Warehouse layout: shelf types and ABC placement
Pallet shelving carries many tons of goods high above the heads of people working below it. An overloaded, damaged or incorrectly mounted shelf can collapse and kill. Shelf safety is therefore not just the warehouse manager's responsibility — as an employee you are the one who sees the damage happening and can stop it in time.
Two warehouses with same goods and same storage space can have widely different productivity — difference lies in layout. Each time a product gets poor placement cost is paid in form of extra driving and walking time every single time product is fetched. Good warehouse layout is therefore about matching three things: product's physics (size, weight, durability), product's turnover rate, and shelf type that fits both
§Shelf types and their logic
The ordinary pallet racking is the warehouse's workhorse: direct access to each pallet, flexible and suitable for many item numbers. If you want to exploit the space harder, there are compact solutions: in a drive-in racking, the truck drives into the racking itself and places pallets in depth — it gives high filling grade, but only access to the front pallet, so the principle becomes LIFO (last in, first out). Through-flow racking solves that problem with roller conveyors and inclination: pallets are inserted from behind and slide forward to removal in front, so the oldest pallet is always taken first — FIFO is built into the steel. Push-back racking fills in depth from the same side and is thus also LIFO. For long goods such as pipes, strips and profiles, cantilever racking is used with cantilevered arms without front posts, and for small items, shelf racking is used, often in multiple levels on a mezzanine.
| Shelf type | Access | Principle | Suits |
|---|---|---|---|
| Pallet shelving, deep stacking, throughput and aisle shelving — and the art of giving goods the right address | Direct to each pallet | Free choice | Many item numbers mixed flow |
| Deep stacking (drive-in). | Only the front pallet | LIFO | Get product numbers in large quantities |
| Through-access shelf | In from the back, out from the front | FIFO | Dated goods and high flow |
| Push-back | In and out from the front | LIFO | Compact buffer with few item numbers |
| Cantilever rack | From side/front | Free choice | Long goods: pipes, plates, strips |
§Fixed or moving location?
Any space in the warehouse must have an address — typically aisle, section, shelf and location (e.g. 03-12-2-1). In fixed location each product has its fixed space: easy to remember but space stands empty when product is sold out. In floating location the system chooses an available space during storage and remembers where the product ended up: better space utilization but entirely dependent on all movements being scanned. Most warehouses combine: fixed picking locations at grip height and floating buffer locations in height from which the picking location is replenished.
§ABC placement: give A-items the prime locations
An ABC analysis ranks item numbers by activity — usually number of picks. The pattern follows Pareto's principle: a small portion of item numbers account for the vast majority of picks. A-items should therefore be located at the warehouse's best locations: close to the packing area, at ergonomic picking height, and with enough space to avoid constant replenishment. C-items can be located at the periphery and at height. The analysis is fresh data — season and assortment shift, so placement should be reviewed at regular intervals.
- 01Place A items close to packing and between knee and shoulder height
- 02Heavy goods at the bottom — both for ergonomics and shelf stability
- 03Dated goods in flow-through shelves or with strict FEFO control
- 04Keep aisles free: a blocked aisle costs the entire warehouse's tempo
- 05Review ABC-placement at least a couple of times a year
§Flow through the building
Zoom out last from the shelf to the whole building. A warehouse with a door at each end can be set up as a flow-through warehouse where goods move in one direction from receipt to shipment — simple flow, but a long way to drive for fast movers. A U-warehouse collects receipt and shipment at the same end, so A-goods can live close to both. There is no one right answer; the right layout is the one that minimizes the total transport time for exactly your product mix. Draw the flow, measure the distances — and let the numbers decide.
“The warehouse's most expensive square meters are those closest to the gate — use them for the goods that move the most.”
— Basic rule in warehouse layout