Pallet storage and safe stacking: a practical guide

Pallet storage is one of the most underrated parts of running a warehouse. It is a workplace safety risk and a question of money at the same time: a toppling stack can injure people and damage goods, and a badly stored pallet loses its value within a few months. Both problems are solved by the same measures, and they cost next to nothing. This guide covers how high pallets should be stacked, what kind of base and location work, how a floor stack differs from pallet racking, how the Finnish winter affects all of this and how to work out what poor storage is costing you.

We collect and sort used pallets every day, so every week we see the difference storage makes. Two batches of the same age can be worth completely different amounts simply because one was kept under a shelter and the other out in the yard.

Two reasons why the way you store pallets matters

Safety. A pallet stack is heavy and tall, and when it falls, it falls fast. Typical incidents include crushed feet and fingers, people being hit by a falling stack and a forklift driver’s view being blocked by a stack that is too tall. Under Finland’s Occupational Safety and Health Act (738/2002), the employer must make sure that goods are stored safely.

Value. A pallet is an item with resale value, and that value disappears with moisture. A pallet kept under a shelter is still saleable a year later; the same pallet left in the yard may not be. Read more in the article on pallet lifespan, and about how condition is graded in the article on pallet grades A, B and C.

How high can you stack pallets?

There is no single statutory maximum height, because the safe height depends on the pallet type, its condition, the base and the handling method. In practice, the guidelines are as follows.

A commonly used rule of thumb for a free-standing stack is that its height should be no more than about three times the stack’s shorter side. Because a pallet is 144 mm high, the rule can be converted directly into a number of pallets.

This explains why the general guideline of ”15-20 pallets” holds true but needs qualifying: for a FIN pallet 20 is justified, for a EUR pallet it is already above the recommendation and for a half pallet it is clearly too many. In practice, 15-16 pallets is a safe upper limit for most pallets, and smaller pallets should be stacked lower. The rule is a guideline rather than law, but it is a good starting point when you have nothing else to go on.

How to stack pallets correctly

Empty pallets

An empty pallet stack usually topples for one of three reasons: the stack is leaning, the pallets are different sizes or the base is not level. All three are easy to prevent.

• Sort by type before stacking. Putting EUR and FIN pallets in the same stack is the most common cause of a leaning stack, because the pallets are different sizes.
• Align the edges. Each pallet goes directly on top of the one below, not overlapping and not crosswise.
• Put damaged pallets in a stack of their own. A warped or broken pallet does not belong in the middle of a stack.
• Keep stacks at an even height. That way you can see the quantity at a glance and the stacks support each other side by side.
• Leave a walkway. Stacks need space around them for forklifts and pedestrians, not just for the forks.

Loaded pallets

With loaded pallets, it is the load that matters, not the pallet. The load on the bottom pallet has to carry everything above it, so stacking only works if the load is even and sturdy.

• Heaviest at the bottom. This is the single most important rule.
• Spread the load evenly over the whole pallet. Weight piled up in the middle bends and topples the stack.
• Use a sheet or lid between the layers. It spreads the weight instead of the pallet above pressing down on a single point of the load below.
• Stretch-wrap or strap before stacking. A loose load carries nothing.
• Do not stack on top of a damaged pallet. Always check the bottom pallet before anything is lifted on top of it.

The base matters more than you might think

The bottom pallet is the weakest point of the stack, and it takes the most punishment. A pallet standing directly on asphalt, gravel or a concrete floor absorbs moisture from below, even if it never rains.

The fix is cheap: lift the stack off the ground. Two timber bearers, two sacrificial pallets or something similar is enough. It also lets the forklift forks slide underneath easily, so the bottom pallet does not have to be dug out. The base must be level and firm, because on soft ground the stack starts to lean under its own weight.

Indoors, under a shelter or outdoors

This is the decision that has the greatest effect on the value of your pallet stock. Below, the options are compared side by side.

A pallet stack also takes up floor space that you pay rent for. How organising the flow of pallets frees up storage space is explained in the article on selling surplus pallets and freeing up storage space.

Note the word ”seemingly” in the last row. Outdoor storage costs nothing at the time, but it eats away the pallet’s resale value and eventually creates a disposal cost. It is a cost that simply shows up later.

Moisture destroys a pallet’s value

Wood absorbs water quickly and releases it slowly. Three things happen in sequence to a pallet that gets wet: its weight increases, the joints loosen even under normal handling and, eventually, mould sets in. A mouldy pallet cannot be used for transporting food or consumer goods, and it has no resale value.

To give a practical sense of scale: a month in the rain is enough to turn a pallet in good condition into one that nobody will pay for. This is the most common reason a company gets less for its surplus pallets than it could have. Advice on the selling side can be found in the article on how to sell surplus pallets.

Pallet racking is not the same as a floor stack

In racking, the pallet carries its load supported only by the beams, so the deck boards are stressed in a completely different way than on the floor. That is why the racking load capacity is lower than the load capacity on the floor, and it must be checked separately. The different types of load capacity are explained in the article on pallet load capacity in practice.

Racking also comes with its own inspection obligation that many people are not aware of. Finnish occupational safety legislation requires the condition of racking to be verified, and the European standard SFS-EN 15635 (the Finnish edition of EN 15635) describes how the inspection is carried out. In practice, this means the following:

• Periodic inspection at least every 12 months. The inspection is carried out by a technically competent person.
• A report is drawn up after the inspection. It records the damage found, its severity and the corrective action.
• Damage is classified on a three-level scale. Green means monitoring, amber means repair and red means the rack location must be emptied immediately.
• Load notices on display. The permitted loads of the racking must be readable wherever pallets are lifted.

If racking has been damaged in a collision, it should not be used until its condition has been assessed. A forklift hitting an upright is the most common cause, and the damage often looks less serious than it is.

The Finnish winter: snow, ice and thaw

This is missing from most storage guidelines, even though in Finland it covers a large part of the year. Winter brings three problems to pallet stacks, and the last one is the worst.

1. Snow load. Snow building up on top of the stack weighs down the top pallet and overloads the stack. Snow collecting on a cover can also tear the cover off.
2. Freezing to the ground. A bottom pallet standing directly on the ground freezes to the surface, and prising it loose with a forklift breaks the blocks. Lifting the stack off the ground prevents this completely.
3. Thawing and refreezing. The single worst factor. Snow melts into the pallet, refreezes and, as it expands, splits the wood and loosens the joints. In Finland this happens dozens of times over a single winter.

Practical advice for winter: do not leave pallets outdoors over the winter. If a pile has built up in the autumn, arrange a collection before the frosts set in. That is cheaper than waiting for spring, by which time the same pile has lost its value.

Keeping the loading area in order

Where you place the stacks affects both safety and how quickly a collection goes. A few things are worth thinking through in advance.

• Stacks close to where the vehicle stops. A short distance means less handling and less damage.
• Visibility must be maintained. A stack that is too tall on the corner of a junction blocks the forklift driver’s view.
• Keep pedestrians and forklift traffic apart. Mark the walkways if the area is busy.
• Keep stacks away from emergency exits and clear of fire extinguishers. This is easily forgotten when a pile grows gradually.
• Room for the forks from every direction. A stack crammed against a wall has to be taken apart by hand.

How the pallet type affects stacking

Not all pallets can be stacked the same way, because the construction is what counts. A lightweight pallet can bear its own weight, but not ten identical pallets on top of it.

A practical rule: if in doubt, make the stack lower. A toppled stack always costs more than the floor space for two extra stacks.

Who is responsible for what

Safe storage often fails because nobody feels it is their job. It pays to agree on responsibilities out loud, because that is the fastest way to make the practices stick.

• The employer is responsible for organising storage safely and for having the racking inspected at regular intervals.
• The supervisor decides where the stacks go and how high they may be, and makes sure everyone has been told.
• The forklift driver is responsible for not building stacks higher than agreed and for taking damaged pallets out of circulation.
• Everyone reports a leaning stack, damaged racking or wet pallets immediately, not at the next meeting.

A single A4 sheet on the wall of the loading area is enough: it states the maximum height, where the stacks are placed and who to report deviations to. It costs nothing and keeps the practices in place better than a one-off induction.

How to calculate what poor storage costs you

This calculation is worth doing once, because it turns the discussion from opinions into numbers. The formula is simple:

Compare the figure with the price of a shelter, or even of a proper cover. In most companies where pallets move regularly, the investment pays for itself within the first year. How pallet prices are formed is explained in the article on pallet prices.

The most common pallet storage mistakes

• The stack stands directly on the ground. The bottom pallet is ruined and freezes to the ground in winter. Two timber bearers fix this.
• Different pallet types in the same stack. Pallets of different sizes make the stack lean and prone to toppling.
• Outside ”temporarily”. Temporary storage drags on, and within a month the value has gone.
• The stack grows so tall that it cannot be handled. Taking the top pallet down from above head height is always a risk.
• Damaged pallets mixed in with intact ones. A warped pallet in the middle of a stack is where toppling starts.
• The racking inspection is forgotten. The annual inspection is an obligation, not a recommendation.
• The pile is allowed to grow for months. The oldest pallets deteriorate at the bottom while you wait for a bigger collection.

Pallet storage in brief

Once a pile has built up, it pays to clear it

The best storage solution for surplus pallets is not to store them at all. When the pile is a reasonable size and the pallets are still in good condition, it makes sense to sell them on rather than leave them waiting in the yard.

The same applies to pallet collars; how to check their condition is covered in the article on used pallet collars. We buy used pallets and pallet collars from companies and collect them with our own trucks from our base in Hyvinkää. If pallets build up regularly, it is worth agreeing on a recurring collection: that way the pile has no time to grow and the pallets have no time to suffer from the weather. Choosing a supplier is covered in the article on how to choose a pallet supplier.

Summary

In pallet storage, safety and monetary value go hand in hand. The stack that is even in height, straight and off the ground is also the stack that will not topple and whose pallets will still be usable a year from now. The single most important factor is protection from the weather: a shelter is the cheapest investment you can make in your pallet stock, and if you do not have one, a cover and timber bearers deliver most of the benefit.

The rest of pallet storage comes down to practices that cost nothing: sort by type, keep stacks at a reasonable height, put the heaviest at the bottom when stacking loaded pallets, keep walkways open and remember the annual racking inspection. And if the pile keeps growing, do not wait for spring.

Frequently asked questions