A collapsing stack of loaded stillages is one of the most avoidable — and most serious — incidents in a UK warehouse or yard. A single toppled steel container can weigh several hundred kilograms, and when it goes, it rarely goes alone. The good news is that stillage stability is almost entirely a matter of design, discipline and routine checks. Get the fundamentals right and a stacked column of steel is one of the safest, most space-efficient ways to store and move goods there is.
This guide sets out the practical fundamentals of keeping stillages stable — from load capacity and stacking heights to storage layout, transport restraint and inspection — and shows where they sit within the UK regulatory framework. It is written for warehouse managers, transport supervisors and health-and-safety leads who need something more useful than “stack carefully”. As a UK manufacturer of steel stillages and cages, we build stability into our products from the drawing board, and this is how we advise customers to keep it there in daily use.
Why stillages collapse in the first place
Collapses and topples almost never come out of nowhere. They are the end point of one or more of a short, familiar list of causes:
- Overloading — putting more weight into a stillage, or onto a stack, than it was designed to carry.
- Poor weight distribution — a load concentrated to one side or piled high creates a top-heavy, off-centre container that wants to tip.
- Stacking too high — every additional layer adds mass and raises the centre of gravity, and small misalignments compound as the column grows.
- Misalignment and mismatched units — corner posts and feet that do not sit squarely into the unit below transfer load through the wrong points.
- Uneven or soft ground — a floor that dips, slopes or gives way under point loads tilts the whole stack.
- Damage and fatigue — a bent post, cracked weld or worn foot quietly removes the safety margin the designer built in.
- Unrestrained movement — a stack that is stable at rest can shift and fall the moment a vehicle brakes or a forklift nudges it.
Prevention is simply the mirror image of that list. Work through each cause in turn and stability follows.
Start with load capacity — and respect it
Every stillage has a safe working load (SWL): the maximum weight it is designed to hold in normal use. Where units are designed to be stacked, they also have a stack-rating — the load the base unit can bear from the containers above it. These are not the same number, and both matter.
Two rules cover most of the risk:
- Never exceed the SWL of the individual unit. If you are not certain of a stillage’s rating, treat it as unknown and have it verified rather than guessing.
- Account for the cumulative load down a stack. The bottom unit carries everything above it. Heaviest at the bottom, lightest at the top — always.
Where lifting is involved, load capacity stops being advisory and becomes a matter of formal certification. Any stillage lifted with its contents — by crane, hoist or forklift jib — is lifting equipment, and it should be proof-load tested and certified before use. Our certified lifting stillages are load tested as standard, and units such as the Liftable Mesh Stillage come with test documentation included, so the rating on the label is backed by evidence, not assumption. A clear, legible SWL label on every unit is the single cheapest stability control you can put in place; it turns “how much can this take?” from a judgement call into a glance.
Distribute the load properly
Two stillages carrying the same total weight can behave completely differently depending on how that weight sits inside them. Balanced loading keeps the centre of gravity low and central, which is exactly where you want it.
- Spread weight evenly across the base rather than piling it into one corner.
- Put dense, heavy items low and lighter items on top.
- Avoid tall, narrow loads that push the centre of gravity upward.
- Stop items protruding past the frame, where they foul neighbouring units or throw the balance off.
- For loose or awkward goods, use a design that contains the load — a mesh stillage for visibility and airflow, or a sheeted stillage where the load needs full containment or protection from the elements.
Matching the container to the goods is half the battle. A stillage that holds its load securely and squarely is stable almost by default; one the load can shift around in is fighting you from the start.
Stack safely: height, alignment and interlocking
Stacking is where stillages earn their keep — vertical storage that frees floor space — and where most stability discipline is spent.
Set and enforce a maximum stacking height
There is no single legal number for how high stillages may be stacked; the safe height depends on the unit’s stack-rating, the load, the floor and the environment. What matters is that you set a documented maximum for each product and location and that everyone works to it. As a rule of thumb, keep stacks well within the manufacturer’s stated stacking limit and reduce it further for heavier loads, uneven floors or draughty, exposed areas. Mark the limit visibly at the point of storage so it is not left to memory.
Align and interlock every layer
Stability depends on load passing cleanly down through corner posts and feet to the floor. That only happens when units sit squarely on one another:
- Seat each stillage fully so its feet or posts locate into the unit below — never stack part-nested or perched on an edge.
- Use only compatible, matching units in a single column; do not mix designs or footprints that do not mate correctly.
- Take advantage of built-in interlocking. Location feet, nesting features and corner-post seats exist precisely to prevent lateral movement — small components such as pallet feet and nesting plugs give a stack the positive registration that stops it “walking” over time.
- Never climb a stack or place unsecured items on top of one.
Stand stacks on stable, level ground
A perfectly loaded stack on a sloping or soft floor is still a hazard. Site stacks on firm, level surfaces and steer clear of gradients, potholes, drainage falls and ground that softens in wet weather. Where the surface genuinely cannot be levelled — a common problem in yards and on site — choose equipment designed to cope, and address the floor itself with repairs or anti-slip treatment where you can.
Storage layout: aisles, access and housekeeping
Stillage stability is not only about the stacks themselves — it is about the space around them. A well-planned storage area is a safer one.
- Keep aisles and access points clear. Operators and forklifts need room to place and retrieve units without clipping neighbouring stacks. Blocked walkways and obstructed emergency exits turn a minor topple into a serious incident.
- Give forklifts an honest working envelope. Most knocks happen during handling; adequate turning and approach space prevents them.
- Maintain good housekeeping. Debris under a stillage foot introduces exactly the unevenness you have worked to eliminate. Keep floors clean and storage zones tidy and defined.
- Consider fixed racking for the heaviest or highest storage. Where stack heights or loads are pushing the sensible limit, racking removes the cumulative-load problem entirely and can be the safer, denser answer.
Secure stillages in transit
A stack that is stable standing still is a different proposition once it is moving. Braking, cornering and road vibration all try to shift the load, and an unrestrained stillage on a vehicle bed is a genuine danger to the driver and to other road users.
- Restrain every unit with appropriate straps, load bars or bracing — do not rely on the load’s own weight.
- Load heaviest units low and forward, keeping the vehicle’s centre of gravity sensible.
- Eliminate gaps that let units slide, and check restraints before departure and again after the first few miles, when loads tend to settle.
- Follow recognised load-securing guidance for the vehicle and route.
Design helps here too. Collapsible metal pallets travel flat when empty, so return journeys carry a low, stable load instead of tall empties, and stackable designs give a predictable, restrainable footprint outbound.
Inspect, maintain and keep records
Steel is durable, not indestructible. A bent corner post, a cracked weld or a seized fold mechanism removes the very margin that keeps a stack upright — and these faults develop quietly. Routine inspection is what catches them before they matter.
What to look for
- Bent, buckled or twisted frames, posts and feet.
- Cracked, corroded or failing welds.
- Loose, missing or damaged fixings, latches and locating features.
- Rust or corrosion that is eating into structural sections.
- Signs of instability in use — leaning, wobble or movement during handling.
Take any unit showing these signs out of service immediately and quarantine it until it is repaired or scrapped. Do not return it to the stack “for now”.
How this fits UK regulation in 2026
Two sets of regulations frame stillage safety in Great Britain:
- PUWER — the Provision and Use of Work Equipment Regulations 1998. Stillages are work equipment. PUWER requires that they are suitable for the task, kept in good repair, and inspected to ensure they stay safe. Almost everything in this guide — capacity, condition, safe use, training — sits under PUWER.
- LOLER — the Lifting Operations and Lifting Equipment Regulations 1998. LOLER applies specifically when a stillage is used to lift a load. Lifting stillages and their attachments must be of adequate strength, marked with their SWL, and subject to thorough examination at the intervals the regulations require.
On product conformity, the current mark for Great Britain is UKCA (UK Conformity Assessed). UKCA is the standard to look for on manufactured handling equipment supplied into the GB market; you can read more in our guide to UKCA certification. Choosing equipment made to a recognised standard by a UK manufacturer means the ratings you rely on for stacking and lifting are engineered and evidenced, not guessed.
Document everything
Keep records of load tests, inspections, faults found and corrective action taken. Good documentation demonstrates due diligence under PUWER and LOLER, but its real value is operational: it shows which units are approaching end of life, which storage areas throw up repeat problems, and where your controls are working. Records turn safety from a reaction into a plan.
Train your people — the control that ties it together
Every control above depends on the person applying it. Operators should understand safe working loads and stacking limits, know how to load for balance, be able to spot damage and instability, and feel able to report a concern without hesitation. A workforce that treats a wobbling stack as everyone’s problem is worth more than any single piece of equipment, because it catches the problems a checklist misses.
Build stability in from the start
The most reliable way to keep stillages stable is to specify the right ones for the job — correctly rated, properly featured for stacking and lifting, and matched to your loads, your floors and your handling equipment. That is where a UK manufacturer earns its keep: we can advise on capacity and stacking, load test where certification is needed, and design bespoke stillages around awkward loads or difficult environments that off-the-shelf units simply cannot handle safely.
If you would like help specifying stable, correctly rated stillages — or want existing units assessed for safe stacking and lifting — get a quote or contact the Lowe team. We will help you build stability in from the start and keep your storage, and your people, safe.