A hospital in the Middle East ordered 400 doors to "1200 × 2100 mm" — the structural opening from the architect's schedule. The factory produced 1200 mm leaves; after frames, stops and clearances were installed, the clear opening was barely 1080 mm and standard patient beds with drip stands would not pass without turning. The entire order was remade. Dimensional errors are the cheapest mistakes to make and the most expensive to fix, because they are only discovered at installation.

Design conditions: start from what must pass

Leaf dimensions are derived, never chosen directly. The derivation chain is: largest item to pass (bed plus attendant, imaging equipment, sterilizer) → required clear opening → leaf width after adding clearances and stop deductions → structural opening after adding frame profile dimensions. Working in the opposite direction — nominal size first — is how the scenario above happens.

Guidance from health facility standards: patient-area doors need clear openings that admit beds with attendants — commonly 1200 mm clear, achieved either with a wide single leaf or an unequal pair (e.g. 1200 + 300 mm leaves, per Australian health building guidance). NHS Health Building Note 00-04 cites 1100 mm clear width and 2000 mm clear height for patient trolley routes. Corridor-to-corridor doors follow the local building code and bed movement strategy. Equipment access is routinely forgotten: MRIs, CT scanners, sterilizers and generators are delivered once but are wider than any bed — check the equipment schedule before fixing structural openings on plant and imaging routes.

Leaf width, height, thickness, weight

Width. Common single-leaf widths run 800–1250 mm; beyond about 1250 mm a single hinged leaf becomes heavy, wide-swinging and hard to closers to control — split into pairs instead. Sliding leaves can run wider since they carry no swing load, limited by wall space for the open position (the clear wall beside the opening must exceed the leaf width).

Height. 2100 mm is the common baseline; 2400 mm and higher suit high-ceilinged corridors and equipment routes. Tall leaves raise deflection and twist risks (see tolerances below) and may need four hinges and heavier stiffening.

Thickness. The international steel-door standard is 1¾″ (≈45 mm); 1⅜″ (35 mm) exists at light duty levels but is rare in medical work. Thicker leaves — 50–60 mm and above — appear on lead-lined, acoustic and hermetic doorsets. Thickness must match the frame rabbet and the hardware: lock backsets, hinge knuckle clearance and closer arm geometry all assume a leaf thickness.

Weight. Weight is an output, not a spec: leaf area × (face sheets + core + lead + glass) plus hardware. A 1000 × 2100 mm 16-gauge honeycomb leaf is roughly 45–60 kg; the same leaf steel-stiffened and lead-lined can exceed 150 kg. Every downstream component — hinges, closer size, frame gauge, anchors, operator force — is sized from this number, so compute it early and state it on the door schedule.

Clear opening, structural opening and clearances

The relationships to control:

  • Structural (rough) opening = frame outside dimensions plus installation/shim allowance.
  • Frame reveal opening minus stop depths = clear opening with the leaf open at 90° — but door hardware (closer arms, pull handles, hinges) may project into it; measure clear opening with hardware fitted.
  • Perimeter clearances between leaf and frame: typically about 3 mm at head and jambs (the 1/8″ convention in US hollow-metal practice and NFPA 80 for fire doors), with undercuts sized for flooring, drop seals and air-transfer requirements. Fire, smoke and airtight ratings all cap these gaps — an over-gap doorset fails inspection even if every component is correct.

Dimensional tolerances

Manufacturing tolerances for standard steel doors are governed by SDI-117: linear dimensions are generally ±1/16″ (1.6 mm) unless otherwise marked, with defined limits for bow, twist and squareness (diagonal difference). Two practical consequences:

  1. Airtight and hermetic performance depends on leaf flatness; a leaf at the twist limit will not compress gaskets evenly. For cleanroom doors, specify flatness tighter than SDI-117 defaults and verify gasket compression on site.
  2. Tolerances accumulate. Structural opening tolerance + frame squareness + leaf squareness + clearance can consume 10–15 mm. Design the dimension chain so worst-case stack-up still yields the required clear opening — do not dimension to best case.

Custom sizing

Custom widths and heights are routine for steel doors (that is the nature of hollow metal fabrication), but custom does not mean unconstrained: face sheet widths are limited by coil stock, fire listings cap maximum tested sizes (e.g. single openings to 4′0″ × 8′0″ and pairs to 8′0″ × 8′0″ in typical hollow metal labeling guides), and oversized leaves exceed closer and hinge ratings. Exceeding a tested size does not make the door non-compliant automatically — but it moves the assembly outside its certification, which the authority having jurisdiction must accept. Lead times and cost also step up sharply beyond standard size grids.

Common mistakes

  • Specifying leaf size where clear opening was meant (and vice versa).
  • Forgetting that pairs and unequal pairs lose clear width to the meeting stile and astragal.
  • Ignoring hardware projection into the clear opening.
  • Sizing the structural opening before the frame system is selected.
  • Late equipment changes — a scanner swapped for a wider model after frames are set.

Practical checklist

  • Per opening: record required clear opening, governing item (bed/equipment), leaf size, thickness, computed weight, structural opening, tolerances and applicable rating size limits — on one schedule.
  • Verify worst-case tolerance stack-up still meets the clear opening requirement.
  • Cross-check leaf weight against hinge, closer, frame and anchor ratings before release to fabrication.

Sources