A 90 kg steel leaf, slamming shut several hundred times a day under a heavy closer, hangs entirely from its frame. When a hospital door starts to bind, drop or pull away from the wall, the leaf is usually blamed — but the root cause is more often a frame that was too light, anchored into the wrong substrate, or set into a wall it was never designed for.

Design conditions first

Frame engineering starts with four inputs: the leaf weight (including lead lining, glazing and hardware), the duty cycle, the wall construction, and any ratings the assembly must carry (fire, acoustic, airtight, radiation). Lead-lined and steel-stiffened medical leaves are far heavier than standard commercial leaves; frame gauge, anchor count and hinge reinforcement all follow from that weight. A frame that is adequate for a 40 kg office door is not adequate for a 120 kg X-ray door.

Frame profiles

Hollow metal frames are bent from a single steel profile into a head and two jambs. The main profile families:

  • Single rabbet — one stop; used for standard single-swing openings. Jamb depths below roughly 4¾″ (120 mm) are typically only available as single rabbet.
  • Double rabbet — two stops, allowing doors swinging in either direction or pairs of doors in the same frame; equal or unequal rabbet depths. Common in hospitals for pairs and for leaf-and-a-half patient-room doors.
  • Cased opening / flush profile — no stop; used for communicating openings and for frames receiving sliding hardware.

The stop itself is structural: it resists the closing impact and, with gaskets, forms the seal line. Double EPDM gasket grooves or applied compression seals are detailed at the stop for hygienic and airtight doorsets. The jamb depth must match the finished wall thickness (stud + both faces of board, or masonry plus plaster) — a mismatch leaves either a gap to be caulked or returns that bear against nothing. Frame face width (commonly 2″ / 50 mm) sets the visible architrave line; wider faces cover more of the wall/frame joint and are forgiving on rough openings.

Steel thickness and reinforcement

Frame gauge follows door duty. Knockdown drywall frames are available in 18, 16 (the industry standard) and 14 gauge; for medical work, 16 gauge (1.5 mm nominal, min 1.3 mm per A250.8 tolerances) is the sensible minimum, with 14 gauge for heavy, lead-lined or high-traffic openings. Hardware reinforcements are welded inside the frame at the factory: hinge reinforcements (typically 7–10 gauge), strike reinforcements, and closer reinforcing sleeves at the head. Frames for automatic operators need reinforcement for the operator arm or track loads — check the operator manufacturer's template, not just the frame catalog.

Knockdown vs welded

ANSI/SDI A250.8 recognizes both. Knockdown (KD) frames ship flat, assemble on site with interlocking corner joints, and suit drywall partitions and export logistics — cheaper freight, easier handling into finished buildings. Welded frames arrive as a rigid unit with corners face-welded and ground smooth; they are stiffer, hold alignment better under heavy leaves, and are preferred for masonry construction, lead-lined doorsets and hermetic frames where corner geometry must be exact. Welded frames ship with a temporary spreader bar and must be installed with a setting spreader to keep the jambs parallel until the wall or anchors lock them in.

Anchoring methods by wall system

  • New masonry / concrete block: masonry wire or T-strap anchors built into the bed joints as the wall goes up, plus adjustable base anchors. Frames are grouted full or spot-grouted at hinges for heavy doors. This is the most robust condition — but the frame must be on site before the wall.
  • Steel stud drywall: snap-in or screw-on steel stud anchors behind the framing, with the jamb depth ordered to the exact partition thickness. KD drywall frames with compression anchors suit retrofit into existing openings (SDI A250.8's "slip-on drywall" type), though these are not available with welded corners.
  • Existing masonry openings: punched-and-dimpled jambs with expansion bolts or tube-and-strap anchors fixed back to the structure; verify substrate strength — hollow block and weak mortar do not hold expansion anchors well.
  • Cleanroom sandwich panels: purpose-designed frames that clamp or screw to the panel skins with sealed returns; standard masonry anchors are useless here, and every penetration must be sealed to maintain the envelope.

Anchor count is not a place to economize: heavy hospital leaves and closers justify anchors at closer spacing and grout filling at least the hinge jamb.

Frame dimensions and rough opening

Order frames to the structural (rough) opening, not the nominal door size. Frame outside dimensions must allow for plumb-and-shim tolerances; the clear opening is what remains after rabbets and stops, and it is the clear opening — not the nominal leaf size — that governs bed access and code compliance (see Chapter 5). Hermetic sliding doors replace the three-sided frame with a pelmet/track assembly plus a sealed perimeter frame; their structural requirement is a lintel or wall capable of carrying the suspended leaf and operator loads.

Common mistakes

  1. Frame gauge chosen from the door schedule's leaf line only, ignoring leaf weight after lead, glass and hardware.
  2. Jamb depth ordered before the wall buildup is finalized.
  3. KD frames specified for heavy or lead-lined doors where a welded frame would hold alignment.
  4. Anchors specified generically ("as manufacturer's standard") without reference to the actual substrate.
  5. Grouting skipped at hinge jambs to save time — the single most common cause of sagging heavy doors.

Practical checklist

  • Confirm leaf weight, rating set and wall buildup; then fix profile, gauge, KD/welded, depth and anchor type in that order.
  • Require a setting spreader and plumb tolerance check at installation, and grout at least the hinge jamb on leaves over ~80 kg.
  • For rated doorsets, verify the frame is part of the same test evidence as the leaf.