A dock seal squeezes against the trailer. A dock shelter wraps around it. Each one suits a different kind of dock. Here is how to choose, using the loading dock industry's own planning guides rather than a sales sheet.
Every loading dock has a gap between the building and the back of the trailer. In the Lower Mainland that gap lets in rain, wind and cold air from October to April, and lets conditioned air out all year. In the dock seal vs dock shelter choice, both close it. They do it in different ways, and picking the wrong one usually means torn fabric, a wet dock floor and a forklift driver who can’t see into the trailer.
How each one works
MHI’s Loading Dock Equipment Manufacturers group (LODEM) defines them in its Dock Seals and Shelters 101 guide:
- Dock seal: foam-filled side pads bonded to a rigid frame and covered in fabric. The trailer backs into the pads and compresses them, sealing directly against the trailer body.
- Dock shelter: an enclosure that sticks out from the building face, with head and side curtains that contact the vehicle body to make the seal. The trailer backs into the shelter, and the curtains drape against its sides and top.
LODEM also covers hybrids, such as a seal with a head curtain, which it calls effective where trailer heights vary widely.
Dock seal vs dock shelter: side by side
| Dock seal | Dock shelter | |
|---|---|---|
| Typical door size (LODEM) | Smaller door openings | Larger door openings |
| Air-flow control (LODEM) | Up to 90% efficiency | Up to 70% efficiency |
| Mixed trailer sizes | Less forgiving | Suited to varying truck configurations |
| Access to the trailer’s rear | Pads compress at the corners | More open. LODEM says a shelter with a 10 ft door gives the most unobstructed access |
| Projection from the wall (LODEM rule) | Bumper projection plus 4 to 6 in | Bumper projection plus about 18 to 20 in |
| Main wear point | Foam compression and fabric wear | Curtain tears and frame damage from misaligned trailers |
One manufacturer’s selection guide adds that compression seals need the building to withstand 35 to 90 lb of pressure per foot, and puts its standard seals at door sizes of about 8 x 8 to 9 x 9 ft. That’s one company’s figure, so confirm for the product you’re quoting.
Dock seal vs dock shelter: start with your trailers
LODEM’s advice is to size for the common 80% of your fleet, not the odd one. A few questions sort most docks:
- Are trailer heights and widths consistent? One carrier with one trailer type points to a seal. Mixed carriers, containers and straight trucks point to a shelter or a seal with a head curtain.
- How big is the door? LODEM’s Dock Planning 101 recommends 9 ft wide doors for 8 ft 6 in trailers and 10 ft high doors to take everything up to high-cube trailers and sea containers. On those larger openings, shelters become the usual choice.
- Is it a refrigerated or temperature-controlled dock? The tighter seal from a compression seal matters more. Dock Planning 101 also suggests a vestibule at refrigerated facilities.
- Do forklifts need full access to the rear of the trailer? Seal pads can block the outer pallet positions. Shelters leave the opening clearer.
Getting the details right
Projection
Too little projection and the trailer crushes the seal or hits the building. Too much and it doesn’t seal. LODEM’s rule is to start from the bumper projection and add 4 to 6 inches for a seal, or about 18 to 20 inches for a shelter. Worn or missing bumpers throw this off. Bumpers are cheap compared with a crushed seal frame or a cracked wall.
Sloped approaches
On a sloped driveway the trailer meets the wall at an angle. LODEM says to taper the units 1 inch for every 1% of grade when the incline or decline is 2% or more. An untapered seal on a sloped approach seals at the bottom and gaps at the top, or the reverse.
Rain and wind on the coast
Nothing here comes from a standard. It’s what we see on Lower Mainland docks. Shelter head curtains take wind and rain hard, and a torn or short head curtain lets water run straight onto the dock leveler and floor. Seals on docks with heavy truck traffic flatten over time and stop sealing at the top corners first. Check both before the rainy season. The commercial door weather sealing guide covers the overhead door side of the same problem.
Signs it’s time to repair or replace
- Daylight visible around the trailer once it’s docked.
- Foam pads that stay flat and don’t spring back.
- Torn curtains, missing stiffeners or a bent shelter frame.
- Water pooling at the dock door threshold after rain.
- Pest activity at the dock. See our page on loading dock pest control.
The seal or shelter, the leveler, the bumpers and the overhead door all work as one dock position. If one is wrong, the others wear faster. We service the whole position: see our dock equipment repair page and loading dock door repair. For cold-storage docks, see our cold storage door page.
Questions property managers ask us
Which seals better, a dock seal or a dock shelter?
A dock seal. MHI’s loading dock equipment group says a dock seal can achieve up to 90% efficiency in controlling air flow at the dock, compared with up to 70% for a dock shelter.
When should I choose a dock shelter instead of a seal?
When the door opening is large or the trailers you receive vary in size. A shelter also gives forklifts more open access to the rear of the trailer.
How far should a dock seal stick out from the wall?
MHI’s guide says to take the bumper projection and add 4 to 6 inches for dock seals, or about 18 to 20 inches for dock shelters.
Does a sloped driveway change the seal?
Yes. MHI’s guide says to taper the units 1 inch for every 1% of grade when the incline or decline is 2% or more.
What door size suits standard trailers?
MHI’s Dock Planning 101 recommends 9 ft wide doors for 8 ft 6 in wide trailers and 10 ft high doors to accommodate trailers up to high-cube trailers and sea containers.
Book a look at your doors
Call (604) 206-5727 or use the contact page. We answer around the clock for commercial door failures. New commercial clients: 10% off labour on your first service call or repair. Mention NEW10 when booking (one per business, not combinable with maintenance-contract pricing, work booked by Dec 31, 2026).
