Rack and Block Storage

Rack and block storage are two fundamental warehouse forms in fulfillment logistics. In rack storage, goods are stored in defined compartments, levels, or containers on racking systems, while block storage stores goods loosely or stacked on the floor in contiguous areas. Both forms have their place – the right choice depends on item size, turnover speed, available hall height, and picking strategy.

In e-commerce fulfillment, rack and block storage are rarely operated in isolation. Professional warehouses typically use a hybrid structure: fast movers and small items in rack storage, bulky pallet goods or reserve stock in block storage. Those who plan this division carefully reduce travel distances, lower pick errors, and use expensive floor space efficiently.

What is Rack Storage?

Rack storage uses vertical and horizontal racking systems to store goods in a structured and addressable manner. Each item receives a fixed or dynamically assigned storage location, which is recorded in the WMS. Typical racking systems in fulfillment include shelf racks, pallet racks, flow racks, heavy-duty racks, and automated small-parts warehouses (e.g., shuttle or miniload systems).

Characteristics of Rack Storage

• Unique storage location addresses for each SKU or container unit
• High area and volume density through use of hall height
• Suitable for pick-by-location and scanner-supported order picking
• Clear separation of items, batches, and quality levels possible
• Investment in racking technology, signage, and possibly lift trucks required

Rack storage is particularly suitable for items with high product variety, small to medium dimensions, and regular picking demand – i.e., for the typical online shop with hundreds to thousands of SKUs.

What is Block Storage?

In block storage, goods are stored on the floor without a fixed compartment structure – usually palletized, stacked, or in mesh boxes. There is no individual storage location address at compartment level, but rather zones or area designations (e.g., "Block A, Row 3"). Block storage is primarily used for heavy, bulky, or very high-volume goods.

Typical Use Cases in Block Storage

1. Reserve and excess stock storage for seasonal peaks
2. Pallet goods with low withdrawal frequency
3. Bulky goods such as furniture, fitness equipment, or building materials
4. Intermediate storage between goods receipt and repacking
5. Bulk storage of homogeneous batches with FIFO principle

Block storage is less expensive to acquire than complex racking systems, but consumes more floor space per storage unit and makes precise inventory management at individual item level more difficult.

Rack Storage vs. Block Storage: Direct Comparison

Comparison of the two warehouse forms based on floor space consumption, investment costs, picking speed, inventory transparency, and suitability for various item sizes.

The decision between rack and block storage is rarely an either-or question. Rather, it is about the optimal mix within the warehouse types and strategies of a fulfillment operation.

Racking Systems in Fulfillment in Detail

Shelf Racks

Shelf racks are the backbone of many e-commerce warehouses. They enable storage of individual cartons, containers, or loosely packed items in clearly addressable compartments. Ideal for pick zones with high product variety and medium turnover.

Pallet Racks

Pallet racks store full or partial pallets at defined pallet storage locations. They combine rack structure with the standard pallet as a storage unit and are suitable for reserve stock that is regularly moved into the pick zone.

Flow Racks (FIFO/LIFO)

Flow racks enforce a specific withdrawal sequence: goods are stored from one side and withdrawn from the other. Particularly relevant for perishable goods, batches with expiration dates, or when the FIFO principle must be strictly observed.

Automated Racking Systems

With high throughput and limited staff, larger fulfillment centers use automated small-parts warehouses or shuttle systems. These systems combine rack storage logic with mechanical withdrawal and drastically reduce travel distances – at a correspondingly high investment.

Block Storage: Organization and Control

Even in block storage, clear rules are needed, otherwise chaos ensues. The following organizational principles have proven effective:

• Zone division by product group, supplier, or turnover class
• Floor markings for aisle widths, stack heights, and safety distances
• Maximum stack height per item class defined and enforced
• FIFO labeling on block rows for batch-controlled goods
• Regular stock counting at defined intervals

Process Flow: Replenishment from Block to Rack Storage

Planning: When Rack Storage, When Block Storage?

Planning begins with an ABC analysis of items. A items (high turnover) belong in pick-near rack zones. C items (rarely withdrawn) can be in block storage or high-bay reserve zones. In between lies the gray zone: medium movers that, depending on size and weight, end up in shelf racks or at pallet storage locations.

Decision Criteria at a Glance

For the structural implementation of racking systems and overall warehouse layout planning, it is worth looking at racking systems and warehouse layout.

Integration with WMS and Order Picking

Both rack and block storage must be correctly mapped in the WMS. In rack storage, storage location management is central: every booking (storage, relocation, withdrawal) references a specific address. In block storage, zone or area booking is often sufficient – though at the cost of granularity.

WMS Requirements by Warehouse Form

Rack storage:

• Storage location management with capacity checking
• Pick route optimization by aisle sequence
• Support for dynamic slotting changes
• Integration with scanner and pick list

Block storage:

• Zone and area booking
• Batch and pallet tracking
• Replenishment trigger at minimum stock in pick zone
• Forklift and material handling equipment coordination

Safety and Occupational Health

Rack and block storage are subject to different safety requirements. Racking systems must be properly anchored, regularly inspected for damage, and equipped with load signs. In block storage, the focus is primarily on stack stability, sufficient aisle widths, and safe use of material handling equipment.

Safety Checklist for Rack and Block Storage

• Rack load capacity per level displayed and observed
• Racks floor- and wall-anchored (where required)
• Aisle widths for material handling equipment and escape routes kept clear
• Maximum stack height in block storage marked and monitored
• Regular visual inspection for damage to racks
• Training of all employees for forklifts and lift trucks
• Personal protective equipment (safety shoes, high-visibility vests) required

Best Practices for Practical Application

Experienced fulfillment operators follow these principles:

1. Keep pick zone lean: Only active items in easily accessible rack storage, rest in reserve (rack or block).
2. Optimize slotting regularly: Fast movers at lower levels and near packing stations, slow movers higher or further away.
3. Hybrid structure instead of dogma: Don't force everything into racks – block storage for reserve is legitimate and economical.
4. Uniform signage: Storage locations, zones, and aisles clearly and consistently marked.
5. Data-driven decisions: Measure turnover frequency, pick times, and floor space costs and adjust layout.

Avoiding Common Mistakes

• Forcing everything into rack storage: Wasting expensive rack space on rarely moved pallets
• Block storage without zone logic: Search and inventory discrepancies increase
• No replenishment process: Pick zone runs empty although reserve is available in block storage
• Rack overload: Safety risk and product damage
• WMS not adapted to warehouse form: Managing block storage with rack logic leads to booking errors

Frequently Asked Questions

Can I operate a small e-commerce warehouse with racks only?

Yes, up to approximately 500–1,000 SKUs and moderate pallet quantities.

Do I need a WMS for block storage?

From medium complexity onward, yes – at minimum for zone booking and replenishment.

What does a shelf rack cost per compartment?

Rough guide: 15–40 euros per compartment, depending on height and load capacity.

When does automation pay off?

Typically from 3,000–5,000 orders per day or a very high SKU count.

Rack storage or block storage for returns?

Inspection zone in rack storage, bulk returns before sorting often in block storage.

Related Topics

• Storage Location and Warehouse Zone
• Pallet Storage Locations
• Racking Systems and Warehouse Layout
• WMS Warehouse Management System
• Warehouse Types and Strategies

Last updated: July 6, 2026