Steel Stiffened / Polystyrene Core Doors

Lindstrom Corporation fabricates Vertically Steel Stiffened and Polystyrene Core Doors, 1-3/4' thick as specified.

Doors will be fabricated of:

  • 16- or 14-gauge face sheets of commercial grade Cold Rolled steel
  • 16- or 14-gauge face sheets of commercial grade A60 Galvanized
  • Doors will have continuous vertical steel stiffeners of 20-gauge and will be spaced no further than 8” on center.
  • Doors will be filled with mineral rock wool. Polystyrene core optional.
  • Top and bottom of doors will be reinforced with continuous 16-gauge steel channels, spot welded to both sides of doors.
  • Hinge reinforcements will be 7-gauge steel angle, 12" long.
  • Cylindrical lock reinforcement will be 16-gauge with 11-gauge thread depth. Other lock and closer reinforcements will be 12-gauge.
  • Doors will be reinforced for all surface type hardware. Drilling and tapping of surface hardware to be done in the field by the installer.
  • Edges of door will be seam welded and ground to ensure smooth finish.


  • Doors will be thoroughly cleaned after assembly and given a prime coat of rust-inhibiting paint.
  • The primer will be air dried.
  • Low gloss oil based trim paints (max gloss 25) are recommended as a finish paint.
  • Undercut: 3/4” standard.


  • Undercuts: 3/4" standard.
  • Other undercuts as specified.
  • Hinge Backset: 1/4” standard.
  • 3/16" or 1/8" available.
  • Astragals: Flat 14-gauge astragals are provided with pairs of doors as needed and are shipped loose for field mounting.
  • Size Limitations: Largest single door available:
    16-: 4'-0" x 10'-0"
    14-: 4'-0" X 10'-0"
Steel Stiffened Doors