Loading Dock Design

The loading Dock is a key component of any facility, whether it is a warehouse, grocer, retail outlet, plant, or other material handler. Through a variety of equipment loading docks can speed up traffic and capture costs that add up if left unattended. With careful planning many of the risks and expenditures associated with a design lacking proper safety features can be alleviated. Improving dock function, employee safety, and effective transfer of goods from your facility to its intended destination should be a primary concern of all conscious business owners and purchasers.

Common problems on the loading dock are often rooted in initial design elements which do not take into consideration future dock uses or the evolution of manufacturing and production. Often times docks will have poorly planned approaches, small doorways, excessive slopes, gravel approaches, improper bumper projections, and docks that are too low to accommodate any standard over the road trailers. By planning for the future steps can be taken to safeguard against large remodelling costs later. The initiation of future planning can take many forms, whether that is installing knock out panel walls for future door expansions, or building your dock to standard height and using wheel risers for smaller trucks.

These simple inexpensive concepts can save you and your customer’s time and money further down the road. Due to the diversity and variations that may exist at the loading dock,
any specification, drawings or other material pertaining to the loading dock should be developed and approved by an experienced professional architect and reviewed by an experienced loading dock professional. Follow best practices for compliance to traffic engineering conventions in design to meet state and local codes.

It is important to include in the specifications of any project that the selected manufacture must provide; specifications, approval drawings, installation manual(s), owner’s manual(s) and employee equipment training, to the owner.

SAFETY MATTERS
Despite the loading docks potential to save money it has exponential safety risks which can cost your company in excess of one million dollars from direct and indirect costs. Financial hardships affect your tenants, customers, employees and bottom line, for this reason aggressive dock safety practices are considered good business sense.
Note: It is the employer’s responsibility to ensure proper training and operating practices of their employee’s.

APRON SPACE
The approach leading up to a bay door, known as the Apron Space, is an area necessary for trucks maneuvering into position at the loading dock opening. When planning this extension of your dock recognizing the needs of current and future potential freight is fundamental to the long term viability of the facility. Factors to consider are the direction of traffic flow, total vehicle lengths received, and materials used for the landing and leading up to the dock.

A simple guideline for determining apron space is to take the sum of the longest possible combination of truck and trailer and multiply the total length by two, then adding an additional safety factor of 5’0” to 10’0” on the outcome. (i.e. a truck with an overall length of 70’ requires a minimum apron space of 150’).

Keep in mind that a dock receiving box trucks and trailer jockey trucks today may not be using these in later years. Always consider long term construction in order to avoid costs in later years.

If the apron space is to be surfaced with asphalt, a concrete landing strip must be poured. This is necessary due to asphalts tendency to become malleable under heat, resulting in depressions changing your truck differential to the dock. This is a serious problem which can make a leveler or board ineffective as well as making it difficult to properly secure wheel risers due to uneven ground.

A gravel-covered loading dock apron should be avoided because it creates uneven and unsafe dock conditions. Note: unless the loading dock is designed to handle peak traffic loads, space must be provided for a truck waiting area. This should be situated so as not to impede the movement of trucks positioning for docking and leaving the facility.

TRUCK BAYS
Truck bays are a complicated portal requiring many pieces of equipment in order to operate safely and efficiently. Factors which ensure the safe function of those pieces of equipment is relative to dock door displacements from each other as well as adequate staging space within the facility.

For docks with multiple loading bays door displacement is crucial to effective loading and as a deterrent to bottlenecking from cramped staging areas. Typically the minimum displacement for doors is 12’ on center of the opening. This provides an overall truck width of 10’ including the mirrors. With greater displacements loading is made more economical, safer, and easier.

When determining the number of loading bays needed to support your product flow, consider the number of trucks received per day, delivery schedules, how many pallets can be loaded or unloaded per hour at one opening, and the number of trailers typically staged at your dock.

Bottle necks inside and outside your facility should always be avoided. Bottlenecking within your dock is the result of too little space for staging; this causes blind spots and reduces the mobility of your loaders, increasing safety risks and lowering productivity. Outside your dock on the apron, bottlenecking occurs when trucks are staged for loading without adequate room for safe departure of other trucks leaving the facility. Another form of restriction from bottlenecking occurs when there is not enough room on the sides of the trailer to safely turn out away from other trucks on the apron. By utilizing a 14’ door differential trucks can safely and effectively exit and couple with the loading dock. This also provides additional space between doors for staging.

DOCK APPROACH

Level dock approach
The most effective approach grade for a loading dock is approximately a 1%-2% incline. This puts the top of the trailer further away from the wall, while also channeling water runoff away from the facility and your product. (Note: when raising the nose of the truck to couple with a tractor the grade is changed, the dock bumper projection must be able to accommodate this change in incline)

DOCK TYPES

Cantilever Loading Dock Design
In a cantilever loading dock design, the foundation wall (dock face) projects past outside building wall. This can prevent damage to the building wall, should a dock bumper fail.

Enclosed Loading Dock Design
This design often used by package handlers utilizing fleets of box trucks, allows for control against pilferage while improving efficiency and comfort; it also doubles as space for overhead cranes loading/unloading flat bed trucks. It is the most expensive loading dock design requiring greater initial investment and maintenance. A main concern for this type of dock is the need for ventilation, adequate air-exchange, due to the exhaust fumes of motors operating within.

Flush Loading Dock Design
The most common type of loading dock used today is the flush loading dock. This dock shares the same foundation as the wall. When the building wall projects past the foundation due to the use of metal or other finishing material, dock bumper projection must be considered more closely; i.e. bumpers should always be a minimum of 4.5” from the wall, if the wall projects 1” past the foundation where bumpers are mounted, then the bumper will need to have at least one more 1” of projection.

TRUCK TYPES

Trucks come in a wide variety of heights, overall lengths and bed heights. The above general information about truck can aid in designing the loading dock, it is best to remember that each of the above truck heights can vary as much as 6” to 8” (12” if air-ride trailer suspension) in height from empty to fully loaded, this is know as “float”. When designing the dock it is a good practice to ask the client for a list of trucks serviced at the loading dock; i.e. height, width, overall length, bed height and frequency that they arrive at the loading dock.

If a wide variety of trucks are to be serviced it may be practical to have several dock heights or one (1) dock position dedicated with a dock scissor lift or a truck leveler to accomplish this. If it is a standard captured fleet (all trucks are the same width, length, height and bed height), then one (1) dock height can possibly serve them all.

Type of Truck	Truck Bed Height Total Range
Double Axel Semi	45” – 55”
City Delivery	45” – 48”
Container	55” – 62”
Flatbeds	47” – 62”
Furniture Van	23” – 36”
High Cube Van	35” – 43”
Low Boys	19” – 25”
Panel Truck	19” – 25”
Reefer	50” – 60”
Stake Truck	42” – 48”
Step Van	19” – 30”
Straight Semi	48” – 52”

DOCK HEIGHT

• Optimal dock height plays a critical role in providing smooth product transfer…The following selection criteria must be considered for a proper loading dock height.
• Service range of the variety of trucks to be service and mid-point.
• The maximum grade capability of your client’s material handling equipment, consistent with dock leveler and board length.
• Dock leveler and board length that can accommodate the height difference from dock to truck, and truck/trailer “float” during loading/unloading.

The average loading dock height is between 48” and 52”. Many facilities may have more specific qualifications for their loading docks which can put them above or below this level. When considering your client’s application determine the highest and lowest truck received, in addition find the average truck bed height (note whether the trailers are refrigerated or not). If the differences in dock height are too great to service all traffic consider options such as wheel risers. This allows a dock to receive standard trailers at a 48” dock height and box trucks which would come in below the operating range of many Dock levelers.

Knowing the maximum grade capability of your material handling equipment can help determine the dock height and dock leveler length. The maximum grade capability of a pallet jack is 3%, electric pallet jack 7%, electric lift truck 10% and gasoline fork tucks is 15%. When planning the dock height always try to strive for the least incline/decline approach to load/unload the vehicles that arrive at the dock, this will provide a longer life for the material handling equipment and the dock leveler.

For more information
www.elitematerialhandling.com
Manpreet Sachdev

The author is CEO at Elite Material Handling Co., based in Bangalore.  Elite is one of the foremost companies in the field of materials handling with a reputation spanning over six decades.  The company has a wide range of time-tested products proven in all fields.