If you've been assuming that the concrete floor in your warehouse is nothing to worry about, then you could be in for a surprise. Floors are under more stress now than ever before, says Andrew O'Brien, business development manager for Performance Structural Concrete Solutions LLC. One reason is that the taller racking that's common today carries greater loads, placing more stress on floors. Another is that electric forklifts' small, hard wheels are tough on concrete. And in spec-built facilities, the cost-conscious developer may not have designed the floor to stand up to high traffic and heavy loads.
Concrete floors can develop cracks, bumps, depressions, and "spalls" (broken-up or pitted areas), which can damage forklifts, driving up maintenance costs and sometimes causing ergonomic problems and injuries. Moreover, operators must slow down in problem areas. In a large facility with multiple shifts, even a one-mile-per-hour reduction in speed can reduce productivity enough to add hundreds of thousands of dollars in labor costs, O'Brien says.
Floor damage is a problem for automated equipment, especially driverless vehicles, which require extremely flat, smooth surfaces to operate properly, O'Brien observes. Also at risk are high-reach trucks. When a bumpy floor makes the truck tilt, that tilt is magnified as the mast rises. A deviation of just 1/4 inch, for example, could cause the mast to lean as much as 12 inches at the top of a 60-foot rack. That slows picking and putaway, especially in very narrow aisles where there's little room to maneuver.
Joints between slabs can become problems, too. A joint that may have been 1/8-inch wide when new can expand, crumbling around the edges from the impact of forklift traffic and filling with debris (see photo). And when interconnected concrete slabs lack load-transfer mechanisms, such as dowels, a forklift's weight can depress one slab, creating a height difference between it and the adjacent slab—a phenomenon known as "rocking." If the difference is great enough, the truck's tires will slam into the edge of the higher slab.
O'Brien offers some suggestions for avoiding such problems:
- When leasing buildings, verify that the floor was designed to handle your current and future load weights for racks and material handling equipment.
- Conduct inspections at least twice annually. Fix floors that are no longer level, address early signs of damage, and repair damaged floor joints.
- Install "joint-free," steel-fiber-reinforced concrete floors. They do have joints, but far fewer and of a different type than in traditional designs.
- Consider "armored" joints instead of joint filler. Depending on the design, these steel structures, which must be installed before the floor is poured, spread or even eliminate the impact of a forklift's weight, protecting against joint deterioration and eliminating shock and vibration in the truck.
O'Brien emphasizes the importance of quick action on floor damage, which "can go from bad to really bad in a fairly short time." It can be expensive to shut down a section of your DC for a floor repair, but the longer you put it off, he says, the greater the damage will become, "and the more it will hurt you every day."
