Warehousing is a game of space vs. time. Designing an efficient warehouse requires balancing storage capacity (space) against throughput and productivity (time).

That's according to comments by Robert Silverman, president of the consulting firm Gross & Associates, at the recent Warehousing Education and Research Council annual conference.

Most warehouse operations, says Silverman, waste a lot of time and space. In a typical warehouse, he says, only 10% of the cubic space is actually occupied by product. Likewise, warehouse workers spend most of their time doing their least productive task—traveling.

"You really want to do everything you can to reduce travel times," says Silverman. What techniques works best? "The No. 1 thing is slotting," he says.

Silverman advocates slotting as a way to not only reduce travel times but also to improve ergonomics for pickers and reduce congestion in aisles.

Silverman offers these additional suggestions for saving time:

• Use machinery—such as carousels, conveyors and sortation system—to bring work to employees.
• Establish forward picking zones.
• Use system-directed putaway and replenishment.

Silverman also provids these space-saving tips:

• Use different trucks that result in narrower aisles.
• Optimize column spacing in new buildings.
• Choose materials handling systems—such as carousels and high-bay storage systems—that better use the cube.
• Find creative ways to use overhead space (i.e. elevated conveyors).
• Collect good cube information to assist in planning (i.e. scan cartons to determine their dimensions).

Because most warehouses devote only 10% of the cube to storage, says Silverman, increasing cube use by just 2-3% can have a 20-30% impact on storage capacity.