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DL Series Steel Stiffened Door

DL-SS Series stiffened core doors add internal steel stiffeners, extending the full width and height of the door with allowance for reinforcements. Standard DL Series is specified to Levels 2-3 extra heavy-duty 16 gauge (18/16 gauge available) and 3/16" hinge thread engagement; optional heavier duty DE Series Levels 2-4 to max-duty 14 gauge (18/16/14 gauge available). Premium full flush standard door construction combines pan-style panels with optional lock-side bevel, and full height center seam projection welded edges.

DL/DE - SS Series doors have a higher than normal resistance to impact.



Strength, durability and ease of installation

  • Steel stiffened core construction using 20 gauge stiffeners (18/16 gauge options) located 6" apart and welded 5" max OC the height of each stiffener, filled with 1 pound fiberglass batting (polystyrene option) between stiffeners
  • The standard stiffened core with fiberglass batting achieves sound and thermal ratings of STC 35 / U=0.61 / R=1.65 per ASTM 1363
  • Square edge design allows for non-handed inventory control in local distribution. Optional lock edge bevel 1/8" over 2" (~3˚)
  • Hinge and lock edges are reinforced with continuous 16 gauge steel channel the full height of the door, welded at a max 5" OC (optional 10 gauge hinge and 14 gauge lock channel with DE Series)
    • Universal standard/heavy weight hinges are used with hinge fillers to allow for easy modification from heavy to standard weight hinge preps
    • Standard visible edges may be filled seamless, intermittently stitch welded and filled, or continuously welded and filled
  • Top flush and bottom inverted channels provide excellent door stability with 16 gauge steel channels, projection welded at a max 2-1/2" OC
  • Standard 14 gauge inverted top and bottom channels provide excellent door stability, and is able to be dressed with top and bottom caps 16 gauge mortise or cylindrical lock reinforcements are of an integral type in accordance with ANSI A115 standards
  • 16 gauge mortise or cylindrical lock reinforcements are of an integral type in accordance with ANSI A115 standards
  • Various light and louver sizes are available with light kits standard (no glass unless noted)
  • Standard cold rolled steel or A60 galvanealed option in 16, 14, and 18 gauge skins. G90 available in 16 or 14 gauge

Exceeds industry standards

  • Republic is SDI Certified through regular audits to ensure manufacturing, performance and quality standards set by the Steel Door Institute
  • Overall door construction exceeds ANSI A250.8-2017 (SDI-100), the standard set by SDI specifying sizes, design, materials, construction, finishing and performance for standard commercial steel doors and frames
  • Hardware preparations and reinforcements meet ANSI A250.6-2003, and locations meet ANSI/DHI A115, unless otherwise stated
  • Doors meet the broadest fire rating requirements; they are listed for installations requiring compliance to both neutral pressure testing (ASTM E152 and UL-10B) and positive pressure standards (UL-10C)
  • Factory-applied baked-on rust inhibiting primer meets ANSI A250.10-2011

Typical applications

Environments that require additional resistance to localized impacts and vandalism, such as detention centers and behavioral correction facilities. While our normal honeycomb core provides the best structural integrity in testing, especially considering the weight of the door, a larger localized impact to the door face can be resisted better with a steel stiffened core.

Technical Data Guide

For more information, download the Republic Technical Data Manual.

  • DL/DE-SS Series (Pages 33-35), thermal & sound (p 26), fire rated (p 98-99), miscellaneous TOC (p 107), door options (p 108-116), paint (p 117-118), vision kits (p 119), louvers (p 120), standard hardware locations (p 121-130), specification 08110 (p 33, 131-135)