narrow aisle work does not: it needs a defined-movement floor, measured along the actual wheel tracks, because the truck runs a fixed path and lifts twelve metres above it. That is why going VNA is a decision taken before the floor is laid or accepted. Afterwards the options are grinding, a bonded topping, or a different truck, and only one of those is cheap.
The third of the floor that never gets racked
No warehouse is all racking. There is a dock buffer where inbound sits before it is put away, a marshalling area where outbound is built, a quarantine and damages corner, an empty pallet return that grows all year, a battery charging or LPG exchange area, and usually a block-stacked bulk area for the lines that move in whole-lane quantities. Together they routinely take a third of the floor, and if they are not drawn at the start they get taken out of the aisles instead — which is how a 3.2 m stack aisle becomes 2.6 m of usable width with a stillage in it.
Block stacking is where the arithmetic is most often flattered. Divide a clear area by a pallet footprint, multiply by the layers the load will safely bear, and the answer looks wonderful compared with racking. What it misses is honeycombing: a lane holds one line, it is full only on the day it is filled, and every pick after that opens a hole nobody else can use. Deep lanes suit lines that arrive and leave by the lane; shallow lanes suit everything else; and the loss is not a percentage you can look up, it is a function of how many pallets per line you actually hold. The other omission is that the stacking limit belongs to the goods, not the machine — crush strength of the packaging, the pallet's own rating, and the plain requirement in OSHA 29 CFR 1910.176 that stored material is stable and secure against sliding or collapse.
Run the numbers on the area that is genuinely clear once aisles, turning space and fire routes are out of it, and with the loaded height of the unit rather than a bare pallet — a default near 150 mm describes a stack of empty pallets and returns a capacity that means nothing. Treat the answer as a ceiling rather than a plan, and put an honest honeycombing allowance against it before comparing it with the racked positions the same footprint would give.
Use it on the block-stacked bulk area and the empty pallet return, with the clear footprint after aisles and the loaded height off a despatch note — both of its roundings are downward, which is what makes the answer a count rather than an ambition.
The total floor/yard area available for pallet storage.
The floor area occupied by a single pallet.
The maximum allowable stack height (ceiling, rack, or safe-stacking limit).
The height of a single loaded pallet in the stack.
Total pallet storage capacity
320 pallets
This assumes uniform pallet footprint and height with no aisle/access clearance deducted — subtract clearance space for forklift access or walkways from the storage area before using this calculator for a realistic count.
- Pallets per layer
- 16 pallets
- Stack layers
- 20 layers
They open the calculator with your figures already in it
Timber Pallet Stack Storage Capacity Calculator: 320 pallets — 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
- Divides area by area, which assumes the pallets tessellate perfectly. Floor space is a shape, not a number: a 1.2 x 1.0 m (3.3 ft) pallet has to fit a real bay dimension by dimension, so a strip 2.2 m (7 ft) wide holds one row and wastes the last metre, while the same area in a squarer bay holds two. Set the grid out on the actual bay dimensions before trusting this count - on an awkward footprint the shortfall against the area division is commonly 10 to 20%.
- Counts positions, not weight. Every floor has an allowable uniform load, and it bites hardest on a suspended slab, a mezzanine or a container floor: a full-height block of dense product concentrates a great deal of weight onto each pallet footprint. Multiply pallets per position by the loaded weight and check it against the floor's rating in kPa or psf, because the height limit that governs is often structural rather than the ceiling.
- The safe stack height comes from what is being stacked. Everything above the bottom pallet is carried by the bottom unit load, and corrugated packaging loses a large share of its compression strength over time under load and in humid air, so a block that stands square on day one can lean or crush by week six. Loads with an uneven or non-flat top cannot be block-stacked at all and need racking, which changes the geometry entirely.
Clearances that appear on no racking drawing
The portal frame is the first of them. A haunch cuts diagonally across the top corner of the run nearest each side wall, so the outermost run often loses its top level for its whole length — and the supplier's elevation, drawn against a rectangle, will not show it. The same goes for downpipes on internal columns, heater flues, the duct nobody surveyed, and the roller shutter that opens into a run somebody drew straight through.
Lighting is the clearance people discover last. Fittings need to run along the aisle centreline, not across the runs, because a luminaire over a rack lights the top of a pallet and leaves the picking face in shadow. That makes the lighting layout a hostage to the racking layout, which is a good reason to fix aisle positions before the electrical package is ordered and an excellent reason not to move an aisle afterwards. Emergency escape lighting sits on top of it: aisles are exit access, a long dead-end aisle is a travel distance problem in its own right, and the escape route through a warehouse has to be lit whether or not the racking has since been reconfigured.
Then the protection and the people. Column guards, end-of-run frame protectors and barriers at aisle ends are cheaper than the upright they save and far cheaper than an offload. Pedestrian routes want to be segregated and marked rather than negotiated: OSHA 29 CFR 1910.176 requires sufficient safe clearance for aisles wherever mechanical handling equipment is used and that permanent aisles are kept clear and appropriately marked, 29 CFR 1910.178 governs how the trucks are operated in them, and HSE guidance HSG76 covers the same ground in the UK. A marked pedestrian route the racking leaves no room for is a route that gets ignored within a fortnight.
Chalk it, drive it, then release the order
Everything above is a drawing until somebody puts a truck in it. The proof costs a morning, a tape, a chalk line and one loaded pallet, and it is the only part of this process that finds the thing you got wrong.
- Get a measured survey of the shell rather than the landlord's drawing — columns, dock positions, door heights, and the underside of the lowest obstruction over every proposed run.
- Survey the sprinkler deflector level at several points, including over the aisle nearest the eaves, and take the floor level survey at the same time.
- Measure fifty received unit loads across the deepest, tallest and heaviest lines, and design from the tail of that spread rather than its average.
- Confirm the aisle figure on the type sheet of the actual truck, with the actual pallet orientation and the actual attachment fitted.
- Chalk one full aisle with two bay pitches on each side at the width you intend to buy, then put the truck in it and place a loaded pallet at the intended top beam level — with the driver who works nights, not the demonstrator.
- Lay the baseplate setting-out over the joint layout and move frame lines off the cuts before the drilling crew is booked.
- Only then release the order, with the marked-up layout as part of the specification — which is what EN 15629 asks the customer to provide, and what a rack designer needs to design against.
What it looks like after the first peak
Layouts drift in one direction. The dock buffer overflows into the first cross aisle, a bulk lane appears where the marshalling area was, someone finds a hundred millimetres by moving a run, and beam levels get re-pitched to take a new line without anybody checking what that does to the bay load. Meanwhile the uprights start collecting damage, and rack damage is not linear — a dented upright can have lost a large fraction of its capacity while looking survivable to a passing glance.
EN 15635 is the document that covers the rest of the rack's life: regular inspection, a nominated person responsible for rack safety, a damage classification that separates what is monitored from what is offloaded immediately, and the requirement that load notices stay accurate. Keep the layout drawing, the design brief and the load notices together, because the moment a run is reconfigured without the supplier's design check it has left the basis it was designed on, and the notice on the end frame is describing a rack that no longer exists.
Settle these before the racking order is released
Six numbers that fix the layout, taken in the order they constrain each other — the pallet constrains the bay, the truck constrains the aisle, and the survey decides whether the top level exists at all.
- The unit load as received, at the tail rather than the mean — Width, depth, loaded height and weight from fifty real pallets across the worst lines, including wrap bulge and case overhang.
- Right-angle stack aisle from the truck's own type sheet — For the pallet orientation you will actually handle, with the operating clearance the manufacturer used noted alongside it so two trucks can be compared honestly.
- Bay pitch built from loads and gaps, not from the shell — Loads plus between-load and side clearances graduated by placement height under EN 15620, plus the upright section depth.
- Surveyed deflector level over each proposed run — Measured, not taken off the haunch height. Less the clear space the sprinkler scheme requires, it caps the top of storage and therefore the level count.
- Upright base load and the joint layout under it — Bay load shared to the uprights, converted to a bearing pressure on the baseplate, and checked against a joint pattern no frame line should straddle.
- Floor area that will never be racked — Dock buffer, marshalling, quarantine, empty pallet return, charging and the block-stacked bulk lanes — drawn first, or it comes out of the aisles later.
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.