What size is a standard loading dock door?

Here are the common sizes, what each one is good for, and what changes when you pick a different size.

Common loading dock door sizes

Dock door makers and dock equipment makers give the same small set of sizes. Widths run from about 7 feet 6 inches to 10 feet, and heights from 8 to 10 feet. Here is what each common size is good for.

Door size (wide x high)	Where it fits
8 x 8 feet	Older docks and small box trucks. Loading to the ceiling of a van trailer is hard.
8 x 9 feet	The size seen most often. Works for many trailers, but leaves little room on each side of a pallet.
9 x 9 feet	Better side room for 8 foot 6 inch trailers, so two pallets can sit side by side with less damage.
9 x 10 feet	The most versatile choice for a new dock. Clears every trailer height up to high cube trailers and sea containers.
10 feet wide or more	Oversized loads and special equipment. Takes more wall space per bay.

Why width matters

The legal trailer limit in most states is 8 feet 6 inches wide and 13 feet 6 inches high, and more trailers now use the full 8 foot 6 inch width. An 8 foot wide door can serve them, but a forklift has very little room to work, and pallets loaded side by side rub the jambs. A 9 foot wide door gives the forklift room and cuts down on damage to the door, the jambs and the product. The trade off is wall space: wider doors take more of the building's length, which matters when the dock wall is short.

Why height matters

Trailers range from flatbeds about 4 feet off the ground to closed vans about 13 feet 6 inches tall, and the tallest point a load can reach inside a van is about 9 feet 6 inches. An 8 foot high door handles a lot of everyday loading but blocks floor to ceiling loads. A 9 foot door lets taller loads pass. A 10 foot door covers the full range. When a short trailer backs up to a tall door, the gap at the top is closed with a dock seal or shelter rather than a smaller door.

Dock height and the leveler

The door is only half of the opening. The dock floor is most often 48 to 52 inches above the pavement, and trailer beds sit a few inches higher or lower depending on the trailer and its load. A dock leveler bridges that difference so a forklift can drive straight into the trailer. If you change door size, check the leveler width and the seal or shelter too, since all three are sized to the same opening.

Dock doors and grade level doors

A loading dock is the raised platform, or the opening in a building wall, where trucks back up to load and unload at bed height. Each opening is called a bay, so a "bay door" is usually the same thing as a dock door, and the sizes in the table above apply. A dock door sits at truck bed height. A grade level door, sometimes called a drive in door, sits at ground level so a forklift, a delivery van or a pickup can drive straight inside. Grade level doors are usually larger, often 12 feet wide or more, and they use a regular sectional or rolling steel door with no leveler. Many warehouses have both: dock doors for semi trailers and one grade level door for everything else.

Replacing a dock door with a different size

Going from an 8 foot to a 9 foot wide door means cutting the wall, moving the jambs and bumpers, and often changing the leveler and the seal. That is a construction project and usually needs a permit. Going taller is simpler if the building has headroom above the opening. If the door size is right and the door itself is worn, dented or slow, repair or a replacement door in the same opening is the faster fix.

How G Brothers helps

G Brothers services rolling steel, sectional, high-cycle and fire-rated doors on warehouses, storefronts and loading docks across the Denver metro, and repairs dock levelers, dock seals and dock bumpers. We work on every brand, can provide a certificate of insurance, usually within 24 hours, and dispatch 24/7 for emergencies. See our loading dock door repair and dock leveler repair pages, or ask for a free estimate.

Sources

• Blue Giant, Planning and Design: Door Size
• Blue Giant, Planning and Design: Dock Height
• Rite-Hite, How Customizable Are Dock Doors?