Our daily lives have no strict rules about what is too close for comfort. Some people go through life blissfully unaware that they make people uncomfortable by intruding on their space. Pallet racking clearance, however, has more specific regulations and guidelines that dictate the minimum distance between racking and the building's structure to comply with safety rules like OSHA regulations.
Pallet racks are structures designed to be self-sufficient and freestanding. Building components (i.e., walls, building columns, beams, etc.) are not typically designed to support additional loads from neighboring structures, which is why storage rack clearance is so important. Connecting pallet racks to building components allows forces to transfer between them, which could have unintended consequences. Unless a structural engineer specifically designed the structures to interact, connecting pallet racks to building components is not recommended and could prove dangerous.
Ensuring warehouse racks are not connected to a building component is insufficient. To prevent contact between building components and pallet racks through vibrations (caused by activities in the warehouse, impact, or a seismic event), a specific storage rack clearance from the building's structure should be respected. Unless you have previously determined by seismic analysis the amplitude of movement of the racks, current standards require a minimum warehouse racking clearance equal to:
The hatched area in Figure 2 represents the required clearance between a warehouse rack and the building structure.
In the event of an impact or seismic activity, a pallet rack could damage a building component if it’s too close, compromising its load-carrying capacity. The rack could also damage non-load-bearing components such as non-supporting walls, plumbing or electrical infrastructures, sprinkler systems, and other warehouse equipment. Figure 3 shows an example of an upright that does not respect the recommended clearance distance between pallet racking and a building column.
Multiplying the height of your pallet rack times 0.05 for down-aisle or 0.02 for cross-aisle directions will allow you to determine your storage rack clearances. For example, if your pallet rack is 240 inches tall (20 feet), the required clearance would be 12 inches (5% of 240) in the down-aisle direction and 4.8 inches (2% of 240) in the cross-aisle direction.
If you are certain that the topmost beam elevation will not be modified over time, the topmost beam height can be used instead of the rack's total height to determine the required distance between pallet racking.
Aside from storage rack clearance and the distance with the building components, there are other clearances to keep in mind in your warehouse. Storing pallets within the recommended clearances will reduce damage to pallet rack components and ensure safe and efficient operation.
Minimum clearances for proper handling and protection of pallet racks are recommended. Required general clearances for single deep/double deep pallet racks are listed in Table 1 below.
Table 1: Recommended storage rack clearances for single-deep and double-deep pallet racks
| # | Clearance Guideline | Recommended clearance space |
|---|---|---|
| 1 | Between two loads and between one load and the upright frame | At least 3 in. |
| 2 | Between the load and the overhead beam | At least 3 in. (and more for safe handling at top levels) |
| 3 | Pallet overhang | Between 2 and 4 in. over the front and back beams |
| 4 | Between two loads in back-to-back cells | At least 4 in. |
| 5 | Service aisle |
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| 6 | Main aisle | According to the lift truck manufacturer’s recommendations |
| 7 | Between load and an automatic sprinkler system | At least 18 in. |
| 8 | Walkways |
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As shown in the table above, pallets should have a minimum clearance of 3 inches between two pallets or one pallet and the upright frame to avoid damage or unintended impacts with rack components. Lift truck drivers should pay close attention and ensure adequate space on both pallet sides when placing pallets.
Figure 5 below shows a pallet stored directly against a column. Disregarding the recommended storage rack clearance can damage the pallet rack components.
Pallet racks are efficient structures for storing large quantities of heavy merchandise, but standards must be followed to ensure they are used safely and remain free of damage. Following the minimum distance between racking and respecting clearance from building components is important.
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