Sealing Systems

Sealing systems seal off the space between a parked trailer and the building (Figure 70). They help to maintain the internal climate and protect the freight against damage.

Figure 70: Sealing System

Sealing systems have many benefits:

  • Energy savings–reduces overhead costs by maintaining the building’s interior temperature and preventing heating/air conditioning from escaping.
  • Safety and productivity–eliminates dangerous precipitation from the loading areas. Worker productivity correlates to the workplace environment and its safety.
  • Freight protection–protects freight against harmful weather and minimizes entry of vermin.
  • Security–prevents product theft and unauthorized entry.
  • Storage–docked trailers become secure, climate-controlled extensions of the building.

There are two types of sealing systems:

  • Compression foam dock seals–the seals are made of high-density polyurethane foam padding with heavy-duty cover material and wear pleats. They are mounted to the wall at the loading door and compress against the back of the truck.
  • Truck shelters–truck shelters have a rigid frame, a head curtain and side curtains with fiberglass stays. The frame is installed to the building wall and the curtains seal against the wall and the side of the truck (Figure 71).

Figure 71

Both seals and shelters use abrasion-resistant industrial fabrics on their sealing surfaces to resist wear from the trailer movement during loading and unloading.

The building wall construction may determine the most suitable type of sealing system. Dock shelters are recommended when walls are not designed to handle the high compression forces of traditional seals.


Proper selection is the most important aspect of sealing system installation. Improper selection can result in not only a poor installation, but also product damage and decreased productivity. When selecting a sealing system, choose a system that is the most effective at sealing the majority of vehicles being serviced.

Grade of Approach

The grade of approach might be level, declined or inclined.

If necessary, seals can be tapered to ensure parallel compression along the entire face of the side pads, which creates an effective seal.

Overhead Door Dimensions

The size of the door opening determines the most suitable sealing systems.

Dock Bumper Projection

The dock bumper projection is the distance between the wall and the front face of the bumper. On declined driveways, the bumper must project far enough to prevent trucks from impacting the upper wall.

Dock Height

The dock height is the distance between the grade and the top of the dock floor.

Mounting Surface

The wall construction may determine the most suitable type of sealing system. Dock shelters are recommended when walls are not designed to handle the high compression forces of traditional seals.


Compression foam dock seals are more effective for sealing than using a shelter system.

  • Can be used on doors up to 9-feet wide
  • To optimize contact with the truck, seals can be tapered to match the drive approach
  • Not recommended for use with trucks with rear loading platforms (Figure 72)
  • Must be sized appropriately for the best access to the interior of the truck
  • Seals the building to conserve energy
  • Economical–provides a return on investment in energy savings
  • Some states offer energy rebates

Figure 72

Install the seals with an opening between 7’4-inch and 7’8-inch (Figure 73). Use bevel seals for a loading door wider than 7’8-inch (Figure 74).

Figure 73

Figure 74

Maintain a minimum of 3-inches between the bottom edge of the head pad and the top of the truck (Figure 75). Various head pad heights are available. Use a fixed head curtain instead of head pads for tall doorways and a wider range of trailer heights (Figure 76).

Figure 75

Figure 76

Guidelines for compression foam dock seal installation:

  • Per square foot of pad length–approximately 80-pounds of compression force on building
  • Distance from wall to the face of the dock bumper–minimum of 4-inches
  • Pad projection beyond the bumper–minimum of 4-inches, maximum of 8-inches; 6-inches is nominal
  • For recessed driveways with a slope of more than 2%–specify a taper seal; for every 1% of driveway grade, taper the seal 1-inch for overall length (Figure 77)

Figure 77


A truck shelter allows for full access to the interior of the truck. An air gap will still be present around the hinge area of the truck’s door.

Dock shelters can be installed on nearly any door but are usually installed on doors between 9-feet wide x 9-feet high and 12-feet wide x 12-feet high.

Use truck shelters for:

  • Loading doors wider than 9-feet or higher than 10-feet
  • Trucks with extended tailgates
  • Trucks with rear platforms (Figure 72)
  • Full access of truck’s interior

Guidelines for truck shelter installation:

  • Minimum shelter width–11-feet wide (O.D.) measured across the side frames
  • Standard opening width–7-feet wide (I.D.) measured between the insides of the side curtains
  • Position of bottom edge of head curtain–6-inches below height of the lowest expected truck (Figure 78)

Figure 78

  • Top of shelter–minimum of 18-inches above top of highest expected truck. Commonly 15-feet off top of grade
  • Shelter projection in front of dock bumpers–14 to 20-inches
  • Install the support brackets for a rigid shelter on the building foundation, flush with the dock floor; the support brackets should project past the shelter frame by 3 to 6-inches