Maximizing Warehouse Efficiency: The Pros and Cons of Two-Deep Storage Racks

When deciding whether storage racks should be installed "two deep," the answer largely depends on factors like the type of goods being stored, available space, safety concerns, and operational efficiency. Installing storage racks two deep means placing two rows of racks, or a double-depth storage system, in such a way that products are stored both at the front and behind the first row. This setup can increase storage capacity, but it requires careful consideration.

The Pros of Two-Deep Storage Racks
Maximizing Vertical Space:

One of the most significant advantages of double-depth storage is its ability to use vertical space more efficiently. By stacking racks in a two-deep configuration, a warehouse or storage area can hold more items without requiring a larger footprint. This is particularly valuable in settings where expanding the physical space is difficult, expensive, or impractical.

Increased Storage Capacity:

The clear benefit of going two-deep is the ability to store more items in the same square footage. This is especially advantageous in high-density environments where available space is at a premium. It’s like doubling up on storage without doubling the space.

Better Utilization of Space:

When you install racks two deep, you can make the most of your available floor area. Rather than spreading storage throughout a larger area, double-deep racks maximize depth, which often allows for a more organized and consolidated layout. The deeper storage locations can be more efficient for certain products or industries.

Ideal for Low-Throughput Products:

In warehouses or storage facilities where certain products do not move frequently, double-depth racks are an excellent solution. These products can be stored deeper into the rack system, leaving front-rack spaces for items that require higher turnover.

The Cons of Two-Deep Storage Racks
Access and Retrieval Issues:

The biggest drawback to installing racks two deep is the difficulty in accessing the products stored in the back row. To reach items stored behind others, operators may have to move the front-row products first, which can slow down order picking times. This can be frustrating in environments where speed and efficiency are crucial.

Increased Labor Costs:

Because of the need to access items in the back, double-depth systems might require more labor to retrieve products. This may involve the use of additional equipment, like forklifts or pallet jacks, to retrieve the second row. This can lead to increased operational costs due to the extra steps involved in order fulfillment.

Risk of Product Damage:

The more complex the retrieval process, the greater the risk of damaging products, especially if heavy machinery or improper handling techniques are used. Moving products in and out of deeper rows increases the likelihood of knocking or dropping items, particularly in high-volume settings.

Limited Product Variety:

Double-depth racks are best suited for homogeneous products or items with similar dimensions. If your warehouse stocks a wide variety of products, each with different sizes or storage requirements, a two-deep system can limit flexibility and might not be the best solution.

Factors to Consider When Deciding on Two-Deep Storage
Turnover Rate of Products:

If you deal with a high volume of fast-moving goods (FIFO – First In, First Out), a two-deep setup might not be ideal. This is because you’ll have to move products around, and it’s much slower compared to systems that allow for easier access to each item, such as single-depth or flow racks.

Type of Products Stored:

Some products require more careful handling, and the risk of damage increases with less convenient access. For fragile or perishable items, it may be more appropriate to avoid deep storage systems that create obstacles for quick, safe retrieval.

Equipment and Technology:

Modern warehouses are increasingly using automated systems and machinery like narrow-aisle forklifts and automated guided vehicles (AGVs) to handle deeper storage systems. These technologies can help mitigate the downsides of two-deep racks by enabling quick, precise access to products. However, implementing such technology requires upfront investment and infrastructure.

Space and Layout Constraints:

If you have limited space and the layout forces you to go deeper into the racks, then two-deep might be a smart choice to get more storage capacity. On the other hand, if the layout allows for easier access and greater maneuverability, single-depth racks or other forms of shelving might work better for operational efficiency.

Safety Concerns:

Double-depth racks may present safety concerns, especially if the items stored at the back are heavy or difficult to maneuver. Proper safety protocols must be in place to prevent accidents, including training for employees on the handling of deep rack systems.

Inventory Management and Tracking:

Managing inventory in a two-deep system can be more complex. It’s crucial to have a robust tracking system to ensure that products are accounted for correctly and that the most recently received stock isn't buried at the back. Warehouse management software (WMS) can help track the flow of goods and ensure proper inventory levels.

Alternatives to Two-Deep Storage Racks
Push-Back Racks:

Push-back racks are a more advanced type of storage system that allows for multiple levels of storage with better accessibility. Products are loaded from the front and automatically pushed backward when new stock is added, making retrieval easier.

Pallet Flow Racks:

These racks are designed for first-in, first-out (FIFO) inventory systems. They use gravity to move items down the rack, which makes it easier to access older products without moving others around.

Mobile Shelving:

Mobile storage racks can be moved along tracks to create wider aisles or allow access to products without needing to go two-deep. This offers a balance between maximizing space and maintaining easy access.

Single-Depth Racks:

If you don’t need to increase your storage density drastically, sticking with single-depth racks might be the simplest and most cost-effective solution.

Conclusion: To Go Deep or Not?
The decision to install two-deep storage racks should not be taken lightly. It involves balancing the need for increased storage capacity against the potential for slower access times, increased labor, and higher operational costs. The nature of the products being stored, the turnover rates, the available space, and the equipment at your disposal all play a significant role in determining whether a two-deep storage solution makes sense for your operation.

In a highly optimized, automated warehouse with good inventory management and appropriate equipment, two-deep racks can offer a valuable increase in capacity with minimal downsides. But in environments where speed, safety, and easy access are paramount, it might be worth considering alternatives like push-back or pallet flow racks. Ultimately, the choice depends on your unique requirements and operational constraints.