Warehouse Design

Let’s learn more about Warehouse Design. Once it has been determined to use a warehouse, the next step is designing it. Whether the warehouse is a small manual operation or a large automated facility, the three principles that are relevant are Design criteria, Handling technology, and Storage plan.

Design Criteria

Warehouse design criteria address physical facility characteristics and product movement. Three factors to be considered in the design process are:

• Number of stories in the facility,
• Height utilization
• Product flow

The Design Process

The design process is a series of steps. In reality, these steps are normally undertaken in an iterative manner, as decisions at a later step may necessitate decisions made at an earlier step being reconsidered. Suggested steps are as

• Define business requirements and design constraints.
• Define and obtain data.
• Formulate a planning base.
• Define the operational principles.
• Evaluate equipment types.
• Prepare internal and external layouts.
• Draw up high-level procedures and information system requirements.
• Evaluate design flexibility.
• Calculate equipment quantities.
• Calculate staffing levels.
• Calculate capital and operating costs.
• Evaluate the design against business requirements and design constraints.
• Finalize the preferred design.

Internal Layout

The warehouse flow diagram is a useful starting point as this shows the relative flows between the different zones. Obviously, the designer will try to minimize the distances for the greatest flows and will avoid any backtracking or major cross-flows. Typically, a number of draft designs will be drawn and these will be compared by the design team. This process will have a number of objectives, such as:

• throughput efficiency, i.e. achieving the required throughput with least resources;
• building utilization, i.e. for new buildings, designing to conform to rectilinear building norms for both high-bay and low-bay areas, while for existing buildings, making best use of the available space;
• safety, eg separating pedestrian from fork-lift truck traffic, avoiding the inclusion of any dangerous junctions between aisles, and ensuring that there is a rapid means of fire escape for all personnel (eg no closed aisles);
• environmental, eg capturing rainwater run-off for further use and location of solar panels.

External Layout

The external layout will show exactly where the warehouse building is to be located on the site and the relevant roadways and parking area. Critical decisions therefore include whether vehicle traffic should go around the building or whether traffic should just go to one or two sides of the building and then return. This will be partly associated with the decision regarding a flow-through or U-flow internal configuration. Even if operational access is only required on one side, then it is still likely that access will need to be considered for emergency services (eg for fire-fighting) on the other sides.

Other external layout considerations include:

• roadway design;
• parking areas, for trucks, containers, demountable bodies and private cars (the latter
• normally being separate from the operational area);
• gatehouses, fences, barriers and landscaping;
• vehicle wash, fuelling and maintenance facilities;
• fire assembly area.

Number of stories in the Facility

The ideal warehouse design is limited to a single story so that product does not have to be moved up and down. The use of elevators to move product from one floor to the next requires time and energy. The elevator is also often a bottleneck in product flow since many material handlers are usually competing for a limited number of elevators. Due to limitation of land space, companies these days resort to multiple level warehousing, by using state of art lifts, hydraulic lifts for the mechanical movement of goods and products. Even car companies who require a large space for storage have multiple floors in the warehouse, with multi-level parking.

Height utilisation

Regardless of facility size, the design should maximize the usage of the available cubic space by allowing for the greatest use of height on each floor. Most warehouses have 20- to 30-foot ceilings, although modern automated and high-rise facilities can effectively use ceiling heights up to 100 feet. Through the use of racking or other hardware, it should be possible to store products up to the building’s ceiling. Maximum effective warehouse height is limited by the safe lifting capabilities of material-handling equipment, such as forklifts.

Product flow

Warehouse design should allow straight product flow through the facility whether items are stored or not. In general, this means that product should be received at one end of the building, stored in the middle, and then shipped from the other end. Straight-line product flow minimizes congestion and confusion.

Handling technology

The second principle focuses on the effectiveness and efficiency of material-handling technology. The elements of this principle concern movement continuity and movement scale economies.

• Movement continuity: Movement continuity means that it is better for a material handler or piece of handling equipment to make a longer move than to have a number of handlers make numerous, individual, short segments of the same move. Exchanging the product between handlers or moving it from one piece of equipment to another wastes time and increases the potential for damage. Thus, as a general rule, fewer longer movements in the warehouse are preferred.
• Movement sale economies: Movement scale economies imply that all warehouse activities should handle or move the largest quantities possible. Instead of moving individual cases, warehouse activities should be designed to move groups of cases such as pallets or containers. While this might increase the complexity of an individual’s activities since multiple products or orders must be considered, the principle reduces the number of activities and the resulting cost.

Storage plan

According to the third principle, a warehouse design should consider product characteristics, particularly those pertaining to volume, weight, and storage. The integrated storage plan must consider and address the specific characteristics of each product.

• Product Volume: High-volume sales or throughput product should be stored in a location that minimizes the distance it is moved, such as near primary aisles and in low storage racks. Such a location minimizes travel distance and the need for extended lifting. Conversely, low-volume product can be assigned locations that are distant from primary aisles or higher up in storage racks.
• Product Weight: Relatively heavy items should be assigned to locations low to the ground to minimize the effort and risk of heavy lifting.
• Product Density: Bulky or low-density products require extensive storage volume, so open floor space or high-level racks can be used for them. On the other hand, smaller items may require storage shelves or drawers.