Understanding the Correct Pallet Rack Height-to-Depth Ratio

While beam load capacity, the height of uprights, and load distribution are commonly focused upon while designing pallet racking, the height-to-depth ratio is a critical element that often gets overlooked. Without understanding the proper height-to-depth ratio of your pallet racks, you can risk equipment failure, creating an unsafe warehouse, and damaging your stored products.

According to the Rack Manufacturers Institute (RMI), a pallet rack’s height-to-depth ratio is “the ratio of the height from the floor to the top surface of the top load-supporting beam level divided by the depth of the frame. The depth needs to be measured from the outside of the column to the outside of the column at the floor.” In short, the HTD describes how tall a rack is compared to the width of the base.

The ratio is important to know because of its implications on your storage capabilities. For single rack rows, the RMI states that the pallet rack must maintain a 6:1 ratio to be applied with standard anchoring.

In Example A in the image above, you can see that the racking illustration that is 240” (20 feet) tall and 42” (3.5 ft) has a ratio of 5.71, within the recommended ratio of 6:1. Example B, where the racking is 264” (22 ft.) x 42” (3.5 ft), the HTD ratio becomes 6.28, meaning additional safety measures need to be followed to keep employees and equipment safe.

What is Needed if the HTD Ratio is Above 6:1?

If your rack exceeds that ratio, you must take additional actions such as adding base plates, overhead rack ties, or specialty anchors. Additionally, your rack configuration may need to be certified by a structural engineer.

The reason for this 6:1 ratio is that anchorage is designed to resist an “overturning force” of 350 pounds at the top shelf level of an empty rack. Most rack manufacturers and distributors understand this and are within their required specifications. However, other variables should be considered when applying this “rule of thumb.” For instance, if the design uses Limit State Design or Load and Resistance Factor Design, two nontraditional methods, the force should be considered “live” and multiplied by 1.6.

What is Needed if the Height-to-Depth Ratio is Above 8:1?

The RMI has additional requirements in the rare case that height-to-depth ratios exceed 8:1. Overhead ties are required in those instances, and anchor design must be engineer-certified.

What is Needed to Know if the HTD is Within the Required Height-to-Depth Ratio?

Just because your pallet rack height-to-depth ratio is within RMI standards, it does not guarantee stability in all scenarios. In areas of seismic activity, additional engineering may be required. If storage is outdoors, the racking configuration may need to consider potential wind and increased wear-and-tear.

What is Needed if I am Not Confident in My Racking Structure?

As a reminder, this guide is only a guide and should only be used for informational purposes.

If you have questions about the height-to-depth ratio of any pallet rack in your facility, you can contact a Storage Solutions expert today. We regularly work with our partners on rack safety surveys and facility safety surveys across North America. Additionally, you could connect with your racking manufacturer directly.

It is imperative that you have confidence in the safety and structure of your pallet racking. If you are unsure or unconfident in any way, take action to ensure safety in your facility.