Narrow vs wide aisles: space against convenience

What takes up the most room in a warehouse is not the racking itself but the empty space between the racks, the aisles. In many warehouses a quarter of the floor, sometimes more, is used purely for moving around. That is why the thought "narrow the aisles and more pallets will fit" is so tempting. But for every centimetre you save you pay with something: the price of equipment, speed or safety. Before deciding, do a short calculation.

What determines aisle width

Three things: the type of equipment, the size of the load and the traffic rules. The figures below are approximate; take the exact value from each machine's data sheet (the line about aisle width):

• a standard counterbalance forklift: roughly 3.5 to 4 metres;
• a reach truck with a telescopic mast: roughly 2.7 to 3 metres;
• special very-narrow-aisle trucks that run on rails or a guide wire: roughly 1.6 to 2 metres;
• picking on foot or with a trolley: roughly 1 to 1.5 metres, and clearly more if two trolleys have to pass each other.

Even a hand pallet truck needs about two metres to turn a pallet across the aisle. So the assumption that "the machine is small, therefore the aisle can be narrow" is not always right.

The calculation: what changes when aisles shrink

A simple example. The hall is 60 metres wide. Two rows of racking placed back to back have a combined depth of 2.2 metres. That block plus one adjoining aisle forms a module, and each module contains two rows of racking.

• Aisle of 3.6 metres: the module is 5.8 metres, the hall takes 10 modules, which is 20 rows.
• Aisle of 2.8 metres: the module is 5.0 metres, 12 modules, which is 24 rows (about 20 percent more).
• Aisle of 1.8 metres: the module is 4.0 metres, 15 modules, which is 30 rows (about 50 percent more).

Narrow-aisle trucks usually lift higher, so once height is counted the gap grows further. But "50 percent more" does not tell the whole story: you also have to count the price of the equipment, the training of the drivers and the picking speed.

The hidden price of narrow aisles

• Equipment and training. Special trucks cost more than an ordinary forklift and the driver is trained separately. If one driver falls ill, is there anyone who can step in?
• The floor. Trucks with a tall mast need a flat, strong floor. On an uneven one the work is both dangerous and slow.
• Jams. Two machines cannot pass each other in a narrow aisle. If one stops, the whole aisle stops, so traffic has to be one-way and in turns.
• Collisions. The narrower the aisle, the likelier it is that a truck clips the racking. Fit protective guards at the foot of the uprights and write down every impact.

When a wide aisle pays off

In fast zones where many people work at once. A picking zone with a heavy flow of orders handles hundreds of lines an hour, and there keeping speed matters more than saving space. Cross aisles help too: if there is a way across every eight to ten bays, a picker can leave without walking the whole length of a long aisle.

The best answer is often a mix: narrow aisles in the zone holding a large, slow-moving reserve, wide aisles in the front zone for fast picking. This also fits well with ABC slotting.

How to decide

1. Measure what share of the floor is currently used by aisles: divide the aisle area by the total area.
2. Check whether you really need extra pallet places, or whether part of the existing places is occupied by old, unsold stock.
3. Work out what one pallet place costs you (rent, racking, electricity, staff) and compare that with the price of narrow-aisle equipment.
4. Escape and fire routes have requirements of their own: before narrowing an aisle, confirm them with the responsible service.

Conclusion

A narrow aisle saves space, a wide one saves time; a good warehouse shares them out by zone. In a warehouse audit, SkladKontrol shows how much of the floor goes on storage and how much on movement, and helps back the layout decision with numbers rather than guesses.