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Design Pressure

Design Pressure (DP) is a numerical value rating which defines the structural wind loading requirements for a building, and components or cladding of a building, described in pounds per square foot. Essentially Design Pressure represents the wind load the door system can withstand.

Factors that are used in determining the Design Pressure (DP) rating are:

  • Basic wind speed velocity in miles per hour
  • Building height
  • Occupancy type
  • Exposure category based on geographic location
  • Whether the building is enclosed or open
  • Building shape
  • Gust factors

Rated DP Unit Testing

During testing, a door unit is attached to a wooden frame and clamped to a specially designed wall. Air pressure is gradually reduced on the inside of the unit, which increases the pressure on the outside until the door fails (breaks beyond repair). The test pressure must reach 1.5 times the design pressure for 10 seconds without the unit suffering permanent damage. In other words, a unit with a DP of 30 would have to withstand 45 psf. The instant the unit fails, the psf is recorded and is used for the calculation.


Requirements for a DP Rated Unit

The requirements for a DP Rated Unit is dependent on the type of unit being constructed. The unit construction must match the conditions in which the unit was tested. Reeb is able to DP certify 4 different type of units:

  • Therma-Tru Continuous Door System
  • Therma-Tru Continuous Door System with Venting Sidelites
  • Simpson Approved Dowel Pin Door Slab with Therma-Tru Continuous Frame System
  • Simpson Approved Mortise and Tenon Door Slab with Therma-Tru Continuous Frame System.

Most doors will require screws in the top and bottom rails of the unit.


Any units with a mullpost will require a screw above and below the strikes on the mullpost. Double Doors require the use of a Coastal Astragal.


Installation of a DP Rated Unit

The installation of a DP Rated Unit will follow Therma-Tru’s standard installation process.


DP Ratings by Reeb

Reeb is able to certify and label units that have a DP rating of DP47 or DP50. The only difference between the two is the threshold that the unit tested was able to achieve. Currently, Reeb is only able to rate a 6/8 or 8/0 unit. The configuration of the door and the door style are used to determine which rating the unit can receive, or if it is not able to be rated.



Updated on May 15, 2021

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