Door Size

Selecting the proper door size is essential when planning the loading dock. Improperly sized doors can create logistic headaches, reduced efficiency, and product damage. Consideration must be given to both the variety of trailers that will visit the dock and the loading method of the product. Planning now for possible future changes can save time, money, and frustration.


The majority of trucks on the road today are at least 8' wide, and an increasing number are 8'6" wide. An 8' door width can service these trucks, but maneuvering room is limited. Another concern of 8' door widths is off-center truck positioning. This can lead to further reductions in efficiency and even create the need for repositioning of the vehicle.

Ideally, nine-foot wide doors should be used to service 8'6" wide trailers. Side-by-side palletizing is simplified and the potential for product damage is significantly reduced. Nine-foot wide doors can also accommodate the unplanned servicing of many oversized loads. For special applications with oversized loads, a 10' wide door can be incorporated.

Wider doors require more building space which can create a problem when room is restricted.

Keep in mind the maximum overall limits for trailer size are 8'-6" wide x 13’-6” high (different in some states). Flat bed carriers are able to exceed the maximum width dimensions (special permits are required).

Door should be spaced on 12’ centers to accommodate the majority of vehicles, the use of dock seals / shelters, and the mounting of two-way communication light systems.


Trailers can range in height from flatbed units (approximately 48" / 1219mm) to closed vans (162" / 4115mm from ground level). The highest internal height for product loading is approximately 114" (2896mm) high.

Depending on the application, there are three basic door heights that are typically specified. Keep in mind that the common dock height is 48" - 52" (1219 - 1321mm).

8' (2438mm) high doors can accommodate many loading/unloading operations, but do not facilitate full floor to ceiling loading of product. The need to optimize the available height in a trailer when loading product in an effort to minimize freight costs, this need makes the 8' high door a less desirable choice.

A 9' (2743mm) high door permits improved floor to ceiling loading of product because a higher load can easily pass under the door opening. Fuller and tighter loading is possible with a reduced risk of product damage due to product impact with the door header. The nine foot height is a popular door height because it suits a wide range of applications. However, trailers with lower heights may create a gap at the top of a 9' door. This gap can be sealed with an appropriately sized dock seal or shelter.

A third typical door height is 10' (3048mm)

The most versatile door size is 10' (120") high. This height will service the full range of loading / unloading operations. 10' high doors will accommodate trailers of all heights up to and including high cube trailers and high cube sea containers.

Special consideration should be given when choosing a dock seal or shelter for a 10' high door. A dock shelter with a 10' high door provides the greatest degree of unobstructed access to the rear of the trailer.

Door sizes can be specified to any configuration required. Keep in mind the product characteristics and possibility of future change.