Bays and Column Spacing

As part of my final project for the Global Logistics Specialist program at California State Long Beach (GLS Website), my team and I determined the cubic capacity and utilization for an entire network of fictitious warehouses run by a fictitious retailer. We found that the bay and column spacing within a warehouse can have a significant impact on key performance indicators (KPIs) for warehouse occupiers in ways that are not always obvious. In this post I discuss bays and column spacing in a warehouse and why they are important for supply chain real estate participants to consider when a) designing a new warehouse location and/or b) perhaps re-designing an existing warehouse.

The definition of bays and column spacing are similar but not always identical. I define bay areas as the floor areas in the warehouse not occupied by columns, walls or other permanent impediments. The length and width dimensions attributed to bay areas and column spacing are typically the same, with some notable exceptions. Bay areas can have different names in different areas of the warehouse. For example, a speed bay is an area adjacent to the loading areas ideally measuring at least 60′ from the dock to the first column. Used to move goods in a quick and efficient manner, any storage done within a speed bay is usually short-term.

Typical column spacing is the most common storage area between the columns, usually measured by the distance between the columns lengthwise and by depth away from the loading areas in a one sided or flow-through building. For example, if you were peering through the middle loading door of a building with 52′ x 50′ typical column spacing, 52′ would be the width between each column and 50′ would be the depth to the next column away from you. Atypical bays would include any areas along the non-loading walls.

So why are bays and column spacing important to supply chain practitioners? One reason is that they impact a warehouse’s space utilization. Improper column spacing can lead to wasting significant square footage areas and storage capacities due to less overall storage positions. Depending on a number of factors such as pallet size, minimum aisle width, and material handling equipment, a 52′ column spacing and a 56′ column spacing will likely result in very different levels of square footage utilization and storage capacities.  Warehouse occupiers should calculate their optimal column spacing within a warehouse prior to occupancy in a new facility or as part of an audit to determine how well they are utilizing their storage capacity in an existing warehouse. According to Tompkins International, a formula for calculating optimal column spacing is:

[(Depth of Rack * 2) + Flue + Aisle Width] / # of Sections of Rack between Columns

The “Flue” is the space between the row of back to back racking, which is called the longitudinal flue.

Column spacing is also important because it influences the choice of material handling equipment. In order to utilize the available square foot and cubic capacities in a warehouse, certain material handling equipment are required. For example, according to Tompkins a 54′ column spacing allows for a 10′ aisle with typical 48″ racking. Since most counterbalanced forklifts will require a 12-15′ aisle, 54′ column spacing would require narrow aisle material handling equipment in order to maximize the usable square feet and cubic capacity. Therefore, racking decisions may require weighing the potential increased material handling costs with the cost of square foot and storage capacity.

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A survey of new warehouses in Southern California show a variety of column spacing dimensions being used, mostly depending on the clear height being offered. For potential e-commerce fulfillment centers, required column spacing is a minimum of 56′-60′ to allow for the large order picking equipment common in the industry and required minimum clearance is 36’+ to allow for multi-level mezzanines/equipment. Two new developments at the Brickyard in Compton and Pacific Industrial/Clarion’s Imperial Distribution Center in Brea have 36′ clearance heights with 56′ x 50′ typical bays.

For new buildings in Southern California with 32′ clear, the typical bay is 52′ wide with varying depths. Western Realco’s new buildings at 4150 N. Palm Street in Fullerton and 3300 E. Birch Street in Brea have 52′ x 60′ typical column spacing. At Pacific Point East @ Douglas Park in Long Beach, Sares Regis has 52′ x 50′ typical column spacing as does Duke’s new warehouse in Lynwood.

racking-plan-building-b
source: The Brickyard South Bay website

Supply chain participants should be aware of how bay areas and column spacing in their warehouses impact their KPIs. If you need help evaluating new or existing warehouses in your supply chain, including evaluating existing column spacing, please feel free to reach out to me.


References

“SPEED BAY.” SPEED BAY. BOMA International, 2016. Web. 01 Dec. 2016.

Holste, Cliff. “Distribution Center Design: Designing from the Inside Out.” Distribution Center Design: Designing from the Inside Out. Supply Chain Digest, 11 Mar. 2008. Web. 01 Dec. 2016.

Johnson, Wendy. “The Importance of Optimal Column Spacing.” Tompkins International. Tompkins International, 30 July 2015. Web. 01 Dec. 2016.

“How to Optimize Your Existing Warehouse Space | Washington and California,.” Raymond Handling. Raymond Handling Concepts Corporation, 13 Aug. 2014. Web. 01 Dec. 2016.

Fallsway Equipment Company. “Warehouse Operation | Finding Your Aisle Dimensions.” Fallsway Equipment Company. Fallsway Equipment Company, 12 June 2014. Web. 01 Dec. 2016.

Foster, Margarita. “The View From E.CON: E-commerce Real Estate Evolves | NAIOP.” The View From E.CON: E-commerce Real Estate Evolves | NAIOP. NAIOP, 2015. Web. 01 Dec. 2016.

Calculating Dock Position Requirements

One of the most important facility requirements for any logistics operation is the amount of dock high positions an industrial building provides. Often overlooked, dock high positions can have a significant impact on whether an operation is able to meet its key performance indicator objectives and contribute to the overall success of a company.

Determining the minimum number of dock positions needed for a facility involves an understanding of the internal and external factors which affect the amount of dock high positions required. The internal factors can include the amount of trucks serviced by the docks over a period of time (average and peak), the time to load and unload each trailer per dock, staging and cross-docking requirements, work hours over a period of time, employee breaks, drop trailer requirements, trash / bailing requirements, shifts, and shipping preferences. External factors can include time of truck arrivals and departures, the reliability of carriers, whether carriers will back haul drop trailers, types of trailers used by carriers, and truck driver capabilities. A comprehensive understanding of these and any other internal and external factors will result in more precise understandings of an operation’s dock high requirements.

In general, the minimum number of dock high positions are calculated based upon a formula involving their use, the amount of time they can be used, and a safety factor. Below are three examples of manual calculations using some of the internal and external factors above.

  1. Number of Truck Positions Needed = ((Number of Trucks per Year x Hours it takes to Load / Unload a Truck) / Work Hours per Year) x Safety Factor [1]
    1. Inputs
      1. 7,000 trucks per year
      2. 2.5 hours for loading / unloading
      3. 2080 work hours per year
      4. Safety factor of 25%
    2. Calculation
      1. (7,000 trucks per year x 2.5 hours for loading / unloading) / 2080 work hours per year) = 8.4 x 1.25 safety factor = 10.5 docks or 11 dock high positions needed at a minimum
  2. Number of Truck Positions Needed = Number of Trucks per Hour x Turnaround Time per Hour [2]
    1. Inputs
      1. 20 trucks per day
      2. 8 hour work day
      3. 150 minute turnaround time
    2. Calculation
      1. (20 trucks per day / 8 hour work day) = 2.5 trucks per hour x (150 minute turnaround time / 60 minutes per hour = 2.5 turnaround time) = 6.25 dock positions needed or 7 positions needed
      2. If all trucks arrive in AM, then work day would be shortened to 4 hours and the dock requirements would be 12.5 or 13 positions needed
  3. ((Peak trucks per day) x (Average dock time per truck) x (Safety factor of 1.5 to 2)) / Number of hours in work day [3]
    1. Inputs
      1. 20 trucks per day
      2. 2.5 hours per truck
      3. 8 hour work day
    2. Calculation
      1. ((20 trucks per day) x (2.5 hours per truck) x (1.5 safety factor)) / 8 hour work day = 9.375 docks required or 10 docks needed

These three calculations show that depending on the formula used, roughly the same inputs will yield slightly to drastically different minimum dock requirements. Where formulas 1 and 3 resulted in 11 and 10 positions required, formula 2 resulted in only 7. Not surprisingly, formula 2 did not employ a safety factor. Safety factors are used to account for unforeseen variability such as disruptions in deliveries or labor.

Companies may also employ manual simulations of dock requirements.  These simulations include the detailed logging of docks used by the various types of vehicles that deliver or ship to a facility.  These simulations can show how to improve dock assignments or delivery schedules for better dock utilization and determining of minimum docks required.[4]

The use of technology in determining the minimum number of dock positions required may make the use of the manual calculations above obsolete. Warehouse management systems or WMS may include dock requirements based upon much more detailed inputs and trends.  However, the manual calculations formulas above help to show the importance of understanding the external and internal factors involved with determining the minimum number of dock positions for a given operation.

 

Real Estate

Chinese car maker BAIC has disclosed plans to build an assembly plant in Mexico after opening a dealership in Mexico last month. Among Chinese car makers in general, there is growing interest in Mexico as a potentially strong export market. Last year Chinese car makers exported over 330,000 vehicles to Mexico.

Amazon has announced that it will build its 10th fulfillment center in California, agreeing to locate an 855,000 square foot facility near Sacramento International Airport.  The fulfillment center will bring a reported 1,000 warehouse jobs to the area.

PortFresh Logistics is constructing a 100,000 square foot cold storage facility at the Port of Savannah. The facility, which will primarily serve the importers of South American produce, will create 40 jobs upon its opening with an expectation of 75 full-time jobs by 2021.

Newegg, a web-only retailer of technology products, has opened what it calls a Hybrid Centre in Ontario, Canada. The 81,000 square foot facility will include a showroom where customers can view some of its latest offerings.  Newegg also has a Hybrid Centre next to its Los Angeles headquarters.

UPS has applied for Miami-Dade County incentives to build a $65 million sorting facility in the northwest part of the County. In the deal UPS would reportedly receive $877,180 in county funds in exchange for creating 25 jobs and retaining 2,005 existing jobs.

Wal-Mart opened its new $100 million grocery distribution center in Mebane, North Carolina.  The center will employ more than 550 and distribute food to more than 55 Wal-Mart stores in North Carolina and Virginia.

Prologis, the global leader in logistics real estate, reported record second quarter 2016 results.  Rents on lease renewals jumped 17.8%  while rents overal rose 7.9 percent.  These led to second quarter net earnings per share of $0.52 compared to $0.27 in the second quarter of 2017.

Many of China’s logistics property companies have disclosed plans to go public amidst the e-commerce boom there.  Groups such as China Logistics Property and GLP have already gone public and otheres, such as e-Shang Warehouse Services, plan to list soon.

Gap said they will add more than 100 jobs and invest $3.1 million in uprades and technology to increase its e-commerce capabilities in its Gallatin, Tennessee facility.

Retailers are adding more distribution centers closer to major population centers in an effort to provide more efficient customer service.  Customers increasing demand to receive orders faster and cheaper has pushed many of the so-called inland ports to grow much faster than average US industrial markets.

General Mills announced the layoff of 1400 jobs, including 550 in United States as part of a rework of its supply chain.  General Mills plans on selling a plant in southern New Jersey and sell another in northern Ohio.

 

 

 

[1] Mulcahy, David E. Warehouse Distribution and Operations Handbook. New York: McGraw-Hill, 1994. 4.18-.20. Print.
[2] 4Front Engineered Solutions, Inc. “Dock Planning Standards.” (n.d.): 10. Web. 31 July 2016.
[3] Gross & Associates. “Calculating Dock Door Requirements.” (n.d.): n. pag. Web. 31 July 2016.
[4] Mulcahy, David E. Warehouse Distribution and Operations Handbook. New York: McGraw-Hill, 1994. 4.18-.20. Print.