One of the most common, and surely, the most mundane of all storage methods is the stacking of pallets on the floor. With no racks to buy, and little space devoted to aisles, it seems like a natural. Perhaps because it is viewed that way, there is some untapped potential for improving its usefulness.

The two key questions are: "How high should we stack the pallets, and how long should the lanes be?" Beyond that, there are some very interesting procedures to consider.

Generally, we would stack as high as the building height will permit, and as the pallets will safely stack. "Safely stack" is sometimes difficult to determine. It is affected by the compressive strength of the lower pallet loads, the stacking pattern of the cartons and the quality of the pallets.

Cartons that are not completely filled, or that contain soft products depend on the carton strength for stacking, rather than on the product inside. Wear and tear from multiple handlings and transportation weaken the carton so that its strength at the end of the supply chain is not what it was at the beginning.

Humidity, too, takes its toll. Recently, I was in a warehouse where two-high was too high. Check with carton suppliers to see if a small change in board strength or glue will add a pallet or two to the stacking strength.

Because the longer the lanes are the more aisles we can eliminate, there is a tendency to layout the warehouse with lanes seven to ten pallets deep. While this might be appropriate for the most popular products, it generally creates severe "honeycombing" loss for the rest. A lane may start out full, but once we begin to remove pallets, the utilization of the spaces in the lane will gradually fall to zero. Shorter lanes, even for popular products, will result in fewer broken lanes, and less honeycombing.

Pallet racking should be provided for slow moving products with fewer than 15 pallets in inventory. It can also be used to clear the last few pallets in a long lane to make it available for assignment to a new product.

Permanent assignment of products to specific lanes ensures that the fastest movers are in the best locations. But, as inventories fluctuate, many lanes may be left empty. A better alternative is to randomly assign products to available lanes in a zone close to the dock, and designated for only fast movers.

If we receive and ship a popular product regularly, but for some reason must carry a large safety stock, the inventory in excess of the regular activity should be slotted at the back of the warehouse. A spike in demand may force us to go to the remote location for the product. But in the meantime, we will have shortened the travel path considerably for the fast moving products. Normally, we can maintain sufficient rotation of stock by moving a small portion of the flow through the reserve storage.

Generally, we take a dim view of mixing different products in a lane. However, we recently encountered a situation in which it seemed appropriate to borrow empty space in a lane of slow moving product to use for pallets of fast movers that we knew would be gone before we needed any of the slow mover.

CAUTION! Don't try this at home—at least not without the help of a good scheduling and control system.