Every warehouse that outgrows a handful of shelves reaches the same question: do we buy racking for this stock, or keep stacking pallets on the floor? For some stock, floor stacking (block stacking) is the right answer, and racking would be money spent to make the floor plan worse. For other stock it is the wrong answer, and you only find that out when a crushed pallet or a buried delivery costs more than the racking would have.

The decision is not made for the whole warehouse. It is made stock line by stock line. This article gives you the test to run on each one, in the order that usually settles it.

What block stacking actually is

Block stacking means pallets stand on the floor, one on top of another, in lanes. There is no steel between them. That has two consequences that decide everything else:

• The load carries the load. The bottom pallet, its boards and its goods support every pallet above it. In racking, the beams carry each pallet; nothing rests on the pallet below.
• Access is by lane, not by pallet. A lane is filled from one end and emptied from the same end, so the last pallet in is the first out. To reach a pallet in the middle of a lane you move the ones in front of it.

Block stacking uses no racking, which is its appeal. Everything below is about when that saving is real and when it is borrowed against something else.

Test 1: how many pallets of each line do you hold?

Lane storage works when a lane is filled with one line and emptied before another is put in. If you hold many pallets of a few lines, lanes fit naturally. If you hold one or two pallets of many lines, every lane is either nearly empty or mixed, and a mixed lane is a problem: the pallet you need is under, or behind, one you do not.

Count your lines and the number of pallets each holds at its typical level, not at the peak. Lines that hold a full lane or more are candidates for block stacking. Lines that hold one or two pallets belong on racking positions, where every pallet can be reached without moving another. Our note on working out how many pallet positions you need covers the counting.

Test 2: can the goods take the weight?

This is the test that cannot be guessed. Ask two questions and get the answers in writing:

• What stacking limit does the product's packaging carry? Cartons, drums, bags and shrink-wrapped loads all have a limit, and the manufacturer or packaging supplier is the source for it. Loads that arrive marked with a maximum stacking height are telling you; loads with no marking need the question asked.
• What is the pallet rated to carry when stacked? A pallet's rating depends on its construction and its condition, and the pallet supplier is the source for the static stacking figure. Do not assume a pallet that works well on racking beams will also carry a stack of loaded pallets on its bottom boards.

Whichever of those two limits is lower is your stack height for that line. It is not the height the forklift mast can reach and it is not the height of the ceiling. If the limit means only two pallets high, the floor area you need is roughly double what a four-high plan would suggest, and the saving over racking shrinks with it.

Test 3: does the order things leave in matter?

Because a lane empties from one end, block stacking runs stock on a last-in, first-out basis. That is fine for a product that never expires, is never batch-controlled and is interchangeable pallet to pallet. It is a real problem when the first delivery has to go first: food, chemicals, anything with a batch or expiry date, and any customer stock you must release in receiving order.

Selective racking makes first-in, first-out straightforward, because each pallet position has its own access. If you block-stack a line that needs first-in, first-out, the effort moves to people: rotating lanes, emptying and refilling them, and checking dates by hand. That cost is real, recurring and easy to overlook when the plan is drawn.

Test 4: what condition are the pallets in?

In a block stack every pallet is a structural component for the pallets above it. A cracked bearer or a missing bottom board that a beam might tolerate for a while can fail under a stack. Loads arriving on mixed, second-hand or repaired pallets are the hardest case, because the weakest pallet in the lane decides the lane.

If you cannot control pallet quality at goods-in, the honest options are to rack the line (where the beams take the load and, with decking, the pallet's job is smaller) or to block-stack it only at a lower height. We set out the faults to look for in what damaged pallets do to your racking; the same faults matter more, not less, when there is no beam under the pallet.

Test 5: what does the floor cost you?

Block stacking spends floor area to save steel. In a Singapore industrial unit the floor is the recurring cost: rent, service charge and the years left on the lease. Two things follow.

• Lanes need aisles. Each lane still has to be reachable and the forklift still has to turn, so the aisle width follows the truck, not the pallet. Our note on forklift turning radius and aisle width applies to floor stacks as much as to racking.
• Lanes do not use the height of the building. Racking is how you turn clear height into storage positions. A block stack stops at the stacking limit from Test 2, and whatever height is above it is paid for and empty.

Also check the lease for floor loading. A stack puts its weight onto the slab differently from racking baseplates, so the floor rating in your lease or from the landlord is a question for both, not only for racking.

Test 6: is it safe and permitted where you put it?

Stack heights, clearance below sprinklers, and keeping exits and fire routes clear are fire-safety matters, and they apply to floor stacks in the same way as to racks. Do not treat a block-stack area as exempt because it has no steel. Put the proposed stack heights and lane positions in front of your qualified person, and confirm with SCDF where they say to, before you fix the floor marking. We cover the racking side of this in SCDF sprinkler clearance above racking.

Reading the results

Put each line through the tests and a pattern usually appears:

• Block-stack candidates: few lines, many pallets per line, goods that take a stack, no strict receiving order, sound uniform pallets, and enough floor that the lanes do not push out something you need.
• Racking candidates: many lines with few pallets each, fragile or unmarked loads, batch or expiry control, mixed or tired pallets, or a unit where height is the resource you are short of.
• The middle: lines with many pallets per line that cannot be stacked on each other. This is what deep-lane racking is for: the frames carry the load, so the stacking limit stops mattering, while you keep lane density. Drive-in racking is the usual example, and it comes with its own trade-off in access.

Most warehouses end up with a mix, which is normal. The mistake is deciding the whole building on one stock line, usually the biggest one, and then discovering that the smaller lines have nowhere to go. A designed floor-stack area for the right lines, sized deliberately and marked, sits comfortably beside racking. We describe the same idea for peaks in designing racking for peak, not average.

What to send a racking supplier

You will get a much better answer if you send a short list rather than a floor area. For each stock line: pallets held at a typical level and at the peak, pallet size, the goods' stacking limit if known, whether first-in, first-out matters, and the pallet condition you receive. Add clear height, the floor rating from the lease and the truck you use. Pricing follows a site survey; nothing here is a quotation.

The short version

Run the tests on each stock line, not the whole building: pallets per line, what the goods and pallets can carry, whether order matters, pallet condition, what the floor costs you, and what your qualified person and SCDF will accept. Block stack the lines that pass, rack the ones that do not, and use deep-lane racking for the ones in between.

If you are deciding which lines to rack and which to leave on the floor, message us on WhatsApp or see our racking systems page for the systems and published bay ranges.