Cantilever Racking Buying Guide: Arms, Uprights & Load Ratings

A cantilever rack is one of the few pieces of warehouse equipment where the specification decisions you make on day one are almost impossible to unwind later. Arms bolt or slot onto uprights; uprights bolt to the floor. Adding arms later is cheap. Adding uprights later means a new bay, a new floor fixing pattern and, usually, a new aisle plan.

This guide is about the components and the load ratings — how a cantilever rack is put together, how to read an arm capacity without over-reading it, and what the published prices in our own range say about how to specify one. If you are still deciding whether cantilever is the right system at all, start with cantilever racking vs pallet racking or the wider warehouse racking types guide. If you are storing bar, tube and section rather than long timber, read timber, pipe and bar storage racks first — the answer there is often not a cantilever rack at all.

The components, and which of them cost money

Every cantilever rack is the same four things.

• Uprights — the vertical columns. These carry every load on the rack as a bending moment and they are what gets fixed to the floor. On our GPC modular range, a starter bay comes with three uprights and an extension bay adds one.
• Arms — the horizontal cantilevers the goods sit on. On the modular range these are height-adjustable in 150 mm increments and fitted with removable end stops so a forklift can load and unload from the end as well as the front.
• Base feet and bracing — what stops the whole thing folding over sideways. The base is doing two jobs: resisting the overturning moment from the loaded arms, and tying the uprights together so the run behaves as one structure.
• Fixings — the frames have wall and floor fixing points. The fixings are not included. This catches people out on delivery day more often than any other detail.

Of those four, the uprights are where the money is, and the published prices in our own range make that unusually clear.

What the price list actually says about specifying arms

Worked from the live configuration prices on the GPC modular cantilever range, all four starter bays carrying three uprights:

Two things fall out of that table, and neither is what a buyer usually expects.

Extra arms on uprights you are already buying cost a fraction of the average. Going from 12 arms to 15 on the same three uprights costs £217.68 on the 500 mm bay and £241.32 on the 1000 mm bay — roughly £73 to £80 per additional arm, against an all-in average of £224 to £284. The first arms are expensive because they arrive attached to the uprights; the last ones are nearly marginal cost.

And doubling the arm reach is almost free. Moving from 500 mm arms to 1000 mm arms on the same bay costs £262.74 at 12 arms and £286.38 at 15 — about £20 per arm, under 9% of the bay price, for twice the reach. That is a quarter of what an extra arm costs and a small fraction of what an extra upright costs.

Put together, those two facts give the single most useful rule in this guide: buy the longest arms and the highest arm count your uprights will carry, at the outset. Reach and arm count are the cheap variables. Uprights are the expensive one, and they are the one you cannot retro-fit without rebuilding the run.

Straight (parallel) versus tapered arms — and a price inversion

Parallel arms are the same depth along their whole length. They are the right choice when the load bears along the arm rather than at the tip — sheet material, boards, anything that sits flat and evenly.

Tapered arms are deeper at the root and shallower at the tip. Structurally that is where the bending moment actually is, so a tapered arm puts steel where the stress is and saves weight at the free end. They suit round and irregular goods that will settle towards the upright.

The usual received wisdom is that tapered arms cost more. In our range that is true single-sided and false double-sided, which is worth knowing before you assume a price.

So on a double-sided tapered rack you pay £159.42 less than for the parallel equivalent, while single-sided the same swap costs you £177.12 more. Choose the arm profile on what you are storing, then check the price rather than assuming it — the direction of the premium reverses inside a single range.

Single-sided versus double-sided

Single-sided racks go against a wall and are loaded from one aisle. Double-sided racks stand free in the floor and are loaded from both sides, sharing one line of uprights and one base between two sets of arms.

On the welded range the uplift from single to double is £475.74 on the parallel racks and £139.20 on the tapered. The double-sided rack is never twice the price, because you are buying a second set of arms rather than a second structure — the same logic that applies to double-sided benching and shelving. What you are actually spending is floor: a double-sided run needs an aisle on both faces, so it only pays where the building is wide enough to give it two access routes.

Welded or adjustable — the decision that outlasts the price

There is a structural split in our range that is easy to miss because it is not what the product names lead with.

• The modular starter and extension range is 250 kg per arm and height-adjustable in 150 mm increments.
• The parallel and tapered racks are 200 kg per arm and of fully welded construction — the arm positions are set at manufacture.

The cheaper racks are both weaker per arm and fixed. That is a defensible combination if you know exactly what you are storing and it will not change: welded frames are simple, rigid and there is nothing to work loose. But if the product mix might change — different lengths, different diameters, a new line — a 150 mm adjustment increment is worth considerably more than the price difference, and no amount of money spent later will make a welded frame adjustable.

One thing our product data does not state, and we will not guess at: the parallel and tapered racks are quoted at 200 kg per arm but the specification does not give an arm count. That means the two ranges cannot honestly be compared on price per arm or on total bay capacity, and any figure you see doing so is inferred rather than published. Ask us for the arm count against the specific model before you compare them on capacity.

How to read a load rating without over-reading it

This is where most cantilever specifications go wrong, and it is a single distinction.

250 kg per arm is not 3,000 kg per bay that you can put anywhere. A CR1004ST carries 15 arms; multiplied out that is 3,750 kg, and that number is close to meaningless on its own. What governs is:

• The rating is per arm, and your load has to actually reach several of them. A 6 m bundle spanning three arms is only sharing its weight across three arms if it bears on all three — which needs the arms level and the load stiff enough not to sag between supports. A load that bridges two arms and touches a third lightly is a two-arm load.
• Uneven distribution beats the total every time. Put a 600 kg coil on one 250 kg arm and you are 140% over on that arm while the bay sits at 16% of its nominal total. The bay rating will not save you.
• Load heavy materials at the base. Both welded ranges state this explicitly, and it is not just about the rack tipping. Every kilogram at the top of an upright is a larger bending moment at the floor fixing than the same kilogram low down.
• The arm rating assumes the load sits on the arm, not hanging off the end. Loading beyond the tip, or letting a bundle overhang so its centre of gravity sits outboard of the arm, changes the calculation entirely.

The practical version: work out the heaviest single item you will store, the number of arms it will genuinely bear on, and specify from that. Then post the resulting figures on a load notice at the end of the run, because a rack whose limits are not written down is a rack that will be overloaded by someone who was not there when it was specified.

Sizing and siting checklist

• Longest item, not average item — the arm length and the upright spacing both follow from the longest thing you will store, plus overhang.
• Arm reach against load depth — a 500 mm arm under a 700 mm-wide sheet stack is an overhang problem, and at roughly £20 per arm to double the reach it is a cheap one to avoid at order time.
• Height in 150 mm steps on the modular range — set the levels against real product heights plus a handling clearance, not against round numbers.
• Aisle width comes from your forklift's data sheet, not from a generic table. Loading long goods sideways from a cantilever rack usually needs more room than the same truck needs at a pallet rack. The racking types guide covers the aisle arithmetic.
• Floor first — slab thickness and condition at the fixing points decide whether the rack can be anchored as designed. Check before you order, not after.
• Protect the ends of the run where trucks turn. The same argument applies as to pallet racking — see upright guards and barriers.

Delivery day

Two facts sit in the product data that change how you plan the installation, and both are stated on the GPC cantilever products in as many words.

A forklift will be needed to unload these units. This is not a two-people-and-a-trolley delivery. If you have no forklift on site on the day, the lorry cannot be unloaded and the delivery will not happen.

Fixings are not included. The frames have wall and floor fixing points; what goes through them is specified against your slab and bought separately. It is the same pattern as our racking, shelter, bench and loading bay ranges, and it is worth settling at design stage — particularly if the floor has a membrane or underfloor heating, where the fixing method stops being a delivery-day decision.

Where our own range sits

The GPC configurations above run from £1,290.00 for a four-arm extension bay to £3,652.80 for a fifteen-arm starter bay. The STOW cantilever system sits above that as an engineered, modular system with a wide range of arm lengths and capacities — it is priced per configuration rather than off a list, so treat any single headline figure for a racking system, ours or anyone else's, as the price of one particular layout.

Browse the full range at cantilever racking, or see the wider racking and shelving range, pallet racking and heavy duty shelving. Both GPC and STOW ranges have their own brand pages, as does GPC Industries.

Inspection and safety

Cantilever racks fall under the same inspection regime as the rest of your racking — a competent person's inspection, a rack safety notice, and a damage reporting route that does not depend on someone volunteering bad news. Rather than repeat it here, that ground is covered properly in warehouse racking inspection: SEMA, HSG76 and UK law.

The one cantilever-specific point worth adding: damage to a cantilever arm is more consequential than damage to a pallet beam, because there is no second support. A bent beam still has an upright at each end; a bent arm is a single member with a load on its free end. Any arm that has been struck should be taken out of use until it has been assessed.

Related guides

For adjacent decisions: the pallet racking buying guide covers bays, beams and load ratings on the pallet side; longspan shelving and heavy duty shelving cover hand-loaded bulky stock; industrial shelving vs pallet racking is the forklift question; and UK pallet sizes explained is worth a look if the same run has to take palletised stock too.

Not sure which configuration fits your longest product and your aisle? Call us and we will work it through against the real arm lengths and capacities.