Two doors can share the same nominal size, the same 1.5 mm steel face and the same catalog photograph, yet one delaminates within three years of hospital corridor service while the other runs for twenty. The difference is inside the leaf and in the details nobody photographs: the core, the edge seams, the hardware reinforcements and the seals.

The leaf: face sheets and edges

A hollow metal medical door consists of two steel face sheets formed and joined around a core. Face sheet thickness is the first durability decision. ANSI/SDI A250.8 defines four performance levels with minimum thicknesses: Level 1 standard duty at 0.8 mm (20 gauge), Level 2 heavy duty at 1.0 mm (18 gauge), Level 3 extra heavy duty at 1.3 mm (16 gauge) and Level 4 maximum duty at 1.7 mm (14 gauge). Given daily bed and trolley impact, hospitals should treat Level 3 (1.3–1.5 mm) as the baseline for patient areas, with Level 4 for high-abuse corridors and emergency departments.

Steel type matters as much as thickness. The Steel Door Institute recommends galvannealed steel (zinc-iron alloy coating, typically A40 or A60) rather than spangled G-type galvanized, because the galvannealed surface accepts primer and powder coating far better — a decisive factor where doors are repainted or recoated during refurbishments. Stainless steel (usually 304 or 316, #4 brushed finish) is used where corrosion resistance and cleanability outweigh cost, such as wet areas and sterile suites; note that mirror finishes show fingerprints and scratch visibly.

Edge construction distinguishes quality grades. Options per SDI A250.8 and HMMA guide specifications include:

  • Continuously welded vertical seams, dressed smooth — no visible seam, best cleanability, the appropriate choice for hygienic and cleanroom doors.
  • Intermittently welded (spot/tack at max 152 mm spacing) with seam filled — acceptable for standard corridors, lower cost.
  • Interlocking lock-seam — economical but leaves a visible seam at both edges; avoid in hygienic zones.

Single-acting door edges are normally beveled (1/8″ in 2″, about 3 mm in 50 mm) to clear the frame stop; double-acting doors get rounded edges. Top and bottom edges are closed with inverted steel channels of at least 1.0–1.3 mm welded to both face sheets — the bottom channel is a common moisture entry point, so fully welded closures pay off in wet-cleaned areas.

Core infill: the hidden trade-off

Core Strengths Weaknesses Typical medical use
Kraft honeycomb Rigid, light, economical Minimal insulation, moderate sound control Interior ward/office doors
Polystyrene Good thermal insulation Minimal sound reduction Exterior, energy-controlled openings
Polyurethane Highest insulation, foamed-in-place bond Minimal sound reduction, higher cost Exterior, cold-chain adjacent rooms
Mineral board Temperature-rise fire performance Heavy, brittle Stairwells, fire barriers with TRR requirement
Steel stiffened (welded channels, max ~152 mm spacing, voids filled with fiberglass/rock wool) Maximum impact and abuse resistance, good sound resistance Heaviest, most expensive Corridors, ED, lead-lined doors

The trade-offs are real: polyurethane insulates best but transmits sound; steel stiffening survives carts and beds but roughly doubles leaf weight, which cascades into heavier hinges, closers and frame anchors. Lead-lined X-ray doors add a continuous lead sheet (commonly 1/16″–1/4″) laminated inside, usually over a steel-stiffened core, with lead-lined frames whose attenuation must equal or exceed the wall's.

Reinforcement and hardware preps

Every hardware item needs a factory-welded reinforcement sized before manufacture: hinge reinforcements (often 7–10 gauge steel channels), closer reinforcement boxes at the top rail, mortise or cylindrical lock preps, and flush-bolt preps on double doors. Field-cutting a hollow metal door for hardware after delivery destroys the internal reinforcement and voids fire labels — a classic and expensive mistake. Automatic operators, drop seals and hermetic tracks must all appear on the hardware schedule before fabrication.

Seals, glazing and accessories

  • Seals: perimeter compression gaskets for hygienic/airtight doors; drop-down bottom seals instead of thresholds where trolleys pass; intumescent and smoke seals on fire doorsets.
  • Vision panels: flush-glazed both faces in hygienic areas, fire-rated or leaded glass to match the doorset rating. Beaded, projecting frames trap dirt and are excluded from cleanroom designs.
  • Accessories: kick and stretcher plates, crash rails, push plates, protection strips on leading edges — all preferably through-fixed into reinforcement, not self-tapped into face sheets.

How construction varies across types

Hermetic sliding leaves add four-sided gasket channels and a reinforced top edge for the hanger/operator interface. Fire doorsets require tested constructions (mineral or proprietary cores) — you cannot substitute a core and keep the label. Lead-lined doors need lead continuity at vision panels and lock preps. Acoustic doorsets combine mass (heavy skins, dense cores) with compression seals; a lightweight honeycomb door cannot be "upgraded" to acoustic duty with seals alone.

Practical recommendation

Write the construction schedule as a matrix per opening: SDI level / face thickness, steel type and coating, edge seam type, core, reinforcements, seal set and accessories — then cross-check every hardware item against a factory prep. If a supplier proposes a substitution (core, gauge, seam), ask which test evidence or listing it invalidates before approving.